The Utility of the 5 Factor Modified Frailty Index in Outcome Prediction for Patients with Chronic Subdural Hematoma Treated with Surgical Drainage

Abstract

Increasing frailty is a significant determinant of perioperative morbidity and mortality within neurosurgical literature. This study investigates the predictive value of the modified frailty index 5 (mFI-5) for postoperative morbidity and mortality following surgical drainage of chronic subdural hematoma (cSDH). A retrospective cohort study was performed on patients who underwent surgical evacuation of a cSDH. The mFI-5 score was calculated for each patient and used to stratify patients: prefrail (mFI-5<2), frail (mFI-5=2), and severely frail (mFI-5>2). Multivariate Cox proportional hazards (CPH) regression analysis were used to identify factors associated with our primary outcomes: overall survival and 30-day readmission. Secondary outcomes included nonhome discharge, length of stay, hematoma accumulation, development of new postoperative neurologic deficits, resolution of preoperative neurologic deficits, and a modified Rankin score >2 at discharge. 118 patients with a mean age of 74.4±11.9 years were analyzed. All baseline demographics were similar across the 3 groups. On multivariate analysis, severely frail patients (N= 24, 20.3%) had increased rates of 30-day readmission (hazard ratio [HR] 4.3, CPH regression P value<0.001) and postoperative mortality (HR 3.1, CPH regression P value<0.01) compared to the prefrail cohort. Severely frail patients had increased rates of nonhome disposition (HR 9.6, CPH regression P value< 0.001), development of new postoperative neurologic deficits (HR 2.75, CPH regression P value=0.03), and hematoma reaccumulation (HR 4.07, CPH regression Pvalue=0.004). A novel scoring system accounting for patient age and frailty was predictive of 90-day mortality (area under the curve 0.77). Frailty, measured by the mFI-5, and our novel scoring system hold a predictive value regarding outcomes for patients undergoing surgical drainage of a cSDH.