Intrathecal Morphine For Postoperative Analgesia In Posterior Lumbar Spine Decompression And Instrumentation : A Comparative Study Of Two Different Doses.

Objectives : To compare the analgesic efficacy of two different doses of intrathecal morphine 0.2 and 0.3 mg in posterior lumbar spine decompression and instrumentation surgery and to assess side effects and total consumption of opioids in 24 hrs postoperatively.

Study Design : Randomized, double blind exploratory trial.

Site : Dr. B.L.Kapur Memorial Hospital, New Delhi.

Methods : Forty patients were randomly assigned to receive morphine intrathecally either 0.2 mg (Group A, n=20) or 0.3 mg (Group B, n=20) in 2 ml saline before general anaesthesia. A morphine patient controlled analgesia (PCA) device was provided as rescue in postoperative period. Morphine use, pain relief and side effects were recorded for 24 hr. Data for categorical variables were presented as percentages and compared using chi square test. Continuous variables presented as mean±SD or median. The t-test to compare the numeric variables and Mann-Whitney U test to compare ordinal variables.

Result : The values on the numerical rating scale for pain in Group B were significantly lower than those in Group A at 4, 8 and 12 hr after operation (p<0.05). The mean morphine consumption in 24 hrs was lower in Group B. There was no significant difference between the groups in other studied parameters.

Discussion : In a meta-analysis of many studies, it was seen that the degree of analgesia was better with intrathecal morphine than with other analgesic techniques such as i.v. low dose ketamine, a regimen of postoperative non-steroidal anti-inflammatory drugs and even continuous epidural infusion technique.

Conclusion : 0.3 mg ITM provided superior analgesia postoperatively and higher patient satisfaction compared with 0.2 mg with no significant difference in the incidence of side effects.