Effects of different doses of epidural midazolam on spinal somatosensory evoked potentials

The aim of this study is to find out the effects of different doses of midazolam, when used epidurally, on somatosensory evoked potentials (SEP) by delaying neuronal conduction. Thirty two New Zeland albino male rabbits were divided into four groups. All rabbits were anesthetised with ketamine and xylasine combination and atracurium was used as muscle relaxant. 10 mg/kg/hr ketamine infusion was used for maintenance of anesthesia. After insertion of the epidural catheter surgically; Group 1 received 1.5 ml isotonic saline (Control), Group 2 received 150 mu g/kg, Group 3 received 250 mu g/kg, and Group 4 received 500 mu g/kg midazolam epidurally. With the stimulation of sciatic nerve, SEP records were recorded From the epidural space. Records were received before the injection of the drug, and 20, 40, 60 minutes after injection of the drug. Latancy results were increased according to control in all groups (including isotonic saline-control-group). Increase in latancy in the control group was interpreted as due to the effect of temperature mismatch of the saline and the rabbits. While in the first and second group amplitudes showed no differences, group 3 and 4 showed decreases of up to 50%. Epidurally administered midazolam up to 150 mu g/kg caused no change in SEP records, but 250 and 500 mu g/kg doses caused decreases in SEP records which can lead to misinterpretation as neurological damage.