[Total intravenous anesthesia with methohexital-alfentanil or propofol-alfentanil in hypogastric laparotomy. Clinical aspects and the effects of stress reaction].

Total intravenous anaesthesia (TIVA) using a combination of a hypnotic and an analgesic agent is gaining increasing popularity as an alternative to balanced anaesthesia with volatile anaesthetics for abdominal surgery. Among the required characteristics of the drugs used in this technique are a good correlation between dose, plasma concentrations, and effect as well as rapid elimination from the circulation, allowing close control of anaesthetic depth. Two hypnotic drugs with similar pharmacokinetic and pharmacodynamic profiles are propofol and methohexitone, both of which can be employed as a component of a TIVA technique. Two TIVA combinations utilising either of these drugs with alfentanil were tested against isoflurane-nitrous oxide in a balanced regimen. METHODS. Twenty-seven healthy women undergoing hysterectomy for non-malignant diseases participated in the study after having given written consent. They were randomly allocated to receive either isoflurane (Iso), methohexital-alfentanil (M-A), or propofol-alfentanil (P-A). Blood samples for determination of cortisol, prolactin, catecholamines, glucose, lactate, non-esterified fatty acids, and pharmacon concentrations were drawn repeatedly from before induction until 360 min after surgery. Anaesthesia was induced in group Iso with fentanyl 0.1 mg and M 1.5 mg.kg-1 and maintained with Iso-N2O. In the TIVA groups M or P was given in a two-step infusion to load peripheral compartments and then maintain plasma concentrations within the hypnotic range. A was given as a continuous infusion in an identical dose (0.1 mg.kg-1 initial, 0.125 mg.kg-1.h-1 maintenance) in both groups. If signs of insufficient depth of anaesthesia occurred (heart rate or systolic blood pressure > 25% above baseline), then first A (0.5-1 mg), and if that was ineffective, then 50 mg hypnotic was administered. The A infusion was stopped 30 min before the end of surgery, and Iso or the hypnotic was stopped at skin closure. Recovery time was the time until the patients were able to give their birth date after stopping the Iso or hypnotic. RESULTS. The three groups were comparable with regard to age, weight, and duration of surgery. The total doses of M and P were 1,357 +/- 125 mg (mean +/- SEM) and 1,315 +/- 121 mg, respectively, and the total A doses were 20.7 +/- 2.5 mg (M-A) and 23.4 +/- 3.5 (P-A). The peak plasma concentrations were P 10.6 +/- 1.5 micrograms.ml-1 and M 12.4 +/- 2.6 micrograms.ml-1. At the end of surgery the P concentrations were in the projected range while those of M were somewhat lower than expected (P 3.7 +/- 0.4 microgram.ml-1; M 3.5 +/- 0.6 microgram.ml-1). Three patients each in the P-A and M-A groups required supplementary A injections. Five patients in the P-A group required additional bolus injections of the hypnotic as compared to 2 in the M-A group. The median recovery times were Iso 15 min, M-A 50 min, and P-A 25 min (P < 0.05). The incidence of shivering was Iso 3/9, M-A 5/9, and P-A 0/9 (P < 0.05); vomiting occurred with equal frequency in all groups (Iso 33%, M-A 33%, P-A 22%). The patients were somewhat more restless in group M-A. Systolic blood pressure dropped in a similar manner in all groups after induction of anaesthesia (Iso -31%, M-A -37%, P-A -36%) but recovered during surgery. The intraoperative response of cortisol (Iso + 216%, M-A +92%, P-A +43%) and catecholamines (noradrenaline Iso +56%, M-A +30%, P-A -21%) was lower in the TIVA groups, whereas prolactin increased after induction in all groups. Plasma concentrations of glucose, lactate, and fatty acids were lower in the TIVA groups than in the Iso group intraoperatively, but increased to comparable postoperative levels. CONCLUSIONS. Both TIVA regimens are acceptable alternatives to balanced anaesthesia with Iso N2O. (ABSTRACT TRUNCATED)