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Both route and severity of infection may influence immunomodulator agents in sepsis. We studied the effect of each variable on HRL-3, an L-selectin-directed MAb that inhibits neutrophil function, in a rat sepsis model. Animals (n = 800) were randomized to be treated with either HRL-3 or placebo and to receive Escherichia coli either intravenously (IV) or intrabronchially (IB) in doses producing low or high mortality rates. Animals received antibiotics and were observed for 168 h. Route but not dose of E. coli altered the effects HRL-3 on mortality rate (mean hazards ratio +/- SE). With IV E. coli, compared with control, HRL-3 was beneficial and reduced the hazards ratio both early (0 to 6 h; -0.75 +/- 0.23) and late (6 to 168 h; -0.72 +/- 0.36) (P = 0.001 and 0.04, respectively, over all E. coli doses). In contrast, with IB E. coli HRL-3 reduced the hazards ratio early (-1.1 +/- 0.36) but worsened it late (0.87 +/- 0.23) (P = 0.002 for both effects over all E. coli doses) in patterns significantly different from IV E. coli (P < 0.0001). Compared with control, although HRL-3 did not alter lung neutrophil numbers or injury score at 6 or 168 h with IV E. coli (P = ns for all), it reduced both early and increased them late with IB E. coli (P

Previous analysis showed that selective inhibitors of five different host inflammatory mediators administered for sepsis, although beneficial with severe sepsis and high-control mortality rates, were ineffective or harmful with less severe sepsis. We hypothesized that severity of sepsis would also influence inhibition of superoxide anion, another inflammatory mediator. To test this, 6-h infusions of M40401, a selective SOD mimetic, or placebo were given to antibiotic-treated rats (n=547) starting 3 h after challenge with differing doses of intravenous Escherichia coli designed to produce low- or high-control mortality rates. There was a positive and significant (P=0.0008) relationship between the efficacy of M40401 on survival rate and control mortality rates. M40401 increased or decreased the log (odds ratio of survival) (means +/- SE), dependent on whether control mortality rates were greater or less than the median (66%) (+0.19 +/- 0.12 vs. -0.25 +/- 0.10, P=0.01). In a subset of animals examined (n=152) at 9 h after E. coli challenge, M40401 increased (mean effect +/- SE compared with control) mean arterial blood pressure (8 +/- 5 mmHg) and decreased platelets (-37 +/- 22 cells x 10(3)/ml) with high-control mortality rates but had opposing effects on each parameter (-3 +/- 3 mmHg and 28 +/- 19 cells x 10(3)/ml, respectively) with low rates (P < or = 0.05 for the differing effects of M40401 on each parameter with high- vs. low-control mortality rates). A metaregression analysis of published preclinical sepsis studies testing SOD preparations and SOD mimetics showed that most (16 of 18) had control mortality rates >66%. However, across experiments from published studies, these agents were less beneficial as control mortality rate decreased (P=0.03) in a relationship not altered (P=not significant) by other variables associated with septic challenge or regimen of treatment and which was similar, compared with experiments with M40401 (P=not significant). Thus, in these preclinical sepsis models, possibly related to divergent effects on vascular function, inhibition of superoxide anion improved survival with more severe sepsis and high-control mortality rates but was less effective or harmful with less severe sepsis. Extrapolated clinically, inhibition of superoxide anion may be most efficacious in septic patients with severe sepsis and a high risk of death.

We investigated whether inhibiting an endothelial adhesion molecule [intracellular adhesion molecule 1 (ICAM-1)] would alter outcome and lung injury in a similar fashion to inhibition of a leukocyte adhesion molecule (integrin CD11b) in a rat model of gram-negative pneumonia. Inhibition of ICAM-1 with monoclonal antibody (MAb) 1A29 (1 mg/kg sc or 0.2 or 2 mg/kg iv, q 12 h x 3) or of CD11b with MAb 1B6 (1 mg/kg sc, q 12 h x 3) were compared against similarly administered placebo proteins in rats challenged with intrabronchial Escherichia coli. After challenge, all animals were treated with antibiotics. ICAM-1 MAb (6 mg/kg, iv, total dose) increased mortality vs. control (P = 0.03). CD11b MAb (3 mg/kg, sc, total dose) did not significantly (P = 0.16) increase mortality rates, but this was not in a range of probability to exclude a harmful effect. All other doses of MAb had no significant effect on survival rates. ICAM-1 and CD11b MAbs had significantly different effects on the time course of lung injury, circulating white cells and lymphocytes, and lung lavage white cells and neutrophils (P = 0.04-0.003). CD11b MAb decreased, whereas ICAM-1 MAb increased these measures compared with control from 6 to 12 h after E. coli. However, from 144 to 168 h after E. coli both MAbs increased these measures compared with control rats but to a greater level with CD11b MAb. Thus both ICAM-1 and CD11b appear to be necessary for survival during E. coli pneumonia. Although these adhesion molecules may participate differently in early lung injury, with CD11b increasing and ICAM-1 decreasing inflammation and injury, both are important for the resolution of later injury. During gram-negative pneumonia the protective roles of ICAM-1 and CD11b may make their therapeutic inhibition difficult.

