Continuous Morphine Infusion: A Retrospective Study of Efficacy, Safety, and Demographic Variables

Neuromodulation. 2009 Apr;12(2):122-9. doi: 10.1111/j.1525-1403.2009.00206.x.

Abstract

Objectives. This study aims to assess the efficacy of intrathecal infusion in different types of pain. A number of different variables were assessed to analyze their effect on therapy and to determine in which patients intrathecal infusion is more effective. Materials and Methods. A retrospective study was conducted with data obtained from 1983 to 2002. During this period, 292 intrathecal morphine tests were performed, with positive results in 205 cases. Eight nonprogrammable intrathecal pumps and 205 programmable pumps were implanted. One hundred and thirty-one programmable pumps were studied in which the drug used was morphine alone. Efficacy and side-effects were analyzed in the overall sample, depending on the type of pain, gender, age (20-40, 40-64, > 65), and dose of morphine used (< 2, 2-4.9, 5-14.9, > 15). Results. All results are expressed as median and interquartile range (p25-p75) because the data had a nonnormal distribution. The patients' mean age was 61 years (range 50-70 years); there were 61 men (46.6%) and 70 women (53.4%). The most commonly reported pain types were cancer pain (64, 48.9%), neuropathic pain (51, 38.9%), and nociceptive pain (16, 12.2%). Test dose used was 0.4 mg/day (0.2-0.7), and mean number of test days was 6 days (range 4-9 days). The initial morphine dose was 0.50 mg (0.30-1.45), mean dose was 2.70 mg (1.25-6.20), and the final dose was 4 mg (0.0-47). The initial numerical rating scale score of 8 (8,9) decreased to 4 (3-8) and 2 (1-5) at the end of the study. The overall rate of complications was 35.35%. Relief was very good in 29 (50.4%), good in 66 (22.1%), fair in 20 (15.3%), and poor in 16 (12.2%) patients. Univariate analysis. (Morphine): Gender: Male 49/58 (84.48%) vs. Female 43/65 (66.15%), RR 1.27 (1.04-1.57), p = 0.02 (chi-squared). No significant differences were found in the other variables studied (age and type of pain). The multivariate analysis (logistic regression analysis) revealed a significant difference with regard to gender, with an odds ratio of 2.78 in favor of male gender. When the efficacy and safety of the infusion was compared to the dose of morphine used, no significant differences were observed, with p = 0.65 for efficacy and p = 0.69 for safety. Conclusions. Pain relief was obtained with this technique in approximately 70% of patients, with no differences between pain types, but with a significant difference in favor of male gender.