• Edward Andrew Ochroch, Anil Vachani, Allan Gottschalk, and Peter A Kanetsky.
• Department of Anesthesiology and Critical Care, Division of Pulmonary and Critical Care, University of Pennsylvania, PA 19104, USA. ochrocha@uphs.upenn.edu
• Clin J Pain. 2012 Nov 1; 28 (9): 747-54.

ObjectivesThe mechanism whereby acute postsurgical pain can persist and become chronic remains unknown. Thoracotomy is a common procedure with a high incidence of long-term pain for which acute postsurgical pain is an established risk factor. Therefore, the genetic basis of elevations in acute postsurgical pain after thoracotomy was investigated.MethodsA cohort of thoracotomy patients participating in an ongoing trial of outcomes after cancer were enrolled. A standard combined general and epidural anesthetic and surgical approach were used. All patients received a standardized postoperative epidural analgesia regimen. Postoperatively, pain scores were determined and blood was collected for genotyping. Our a priori hypothesis was that variability of genes involved in nociception and analgesic therapy would predict pain score ≥3 of 10 on the third postoperative day.ResultsNinety patients with pain and genotyping data on postoperative day 3 were examined. We found no association between markers in COMT, COX1, COX2, and TRPV1 and postoperative pain. We demonstrated several statistically significant associations with 4 single nucleotide polymorphism markers in OPRM1 (odds ratio, 95% confidence intervals): rs634479 (0.4, 0.17, 0.97), rs499796 (0.35, 0.13, 0.92), rs548646 (0.47, 0.23, 0.97), and rs679987 (0.1, 0.01, 0.84). From these, we inferred 2 haplotype blocks in OPRM1 where both had a frequency of 9% and P=0.03 and 0.04. Previously published functional single nucleotide polymorphisms in OPRM1 and COMT were not associated with increased pain on the third postoperative day.DiscussionWe identified previously unpublished haplotypes of the OPRM1 receptor that predicted increases in self-reported pain on the third postoperative day after thoracotomy. These findings require replication and further refinement before their impact on patient care can be determined.

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