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Purpose This study addresses the effect of short myocardial ischemia on inhibitory effect of ATP for mitochondrial cytochrome c oxidase (CytOx) activity in myocardium and subsequent hemodynamic alterations. The activity of CytOx is inhibited by ATP (primary substrate control). This additional mechanism was proposed to be switched off at higher mitochondrial membrane potential values in case of stress. The ATP-dependent allosteric enzyme inhibition (second respiratory control) is suggested to reduce the formation of reactive oxygen species and thus is pivotal for cytoprotection. This report addresses the possible involvement of this mechanism in case of myocardial preconditioning. Methods Rat hearts were perfused in a Langendorff system (n = 5 each group). The first two groups underwent short recurrent ischemic periods (three times 5 min) and subsequent high or low reperfusion for 40 min. Besides four control groups, hearts were exposed to an ischemia of 15 min and high flow reperfused for 30 min, in addition. Hemodynamic data were evaluated in parallel. Mitochondria were separated for the polarographic respiration measurements in the presence of ADP or ATP, respectively. Phosphorylation patterns of the CytOx subunits were studied by immunoblotting with P-Ser, P-Thr, and P-Tyr antibodies. Results Short recurrent episodes of ischemia result in an ATP-dependent inhibition of CytOx. Electrophoretic analysis and blotting techniques reveal different phosphorylation patterns of the enzyme. Frequent short-lasting ischemic impacts and subsequent increased coronary flow seem to be essential for this effect. Conclusion The procedure of preconditioning is likely to be dependent on the mechanism of ATP-dependent inhibition of CytOx activity.

In this study, the microvascular tissue oxygenation and oxidative muscle metabolism during graded hypoxia and reoxygenation were examined in a rabbit model by near-infrared (NIR) spectroscopy and correlated with high-energy phosphates measured by (31)P nuclear magnetic resonance (NMR) spectroscopy.Graded hypoxia was performed in a New Zealand rabbit model (n = 20, 2.0 ± 0.4 kg) by a stepwise reduction of the fraction of inspired oxygen (FiO(2)) from 0.3 to 0.05 (intervention group versus control group). Recovery and reoxygenation were achieved using FiO(2) of 0.3. A noninvasive NIR spectroscopy sensor and NMR probe was positioned on the surface of the prepared pedicled latissimus dorsi muscle. Microvascular tissue oxygenation (oxyhemoglobin, HbO(2); deoxyhemoglobin, HHb) and redox state of cytochrome oxidase (CytOx) were measured by NIR spectroscopy and correlated with standard values of oxidative muscle metabolism (phosphocreatine, PCr; adenosine triphosphate, ATP) measured by time-resolved (31)P NMR spectroscopy (4.7T).Significant correlation was found between PCr and HbO(2) (r = 0.85, P0.001) and HHb (r = -0.75, P0.001). β-ATP levels correlated significantly with CytOx (r = 0.87, P0.001).The data suggest that changes in high-energy phosphates (PCr- and ATP-levels) correlate closely with microvascular tissue oxygenation (HbO(2), HHb, CytOx) measured by NIR spectroscopy.

Simultaneous measurements of extracellular pH, potassium (K(+)), and calcium (Ca(2+)) activity might be indicative of myocardium vitality or ischemia. Ten consecutive patients undergoing elective coronary artery bypass grafting were studied. Epicardial extracellular pH, potassium, and calcium were measured by a miniaturized disposable multi-sensor probe. Blood gases and electrolytes were derived with measurements of arterial and mixed venous blood samples at intervals during surgery. The mean epicardial baseline levels for pH in all patients were 8.04+/-0.22 arbitrary units (AU) for the right ventricle (RV) and 8.03+/-0.21 AU for the left ventricle (LV); for Ca(2+) 0.23+/-0.07 mmol/l (RV) and 0.20+/-0.10 mmol/l (LV); and for K(+) 4.54+/-1.51 mmol/l (RV) and 4.38+/-0.57 mmol/l (LV). Before ischemia, epicardial pH was moderately (p

Effective myocardial oxygen supply should not be compromised during cardiac surgery as it is essential to avoid circulatory and cardiac dysfunction. Local measurement of myocardial oxygen partial pressure (pO2) was therefore introduced into the operative monitoring of myocardial ischemia. The aim of the present study was to assess whether myocardial oxygen partial pressure correlates with the content of high energy phosphates (HEPs). Seven male rabbits were examined in parallel with measurement of myocardial pO2 by an implanted Clark electrode and 31phosphorus-NMR spectroscopy. The ventilatory management established hyperoxygenation followed by systemic hypoxia with hypercapnia for 20 min. Additionally, analysis of end-expiratory gas composition in combination with blood gas analysis was performed simultaneously, and hemodynamic parameter was recorded. Under hypoxic conditions the cardiovascular system was severely compromised, whereas the myocardial pO2 was only moderately impaired (pO2M 45.0+/-16.0 mm Hg). Immediately before cardiac arrest, low values of arterial and venous pO2 were found (17.6+/-6.0 and 12.9+/-6.1 mm Hg). In contrast to near normal myocardial pO2, HEP content in the myocardium was considerably reduced and inorganic phosphorus was increased. Artificial ventilation leading to systemic hypoxia and eventually circulatory arrest resulted in almost normal myocardial pO2 but severely compromised HEP content. This somewhat unexpected finding requires further clarification, but is in accordance with findings reported previously where regulatory mechanisms have been shown to play a role in the pathophysiology of severe hypoxic conditions such as those for cellular oxygen delivery and demand, P/O coupling and finally control of HEP production facilitating the interaction between respiratory chain and myoglobin oxygen transport.

