Tissue oxygenation during liver transplantation

Surgical Science and the Evolution of Critical Care Medicine

Surgical science has driven innovation and inquiry across adult and pediatric disciplines that provide critical care regardless of location. Surgically originated but broadly applicable knowledge has been globally shared within the pages Critical Care Medicine over the last 50 years.

A comparison of intra-operative blood loss and acid-base balance between vasopressor and inotrope strategy during living donor liver transplantation: a randomised, controlled study

Administration of vasopressors or inotropes during liver transplant surgery is almost universal, as this procedure is often accompanied by massive haemorrhage, acid-base imbalance, and cardiovascular instability. However, the actual agents that should be used and the choice between a vasopressor and an inotrope strategy are not clear from existing published evidence. In this prospective, randomised, controlled and single-blinded study, we compared the effects of a vasopressor strategy on intra-operative blood loss and acid-base status with those of an inotrope strategy during living donor liver transplantation. Seventy-six adult liver recipients with decompensated cirrhosis were randomly assigned to receive a continuous infusion of either phenylephrine at a dose of 0.3-0.4 μg.kg(-1).min(-1) or dopamine and/or dobutamine at 2-8 μg.kg(-1).min(-1) during surgery. Vascular resistance was higher over time in the phenylephrine group than in the dopamine/dobutamine group. Estimated blood loss was significantly lower in the phenylephrine group than in the dopamine/dobutamine group (mean (SD) 4.5 (1.8) l vs 6.1 (3.4) l, respectively, p=0.011). Patients in the phenylephrine group had lower lactate levels in the late pre-anhepatic and the early anhepatic phase and needed less bicarbonate administration than those in the dopamine/dobutamine group (median (IQR [range]) 40 (0-100 [0-160]) mEq vs 70 (40-163 [0-260]) mEq, respectively, p=0.018). Postoperative clinical outcomes and laboratory-measured hepatic and renal function did not differ between the groups. Increased vascular resistance and reduction of portal blood flow by intra-operative phenylephrine infusion is assumed to decrease the amount of intra-operative bleeding and thereby ameliorate the progression of lactic acidosis during liver transplant surgery.

Dichloroacetate stabilizes the intraoperative acid-base balance during liver transplantation

Lactic acidosis occurs during orthotopic liver transplantation (OLT), especially during the anhepatic and early postreperfusion phases. Dichloroacetate (DCA) inhibits pyruvate dehydrogenase kinase-1, indirectly activating mitochondrial pyruvate dehydrogenase. This, in turn, markedly reduces systemic lactate production and, to a lesser extent, increases hepatic lactate uptake. The result is moderation of lactic acidosis in many clinical conditions. This study evaluated the efficacy of DCA in controlling lactic acidosis during OLT and improving perioperative outcome from OLT. After informed consent, 250 patients for OLT received either intraoperative DCA or placebo. DCA (40 mg/kg intravenously) or placebo was administered after anesthesia induction and repeated 4 hours later. Intraoperative measures were arterial blood gases, lactate, and Na+ and utilization of blood products, CaCl2, and NaHCO3. Outcome measures were time to tracheal extubation, intensive care unit length of stay, hospital length of stay, requirement for postoperative plasma transfusion, retransplantation, and perioperative mortality. DCA reduced the arterial lactic acid concentration by an average of 44% (1.8 mmol L(-1), P < 0.001), stabilized the acid-base balance, and reduced NaHCO(3) administration by 80% (P < 0.001). Postoperatively, DCA-treated patients required 50% less postoperative plasma transfusion (2 versus 4 units, respectively, P = 0.016), but the incidence of transfusion was similar in both groups (62% versus 60%, P = 0.381). DCA did not alter time to extubation, intensive care unit length of stay, or hospital length of stay. In conclusion, DCA attenuated lactic acidosis during OLT, stabilizing the intraoperative acid-base balance and decreasing NaHCO3 use. DCA decreased postoperative plasma transfusion requirement but otherwise had no measurable effect on perioperative outcome parameters.

