Tissue oxygenation during liver transplantation.

OBJECTIVES: a) To assess perioperative changes in tissue oxygenation parameters during liver transplantation; b) to evaluate the need for venovenous bypass as hemodynamic support; and c) to assess the efficacy of mixed venous oxygen saturation monitoring and the importance of lactate determinations in the management of patients following liver transplantation. DESIGN: Prospective case series. SETTING: Liver transplant unit in a university hospital. PATIENTS: A total of 68 consecutive patients undergoing liver transplantation. The entire population was analyzed before and after transplantation, dividing the patients into two groups, based on whether their initial cardiac index was higher (n = 37) or lower (n = 31) than 4.5 L/min/m2. MEASUREMENTS: Hemodynamic measurements and blood gas analyses were made before incision, before vascular clamping (including hepatic artery, portal vein and inferior vena cava), during the anhepatic phase, and at 5, 30, 60, and 120 mins following unclamping. Oxygen transport and oxygen consumption values were calculated. Serum lactate concentrations were measured by enzymatic technique. MAIN RESULTS: Mixed venous oxygen saturation was correlated with oxygen transport (Do2) in the whole population in which an abnormal oxygen consumption (Vo2)-Do2-dependent relationship occurred from the beginning of operation until 30 mins following unclamping. The comparison between hyperdynamic patients (initial cardiac index greater than 4.5 L/min/m2) with impaired tissue oxygenation and normodynamic patients showed that mixed venous oxygen saturation failed to correlate with Do2 when the cardiac index was greater than 4.5 L/min/m2 and that the Vo2-Do2 dependency was only noted in these patients. The serum lactate concentrations were similar in both groups. CONCLUSIONS: The Vo2-Do2-dependent relationship and mixed venous oxygen saturation-Do2 correlation noted in the 68 studied patients suggest the need for venovenous bypass and the reliability of mixed venous oxygen saturation monitoring in all patients scheduled for liver transplantation. However, a sharper comparison between hyperdynamic and normodynamic patients demonstrated the lack of efficacy of mixed venous oxygen saturation monitoring in predicting adequate tissue oxygenation in the first group and the mandatory need for venous shunting to limit tissue hypoxia which occurred despite its use only in these patients. Lactic acidosis appeared similarly in both groups and could not be linked to tissue hypoxia.     

Effects of low-dose dopexamine on splanchnic oxygenation during major abdominal surgery

OBJECTIVE: To study the influence of low-dose dopexamine on splanchnic oxygenation during major abdominal surgery. DESIGN: Prospective, randomized, placebo-controlled study. SETTING: University hospital. PATIENTS: Eighteen adult patients undergoing elective major abdominal surgery. INTERVENTIONS: The patients received either dopexamine at 1 microg/kg/min (group A, n = 9) or 0.90% saline as control (group B, n = 9). MEASUREMENTS AND RESULTS: To assess the splanchnic oxygenation, intestinal tissue PO2 (PtissO2) and gastric intramucosal Pco2 (PmucCO2) were measured, and the PCO2 gap (PmucCO2 - PaCO2) was calculated at baseline (T1) and after an infusion period of 60 mins (T2). There was no difference between the groups in the global oxygen transport parameters. Low-dose dopexamine increases PtissO2 on the serosal side of the small bowel (deltaPtissO2, 17+/-24 mm Hg in group A vs. -5+/-10 in group B). The changes in PtissO2 at the serosal side of the colon after dopexamine demonstrated a nonsignificant increase (deltaPtissO2, 7+/-11 mm Hg in group A vs. -11+/-23 mm Hg in group B). In both groups, the Pco2 gap (group A, 6+/-7 mm Hg [T1] and 5+/-6 mm Hg [T2], vs. group B, 9+/-10 mm Hg [T1] and 12+/-10 mm Hg [T2]) remained unchanged compared with the baseline. CONCLUSION: It is concluded that low-dose dopexamine improves PtissO2 at the serosal side of the gut, preferably at the small bowel. However, low-dose dopexamine did not improve gastric PmucCO2.     