Introduction: Recent innovations in laser scanning technology provide a potentially useful tool for three-dimensional surface registration for image-guided surgery. The purpose of this study is to evaluate the clinical reliability of this technique in oral and maxillofacial surgical procedures using image-guided navigation. Methods: In an experimental step, a stable anthropomorphic skull model with prelabeled markers was scanned and registered with laser surface scanning (z-touch®, BrainLAB) and marker-based algorithms. The registration protocol was then repeated 25-times. Root mean square error (RMSE) and target difference values were compared for their suitability for this application. Twelve patients with different indications for oral and maxillofacial surgery were planned for image-guided surgery using a passive infrared surgical navigation system (VectorVision®, BrainLAB). Preoperative computed tomography (CT) scans were carried out with newest 16-line multisclice CT-scanner (Siemens Somatom Sensation 16). The new markerless laser surface scanning technique was applied in all intraoperative patient registrations. Registration error was noted. The clinical application accuracy was determined for anatomical landmark localization deviation. Results: In the experimental protocol a mean registration error (RMSE) or target difference of 1.3 (0.14) or 2.08 (0.49) mm for laser scanning and 0.38 (0.01) or 0.99 (0.15) mm for marker registration was found. The differences for RMSE and target localization were statistically significant (p

BACKGROUND This study was undertaken to investigate the physiological effects of cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) on cerebral oxygen metabolism estimated by near-infrared spectroscopy (NIRS). METHODS Ten newborn piglets (2.1 to 2.6 kg) were monitored with right frontal NIRS; the right jugular bulb was cannulated for intermittent sampling of jugular venous blood. All animals underwent CPB, cooling to a core temperature below 15 degrees C, 60 minutes of DHCA followed by subsequent reperfusion and rewarming. Continuously recorded NIRS data and intermittent jugular venous blood values were compared. RESULTS NIRS performance was examined over the jugular venous oxygen saturation (SjvO2) range of 40 to 98 %, a linear correlation was found between SjvO2 and NIRS-derived regional cerebral oxygen saturation (rSO2) (r = 0.91, p < 0.001). A correlation was observed between the cellular oxidation NIRS-parameter cytochrome oxidase aa3 (CytOx) slope during the DHCA period in relation to rectal and nasopharyngeal temperature immediately before the onset of DHCA (r = 0.75 and 0.85, p < 0.001). CONCLUSIONS This study suggests that NIRS-measured hemoglobin oxygenation parameters may reflect functional changes in cerebral hemodynamics and brain tissue oxygenation, while CytOx values represent related effects on intracellular oxidative metabolism.

Early detection of myocardial ischaemia is a central problem in cardiological and cardiosurgical intensive care. A new approach is the use of ion-selective electrodes implanted directly on the myocardium, enabling detection of increased potassium activity as an indication of general hypoxia. After a comprehensive study of the electrode parameters, an animal experiment was carried out, in which it was found that respiration-induced hypoxia resulted in an increase in epicardial potassium activity (p < 0.01). Blood gas analysis performed simultaneously revealed reduced arterial pO2, but no acidosis. Haemodynamic data evidenced hypoxic depression of circulatory parameters. Histological examinations of the myocardium beneath the electrodes revealed typical lymphocytic infiltration. Electron microscopy demonstrated crystolysis in the mitochondria as an early sign of hypoxia, thus confirming the sensitivity of these electrodes. This underscores the potential of ion-selective electrodes for the detection of myocardial ischaemia, and they should now be investigated in the clinical setting.

Advances in intra-operative imaging and the development of new minimally invasive techniques are having an ever greater impact on modern surgery. Mobile CT scanners in the operating room is a new technique that permits image-guided surgery, and helps minimize postoperative complications. We report on our initial experience with intraoperative CT scanning during surgery on patients suffering lateral midface trauma. A mobile CT unit, the Tomoscan M (Philips, Utrecht, Netherlands) set up in the operating room, was evaluated in 6 patients with zygomatic bone fractures. The patients were placed on the CT scanner table, which is detachable from the gantry. The unit is powered by batteries charged from an ordinary ring mains supply via a conventional plug. The CT images obtained were of good quality in all cases. No technical problems were observed during surgery. Using repeat CT scans, the procedure also permits accurate intraoperative monitoring of the anatomical repositioning of the bone fragments, and accurate implantation. No intraoperative or early postoperative complications were observed. This new technical aid ensures highly accurate reduction of the bone fragments, and minimizes the need for reoperation. High-quality intraoperative imaging with surgical navigation increase surgical outcome, and expand the spectrum of minimally invasive surgery.

