[Feedback control of depth of anesthesia during propofol administration. Bispectral index as the controlled variable]. / Regelkreisgesteuerte Narkosetiefe bei Propofolapplikation. Verwendung des Bispektralindex als Regelungsgrösse.

BACKGROUND: The objective of this study was to evaluate the performance of a new system for closed-loop control of propofol administration using the bispectral index (BIS) under total intravenous anesthesia in the index values of middle-to-deep depth of anaesthesia. METHODS: In this study 20 adult patients anesthetized with propofol and remifentanil were investigated. The propofol infusion was carried out using a fuzzy-PD+I controller with a target BIS value of 40. RESULTS: Closed-loop control was able to provide maintenance of anesthesia and adequate operating conditions for all patients. The following quality control criteria were calculated: median performance error (MDPE; 0.16%, SD +/-1.4%), median absolute performance error (MDAPE; 6.9%, SD +/-2.8%) and wobble (6.8%, SD +/-2.5%). CONCLUSION: The present study showed the clinical feasibility of the controller compared to existing devices regarding a high level of quality criteria of a model with an implemented fuzzy-PD+I structure controlling depth of hypnosis.

Xenon anesthesia impairs hepatic oxygenation and perfusion in healthy pigs.

BACKGROUND: Over the last 15 years, there has been growing interest in the noble gas xenon as a new inhalational anesthetic. This is due to its favorable pharmacological properties such as short onset and offset, as well as its hemodynamic stability. However, most volatile anesthetics appear to play an important role in the multi-factorial etiology of perioperative liver injury by decreasing liver blood flow with a subsequent reduction of hepatic oxygen supply. However, the effects of the anesthetic gas xenon on hepatic perfusion and oxygenation have not been completely investigated. METHODS: Following ethical approval, 18 anesthetized and acutely monitored pigs were randomly assigned to the two following groups: 9 animals received xenon anesthesia in increasing inspiratory concentrations of 0%, 20%, 50%, and 65% in addition to their basic intravenous anesthesia; 9 animals served as a control group. Measurement points for systemic and regional hemodynamic and oxygenation parameters were performed 30 min after changing the xenon concentration. RESULTS: Xenon elicited dose-dependent systemic hemodynamic changes such that the mean arterial pressure did not change, while the heart rate and cardiac output decreased by about 30%, thereby indicating an increase in the systemic vascular resistance. Portal venous blood flow decreased, while hepatic arterial blood flow was unchanged. The oxygen supply of the liver was reduced, but not the rate of indocyanine plasma disappearance from the liver. Furthermore, the increase of liver surface pO2 to systemic hyperoxia was absent, and hepatic lactate uptake was reduced. CONCLUSION: Xenon, in addition to basic intravenous anesthesia, elicited a decrease in heart rate and cardiac output and an increase in mean arterial pressure. Similar to volatile anesthetics, xenon does reduce portal venous flow and influences hepatic tissue oxygenation. In contrast, hepatic arterial blood flow remains stable in the presence of xenon, and no changes in the hepatic arterial buffer responses were evident. Xenon does affect hepatic perfusion and oxygenation.

Protective effects of PARP inhibition on liver microcirculation and function after haemorrhagic shock and resuscitation in male rats.

