[Prevention and treatment of hypotension during spinal anesthesia]. / Prévention et traitement de l'hypotension au cours de l'anesthésie médullaire.

Spinal and epidural anaesthesias alter self-regulation of arterial pressure as they lead to a sympathetic blockade. The extent and the speed of appearance of this blockade conditions the magnitude of the decrease of arterial pressure. So, epidural or spinal anaesthesias may only be performed on hemodynamically stable patients for a non hemorrhagic surgery. The routine fluid preloading is illogical and poorly efficient. Correcting a deep arterial hypotension demands first of all the use of vasoconstricting agents the choice of which depends on the site of the anaesthesia and on the cardiovascular condition of the patient. The occurrence of bradycardia more often indicates a hypovolaemic state.

Comparison of hypertonic saline (5%), isotonic saline and Ringer's lactate solutions for fluid preloading before lumbar extradural anaesthesia.

We have compared the haemodynamic effects of fluid preloading performed before lumbar extradural anaesthesia with isotonic saline (NS), 5% hypertonic saline (HS) and Ringer's lactate (RL) solutions in 30 ASA I patients undergoing minor orthopaedic surgery, allocated randomly to the three groups. All patients received an equal amount of sodium (2 mmol kg-1). After fluid preloading, lumber extradural anaesthesia was performed (2% lignocaine 6 mg kg-1) and ephedrine was administered in order to maintain mean arterial pressure (MAP) > 80% of its control value. Both volume and duration of fluid preload were significantly less in group HS (160 (SD 25) ml, 8.8 (SD 2.9) min) than in the two other groups (NS: 903 (144) ml, 17.7 (3.3) min; RL: 932 (166) ml, 212 (6.0) min) (P < 0.05). The number of blocked segments and the total amount of ephedrine administered were similar in the three groups. Heart rate increased significantly in all groups immediately after the fluid preload and remained increased until the end of the study (90 min). MAP was not affected by any fluid preload and its maximal decrease after lumbar extradural anaesthesia was similar in all groups. Infusion of 5% HS 2.3 ml kg-1 was tolerated well and produced a significant (P < 0.05) but moderate hypernatraemia lasting 90 min after the end of fluid preloading. We conclude that HS may be useful when rapid fluid preloading is desired, in situations where excess free water administration is not desired.

Does adult liver transplantation without venovenous bypass result in renal failure?

Thirty-eight adult orthotopic liver transplant recipients were studied to compare renal hemodynamics and renal function with (17 patients) and without (21 patients) venovenous bypass. Bypass was used when mean arterial blood pressure decreased by greater than 30% or cardiac index decreased by greater than 50%, or both, during a 5-min trial of clamping of the suprahepatic and infrahepatic vena cava and portal vein. Intraoperative measurements were performed 2 h after induction of anesthesia, 10 min before the end of the anhepatic phase, and 2 h after cava unclamping. During the anhepatic stage, renal perfusion pressure decreased significantly in the group with no bypass (79 +/- 20 vs 60 +/- 17 mm Hg, P less than 0.05) (mean +/- SD), whereas it remained unchanged in the group with bypass (77 +/- 14 vs 74 +/- 16 mm Hg, NS); urinary output was not modified in the bypass group, whereas it decreased significantly in the group with no bypass compared with the dissection phase (0.7 +/- 0.6 vs 1.7 +/- 2.0 mL.kg-1.h-1, P less than 0.05). However, during the postreperfusion phase, urinary output was similar in both groups and was more when compared with the dissection phase (P less than 0.05). Serum creatinine level was increased in both groups on the third postoperative day, but no difference occurred between the groups (bypass group 107 +/- 49 mmol/L; nonbypass group 126 +/- 95 mmol/L). No patient required dialysis in either group in the postoperative period. This study suggests that in patients without preoperative renal failure and who tolerate the trial of clamping well, venovenous bypass is not required to maintain postoperative renal function after liver transplantation.

Extrahepatic metabolism of propofol in man during the anhepatic phase of orthotopic liver transplantation.