Hepatic and splanchnic oxygen consumption during acute hypoxemic hypoxia in anesthetized pigs

OBJECTIVE: To compare the hepatosplanchnic oxygen consumption (VO2) with the hepatic and splanchnic VO2 and to calculate the critical oxygen delivery (DO2crit) below which VO2 decreases in the hepatic, splanchnic, and hepatosplanchnic regions in a model of hypoxemic hypoxia. DESIGN: Prospective animal study. SETTING: University research laboratory. SUBJECTS: Anesthetized and ventilated pigs (n = 7). INTERVENTIONS: The right carotid artery was cannulated to measure mean arterial pressure. A pulmonary artery catheter was inserted to measure mean pulmonary arterial pressure and cardiac output. After a midline abdominal incision, two flow probes were positioned around the portal vein and the hepatic artery to measure portal vein blood flow and hepatic artery blood flow. Oxygen and lactate contents in the carotid artery, the portal vein, and the hepatic vein were measured in blood samples obtained from the appropriate catheters. MEASUREMENTS AND MAIN RESULTS: After a 2-hr stabilization period, hemodynamic and biological variables were recorded during acute hypoxemic hypoxia (FIO2 = 0.5, 0.4, 0.3, 0.21, 0.15, 0.10, and 0.07). VO2, DO2, and DO2crit were determined in the hepatic, splanchnic, and hepatosplanchnic regions. The hepatosplanchnic VO2 was 48 +/- 5 mL/min at high FIO2 (40% for the liver and 60% for the splanchnic organs) and decreased below FIO2 of 0.15. Lactate uptake in the whole hepatosplanchnic region remained steady at FIO2 values of 0.5 to 0.15 and then switched to a lactate release at low FIO2. However, the splanchnic region released lactate, whereas lactate was taken up by the liver. DO2crit in the hepatic, splanchnic, and hepatosplanchnic regions was 24 +/- 3, 38 +/- 2, and 49 +/- 4 mL/min, but the systemic DO2crit, below which regional VO2 became oxygen supply dependent, did not differ in the liver, splanchnic, and hepatosplanchnic regions. CONCLUSIONS: The variables of oxygenation and lactate flux measured in the hepatosplanchnic region summarize the metabolic changes of various organs that may vary in different ways during hypoxemic hypoxia.     

Hemodynamic changes in splanchnic circulation after orthotopic liver transplantation in patients with liver cirrhosis

BACKGROUND: Liver cirrhosis increases portal vein pressure and alters the splanchnic circulation. With Doppler sonography, we investigated the hemodynamic changes in the portal vein, superior mesenteric artery, hepatic and splenic arteries and spleen size in a group of patients with end-stage liver disease before and after orthotopic liver transplantation (OLT). METHODS: Ten patients (seven male, three female; mean age = 48.8 +/- 7.6 years) who underwent OLT for liver cirrhosis mainly associated with hepatitis C virus infection completed the study. The control group consisted of 10 patients matched by sex and age who had no gastroenterologic or vascular diseases. All patients underwent duplex Doppler sonography (Toshiba SSA 270A with a 3.5-MHz probe) after 24 h of fasting (baseline) and then 6 and 12 months after OLT. The following parameters, expressed as the mean of three measurements, were evaluated: portal flow velocity (PFV), pulsatility index of the superior mesenteric artery (MAPI), resistance indexes of the hepatic (HARI) and splenic (SARI) arteries, and longitudinal diameter of the spleen (LDS). RESULTS: PFV in the pre-OLT phase was significantly lower in the patients than in the controls ( p < 0.0001); it progressively and significantly increased over baseline levels at 6 and 12 months ( p < 0.0001), approaching control values. LDS in the pre-OLT phase was significantly higher than in controls ( p < 0.0001); after OLT, it decreased significantly compared with baseline values ( p < 0.005). The MAPI of patients in the pre-OLT phase was lower than that in controls ( p < 0.0001); post-OLT, it progressively increased and reached values that were significantly above baseline at 12 months ( p < 0.005). In the pre-OLT phase, the HARI and SARI were significantly higher than in controls ( p < 0.04); 6 and 12 months after OLT, those values were significantly below baseline values ( p < 0.001), and there was no significant difference from control values. CONCLUSION: These data show that many of the hemodynamic parameters typical of decompensated cirrhosis improve progressively within 12 months after transplantation.     

