The optimal dose of ketamine for caudal epidural blockade in children.

Sixty boys aged up to 9 years undergoing orchidopexy were randomly allocated to receive one of three solutions for caudal epidural injection: group A received 1 ml.kg-1 of 0.25% bupivacaine with 0.25 mg.kg-1 of preservative-free ketamine, group B received 1 ml.kg-1 of 0.25% bupivacaine with ketamine 0.5 mg.kg-1 and group C received 1 ml.kg-1 of 0.25% bupivacaine with 1 mg.kg-1 of ketamine. Postoperative pain was assessed by means of a modified Objective Pain Score and analgesia was administered if this score exceeded four. The median duration of caudal analgesia was 7.9 h in group A, 11 h in group B and 16.5 h in group C. There were no differences between the groups in the incidence of motor block, urinary retention, postoperative vomiting or postoperative sedation. Group C had a significantly higher incidence of behavioural side effects, including slightly odd behaviour, vacant stares and abnormal effect than groups A and B.