Neurological phenomena during emergence from enflurane or isoflurane anaesthesia

During emergence from anaesthesia, transient neurological signs that would usually be considered pathological may appear. The objective of this randomized, patient (n = 30) and observer-blinded study was to compare prospectively the incidence and duration of post-anaesthetic neurological abnormalities in healthy patients undergoing minor elective procedures following thiopentone and succinylcholine induction, and enflurane-N2O or isoflurane-N2O anaesthesia. Patients were studied for 60 min after anaesthesia. Arousal state, muscle tone, deep tendon reflexes, plantar reflex, sustained clonus, shivering, intense muscular spasticity and temperature were assessed. Results of neurological examination were correlated with the patient's state of arousal. Transient emergent neurological abnormalities occurred more frequently following enflurane-N2O anaesthesia than isoflurane N2O anaesthesia. This was statistically significant (P less than 0.05) for quadriceps hyperreflexia, upgoing toes (positive Babinski reflex) and intense muscular spasticity. Neurological abnormalities occurred most commonly 5-20 min after anaesthesia and all abnormalities resolved within 60 min. Following enflurane anaesthesia, as patients became more alert the incidence of abnormalities declined, while the arousal state did not affect the incidence of abnormalities after isoflurane. There was no significant difference between axillary temperatures of those patients who shivered and those who did not. In conclusion, temporary emergent neurological abnormalities occurred more often following enflurane-N2O than after isoflurane-N2O anaesthesia.