The Surgical Apgar Score in Hip and Knee Arthroplasty

A 10-point Surgical Apgar Score, based on patients' estimated blood loss, lowest heart rate, and lowest mean arterial pressure during surgery, was developed to rate patients' outcomes in general and vascular surgery but has not been tested for patients having orthopaedic surgery. For patients undergoing hip and knee arthroplasties, we asked (1) whether the score provides accurate risk stratification for major postoperative complications, and (2) whether it captures intraoperative variables contributing to postoperative risk based on the three parameters independent of preoperative risk. We retrospectively reviewed the electronic records for all 3511 patients who underwent a hip or knee arthroplasty from March 2003 to August 2006 and extracted data to calculate a Surgical Apgar Score. We evaluated the relationship between scores and likelihood of major postoperative in-hospital complications and assessed its discrimination and calibration. Complication rates increased monotonically as the score decreased. Even after controlling for preoperative risk, each 1-point decrease in the score was associated with a 34.0% increase (95% confidence interval, 0.66-0.84) in the odds of a complication. The overall discriminatory performance of the score was a c-statistic of 0.61. Seventy-six percent of all major complications occurred in patients classified as low risk with scores of 7 or greater. For patients undergoing hip and knee arthroplasties, the score captures important intraoperative information regarding risk of complications and contributes additional information to preoperative risk, but on its own is insufficient to provide comprehensive postoperative risk stratification for arthroplasties. Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.