Search

Background: Organ donors are frequently trauma victims, but the impact of donor hemorrhagic shock and resuscitation (HSR) on pulmonary graft function has not been assessed. L-arginine treatment during reperfusion increases the production of endothelial nitric oxide and thus ameliorates ischemia-reperfusion injury. Objective of the present porcine study was to investigate the effect of donor hemorrhage on pulmonary graft function and potential beneficial effects of L-arginine administration., Methods: In the control-group (n=6), lungs were harvested from donors without hypotensive periods. In the HSR-group (n=6) and HSR-Arg-group (n=6), donors were subjected to hemorrhagic shock (40% blood shed) and resuscitation before harvest. Left lungs were transplanted after hypothermic preservation of 18 hr, and graft function was observed for 6 hr after reperfusion. Recipients in the HSR-Arg-group received a bolus of L-arginine (50 mg/kg BW) intravenously 5 min before reperfusion followed by a continuous intravenous administration of L-arginine 200 mg/kg BW for 2 hr. Tissue specimens and bronchoalveolar lavage fluid were obtained at the end of the observation period., Results: Donor lung function did not differ between study groups. Compared with the control group, pulmonary graft gas exchange was significantly impaired in the HSR-group. Graft function in the HSR-Arg-group did not differ from control organs. Neutrophil fraction, protein content, and malondialdehyde levels in the bronchoalveolar lavage fluid in the HSR-group were higher compared with control and HSR-Arg-Group., Conclusion: Although fulfilling ideal donor criteria, pulmonary graft function of lungs harvested from donors subjected to HSR is impaired, but improves significantly when l-arginine is administered during reperfusion.

Background: The routine transplantation of steatotic livers could potentially mitigate the donor shortage, but so far is associated with a high rate of graft dysfunction. Steatosis and brain death have been perceived as independent risk factors, but they may synergistically target the hepatic microcirculation. This study compares the effects of brain death on the microcirculation of steatotic and normal livers., Methods: Brain death was induced in obese and lean Zucker rats. Lean and obese sham-operated animals served as controls. Liver microcirculation was investigated using intravital fluorescence microscopy. Serum liver enzyme and reduced glutathione, expression of P-selectin, ICAM-1 and VCAM-1 mRNA in the liver were determined. The ultrastructural alterations were compared by electron microscopy., Results: In nonbrain-dead animals, liver steatosis was associated with smaller sinusoidal diameters, but did not impair sinusoidal perfusion. During brain death, sinusoidal diameter and perfusion were reduced in normal and, to a greater extent, in steatotic livers. Also, more leukocytes were recruited to the microvasculature of steatotic livers than to normal livers in brain-dead state. The highest liver enzyme activities and the lowest hepatic GSH concentrations were measured in brain-dead animals with steatotic livers; only in these organs was endothelial cell swelling regularly observed. In brain-dead state, only the P-selectin mRNA expression was increased in steatotic livers as compared to normal livers., Conclusions: Brain death amplifies the adverse effects of steatosis on the hepatic microcirculation. Our results underline the need for therapeutic intervention in brain-dead state when steatotic livers are to be used for transplantation.

Background: The warm ischemic period of lungs harvested from a non-heart-beating donor (NHBD) results in an increased ischemia-reperfusion injury after transplantation. The intravenous application of nitroglycerin (NTG), a nitric oxide (NO) donor, proved to be beneficial during reperfusion of lung grafts from heart-beating donors. The objective of the present study was to investigate the effect of nitroglycerin on ischemia-reperfusion injury after transplantation of long-term preserved NHBD-lungs., Methods: Sixteen pigs (body weight, 20-30 kg) underwent left lung transplantation. In the control group (n=5), lungs were flushed (Perfadex, 60 mL/kg) and harvested immediately after cardiac arrest. In the NHBD group (n=5) and the NHBD-NTG group (n=6), lungs were flushed 90 min (warm ischemia) after cardiac arrest. After a total ischemia time of 19 hr, lungs were reperfused and graft function was observed for 5 hr. Recipient animals in the NHBD-NTG group received 2 microg/kg/min of NTG administered intravenously during the observation period starting 5 min before reperfusion. Tissue specimens and bronchoalveolar lavage fluid (BALF) were obtained at the end of the observation period., Results: Compared with the control group, pulmonary gas exchange was significantly impaired in the NHBD group, whereas graft function in the NHBD-NTG group did not change. Leukocyte fraction and protein concentration in the BALF and histologic alteration of the NHBD-NTG group were not different from controls., Conclusions: Continuous infusion of NTG in the early reperfusion period improves pulmonary graft function of NHBD lungs after long-term preservation. The administration of an NO donor during reperfusion may favor the use of NHBD lungs to alleviate the critical organ shortage in lung transplantation.

Background: Scavenging of nitric oxide by hemoglobin-based oxygen carriers could aggravate microcirculatory failure in splanchnic organs after hemorrhagic shock as a consequence of vasoconstrictive side effects. The aim of this study was to compare the effects of two recombinant human hemoglobin solutions, a second-generation product bearing reduced nitric oxide-scavenging properties (rHb2.0) due to site directed mutagenesis of the heme pocket and a first-generation recombinant hemoglobin (rHb1.1) with scavenging capacity similar to native hemoglobin, on the pancreatic microcirculation after hemorrhagic shock., Methods: Twenty-eight pentobarbital-anesthetized rats were bled to a mean arterial pressure of 40 mmHg and maintained at this level for 1 h. Using an intravital microscope, the length of erythrocyte-perfused pancreatic capillaries per observation area (functional capillary density) were measured in animals resuscitated by volumes of hydroxyethyl starch, rHb1.1, or rHb2.0 equivalent to the shed blood volume. Animals without shock induction served as control., Results: As compared with control (438 +/- 10 cm(-1)), animals treated with hydroxyethyl starch (315 +/- 44 cm(-1)) and rHb1.1 (288 +/- 67 cm(-1)) showed a significant reduction of functional capillary density after 2 h of resuscitation. rHb2.0 was able to restore functional capillary density (410 +/- 42 cm(-1)) and mean arterial pressure to baseline values., Conclusion: rHb2.0 was effectively able to restore pancreatic microcirculation after hemorrhagic shock. This may be related to the compound's effective lack of nitric oxide-scavenging properties. This hemoglobin solution or ones similar to it might be uniquely valuable for resuscitation from hemorrhagic shock.

Objective: To evaluate the potential of postischemic intravenous infusion of the endogenous antioxidant glutathione (GSH) to protect the liver from reperfusion injury following prolonged warm ischemia., Background Data: The release of reactive oxygen species (ROS) by activated Kupffer cells (KC) and leukocytes causes reperfusion injury of the liver after warm ischemia. Therefore, safe and cost-effective antioxidant strategies would appear a promising approach to prevent hepatic reperfusion injury during liver resection, but need to be developed., Methods: Livers of male Lewis rats were subjected to 60, 90, or 120 minutes of normothermic ischemia. During a 120 minutes reperfusion period either GSH (50, 100 or 200 micromol/h/kg; n= 6-8) or saline (n= 8) was continuously administered via the jugular vein., Results: Postischemic GSH treatment significantly prevented necrotic injury to hepatocytes as indicated by a 50-60% reduction of serum ALT and AST. After 1 hour of ischemia and 2 hours of reperfusion apoptotic hepatocytes were rare (0.50 +/- 0.10%; mean +/- SD) and not different in GSH-treated animals (0.65 +/- 0.20%). GSH (200 micromol GSH/h/kg) improved survival following 2 hours of ischemia (6 of 9 versus 3 of 9 rats; P < 0.05). Intravital fluorescence microscopy revealed a nearly complete restoration of sinusoidal blood flow. This was paralleled by a reduction of leukocyte adherence to sinusoids and postsinusoidal venules. Intravenous GSH administration resulted in a 10- to 40-fold increase of plasma GSH levels, whereas intracellular GSH contents were unaffected. Plasma concentrations of oxidized glutathione (GSSG) increased up to 5-fold in GSH-treated animals suggesting counteraction of the vascular oxidant stress produced by activated KC., Conclusions: Intravenous GSH administration during reperfusion of ischemic livers prevents reperfusion injury in rats. Because GSH is well tolerable also in man, this novel approach could be introduced to human liver surgery.

Introduction: Capillary perfusion failure of the pancreatic microcirculation is characteristic in the pathogenesis of acute pancreatitis and ischemia-reperfusion damage after pancreas transplantation. Up to now, no logistic suitable method for analyzing pancreatic capillary perfusion during operations in humans has been established without the use of fluorescent dyes., Aim: To compare the well-established technique of intravital epifluorescence microscopy with the novel noninvasive method of orthogonal polarization spectral (OPS) imaging for measurement of the pancreatic functional capillary density., Methodology: In eight anesthetized rats, six identical capillary regions of interest per animal were measured by both methods, and the results were compared., Results: Absolute values from the capillary perfusion data were not significantly different between the two methods (fluorescence microscopy: 394 +/- 44 cm/cm2; OPS imaging: 385 +/- 45 cm/cm2). Correlation parameters were significant, and Bland-Altman analyses showed good agreement with a mean difference (bias) between the two methods of 6.9 cm/cm2, indicating that slightly smaller values are measured with OPS imaging., Conclusion: OPS imaging is a valid noninvasive method that analyzes the pancreatic microcirculation as accurately as the established intravital microscopy technique and therefore could be useful for clinical research and diagnosis during transplantation and operations.

