Sex-related differences of patient-controlled epidural analgesia for postoperative pain

Gender differences in pain modulation are evident but data are rare with regard to perioperative regional analgesia. The aim of the present analysis was to assess gender-related differences in pain ratings, analgesic consumption, and adverse events in a large group of patients treated with patient-controlled epidural analgesia (PCEA) after major surgery. Data from 14,988 adult patients (6506 women; 8482 men) receiving a PCEA between January 1998 and December 2009 were examined. Demographic data and postoperative measurements assessed by the Acute Pain Service, including total PCEA consumption, pain scores, and complications, were analyzed by using PASW Statistics (18.0; SPSS Inc, Chicago, IL, USA). Beyond standard descriptive analyses, gender-related differences were investigated using a stepwise multivariate analysis of variances. Postoperative pain scores during rest and movement were almost equal between men and women. However, women showed lower total PCEA consumption consistently throughout the 5-day observation period (relative reduction by 1.7%-10.2% compared to men; P=0.00). Total PCEA consumption did not interact with surgical site (abdomen, thorax, extremity) (P=0.379) or age (<50, 50-75, >75 years; P=0.330), but was influenced by body mass index (P=0.017) and vomiting (P=0.011). Furthermore, motor blockade was greater in females compared to males (P=0.000). In patients treated with PCEA, gender differences in numeric rating scale scores exist but are not clinically relevant. However, reduced total PCEA consumption in women might be a consequence of an increased incidence of motor blockade and vomiting; the latter point towards an opioid-free PCEA solution in female patients at high risk for vomiting.