Forty patients undergoing microlaryngoscopy were anaesthetized with thiopentone and nitrous oxide. Twenty patients received metoprolol 200 mg in a slow-release tablet once daily for 4 days up to, and including, the morning of operation, and 10 mg i.v. shortly before induction of anaesthesia. The other patients received placebo tablets and physiological saline i.v., instead. Both groups of 20 patients were further subdivided, half of the patients receiving fentanyl 1.0-1.5 mg during anaesthesia, the effect of which was antagonized by naloxone at the end of the procedure. The other patients received saline i.v. instead of fentanyl or naloxone. Metoprolol decreased heart rate and the general level of arterial pressure during anaesthesia, but did not affect the fluctuations in pressure. Arterial plasma noradrenaline concentrations during microlaryngoscopy were enhanced by metoprolol, in comparison with placebo, the reverse being the case for cortisol concentrations. Fentanyl decreased arterial pressure and plasma ACTH and cortisol concentrations regardless of whether the patient had received metoprolol. Plasma adrenaline and noradrenaline concentrations were decreased by fentanyl in the patients receiving metoprolol.

Twenty patients undergoing microlaryngoscopy were anaesthetised with thiopentone and nitrous oxide. Half of the patients received 1.0-1.5 mg of fentanyl during anaesthesia, the effect of which was antagonised by naloxone 0.4 mg intravenously and 0.4 mg subcutaneously. The other patients served as controls and received saline instead of fentanyl and naloxone. Fentanyl markedly reduced mean arterial pressure and the heart rate-systolic arterial pressure product during microlaryngoscopy. Conversely, there were significant increases in these measurements after naloxone had been given. However, there were no significant differences between patients given fentanyl with naloxone, and those given saline, in respect of arterial pressure, heart rate or dysrhythmia during recovery. No patient vomited, or appeared nauseated when observed afterwards in the operating room. One patient vomited several hours after naloxone.

The effects of the cardioselective beta-blockers practolol (Eraldin, ICI) and metoprolol (Seloken, Hässle) were studied during microlaryngoscopy. I. v. practolol (0.4 mg/kg before and 0.2 mg/kg during anaesthesia) did not protect against increases in arterial pressure, although heart rate was reduced. Oral metoprolol (0.2 g for 4 days) reduced the level of arterial pressure both before and during anaesthesia. Variations in arterial pressure were not attenuated. Very low levels of arterial pressure were seen, and variations in arterial pressures were attenuated when metoprolol was combined with fentanyl.