Platelets are suggested to participate in the pathogenesis of hepatic ischemia-reperfusion (I/R) injury. This study was designed to analyze platelet-endothelial cell interactions in the postischemic mouse liver in vivo and to define the role of endothelial versus platelet P-selectin for these interactions. Platelet-endothelial cell interactions were quantitatively analyzed using intravital fluorescence microscopy after lobar hepatic I/R in C57BL/6 wild-type and P-selectin-deficient mice after infusion of ex vivo rhodamine-6G-labeled wild-type and P-selectin-deficient platelets. Reperfusion injury and apoptosis were assessed by established methods. In wild-type animals, hepatic I/R caused significantly enhanced platelet-endothelial cell interactions in terminal arterioles and postsinusoidal venules as well as platelet stagnation in sinusoids. Concomitantly, transaminase and caspase-3 activities were elevated and sinusoidal perfusion was impaired. In contrast, platelet-endothelial cell interactions were nearly absent in arterioles and venules of mice lacking endothelial P-selectin, irrespective of the presence of P-selectin on infused platelets, but still significantly elevated in sinusoids. Simultaneously, sinusoidal perfusion failure was ameliorated, and transaminase- and caspase-3 activities were significantly reduced in P-selectin-deficient mice as compared with wild-type animals. The present intravital microscopic study provides, for the first time, quantitative analyses of platelet-endothelial cell interactions in the postischemic hepatic microcirculation. Our in vivo data show that endothelial P-selectin is critical for postischemic platelet-endothelial cell interactions within hepatic presinusoidal arterioles and postsinusoidal venules. P-selectin deficiency prevents microvascular injury and apoptosis after warm hepatic I/R.

Background: Platelets are thought to be involved in the induction of hepatic ischemia-reperfusion (I/R) injury. The mechanisms of platelet adhesion in the hepatic microvasculature and the role of platelets in the pathogenesis of I/R-induced liver damage in vivo remain unclear., Methods: In C57BL/6 mice, platelet- and leukocyte-endothelial cell interactions were quantitatively analyzed using intravital fluorescence microscopy in sham-operated animals, after warm lobar hepatic I/R (90/20 min) in wild-type and intercellular adhesion molecule (ICAM)-1-deficient mice, and after I/R in wild-type mice treated with an antifibrinogen antibody. Fibrinogen deposition on the endothelium was detected by intravital microscopy and by immunostaining. Reperfusion injury was assessed by measurement of liver enzyme and caspase-3 activities and of lipid peroxidation., Results: Hepatic I/R induced fibrinogen deposition on hepatic endothelium, followed by a dramatic increase in the number of firmly adherent platelets in the liver microvasculature. Simultaneously, the number of adherent leukocytes in postsinusoidal venules and the aspartate aminotransferase/alanine aminotransferase and caspase-3 activities were elevated. Although ICAM-1 deficiency attenuated postischemic adherence of both platelets and leukocytes, the application of an antifibrinogen antibody selectively reduced the number of adherent platelets but did not influence leukocyte adhesion. The selective blockade of platelet adherence significantly prevented the postischemic increase in liver enzyme and caspase-3 activities. Furthermore, sinusoidal perfusion failure and lipid peroxidation were attenuated in the treated group., Conclusions: These in vivo data show that platelet adhesion mediated through fibrinogen deposition on ICAM-1 expressed on the endothelium of postischemic hepatic microvessels induces microvascular injury and hepatocellular apoptosis after I/R of the liver during early reperfusion.

Introduction: Microcirculatory disturbances caused by ischemia-reperfusion injury (IRI) are the crucial hallmarks of pancreatitis following pancreas transplantation., Aims: To develop a novel rodent model of normothermic in situ ischemia of a pancreatic tail-segment that simulates the clinical situation of pancreas transplantation by flushing the organ via an inserted microcatheter and thus enables selective treatment of the organ via this access., Methodology: Four experimental groups were investigated (n = 7 Wistar rats/group): sham animals without ischemia and dissection of the pancreas; control animals with dissection of a pancreatic tail segment pedunculated on the splenic vessels and flushing od this segment with saline via a microcatheter; and two groups of animals treated like controls with a pancreatic ischemia time of 1 hour or 2 hours. With use of intravital epifluorescence microscopy, the microcirculatory damage was characterized by investigation of functional capillary density (FCD) and leukocyte adherence in postcapillary venules (LAV) before ischemia and during a reperfusion time of 2 hours. Dry:wet ratio determinations, light microscopy, and electron microscopic investigations were performed to characterize the histologic organ damage., Results: FCD decreased significantly (p < 0.05) 2 hours after reperfusion in the groups of 1-hour (-29.21%) and 2-hour ischemia (-42.73%), in comparison with baseline values. LAV increased significantly (p < 0.05), 4.3- and 5.8-fold, after 1-hour and 2-hour ischemia during the observation time. The histologic damage was similar to posttransplantation pancreatitis in humans 1 hour after reperfusion. In sham and control animals these alterations were not significant., Conclusions: The rodent in situ model of pancreatic IRI showed standardized microcirculatory damage dependent on the ischemia time. Offering the possibility of selective treatment by the direct artery access to the ischemic pancreatic area, the model enables investigations of questions related to human pancreas transplantation.

Several studies have shown that warm ischemia before short-term preservation of pulmonary grafts from non-heart-beating donors (NHBD) induced morphological changes, but still provided a good pulmonary graft function. The aim of this study was to investigate morphological and metabolic changes of NHBD lungs after long-term preservation. Left lung allotransplantation was performed on 12 native-bred pigs. In the NHBD group, lungs were subjected to 90 min of warm ischemia before harvesting, whereas lungs in the HBD group were harvested immediately after cardiac arrest. After a total ischemic period of 19 h, lungs were reperfused and pulmonary gas exchange was assessed. Bronchoalveolar lavage (BAL) and tissue specimen for wet-to-dry weight (W/D) ratio, histologic examination, and measurement of high-energy phosphates were taken 5 h after reperfusion. All parameters were compared with a sham-operated control group. Five hours after reperfusion, mean paO2 and paCO2 were 288 +/- 52 and 48 +/- 0.8 mmHg, respectively, during isolated ventilation of the pulmonary graft with 100% oxygen in the NHBD group. W/D ratio and high-energy phosphates of the pulmonary graft did not differ between our study groups. Histologic examination showed significant morphological changes in the HBD and NHBD group, but alterations were more pronounced in the NHBD group. The percentage of neutrophils, total protein content, and potassium concentration were significantly elevated in the BAL fluid of the NHBD group. Despite the observed aggravation of cellular injury after long-term preservation, NHBD lungs still performed a good pulmonary graft function.

Background: Microcirculatory failure, activation of Kupffer cells (KC), and the formation of reactive oxygen species (ROS) are considered pivotal mechanisms of reperfusion injury after orthotopic liver transplantation. However, the sequence of these events and their impact on early graft function remain controversial. We therefore investigated whether KC induce microcirculatory disturbances through ROS release and whether microcirculatory failure contributes to early graft function after liver transplantation., Methods: Donor livers of Lewis rats were pretreated either with saline or with gadolinium chloride (GdCl3), an inhibitor of KC function (n=8 each). Syngeneic OLT was performed after 24 hr of hypothermic preservation in University of Wisconsin solution., Results: Intravital microscopy revealed significantly higher sinusoidal perfusion rates in GdCl3-treated allografts (92+/-1.1% vs. 75.7+/-0.8%; P<0.001) compared with untreated controls; permanent leukocyte sticking in sinusoids (23.5+/-2.1 vs. 62.6+/-3.3 cells/lobule, P<0.001) and in postsinusoidal venules (153.1+/-10.4 vs. 446.6+/-46.4 cells/mm(2), P<0.001) were markedly attenuated in GdCl3-treated allografts. Improvement of microcirculatory parameters in GdCl3-treated livers was correlated with a significant reduction of plasma glutathione disulfide formation by KC-derived ROS (0.96+/-0.1 microM vs. 1.79+/-0.5 microM; P<0.01). Despite these beneficial effects, GdCl3-pretreatment failed to improve postischemic alanine aminotransferase release and bile flow., Conclusions: Microcirculatory failure after liver transplantation is related to KC-derived oxidant stress but not involved in early graft dysfunction.

Background: Although hepatic ischemia-reperfusion (I/R) injury can be reduced by cooling of the ischemic organ, a systematic in vivo analysis of the influence of organ temperature in I/R injury is missing. The aim of this study was to systematically investigate the impact of defined temperatures of the ischemic liver tissue on microvascular I/R injury., Methods: Ischemia of the left liver lobe was induced in C57BL/6 mice for 90 min. The ischemic lobe was placed in a polyethylene well and the temperature was adjusted to 37 degrees C, 26 degrees C, 15 degrees C, and 4 degrees C by superfusion with cooled/warmed saline solution. The ischemia groups (n=7 each) were compared with a sham-operated group (n=7). The sinusoidal perfusion index and the number of leukocytes firmly adherent to the endothelium of postsinusoidal venules were assessed using intravital fluorescence microscopy at 30 min, 120 min, and 240 min of reperfusion, respectively. At the end of the experiment, serum activities of the liver enzymes aspartate aminotransferase/alanine aminotransferase were determined, and tissue specimens were examined by electron microscopy., Results: Core body temperature did not differ significantly between the groups. In the 37 degrees C group, the sinusoidal perfusion index was significantly reduced and the number of adherent leukocytes was significantly increased compared with the sham group. In all hypothermia groups, however, the microcirculatory parameters did not differ from the sham group. Serum activities of aspartate aminotransferase/alanine aminotransferase were significantly increased and hepatocellular integrity was severely affected in the 37 degrees C group as compared with all other groups., Conclusions: These findings demonstrate that in the mouse liver the known protective effect of hypothermia is already encountered at 26 degrees C. Further reduction of temperature did not generate additional protection from I/R injury.

