Postoperative morbidity index: a quantitative measure of severity of postoperative complications

Background: Postoperative complications are key outcomes of surgical procedures, but currently there is no uniform quantitative measure of complication severity. The purpose of this study was to evaluate and establish feasibility of quantitative morbidity scores for several common abdominal surgical procedures.

Study design: Using American College of Surgeons' National Surgical Quality Improvement Program data, complications were identified in 5 common abdominal procedures for one institution in 2005-2008, including inguinal hernia, appendectomy, laparoscopic colectomy, hepatectomy, and pancreaticoduodenectomy. Complications were graded by the 6-level "expanded" Accordion Severity Grading System. Quantification was performed using severity scores described previously.

Results: Six hundred and seventy-six procedures were identified, including 88 patients (13.84%) who had complications and 5 patients (0.79%) who died. After severity weighting, the postoperative morbidity index (PMI) for each procedure was derived. An index of 0 would indicate no complication in any patient and an index of 1.000 would indicate that all operated patients died. PMIs were hernia repair 0.005; appendectomy 0.031; laparoscopic colectomy 0.082; hepatectomy 0.145; and pancreaticoduodenectomy 0.150. PMI of hepatectomy was greatly affected by the presence of a second procedure, ie, 0.070 without a second procedure and 0.427 with a second procedure. Weighted severity spectragrams were developed, portraying the impact of each grade of complication on overall morbidity.

Conclusions: Quantification of severity of postoperative complications is possible using American College of Surgeons' National Surgical Quality Improvement Program methods and the Accordion Severity Grading System. Procedural PMI can be useful in assessing surgical outcomes. Certain limitations, particularly the need for risk adjustment, still need to be addressed.