We investigated the effect of inhaled nitric oxide (NO) at increasing fractional inspired O2 concentrations (FIO2) on hemodynamic and pulmonary function during Escherichia coli pneumonia. Thirty-eight conscious, spontaneously breathing, tracheotomized 2-yr-old beagles had intrabronchial inoculation with either 0.75 or 1.5 x 10(10) colony-forming units/kg of E. coli 0111:B4 (infected) or 0.9% saline (noninfected) in one or four pulmonary lobes. We found that neither the severity nor distribution (lobar vs. diffuse) of bacterial pneumonia altered the effects of NO. However, in infected animals, with increasing FIO2 (0.08, 0.21, 0.50, and 0.85), NO (80 parts/million) progressively increased arterial PO2 [-0.3 +/- 0.6, 3 +/- 1, 13 +/- 4, 10 +/- 9 (mean +/- SE) Torr, respectively] and decreased the mean arterial-alveolar O2 gradient (0.5 +/- 0.3, 4 +/- 2, -8 +/- 7, -10 +/- 9 Torr, respectively). In contrast, in noninfected animals, the effect of NO was significantly different and opposite; NO progressively decreased mean PO2 with increasing FIO2 (2 +/- 1, -5 +/- 3, -2 +/- 3, and -12 +/- 5 Torr, respectively; P < 0.05 compared with infected animals) and increased mean arterial-alveolar O2 gradient (0.3 +/- 0.04, 2 +/- 2, 1 +/- 3, 11 +/- 5 Torr; P < 0.05 compared with infected animals). In normal and infected animals alike, only at FIO2 < or = 0.21 did NO significantly lower mean pulmonary artery pressure, pulmonary artery occlusion pressure, and pulmonary vascular resistance index (all P < 0.01). However, inhaled NO had no significant effect on increases in mean pulmonary artery pressure associated with bacterial pneumonia. Thus, during bacterial pneumonia, inhaled NO had only modest effects on oxygenation dependent on high FIO2 and did not affect sepsis-induced pulmonary hypertension. These data do not support a role for inhaled NO in bacterial pneumonia. Further studies are necessary to determine whether, in combination with ventilatory support, NO may have more pronounced effects.

We investigated the effects of recombinant granulocyte colony-stimulating factor (rG-CSF) during canine bacterial pneumonia. Beagles with chronic tracheostomies received daily subcutaneous rG-CSF (5 micrograms/kg body wt) or placebo for 14 days, beginning 9 days before intrabronchial inoculation with E. coli. Animals received antibiotics and fluid support; a subset received humidified oxygen (fractional inspired O2 0.40). Compared with controls, rG-CSF increased circulating neutrophil counts (57.4 vs. 11.0 x 10(3)/mm3, day 1 after infection; P = 0.0001), decreased plasma endotoxin (7.5 vs. 1.1 EU/ml at 8 h; P < 0.01) and serum tumor necrosis factor-alpha (3,402 vs. 729 pg/ml at 2 h; P = 0.01) levels, and prolonged survival (relative risk of death = 0.45, 95% confidence interval 0.21-0.97; P = 0.038). Also, rG-CSF attenuated sepsis-associated myocardial dysfunction (P < 0.001). rG-CSF had no effect on pulmonary function or on blood and lung bacteria counts (all P = not significant). Other animals challenged with endotoxin (4 mg/kg i.v.) after similar treatment with rG-CSF had lower serum endotoxin levels (7.62 vs. 5.81 log EU/ml at 6 h; P < 0.01) and less cardiovascular dysfunction (P < 0.05 to < 0.002) but similar tumor necrosis factor-alpha levels (P = not significant) compared with controls. Thus prophylactic rG-CSF sufficient to increase circulating neutrophils during bacterial pneumonia may improve cardiovascular function and survival by mechanisms that in part enhance the clearance of bacterial toxins but do not improve lung function.

