Spearman's Rank Correlation Matrix for Preoperative, Perioperative, and Postoperative Study Variables Including Predictors, Confounders and Outcomes.

Spearman's rank correlation coefficients for all pairs of preoperative, perioperative, and postoperative study variables including predictors, confounders and outcomes. Total n for the pairwise correlations with pre- and intraoperative variables is 42. For postoperative pain-related outcomes any pairwise correlation has a total n of 32 with the exception of morphine (n = 42) and persistent postoperative pain at six months (POD 180) (n = 15). Coefficients with significance levels of 0.05 or less are printed in bold.
STAI  =  state part of the Spielberger's State Trait-Anxiety Inventory; BDI  =  Beck's Depression Inventory; PPT 1 =  pressure pain threshold (test pain before cold pressor test); PPT 2 =  pressure pain threshold (test pain after 120 s cold pressor test); kPa  =  kilopascal; Cold pain detection  =  time to pain detection during cold pressor test; Cold pain tolerance  =  total hand immersion time during cold pressor test; CPTP  =  worst pain intensity associated with cold pressor test; CPTU  =  worst unpleasantness associated with cold pressor test; NRS 0–10 = 11-point numerical rating scale; CPM  =  conditioned pain modulation (i.e., difference between PPT 1 and PPT 2); S-PCS  =  the Situational Pain Catastrophizing Scale administered in connection with cold pressor test; Epidural analgesia  =  total intraoperative dose of 0.25% bupivacaine + morphine, 50 µg ml−1; Fentanyl  =  total dose of intraoperative fentanyl; PAR  =  postoperative pain at rest (POD 2–5); MEP  =  postoperative movement-evoked pain (POD 2–5); Morphine  =  postoperative morphine consumption (POD 2–5); Integrated analgesic assessment score  =  a composite measure of movement-evoked pain intensity and morphine consumption: Pain intensity scores and morphine consumption for each patient were rank ordered, subtracted from the mean rank, expressed as a percentage difference from the mean rank and added together (i.e., pain rank score + morphine rank score) to yield and integrated analgesic assessment score (ranging anywhere from −200 to +200%; with the highest positive score indicating the most pain); Pain at POD 180 was assessed according to response to the question: “Please rate your pain by circling the one number that best describes your pain on the average” from the Brief Pain Inventory – Short Form (BPI). The BPI rates worst, average, current, and least pain using simple numeric rating scales (NRS) ranging from 0 to 10, where 0 =  no pain and 10 =  the worst pain imaginable.