The use of minimally invasive procedures in maxillofacial surgery will require new technologies involving surgical navigation and techniques. The aim of our studies is to improve the efficacy of image-guided navigation in combination with endoscopically assisted techniques for minimally invasive craniomaxillofacial procedures. Prospective evaluation was made of all patients who underwent surgical procedures using image-guided navigation. The most common type of operations performed were endoscopically assisted interventions within the paranasal sinuses, fracture treatment, the resection of bone lesions and further miscellaneous interventions. Our experience to date suggest that image-data based techniques are eminently applicable, providing a feasible alternative to conventional surgical treatment.

The purpose of this prospective clinical study was to evaluate new resorbable implants for bone fixation. The plates and screws are made of poly (D, L)lactide (PDLLA). Bioresorbable osteosynthesis and fixation (ResorbX) has been applied in 22 patients. Indications for operations were craniofacial trauma (malar, orbital-floor or frontal bone fractures) or orthognathic procedures (Le Fort-I-osteotomies) as well as the surgical correction in case of craniofacial syndromes. In the initial follow up, the first patients showed clinically and radiologically uneventful fixation and healing of the bone. There were no implant material related complications. Overall, the advantages of PDLLA-implants appear to be their ease of use, radiolucency and resorption, although further experience is needed to determine the longterm benefits of biodegradable implants.

Objective: Recent observations have been shown that the induction and accumulation of heat shock proteins (HSPs) by short exposure to nonlethal whole-body hyperthermia with normothermic recovery are closely associated with transient resistance to subsequent ischemiareperfusion challanges. Here, this study was performed to investigate whether a shortly heat shock pretreatment affects the left ventricular (LV) function after cold cardioplegic ischemia in reperfused neonatal rabbit hearts. Methods: Hearts from neonatal New Zealand White rabbits were isolated perfused (working heart preparation) and exposed to 2 h of cold cardioplegic ischemia followed by reperfusion for 60 min. To induce the heat shock response neonatal rabbits (na 5, HT-group) were subjected to whole-body hyperthermia at 42.0‐42.58C for 15 min, followed by a normothermic recovery period of 60 min, before harvesting and the onset of global hypothermic cardioplegic arrest. Another set of hearts (na 5, control group) without a heat treatment underwent a similar perfusion and ischemia protocol served as control. The postischemic recovery was assessed by measuring several parameters of LV function. LV biopsies from all control and heat treated animals were taken before ischemia and at the end of reperfusion to examine myocardial HSP levels by Western blot analysis. Results :A t 60 min of reperfusion the HT-group showed significant better recovery of ventricular function such as LV developed pressure (DP) (74.6 ^ 10 vs. 52.1 ^ 8.5%, P , 0.05), LV positive dP/dt (910 ^ 170 vs. 530 ^ 58 mmHg/s, P , 0:01) and LV end-diastolic pressure (LVEDP) (8 ^ 2 vs. 18.4 ^ 5 mmHg, P , 0:05) than control. Myocardial oxygen consumption (MVO2) was significantly higher in the HT-group compared with control (0.054 ^ 0.006 vs. 0.041 ^ 0.002 ml/g per min, P , 0:05). Significant postreperfusion lower level in lactate production was observed in the HT-group (0.83 ^ 0.11 vs. 1.67 ^ 0.8 mmol/l, P , 0:05). Also, the recovery of hemodynamic parameters such as aortic flow, coronary flow and cardiac output was significantly superior (P , 0:05) in the HT-group. Furthermore, high expression of HSP72 1 /73 1 were detected in the myocardial tissue samples of heat-treated rabbits by immunoblotting, appearing even at 60 min of normothermic recovery after heat stress. Conclusions: These data in the immature rabbit heart indicate that previous shortly heat treatment with high level expression of heat shock proteins (HSP72 1 /73 1 ) before hypothermic cardioplegic ischemia provides transient tolerance against myocardial injury and could be an improvement for the postischemic functional recovery of neonatal hearts. q 2000 Elsevier Science B.V. All rights reserved.

In der vorliegenden Studie wurde ein Kaninchenmodell verwendet, um den Einflus eines 60minutigen Kreislaufstillstandes in tiefer Hypothermie auf die intrakraniellen Veranderungen in der Verfugbarkeit von Sauerstoff im Hirngewebe sowie die Hindurchblutung untersuchen zu konnen. Mit der Dauer des totalen Kreislaufstillstandes nahm der Hirngewebe-Sauerstoffpartialdruck (ptiO2) kontinuierlich ab. In der Reperfusion und Erwarmung war die zerebrale Reoxygenierung mit subnormalen ptiO2-Werten stark verzogert. Am OP-Ende (nach Reperfusion und Entwohnung von der EKZ) ergaben sich signifikant verminderte Werte fur den ptiO2: 25±4 mmHg vs. Ausgangswert: 38±5 mmHg (p