OBJECTIVE: The aim of this study was to investigate the impact of the water-soluble poly-(ADP)-ribose-polymerase (PARP) inhibitor 5-aminoisoquinolinone (5-AIQ) on liver microcirculation and function after haemorrhagic shock and resuscitation. DESIGN: Controlled, randomized animal study. SETTING: University animal care facility and research laboratory. SUBJECT: Male Sprague-Dawley rats were subjected to haemorrhagic shock for 1 h, followed by resuscitation with shed blood and crystalloid solution for a total of 5 h. INTERVENTIONS: The PARP inhibitor 5-AIQ (3 mg/kg; n=7) or vehicle (n=7) was administered 5 min prior to resuscitation. Sham-operated animals without induction of shock served as controls (n=7). MEASUREMENTS AND RESULTS: Using intravital fluorescence microscopy hepatic microcirculation was assessed at baseline, end of shock phase as well as 1 h and 5 h after resuscitation. Systemic arterial blood pressure and bile flow were continuously monitored. 5-AIQ treatment attenuated shock/resuscitation-induced increase of intrahepatic leukocyte-endothelial cell interaction with a marked reduction of both sinusoidal leukostasis and venular leukocyte adherence. Moreover, nutritive perfusion was found improved, guaranteeing sufficient oxygen supply to tissue, as indicated by low NADH autofluorescence, which was not different to that in controls. Most notably, excretory liver function reached baseline level over 5 h of reperfusion in 5-AIQ-treated animals. CONCLUSIONS: In the present setting of shock/resuscitation in male rats the PARP inhibitor 5-AIQ proved to be very effective in ameliorating compromised liver microcirculation and function. Further research has to confirm that PARP inhibition is a suitable tool in the acute treatment of patients suffering from reduced circulating blood volume and thus microcirculatory organ dysfunction.

Effects of systemically applied clonidine on intestinal perfusion and oxygenation in healthy pigs during general anaesthesia and laparotomy.

BACKGROUND AND OBJECTIVE: Clonidine, which is used for induction of sympatholysis and prevention or treatment of alcohol withdrawal in anaesthesia and intensive care medicine, may have deleterious effects on intestinal mucosal perfusion. This study was designed to investigate the effects of clonidine on intestinal perfusion and oxygenation. METHODS: Following ethical approval 17 anaesthetized, and acutely instrumented pigs were randomly assigned to two groups: eight animals received intravenous clonidine (2 microg kg(-1) bolus and 2 microg kg(-1) h(-1)), nine animals served as a control group. Measurement points for systemic and regional haemodynamic and oxygenation parameters were 135 and 315 min after starting the clonidine application. RESULTS: Clonidine elicited systemic haemodynamic changes (median [25-75th interquartile range]): heart rate (106 [91, 126] to 84 [71, 90] beats min(-1)) cardiac output (147 [123, 193] to 90 [87, 107] mL min(-1) kg(-1)) and mean arterial pressure (77 [72, 93] to 69 [61, 78] mmHg) decreased. Despite systemic haemodynamic changes, the superior mesenteric artery blood flow did not change in the clonidine group. The vascular resistance of the superior mesenteric artery decreased. The small intestinal oxygen supply, the mucosal and the serosal tissue oxygen partial pressure did not change. CONCLUSIONS: Systemic sympatholysis induced by intravenously applied clonidine in addition to basic intravenous anaesthesia elicited a decrease in cardiac output and mean arterial pressure. However, regional macrohaemodynamic perfusion was maintained and intestinal oxygenation did not change. Clonidine does not impair intestinal mucosal and serosal oxygenation under physiological conditions.

Impact of inspired substance concentrations on the results of breath analysis in mechanically ventilated patients.

A well-defined relationship has to exist between substance concentrations in blood and in breath if blood-borne volatile organic compounds (VOCs) are to be used as breath markers of disease or health. In this study, the impact of inspired substances on this relationship was investigated systematically. VOCs were determined in inspired and expired air and in arterial and mixed venous blood of 46 mechanically ventilated patients by means of SPME, GC/MS. Mean inspired concentrations were 25% of expired concentrations for pentane, 7.5% for acetone, 0.7% for isoprene and 0.4% for isoflurane. Only if inspired concentrations were <5% did substance disappearance rates from blood and exhalation rates correlate well. Exhaled substance concentrations depended on venous and inspired concentrations. Patients with sepsis had higher n-pentane and lower acetone concentrations in mixed venous blood than patients without sepsis (2.27 (0.37-8.70) versus 0.65 (0.33-1.48) nmol L-1 and 69 (22-99) versus 18 (6.7-56) micromol L-1). n-Pentane and acetone concentrations in breath showed no differences between the patient groups, regardless whether or not expired concentrations were corrected for inspired concentrations. In mechanically ventilated patients, concentration profiles of volatile substances in breath may considerably deviate from profiles in blood depending on the relative amount of inspired concentrations. A simple correction for inspired substance concentrations was not possible. Hence, substances having inspired concentrations>5% of expired concentrations should not be used as breath markers in these patients without knowledge of concentrations in blood and breath.

