Spinal anesthesia for arthroscopic knee surgery.

BACKGROUND AND OBJECTIVE

The purpose of the study was to compare the effects of adding 50 microg of morphine, 25 microg of fentanyl or saline to 6 mg of hyperbaric bupivacaine on postoperative analgesia and time to urination in patients undergoing arthroscopic knee surgery under spinal anesthesia.

METHODS

The study was designed in a prospective, randomized, double-blinded and placebo-controlled manner. Sixty ASA I-II patients were randomized into the following three groups: Group BM: 6 mg of bupivacaine and 50 microg of morphine, Group BF: 6 mg of bupivacaine and 25 microg of fentanyl, and Group BS: 6 mg of bupivacaine and saline. Selective spinal anesthesia was performed in a lateral decubitus position, with the operative knee dependent for 10 min.

RESULTS

In all groups satisfactory anesthesia was provided during the operation. There was a statistically significant difference between all the groups in times to voiding [Group BM 422 +/- 161 min; Group BF 244 +/- 163 min; Group BS 183 +/- 54 min (mean +/- SD)]. The incidence of pruritus was significantly greater in Group BM (80%) and BF (65%) in comparison with Group BS (no pruritus) (P < 0.05). The incidence of nausea was significantly increased in Group BM (35%) in comparison with Group BF (10%) and Group BS (P < 0.05). Analgesic consumption was significantly greater in Group BS in comparison with Groups BM and BF (P < 0.01).

CONCLUSIONS

We conclude that during spinal anesthesia even mini-dose intrathecal morphine is not acceptable for outpatient surgery due to side-effects, especially severely prolonged time to urination.