Using a dual channel near infrared (NIR) in vivo optical spectroscopy (INVOS) system (INVOS 3100A, Somanetics Corp. Troy, MI, USA) we investigated the relationship between jugular venous oxygen saturation (SjvO2) and regional cerebral oxygen saturation (rSO2) in 30 infants and children (mean age 4.5 years) with congenital heart disease undergoing cardiac catheterisation. The NIRS-SomaSensor (emitter and dual receiver probe) was applied at a standardised right fronto-temporal location (over the right frontal cortex) on the infant's head and covered with an adhesive flexible bandage. Using NIR light (730 and 810 nm) and two source-detector spacings (3 and 4 cm from the transmitter), percentage values of rSO2 were calculated from detected haemoglobin saturations. Simultaneously, jugular venous oxygen saturation (SjvO2) monitoring was performed via a catheter placed in the right internal jugular vein with its tip positioned in the jugular bulb, as verified by fluoroscopy. To compare the reliability of NIRS measurement characteristics, jugular venous blood was analysed for SjvO2 as a reference measure of global cerebral oxygenation, by co-oximetry (OSM3-Hemoximeter, Radiometer Copenhagen, Denmark). Other measured variables included pulse oximetry, arterial blood pressure, and venous and arterial oxygen saturations. Over a jugular venous oxygen saturation range of 31-83%, a significant positive linear correlation was found between rSO2 (NIRS measurement) and SjvO2 (jugular bulb oximetry) (r = 0.93, p < 0.001). No significant correlation was observed between rSO2 values and arterial blood saturation or pulse oximetry. The quantitative correlation between rSO2 (haemoglobin oxygenation in a small hemi-elliptical area of the brain) and reference SjvO2 measurement (method for monitoring global cerebral oxygenation) suggests that NIRS measurement with subtraction algorithm should identify predominantly intracranial saturation in the pediatric age group, and will tend to reflect global oxygenation under physiological conditions. Transcranial oximetry using dual receiving channel NIRS offers a noninvasive, real-time, reliable and practicable means of monitoring cerebral haemoglobin oxygenation changes infants and children with cyanotic and noncyanotic congenital heart disease.

Currently, no reliable minimally invasive method of measuring cardiac output continuously in neonates and children undergoing cardiac surgery is available. An extravascular Doppler probe was used to measure cardiac output in 15 New Zealand White rabbits (average weight 3.5 kg, range 2.5-4.5 kg). The results obtained were compared with cardiac outputs determined using the aortic thermodilution principle. The mean cardiac outputs measured with the extravascular Doppler probe was 0.37 +/- 0.01 l/min as compared with 0.39 +/- 0.01 l/min with aortic thermodilution. Regression analysis revealed a close correlation (r = 0.973) between the two techniques. The extravascular Doppler techniques is an option for continuous and reliable cardiac output measurement in small animals used in surgical experiments (open chest models) and in neonates or children during surgical repair of complicated congenital heart conditions.

Early detection of myocardial ischaemia following cardiac surgery remains a central problem of intensive care medicine. On the basis of the observation in the epicardium that an elevated potassium activity accompanies myocardial ischaemia, a miniaturized electrode system for the measurement of epicardial potassium concentration was constructed and tested. Different types of electrode were implanted in two groups of rabbits. The electrode parameters were satisfactory (slope, screening) and it proved possible to record interference-free myocardial ion potentials, which with regard to the ionophores used is selective for potassium ion activity in the solid phase electrode. The system thus meets the prerequisites for further investigations into its suitability for early diagnosis of ischaemia.

There is currently no efficient and reliable clinical means of assessing the degree of ischemia- and reperfusion-associated damage in microvascular transplants. The objective was to study correlation of tissue oxygen tension measurements with tissue oxygen saturation, cytochrome oxidase redox state, and tissue viability.Latissimus dorsi muscle was dissected and mobilized in New Zealand white rabbits (n = 30, 2.5 ± 0.5 kg). Muscles were exposed to warm ischemia in two groups with either 4 or 6 h, followed by reperfusion. Tissue PO(2) was measured with a miniature intramuscular oxygen sensor (Licox microprobe; Integra Neurosciences, Ratingen, Germany) all along with tissue hemoglobin saturation (rSO(2)) and cytochrome oxidase aa3 redox state (CytOx) by in vivo near-infrared spectroscopy. Linear correlation was performed between tissue PO(2) and rSO(2), CytOx and tissue viability.After ischemia and reperfusion, tissue PO(2) and CytOx recovery was significantly decreased in both groups compared with control (4 h: P0.05; 6 h: P0.01). Significant correlations between changes in tissue PO(2) and rSO(2) (r = 0.92; P0.01), CytOx (r = 0.90; P0.01), wet-to-dry ratio (r = -0.97; P0.01), and mitochondrial viability index (r = 0.97; P0.01) were found.Tissue oxygen tension measured with microprobes correlated closely with tissue oxygenation, cellular oxygen utilization, and the extent of ischemia reperfusion injury.

