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[The effects of age on onset and recovery from atracurium, rocuronium and vecuronium blockade].

UNLABELLED
Elderly patients may show an age-related decline in physiologic functions, which may be responsible for the prolonged duration of some neuromuscular blocking agents. Previous studies have yielded conflicting results as to the effects of these drugs in the elderly.


METHODS
After obtaining informed consent and approval of the Ethics Committee, we compared onset and recovery times of single IV doses of atracurium, rocuronium, and vecuronium given to 108 patients divided into three groups according to age (18-50, 51-64, > or = 65 years). Following oxazepam premedication and fentanyl and thiopentone induction, patients were randomly allocated to receive atracurium, rocuronium or vecuronium (0.5, 0.6, or 0.1 mg/kg, respectively) in < or = 0.8 vol.% enflurane (end-tidal)-nitrous oxide anaesthesia. Muscular relaxation was assessed by electromyographic (EMG) recording of the adductor pollicis muscle after supramaximal single-twitch stimulation 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. Creatinine clearance predicted from serum creatinine (Ccr) was correlated with recovery from neuromuscular block.


RESULTS
Onset time was not different among groups or relaxants. The results showed a prolonged duration 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 neuromuscular block, especially after atracurium and rocuronium. Ccr showed a negative correlation with age for all relaxants, but a negative significant correlation between Ccr and recovery was found only for rocuronium.


CONCLUSIONS
This study suggests that onset time for atracurium, rocuronium and vecuronium is not age-dependent. Recovery was prolonged in the elderly for all three relaxants. This effect appears to be secondary to changes in body composition and function accompanying the aging process. Neither atracurium nor vecuronium depends significantly on the kidney for elimination, but the negative correlation between Ccr and rocuronium suggests an appreciable role for the kidney in the elimination 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 atracurium and rocuronium.