[Extracorporeal blood purification in severe liver failure with the albumin dialysis MARS -- impact on relevant intensive care parameters]. / Extrakorporale Blutreinigung im schweren Leberversagen mit der Albumindialyse MARS -- Einfluss auf intensivmedizinisch relevante Parameter.

Extracorporeal liver support methods have been tested for over 50 years now. Standard techniques of blood purification like dialysis, adsorption, hemo- and plasma filtration as well as bioreactor-based approaches using liver cells or tissues have been used. Most clinical experience, however, is limited to use in acute liver failure (ALF). Since 1993, the Molecular Adsorbent Recirculating System (MARS) has been used clinically -- a system that combines dialysis, filtration and adsorption in a biocompatible method. Human serum albumin (HSA) acts as a selective molecular adsorbent binding protein-bound compounds like bile acids or bilirubin. These substances can contribute to the maintenance or even further aggravation of liver failure. They are linked with the pathogenesis of hyperdynamic hypotonic circulation, hepatic encephalopathy, hepatorenal syndrome, impaired hepatic protein synthesis, and intractable pruritus seen in chronic liver failure. HSA takes over the toxic substances from a patient's blood and passes through a remote detoxification process including bicarbonate-dialysis and a two-step adsorption. It is then recirculated in the patient's blood. Up to today, more than 4000 patients have been treated in approximately 16,000 single sessions. Thus, MARS represents the most frequently used liver support method at the present time. In addition to ALF, mainly acute decompensations of chronic liver failures (ACLF) have been treated. The impact of the extracorporeal treatment on relevant medical parameters of intensive care medicine is discussed with regard to the specific situation of the liver-failure patient (susceptibility to infection, atypical picture and course of infection, coagulation disorders and bleeding tendencies).

Effects of xenon anaesthesia on intestinal oxygenation in acutely instrumented pigs.

BACKGROUND: Xenon is a narcotic gas that might be able to replace volatile anaesthetics or nitrous oxide due to its favourable pharmacological properties, such as providing haemodynamic stability. Intestinal oxygenation is affected by most volatile anaesthetics as a result of cardiodepressive effects. Reducing oxygenation of the gut might be a factor leading to perioperative organ dysfunction. This animal study was designed to assess the effects of xenon on intestinal oxygenation. METHODS: After ethical approval, 24 anaesthetized, acutely instrumented pigs were randomly assigned to three groups: nine animals received xenon anaesthesia with inspiratory concentrations of 0, 20, 50 and 65% in addition to their basic i.v. anaesthesia, nine animals served as a study control group, and five animals were used to assess model stability. Measurement of systemic and regional haemodynamic and oxygenation parameters was made 30 min after changing the xenon concentration. RESULTS: Xenon elicited dose-dependent systemic haemodynamic changes: heart rate and cardiac output decreased by 30%, while mean arterial pressure was stable. Superior mesenteric artery blood flow was lower in the xenon group. Vascular resistance of the superior mesenteric artery increased. The small intestinal oxygen supply decreased with increasing xenon concentration; the mucosal tissue oxygen partial pressure decreased but did not reach hypoxic (<5 mm Hg) values. Serosal tissue oxygen partial pressure was maintained. CONCLUSIONS: Xenon, in addition to basic i.v. anaesthesia, elicited a decrease in cardiac output and maintained mean arterial pressure. Intestinal oxygenation was maintained, although regional macrohaemodynamic perfusion decreased. Xenon does not impair intestinal oxygenation under physiological conditions.

[Remifentanil analgesia for aspiration of follicles for oocyte retrieval]. / Remifentanil-Analgezien zur Follikelpunktion für In-Vitro-Fertilisation.