Conflicting results have been reported with regard to the neuroprotective effects of steroid treatment with cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA). We evaluated the mode and severity of neuronal cell injury in neonatal piglets after prolonged DHCA and the possible neuroprotective effect of systemic pretreatment (>6 h before surgery) with large-dose methylprednisolone (MP). Nineteen neonatal piglets (age

Background Recent studies have shown a relationship between alterations in tissue oxygen metabolism and cellular changes following ischemia and reperfusion, such as energy store depletion and intracellular acidosis. The aim of this study was to evaluate the relationship between tissue energy metabolism and intramuscular tissue oxygen tension in the mobilized latissimus dorsi muscle. Material and methods The latissimus dorsi muscle was raised in New Zealand white rabbits ( n = 10, 2.5 ± 0.5 kg). During 4 h of ischemia and 2 h of reperfusion, the intramuscular tissue oxygen tension (Licox PO 2 -microcatheter probe) and the status of phosphorylated muscle energy metabolites were measured using a high-field 31 P-NMR spectrometer. Linear correlation was performed between 31 P-NMR data and tissue oxygen tension readings. Results The tissue oxygen tension (PO 2 ) values correlated significantly with phosphocreatine (PCr) ( r = 0.96, P r = 0.64, P r = 0.82, P Conclusions On the basis of these findings, we conclude that the data provided by tissue oxygen tension measurement offer a real time minimally invasive estimate of muscle oxidative metabolism during ischemia and reperfusion.

Myocardial hypoxia is accompanied by increased epicardial potassium activity. In this experimental study in rabbits (n = 13), with ion-selective probes, we correlated our findings with an exact evaluation of myocardial oxygen tension, hemodynamic data and arterial and venous blood gas analysis. The epicardial potassium activity had good correlation with these parameters (pm = −0.95, pco = −0.93 and pa = −0.72, pv = −0.96, respectively). Therefore, the clinical use of these electrodes can be recommended for continuous monitoring in intensive care units.

Laser-induced interstitial thermal therapy (LITT) is a proven minimally invasive surgical technique for the treatment of haemangiomas and vascular malformations, and various tumours. The intra-lesion application of thermal energy destroys regional tissue. The percutaneous placement of the laser fibre for photocoagulation is done without the benefit of direct visual control. Image-data-based LITT was performed in patients (five procedures) with extensive venous malformations in the maxillofacial area. The system comprised a specially developed Nd:YAG laser fibre introducer set used in conjunction with fused high-resolution computed tomography, and magnetic resonance image-data--based surgical navigation. In all cases, follow-up examination clearly showed a diminishment in tumour volume, and all patients reported significant subjective improvement. The results suggest that navigation-guided LITT can be performed safely, preserving vital structures from collateral thermal damage.

Background Recent findings indicate that molecular chaperones actively participate in myocardial cytoprotection. Moreover, ischemic tolerance can be induced in humans by brief ischemic events. Therefore, we investigated patients with severe angina attacks before coronary artery bypass grafting. We focused on appearance of anti-hsp70 antibodies as an immunologic response to heat shock protein induction by ischemia followed up by hemodynamic measurements perioperatively. We correlated these clinical findings with the presence of antibodies against hsp70 and the antioxidative capacity of patients' sera. Methods Thirty-five consecutive patients with coronary artery disease scheduled for coronary artery bypass grafting were included. Seventeen patients had severe angina, and 18 patients suffered from chronic stable angina preoperatively. In the patients' sera, antibodies against hsp70 were detected by enzyme-linked immunosorbent assay, and antioxidative capacity was detected using the chromogen assay. Cardiac output and pulmonary capillary wedge pressure were measured using a thermodilution catheter. We also evaluated C-reactive protein and creatine kinase MB isoenzyme, and performed a conventional leukocyte count. Results The sera of the 17 patients with severe angina attacks before surgery contained antibodies against hsp70 and a low antioxidative capacity. The interval between a severe angina attack and anti-hsp70 antibody titer are inversely correlated. These patients had better cardiac output and lower pulmonary capillary wedge pressure values after surgery. Conclusions Severe angina before cardiac surgery coincided with an improved outcome as measured by hemodynamic variables as compared with chronic stable angina. This finding correlated significantly with a low antioxidative capacity and the presence of antibodies against hsp70. These pathophysiologic mechanisms might therefore play a role in myocardial protection.

Recent innovations in laser scanning technology provide a potentially useful tool for three-dimensional surface registration for image-guided surgery. The purpose of this study is to evaluate the clinical reliability of this technique in oral and maxillofacial surgical procedures using image-guided navigation.In an experimental step, a stable anthropomorphic skull model with prelabeled markers was scanned and registered with laser surface scanning (z-touch, BrainLAB) and marker- based algorithms. The registration protocol was then repeated 25-times. Root mean square error (RMSE) and target difference values were compared for their suitability for this application. Twelve patients with different indications for oral and maxillofacial surgery were planned for image-guided surgery using a passive infrared surgical navigation system (VectorVision, BrainLAB). Preoperative computed tomography (CT) scans were carried out with newest 16-line multisclice CT-scanner (Siemens Somatom Sensation 16). The new markerless laser surface scanning technique was applied in all intraoperative patient registrations. Registration error was noted. The clinical application accuracy was determined for anatomical landmark localization deviation.In the experimental protocol a mean registration error (RMSE) or target difference of 1.3 (0.14) or 2.08 (0.49) mm for laser scanning and 0.38 (0.01) or 0.99 (0.15) mm for marker registration was found. The differences for RMSE and target localization were statistically significant (p0.005). Furthermore, a strong correlation between RMSE and target difference was found for laser scanning (r = 0.96) and marker registration (r = 0.95). During various clinical procedures involving oral and maxillofacial surgery, the overall error of the registration procedure determined as RMSE was 1.21 (0.34) mm. Intraoperatively, the mean clinical application accuracy was found to be 1.8 (0.5) mm.Three-dimensional laser surface scanning technique may be a interesting and useful approach to register the patient for image-guided procedures, particularly during oral and craniomaxillofacial surgery.