We have investigated extrahepatic metabolism of propofol in 10 patients undergoing orthotopic liver transplantation (group 1) (mean age 38 yr, mean weight 60 (SD 7) kg) and compared it with that in 10 patients without liver dysfunction undergoing extrahepatic abdominal surgery (group 2) (mean age 56 yr, mean weight 68 (11) kg). A single i.v. bolus dose of propofol 0.5 mg kg-1 was injected into a peripheral vein 5 min after the beginning of the anhepatic phase in group 1 and 60 min after the induction of anaesthesia in group 2. Arterial blood samples were obtained at 5, 10, 15, 20, 30, 40, 50 and 60 min after injection and urine samples were collected every 15 min. Propofol concentrations in whole blood and urine were measured by high performance liquid chromatography with fluorescence detection. Propofol glucuronide was measured in urine by incubation with a specific beta-glucuronidase. The area under the time-blood concentration curve from 0 to 60 min was found to be significantly greater in group 1 (13743 (2830) micrograms litre-1 h-1) than in group 2 (7992 (4895) micrograms litre-1 h-1) (P less than 0.05). Unchanged propofol was not detected in the urine of either group. No significant difference was found in the amount of propofol glucuronide excreted by patients in group 1 (457 (269) micrograms) and in group 2 (921 (672) micrograms). The presence of a propofol metabolite in urine when the liver was excluded from the circulation suggests that extrahepatic metabolism occurred.

[Physiopathology of combined peridural and general anesthesia]. / Physiopathologie de l'association anesthésie péridurale--anesthésie générale.

General anaesthesia alters self-regulation of arterial pressure by lowering the sympathetic tone to his baseline level. More important is the sympathetic stimulation before general anaesthesia, more important will be the decrease in arterial pressure after induction. Epidural anaesthesia always leads to a sympathetic blockade. The extent and the speed of appearance of this blockade condition the magnitude of the decrease of arterial pressure. So, general anaesthesia and epidural anaesthesia both modifying deeply the autonomic nervous system, their association can only be performed on hemodynamically stable patients for a non hemorrhagic surgery. Correcting a deep arterial hypotension demands first of all the use of vasoconstricting agents the choice of which depends on the site of the epidural anaesthesia and on the cardiovascular condition of the patient. However, although the combined use of the two techniques is attractive, it does not seem to improve cardiovascular nor respiratory morbidities in high risk patients compared with classical general anaesthesia. Nevertheless, the high value of epidural analgesia may improve the postoperative course.

Dose requirements of vecuronium, pancuronium, and atracurium during orthotopic liver transplantation.

To further elucidate the role of the liver in the clearance of vecuronium, atracurium, and pancuronium, 30 patients undergoing orthotopic liver transplantation were randomly assigned to three comparable groups to receive a continuous infusion of vecuronium, atracurium, or pancuronium. The evoked integrated compound action potential of the hypothenar eminence in response to train-of-four ulnar nerve stimulation was measured and recorded. Anesthesia was induced with 3-5 mg/kg of thiopental, 50 micrograms/kg of midazolam, and 1-5 micrograms/kg of fentanyl IV and was maintained with continuous infusions of midazolam and fentanyl while the lungs were ventilated with an air-oxygen mixture. The infusion rates of vecuronium, atracurium, and pancuronium were adjusted to achieve a T1/Tc ratio of between 0.02 and 0.10 (T1 = height of first twitch, Tc = height of control twitch). Vecuronium and pancuronium requirements, which were 0.072 +/- 0.022 and 0.042 +/- 0.015 mg.kg-1.h-1 (mean +/- standard deviation) respectively during the dissection phase, decreased significantly during the anhepatic phase to 0.036 +/- 0.021 and 0.018 +/- 0.012 mg.kg-1.h-1 and returned toward the initial values in the postreperfusion phase (0.055 +/- 0.018 and 0.032 +/- 0.012 mg.kg.-1.h-1); whereas atracurium requirements remained unchanged during the three phases (0.667 +/- 0.199, 0.567 +/- 0.142, and 0.692 +/- 0.254 mg.kg-1.h-1). These data suggest that the liver has an important role in the elimination of vecuronium and pancuronium, whereas the elimination of atracurium is unaltered during exclusion of the liver from the circulation.

[What is the method of choice for hemodynamic monitoring in liver transplantation?]. / Quel monitorage hémodynamique lors des transplantations hépatiques?

Orthotopic liver transplantation requires close hemodynamic monitoring. Technological advances provide new possibilities of improving this monitoring. The most recent devices are the mixed venous oxygen saturation catheter, which gives continuous SVO2 values, and the right ejection fraction catheter used discontinuously. Our experience of 100 liver transplantations has enabled us to investigate the advantages of these catheters over the conventional Swan Ganz catheters.