Background: The aim of this study was to investigate changes in the blood microcirculation of skin, subcutaneous tissue, and striated muscle, and the venous and lymphatic outflow from hind limb, after a standardized mechanical trauma., Methods: Trauma, defined as 50% of the minimal energy needed for tibia fracture (3.7 J/g), was applied to the leg of hairless mice. Intravenously injected fluorescein isothiocyanate-dextran 150 kDa and Rhodamine-6G were used for intra-vital fluorescence microscopy of blood vessels. Lymphatics were stained with fluorescein isothiocyanate-dextran injected into the footpad. A computer-assisted analysis system allowed measurement of the functional capillary density (FCD), vessel diameters, velocity of blood flow, and edema value expressed as extravasation index (EV). The percentage of slowly rolling and sticking leukocytes in postcapillary venules was estimated., Results: At the site of injury, trauma resulted in significant reduction of FCD in skin, subcutaneous tissue, and striated muscle. There were no significant differences in the vessel diameter (skin subcutaneous and muscle arterioles and venules, and superficial saphenous artery and vein) or velocity of blood flow (subcutaneous tissue and muscle venules). The EV increased significantly in muscle venules and was higher in muscles, subcutaneous tissue, and superficial saphenous veins than in controls (nonsignificantly). An increased percentage of slowly rolling and sticking leukocytes was noted in the superficial saphenous vein at the site of injury and proximal to it. The lymphatics remained patent, with faster visualization and increased summarized cross-sectional areas in traumatized extremities., Conclusion: Early changes occurring in soft tissues in response to mechanical injury were characterized by reduction in FCD of skin and muscles, and less in subcutis; increased EV, reflecting leakage of macromolecules; increased percentage of slowly rolling and sticking leukocytes; maintenance of lymphatic vessel continuity; and increased lymph formation and flow rate.

Background: Quantitative analysis of liver microcirculation using intravital fluorescence microscopy in animals has increased our knowledge about ischemia-reperfusion injury. However, because of the size of the instrumentation and the necessity of fluochromes for contrast enhancement, human liver microcirculation cannot be observed. Orthogonal Polarization Spectral (OPS) imaging is a recently introduced technique that can be used to visualize the microcirculation without the need for fluorescent dyes. It is a small, hand-held device and could potentially be used to study the microcirculation of the human liver in a clinical setting. However, before implementation into clinical use its ability to quantitatively measure microcirculatory parameters must be validated., Methods: The livers of Spraque-Dawley rats (n=9) were exteriorized, and images were obtained using OPS imaging and intravital fluorescence microscopy of the identical microvascular regions before and after the induction of a 20-min warm lobar ischemia. Images were videotaped for later computer-assisted off-line analysis., Results: OPS imaging can be used to accurately quantify the sinusoidal perfusion rate, vessel diameter, and venular red blood cell velocity. Correlation parameters were significant and Bland-Altman analyses showed good agreement for data obtained from the two methods at baseline as well as during reperfusion., Conclusion: OPS imaging can be used to quantitatively measure microcirculatory parameters in the rat liver under both physiological and pathophysiological conditions. Thus, OPS imaging has the potential to be used to make quantitative measurements of the microcirculation in the human liver.

Background: Normovolemic hemodilution is an effective strategy to limit perioperative homologous blood transfusions. The reduction of hematocrit related to hemodilution results in reduced arterial oxygen content, which initially is compensated for by an increase in cardiac output and oxygen extraction ratio. To increase the efficacy of hemodilution, a low hematocrit should be aimed for; however, this implies the risk of myocardial ischemia and tissue hypoxia., Objective: To assess whether hemodilution can be extended to lower hematocrit values by the use of a hemoglobin-based artificial oxygen carrier solution., Design: Prospective, randomized, controlled., Setting: Animal laboratory of a university hospital., Subjects: Twelve anesthetized, mechanically ventilated pigs., Interventions: Isovolemic hemodilution was performed with either 10% diaspirin crosslinked hemoglobin (DCLHb Baxter Healthcare, Boulder, CO; n = 6) or 8% human albumin solution (HSA, oncotically matched to DCLHb, Baxter Healthcare; n = 6) to a hematocrit of 15%, 8%, 4%, 2%, and 1%., Measurements and Main Results: In both groups, measurements were performed at baseline at the previously mentioned preset hematocrit values and at the onset of myocardial ischemia characterized by critical hematocrit (significant ST-segment depression >0.1 mV and/or arrhythmia). To determine peripheral tissue oxygenation and myocardial perfusion and function, the following variables were evaluated: total body oxygen transport variables, tissue oxygen partial pressure (tPo2, MDO-Electrode, Eschweiler Kiel, Germany) on the surface of the skeletal muscle, coronary perfusion pressure, left ventricular (LV) end-diastolic pressure, global and regional myocardial contractility (maximal change in pressure over time, LV segmental shortening, microsonometry method), LV myocardial blood flow (fluorescent microsphere technique), LV oxygen delivery, and the ratio between LV subendocardial and subepicardial myocardial perfusion. In the HSA group, critical hematocrit was found at 6.1 (1.8)% (hemoglobin, 2 g x dL(-1)), whereas all DCLHb-treated animals survived hemodilution until hematocrit 1.2 (0.2)% (hemoglobin, 4.7 g x dL(-1)) was achieved without signs of hemodynamic instability. Although arterial oxygen content was higher in the DCLHb group at 1.2% hematocrit than in the HSA group at critical hematocrit (i.e., hematocrit, 6.1%; hemoglobin, 2 g.dL-1) neither oxygen delivery and oxygen uptake nor median tPo2 and hypoxic tPo2 values on the skeletal muscle were different between groups. In contrast, subendocardial ischemia was absent in DCLHb-diluted animals until 1.2% hematocrit was achieved. This was attributable to a higher coronary perfusion pressure (65 (22) mm Hg vs. 19 (8) mm Hg; p <.05), higher subendocardial perfusion (4.1 (2.6) mL.min-1.g-1 vs. 1.2 (0.4) mL x min(-1) x g(-1)), and subendocardial oxygen delivery (5.7 (2) mL x min(-1) x g(-1), p <.05) in DCLHb-diluted animals, resulting in superior myocardial contractility reflected by maximal change in pressure over time (3829 (1914) vs. 1678 (730); p <.05) and higher regional myocardial contractility (11 (8)% vs. 6 (2)%; p <.05). An increased LV end-diastolic pressure reflected LV myocardial pump failure in HSA-diluted animals but was unchanged in DCLHb-diluted animals. In the DCLHb group, systemic vascular resistance index remained at baseline values throughout the protocol, whereas coronary vascular resistance decreased. In contrast, both variables decreased in HSA-diluted animals., Conclusion: DCLHb as a diluent allowed for hemodilution beyond the hematocrit value, determined "critical" after hemodilution with HSA (6.1% (1.8)%). Even at 1.2% hematocrit (hemoglobin, 4.7 g x dL(-1)) myocardial perfusion and function were maintained, although at the expense of peripheral tissue oxygenation. This discrepancy in regional oxygenation might be caused by a redistribution of blood flow favoring the heart, which is related to a disproportionate decrease of coronary vascular resistance index during hemodilution with DCLHb.

Background: A newly developed observation chamber has been designed for comfortable limb immobilization during intravital microscopic analysis, which permits direct, repeated, long-lasting observations of the microcirculation in the various hindleg soft tissues., Methods: Experiments were performed under inhalation isoflurane/nitrous oxide anesthesia. Intravenously injected fluorescein isothiocyanate (FITC)-dextran (M, 150,000) and Rhodamine 6G (Sigma, St. Louis, MO) allowed for visualization of both microcirculatory phenomena in arterioles, capillaries, and venules and macrocirculatory structures as superficial saphenous artery and vein. Skin microcirculation analysis was performed from the epidermal side (group A, n = 7), whereas observation of deeper situated tissues was performed after oval skin excision on the medial surface of the tibial area (group B, n = 7). FITC-dextran (M, 150,000; group C, n = 8) injected into the foot pad permitted visualization of venous, arterial, and accompanying lymphatic vessels. With the aid of a computer-assisted microcirculation analysis system, functional capillary density, vessel diameter, edema formation, and leukocyte-endothelial cell interactions were evaluated. The ratio of rolling leukocytes, given as percentage of all leukocytes passing the vessel segment during a 30-second observation interval, and the number of sticking leukocytes per square millimeter of endothelial surface were determined., Results: This new model allows the analysis of the complex in vivo changes of macro- and microcirculatory parameters in the different (venous, arterial, lymphatic) vessels of the covering tissues (skin and muscle) of the mouse hindleg., Conclusion: The potential applications of this technique include the study of mechanical trauma, ischemia-reperfusion injury, and tissue compression mimicking both acute and prolonged venous stasis on both the microcirculatory and macrocirculatory levels in the different tissue compartments.

Background: Experimental studies demonstrated a suppression of oxygen-derived free radicals, reduced adhesion of activated neutrophils on the endothelium and an increase of de novo synthesis of surfactant during liquid ventilation with perflurocarbon. The purpose of this study was to assess the pulmonary graft function after preservation with endobronchially administered perfluorocarbon as an alternative to flush perfusion., Methods: Native bred pigs underwent orthotopic left lung transplantation. Donor lungs were flushed in situ with either a low-potassium dextran solution (LPD, n=6) or a perfluorochemical was administered endobronchially (PFC, n=6) and were then stored after removal for 18 hr at 4 degrees C. Pulmonary graft function was assessed after reperfusion for 5 hr by measuring pulmonary gas exchange and hemodynamics during isolated ventilation and perfusion. Tissue specimens were taken for analysis of morphology and wet/dry ratio. All values were compared to a sham-operated group (n=6)., Results: Pulmonary gas exchange of the graft revealed reduced paO2 values and elevated paCO2 values in the PFC group throughout the observation period as compared with the LPD group and sham group. Endothelial alterations and fibrin exudate in the PFC group were significantly more pronounced. Lungs in the LPD group showed functional and morphological recovery close to sham group., Conclusions: Long-term preservation with endobronchially administered perfuorocarbon is possible. Impaired pulmonary graft function and pronounced morphological alterations indicate an aggravation of the ischemic reperfusion injury after lung transplantation compared to LPD preserved lungs.

