Methohexital vs midazolam/flumazenil anaesthesia during laryngoscopy under jet ventilation

Abstract

In a randomised clinical study, two total intravenous anaesthesia techniques for microlaryngoscopic laser surgery were compared. After an induction dose of 100 mg methohexital, Group I received a maintenance infusion of 10 mg·min‐1. In Group II anaesthesia was obtained by 15 mg midazolam followed by 0.1 mg·min‐1 continuously and terminated by the injection of flumazenil. For analgesia 5 mg alfentanil were administered. Opiate‐induced respiratory depression was antagonised by 0.08 to 0.12 mg naloxone. Prior to, during, and after surgery, adrenergic response was assessed by HPLC‐analysis of blood taken from a peripheral vein. Haemodynamic responses to the operation and during the post‐operative period were almost identical in both groups. In Group I, the mean recovery period of 14 min was significantly longer than in Group II (9 min), where patients received a mean dose of 0.53 mg (0.15) flumazenil. Resedation could be observed in all patients receiving flumazenil within 60 min after antagonisation, which was associated with a mean decrease in O2‐saturation from 95% to 88%. There was no difference in epinephrine and norepinephrine blood levels between the two groups prior to and during anaesthesia. In all patients, arousal was associated with a significant increase in the epinephrine plasma concentration. While blood levels in Group I decreased during the post‐operative period to levels prior to surgery, the concentrations in Group II remained elevated. In one patient who received no naloxone, the reversal of midazolam action induced a 16‐fold increase in catecholamine levels (from 50 to 800 ng.1‐1) associated with a tachycardia of 170 b·min‐1 and hypertension of 160 mmHg. It is concluded that both anaesthetic techniques provide appropriate and equivalent anaesthesia for laryngeal surgery under jet ventilation. The shorter post‐operative period of unconsciousness after flumazenil administration can be regarded as an advantage. Yet, in single cases the use of flumazenil may lead to excessive adrenergic reactions combined with tachycardia and hypertension. This has to be considered when the antagonist is administered to high‐risk patients. The higher degree of post‐operative vigilance is less accepted by some patients. Post‐operative observation after antagonisation is mandatory as resedation may result in hypoxic episodes.

Flumazenil and midazolam in anaesthesia

“…Apart from one case in the report by Kulka (53), flumazenil is, in general, safe to reverse midazolam in patients at high cardiovascular risk, since it does not cause rebound hypertension (34, 41,42,55). For this reason, a combination of BZD and opioid should be reversed with flumazenil when it causes: a dangerous state of deep sedation; severe respiratory depression; and possibly anaesthesia; since naloxone could cause rebound hypertension (56).…”

Midazolam-Flumazenil Topical Anaesthesia for Microlaryngoscopy with Jet Ventilation

“…Microlaryngoscopic procedures under general anaesthesia and jet ventilation require a deep level of anaesthesia with a smooth induction, prompt awakening, and rapid recovery of cough reflex to prevent possible aspiration of blood and debris 2,6,12 . It is difficult to cope with the variation in surgical stimuli and the individual patient's response which alter anaesthetic needs, even with various complex dose regimens and infusion schemes of short-acting intravenous anaesthetics (propofol, thiopentone, methohexitone, etomidate and althesin) [1][2][3][4][5][6][7] . These dose regimens were designed to keep blood concentration at the desired level and need further clinical adjustment during the procedures.…”

“…Total intravenous anaesthesia (TIVA) in combination with venturi jet ventilation has been used for microlaryngeal surgery involving vocal cord and other procedures in the upper airway for many years [1][2][3][4][5] . Continuous infusion or intermittent injection of various ultra-short-acting intravenous anaesthetics (e.g.…”

“…Continuous infusion or intermittent injection of various ultra-short-acting intravenous anaesthetics (e.g. thiopentone, methohexitone, etomidate, althesin and propofol) have been successfully used for years [1][2][3][4][5][6][7] . A number of complex dose regimens and infusion schemes have been devised in order to keep the blood concentration at the desired level, but it is still difficult to provide adequate anaesthesia to cope with individual variation in responses to surgical stimuli.…”

“…Flumazenil (Anexate R ), a specific benzodiazepine antagonist, has been introduced to treat benzodiazepine over-sedation and intoxication [8][9][10] . Availability of flumazenil allows a benzodiazepine of appropriate duration of action to be used as the main drug in TIVA 1,[11][12] . The benzodiazepine anaesthesia can be reversed at the end of the procedure.…”