Neurologic changes during awakening from anesthesia

Transient hyperreflexia, the Babinski reflex, and other transient neurologic signs may follow anesthesia in healthy persons. The authors describe the appearance and durations of these signs and relate them to anesthetic agent, time following cessation of anesthesia, and state of arousal. Twenty-nine neurologically normal male patients undergoing superficial operations were anesthetized with halothane-nitrous oxide, enflurane-nitrous oxide, or nitrous oxide-narcotic. During awakening, patients experienced transient hyperreflexia and shivering following all anesthetic techniques. Quadriceps hyperreflexia occurred in three of eight patients after halothane-N2O, seven of 12 patients after enflurane-N2O, and no patient after n2O-narcotic anesthesia. Sustained ankle clonus and upgoing plantar responses were observed most frequently following enflurane-N2O (50 percent of patients). Following halothane-N2O, ankle clonus was observed in 12.5 per cent of patients and upgoing plantar responses in 25 per cent of patients. Neither sign occurred after N2O-narcotic anesthesia. Shivering, too, was observed most frequently following enflurane anesthesia (66 per cent of patients). There were equal reductions of body temperature in shivering and nonshivering patients. In every patient, regardless of the anesthetic used, the lash reflex and the pupillary response to light returned to normal with the return of consciousness as measured by the response to verbal commands. It is concluded that the neurologic profile during awakening from general anesthesia is most abnormal following enflurane-N2O, compared with halothane-N2O and N2O-narcotic anesthesia. Abnormalities are found most frequently when patients are poorly responsive to verbal commands. Although their incidence diminishes with time, abnormal responses to neurologic examination may persist for 40 min or more after cessation of anesthesia.