Anesthesia during liver transplantation

Different methods and components of anesthesia during operations in donors and recipients were studied by using the experience in maintaining anesthesia during 39 relative and 7 cadaveric hepatic transplantations. The experience in using epidural anesthesia and total intravenous anesthesia at the donor stage of hepatic lobar transplantation was comparatively analyzed. Combined epidural anesthesia (CEA) may be used during long-term and traumatic operations dealing with hepatic lobectomy in a relative donor since it is noted for low hepatotoxicity and no drastic hemodynamic exposures. CEA can substantially reduce pharmacological loading with opioids or myorelaxants, which is particularly important in taking the lobe of the liver. This reduces the recovery period of adequate own respiration, activates a patient more rapidly, substantially reduces the risk for postoperative iatrogenic complications. Balanced general anesthesia whose major component is inhalational anesthesia with isoflurane is the method of choice in performing an operation in the recipient. The use of isoflurane in the minimal-flow mode is cost-effective and safe. When anesthesia is performed in the recipient, it is necessary to take in account drastic hemodynamic pattern changes at the liverless stage during vein-venous bypass surgery, including the liver into systemic circulation, and the likelihood of development of significant reperfusion and concomitant metabolic and coagulative disorders.     

Hepatic transplantation

In this article hepatic transplantation is discussed with respect to selection of patients, indications and contraindications, the donor and recipient operation, complications, and results.     

Plasma glucose concentrations during liver transplantation

We reviewed the intraoperative plasma glucose concentrations in 100 consecutive patients who underwent orthotopic liver transplantation. The plasma glucose concentration increased significantly (P less than 0.05) from 110 +/- 46 mg/dl (mean +/- SD) to 204 +/- 60 mg/dl during the preanhepatic phase of transplantation (phase I). No significant change in plasma glucose concentrations occurred during the anhepatic phase (phase II). During the reperfusion phase (phase III), the mean plasma glucose concentration increased significantly (P less than 0.05) from 201 +/- 56 mg/dl to 384 +/- 72 mg/dl. The only glucose administered was that contained in the blood products. No correlation was found between the amount of glucose administered with the blood products and the changes in plasma glucose concentrations in these patients. None of the patients became hypoglycemic during any phase of the transplant procedure. All patients demonstrated a tendency toward hyperglycemia.     

Prostacyclin levels during orthotopic liver transplantation

Many anesthesia providers involved in orthotopic liver transplantation (OTL) have become increasingly aware of the incidence of hypotension immediately following revascularization of the donor liver. Postreperfusion syndrome (PRS) is usually characterized by a decrease in systemic blood pressure of at least 30 torr with a duration of 5 minutes or more. Several researchers have suggested that the etiology of this hypotension may be related to acute hyperkalemia, acidosis, hypothermia, reflex systemic vasodilation, or some yet unidentified prostaglandin liberated from the gut at reanastomosis. The potential role of prostacyclin as the primary etiologic agent responsible for this syndrome was studied. Serum prostacyclin measurements were obtained in seven patients 1 minute before and 5 minutes after revascularization. Coincident measures were taken of preselected cardiovascular parameters. Five patients demonstrated increased levels of prostacyclin during clamping of the portal vein and four experienced significant hypotension at reperfusion. In the five patients demonstrating hypotension, a decrease in heart rate and systemic vascular resistance and an increase in cardiac output and PCWP was noted. It is concluded that one or more endogenous prostacyclins may play an important role in the etiology of postreperfusion syndrome.     

