Background: Ketamine can enhance anesthetic and analgesic actions of a local anesthetic via a peripheral mechanism. The authors' goal was to determine whether or not ketamine added to ropivacaine in interscalene brachial plexus blockade prolongs postoperative analgesia. In addition, we wanted to determine the incidence of adverse-effects in patients undergoing hand surgery.
Methods: Sixty adults scheduled for forearm or hand surgery under the interscalene brachial plexus block were prospectively randomized to receive one of the solutions of the study. Group P received 0.5% ropivacaine 30 ml, group K received 0.5% ropivacaine 30 ml with 30 mg ketamine, and group C received 0.5% ropivacaine with 30 mg ketamine i.v. Loss of shoulder abduction, elbow flexion, wrist flexion and loss of pinprick in the C4-7 sensory dermatomes were assessed at 1-min intervals. Adverse-effects were assessed every 5 min. The duration of the sensory and motor blocks was assessed after operation. Adverse-effects were also recorded.
Results: The onset time of sensory or motor blockade and the duration of sensory or motor blockade were similar in all groups. Adverse-effects occurred in 44% of patients in group K and 94% of group C.
Conclusion: This study suggests that 30 mg ketamine added to ropivacaine in the brachial plexus block does not improve the onset or duration of sensory block, but it does cause a relatively high incidence of adverse-effects. These two findings do not encourage the use of ketamine with local anesthetics for brachial plexus blockade.