Changes in oxyhemoglobin dissociation curve in intrabdominal organs during pig experimental orthotopic liver transplantation

Liver transplantation has become a gold standard treatment for irreversible liver disease. Conventional measures of oxygenation are inadequate to understand the dynamics of regional oxygen metabolism during liver transplantation because they represent global markers of tissue dysoxia. Therefore, the addition of an assessment of the hemoglobin O(2) binding capacity can give a better insight into systemic and regional tissue oxygenation and can reflect a more accurate estimation of oxygen release to the tissues than can the hemoglobin, the PaO(2) and SaO(2) alone. This prospective study was designed to evaluate possible alterations in the oxyhemoglobin dissociation curve of vital end organs (small bowel, liver, and kidney) in an experimental liver transplantation model. Fifteen pigs with body weights ranging from 25 to 30 kg were used for the study. Five healthy pigs underwent a sham operation under general anesthesia (group A-control). Ten pigs underwent orthotopic liver transplantation (OLT). Five of them were healthy (group B), whereas the other five were in acute liver failure, which had been surgically induced (group C). Systemic arterial blood pressure, cardiac index, and pulmonary and systemic vascular resistance indexes were measured. Venous blood gas analysis was also performed from pulmonary artery, superior mesenteric, hepatic, and renal veins at well-defined timepoints during the course of the OLT. A statistically significant (P < 0.05) decrease of P(50) in groups B and C compared with group A was observed 30 minutes after reperfusion in the systemic circulation, hepatic, and renal veins. This coincided with a decrease in animal temperature 30 minutes after reperfusion. Regarding group C, after reperfusion of the newly transplanted liver there was a significant increase of P(50) in the small bowel in comparison to baseline values. In conclusion, these changes in P(50) may suggest the occurrence of abnormal tissue oxygenation after reperfusion.

Oxygen availability during orthotopic liver transplantation

Studies have stressed the role of adequate tissue oxygenation in the light of an optimal patient outcome and allograft viability in liver transplantation. The practice of monitoring conventional hemodynamic parameters during liver transplantation could be complemented by parameters assessing real oxygen availability. In the present prospective study, real arterial available oxygen content (CavlO(2)) and its extraction ratio (O(2)ERavl) were calculated. These parameters include the effect of changes in oxyhemoglobin dissociation curve (ODC; expressed by P(50)) on oxygen availability, under the different circumstances occurring during liver transplantation. Sixteen adult cirrhotic patients were studied during orthotopic liver transplantation with the use of venovenous bypass. Classic hemodynamic measurements using a Swan-Ganz thermodilution catheter and arterial and mixed venous blood gas analysis were performed, and P(50), oxygen delivery index (DO(2 ind)), oxygen consumption index (VO(2 ind)), oxygen extraction ratio (O(2)ER), CavlO(2), and O(2)ERavl were calculated. Statistical analysis was performed using ANOVA for repeated measures and Spearman correlation coefficient matrix among the six variables (DO(2 ind), VO(2 ind), O(2)ER, P(50), CavlO(2), and O(2)ERavl) taken two at a time at every phase. Parameter P(50) changed from 25.98 +/- 1.10 to 23.15 +/- 2.24 (at the end of operation). A leftward shift of the ODC was observed. The results showed positive association between P(50) and CavlO(2) after the removal of the native liver, and a weak and inconsistent relation of DO(2 ind) with any of the other study variables. The intraoperative changes in P(50) values, which represent a shift of the ODC to the left, may reflect a more accurate estimation of O(2) release to the tissues, than the hemoglobin, Pao(2) and Sao(2) alone. Besides conventional hemodynamic parameters, P(50), which includes the effect of alterations in ODC on oxygen availability, could be of value in monitoring the systemic oxygenation during liver transplantation.

The effect of venovenous bypass on lactic acid levels during human liver transplantation (OLT)

Lactate determinations did not contribute to the quantification of the systemic and regional tissue oxygenation during OLT. Venous stasis was not an important factor in the tissue imbalance between oxygen supply and oxygen demand.

