Optimization of the nose of intrathecal morphine in total hip surgery: A dose-finding study

We designed this study to determine the optimal intrathecal dose of morphin e in total hip surgery. The optimal intrathecal dose was defined as that pr oviding effective analgesia and minimal side effects 24 h after total hip s urgery. Patients (n = 143) scheduled for total hip surgery were randomized to four double-blinded groups with a standardized bupivacaine dose but diff erent doses of intrathecal morphine (Group I = 0.025 mg, Group II = 0.05 mg , Group III = 0.1 mg, and Group IV = 0.2 mg). Pain scores, IV morphine inta ke (patient-controlled analgesia), and morphine-related side effects (respi ratory depression, postoperative nausea and vomiting, itching, urinary rete ntion) were recorded for 24 h after surgery. Excellent postoperative pain r elief was present in all groups. The highest pain scores were found in Grou p I. The mean use of systemic morphine administered by patient-controlled a nalgesia infusion pump was 23.7, 17.8, 10.9, and 9.9 mg in Groups I-IV, res pectively (P < 0.01 for Groups III and TV versus Group I). We conclude that 0.1 mg of intrathecal morphine is the optimal dose for pain relief after h ip surgery with minimal side effects. Implications: Earlier studies showed excellent postoperative pain relief after intrathecal morphine. However, th e severity of side effects resulted in decreased enthusiasm for this anesth esia technique. In the present study, we show that an intrathecal dose of 0 .1 mg of morphine can be used safely in total hip surgery with excellent po stoperative pain relief.