Abstracts

Rationale: Recently there has been an increased interest with a therapeutic role of moderate to deep hypothermia in refractory status epilepticus. On the other hand, epileptiform discharges and electrographic seizures have been reported in patients undergoing cardiovascular surgery using deep hypothermic circulatory arrest (DHCA). The main objective of this study is to examine the prevalence and timing of electrographic seizures and interictal activation during aortic arch repair surgeries using DHCA as detected by continuous intraoperative encephalogram (IOEEG and correlate it with outcome).The second goal of this study was to define IOEEG changes occurring at specific temperature points of cooling and rewarming.Methods: Cases were identified through a query of our electronic EEG report system. 32 patients were then randomly selected from a core group of patients consisting 132 patients who underwent ascending aorta and/or aortic arch reconstructive surgery using DHCA between 2012 and 2014. Preoperative patient characteristics, intraoperative data including IOEEG changes at specific temperature points during cooling and rewarming as well as postoperative neurologic outcomes were reviewed. IOEEGs were graded based on the frequency of epileptiform discharges (grade 1 or grade 2) and/or the presence of electrographic seizure (grade 3).Results: Epileptiform activation was seen in 30/32 cases. Grade 1 and grade 2 activations were more prominent during cooling at nasopharyngeal temperature of 23.9 ± 4.01oC (mean ± SDV) and ranging from 16.8-33.4oC (p<0.01). These activations occurred at mean nasopharyngeal temperature of 23.9 ± 4.01oC (mean ± SDV). In the majority of cases the epileptiform discharges appeared at a nasopharyngeal temperature below 28°C. Electrographic seizures occurred in six patients and were exclusively seen during cooling at temperatures below 280 C (Figure 1). The mean seizure duration was 195 ± 205 seconds (mean ± SDV) and ranged 35 - 637 seconds. No patient developed postoperative clinical neurologic deficit or seizures. Good neurologic outcome at hospital discharge was seen in 30 patients (93.8%).There was no statistical correlation between IOEEG grade and mortality, or between the occurrence of neurological complications and duration of circulatory arrest.Conclusions: Robust epileptiform activation occurred in almost all cases during induction of deep hypothermia. This activation was much less commonly seen during restoration of normothermia. These alterations were not associated with postoperative neurologic deficit or Clinical neurophysiologists, technicians and surgeons need to be aware that these discharges are common during this procedure, yet have no apparent clinical significance and do not appear to require therapeutic intervention. Caution is required in interpreting and relating the findings of studies involving refractory status against ours which examined the effect of hypothermia in a brain that was not seizing at the inception of hypothermia.