Interactions Between Pulmonary Performance and Movement-Evoked Pain in the Immediate Postsurgical Period: Implications for Perioperative Research and Treatment Jason Erb, M.D., Elizabeth Orr, R.N., C. Dale Mercer, M.D., F.R.C.S.C., and Ian Gilron, M.D., M.Sc., F.R.C.P.C. Background and Objectives: Previous data suggest that movement-evoked pain is more closely correlated with pulmonary performance than rest pain beyond 24 hours following lower abdominal surgery. Because adverse alterations in lung physiology are initiated intraoperatively and impact upon pulmonary morbidity, this study tests the hypothesis that movement-evoked pain correlates negatively with pulmonary performance in the immediate postoperative period. Methods: We measured pain at rest and pain evoked by sitting, forced expiration, and coughing as well as peak expiratory flow (PEF), forced expiratory volume in 1 second, and forced vital capacity for the first 3 hours after laparoscopic cholecystectomy in 65 patients. Results: Immediately after surgery, all pain measures were significantly correlated with PEF with a medium effect size. Also, sitting-evoked pain and cough-evoked pain were significantly more intense than rest pain. Pain intensity improved significantly over the first 3 postoperative hours. Conclusions: Considering these and previous results, pulmonary function tests such as PEF should be considered for more routine use as functional surrogates of movement-evoked pain in analgesic trials of thoracic and abdominal surgery. Mechanisms of immediate postoperative movement-evoked pain may differ from those in effect at later time points after which tissue inflammation and spinal sensitization develop. Because pain adversely impacts upon postoperative rehabilitation, these results further imply that aggressive treatment of movement-evoked pain could improve the outcome of postoperative rehabilitation measures if both are implemented very early after surgery. Reg Anesth Pain Med 2008;33:312-319. Key Words: Surgical pain, Postoperative complications, Central sensitization, Peripheral sensitization, Hyperalgesia, Respiratory physiology. O ver 40 million surgeries are performed in North America per year and moderate to severe post- surgical pain occurs in over half of these. 1,2 While postoperative pain itself is an important source of morbidity, 3 evidence also exists to suggest that pain is an important contributor to adverse outcomes follow- ing surgery. 4,5 One important condition in which pain, and treatment thereof, may affect adverse out- comes is that of postoperative lung dysfunction. 6 Post- operative lung dysfunction has long been recognized as a multifactorial condition affected by intraoperative body position, general anesthesia, muscle relaxation, and endotracheal positive-pressure ventilation, as well as postoperative pain. 7-9 The development of postoperative pain measure- ment scales initially focused on the assessment of spontaneous pain or pain at rest. 10,11 However, in- corporation of measures of “movement-evoked” pain or pain during normal activities (e.g., sitting, breathing, or coughing) has gradually become a more common research practice, 12,13 although this is not homogeneously done across all current post- From the Departments of Anesthesiology (J.E., E.O., I.G.), Surgery (C.D.M.), and Pharmacology and Toxicology (I.G.), Queen’s Univer- sity and Kingston General Hospital, Kingston, Ontario, Canada. Accepted for publication January 16, 2008. This work was supported by Physicians’ Services Incorporated Foundation Grant number 03-30 and Queen’s University Grant number 383-861. Ian Gilron is supported by a Canadian Insti- tutes of Health Research New Investigator Award. The authors have no conflict to declare. Reprint requests: Ian Gilron, M.D., M.Sc., F.R.C.P.C., Depart- ments of Anesthesiology and Pharmacology & Toxicology, Queen’s University, Kingston General Hospital, 76 Stuart St., Kingston, Ontario K7L 2V7, Canada. E-mail: gilroni@post. queensu.ca © 2008 Published by Elsevier Inc. on behalf of the American Society of Regional Anesthesia and Pain Medicine. 1098-7339/08/3304-0001$34.00/0 doi:10.1016/j.rapm.2008.01.003 312 Regional Anesthesia and Pain Medicine, Vol 33, No 4 (July–August), 2008: pp 312–319