Recovery from pre-operative sedation with clonidine--brain stem auditory evoked response

In a randomised double-blind study, 34 elderly patients (ASA grades 1-2) underwent elective intra-ocular surgery. Patients were allocated randomly to two groups to receive oral clonidine 300 micrograms or oral diazepam 10 mg 2 h before surgery. Facial block and retrobulbar block were given at 2 h after premedication. Anaesthetic recovery was assessed using a clinical recovery score (at 0, 30, 60 and 120 min after arrival in the recovery room) and brain stem auditory evoked potential responses (BAER) (immediately after operation and at 120 min after operation). In both the groups the clinical recovery scores decreased significantly at 30 and 60 min following recovery (p < 0.01). At 120 min this score returned to the pre-operative value in the clonidine group, but in the diazepam group there was a significant difference between the 2h value and pre-operative value (p < 0.05). In the clonidine group there was no significant rise in the interpeak latencies and absolute peak latencies of brain stem auditory evoked responses recorded immediately after operation and 120 min after operation. In the diazepam group, there was a significant rise in the interpeak latencies immediately after operation and 120 min after operation and a rise in absolute peak latencies (p < 0.05) immediately after operation. In the clonidine group there was a reduction (p < 0.05) in amplitude of wave V at immediately after operation. We conclude that clonidine 300 micrograms orally before surgery does not delay recovery.