Hepatic and splanchnic oxygenation during liver transplantation

OBJECTIVE

To evaluate hepatic and splanchnic oxygenation during liver transplantation.

DESIGN

Prospective study.

SETTING

University hospital.

PATIENTS

Ten adult patients undergoing liver transplantation.

INTERVENTIONS

Standardized surgery and anesthesia without venovenous bypass.

MEASUREMENTS AND MAIN RESULTS

Hepatic oxygenation was assessed by analyzing oxygen tension, oxygen saturation, and lactate concentration in hepatic venous blood. Splanchnic oxygenation was assessed by analyzing oxygen tension, oxygen saturation, and lactate concentration in portal venous blood and by gastric tonometry. Before reperfusion, the grafts were flushed with 1000 mL of acetated Ringer's solution and 400 mL of portal venous blood. The effluent blood from the graft was wasted and showed a mean pH of 6.86 and a lactate concentration of 9.4 mmol/L. Five minutes after portal reperfusion, most of the grafts produced lactate. Portal-hepatic venous P(CO2) difference ranged from 3 to 16 torr (0.4-2.1 kPa). By the time of restoration of the infrahepatic caval flow mean 24 mins later, eight of the grafts had stopped producing lactate. Mean hepatic venous oxygen tension was 47 torr (6.3 kPa), stabilizing to 41 torr (5.5 kPa) at the end of surgery. Acidosis resolved without pharmacologic interventions. Mean gastric mucosal pH was 7.29 during the anhepatic phase and 7.40 at the end of surgery. One of the patients developed hepatic arterial thrombosis intraoperatively. Her data were analyzed separately. Later, the other patients recovered with good liver function, whereas the patient with hepatic arterial thrombosis was successfully retransplanted.

CONCLUSIONS

The liver grafts received well-oxygenated portal venous blood during reperfusion, despite the low values of gastric mucosal pH immediately before reperfusion. Hepatic oxygenation became adequate soon after reperfusion. In the patient with hepatic arterial thrombosis, the recovery of hepatic oxygenation was impaired and lactic acidosis persisted.

Oxygen consumption, lactate metabolism, and gastric intramucosal pH in an experimental liver transplantation model

OBJECTIVE

To assess the usefulness of measuring whole-body oxygen consumption (VO2), arterial lactate concentration, and gastric intramucosal pH (pHi) as parameters for evaluating hepatic graft viability in a model of experimental liver transplantation.

DESIGN

Experimental, prospective study.

SETTING

Hospital laboratory for experimental surgery.

SUBJECTS

Twenty-eight Landrace-Largewhite pigs: 14 donors and 14 recipients.

INTERVENTIONS

Orthotopic liver transplantation. Two groups were differentiated by graft preservation status: an optimal-graft group (group 1), which received donor livers that had been preserved in Collins solution at 4 degrees C for <4 hrs (n = 7), and an injured-graft group (group 2), which received donor livers that had been preserved in Collins solution at 4 degrees C for >24 hrs (n = 7).

MEASUREMENTS AND MAIN RESULTS

Hemodynamic parameters, variables related with systemic and hepatic oxygen and lactate metabolism, gastric pHi, and arterial pH were measured at two stages: a) preanhepatic stage; and b) neohepatic stage (60 mins after reperfusion). There were no differences in VO2 between graft groups or stages. In the neohepatic stage, hepatic oxygen extraction and lactate turnover were significantly higher in the optimal-graft group than in the injured-graft group. In the neohepatic stage, gastric pHi decreased significantly and arterial lactate concentrations increased significantly in both groups.

CONCLUSIONS

Changes in hepatic VO2 cannot be detected by VO2 measurements. Optimal-state grafts increased their lactate turnover as a result of substrate overload, but injured grafts did not. Therefore, the evolution of arterial lactate concentrations in the immediate postoperative period may be useful for the early evaluation of transplanted livers. Gastric pHi can be a useful measurement in the immediate posttransplantation period for differentiating between hyperlactacidemia produced by liver dysfunction (normal pHi) and hyperlactacidemia produced by lactate generation as a consequence of inadequate tissue oxygenation or of a mixed origin (abnormal pHi).

