Supraceliac aortic clamping during the anhepatic phase of experimental orthotopic liver transplantation.

BACKGROUND: The pig tolerates simultaneous clamping of the liver pedicle and inferior vena cava poorly, so venovenous bypass has to be used during the anhepatic phase of experimental orthotopic liver transplantation (OLT). The aim of this work is to assess whether clamping of the supracoeliac aorta during the anhepatic phase (AP) of experimental OLT in pigs allows transplantation in stable hemodynamic conditions. METHODS: Fourteen pigs (weight, 16 to 18 kg) received whole liver grafts from 14 age-matched donors and were subsequently divided into two groups: group I, OLT without venovenous bypass during the AP, group II, OLT with supracoeliac aortic clamping during the AP. Variables analyzed were cardiac output (CO) and related variables, mean systemic arterial pressure (MAP), mixed venous oxygen saturation (SvO2), hepatic artery and portal vein blood flow, systemic and hepatic O2 supply and uptake (SDO2, SVO2, HDO2, HVO2, respectively), liver enzymes, glucose, creatinine, and electrolytes. RESULTS: In group I, CO, MAP, and SvO2, decreased during the AP (anhepatic) in comparison with baseline (preanhepatic) values (CO, 3.60+/-0.74, preanhepatic, v. 1.21+/-0.25 L x min(-1), anhepatic; P<.05. MAP, 97+/-12, preanhepatic, v. 43+/-17 mm Hg, anhepatic; P<.05. SvO2, 91.6+/-5.6, preanhepatic v. 70.0+/-12.5%, anhepatic; P<.05), and SDO2/SVO2 increased by 16% (preanhepatic) to 33% (anhepatic; P<.05). In group II, CO decreased during the anhepatic phase by only 21% (3.82+/-0.81, preanhepatic, v. 3.07+/-0.99 L x min(-1), anhepatic; not significant), the MAP increased significantly (100+/-8, preanhepatic, v. 135+/-4 mm Hg, anhepatic; P<.05), and SVO2, SDO2, SVO2, and SDO2/SVO2 remained unchanged. After revascularization, none of these variables differed significantly between groups, and levels of liver enzymes, glucose, creatinine, urea, and electrolytes were similar in both groups, both before and aftertransplantation. CONCLUSIONS: Experimental OLT can be carried out in pigs without venovenous bypass, but it leads to severe hemodynamic disturbances. Clamping of the supraceliac artery during the AP is well tolerated and results in excellent hemodynamic stability, so it may prove to be a useful technique in liver transplantation in animals, such as dogs or pigs, that do not tolerate simultaneous clamping of the liver pedicle and inferior vena cava as well as human beings.

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).

The effect of hepatic vascular exclusion on hepatic blood flow and oxygen supply--uptake ratio in the pig.

The hemodynamic disturbances produced by total hepatic vascular exclusion (THVE) for 40 minutes were studied in 7 pigs (19-22 kg). THVE was produced by clamping the hepatic pedicle and inferior vena cava, above and below the liver, for a 40-minutes period, followed by unclamping. Compared to baseline values, 30 minutes after onset of THVE, there was a decrease in cardiac output (3.86 +/- 0.55 vs 1.23 +/- 0.23 L x min-1), systemic arterial pressure (97.54 +/- 13.58 vs 43.43 +/- 11.38 mm Hg), and pulmonary artery pressure (16.57 +/- 6.38 vs 12.57 +/- 3.58) and an increase in systemic and pulmonary vascular resistance (1772 +/- 198 vs 2351 +/- 462, and 182 +/- 66 vs 361 +/- 124 dyn x s x cm-5 respectively). As a result of diminished cardiac output, the systemic oxygen supply decreased (461 +/- 131 vs 101 +/- 46 ml x min-1), but the systemic oxygen extraction rate rose from 17.3% t0 31.2%. Thirty minutes after unclamping, the changes had reversed and all the parameters tended to normalize. Total hepatic blood flow 30 minutes after unclamping was higher than at baseline (5.08 +/- 1.2 vs 6.66 +/- 0.67 ml x min-1 x 100 g-1), because of the increase in portal blood flow (4.52 +/- 1.21 vs 6.07 +/- 0.70 ml x min-1 x 100 g-1). There were no significant differences in hepatic oxygen supply and uptake at baseline and after unclamping (152.6 +/- 23.0 vs 187.0 +/- 34.7 and 22.7 +/- 4.9 vs 28.7 +/- 8.4 ml O2 respectively). AST rose (29 +/- 7 vs 136 +/- 91 U/l), but there was no change in the remaining liver enzymes, glucose, creatinine and serum electrolytes, so we conclude that the hemodynamic disturbances produced by 40 minutes of THVE are manageable and spontaneously reversible. Liver metabolism was not greatly disturbed, so THVE was judged to be a viable technique to be added to the surgeon's range of options.

Donor vascular grafts for arterial reconstruction in pediatric liver transplantation.

The authors compared the results of 48 orthotopic liver transplantations (OLT) in which revascularization was achieved with a conduit interposed between the receptor aorta and the graft (vascular graft [VG] group) with those obtained for 56 OLT performed during the same period (1991 to 1994) in which end-to-end anastomosis (EEA) of the hepatic arteries or celiac trunk was used (EEA group). In the VG group, the interposed conduits were the cadaveric iliac artery (37) the living-donor saphenous vein (3), or nonthrombosed conduits from previous transplants (8) (7 iliac arteries, 1 saphenous vein). There were significant differences between the two groups with respect to recipient age, recipient weight, the retransplant:first transplant ratio, the number of emergency transplantations, the use of reduced-size grafts, and intraoperative transfusion requirements. Twenty-nine grafts in the VG group (60.4%) and 43 in the EEA group (76.7%) currently are functioning. The actuarial 3-year graft survival rates are 60% and 71.5% for the VG and EEA groups (P < .05), respectively. The rate of arterial thrombosis did not differ between the two groups. The authors conclude that, although EEA of the hepatic artery is still the preferred revascularization technique for OLT, revascularization of the liver graft by conduit interposition is safe when EEA is not possible. Reutilization of the interposed conduit during retransplantation proved to be safe in the absence of hepatic artery thrombosis.