Remifentanil is an esterase-metabolized ultra-short acting mu-agonist opioid with a rapid clearance. The aim of this study was to determine the efficacy of remifentanil infusion for the short-lasting, but painful, transvaginal puncture for oocyte retrieval. Eighty consenting adult women (ASA I and II) aged 30.5 +/- 5 years and with a body weight of 69.1 +/- 9.1 kg were enrolled in this prospective study. After an oral premedication with 7.5 mg midazolam, all patients received 3 l/min oxygen. Subsequently, the remifentanil infusion was started with a rate of 0.3 microg/kg/min. Remifenanil doses were adjusted as needed for painless puncture and sufficient oxygen saturation in steps of 0.05 microg/kg/min. Dosage requirements, blood pressure, heart rate, oxygen saturation (pulse oxymetry, SaO2) and the level of analgesia were recorded every 3 minutes. Follicular aspiration lasted 11.8 +/- 4.1 min and the time of remifentanil infusion was 18.7 +/- 4.6 min. Dosage requirements of remifentanil were 0.3 microg/kg/min in 48.7% of all patients, but 27.8% needed only 0.25 microg/kg/min and 16.6% needed only 0.2 microg/kg/min. However, 4.2% of patients needed 0.35 microg/kg/min and 2.7% of all cases needed 0.4 microg/kg/min. Vital parameters remained nearly unchanged. Oxygen saturation decreased significantly from 99.2 +/- 0.7% to 98.2 +/- 2.4% after 3 min and to 94.9 +/- 7.2% after 10 min. Nine women showed motoric reactions to puncture. In many cases, the infusion of remifentanil after premedication with midazolam provided a suitable and satisfying anaesthesia for oocyte retrieval. Some patients, however, showed motoric reactions to vaginal puncture, while in other cases significant and clinical relevant decreases in Hb-oxygen saturation occurred. Therefore, we no longer carry out remifentanil infusion for transvaginal oocyte retrieval. We now prefer a remifentanil infusion of 0.2 microg/kg/min and propofol (1 mg/kg initially with intermittent doses of 0.5 mg/kg) combined with assisted ventilation by mask.

[Cricoid pressure--safety necessity or unnecessary risk?]. / Krikoid-Druck--Sicherheitsnotwendigkeit oder unnötiges Sicherheitsrisiko?

Cricoid pressure is a simple and effective measure to prevent regurgitation of gastric juice and content. This procedure, which prevents a possible reflux by compression of the oesophagus between the cricoid cartilage and the cervical vertebral bodies, is generally acknowledged in clinical practice, although there is lack of scientific evidence regarding its effect on the outcome of patients at risk of aspiration. However, there is only a rare incidence of complications as long as cricoid pressure is used with exact indication, considering the contraindications and correct performance. Especially important are the optimal force applied on the cricoid and the duration of application. However, there is a lot of evidence in the literature that the knowledge of anaesthetists about the method and technique of cricoid pressure is rather unsatisfactory. Thus, the starting point for improving the efficiency and safety of cricoid pressure seems to be better teaching and training.

[Alcohol--a perioperative problem of anaesthesia and intensive care medicine]. / Alkohol als perioperatives Problem in Anästhesiologie und Intensivmedizin.

Alcohol is a socially tolerated drug. Its consumption is associated with several physiological and pharmacological negative side-effects during anaesthesia and intensive care. The impact of chronic and acute alcoholism on perioperative morbidity and mortality and especially on anaesthetic risk are important, due to pharmacological interactions, pathophysiological changes and direct pharmacological interactivities between alcohol and narcotics. In contrast to opioid withdrawal symptoms of alcohol withdrawal are a serious and potentially life-threatening complication and should be avoided or the risk for occurrence must at least be reduced. Patients with a high risk of developing perioperative symptoms of alcohol withdrawal can be detected by laboratory tests and questionnaires. A prophylaxis of withdrawal should be started preoperatively solely with benzodiazepines or in combination with clonidine. Haloperidol is the drug of choice for emerging symptoms of alcohol withdrawal with productive psychosis. To estimate the pharmacological changes during anaesthesia, it is necessary to differentiate whether the patient is an occasional drinker with acute intoxication, a chronic abuser without limitations of hepatic function or a chronic user with insufficiency of the liver. The most important implication for anaesthesia are the choice of a rapid sequence induction to reduce the risk of aspiration and the maintenance of haemodynamic stability and liver perfusion. For the acute alcoholic providing prolonged postoperative surveillance is necessary, for the chronic alcoholic intensive care seems to be mandatory. For regional anaesthesia the indications and limitations are the same as for other patients (cooperativeness, coagulation, consent, etc.).