We studied the effects of inhibiting and augmenting neutrophil function by using an immunocompetent rat model of infectious and hyperoxic lung injury. After intrabronchial Escherichia coli challenge at all fractional inspired O2 (FIO2) values studied (FIO2 = 0.21, 0.60, and 0.95) and after lethal O2 exposure alone (FIO2 = 0.90), lung injury, as measured by histological and physiological changes, was reduced by a CD11b/CD18-directed monoclonal antibody (MAb 1B6, P < 0.05 vs. controls) but was increased by recombinant granulocyte colony-stimulating factor (rG-CSF; P < 0.05 vs. control; MAb 1B6 vs. rG-CSF, P < 0.004). Pulmonary neutrophil counts were reduced by MAb 1B6 (P < 0.04) and increased by rG-CSF (P < 0.0004) compared with control animals. However, despite antibiotics, MAb 1B6 and rG-CSF both significantly increased the relative risk of death, independent of O2 concentration, during E. coli pneumonia (1.74 [symbol: see text] 1.20 and 2.39 [symbol: see text] 1.19, respectively, each P < 0.01). During lethal hyperoxia, MAb 1B6 increased the relative risk of death (1.76 [symbol: see text] 1.28, P < 0.16), whereas rG-CSF had no effect on survival (0.97 [symbol: see text] 1.28, P = 0.89). Thus inhibition of neutrophil function attenuated and enhancement worsened lung injury in response to infectious and hyperoxic challenges, supporting a pathophysiological role of the neutrophil in these processes. However, it is problematic that MAb 1B6 therapy, despite preventing lung damage, ultimately worsened host defenses and survival. Furthermore, rG-CSF also adversely affected survival during infectious lung injury, demonstrating the inherent risks of inhibiting or augmenting neutrophil function in an immunocompetent host during infection.

We investigated the effects of recombinant granulocyte colony-stimulating factor (G-CSF) in a canine model of septic shock. Awake 2-yr-old beagles were studied before and after intraperitoneal placement of an Escherichia coli-infected clot. Nine days before and until 3 days after clot placement, animals received daily high-dose (G-CSF (5 microgram/kg body wt; n = 17), low-dose G-CSF (0.1 microgram/kg body wt; n = 17), or a control protein (5 micrograms/kg body wt; n = 20). Survival rate was greater (P < 0.04, Wilcoxon test) in the high-dose G-CSF group (14/17) than in the low-dose G-CSF (10/17) and control (12/20) groups. High-dose G-CSF improved cardiovascular function, as evidenced by increased left ventricular ejection fraction (day 1 after clot; P < 0.001) and mean arterial pressure (day 2; P < 0.02) compared with low-dose G-CSF and control groups. High-dose G-CSF increased (P < 0.001) mean peripheral neutrophils before (-3 days) and after (2 h to 4 days) clot and produced a more rapid (P < 0.001) rise (day 2) and fall (day 4) in mean alveolar neutrophil numbers compared with the low-dose G-CSF and control groups. High-dose G-CSF decreased mean serum endotoxin (2-8 h; P < 0.002) and tumor necrosis factor (2 h; P < 0.02) levels and lowered blood bacteria counts (2-6 h; P < 0.04) compared with the low-dose G-CSF and control groups. Thus, in this canine model, G-CSF sufficient to increase peripheral neutrophils before and during peritonitis and septic shock enhances host defense, reduces cytokine (tumor necrosis factor) levels, and improves cardiovascular function and survival.