Background: Perfluorocarbon-based oxygen carriers have been proposed as an adjunct to autologous blood conservation techniques during elective surgery. To date, the effects of perfluorocarbon emulsions at the microcirculatory level have not been studied extensively. In this study the effects of perflubron emulsion on the microcirculation after acute normovolemic hemodilution (ANH) were investigated using different colloid plasma expanders., Methods: The dorsal skin fold chamber model and intravital fluorescence microscopy were used for analysis of the microcirculation in the thin striated skin muscle of conscious hamsters (body weight, 40-60 g). Measurements of microvascular perfusion and leukocyte adhesion (n = 6 animals per experimental group) were made before and at 10, 30, and 60 min after ANH (to hematocrit 0.3) with either 6% hydroxyethyl starch 200/0.6 (HES), 3.5% gelatin, 5% human serum albumin (HSA), or 6% dextran 60 (DX-60) followed by intravenous injection of 3 ml/kg body weight of a 60% weight/volume perfluorocarbon emulsion based on perflubron (perfluorooctyl bromide) emulsified with egg yolk lecithin., Results: Acute normovolemic hemodilution with HES, gelatin, or HSA followed by injection of perflubron emulsion elicited no alterations of local microvascular perfusion or leukocyte-endothelium interaction as assessed in arterioles and postcapillary venules. However, ANH with DX-60 followed by injection of perflubron emulsion led to a significant reduction of erythrocyte velocity in postcapillary venules and an increase in venular leukocyte sticking that was never observed with DX-60 alone., Conclusions: Hydroxyethyl starch, gelatin, and HSA are compatible with perflubron emulsion in the setting of ANH. Only DX-60 appeared to be incompatible with perflubron emulsion, as evidenced by impairment of capillary perfusion.

Objective: To evaluate the effects of resuscitation with a 10% diaspirin-crosslinked hemoglobin (DCLHb) solution on global hemodynamic variables, systemic and myocardial oxygen transport and tissue oxygenation, and contractile function of the left ventricle in an experimental model of severe hemorrhagic shock and critical stenosis of the left anterior descending coronary artery (LAD)., Design: Prospective, placebo-controlled, randomized study., Setting: Experimental animal laboratory., Subjects: A total of 20 anesthetized pigs., Interventions: After implementation of a permanent critical LAD stenosis (ie, maintenance of basal blood flow but absence of reactive hyperemia after a 10-sec complete vessel occlusion), hemorrhagic shock (target mean aortic pressure, 45 mm Hg) was induced within 15 mins by programmed withdrawal of blood and maintained for 60 mins. Subsequently, the volume of plasma lost during hemorrhage was replaced by either a balanced electrolyte solution containing 10 g/dL DCLHb (DCLHb group; n = 10) or an 8 g/dL human albumin solution (HSA) oncotically matched to DCLHb (HSA group; n = 10). Data were collected immediately after the infusion of the different solutions and again after 60 mins had elapsed., Measurements and Main Results: Although five of ten HSA-treated animals died of acute left ventricular failure within the first 20 mins after complete fluid resuscitation, all of the DCLHb-treated animals survived the 60-min observation period after resuscitation (p < .05). This significant difference in mortality is explained by higher coronary perfusion pressure in DCLHb-treated animals (75 +/- 17 vs. 27 +/- 17 torr DCLHb vs. HSA group; p < .05) and persistence of subendocardial ischemia and hypoxia (radioactive microspheres method) in HSA-treated animals on resuscitation particularly affecting the LAD-supported myocardium (subendocardial oxygen delivery: 20 +/- 11 vs. 3 +/- 1 mL oxygen x g(-1) x min(-1), DCLHb vs. HSA group; p < .05). Except for enhanced myocardial contractility immediately on infusion of DCLHb (maximal left ventricular pressure increase: 2373 +/- 782 vs. 1730 +/- 543 torr x sec(-1) DCLHb vs. HSA group; p < .05), no differences were detected between groups concerning the variables of systemic oxygen transport, tissue oxygenation, and regional contractile function of the myocardium (determined with microsonometry)., Conclusions: Fluid resuscitation with 10% DCLHb solution completely reverses hemorrhagic shock-induced subendocardial ischemia and hypoxia in the presence of compromised coronary circulation and thereby prevents early death after resuscitation.

Background: Microvascular reperfusion failure of splanchnic organs is a crucial hallmark in organ damage induced by hemorrhagic shock, which should be prevented by a resuscitation solution. Because the vasoactive properties of the hemoglobin-based oxygen carrier diaspirin cross-linked hemoglobin (DCLHb) could adversely influence restoration of pancreatic capillary perfusion during resuscitation, the authors investigated its effects on the microcirculation of the rat pancreas in comparison with whole blood and 6% hydroxyethylstarch resuscitation from severe hemorrhagic shock., Methods: Twenty-eight pentobarbital-anaesthetized rats were bled to a mean arterial pressure (MAP) of 40 mmHg and maintained at this level for 1 h. Using an intravital microscope, mean arterial pressure, the length of erythrocyte-perfused pancreatic capillaries per observation area (functional capillary density), the adherence of leukocytes in postcapillary venules, and pancreatic lipid peroxidation, measured as thiobarbituric acid-reactive material in pancreatic tissue, were determined in animals resuscitated by volumes of hydroxyethylstarch, DCLHb, and whole blood (WB) equivalent to the shed blood volume or in control animals without shock induction for a period of 2 h after resuscitation., Results: Compared with control animals (366+/-28 cm(-1)), animals resuscitated with DCLHb (294+/-45 cm(-1)), WB (306+/-11 cm(-1)), and hydroxyethylstarch (241+/-34 cm(-1)) showed a significant reduction of functional capillary density after 2 h of resuscitation. DCLHb was as effective as WB and superior to hydroxyethylstarch in restoring functional capillary density and mean arterial pressure. Leukocyte adherence in postcapillary venules was not enhanced by DCLHb (369+/-148/mm2) infusion when compared with hydroxyethylstarch- (615+/-283/mm2) and WB-treated (510+/-415/mm2) animals. Lipid peroxidation of pancreatic tissue was significantly elevated after treatment with both oxygen-carrying solutions compared with hydroxyethylstarch., Conclusion: DCLHb is as effective as WB for preservation of the pancreatic microcirculation.

Transient sublethal hyperthermia and the recovery from this exposure to heat (heat shock preconditioning) provides a cytoprotective effect on oxidative insults through an intracellular protective response, heat shock response. The impact of heat shock preconditioning on hepatic microvascular failure, which is a causative determinant of ischemia/reperfusion-induced injury of the liver, was investigated by using intravital fluorescence microscopy. In Sprague-Dawley rats, normothermic ischemia was induced by totally clamping the hepatoduodenal ligament for 20 min, followed by 120 min of reperfusion. Heat shock preconditioning was performed by whole-body hyperthermia (42 degrees C for 15 min) and subsequent 48 h recovery. In accordance with the prominent induction of heat shock protein 70 in the liver tissue, the postischemic decrease in sinusoidal perfusion rate and sinusoidal diameter, and the postischemic increase in the number of stagnant leukocytes in sinusoids and adherent leukocytes in postsinusoidal venules were significantly attenuated in the heat shock-treated animals. Furthermore, liver enzyme release (glutamate pyruvate transaminase and alpha-glutathione S-transferase) was significantly reduced and postischemic deterioration of bile production was attenuated. The 7-day survival rate after 20-minute ischemia was significantly improved from 50% to 80% (heat shock-nontreated group vs. heat shock-treated group, P < 0.05). These results indicate that heat shock preconditioning attenuates ischemia/reperfusion-induced hepatic injury by preventing postischemic microvascular disturbances, and that its protective effect is circumstantially associated with the concomitant induction of heat shock protein 70.

Background: Fluorocarbon emulsions have been proposed as temporary artificial oxygen carriers. The aim of the present study is to compare the effectiveness of perflubron emulsion with the effectiveness of autologous blood or colloid infusion for reversal of physiologic transfusion triggers., Methods: A multinational, multicenter, randomized, controlled, single-blind, parallel group study was performed in 147 orthopedic patients. Patients underwent acute normovolemic hemodilution with colloid to a target hemoglobin of 9 g/dl with an inspiratory oxygen fraction (FIO2) of 0.40. Patients were then randomized into one of four treatment groups after having reached any of the protocol-defined transfusion triggers including tachycardia (heart rate > 125% of posthemodilution rate or > 110 bpm), hypotension (mean arterial pressure < 75% of posthemodilution level or < or = 60 mmHg), elevated cardiac output (> 150% of posthemodilution level) or decreased mixed venous oxygen partial pressure (PVO2; < 38 mmHg). Treatments in the four groups were 450 ml autologous blood harvested during acute normovolemic hemodilution given at FO2 = 0.40; 450 ml colloid at FIO2 = 1.0; 0.9 g/kg perflubron emulsion with colloid (total = 450 ml) at FIO2 = 1.0; and 1.8 g/kg perflubron emulsion with colloid (total = 450 ml) at FIO2 = 1.0. The primary endpoint was duration of transfusion-trigger reversal. A secondary end-point was percentage of transfusion-trigger reversal., Results: Perflubron emulsion was well tolerated with no serious adverse event attributed to drug treatment. Duration of reversal was longest in the 1.8 g/kg perflubron group (median, 80 min; 95% confidence interval, 60-100 min; P = 0.014 vs. autologous blood, P < 0.001 vs. colloid) followed by the 0.9 g/kg perflubron group (median, 59 min; 95% confidence interval, 40-90 min), the autologous blood group (median, 55 min; 95% confidence interval, 30-70 min) and the colloid group (median, 30 min; 95% confidence interval, 27-60 min). Percentage of reversal was also highest in the 1.8 g/kg perflubron group (97%; P < 0.001 vs. autologous blood; P = 0.014 vs. colloid), followed by 0.9 g/kg perflubron (82%), colloid (76%), and autologous blood (60%)., Conclusions: Perflubron emulsion (1.8 g/kg) combined with 100% oxygen ventilation is more effective than autologous blood or colloid infusion in reversing physiologic transfusion triggers.

