Intrathecal morphine provides better postoperative analgesia than psoas compartment block after primary hip arthroplasty.

Abstract

Intrathecal morphine and psoas compartment block represent two accepted techniques to provide postoperative analgesia after hip arthroplasty. We designed a prospective, randomized, single-blinded study to compare these two techniques. Patients scheduled for primary hip arthroplasty under general anesthesia were randomized to receive either an intrathecal administration of 0.1 mg morphine (Group I, n = 27) or a psoas compartment block with ropivacaine 0.475% 25 mL (Group II, n = 26). Pain scores, morphine consumption, associated side-effects were assessed for 48 hr postoperatively. In addition, patient's acceptance and satisfaction of the postoperative analgesic technique were also recorded. During the first 24 hr, pain scores (3.3 +/- 9.6 mm vs 22.8 +/- 27.1 at H+6, 3.3 +/- 8.3 mm vs 25 +/- 26.7 mm at H+12, 7 +/- 14.9 mm vs 21.9 +/- 29 mm at H+18) and morphine consumption (0.56 +/- 2.12 mg vs 9.42 +/- 10.13 mg) were lower in Group I than in Group II. Urinary retention was the more frequent side-effect occurring in 37% of cases in Group I vs 11.5% in Group II (P < 0.05). No major complication occurred. Despite better analgesia provided by the use of intrathecal morphine, there was no difference in the satisfaction scores between groups. 0.1 mg intrathecal morphine administration provides better postoperative analgesia than single-shot psoas compartment block after primary hip arthroplasty.