Rocuronium administration may cause tachycardia and an increase in cardiac index. Pancuronium, another steroidal non-depolarizing muscle relaxant, 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 administration of vecuronium (0.12 mg kg−1) or rocuronium (0.9 mg kg−1) to elderly patients. Thirty patients, 65 years or older, not receiving β-blockers, were studied. During thiopentone, fentanyl, nitrous oxide anaesthesia, either rocuronium (0.9 mg kg−1) or vecuronium (0.12 mg kg−1) was administered, according to random allocation. In all 30 patients, 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 tracheal intubation. In the latter 20 patients, samples for plasma catecholamine estimation were obtained prior to, and 1 min after muscle relaxant administration and 1 min after tracheal intubation. Blood pressure and heart rate were similar in the two groups throughout the study. Plasma noradrenaline concentrations were similar in the vecuronium and 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) and 1 min after tracheal intubation (597(SD351) and 440(SD181) pg mL, respectively). There was no significant change in either plasma noradrenaline or adrenaline concentrations in either group following muscle relaxant administration or tracheal intubation. The use of rocuronium (0.9 mg kg−1) in elderly patients does not result in a clinically significant change in heart rate, blood pressure or plasma catecholamine concentration.

The changes in heart rate and arterial blood pressure following the administration of suxamethonium in healthy children (mean age 3.8 ± 0.3 years) during inhalational induction with either sevoflurane (n = 22) or halothane (n = 19) were studied. Heart rate 60 s following suxamethonium administration increased significantly in the sevoflurane but not in the halothane group. In the halothane group, four children required intravenous (i.v.) atropine as a result of bradycardia. None of the children in the sevoflurane group developed bradycardia following suxamethonium (P < 0.05). Values of oxygenation, ventilation and age corrected minimal alveolar concentration were comparable at all measurement times. The haemodynamic response to the administration of suxamethonium in children anaesthetized with sevoflurane seems to reflect the stimulation of the autonomic ganglia by suxamethonium whereas this positive chronotropic effect is attenuated or reversed by halothane.