Thermal quantitative sensory testing to predict postoperative pain outcomes following gynecologic surgery

Abstract

Objective: To evaluate the relationship of preoperative thermal quantitative sensory testing (QST) values with postoperative pain and opiate consumption in opiate-naïve patients following gynecologic surgery. Design: Single blind observational study. Settings: Surgical center of an academic medical center. Methods: QST was performed preoperatively on 124 opioid-naïve patients. Pain outcomes were assessed on arrival to the post-anesthesia care unit and at 6 hourly intervals for 24 hours. Subjects were reclassified to three groups: Group 1 had a heat pain threshold above and a cold pain threshold below the median; Group 2 had either a heat pain threshold below or a cold pain threshold above the median; Group 3 had a heat pain threshold below and a cold pain threshold above the median. The primary outcome measure was the 24-hour morphine consumption. Results: One hundred twenty subjects were evaluated. Median (interquartile range) warm and cold pain thresholds were 44.8 (42.4-46.9)°C and 10.5 (3.2-19.0)°C, respectively. Heat pain thresholds demonstrated a negative (rho=-0.23, P=0.01) and cold thresholds a positive correlation (rho=0.21, P=0.02) with 24-hour morphine consumption. Median morphine consumption was 19 (2-33) mg (P=0.004) equivalents greater in subjects (N=46) with heat pain thresholds <45°C and cold pain thresholds >10°C than subjects with heat pain thresholds >45°C and cold pain thresholds <10°C. Discussion: Reduced tolerance to both heat and cold thermal pain stimulus was associated with increased postoperative analgesic requirements. Combined responses to multiple pain modalities may be more useful than a single stimulus paradigm. © 2014 American Academy of Pain Medicine.