Does N-acetylcysteine improve hemodynamics and graft function in liver transplantation?

The release of toxic oxidative free radicals induced by ischemia and reperfusion may jeopardize liver graft function. N-acetylcysteine (NAC) has shown protective effects on hypothermic and warm ischemia reperfusion liver injury in animals. NAC improves hemodynamics and survival rates in patients with fulminant hepatic failure. The aim of this study was to investigate whether intraoperative treatment with NAC would improve hemodynamics and postoperative graft function in liver transplantation. Sixty patients with chronic end-stage liver disease were included in a prospective randomized placebo-controlled study. NAC or the same volume of 5% glucose was started during the anhepatic phase. Hemodynamic data and calculated tissue oxygenation parameters were compared throughout the procedure. Postoperative graft function was assessed by measurements of aminotransferases, prothrombin time, and monoethylglycinexylidide test over the 3 first postoperative days. Patient demographics were similar before the infusion of NAC or glucose. Hemodynamic parameters, oxygen consumption, oxygen delivery, oxygen extraction ratio, and lactates were not different throughout the procedure. One hour after the revascularization of the hepatic artery, the oxygen extraction ratio by the liver was similar (17% +/- 7.6% v 17% +/- 6.2%) in both groups. Postoperative graft function was comparable within the 3 first postoperative days. This study failed to show any beneficial effect of the intraoperative administration of NAC on hemodynamics and graft function in liver transplantation in patients with chronic liver disease.

Oxygen metabolism during liver transplantation: the effect of dichloroacetate

Dichloroacetate (DCA) stimulates pyruvate dehydrogenase (PDH), accelerating recovery of the postischemic heart. Because DCA also stimulates hepatic PDH, it may facilitate graft recovery during liver transplantation (OLT). Hepatic removal and replacement during OLT produce major changes in O2 consumption (VO2), and return of baseline VO2 has been used to index early graft function. We examined the effect of DCA on O2 metabolism during OLT. Forty patients received DCA 80 mg/kg intravenously in divided doses, and 40 served as controls. Serial measurements were made for body temperature, hemodynamics, O2 metabolic indices, and plasma substrate and hormonal concentrations. Oxygen delivery (DO2I) and consumption (VO2I) indices were calculated. Patients exhibited stable hemodynamics, with similar fluid and blood product requirements. Compared with the dissection stage, DO2I and VO2I were decreased during the anhepatic stage (31% and 36%, respectively), then returned to dissection stage values soon after portal vein unclamping. Temperature decreased during the anhepatic stage and returned toward dissection stage value after graft perfusion. DCA reduced lactic acidosis and NaHCO3 use but did not alter hemodynamics or measures of O2 metabolism or body temperature. VO2 is decreased during the anhepatic stage largely due to loss of hepatic metabolism. Restoration of VO2 by 30 min after portal vein unclamping reflects rapid recovery of O2 metabolism by the graft liver, but DCA does not accelerate recovery of VO2. DCA does not seem to facilitate early graft hepatic function as indexed by VO2.

IMPLICATIONS

We evaluated whether dichloroacetate, which stimulates pyruvate dehydrogenase, can accelerate recovery of graft liver hepatic function during liver transplantation, as indexed by oxygen consumption. We found that despite evidence that it activated pyruvate dehydrogenase, dichloroacetate did not affect recovery of transplanted liver function.