To study the role of tumor necrosis factor-alpha (TNF-alpha) for induction of the proinflammatory cytokine cascade after liver ischemia and reperfusion (I/R), rats were injected intraperitoneally with anti-TNF-alpha monoclonal antibodies (mAb) or placebo (IgG1) 30 min prior to global hepatic ischemia. Blood levels of TNF-alpha, interleukin (IL)-1alpha and -6 were determined. In addition, Kupffer cells (KC) were harvested after 60 min of reperfusion and spontaneous cytokine release was measured. Sham-operated animals were used as controls. Levels of proinflammatory cytokines in serum and KC supernatants were detected using specific bioassays and ELISA. Liver I/R resulted in increased (p < .01) serum levels of TNF-alpha, IL-1alpha, and IL-6, which was associated with an enhanced (p < .05) release of these cytokines by KC. In vivo pretreatment with anti-TNF-alpha mAb led to complete neutralization of TNF-alpha serum levels and decreased (p < .01) IL-6 levels (-62%). Moreover, anti-TNF-alpha mAb markedly (p < .05) decreased the release of TNF-alpha (-69%) and IL-6 (-56%) by KC, while IL-1alpha was not affected. These data indicate that TNF-alpha produced early after liver I/R triggers both its own secretion as well as IL-6 release by KC during reperfusion while the release of IL-1alpha occurs independent from TNF-alpha.

Background: Hemorrhagic shock and resuscitation triggers a global ischemia/reperfusion phenomenon, in which activated leukocytes are considered strong contributors to the ensuing tissue damage., Methods: The aim of the study was to investigate the effects of hypertonic saline dextran (HSD) on the early leukocyte/endothelial interactions (intravital fluorescence microscopy) in a rat model of hemorrhagic shock (1 hour at mean arterial pressure of 40 mm Hg). The resuscitation was performed with lactated Ringer's solution (RL, four times shed blood/20 minutes, n = 6), 6% dextran 60 (DEX, 100% shed blood/5 minutes, n = 8), and 7.2% NaCl/10% dextran 60 (HSD, 10% shed blood/2 minutes, n = 8)., Results: After 1 hour of resuscitation, shock-induced stasis/adherence of leukocytes was further enhanced with RL (sinusoids 17.6+/-6.9%; venules 33.9+/-8.5%), whereas DEX and HSD attenuated leukocyte stagnation in sinusoids (DEX -7.4+/-6,1%; HSD -14.7+/-2.9%, p<0.01 vs. RL) and leukocyte adherence in postsinusoidal venules (DEX -12.2+/-8.6%, p<0.05 vs. RL; HSD -27+/-7.4%, p<0.01 vs. RL)., Conclusion: HSD reduced significantly the number of leukocytes accumulated in the liver after resuscitation of hemorrhagic shock, probably due to a combination of mechanisms of both components.

The purpose of the study was to examine the effects of buflomedil hydrochloride (BFL) on the expression of adhesion molecules (beta2-integrins) and oxygen radical production of circulating and emigrated intra-abdominal polymorphonuclear leukocytes (PMNL) in a standardized porcine model of hyperdynamic endotoxemia. A total of 20 anesthetized pigs were randomly assigned to one of the following groups: endotoxin group (endotoxin 5 microg / kg x h, intravenously (i.v.), n = 7), BFL group (BFL (3 mg/kg initial i.v. bolus followed by a continuous infusion (.1 mg / kg x h) and endotoxin 5 microg / kg x h, i.v., n = 7), and control group (NaCl .9%; n = 6). Experiments were terminated at 330 min. Infusion of endotoxin alone resulted in the activation of circulating and emigrated PMNL as evidenced by neutropenia, functional and numerical up-regulation of beta2-integrins, and enhanced oxygen radical production. BFL was able to attenuate functional and numerical up-regulation of beta2-integrins as well as oxygen radical production of circulating and emigrated PMNL. An unexpected decrease in the plasma concentration of BFL during the experiments was associated with an increase in the oxygen radical production of PMNL at the end of the experiments. In addition, BFL attenuated the fall in the intramucosal pH and the increase in plasma concentration of lactate observed in the late phase of endotoxemia. These findings suggest that BFL is able to decrease systemic activation of PMNL and to improve local tissue oxygenation during endotoxemia.

The influence of the vasoactive drug buflomedil hydrochloride bound to liposomes (2 mg/ml) was investigated in an arterial pattern skin flap model using the ear of hairless mice. For flap creation, the ear is cut at four-fifths of its base, which leaves the anterior artery as the only feeding vessel of the flap. Liposomes were locally applied daily for 30 minutes up to 5 days after flap creation. Microvascular perfusion in the proximal, central, and distal parts of the flap was measured by laser Doppler flowmetry. The border between perfused and nonperfused tissue was visualized by intravital fluorescence microscopy using fluorescein isothiocyanate (FITC)-labeled dextran (Mr 150,000) for contrast enhancement of microvessels. The area of nonperfused tissue was assessed by digital planimetry. Five days after flap creation the nonperfused area amounted to 23.8 +/- 3.1 percent of total flap surface in treated ears compared with 46.1 +/- 5.6 percent in untreated ears (p < 0.05) of the contralateral side. Additional preoperative treatment for 5 days did not further reduce the area of nonperfused tissue (treated ears, 23.0 +/- 1.3 percent; control ears, 44.6 +/- 5.1 percent). Microvascular perfusion was higher in the postoperatively treated ears in all parts of the flap from day 1 after flap creation until termination of the experiment. Five days after flap creation, perfusion as measured by laser Doppler flowmetry was reduced to 46.0 +/- 10.8 percent in the distal part in control ears compared with 91.9 +/- 8.3 percent (p < 0.05) in treated animals. Additional preoperative treatment for 5 days did not result in further improvement. It is concluded that local application of the vasoactive drug buflomedil docked to liposomes could be of therapeutic use in the treatment of ischemic tissue, including skin flaps.

The effect of zymosan-induced generalized inflammation on the microcirculation of distant striated skin muscle was studied for a 12 day period in awake Syrian golden hamsters (n = 18) using the dorsal skinfold chamber model and intravital fluorescence microscopy. Intraperitoneal zymosan exposure (125 mg/100 g body weight) induced significant nutritive perfusion failure in the distant striated muscle tissue at Day 1 without complete recovery over the 12 day observation period, as indicated by the marked reduction of functional capillary density when compared with both baseline values and values of sham-treated control animals. Moreover, intraperitoneal zymosan exposure induced endothelial disintegration, as demonstrated by the continuous increase of macromolecular leakage throughout the 12 days of observation. Strikingly, zymosan did not induce significant leukocyte adherence to the endothelial lining of postcapillary and collecting venules of the striated muscle tissue. Thus, we conclude that in this model of generalized inflammation nutritive perfusion failure and loss of endothelial integrity in distant striated muscle is not mediated by activated leukocytes, but must rather be attributed to direct toxic effects of mediators, elicited by the local (intraperitoneal) zymosan challenge and systemically released.

The aim of this study was to evaluate the effect of dextran (Dx) 1 versus Dx 60 (molecular weights 1,000 and 60,000) on microvascular disturbances and tissue injury in striated muscle after ischemia/reperfusion (I/R). Experiments were performed using a 4 h pressure-induced ischemia model in the hamster dorsal skinfold chamber. Three groups (n=6) of animals received a continuous infusion (45 min, 3 microL/min) of either Dx 1 or Dx 60 (total dose 5 mg/kg) or saline solution beginning 15 min before reperfusion. Intravital fluorescence microscopy allowed for quantification of functional capillary density, leukocyte adherence, extravasation of fluorescein isothiocyanate-Dx, and nonviable (propidium-positive) cell count before ischemia and .5, 2, and 24 h after reperfusion. Experiments were terminated with tissue preservation for electron microscopy. Postischemic functional capillary density was significantly improved by Dx 60 (at 24 h, 88% vs. 51% in controls). In animals receiving postischemic Dx 1 or Dx 60, leukocyte adherence was significantly reduced (at .5 h, 44% and 58%, respectively) as compared with controls, whereas macromolecular extravasation was unchanged. Nonviable cell count was significantly decreased by both Dx fractions (at 24 h, Dx 1, 75%; Dx 60, 87%), indicating a reduction of tissue injury, which was also confirmed by electron microscopy. These results provide evidence that Dx 60 at 5 mg/kg attenuates I/R injury more effectively than Dx 1. Leukocytes play a major role in the development of I/R injury, but macromolecular extravasation does not always correlate with the leukocyte-endothelium interaction and the manifestation of I/R injury.

The role of endothelin (ET)-1 as a mediator of small intestinal mucosal perfusion failure and tissue damage was investigated in the rat using intravital fluorescence videomicroscopy. The effects of intravenous infusion of ET-1 (3 nmol/kg) on functional capillary density, mucosal thickness, and the degree of mucosal damage were evaluated. Administration of ET-1 caused pronounced mucosal injury with a significant reduction of mucosal thickness compared with vehicle-treated control animals. Concomitantly, villous functional capillary density was markedly reduced 30 and 90 min after the infusion of ET-1. ET(A) receptor blockade by pretreatment with BQ 610 or with the novel ET(A) receptor antagonist ETR-P1/FL peptide prevented ET-1 induced capillary perfusion failure and mucosal damage. In contrast, the ET(B) receptor antagonist IRL 1038 was not effective. These results indicate that, acting via the ET(A) receptor, elevated levels of circulating ET-1 under various pathophysiological conditions, such as septic or hemorrhagic shock, might impair nutritive perfusion of the intestinal mucosa and contribute to tissue injury.