[Smoking and preoperative fasting--are there evidence-based guidelines?]. / Rauchen und präoperative Nüchternheit--Was ist belegt?

Over the last years several clinical studies have modified the guidelines for preoperative fasting to reduce the risk of pulmonary aspiration. In most western countries the following guidelines are accepted: for clear liquids 2 hours, breast feeding 4 hours, small meals and breast milk substitutes 6 hours, heavy meals 8 hours. Since preoperative smoking is acknowledged as a risk factor, it should be ceased in most clinics 6 hours before induction of anaesthesia, as well. Smoking, however, does not increase the risk of pulmonary aspiration, as is often maintained, but increases the risk of postoperative pulmonary complications. To reduce the risk of perioperative pulmonary complications, cessation of smoking is necessary 8 weeks before operation. Stopping smoking only a few days before operation and anaesthesia even tends to increase the risk of pulmonary complications. Regarding cardiac complications, cessation of smoking 12 hours before anaesthesia is sufficient to reduce the incidence of cardiac ischaemia.

[Perioperative management of a patient with Sneddon syndrome--a case report]. / Perioperatives Management bei Patientin mit Sneddon-Syndrom--Eine Kasuistik.

Sneddon's syndrome is a rare combination of generalised livedo reticularis and cerebrovascular accidents. Its clinical presentation varies widely and its aetiology is still not known. 60 to 80% of patients are female. First symptoms of the syndrome are mostly repetitive cerebral strokes, but reduced perfusion of the skin, seen as blue or red-brown mottling, precedes the strokes. The vascular disease is generalised and often accompanied by arteriosclerosis, systemic arterial hypertension, valvular heart disease and the presence of antiphospholipid antibodies. The diagnostic procedures are complicated and have to exclude other autoimmunological diseases. Therapeutic options are anticoagulatory therapy with warfarin, ASS or heparin, reduction of endothelial proliferation with ACE-inhibitors, and improvement of microvascular perfusion with prostaglandine. The increased anaesthesiological risk with these patients is due to the acute risk of thromboembolism and ischaemic cerebral and cardiovascular insults. The anaesthetic management must provide stable perfusion pressures for cerebral and myocardial arteries and avoid increasing risk factors for thromboembolism such as increased blood viscosity or stasis due to improper positioning of the patient. The choice of anaesthetic drugs is dependent on good controllability for haemodynamic stability. The high risk of patients with Sneddon's syndrome justifies a more invasive haemodynamic monitoring and postoperative surveillance on an intensive care unit. This case report describes the anaesthesiological considerations for, and management of, a patient with Sneddon's syndrome who was admitted to hospital for vaginal hysterectomy.

Effects of epidural anaesthesia on intestinal oxygenation in pigs.

BACKGROUND: Perioperative intestinal hypoperfusion is a major contributing factor leading to organ dysfunction. It can be caused by stress as a result of surgical manipulation or hypoxia. Additionally, anaesthesia can affect intestinal oxygenation. This animal study was designed to assess the effects of reduced regional sympathetic nervous activity induced by thoracic epidural anaesthesia on intestinal oxygenation. METHODS: After ethical approval, 16 anaesthetized and acutely instrumented pigs were randomly assigned to two groups (epidural anaesthesia alone vs epidural anaesthesia plus volume loading). The epidural anaesthesia aimed for a T5-T12 block. Measurements were at baseline and after 1 and 2 h. RESULTS: Epidural anaesthesia was associated with a decrease in mean arterial blood pressure and pronounced mesenteric vasodilatation. Mesenteric blood flow did not change. Intestinal oxygen uptake, mucosal tissue oxygen partial pressure and tissue carbon dioxide partial pressure remained unchanged. CONCLUSIONS: Despite marked systemic hypotension, epidural anaesthesia did not affect intestinal oxygenation. There was no benefit obtained from volume loading.