Lactate blood levels in the perioperative period of orthotopic liver transplantation

To investigate whether early postoperative changes in blood lactate concentration indicate the functional recovery of the newly grafted liver, changes in oxygen supply, oxygen consumption, acid-base equilibrium, and blood lactate concentrations were prospectively studied in a group of 53 postnecrotic cirrhotic patients during the various phases of orthotopic liver transplantation (preanhepatic, anhepatic, neohepatic) and for the first 48 h following reperfusion. The patients were divided into two groups according to the quality of the early graft function, as indicated by alanine aminotransferase, bile flow, and prothrombin activity: group A (49 patients), good immediate graft function and group B (4 patients), immediate graft non-function. Lactate levels rose in the same manner during the preanhepatic and anhepatic stages and peaked after revascularization of the graft. Following reperfusion, however, distinctly different blood lactate profiles were recorded in the two groups of patients. A fall in lactate concentration was recorded in group A patients, whereas a continuous rise occurred in group B patients: the difference becoming significant by the end of surgery (P < or = 0.05). During the first 48 h following revascularization of the graft, opposite trends in lactate concentration, bile flow, alanine aminotransferase, and prothrombin activity were evident in the two groups of patients: 24 h after reperfusion, lactate levels were below 2 mmol/l in 47 of 49 patients from group A, while they plateaued above 4 mmol/l in all patients from group B. Group A patients had lower alanine aminotransferase levels (P < or = 0.001), higher prothrombin activity, (P < or = 0.01), and greater bile flow (P < or = 0.02). If validated in larger series, the blood lactate profile, probably more than the absolute level, appears to be a useful indicator of the early recovery of liver metabolic capacities in the immediate postoperative period of orthotopic liver transplantation.

Glucose and potassium metabolic responses to insulin during liver transplantation

Insulin regulates glucose and potassium metabolism by acting differently upon peripheral tissues (e.g., skeletal muscle) and the splanchnic bed, including the liver. Liver disease is accompanied by "insulin resistance" of glucose metabolism, whereby glucose intolerance occurs despite relatively increased plasma insulin concentration. However, it is unknown whether insulin resistance extends to potassium metabolism. Further, it is uncertain whether the hyperglycemia and alterations of plasma potassium concentration observed during liver transplantation result from changes in circulating insulin concentration, altered sensitivity to insulin, or both, as the diseased liver is removed and replaced with a graft organ. The present study evaluated the role of the liver in maximal insulin responsiveness of whole-body glucose and potassium metabolism, using a hyperinsulinemic clamp technique, to identify the mechanism(s) underlying post-reperfusion hyperglycemia and intraoperative hyperkalemia. Two protocols were employed: in protocol 1 (n = 10), no exogenous insulin was administered. In protocol 2 (n = 10), an intravenous insulin bolus (666 mU . kg-1) was administered after anesthesia induction, followed by an infusion at 500 mU.m-2.min-1, which continued until 3 hours after portal vein unclamping. Plasma concentrations of glucose and potassium were regulated by glucose and potassium chloride infusion (euglycemic eukalemic clamp). Insulin-stimulated exogenous glucose and potassium uptakes were determined in protocol 2 before skin incision and during the dissection, anhepatic, and neohepatic stages. In both protocols, serial measurements of hemodynamic arterial blood gases, glucose, free fatty acids, potassium, insulin, and glucagon concentrations were made. Without insulin (protocol 1), progressive hyperglycemia peaked after portal vein unclamping (post-reperfusion hyperglycemia), with no concomitant decrease in plasma insulin concentration. Intraoperative plasma potassium concentration did not change. Insulin infusion (protocol 2) produced a stable hyperinsulinemia (approximately 2000 microU/mL). Hyperinsulinemia did not eliminate post-reperfusion hyperglycemia. Insulin-stimulated glucose uptake, in mg . kg-1 . min-1, was 8.10 +/- 0.78 (mean +/- SE) before skin incision, 7.62 +/- 0.82 during the hepatic dissection, 4.40 +/- 0.75 during the anhepatic stage, and 4.06 +/- 0.74 at 3 hours after portal vein unclamping. Insulin-stimulated potassium uptake, in mEq . kg-1 . hr-1, was 0.24 +/- 0.02 before skin incision, 0.21 +/- 0.04 during hepatic dissection, 0.07 +/- 0.02 during the anhepatic stage, and 0.21 +/- 0.04 and 0.19 +/- 0.05 at 30 minutes and 3 hours, respectively, after portal vein unclamping. We conclude that post-reperfusion hyperglycemia is not due to inadequate insulin stimulation. Liver disease-induced insulin resistance of glucose metabolism is exacerbated by hepatectomy and is not reversed during the intraoperative neohepatic stage. Liver disease does not impair maximal insulin-stimulated potassium uptake. The liver, even with end-stage disease, accounts for approximately 70% of insulin-stimulated potassium uptake.

