The effect of spinal anesthesia with hyperbaric tetracaine and bupivacaine, with and without 1:1000 epinephrine were studied in 60 patients having perianal operation in the horizontal lithotomy position.

The 60 patients were divided into four groups(n=15 in each group). Patients in group I and II received 0.5% hyperbaric tetracaine 7 mg(1.4 ml) and normal saline 0.2 ml (group I) or epinephrine 0.2 mg (0.2 ml) (group II) and patients in group III and IV received 0.5% hyperbaric bupivacaine 7 mg (1.4 ml) and normal saline 0.2 ml (group III) or epinephrine 0.2 mg (0.2 ml) (group IV). After intrathecal injection, changes and durations of sensory block, motor block and anal tone block were checked.

The sensory block level was similar in four groups and the duration of analgesia was significantly longer in bupivacaine groups (III and IV) than in tetracaine groups (I and II) (in turn, group IV, II, III and I). Tetracaine groups were earlier onset of motor block, a larger number of patients with motor block and significantly longer duration of motor block than bupivacaine groups (in turn, group II, I, IV and III). The onset of anal tone block was earlier in tetracaine groups as the onset of motor block, but the duration of anal tone block was significantly longer in bupivacaine groups as the duration of analgesia (in turn, group IV, II, III and I). Epinephrine 0.2 mg produced significant prolongation of durations of analgesia, motor block and anal tone block of the hyperbaric tetracaine and bupivacaine. Cardiovascular change was similar in four groups and most common complication in all groups after spinal anesthesia was urinary retention.

We conclude that the hyperbaric tetracaine and bupivacaine are appropriate anesthetic agents for perianal surgery and epinephrine produce a significant prolongation of the postoperative analgesic duration in both anesthetic agents.