Objectives: To determine the effects of a prophylactic intravenous infusion of adenosine on cardiopulmonary functions and oxygen-derived variables in a porcine model of endotoxemia., Design: Prospective, randomized, placebo-controlled, unblinded study., Setting: University research laboratory., Subjects: Thirty country bred pigs, aged 6 to 7 wks, weighing 24.9 +/- 0.65 (SEM) kg body weight., Interventions: Pigs were anesthetized by i.v. pentobarbital and fentanyl, intratracheally intubated, and mechanically normoventilated with a gas mixture of nitrous oxide/oxygen = 1:1. Intravascular catheters were inserted to allow for determination of arterial, central venous blood pressure, pulmonary artery occlusion pressure, cardiac output, and sampling of blood for gas analyses. Group 1 (n = 10) received a 330-min intravenous infusion of Salmonella abortus equi endotoxin (5 microg/kg body weight x hr). Group 2 (n = 10) received an additional intravenous infusion of adenosine (150 microg/kg body weight x min), started 30 mins before the infusion of endotoxin. Control groups 3 and 4 (n = 5 for both groups) received adenosine or physiologic saline, respectively., Measurements and Main Results: Parameters of cardiopulmonary function and oxygen-derived variables were calculated from pulmonary artery catheter measurements and blood gas analyses using standard formula. Plasma concentrations of purine compounds (adenosine, inosine, hypoxanthine) were determined by high-performance liquid chromatography. Since tumor necrosis factor-alpha plays a central role in the development of endotoxic shock, concentrations of this cytokine were determined in serum by enzyme-linked immunosorbent assay. Infusion of adenosine before the beginning of the infusion of endotoxin increased plasma concentrations of the nucleoside from 193 +/- 72 to 553 +/- 65 nmol/L and decreased the systemic vascular resistance by 50%. Although acting as a potent vasodilator under control conditions, adenosine did not aggravate the arterial hypotension elicited by endotoxemia but significantly increased cardiac output by a comparably small decrease in systemic vascular resistance, prevention of pulmonary vasoconstriction, and improvement of left ventricular performance. Despite significant pulmonary vasodilation, gas exchange was not worsened but slightly improved by adenosine. With the increase in cardiac output and arterial oxygenation, systemic oxygen delivery almost doubled. This adenosine-induced oxygen flux was not a surplus but was most likely utilized by tissues, as suggested by the much earlier beginning of the increase in the systemic oxygen consumption and the attenuation of the decrease in the gastric mucosal pHi. No effects of adenosine were observed on the endotoxin-induced increase in serum concentrations of tumor necrosis factor-alpha., Conclusions: Infusion of adenosine might be useful to improve flow-dependent oxygen delivery and tissue oxygenation during endotoxic shock without the induction of adverse cardiopulmonary side effects. The beneficial hemodynamic effects of adenosine appear not to be mediated by the inhibition of the release of tumor necrosis factor-alpha.

Endotoxin has profound effects on nitric oxide (NO) production, and considerable controversies exist as to whether these alterations are beneficial or deleterious. Increased mortality has been reported from nonselective inhibition of NO synthase. Results from selective inhibition of the inducible isoform (iNOS) appear largely positive. In a model of rat endotoxemia we have compared the early effects on hepatic morphology and function of selective and nonselective NO inhibition. Two hours after endotoxin injection (5 mg/kg intraportally) the rats were treated with either the selective iNOS inhibitor aminoethyl isothiourea (AE-ITU, 10 mg/kg), the nonselective NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg), or normal saline. The animals were observed for another hour. Using an immunohistochemical method, induction of iNOS was demonstrated in various tissues in all slices examined. No unequivocal benefit from NO inhibition was noted. Electron microscopic examination revealed widespread alterations of liver morphology, without obvious differences between the groups. Liver function, as assessed by ketone body ratio, hepatic venous acid base values, and bile production, was generally more adversely affected after NO inhibition. Even with the iNOS selective inhibitor AE-ITU no benefit was noted. We conclude that during the early phases of endotoxemia therapeutic reduction of NO production has no positive effects on liver function or morphology.

Background: Although isoflurane may cause subendocardial hypoperfusion in the presence of coronary stenosis because of its coronary arteriolar dilatory effects, it is not known how the subendocardial microcirculation is affected. The authors examined the effects of isoflurane on poststenotic subendocardial microvessels with coronary stenosis., Methods: The authors observed subendocardial microvessels in in situ beating swine hearts with or without critical stenosis of the left anterior descending coronary artery (LAD) with a needle-type videomicroscope during isoflurane- (ISO-H), adenosine- (ADE-H), and nitroglycerin- (NTG-H) induced hypotension (mean arterial pressure, 55 mmHg). Regional myocardial function, oxygen balance, and lactate metabolism in the region perfused by the LAD also were determined., Results: In swine with stenosis, there were no differences in heart rate, cardiac output, and LAD blood flow among the three types of hypotension. Regional lactate production and anterior interventricular venous pO2 were similar during ISO-H and NTG-H but higher during ADE-H. With videomicroscopy, about half as many subendocardial microvessels could be visualized during ADE-H as with ISO-H and NTG-H. The average decrease in the systolic diameter of subendocardial microvessels of greater than 100 microm was 9 +/- 6% during ISO-H and 12 +/- 5% during NTG-H, but no consistent phasic diameter changes were observed during ADE-H. In swine without stenosis, a systolic diameter decrease was observed during all three types of hypotension., Conclusions: These findings suggest that hypotension induced by isoflurane or nitroglycerin preserves phasic diameter changes in subendocardial microvessels in the presence of critical coronary stenosis, whereas that induced by adenosine does not.

Background: Current lung preservation consists of flushing of the donor organs, with successive hypothermic storage in an inflated state. Recently, hypothermic storage alone was reported to be superior in terms of functional recovery. This study was designed to investigate the metabolic, morphologic, and functional consequences of hypothermic storage alone, in experimental lung preservation., Methods: Orthotopic left-sided lung transplantation was performed in pigs. Donor lungs were flushed with Euro-Collins solution (n=6) or simply explanted (n=6) and stored for 18 hr at 4 degrees C. After this, left-sided single lung transplantation was performed. Sham-operated animals (n=6) served as control. Morphology and metabolism were analyzed in normal lungs, after ischemia and at the end of reperfusion. Gas exchange and pulmonary hemodynamics of the transplanted organs were measured, after exclusion of the native lung from perfusion and ventilation., Results: Metabolic and morphologic evaluation did not show a significant difference between the groups at the end of ischemia. Lungs preserved by hypothermia alone showed a functional recovery close to sham-operated animals and superior to flushed organs., Conclusions: Hypothermia alone is a sufficient means of preservation for explanted lungs for at least 18 hr.

Resuscitation using small volumes of hypertonic saline solutions normalizes cardiac output without fully restoring arterial pressure. This study compared the efficacy of either 7.2% saline/10% dextran 60 (HSDex) or the identical sodium load of normal saline (NS) to improve regional myocardial blood flow (MBF), contractile function, and oxygen metabolism in the presence of a critical coronary stenosis. Fourteen anesthetized, open-chest pigs (25 +/- 3.6 kg) were instrumented to assess left anterior descending coronary artery (LAD) flow, post-stenotic oxygen, and lactate metabolism, regional myocardial segment shortening (SS, sonomicrometry), and MBF (radioactive microspheres). After implementation of a critical LAD-stenosis, shock was induced by hemorrhage (mean arterial pressure (MAP) 45-50 mmHg for 75 min). Resuscitation was started by infusion (2 min) of either HSDex (n = 7,10% of blood loss) or NS (n = 7, 80% of blood loss); 30 min later 6% dextran 60 (10% of blood loss) was administered in both groups. The LAD-stenosis did not affect myocardial metabolism, SS, or MBF at rest. After hemorrhage, MBF remained unchanged from baseline in non-stenotic but decreased by 53% in post-stenotic myocardium (p < .05). The endo-epicardial flow ratio fell below 1.0 in both areas. SS decreased by 10-15% only in post-stenotic myocardium (p < .05). Resuscitation with both HSDex and NS restored cardiac index (CI) but not MAP. MBF increased above baseline values with either solution in non-stenotic while it remained at shock levels in post-stenotic myocardium, where ischemia persisted as evidenced by lactate production and depressed SS. Neither in non-stenotic nor in post-stenotic myocardium was the epi-endocardial flow ratio normalized upon resuscitation with HSDex or NS. We conclude that in the presence of a flow-limiting coronary stenosis, initial fluid resuscitation with both HSDex and the identical sodium load of NS failed to restore perfusion pressure, redistributed MBF in favor of normally perfused myocardium, and did not reverse ischemia in post-stenotic myocardium.

Despite improved preservation methods, graft dysfunction after liver transplantation continues to contribute considerably to postoperative morbidity and mortality. In clinical and experimental studies prostaglandin (PG)I2 analogs proved effective in the treatment of liver damage of different origin. Using in vivo fluorescence microscopy in a rat liver transplantation model, we studied the effect of donor bolus pretreatment with the PGI2 analog epoprostenol on hepatic graft revascularization. After epoprostenol bolus pretreatment (group 1: liver transplantation/PGI2), perfusion of liver sinusoids after reperfusion was significantly improved as compared with untreated donor livers (group 2: liver transplantation (95.2+/-0.6% vs. 75.3+/-3.8%, mean +/- SEM; P=0.001) and epoprostenol was found almost in the range of that in normal nontransplanted livers (99.4+/-0.2%). In addition, leukocyte adherence in liver lobules (21.0+/-3.5 vs. 115+/-11.5 n/lobule; P=0.001) and postsinusoidal venules (23.0+/-3.8 vs. 113+/-11.3 n/mm2 endothelial surface; P=0.002) was significantly reduced in the pretreated grafts. Bile production in the recipient was significantly increased by epoprostenol pretreatment of the donor (1.88+/-0.4 vs. 0.63+/-0.13 g/100 g liver*1 hr; P=0.015), indicating restored liver function. These results suggest that the prostacyclin analog epoprostenol is effective in preconditioning the graft prior to transplantation, i.e., improving preservation and increasing graft resistance to ischemia/reperfusion injury. Thus, favorable effects on early graft function after clinical liver transplantation may be achieved by introducing epoprostenol pretreatment into the harvesting procedure.

