Intraoperative Neuromonitoring to Predict Development of Post Operative Delirium Following Ruptured and Unruptured Aneurysm Clipping Surgery

Introduction: Post-operative delirium(POD) affects 20% of intracranial surgical patients and 42.2% of Neurosurgery Intensive Care Unit patients; it can lead to doubled length of hospital stay, doubled nursing hours, five times the mortality risk, and three times the cost. Thus, early detection and intervention intraoperatively can be critical. A key precipitating factor for delirium is alteration of cerebral blood flow(CBF). However, all current CBF monitoring methods are either non-continuous or extremely invasive and increase risk. During vascular surgeries, like aneurysm clipping, the major cause of intraoperative neuromonitoring(IONM) changes are decrease in CBF. Continuous electroencephalography(EEG) or somatosensory evoked potentials(SSEP) could offer a possible alternative CBF monitoring method. The aim was to determine the diagnostic accuracy of both modalities for predicting POD incidence after aneurysm clipping.

Methods: IONM and clinical data from 470 patients undergoing aneurysm clipping were retrospectively reviewed. Delirium was assessed using the Intensive Care Delirium Screening Checklist(ICDSC) and the International Classification of Diseases(ICD9/10). Significant IONM changes were evaluated based on visual review of SSEP/EEG data and documentation of changes.

Results: Of 470 patients, 115(24.5%) were diagnosed with POD and 35(30.4%) had IONM changes. After adjusting for confounders, IONM and SSEP changes were significantly associated with POD (OR 2.4 (CI 1.40-4.17); P=0.002, OR 2.49 (CI 1.39-4.45); P = 0.002, respectively). We also found that odds of POD were higher in patients with ruptured aneurysms and those who developed focal neurological deficits(FND) post-operatively (OR 2.76,1.72-4.42; P< 0.001, OR 2.11,1.02-4.36,P=0.04, respectively).

Conclusion : Patients with POD after aneurysm clipping are twice as likely to have significant IONM or SSEP changes. Patients with ruptured aneurysms or who develop post-operative FND are more than twice as likely to develop POD. IONM could function as a non-invasive, continuous, proxy CBF measure and allow for timely interventions to improve outcomes. Our findings offer a strong basis for further research of IONM as a standard monitoring procedure to prevent POD incidence.