Effects of S(+) ketamine added to bupivacaine for spinal anaesthesia for prostate surgery in elderly patients.

BACKGROUND AND OBJECTIVE: Intrathecal ketamine as the sole anaesthetic agent has demonstrated a lack of cardiovascular depression that should be of advantage in an elderly population. S(+) ketamine has three-times the analgesic potency of R(-) ketamine and its antinociceptive effects after intrathecal administration in rats are known. We decided to evaluate the effects of intrathecal S(+) ketamine added to a small dose of spinal bupivacaine in elderly patients undergoing transurethral prostate surgery.

METHODS: Forty males over 60 yr old, scheduled for transurethral prostate resection under spinal anaesthesia, were studied in a prospective, double-blinded, randomized way. Patients were allocated to receive either bupivacaine 10 mg or bupivacaine 7.5 mg combined with S(+) ketamine 0.1 mg kg(-1). Spinal block onset time, maximum sensory level, duration of blockade, haemodynamic variables, postoperative analgesic requirements and adverse events were recorded.

RESULTS: Onset times of motor and sensory block were shorter in the bupivacaine plus S(+) ketamine group. Incomplete motor block of the lower extremities was seen in 80% of the patients in bupivacaine plus S(+) ketamine group. Duration of complete motor block and spinal analgesia was shorter in the bupivacaine plus S(+) ketamine group. There was no significant difference in arterial pressure. Heart rate decreased after spinal anaesthesia in the bupivacaine plus S(+) ketamine group and was significantly lower until the end of anaesthesia. The incidence of adverse effects was not different between groups.

CONCLUSIONS: Intrathecal S(+) ketamine administered with a low dose of bupivacaine provides shorter motor and sensory block onset time, shorter duration of action and less motor blockade in elderly males.