Risk Analysis Index as a preoperative frailty tool for elective ventriculoperitoneal shunt surgery for idiopathic normal pressure hydrocephalus

Abstract

OBJECTIVE Idiopathic normal pressure hydrocephalus (iNPH) predominantly occurs in older patients, and ventriculoperitoneal shunt (VPS) placement is the definitive surgical treatment. VPS surgery carries significant postoperative complication rates, which may tip the risk/benefit balance of this treatment option for frail, or higher-risk, patients. In this study, the authors investigated the use of frailty scoring for preoperative risk stratification for adverse event prediction in iNPH patients who underwent elective VPS placement. METHODS The Nationwide Readmissions Database (NRD) was queried from 2018 to 2019 for iNPH patients aged ≥ 60 years who underwent VPS surgery. Risk Analysis Index (RAI) and modified 5-item Frailty Index (mFI-5) scores were calculated and RAI cross-tabulation was used to analyze trends in frailty scores by the following binary outcome measures: overall complications, nonhome discharge (NHD), extended length of stay (eLOS) (> 75th percentile), and mortality. Area under the receiver operating characteristic curve analysis was performed to assess the discriminatory accuracy of RAI and mFI-5 for primary outcomes. RESULTS A total of 9319 iNPH patients underwent VPS surgery, and there were 685 readmissions (7.4%), 593 perioperative complications (6.4%), and 94 deaths (1.0%). Increasing RAI score was significantly associated with increasing rates of postoperative complications: RAI scores 11–15, 5.4% (n = 80); 16–20, 5.6% (n = 291); 21–25, 7.6% (n = 166); and ≥ 26, 11.6% (n = 56). The discriminatory accuracy of RAI was statistically superior (DeLong test, p < 0.05) to mFI-5 for the primary endpoints of mortality, NHD, and eLOS. All RAI C-statistics were > 0.60 for mortality within 30 days (C-statistic = 0.69, 95% CI 0.68–0.70). CONCLUSIONS In a nationwide database analysis, increasing frailty, as measured by RAI, was associated with NHD, 30-day mortality, unplanned readmission, eLOS, and postoperative complications. Although the RAI outperformed the mFI-5, it is essential to account for the potentially reversible clinical issues related to the underlying disease process, as these factors may inflate frailty scores, assign undue risk, and diminish their utility. This knowledge may enhance provider understanding of the impact of frailty on postoperative outcomes for patients with iNPH, while highlighting the potential constraints associated with frailty assessment tools.