Comparison of methotrimeprazine and meperidine as components of balanced anesthesia

Methotrimeprazine (MTM) (0.5 mg/kg) and meperidine (1.5 mg/kg) was administered to four groups of 10 patients each. Two of these groups (I and II) received MTM or meperidine 12 minutes before, two other groups (III and IV), 3 minutes after, induction of thiopental anesthesia. N2O-O2 was administered after thiopental induction, and fractional doses of meperidine and muscle relaxants were used as required for maintenance of anesthesia. The preliminary administration of MTM or meperidine decreased the induction dose of thiopental by about 60 percent. When administered before thiopental, both had similar effects on heart rate, but whereas MTM moderately decreased, meperidine moderately increased systolic and diastolic blood pressure MTM had little or no effect on respiratory rate, which was significantly depressed by meperidine. When given after an induction dose of thiopental, the circulatory effects of MTM and meperidine were similar. Respiratory measurements were little affected by MTM but were markedly depressed by meperidine. The mug/kg/min maintenance doses of meperidine were about the same in the four groups. Postanesthetic recovery of consciousness was delayed in the two MTM groups. The incidence of postoperative nausea and vomiting was less in the MTM than in the meperidine groups. MTM appears to have several advantages over meperidine as a component of balanced anesthesia, but is not desirable if rapid postanesthetic recovery or early ambulation is important. Its use is indicated in patients in whom even transient respiratory depression is undesirable and in those in whom prolonged postoperative sedation is desired.