Hemodynamic correlates of outcome in patients undergoing orthotopic liver transplantation. Evidence for early postoperative myocardial depression

OBJECTIVE

To describe the hemodynamic and oxygen transport patterns in survivors and nonsurvivors following liver transplantation (LT) and to assess their relationship to organ failure and mortality.

DESIGN

Retrospective cohort.

SETTING

Surgical ICU in a tertiary care university teaching hospital.

PATIENTS

Consecutive series of 113 adults undergoing LT between 1984 and 1992. Patients were excluded if they died intraoperatively (n = 2), required retransplantation (n = 8), or their records were incomplete (n = 7).

MEASUREMENTS AND MAIN RESULTS

Preoperative severity of illness was assessed by the acute physiology and chronic health evaluation (APACHE) II scoring system. Hemodynamic and oxygen transport variables were recorded immediately preoperatively and sequentially every 12 h during the first 2 postoperative days. Organ failures (pulmonary, renal, cardiovascular, hepatic, and central nervous system) were assessed for patients in the postoperative period. Patients were grouped as survivors (n = 82) or nonsurvivors (n = 14) with a mortality rate of 15%. Preoperative APACHE II scores were significantly lower in survivors compared with nonsurvivors (7 +/- 0 vs 11 +/- 2; p = 0.029). Both preoperatively and postoperatively, survivors sustained a relatively higher mean arterial pressure, stroke volume index, left ventricular stroke work index, cardiac index, and oxygen delivery as compared with nonsurvivors (p < 0.01). The postoperative decline in systemic blood flow that was seen in both groups was particularly prominent in nonsurvivors during the first 12 h following LT (p < 0.03). Nonsurvivors sustained an approximately fivefold increase in the rate of organ failure (p < 0.0001); all patients (n = 6) with 4 or more organ failures died.

CONCLUSION

Nonsurvivors of LT have less cardiac reserve pretransplant; postoperatively, they demonstrate early myocardial depression and subsequently lower levels of cardiac index and oxygen delivery. Patients who develop these hemodynamic patterns are more prone to organ failure and death.

Early death or retransplantation in adults after orthotopic liver transplantation. Can outcome be predicted?

Early, reliable outcome prediction after a liver transplant would help improve organ use by minimizing unnecessary retransplantations. At the same time, early intervention in those cases destined to fail may ameliorate the high morbidity and mortality associated with retransplantation. The purpose of this study was to analyze several parameters that have been identified in the past as being associated with patient and graft outcome, and to try to develop a model that would allow us to make predictions based on data available in the early postoperative period. A total of 148 patients were followed in a prospective, observational study. Graft failure was defined as patient death or retransplantation within 3 months of surgery. Preoperative variables studied included patient demographics, need for life support, presence of ascites, serum bilirubin, serum albumin, prothrombin time, serum creatinine, and the results of the cytotoxic crossmatch. During the first 5 postoperative days, standard measurements included serum transaminases, serum bilirubin, ketone body ratio, prothrombin time, factor V, and serum lactate. Oxygen consumption was measured shortly after surgery, once the patients had rewarmed to 36 degrees C. There were 131 successful transplants (88.5%) and 17 failures (11.5%). Most of the variables studied were found to be associated with outcome (by univariate analysis) at different points in the early postoperative period. However, receiver operating characteristic curve analysis showed that the predictive ability of even the best parameter was not adequate to make decisions on individual patients. Multivariate analysis, using stepwise logistic regression, yielded a model with an overall accuracy of 92.7%. Again, receiver operating characteristic curve analysis suggested that this model did not achieve the discriminating power needed for routine clinical use. We are still not able to accurately predict outcome in the early posttransplant period. We must be very careful when evaluating parameters, or scoring systems, that are said to accomplish this. It is especially important in this era of cost containment, with its renewed pressures to guide therapy based on our perceived understanding of a patient's future clinical course.

