Postoperative analgesia after radical prostatectomy with high-dose intrathecal morphine and intravenous naloxone: a retrospective review

Abstract

Background and methods: Intrathecal opioids (ITOs) have been used for decades to control postoperative pain. Intrathecal opioid dosing is limited, however, by opioid-related side effects, most importantly respiratory depression. To overcome these limitations, we combined intrathecal morphine with a continuous intravenous (IV) postoperative naloxone infusion to control opioid-related side effects. The purpose of this study is to document the efficacy and safety of high-dose intrathecal morphine combined with postoperative naloxone infusion to provide postoperative analgesia after major surgery. After IRB approval, a retrospective chart analysis was performed on 35 patients who had a radical prostatectomy from 2004 to 2006. All patients received a single injection of ITOs before anesthesia, a typical general Anesthestic, followed by naloxone infusion at 5 microg/kg/h started 1 hour post-ITOs and continued for 22 hours postoperatively. The following information was collected: patient age, height, weight, anesthesia technique/time, and dose of ITOs given. Postoperative pain relief was assessed for 48 hours using the Visual Analog Score (VAS) for pain (0, no pain; 10, worst pain), perioperative opioid use, NSAID consumption, and ability of patient to ambulate. The safety of this novel treatment was assessed with opioid-related side effects and vital signs. All data are reported as mean (SD).

Results: Mean ITOs given were morphine 1.3 (0.3) mg combined with fentanyl 56 (9) microg. The intrathecal morphine dose ranged from 0.8 to 1.7 mg. The mean worst pain VAS in the first 12 hours postoperatively was only 1.0 (1.7). The first NSAID dose was given 6.6 (3.1) hours post-ITOs. The first opioid on the floor was given an average of 22.6 (14.5) hours post-ITOs. A mean of only 5.7 (12.3) morphine equivalents were required on postoperative day 1 (POD 1). On POD 2, the mean worst pain VAS was only 2.6 (2.2) with only 5.7 (6.2) morphine equivalents needed to provide pain relief On POD 1, 25patients required no additional opioids for their entire hospital stay. Overall, 11 of 35 patients did not require any additional postoperative opioids. Thirty-four patients (97 percent) were able to ambulate in the first 12 hours postoperatively. No opioid-induced respiratory depression was observed. Opioid-related side effects (pruritus, nausea) were infrequent and minor.

Conclusions: High-dose ITOs combined with postoperative IV naloxone infusion provided excellent analgesia for radical prostate surgery. IV naloxone infusion appeared to control opioid side effects without diminishing the analgesia. No serious adverse effects were noted.