Abstracts

Rationale: Burst suppression is frequently used to monitor depth of anesthesia, and in treatment of status epilepticus. However, there is no consensus on what neurophysiological measures should be used to define optimal burst suppression, and little is known about how pharmacologically induced burst suppression patterns vary with age. The primary objective of this study was to determine if there was a consistent relationship between the duration of a burst and the overall burst suppression ratio in patients who are treated with pharmacological burst suppression as part of neurosurgical anesthesia. Our secondary objective was to determine if age affected the relationship between burst duration and burst to suppression ratio. Methods: We retrospectively reviewed EEG records that were used to monitor depth of anesthesia in patients undergoing neurosurgery at our institution. Patients' age ranged from 8 to 84, with both males and females included. Data was collected from representative samples of intra-operative EEG tracings done between 1/1/2005 and 5/1/2012 to total 56 EEGs. The first portion of the EEG with burst suppression was identified and the burst length, suppression length, number of bursts per minute, and overall ratio of burst to suppression were recorded. A quadratic regression spline was used to model the relationship between burst duration and the overall suppression ratio. Results: There was a direct relationship between burst duration and overall burst suppression. There was also a trend towards younger patients having longer bursts and longer periods of suppression for a given burst suppression ratio. Conclusions: There is a direct relationship between burst duration and burst/suppression duration ratio, showing that either burst duration or burst/ to suppression ratio can be used to guide clinical management in most patients. There was a trend of decreasing burst duration with increasing age for a given ratio, suggesting that caution should be used in the pediatric population as burst duration may underestimate the burst suppression ratio in children.