Concentrations in plasma and tissue penetration of ceftriaxone and ornidazole during liver transplantation

Plasma and epiploic fat drug concentrations and fat penetration of ceftriaxone and ornidazole given for antimicrobial prophylaxis were studied in 11 patients scheduled for liver transplantation. Ceftriaxone (1 g) and ornidazole (500 mg) were infused during 30 min after the induction of anesthesia. Arterial blood and epiploic fat samples were collected at 30, 60, and 120 min and then every 90 min following the end of the infusion until closure of the peritoneum. Blood samples were immediately centrifuged, and plasma and fat were stored at -35 degrees C until analysis. Ceftriaxone and ornidazole concentrations were determined by high-performance liquid chromatography. Surgery lasted 440 +/- 84 min and required a mean of 9.5 units of packed erythrocytes and 13 units of fresh frozen plasma. Plasma ceftriaxone concentrations decreased from 89 +/- 34 to 41 +/- 16.5 micrograms/ml from the beginning of the operation until the time of closure of the peritoneum. Corresponding levels in epiploic fat decreased from 8.7 +/- 3.3 to 4.5 +/- 3.5 micrograms/g. Ornidazole concentrations ranged, respectively, between 8.7 +/- 2.5 and 4.9 +/- 1.7 micrograms/ml in plasma samples and 4.6 +/- 1.2 and 2.5 +/- 1.1. micrograms/g in fat samples. Rates of penetration into the omentum remained at about 9% for ceftriaxone and between 50 and 70% for ornidazole. Tissue ceftriaxone concentrations were, in all cases, greater than typical MICs for 90% for Escherichia coli and Klebsiella isolates tested (MIC90S). They were insufficient in 40% of patients after 60 min with regard to the MIC90S for Staphylococcus aureus. Tissue ornidazole concentrations were not superior to MIC90S for anaerobes after 30 min in 50% of patients. These results show that a single dose of 1 g of ceftriaxone provides adequate coverage against gram-negative bacteria and that 1 g instead of 500 mg ornidazole may provide a protective effect against anaerobes during liver transplantation. Prophylaxis against S. aureus and Streptococcus faecalis requires more specific antibiotics. Prophylaxis for patients with significant blood loss or initial severe renal or hepatic failure needs further evaluation.

Oesophageal thermal tube for intraoperative hypothermia in liver transplantation

In order to prevent the occurrence of major hypothermia during liver transplantation, with its deleterious effects on intraoperative cardiovascular activity and on postoperative graft functioning, this study evaluated the benefit of an oesophageal rewarmer, used during surgery, in addition to the usual methods of warming (OR temperature at 22 degrees C, rewarming of fluids and blood, heating mattress, heat and moisture exchanger). We compared 10 patients with an oesophageal rewarmer (OeR group) to 10 patients without (Control group). The anaesthetic procedure was similar in all cases. Rectal (RT) and pulmonary artery (PT) temperatures were recorded during the three phases of surgery (pre-anhepatic, anhepatic, postanhepatic phase) and their time course was analysed with non-parametric tests. The two groups were comparable with regard to duration of surgery, blood and fluid requirements and veno-venous bypass flow rate. The RT decreased similarly in both groups, but was significantly higher in the OeR group at peritoneum closure (P < 0.01). The PT was higher in the OeR group after onset of venous shunting (P < 0.05) and during the third phase of surgery (P < 0.01). Three incidents (one leakage and two herniations of the latex tube) occurred, without detrimental effects on the patients. It is concluded that the oesophageal heat exchanger allows better rewarming after revascularization of the graft, but is unable to prevent cardiac hypothermia at unclamping.