Early detection of myocardial ischaemia is a central problem in cardiological and cardiosurgical intensive care. A new approach is the use of ion-selective electrodes implanted directly on the myocardium, enabling detection of increased potassium activity as an indication of general hypoxia. After a comprehensive study of the electrode parameters, an animal experiment was carried out, in which it was found that respiration-induced hypoxia resulted in an increase in epicardial potassium activity (p0.01). Blood gas analysis performed simultaneously revealed reduced arterial pO2, but no acidosis. Haemodynamic data evidenced hypoxic depression of circulatory parameters. Histological examinations of the myocardium beneath the electrodes revealed typical lymphocytic infiltration. Electron microscopy demonstrated crystolysis in the mitochondria as an early sign of hypoxia, thus confirming the sensitivity of these electrodes. This underscores the potential of ion-selective electrodes for the detection of myocardial ischaemia, and they should now be investigated in the clinical setting.

Advances in intra-operative imaging and the development of new minimally invasive techniques are having an ever greater impact on modern surgery. Mobile CT scanners in the operating room is a new technique that permits image-guided surgery, and helps minimize postoperative complications. We report on our initial experience with intraoperative CT scanning during surgery on patients suffering lateral midface trauma. A mobile CT unit, the Tomoscan M (Philips, Utrecht, Netherlands) set up in the operating room, was evaluated in 6 patients with zygomatic bone fractures. The patients were placed on the CT scanner table, which is detachable from the gantry. The unit is powered by batteries charged from an ordinary ring mains supply via a conventional plug. The CT images obtained were of good quality in all cases. No technical problems were observed during surgery. Using repeat CT scans, the procedure also permits accurate intraoperative monitoring of the anatomical repositioning of the bone fragments, and accurate implantation. No intraoperative or early postoperative complications were observed. This new technical aid ensures highly accurate reduction of the bone fragments, and minimizes the need for reoperation. High-quality intraoperative imaging with surgical navigation increase surgical outcome, and expand the spectrum of minimally invasive surgery.

Total circulatory arrest in deep hypothermia, which is used in corrective surgery of complex cardiovascular malformations, has been said to cause brain injury. Near-infrared spectroscopy (NIRS) is a new non-invasive method that potentially monitors changes in cerebral oxygenation and tissue oxygen utilisation. The aim of this experimental study in rabbits was to evaluate the change in intravascular and intracellular oxygenation patterns during cooling, deep hypothermic circulatory arrest and rewarming using a commercially available NIRS-cerebral oximeter.Ten New Zealand White male rabbits (weight, 3.1+/-0.25 kg BW) were included in this study. All animals underwent cardiopulmonary bypass (CPB), cooling to a rectal temperature below 15 degrees C, 60 min of deep hypothermic circulatory arrest (DHCA) followed by reperfusion and rewarming. Cerebral oxyhaemoglobin (HbO2), deoxyhaemoglobin (HHb) and cytochrome oxidase aa3 (CytOxaa3) concentrations were continuously measured during the entire procedure using the Cerebral RedOx Monitor 2020 (Criticon cerebral redox monitor 2020, JohnsonJohnson Medical). Total haemoglobin concentration (tHb) and regional cerebral oxygen saturation (rSO2) values were calculated by integrated algorithm.In all animals an initial increase of oxygenated haemoglobin (HbO2, rSO2) and a fall in deoxygenated haemoglobin (HHb) were found during cooling on bypass. A slight decrease in CytOxaa3 signal was observed in response to initial cooling. Variation in intravascular haemoglobin oxygenation parameters (HbO2, HHb) were related to haemodynamic changes associated with fluid loading, initiation and termination of CPB, bypass flow rate and cooling and rewarming. When the pump flow was stopped all NIRS parameters, except the HHb value, decreased precipitously during the DHCA-period (P0.01). After reperfusion and rewarming, all haemoglobin oxygen saturation readings returned nearly to pre-CPB levels (P=0.09), but the CytOxaa3 was still significantly lower than the pre-CPB levels (P0.05).The change in the NIRS-derived haemoglobin oxygenation parameters may reflect physiological changes in systemic and cerebral haemodynamics. CytOxaa3 values may represent related effects on cellular oxygenation. Thus, continuous, real-time NIRS-monitoring may identify critical periods with inadequate brain tissue oxygenation, particularly during DHCA. The neurological implications of the observed changes in NIRS oxygenation parameters, however, require further quantitative morphological evaluation of the brain in animals surviving a longer reperfusion and observation period.

