High dose intrathecal morphine for major abdominal cancer surgery: a prospective double-blind, dose-finding clinical study.

BACKGROUND

Despite 30 years of clinical research, we still do not know the optimal dose of intrathecal morphine (ITM) when used alone.

OBJECTIVES

A safety investigation and comparison of the analgesic efficacy of ITM 0.2 mg, 0.5 mg, and 1 mg in patients undergoing major abdominal cancer surgery.

STUDY

DESIGN

A randomized, double-blind trial.

SETTING

Academic medical center.

METHODS

Ninety patients were randomly assigned to receive morphine intrathecally either 0.2 mg (Group I, ITM 0.2 mg, n = 30), 0.5 mg (Group II, ITM 0.5 mg, n = 30), or 1 mg (Group III, ITM 1 mg, n = 30) dissolved in 5 mL physiological saline before general anesthesia. Assessment parameters included hemodynamics, respiratory rate, peripheral arterial oxygenation, sedation score, pain severity, time of first analgesic request, total analgesic consumption, and side effects in the first 72 hours.

RESULTS

The mean time to first request for rescue analgesia was significantly prolonged in Group II (22.13 ± 5.21 hours, P < 0.001) and Group III (30.83 ± 4.89 h, P < 0.001), compared with Group I (0.50 ± 0.66 hours). The mean tramadol consumption dose was significantly reduced in Group II (383.33 ± 91.28 mg, P < 0.001) and Group III (300 ± 69.48 mg, P < 0.001) compared with Group I (770 ± 114.92 mg). Patients received 1 mg ITM showed lower VAS scores in the first 48 h postoperative (P < 0.04) compared with Group I and Group II. No significant differences were observed in the mean systolic and diastolic blood pressure values, respiratory rate, and peripheral arterial oxygen saturation between groups. Lower mean heart rate values were observed in Group III patients at 6 hours (P < 0.01) and 12 hours (P < 0.03) postoperative compared with Group I and Group II patients. Six patients (20%) in Group II and 8 (26.7%) in Group III exhibited pruritus compared with 2 patients (6.66%) in Group I (P < 0.01). No intergroup statistical differences were observed for other studied side effects.

LIMITATIONS: This study is limited by its small sample size.

CONCLUSION

One mg ITM provided superior analgesia for 48 hours postoperative compared with 0.2 mg and 0.5 mg ITM with a nonsignificant difference in the incidence of side effects. Further studies of larger sample size are recommended to confirm these findings.