[Managing anesthesia in the alcoholic patient]. / Narkoseführung beim Alkoholiker.

In most developed countries, alcohol is a socially tolerated drug. Nevertheless, its consumption is associated with several negative side-effects during anaesthesia. In surgical patients the prevalence of alcoholism exceeds 20%. Chronic alcoholism and acute alcoholism have an important impact on perioperative morbidity and mortality and especially on anaesthetic risk, due to pharmacological interactions, pathophysiological changes and direct pharmacological interactivities between alcohol and narcotics. Symptoms of alcohol withdrawal are a serious and potentially life-threatening complication and should be avoided or the risk for occurrence should at least be reduced. Patients with a high risk of developing perioperative symptoms of alcohol withdrawal can be detected by laboratory tests and questionnaires. The most important implication for anaesthesia is the choice of a rapid sequence induction to reduce the risk of aspiration and the maintenance of haemodynamic stability and liver perfusion. Maintaining body temperature and providing intensive postoperative surveillance and care are necessary. The indications for regional anaesthesia are the same as for other patients (cooperativeness, coagulation, consent, etc.). In general, awareness of possible interactions can reduce perioperative complications and improve postoperative outcome.

[Can the limits of intensive care management be defined?]. / Lassen sich Grenzen intensivtherapeutischen Handelns festlegen?

Medical treatment requires more than the application of techniques and devices. Knowing the limitations of (intensive) care and respecting patients' will and dignity is as important as technical skills. Limitations of therapy may arise from medical, ethical, legal, and economic reasons. Therapy may be limited through a Do-Not-Resuscitate (DNR) order, or by withholding or withdrawal of treatment. Total withdrawal of treatment ensues from proven brain death when organ donation has been denied or has been accomplished. But legislation as well as ethics and medical science fail to define unequivocal and precise criteria for limitation of treatment. Depending on the kind of disease, its prognosis and the patient's individual situation clinical scenarios can be identified when withholding or withdrawal of treatment may be thought of. The patient's expressed or anticipated wishes play a key role in decision-making on limitation of treatment. If the patient has no more decision making capacities physicians and patient's next of kin have to determine what would be in the patient's best interest. The patient and/or his family, all attending physicians and the nursing staff have to agree when limitation of care is taken into account. Hospital guidelines and written orders will help physicians and nursing staff to manage these difficult situations. Whether treatment has been limited or not, the patient and his family deserve all our medical and psychological skills--until the end.

[Hemodynamic monitoring of splanchnic circulation--does the benefit outweight risk of of regional circulation monitoring?]. / Hämodynamisches Monitoring des Splanchnikusgebietes--Uberwiegt der Nutzen das Risiko des teilkreislaufbezogenen Monitorings?

Over the last 20 years there has been increasing interest in the pivotal role of the splanchnic region in the development of SIRS, sepsis and multiple organ failure. One key question is how to monitor and detect in good time regional splanchnic perfusion, oxygenation and impaired function of liver and gut, so as to start appropriate therapeutic measures. This review describes the pathophysiological background of impaired splanchnic perfusion. It focuses on the advantages and risks of methods of monitoring splanchnic perfusion or oxygenation and considers them regarding clinical relevance and usefulness. Special emphasis is laid on gastric tonometry. Despite all the restrictions and the criticism which can be levelled at this method, it remains the only way of monitoring splanchnic perfusion and oxygenation that is currently applicable in clinical routine. The data gained can be useful if clinicians are aware of the weak points of tonometry and consider the data in the overall clinical picture. When this is done, the patient can profit from gastric tonometry and the benefits outweigh the risks.

Regulation of hepatic blood flow during resuscitation from hemorrhagic shock: role of NO and endothelins.

