Inadvertent Burst Suppression During Total Intravenous Anesthesia in 112 Consecutive Patients Undergoing Spinal Instrumentation Surgery: A Retrospective Observational Quality Improvement Project.

INTRODUCTION The incidence and quantification of inadvertent electroencephalographic burst suppression during total intravenous anesthesia (TIVA) for spine instrumentation surgery has not previously been reported. METHODS The primary aim of this retrospective observational quality improvement project was to establish the prevalence of burst suppression during spine instrumentation surgery with TIVA. The secondary outcome was the incidence of postoperative delirium. RESULTS One hundred twelve consecutive patients, aged between 20 and 88 years, underwent spinal instrumentation surgery. Seventy-eight (69.6%) patients experienced inadvertent burst suppression; the maximal degree of burst suppression ratio was 20% to 100%. Median (interquartile range [IQR]) time spent in burst suppression was 44 (77) minutes, and burst suppression was present for 22% (range: 2% to 93%) of the monitoring period. Average (±SD) propofol dose was lower in patients with burst suppression (87±19 vs. 93±15 µg/kg/min, P=0.04). Ten (8.9%) patients experienced postoperative delirium. Intraoperative burst suppression was more prevalent in those that experienced delirium (100% vs. 66.7%, P=0.03, relative risk: 1.5, 95% confidence interval: 1.3-1.7). The proportion of the monitoring period spent in maximal burst suppression (15.3 [25.9]% vs.11.7 [21.7]%) was similar between those that did, and did not, experience delirium. CONCLUSIONS High rates and prolonged periods of inadvertent burst suppression may be prevalent during spine instrumentation surgery with TIVA. Our findings suggest that usage of electroencephalography alone is incomplete without prompt interpretation and intervention, mandating close communication between neuromonitoring and anesthesia teams. The dose-response relationship between burst suppression, total time spent in maximal burst suppression, and their association with delirium warrants further evaluation.