Preemptive analgesia for postoperative pain relief in lumbosacral spine surgeries: a randomized controlled trial.

BACKGROUND CONTEXT: Administration of analgesic medication, before the actual onset of painful stimulus, is more effective than that after the onset of painful stimulus. This is the principle of preemptive analgesia. Although it is often considered superior to other forms of analgesia, its role in postoperative pain relief after lumbosacral spinal surgery has not been fully investigated.

PURPOSE: To analyze the efficacy of preemptive analgesia with a single caudal epidural injection for patients undergoing surgeries on the lumbosacral spine by the posterior approach.

STUDY DESIGN/SETTING: Randomized, double-blinded and controlled clinical trial.

PATIENT SAMPLE: Eighty-two patients who underwent discectomy in the lumbosacral spine by the posterior approach, with or without instrumentation, were randomized to the control group (n=40) and to the study group (n=42).

METHODS: Patients in control group received a single caudal epidural injection of 20 ml of normal saline. Patients in study group received a single caudal epidural injection of 20 ml containing bupivacaine and tramadol as the active agents. The time interval between this injection and the surgical incision was never less than 20 minutes in either of the groups. This facilitated enough time for the drug to get fixed to the nerve roots, leading to effective preemptive analgesia.

OUTCOME MEASURES: Patients were monitored for postoperative pain immediately after surgery when they had completely recovered and regained consciousness from general anesthesia, and subsequently 4, 8, 12 and 24 hours thereafter. Pain was quantified using the visual analog scale (VAS) and the verbal rating scale (VRS). The time at which supplemental analgesic medication was first demanded in the postoperative period by the patient was also noted.

RESULTS: The two groups were comparable for age, sex, body weight and the type of surgery they underwent. Because the data did not have a normal Gaussian distribution, the one-tailed Mann-Whitney test, being a nonparametric test, was adopted for statistical analysis. Accordingly, VAS and VRS values at all time intervals were significantly lower (p<.0001) in the study group as compared with the control group. This indicated significantly better pain relief in the study group. There was also a significant delay (p=.0041) in the first demand for supplemental analgesic medication in the postoperative period in the study group. No complication specific to the procedure was noted except for the development of postoperative urinary retention, which was transient and appropriately managed with urinary catheterization.

CONCLUSIONS: Preemptive analgesia with a single caudal epidural injection of bupivacaine and tramadol is a safe, simple and effective method for postoperative pain relief.