We determined the role of nitric oxide (NO) and endothelins (ETs) in the regulation of hepatic blood flow during resuscitation from hemorrhagic shock (HS) in anesthetized rats. Volume resuscitation restored systemic hemodynamics and increased hepatic arterial and portal venous flow above baseline in the vehicle group. Presence of N omega-nitro-L-arginine methyl ester (L-NAME, 1 mg/kg) during resuscitation increased systemic vascular resistance (SVR) above baseline, prevented the restoration of hepatic arterial flow, and abolished portal hyperemia. Although the ETA+B-receptor antagonist bosentan (10 mg/kg) did not alter the systemic hemodynamic response, it abolished the hepatic arterial and portal hyperemia. The ETA-receptor antagonist BQ-610 (150 micrograms/kg) reduced SVR below baseline, allowed hepatic arterial hyperemia to occur, and further enhanced the portal venous hyperemia. This indicates that 1) NO reduces SVR and acts to preserve hepatic blood flow during resuscitation from HS; 2) ETA-receptor-mediated vasoconstriction counteracts the systemic and portal hemodynamic effects of NO; and 3) simultaneous ETB-receptor stimulation enhances blood flow to the liver and may serve to modulate the ETA-receptor-mediated vasoconstrictive effects of ETs.

The effects of desflurane on splanchnic hemodynamics and oxygenation in the anesthetized pig.

This study was designed to investigate the effects of desflurane on systemic and splanchnic hemodynamics, O2 delivery and O2 uptake, tissue oxygenation (as monitored by surface PO2 electrodes), and hepatic oxygen-dependent intermediary metabolism (hepatic lactate uptake, intestinal lactate production, ketone-body ratio) in the pig. We studied 11 anesthetized (i.e., ketamine, flunitrazepam, vecuronium) and ventilated domestic pigs (17-23 kg). After instrumentation, desflurane was administered randomly at 0.5 minimum alveolar anesthetic concentration (MAC) (4.2 vol %) and 1.0 MAC (8.3 vol %). Desflurane caused dose-dependent decreases in heart rate, mean arterial blood pressure, and cardiac output. Hepatic arterial blood flow was not affected at 0.5 MAC but decreased at 1.0 MAC. In contrast, portal and superior mesenteric arterial blood flow decreased at 0.5 MAC but did not show any further significant decrease at 1.0 MAC. Total hepatic blood flow decreased dose-dependently. Although O2 deliveries of whole body, liver, and small intestine were markedly reduced at both concentrations, respective O2 uptakes did not change significantly. The decreases in O2 deliveries were reflected by moderate disturbances in hepatic and small intestinal surface PO2. No evidence for severe tissue hypoxia could be detected. Desflurane had no adverse effects on hepatic and small intestinal metabolic function. These data indicate that hepatic and small intestinal O2 reserve capacity is impaired by desflurane.

Different effects of early endotoxaemia on hepatic and small intestinal oxygenation in pigs.

OBJECTIVE: Study on simultaneous O2 supply/uptake relationships in liver and gut during endotoxaemia, to determine whether signs of dysoxia develop uniformly in the splanchnic region. DESIGN: Animal study to assess the early effects of endotoxaemia on oxygenation of both liver and small intestine. INTERVENTIONS: Eight anaesthetized pigs received a continuous portal venous infusion of lipopolysaccharide (0.5 microgram.kg-1.h-1) for 6 h. Systemic, pulmonary and splanchnic haemodynamics as well as systemic and splanchnic O2 supply/uptake relationships were determined. RESULTS: There was a multiphasic haemodynamic response pattern characterized by an early (within the 1st h) and a subsequent more prolonged phase (between the 2nd and 6th h) of decreases and recovery of hepatic arterial, portal venous and superior mesenteric arterial blood flows (electromagnetic flow probes) and splanchnic O2 deliveries. Unrelated to perfusion pressure and O2 delivery, there were early and sustained decreases in ileal mucosal surface partial pressure of oxygen (PO2) (multiwire PO2 electrode) and pH (tonometry). This was not reflected by ileal serosal surface PO2, O2 uptake and arteriomesenteric venous pH and partial pressure of carbon dioxide (PCO2) gradients. There was little evidence of concomitant hepatic dysoxia as evaluated by surface PO2. CONCLUSIONS: The study demonstrates early and sustained regional (mucosa) intestinal hypoxia with little evidence of simultaneous hepatic dysoxia during initial endotoxaemia.