Somatostatin and its stable analogue octreotide are proposed to ameliorate the outcome from acute pancreatitis by inhibiting pancreatic secretion and preventing cell injury. This study investigated the effect of somatostatin analogue octreotide on pancreatic microcirculatory injury (by means of intravital fluorescence microscopy) and enzyme release after ischemia/reperfusion of the pancreas in rats. Octreotide, injected 15 min before the end of 2 h of ischemia as a bolus injection (50 micrograms kg-1 i.v.) or as a continuous infusion (50 micrograms kg-1 h-1 i.v.), attenuated postischemic reperfusion injury of the pancreas as evidenced by a significant (p < 0.05) improvement in capillary perfusion and decrease in leukocyteendothelium interaction in postcapillary venules compared to ischemia without treatment. Pancreas amylase concentration remained unchanged in the octreotide group but increased significantly (p < 0.05) in the ischemia group. These results indicate a protective effect of octreotide against postischemic reperfusion injury of the pancreas in rats.

To study the role of Kupffer cells (KC) as a cellular source of proinflammatory cytokines in hepatic ischemia/reperfusion, Sprague-Dawley rats were subjected to 20 min global hepatic ischemia. Sham-operated animals served as controls. Blood levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and interleukin 6 (IL-6) were determined after 10, 30, 60, 120, and 240 min of reperfusion and compared with spontaneous cytokine release by KC isolated after 60 min of reperfusion. Hepatic ischemia/reperfusion resulted in an enhanced (p < .01) spontaneous release of TNF-alpha (+482%), IL-1 alpha (+33%), and IL-6 (+175%) by KC. Kinetic analysis of cytokinemia revealed an early increase (p < .01) of TNF-alpha and IL-1 alpha within minutes upon reperfusion, while an elevation of IL-6 serum levels was observed with a delay of 2 h. Early cytokinemia was associated with dysfunction/injury of the liver, lung, and kidney after 4 and 24 h of reperfusion, respectively. These data indicate that hepatic ischemia/reperfusion results in Kupffer cell activation and increased cytokine levels, which may produce systemic inflammation and may be responsible for tissue injury locally and on remote sites.

Although the microvascular endothelium has been identified as the primary target site for the initiation of pancreatic islet graft rejection, little is known of the microvascular and cellular mechanisms involved, partly due to the lack of adequate models. Herein, we present a model for the in vivo assessment of the microcirculation of pancreatic islet grafts in mice. Isolated islets of Langerhans from immunocompetent hairless mice and immunoincompetent athymic nude mice were transplanted syngeneically into a specially designed dorsal skinfold chamber mounted on nondiabetic recipients. The islets' microcirculation was visualized by means of intravital fluorescence microscopy, and microcirculatory parameters were quantitatively analysed over a period of 14 days in the awake animal. Between day 2 and 4 after transplantation 84% (31/37; hairless mice) and 69% (36/52; nude mice) of the islet grafts revealed capillary sprouts and formation of new microvessels. On day 6, these sprouts were found interconnected, and red blood cell movement within the newly formed microvascular network was observed. The process of angiogenesis and revascularization was completed within 10 days after transplantation yielding a glomerulus-like network of capillaries as known for pancreatic islets in situ. Functional capillary density of the islet grafts ranged between 650 and 700 cm-1 in both hairless and nude mice. Within the islets' microvessels neither accumulation of leukocytes nor leukocyte-endothelial cell interaction was observed, indicating the lack of rejection and inflammation in these syngeneic islet grafts. We propose that this model provides a wide spectrum of promising experimental approaches for the study of microcirculatory and cellular mechanisms in free pancreatic islet transplantation.

Small volumes of hypertonic saline dextran (10% of shed blood volume [SBV] restore cardiac output (CO) and increase arterial pressure in hemorrhagic shock. Besides rapid expansion of plasma volume, a positive inotropic effect has been proposed as an additional mechanism for the immediate onset of the cardiovascular response. This study compares the effects of 7.2% saline/10% dextran 60 (HSDex, n = 8) and normal saline (NS; n = 6) on central hemodynamics and cardiac contractility assessed by end-systolic elastance (Ees; conductance technique) and segmental preload recruitable stroke work (sPRSW; sonomicrometry). In anesthetized open chest pigs (28 +/- 1 kg, mean +/- SEM) shock was induced by blood withdrawal (40% of blood volume) to maintain mean arterial pressure (MAP) at 45 mm Hg for 75 min. Resuscitation was started by bolus infusion (2 min) of either HSDex (10% of SBV) or the identical sodium load of NS (80% of SBV); 30 min later both groups received 6% dextran (10% of SBV). Hemorrhagic shock reduced CO (-45%) and left ventricular end-diastolic volume (Ved; -70%) while Ees increased (NS:2.2 +/- 0.4 to 7.5 +/- 1.8 mm Hg/mL, P < 0.05; HSDex: 1.9 +/- 0.2 to 9.1 +/- 2.6 mm Hg/mL, P = 0.085). Within 5 min after infusion of either solution CO returned to baseline values and MAP (NS +55%, HSDex +64%) and Ved (+100%) increased. Neither HSDex nor NS increased Ees above shock levels (NS, 8.7 +/- 4.9 mm Hg/mL; HSDex, 7.3 +/- 2.6 mm Hg/mL) and no group differences occurred in other measurements of contractility (dP/dt40,sPRSW). Plasma osmolality increased to 328 +/- 3 mOsmol/kg with HSDex.(ABSTRACT TRUNCATED AT 250 WORDS)

We present an experimental model that makes it possible to investigate the effects of global ischemia and reperfusion on microvascular perfusion and viability of ill-proportioned (poorly designed) arterial pattern skin flaps in hairless mice. Skin flaps were created on the ears of hairless mice by dissecting two of three nutritional vessel bundles at the ear base. Under these nonischemic conditions, 19 percent of the total flap area went on to necrose (as a result of poor flap design). Global ischemia was induced to the flap tissue for 6 hours with a tourniquet clamp directly after flap incision. The extension of perfused tissue area and flap viability were assessed at the microcirculatory level by intravital video microscopy at 1, 3, 6, and 18 hours and 7 days after reperfusion in animals treated with either normal saline (control) or the vasoactive drug buflomedil hydrochloride (3 mg/kg of body weight per day, i.v., starting 4 hours prior to flap creation and continued at daily intervals until the end of the experiments). In untreated animals (n = 18), 1 hour after clamp release we observed reperfusion of 39.55 percent (38.5/44.9) of total flap area. Reperfusion remained unchanged within the following 5 hours. Within the next 12 hours, reperfused flap area was dramatically reduced to 21.9 percent (15.1/58.4). Seven days thereafter, only 18.8 percent (10.9/42.2) of total flap area remained viable. In contrast, we found in buflomedil-treated animals (n = 18) that 57.3 percent (53.5/62.9) of the total flap tissue was reperfused within the first hour after clamp release (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Small volumes (4 mL/kg body weight (bw)) of hypertonic sodium chloride dextran effectively restore cardiac output and nutritional blood flow and increase arterial pressure in severe hemorrhagic shock. It has been suggested that the chloride anion be replaced with acetate to provide a solution that avoids the risk of hyperchloremia and has the advantage of supplying a buffering base to optimize hypertonic resuscitation. This study compares the effects of hypertonic sodium chloride dextran solution (7.2% NaCl/10% dextran 60 [NaCl-Dx]; n = 7) with sodium acetate dextran (10.4% Na-Ac/10% dextran 60 [NaAc-Dx]; n = 6) on hemodynamic, oxygen transport, and metabolic variables. Both solutions had the identical osmolality (2400 mOsmol/kg). Dogs (16.9 +/- 1.9 kg) were anesthetized and mechanically ventilated. Shock was induced by exteriorization of intestine and blood withdrawal (50% of blood volume) to maintain mean arterial blood pressure (MAP) at 40 mm Hg for 75 min. Thereafter, resuscitation was performed either with NaCl-Dx (4 mL/kg over 2 min) or NaAc-Dx (4 mL/kg over 4 min). During hypertonic resuscitation, there was a short-lasting decrease in MAP, which was more pronounced in the NaAc-Dx group (delta MAP -7.3 +/- 2.5 mm Hg). Cardiac index and oxygen consumption were normalized within 5 min after resuscitation with both solutions. In NaAc-Dx-treated animals, MAP remained at lower values as compared to NaCl-Dx-treated dogs at 5 and 30 min after resuscitation (52 +/- 3 vs 74 +/- 6, and 61 +/- 7 vs 79 +/- 12 mm Hg; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

In a prospective randomized double-blind placebo-controlled trial, the effect of rh-SOD, given in a dose of 200 mg intravenously during surgery to cyclosporine-treated recipients of cadaveric renal allografts, on both acute and chronic rejection events as well as patient and graft survival was investigated by analyzing the patients' charts retrospectively. The results obtained show that rh-SOD exerts a beneficial effect on acute rejection events as indicated by a significant reduction of (1) first acute rejection episodes from 33.3% in controls to 18.5%, as well as (2) early irreversible acute rejection from 12.5% in controls to 3.7%. With regard to long-term results, there was a significant improvement of the actual 4-year graft survival rate in rh-SOD-treated patients to 74% (with a projected half-life of 15 years) compared with 52% in controls (with an extrapolated half-life of 5 years). The beneficial effect of rh-SOD observed in this trial is not fully understood, although one can assume that the effect is related to its antioxidant action on ischemia/reperfusion injury of the renal allograft, thereby potentially reducing the immunogenicity of the graft. In addition and in accordance with the "response-to-injury hypothesis" in the pathogenesis of general atherosclerosis, rh-SOD has the potential to mitigate free radical-mediated reperfusion injury-induced acute endothelial cell damage that potentially may contribute to the process of chronic obliterative rejection arteriosclerosis.

