Correlation of higher preoperative American Society of Anesthesiology grade and increased morbidity and mortality rates in patients undergoing spine surgery

OBJECT: Patients with varied medical comorbidities often present with spinal pathology for which operative intervention is potentially indicated, but few studies have examined risk stratification in determining morbidity and mortality rates associated with the operative treatment of spinal disorders. This study provides an analysis of morbidity and mortality data associated with 22,857 cases reported in the multicenter, multisurgeon Scoliosis Research Society Morbidity and Mortality database stratified by American Society of Anesthesiologists (ASA) physical status classification, a commonly used system to describe preoperative physical status and to predict operative morbidity. METHODS: The Scoliosis Research Society Morbidity and Mortality database was queried for the year 2007, the year in which ASA data were collected. Inclusion criterion was a reported ASA grade. Cases were categorized by operation type and disease process. Details on the surgical approach and type of instrumentation were recorded. Major perioperative complications and deaths were evaluated. Two large subgroups--patients with adult degenerative lumbar disease and patients with major deformity--were also analyzed separately. Statistical analyses were performed with the chi-square test. RESULTS: The population studied comprised 22,857 patients. Spinal disease included degenerative disease (9409 cases), scoliosis (6782 cases), spondylolisthesis (2144 cases), trauma (1314 cases), kyphosis (831 cases), and other (2377 cases). The overall complication rate was 8.4%. Complication rates for ASA Grades 1 through 5 were 5.4%, 9.0%, 14.4%, 20.3%, and 50.0%, respectively (p = 0.001). In patients undergoing surgery for degenerative lumbar diseases and major adult deformity, similarly increasing rates of morbidity were found in higher-grade patients. The mortality rate was also higher in higher-grade patients. The incidence of major complications, including wound infections, hematomas, respiratory problems, and thromboembolic events, was also greater in patients with higher ASA grades. CONCLUSIONS: Patients with higher ASA grades undergoing spinal surgery had significantly higher rates of morbidity than those with lower ASA grades. Given the common application of the ASA system to surgical patients, this grade may prove helpful for surgical decision making and preoperative counseling with regard to risks of morbidity and mortality.