Pulsewave velocity analysis is an option for the noninvasive determination of cardiac output and the evaluation of additional haemodynamic parameters. An algorithm we developed ourselves has been established as a method for the measurement of cardiac output in rabbits. The effectiveness of this program was investigated by monitoring controlled hypoxia-induced alterations in the circulatory system. Calculated values were compared with direct measurements of cardiac output with a Doppler flow probe placed in the ascending aorta. Within the physiological framework of blood gas analysis, a good correlation was found between the two methods. In the case of hypoxia-induced depression, however, the two methods showed diverging results, presumably due to arrhythmia-induced wave reflections within the arterial vascular tree. This makes an extension of the algorithm necessary to take account for these case.

Perioperative cardiac dysfunction may be related to inadequate myocardial protection during cardiopulmonary bypass (CPB) and associated procedures. Many intrinsic and extrinsic factors may act directly on vessels or indirectly by release of vasoactive metabolites to alter vascular tone and myocardial function during reperfusion. Milrinone, by inhibiting cAMP-specific phosphodiesterase enzymes in both cardiac and vascular smooth muscle, is a powerful inotrope and vasodilator, but has little effect on systemic arterial blood pressure. The purpose of the study was to investigate the effect of milrinone administration on recovery of left ventricular (LV) function and systemic haemodynamics after deep hypothermia and CPB in rabbits.

We investigated the capacity of heat stress to improve myocardial tolerance and cardiac energy metabolism in the isolated perfused neonatal rabbit heart subjected to prolonged cold cardioplegic ischemia.

Using a dual channel near infrared (NIR) in vivo optical spectroscopy (INVOS) system (INVOS 3100A, Somanetics Corp. Troy, MI, USA) we investigated the relationship between jugular venous oxygen saturation (SjvO2) and regional cerebral oxygen saturation (rSO2) in 30 infants and children (mean age 4.5 years) with congenital heart disease undergoing cardiac catheterisation. The NIRS-SomaSensor (emitter and dual receiver probe) was applied at a standardised right fronto-temporal location (over the right frontal cortex) on the infant's head and covered with an adhesive flexible bandage. Using NIR light (730 and 810 nm) and two source-detector spacings (3 and 4 cm from the transmitter), percentage values of rSO2 were calculated from detected haemoglobin saturations. Simultaneously, jugular venous oxygen saturation (SjvO2) monitoring was performed via a catheter placed in the right internal jugular vein with its tip positioned in the jugular bulb, as verified by fluoroscopy. To compare the reliability of NIRS measurement characteristics, jugular venous blood was analysed for SjvO2 as a reference measure of global cerebral oxygenation, by co-oximetry (OSM3-Hemoximeter, Radiometer Copenhagen, Denmark). Other measured variables included pulse oximetry, arterial blood pressure, and venous and arterial oxygen saturations. Over a jugular venous oxygen saturation range of 31-83%, a significant positive linear correlation was found between rSO2 (NIRS measurement) and SjvO2 (jugular bulb oximetry) (r = 0.93, p0.001). No significant correlation was observed between rSO2 values and arterial blood saturation or pulse oximetry. The quantitative correlation between rSO2 (haemoglobin oxygenation in a small hemi-elliptical area of the brain) and reference SjvO2 measurement (method for monitoring global cerebral oxygenation) suggests that NIRS measurement with subtraction algorithm should identify predominantly intracranial saturation in the pediatric age group, and will tend to reflect global oxygenation under physiological conditions. Transcranial oximetry using dual receiving channel NIRS offers a noninvasive, real-time, reliable and practicable means of monitoring cerebral haemoglobin oxygenation changes infants and children with cyanotic and noncyanotic congenital heart disease.

The aim of this study was to evaluate the relationship between the kinetic patterns of the protein S-100beta, an astroglial cell marker, and its immunohistochemical expression in the brain in rabbits that underwent cardiopulmonary bypass with deep hypothermic circulatory arrest. Fourteen New Zealand rabbits (weight, 3.1+/-0.25 kg) were anaesthetised, intubated and mechanically ventilated. Four animals were not connected to the cardiopulmonary bypass and served as controls. Ten animals were perfused according to a uniform protocol. After systemic cooling, deep hypothermic circulatory arrest was induced for 60 minutes. After reperfusion and rewarming, the animals were weaned from bypass and sacrificed. In the brain, astrocyte reactivity for S-100beta was evaluated immunocytochemically (DPC Immustain) and the serum concentrations of S-100beta were analysed using a commercially available immunoluminometric kit (Byk-Sangtec, Dietzenbach, Germany). In all experimental animals a significant increase of the serum concentration of the protein S-100beta was found immediately after reperfusion and the termination of cardiopulmonary bypass. In comparison with the control animals, increased staining of S-100beta was found in the astroglial cells and swollen astrocytic end-feet in the perivascular regions. There were fewer signs of neuronal cell injury of neurones in the hippocampus structure. In conclusion, astrocytic activation and S-100beta overexpression seems to precede the neurodegeneration following deep hypothermic circulatory arrest. The marked perivascular cell swelling may support the assumption of reperfusion injury of the astroglial cell complex that forms the blood-brain barrier, which may be indicative of the source of the released S-100beta into the blood stream.