Objective: This phase-I study transferred the concept of isovolemic hemodilution, which has been proven beneficial in the treatment of experimental acute pancreatitis to the patient., Summary Background Data: Pancreatic ischemia represents one main mechanism in the pathogenesis of necrotizing pancreatitis. Isovolemic hemodilution with dextran 60 has been shown experimentally to limit the progression of pancreatic necrosis by improving pancreatic microcirculation., Methods: Thirteen patients with clinically severe nonbiliary pancreatitis and CT-classification E according to Balthazar were enrolled. Exclusion criteria were anemia, coronary heart disease, chronic obstructive pulmonary disease, coagulopathies, and secondary referral. The volume of blood to be exchanged for dextran 60 was calculated from a nomogram based on body surface. Isovolemic hemodilution aimed at a hematocrit of 30%. Independent from the exchange procedure conventional fluid resuscitation was performed to adjust the central venous pressure at 6 +/- 2 mm Hg., Results: Whole blood (750-1,700 mL) was exchanged for dextran 60 during 45 to 70 minutes. No adverse effect was encountered; central hemodynamics were not affected. Considering a mean Ranson score of 5, mortality was low (7.7%). Progression of pancreatic necrosis was registered in only two patients subsequently undergoing surgical treatment (15%)., Conclusions: Isovolemic hemodilution is practicable in patients. A randomized trial has to prove whether isovolemic hemodilution can substantially alter the course of acute pancreatitis as anticipated from animal studies.

This study investigated the influence of hepatic arterialization on early graft function, microcirculation, and leukocyte-endothelial interaction after syngeneic orthotopic liver transplantation in Lewis rats. Livers were preserved for 17 hr in UW solution and transplanted without rearterialization (group 1: n = 10) or with immediate arterial reconstruction (group 2: n = 10). Graft function was analyzed by bile flow; microcirculation was assessed by laser Doppler flowmetry (LDF) and intravital microscopy (IVM). In addition, flow behavior of leukocytes was quantified by IVM after i.v. injection of the WBC marker acridine orange. Improved graft function in group 2 was indicated by increased bile production during the observation period of 90 min after reperfusion (7.18 +/- 0.62 vs. 3.63 +/- 0.63 ml/100 g liver [mean +/- SEM] P < 0.001). In arterialized grafts LDF values increased by 22.9 +/- 3.8% upon reperfusion of the hepatic artery (P = 0.004). Arterialization increased WBC velocities in sinusoids (group 1: 0.29 +/- 0.02 mm/sec, group 2: 0.34 +/- 0.01 mm/sec, P < 0.001) and postsinusoidal venules (0.43 +/- 0.05 vs. 0.64 +/- 0.05 mm/sec, P = 0.029). In addition, the number of nonperfused midzonal sinusoids decreased significantly (8.5 +/- 2.2% of all sinusoids analyzed vs. 4.2 +/- 1.3%, P = 0.048). However, the marked sinusoidal and venular WBC adherence observed 1 hr after reperfusion was not altered by arterialization. It is concluded that arterial reconstruction in rat liver transplantation improves microvascular perfusion and graft function but this improvement does not relate to WBC accumulation within the graft. We propose that studies on hepatic preservation and postischemic reperfusion in the rat should be based on the physiological model of dual vascularization.

Monitoring of nutritive blood flow in muscle is of particular importance to reconstructive surgeons, since ischemia/reperfusion in striated muscle is known to result in postischemic microvascular perfusion failure. Laser Doppler flowmetry has recently been introduced as an easy-to-use, noninvasive technique for continuous monitoring of microvascular tissue perfusion. Despite its popularity, there exists a great deal of controversy as to what actually generates the laser Doppler signal recorded from a given tissue. Intravital microscopy is a technique for direct visualization of the nutritional circulation in tissue. By using intravital microscopy, direct measurements of blood perfusion in individual segments of the nutritional microcirculation can be made. In 22 Syrian golden hamsters we performed laser Doppler flowmetry and intravital microscopy measurements in muscle tissue prior to and during reperfusion after 4 hours of tourniquet ischemia using the dorsal skinfold chamber model. Intravital microscopy (n = 10) revealed a heterogeneous capillary perfusion during the early reperfusion phase with a decrease (p less than 0.01) in functional capillary density to 49.4 +/- 17.0 percent of control. No recovery was observed after 24 hours of reperfusion. Laser Doppler flowmetry (n = 12) showed a parallel reduction of capillary red blood cell flux during the early perfusion phase to 43.9 +/- 22.6 percent of control values (p less than 0.01), and no recovery was observed after 24 hours of reperfusion. However, the laser Doppler flowmetry technique was not able to detect the capillary perfusion inhomogeneities shown by intravital microscopy. Postischemic reperfusion in striated muscle is characterized by a decrease in functional capillary density and a heterogeneous capillary perfusion. Laser Doppler flowmetry is a useful tool for monitoring microvascular tissue perfusion, although in striated muscle of the hamster it must be considered that accurate nutritional "capillary" flow readings can be grossly overestimated if larger vessels, such as arterioles and collecting venules, are contained in the measuring field of the laser Doppler probe.

The authors studied the effects of sevoflurane and isoflurane on systemic hemodynamics and regional blood flow distribution (microsphere technique) in 15 rats during general anesthesia with intravenous chloralose and controlled ventilation. Inhaled anesthetics were applied to reduce mean arterial blood pressure (MAP) to 70 mm Hg (1.66 vol% sevoflurane and 0.96 vol% isoflurane) and 50 mm Hg (MAP 50; 3.95 vol% sevoflurane and 2.43 vol% isoflurane). Control recordings were obtained with intravenous chloralose only. At a MAP of 70 mm Hg, both anesthetics reduced heart rate, cardiac output, and systemic vascular resistance to a similar degree. Isoflurane decreased systemic vascular resistance markedly at a MAP of 50 mm Hg and thereby maintained cardiac output at higher levels than sevoflurane. The left ventricular rate-pressure product decreased comparably with both anesthetics. Cerebral blood flow increased dose-dependently with both inhaled anesthetics but to a greater degree with isoflurane. Total hepatic blood flow remained unchanged from control at a MAP of 70 mm Hg but decreased at a MAP of 50 mm Hg. This was due to reductions of hepatic arterial and portal venous tributaries. Renal blood flow was reduced with only the high concentrations of the anesthetics. Myocardial blood flow was reduced at all concentrations of volatile anesthetic; however, the decrease was less with isoflurane. This would indicate a more pronounced coronary vasodilation by isoflurane as the rate-pressure product, as a measure of the actual left ventricular oxygen demand, decreased by comparable degrees with both anesthetics. Our results indicate that sevoflurane and isoflurane (each approximately 0.7 MAC) have no dissimilar systemic and regional hemodynamic effects at a MAP of 70 mm Hg in this animal model. At higher concentrations (approximately 1.7 MAC), cerebral blood flow was more with isoflurane than with sevoflurane and was associated with a more pronounced vasodilation in the myocardium.

Objective: To determine whether regional hypoperfusion of the interventricular septum occurs during ventilation with positive end-expiratory pressure., Design: Animal study., Animals: Anesthetized, closed chest dogs (n = 8)., Interventions: Induction of experimental adult respiratory distress syndrome (ARDS) and then ventilation with 10, 15, and 20 cm H2O of positive end-expiratory pressure., Measurements and Main Results: Cardiac output and regional interventricular septum blood flow were assessed at control, at induction of experimental ARDS, and at each level of positive end-expiratory pressure. Ventilation with 20 cm H2O of positive end-expiratory pressure decreased cardiac output (-32% vs. control, p less than .05), and did not change absolute, but increased relative (to cardiac output) interventricular septum blood flow. During experimental ARDS and ventilation at 20 cm H2O end-expiratory pressure, there was a redistribution of flow toward the right ventricular free wall (+93%, p less than .001) and the right ventricular part of the interventricular septum (+68%, p less than .01), while flow to the left ventricular interventricular septum and to the left ventricular free wall remained unchanged. Locally hypoperfused interventricular septum areas or findings indicative of interventricular septum ischemia were not observed during positive end-expiratory pressure., Conclusions: The decrease in cardiac output during positive end-expiratory pressure is not caused by impaired interventricular septum blood supply. The preferential perfusion of the right ventricular interventricular septum indicates increased local right ventricular interventricular septum oxygen-demand and suggests that during positive end-expiratory pressure, this part of the interventricular septum functionally dissociates from the left ventricular interventricular septum and the left ventricular free wall to support the stressed right ventricle.

Background: In vitro and in vivo experiments have demonstrated the role of oxidatively modified low density lipoprotein (oxLDL) in eliciting leukocyte/endothelium interaction during early atherogenesis., Methods and Results: In the present study we investigated the effect of dietary fish oil on oxLDL-induced leukocyte/endothelium interaction using intravital fluorescence microscopy in the dorsal skinfold chamber model in awake Syrian golden hamsters. Hamsters were fed for 4 weeks prior to the experiments with either standard laboratory chow or a diet supplemented with 5% of a fish oil concentrate (18% eicosapentaenoate, 12% docosahexaenoate). The efficacy of the fish oil diet was demonstrated by the incorporation of fish oil-derived omega-3 fatty acids into plasma, leukocyte, and erythrocyte lipids. In control hamsters (n = 7) and fish oil-fed hamsters (n = 7), leukocyte/endothelium interaction was assessed in the time course after intravenous injection of human LDL (4 mg/kg), oxidized by 7.5 microM Cu2+ (6 hours, 37 degrees C). In control hamsters, injection of oxLDL elicited the rolling and sticking of leukocytes to the endothelium of arterioles and postcapillary venules with a maximum 15 minutes after injection (arterioles: from 3 +/- 1 to 91 +/- 25 cells/mm2 at 15 minutes; venules: from 13 +/- 6 to 150 +/- 46 cells/mm2 at 15 minutes; mean +/- SD). This phenomenon was significantly reduced in fish oil-fed hamsters, where 15 minutes after injection of oxLDL leukocyte sticking reached a maximum of only 15 +/- 7 and 20 +/- 5 cells/mm2 in arterioles and postcapillary venules, respectively (p less than 0.01 versus control animals)., Conclusions: The results of the present study suggest that inhibition of leukocyte/endothelium interaction may be one of the mechanisms by which dietary fish oil exerts its protective effects on experimental and clinical atherogenesis.