Alfentanil obtunds the cardiovascular and sympathoadrenal responses to suxamethonium-facilitated laryngoscopy and intubation.

Alfentanil 75 micrograms kg-1 or saline (control group) was given 1 min before induction of anaesthesia in 20 healthy patients premedicated with diazepam 0.14 mg kg-1 and pethidine 1 mg kg-1. Anaesthesia was induced with a sleep dose of thiopentone preceded by glycopyrrolate. Suxamethonium 1 mg kg-1 was used to facilitate laryngoscopy (which lasted 10 s) and tracheal intubation. Arterial pressure, heart rate and noradrenaline concentration in mixed venous plasma increased significantly after suxamethonium, and increased further after laryngoscopy and intubation in the control group (n = 10). The QT interval of the ECG was prolonged after the administration of suxamethonium, and was prolonged further after laryngoscopy and intubation. All these changes were attenuated in patients pretreated with alfentanil (n = 10), but four patients had chest wall rigidity. Changes in the QT interval correlated directly with the changes in plasma noradrenaline concentration (r = 0.67). Plasma adrenaline concentrations decreased during induction of anaesthesia in both groups.