Intrathecal morphine reduces immediate pain after lumbar arthrodesis
Introduction
Lumbar arthrodesis (LA) is a frequent procedure with high level and extended postoperative pain. Several studies have demonstrated intrathecal morphine (IM) efficacy in reducing pain after LA. None has addressed pain in the recovery room. Controversy persist on the optimal dosage of IM. The aim of this study is to evaluate the efficacy of IM on pain in recovery room and compare the various schemas of administration.
Material and methods
This is a retrospective single center study. All patients who had lumbar arthrodesis between January 2012 and November 2016 were included. The patients were classified in IM group and no IM group. IM was administrated either prior or during surgery. The regimen of IM and multimodal analgesia were decided by the attending anesthesiologist. The main outcome was the proportion of patient requiring morphine titration in recovery room. The secondary end points were the rate of adverse effect of IM. The data were compared using Chi 2 test. Adjustment conducted using the Mantel Haenszel test. SPSS was used for statistics analyses and P value set at 0.05.
Results
431 patients have been included during the study period with 129 (30 %) in the IM group. Demographic data were comparable between the groups. The median dose of IM was 200 µg (100; 300).  IM reduces the rate of morphine titration in recovery room, odds ratio (OR) 2.95 (1.92; 4.57) (figure 1). After adjustment on multimodal analgesia modalities and the prior exposure to morphine, the OR is 2.35 (1.39; 3.95). When 200 µg IM was administrated before surgery, the OR is 5.38 (2.08; 13.90). No adverse effect occurred in recovery room. 2 patients required bladder evacuation on day 1 and 2 leakage of CSF occurred at day 2 in IM group.
Discussion
IM reduces the need of morphine in recovery room. This is more prominent when the IM is administrated before surgery at the dose of 200 µg. Usually, for LA, IM is administrated by the surgeon at the end of surgery with an efficiency up to four hours after surgery (1). The median dose of IM was 200 µg with no adverse effect in recovery room. Boezaart and al has demonstrated the safety of dose up to 300µg (2).
Conclusion 
IM may reduce the need of morphine in the recovery room after LA. IM should be administrated before surgery at the dosage of 200 µg.
1. S Ziegeler, E Fritsch and al. Therapeutic Effect of Intrathecal Morphine After Posterior Lumbar Interbody Fusion Surgery A Prospective, Double-Blind, Randomized Study. Spine 33; 22; 2379 –2386. 
2. A Boezaart; J Eksteen and al.Intrathecal morphine : double-blind evaluation of optimal dosage for analgesia after major lumbar spinal surgery. spine 24;11; 1131-1137