Cerebral perfusion during human liver transplantation

Summary. During transplantation of the liver cerebral perfusion was monitored by transcranial Doppler determined middle cerebral artery mean flow velocity (V_mean) and pulsatility index (PI) in six fulminant hepatic failure patients and 11 patients with chronic liver disease. In both groups of patients V_mean, PI and central haemodynamic variables were recorded during (1) the last preanhepatic hour; (2) the anhepatic phase; (3) the first 15 min of reperfusion; and (4) for the following 45 min of reperfusion. No significant differences were detected between the two groups of patients with respect to changes of variables with time. The V_mean (40±13 cm s^-1 [mean±SD]), thoracic electrical impedance (TI) (30±7 Ohm), heart rate (97±19 beats min^-1), mean arterial pressure (84±9 mmHg) and arterial carbon dioxide tension (PaCO₂, 4.5±0.4 kPa) remained stable in the anhepatic phase, while cardiac output (CO, 7.6±2.7 to 5.4±1.41 min^-1), stroke volume (SV, 79±26 to 56±15 ml) and PI (1.2±0.3 to 0.9±0.2) decreased (P<0.05). During reperfusion, CO (9.9±4.01 min^-1), SV (105±40 ml), Pa_CO2 (5.5±0.6 kPa), Vmean (57±17 cm s^-1) and PI (1.2±0.2) became elevated. Taken together, during the anhepatic phase of the liver transplantation a maintained central blood volume as indicated by the constant TI served for a stable blood pressure and in turn cerebral perfusion, whereas revascularization of the graft increased cerebral perfusion concomitant with an elevated carbon dioxide tension.     

肝移植围术期循环支持和心肌保护

近年,肝移植在我国取得长足发展,其围术期管理已成为移植科医生、麻醉科医生、ICU医生共同关注的课题。随着对终末期肝病病理生理研究的深入,对肝移植术中大血管阻断及开放引起血液流变学剧变、移植肝开     

Blood transfusions increase cerebral,splanchnic, and renal oxygenation in anemic preterm infants

BACKGROUND: Multiprobe near infrared spectroscopy (NIRS) has been used to study regional cerebral (rSO₂C), splanchnic (rSO₂S), and renal (rSO₂R) tissue oxygenation in newborns. We used this method to study the effects of red blood cell (RBC) transfusions in anemic preterm infants to assess if thresholds for transfusions were appropriate for recognizing a clinical condition permitting tissue oxygenation improvement. STUDY DESIGN AND METHODS: Multiprobe NIRS (INVOS 5100, Somanetics) was applied during transfusion to 15 preterm infants with symptomatic anemia of prematurity (hematocrit level of <25%). rSO₂C, rSO₂S, and rSO₂R were recorded at selected times, and then fractional oxygen cerebral extraction ratio [FOEC: (SaO₂‐rSO₂C)/SaO₂], fractional oxygen splanchnic extraction ratio [FOES: (SaO₂‐rSO₂S)/SaO₂], fractional oxygen renal extraction ratio [FOER: (SaO₂‐rSO₂R)/SaO₂], cerebrosplanchnic oxygenation ratio [CSOR: (rSO₂S/rSO₂C)], and cerebrorenal oxygenation ratio [CROR: (rSO₂R/rSO₂C)] were calculated. In addition, we used Doppler ultrasonography for evaluating cerebral blood flow (CBF), splanchnic blood flow (SBF), and renal blood flow (RBF) velocity. RESULTS: rSO₂C, rSO₂S, and rSO₂R significantly increased during transfusions, while FOEC, FOES, and FOER decreased. CSOR and CROR increased during transfusions. CBF velocity decreased during the study period, while SBF and RBF velocities did not vary. CONCLUSION: RBC transfusions performed at used thresholds permitted an increase in cerebral, splanchnic, and renal oxygenation. The associated decreases in oxygen tissue extraction might suggest that transfusions were well timed for preventing tissue hypoxia or too early and theoretically prooxidant. Further studies could help to clarify this issue.     

