Associations between Heat Pain Perception and Opioid Dose among Patients with Chronic Pain Undergoing Opioid Tapering

Objective. The purpose of this study was to investigate the associations between morphine equivalent dose and heat pain (HP) perception in patients with chronic pain undergoing opioid tapering in the context of a multidisciplinary rehabilitation program.Design. Prospective design.Setting. Multidisciplinary pain rehabilitation center.Patients. The cohort included 109 patients using opioids (female 52%) who met inclusion criteria, and were consecutively admitted from March 2007 to June 2008.Intervention. Three-week outpatient multidisciplinary rehabilitation program that incorporates opioid tapering.Outcome Measures. Using a standardized quantitative sensory test (QST) method of levels, standardized values of HP perception were obtained one day following program admission and following completion of the opioid taper at program dismissal.Results.At admission, the mean morphine equivalent dose was 192mg/day. Univariate linear regression analysis showed that greater baseline morphine equivalent dose was associated (P=0.040) with lower, or more hyperalgesic, values of HP 5-0.5, which is a standardized measure of HP perception. The dose dependent association retained significance (P=0.029) after adjusting for pain severity, pain duration and pain diagnosis. Tapering of greater morphine equivalent dosages was associated (P=0.001) with lower values of HP 5-0.5. The association retained significance (P=0.001) after adjusting for pain severity, pain duration, pain diagnosis, opioid withdrawal symptoms, and time between completion of the taper and performance of the dismissal QST.Conclusion. The use of a validated QST method of levels and standardized values of HP 5-0.5 may expand the methodological approaches available for investigating the clinical effects of opioids on HP perception.