Identification of factors associated with morbidity and post-operative length of stay in surgically managed chronic subdural haematoma using electronic health records: a retrospective cohort study

INTRODUCTION Chronic subdural haematoma (cSDH) tends to occur in older patients, often with significant comorbidity. The incidence and effect of medical complications as well as the impact of intraoperative management strategies are now attracting increasing interest. OBJECTIVES We used electronic health record data to study the profile of in-hospital morbidity and examine associations between various intraoperative events and postoperative stay. DESIGN, SETTING AND PARTICIPANTS Single-centre, retrospective cohort of 530 cases of cSDH (2014-2019) surgically evacuated under general anaesthesia at a neurosciences centre in Cambridge, UK. METHODS AND OUTCOME DEFINITION Complications were defined using a modified Electronic Postoperative Morbidity Score. Association between complications and intraoperative care (time with mean arterial pressure <80 mm Hg, time outside of end-tidal carbon dioxide (ETCO2) range of 3-5 kPa, maintenance anaesthetic, operative time and opioid dose) on postoperative stay was assessed using Cox regression. RESULTS 53 (10%) patients suffered myocardial injury, while 24 (4.5%) suffered acute renal injury. On postoperative day 3 (D3), 280 (58% of remaining) inpatients suffered at least 1 complication. D7 rate was comparable (57%). Operative time was the only intraoperative event associated with postoperative stay (HR for discharge: 0.97 (95% CI: 0.95 to 0.99)). On multivariable analysis, postoperative complications (0.61 (0.55 to 0.68)), anticoagulation (0.45 (0.37 to 0.54)) and cognitive impairment (0.71 (0.58 to 0.87)) were associated with time to discharge. CONCLUSIONS There is a high postoperative morbidity burden in this cohort, which was associated with postoperative stay. We found no evidence of an association between intraoperative events and postoperative stay.