CHANGES IN PLASMA-CATECHOLAMINE CONCENTRATIONS AND HEMODYNAMIC-EFFECTS OF ROCURONIUM AND VECURONIUM IN ELDERLY PATIENTS

Rocuronium administration may cause tachycardia and an increase in car diac index. Pancuronium, another steroidal non-depolarizing muscle rel axant, augments release of, and blocks re-uptake of catecholamines at adrenergic nerve endings. This study compared the haemodynamic effects of, and changes in catecholamine concentrations following administrat ion of vecuronium (0.12 mg kg(-1)) or rocuronium (0.9 mg kg(-1)) to el derly patients. Thirty patients, 65 years or older, not receiving beta -blockers, were studied. During thiopentone, fentanyl, nitrous oxide a naesthesia, either rocuronium (0.9 mg kg(-1)) or vecuronium (0.12 mg k g(-1)) was administered, according to random allocation. In all 30 pat ients, blood pressure and heart rate were measured before induction of anaesthesia, immediately and 1 min after induction, 1 and 2 min after muscle relaxant administration, and immediately, 1 and 2 min after tr acheal intubation. In the latter 20 patients, samples for plasma catec holamine estimation were obtained prior to, and 1 min after muscle rel axant administration and 1 min after tracheal intubation. Blood pressu re and heart rate were similar in the two groups throughout the study. Plasma noradrenaline concentrations were similar in the vecuronium an d rocuronium groups prior to muscle relaxant administration (589(SD240 ) and 444(SD213) pg mL(-1), respectively), 1 min after muscle relaxant administration (602(SD220) and 520(SD392) pg mL(-1), respectively) an d 1 min after tracheal intubation (597(SD351) and 440(SD181) pg mL, re spectively). There was no significant change in either plasma noradren aline or adrenaline concentrations in either group following muscle re laxant administration or tracheal intubation. The use of rocuronium (0 .9 mg kg(-1)) in elderly patients does not result in a clinically sign ificant change in heart rate, blood pressure or plasma catecholamine c oncentration.