Effects of patient and surgery characteristics on persistent postoperative pain: A mediation analysis

Objective: Acute postoperative pain intensity is associated with persistent postsurgical pain risk. However, it remains unclear whether acute postoperative pain intensity mediates the relationship between clinical factors and persistent pain. Methods: Subjects from a mixed surgical population completed the Brief Pain Inventory and pain catastrophizing scale before surgery, and the Brief Pain Inventory daily after surgery for 7 days and at 30 and 90 days after surgery. We considered mediation models using the mean of the worst pain intensities collected daily on each of postoperative days (PODs) 1 to 7 against outcomes of worst pain intensity at the surgical site endpoints reflecting persistent postsurgical pain (POD 90) and subacute pain (POD 30). Results: The analyzed cohort included 284 subjects for the POD 90 outcome. For every unit increase of maximum acute postoperative pain intensity through PODs 1 to 7, there was a statistically significant increase of mean POD 90 pain intensity by 0.287 after controlling for confounding effects. The effects of female vs. male sex (m=0.212, P=0.034), pancreatic/biliary vs. colorectal surgery (m=0.459, P=0.012), thoracic cardiovascular vs. colorectal surgery (m=0.31, P=0.038), every minute increase of anesthesia time (m=0.001, P=0.038), every unit increase of preoperative average pain score (m=0.012, P=0.015), and every unit increase of catastrophizing (m=0.044, P=0.042) on POD 90 pain intensity were mediated through acute PODs 1 to 7 postoperative pain intensity. Discussion: Our results suggest the mediating relationship of acute postoperative pain on persistent postsurgical pain may be predicated on select patient and surgical factors.