We examined the ability of commonly used clinical parameters to quantify acute hemorrhage in dogs. Eight animals were bled 40 ml/kg body wt over 100 min. Ten hemodynamic and 20 blood laboratory parameters were obtained every 10 min to construct, with use of linear regression analysis, models that quantify blood loss. During model construction, the best indicator of quantity of hemorrhage was arterial base deficit [ABD; coefficient of variation (CV) 35%]. This model was more accurate (P < 0.05) than 27 others (CV range 43 to 63%) and similar to systolic (CV 40%) and mean (CV 40%) arterial pressures. In validation studies in 10 additional animals, our best models based on ABD and systolic and mean arterial pressures each unexpectedly showed a significant (P < 0.05) decrease in accuracy (CV 86, 57, and 60%, respectively) attributable to large baseline (before hemorrhage) variability among animals. To eliminate this variability, models based on changes from baseline measurements were investigated. The best predictor of change in blood volume was change in ABD (CV 27%). This model was significantly (P < 0.05) more accurate than any of 27 others (CV range 36 to 65%) and similar to change in venous base deficit and venous pH (each CV 31%). When validated, acid-base models such as ABD, venous pH, and arterial bicarbonate were the best predictors of volume change (CV range 28 to 40%). With the use of multivariate analysis, pairwise combinations of single parameter models (n = 465) improved prediction errors only minimally. In summary, most commonly used hemodynamic and blood indexes could not be validated as accurate measurements in quantifying hemorrhage. In contrast, changes in acid-base parameters were validated as moderately accurate predictors of blood volume changes and therefore may have utility in the assessment of patients with ongoing hemorrhage.

We compared the early and late pulmonary effects of human recombinant tumor necrosis factor (TNF) and interleukin 1 (IL-1) challenges in awake dogs with chronic tracheostomies. Serial blood gas analysis, bronchoalveolar lavage (BAL) with cell and protein analysis, intravascular catheter hemodynamics, and radionuclide left ventricular ejection fractions (LVEF) were determined before and after infusion of TNF (60 micrograms/kg body wt, n = 8), IL-1 (1,000 micrograms/kg body wt, n = 6), or heat-inactivated IL-1 (n = 6, controls). Controls given heat-inactivated IL-1 had no changes (P = NS) in any pulmonary parameter throughout the study. Animals given IL-1 had a transient increase (P less than 0.05) in BAL neutrophil concentration 1 day after infusion but no other changes (P = NS) in pulmonary function throughout the study. Animals given TNF had early (0-4 h) decreases (P less than 0.05) in arterial PO2, increases (P less than 0.05) in physiological shunt fraction and alveolar-to-arterial PO2 gradient, and a high mortality rate (50%). In TNF animals, volume challenges at 4 h were associated (P less than 0.05) with death and noncardiogenic pulmonary edema. In TNF survivors, hypoxemia persisted for 2-3 days and was associated with increases (P less than 0.05) in alveolar protein and neutrophil concentration on days 1 and 3, respectively, which in survivors returned to near normal over 6-21 days. Animals challenged with TNF and not IL-1 had reversible depression of LVEF similar in time course to abnormalities in arterial PO2. In this study, TNF (but not IL-1) challenges were lethal and produced acute pulmonary dysfunction sustained over days (reversible in survivors) that was similar to that seen in human septic shock. The ability of TNF to induce pulmonary injury similar to bacterial shock suggests that TNF is a key mediator of sepsis-induced lung injury. Furthermore, because TNF challenge induced both sustained pulmonary and cardiac injury, TNF may be a common pathway for the multiple organ dysfunction that occurs during septic shock.

The hemodynamic response to inhalation anesthesia is influenced by three factors: 1) the specific drug, 2) the dose, and 3) individual characteristics of the subject. To investigate the importance of these factors on the cardiovascular response, we administered five doses [0, 0.5, 1.0, 1.5, and 2.0 minimum alveolar concentration (MAC)] of enflurane, halothane, and isoflurane to each of six dogs. Twelve hemodynamic variables were measured. For all variables, a change in the dose of each drug produced a consistent effect in each dog. Increases in dose resulted in significant decreases in seven variables [left ventricular ejection fraction, cardiac index (CI), stroke volume index (SVI), mean arterial pressure (MAP), mean pulmonary arterial pressure (MPAP), left ventricular stroke work index (LVSWI), and heart rate (HR)] and a significant increase in one variable [central venous pressure (CVP)]. In contrast, the response of individual dogs to different drugs was not consistent. For seven variables [MAP, MPAP, LVSWI, CVP, pulmonary capillary wedge pressure (PCWP), end-diastolic volume index (EDVI), and end-systolic volume index (ESVI)], a significant difference in the responses of a dog to two drugs was greater than zero, whereas a significant difference in the response of at least one other dog to the same two drugs was less than zero (discordant dog-drug interactions). Thus, in contrast to the consistency of the cardiovascular response to changes in dose, the hemodynamic response to different drugs was inconsistent among dogs. We also studied the effect of fluid challenge on hemodynamic response at 1.5 or 2.0 MAC of the three drugs given to each dog.(ABSTRACT TRUNCATED AT 250 WORDS)