Efficacy of Low-Dose Intrathecal Morphine for Postoperative Analgesia After Abdominal Aortic Surgery: A Double-Blind Randomized Study

Abstract

Several studies suggest that intrathecal morphine (ITM) improves analgesia after aortic surgery. We tested the hypothesis that in combination with multimodal postoperative pain management, low-dose ITM associated with general anesthesia would decrease postoperative analgesic requirements in patients undergoing abdominal aortic surgery. Thirty patients were randomized to receive either general anesthesia alone or preceded by low-dose ITM (0.2 mg) administration. Patients and providers were blinded to treatment. Postsurgical multimodal pain management was similar in both groups, including parenteral paracetamol, followed by intravenous nefopam and then morphine if not sufficient. Intravenous analgesic requirements, visual analog scale (VAS) scores, and the incidence and severity of side effects were recorded for 48 hours after surgery. Intraoperative data were comparable between the 2 groups, except sufentanil consumption, which was significantly lower in the ITM group when compared with the control group (P = .023). ITM decreased postoperative total-morphine requirements with respect to both the number of patients who received morphine (4 v 12 patients, P = .003) and the cumulative dose of morphine administered (0 [0-12.4] v 23 [13.9-45.6] mg, P = .006). VAS scores at rest were higher in the control group than in the ITM group at awakening (P < .01), at 4 hours (P < .01) after surgery, and at 8 hours (P < .05) after surgery but did not differ between groups after this period. Whereas VAS scores on coughing were higher in the control group at awakening (P < .01) and 4 hours after surgery (P < .05), no differences were found between groups from 8 hours after surgery. In patients undergoing abdominal aortic surgery, intrathecal morphine (0.2 mg) improves postoperative analgesia and decreases the need in intraoperative and postoperative analgesics. Further studies are indicated to evaluate the role of ITM in postoperative recovery.