THE EFFECTS OF AGE ON ONSET AND RECOVERY FROM ATRACURIUM, ROCURONIUM AND VECURONIUM BLOCKADE UNDER ENFLURANE ANESTHESIA

Elderly patients may show an age-related decline in physiologic functi ons, which may be responsible for the prolonged duration of some neuro muscular blocking agents. Previous studies have yielded conflicting re sults as to the effects of these drugs in the elderly. Methods. After obtaining informed consent and approval of the Ethics Committee, we co mpared onset and recovery times of single IV doses of atracurium, rocu ronium, and vecuronium given to 108 patients divided into three groups according to age (18-50, 51-64, greater than or equal to 65 years). F ollowing oxazepam premedication and fentanyl and thiopentone induction , patients were randomly allocated to receive atracurium, rocuronium o r vecuronium (0.5, 0.6, or 0.1 mg/kg, respectively) in less than or eq ual to 0.8 vol.% enflurane (end-tidal)-nitrous oxide anaesthesia. Musc ular relaxation was assessed by electromyographic (EMG) recording of t he adductor pollicis muscle after supramaximal single-twitch stimulati on of the ulnar nerve every 10 s. Onset time and recovery to 25%, 75% and 90% of twitch control values (DUR25, 75, 90) were recorded. Creati nine clearance predicted from serum creatinine (C-cr) was correlated w ith recovery from neuromuscular block. Results. Onset time was not dif ferent among groups or relaxants. The results showed a prolonged durat ion of action for atracurium (DUR75, DUR90), rocuronium (DUR25, DUR75) , and vecuronium (DUR25) in the elderly. A number of patients did not reach DUR75 or DUR90. There was a significant relationship between age and failure to return to control values during recovery from neuromus cular block, especially after atracurium and rocuronium. C-cr showed a negative correlation with age for all relaxants, but a negative signi ficant correlation between C-cr and recovery was found only for rocuro nium. Conclusions. This study suggests that onset time for atracurium, rocuronium and vecuronium is not age-dependent. Recovery was prolonge d in the elderly for all three relaxants. This effect appears to be se condary to changes in body composition and function accompanying the a ging process. Neither atracurium nor vecuronium depends significantly on the kidney for elimination, but the negative correlation between C- cr and rocuronium suggests an appreciable role for the kidney in the e limination of this relaxant. The long recovery times observed in this study could also be related to enflurane anaesthesia. We suggest that failure of EMG responses to return to baseline values during recovery from neuromuscular block may be related to age, especially for atracur ium and rocuronium.