Zur Antagonisierung des Heparins nach EKZ-Ende und Dekanulierung wird das alkalische Protein Protamin eingesetzt, wobei die initiale Menge des applizierten Heparins, bezogen auf das Korpergewicht oder die Korperoberflache des Patienten, zur Berechnung der erforderlichen Protamindosen dient. Die Antagonisierung mit Protamin erfolgt bei Standardprotokollen im Verhaltnis von 0,8–1:1 gegenuber der Heparindosis, und der Zielwert ist eine ACT

The present paper discusses an optimized model for describing central and peripheral pulse waves. On the basis of these computer-aided calculations, further haemodynamic data may be evaluated with the aim of improving the possibilities of clinically invasive diagnostic evaluation of cardiovascular diseases.

Currently, no reliable minimally invasive method of measuring cardiac output continuously in neonates and children undergoing cardiac surgery is available. An extravascular Doppler probe was used to measure cardiac output in 15 New Zealand White rabbits (average weight 3.5 kg, range 2.5-4.5 kg). The results obtained were compared with cardiac outputs determined using the aortic thermodilution principle. The mean cardiac outputs measured with the extravascular Doppler probe was 0.37 +/- 0.01 l/min as compared with 0.39 +/- 0.01 l/min with aortic thermodilution. Regression analysis revealed a close correlation (r = 0.973) between the two techniques. The extravascular Doppler techniques is an option for continuous and reliable cardiac output measurement in small animals used in surgical experiments (open chest models) and in neonates or children during surgical repair of complicated congenital heart conditions.

Early detection of myocardial ischaemia following cardiac surgery remains a central problem of intensive care medicine. On the basis of the observation in the epicardium that an elevated potassium activity accompanies myocardial ischaemia, a miniaturized electrode system for the measurement of epicardial potassium concentration was constructed and tested. Different types of electrode were implanted in two groups of rabbits. The electrode parameters were satisfactory (slope, screening) and it proved possible to record interference-free myocardial ion potentials, which with regard to the ionophores used is selective for potassium ion activity in the solid phase electrode. The system thus meets the prerequisites for further investigations into its suitability for early diagnosis of ischaemia.

Ischemic periods very often occur a dysfunction of the heart. In this series the intraoperative changes of potassium-activity and pH- value on the heart undergoing cardioplegic induced cardiac arrest were studied. Furthermore, the sensitivity of the system in diagnostic fields of ischemic periods and reperfusion damages were investigated.In eight patients (7 male and 1 female pts.) undergoing elective cardiosurgical procedures (aortocoronary bypass grafts) the ion activity of potassium and hydrogen ions were monitored on the heart, intraoperatively. By ion-selective electrodes the superficial cardiac ion activities were evaluated on definitive time periods on the left (LV) and right ventricle (RV).Preliminary results suggest: In the reperfusion-period different pH-values result on the ventricles. In the end of reperfusion the pH-values return to the starting points. Though the evaluated parameters are too alcaline in comparison to physiological intervals. The time course of epicardial potassium-concentrations is not different between the RV and LV. Initially, only low concentrations were found during perfusion and reperfusion, in the last interval of reperfusion period an increase of potassium on both ventricles were evaluated. In the end of the operations the superficial ion concentrations approximate to the values evaluated at the starting points.These results suggests, that the dynamics of ion-exchange-processes in the myocardium can be monitored with the help of ion-selective probes. This new technique opens new strategies in the qualitative check-up of myocardial protective procedures during cardioplegic cardiac arrest.

In this study, the possibility of total intravenous anaesthesia with the anaesthetic agents etomidat/fentanyl, ketamine/xylazine and maintenance with halothane, nitrous oxide and oxygen was used in rabbits for long-term experimental surgery with median sternotomy. The clinical course, cardiovascular and respiratory parameters undergoing long-term anaesthesia for experimental cardiac surgery in rabbits were evaluated.

The study was done in order to investigate the central nervous activities in rabbits (n = 10) during experimental surgery in ketamine and ketamine/midazolam-anaesthesia. The combination of a benzodiazepine with ketamine was thought to be beneficial to reduce the usual excitatory nervous effects after ket amine-anaesthesia. The results of the measured EEG-power spectra and somatosensory-evoked potentials were presented. Additionally, the central effects were correlated with mean arterial blood pressure and the results of blood gas analyzes.

The total removal of the myxoma under extracorporeal circulation from the origin maintains the optimal surgical treatment. Differentiation between myxoma and thromboses is a problem of preoperative diagnostics. Both tumors show unspecific symptoms. Therefore echocardiography and angiography are required as diagnostic tools. Between 1984 and 1991, 14 patients were cured from intracardiac tumors in the Clinic for Cardiovascular Surgery of the University of Leipzig. Problems in the sensitivity and security of the preoperative diagnostics and certain aspects of the surgical treatment will be discussed.