Hepatic vein oxygenation, liver blood flow, and the rate of ethanol metabolism in recently abstinent alcoholic patients

Abstract To determine whether hepatic hypoxia is associated with hepatocellular necrosis in alcoholics, oxygen tension in the hepatic vein and hepatic blood flow were determined in thirteen patients without overt clinical liver disease. Ethanol metabolic rate was also assayed as an index of liver metabolism. Hepatic blood flow and ethanol metabolic rate were also determined in six normal volunteers. According to liver histology patients were separated into two groups, with and without hepatocellular necrosis. Alcoholics with necrosis showed a higher ( P < 0–002) ethanol metabolic rate (405 ± 0–23 mmol/kg/h) than those without necrosis (2–46 ± 0–34). Hepatic blood flow in the total group of alcoholics was not significantly different from controls; in the group with necrosis it was lower (651–7 ± 44–6 ml/min/m²) than in the group without necrosis (878–3 ± 81–6; P < 0025). Hepatic vein pO₂ was lower ( P < 001) in patients with hepatocellular necrosis (31–7 ± 0–68 mmHg) than in patients without necrosis (35–7 ± 0–99). In the whole group, a significant negative correlation ( r = -0 76, P < 0–003) was observed between hepatic vein pO₂ and ethanol metabolic rate. Acute administration of ethanol (21–7 mmol/kg) did not alter hepatic blood flow in six normal individuals nor in five alcoholic patients, although an increase in hepatic vein pO₂ was observed in the latter. The changes observed in hepatic vein pO₂, functional hepatic blood flow, and ethanol metabolic rate which correlate with hepatocellular necrosis, may be of pathogenic importance in alcoholic liver disease.     

肝移植手术中的体温观察

目的探讨肝移植手术患者手术中的体温变化,实施有效的护理措施。方法对2002年6月至2004年10月实施的73例肝移植患者手术切皮期及无肝前期、无肝期、新肝期3个时期的早、中、晚3个不同时间段的体温变化进行回顾性分析。观察记录术中最低体温出现时间,新肝期门静脉开放时间。术中采用变温水毯、充气式保温毯、血液加温仪以及40℃温水间断冲洗。结果肝移植患者在术中不同时间的体温差异有统计学意义,F=209.628,P＜0.001。患者体温从无肝前期旱段到新肝期早段缓慢持续下降,在新肝期早段降到最低,新肝期晚段体温逐渐恢复。结论在术中采取变温水毯、充气式保温毯、血液加温仪、40℃温水间断冲洗是肝移植术中体温恢复的有效手段,提示在新肝期采取护理措施避免低体温出现。     

Hepatic vein oxygenation, liver blood flow, and the rate of ethanol metabolism in recently abstinent alcoholic patients

Abstract. To determine whether hepatic hypoxia is associated with hepatocellular necrosis in alcoholics, oxygen tension in the hepatic vein and hepatic blood flow were determined in thirteen patients without overt clinical liver disease. Ethanol metabolic rate was also assayed as an index of liver metabolism. Hepatic blood flow and ethanol metabolic rate were also determined in six normal volunteers. According to liver histology patients were separated into two groups, with and without hepatocellular necrosis. Alcoholics with necrosis showed a higher ( P < 0–002) ethanol metabolic rate (405±0–23 mmol/kg/h) than those without necrosis (2–46±0–34). Hepatic blood flow in the total group of alcoholics was not significantly different from controls; in the group with necrosis it was lower (651-7±44-6 ml/min/m²) than in the group without necrosis (878-3±81-6; P < 0025). Hepatic vein pO₂ was lower ( P < 001) in patients with hepatocellular necrosis (31-7±0–68 mmHg) than in patients without necrosis (35-7±0–99). In the whole group, a significant negative correlation ( r = -0 76, P < 0–003) was observed between hepatic vein pO₂ and ethanol metabolic rate. Acute administration of ethanol (21-7 mmol/kg) did not alter hepatic blood flow in six normal individuals nor in five alcoholic patients, although an increase in hepatic vein pO₂ was observed in the latter. The changes observed in hepatic vein pO₂, functional hepatic blood flow, and ethanol metabolic rate which correlate with hepatocellular necrosis, may be of pathogenic importance in alcoholic liver disease.