Abstract Number ‐ 100: Hypothermia As A Therapy For Status Epilepticus: Systematic Review And Description Of A Novel Technique
Authors: Dammavalam Vikalpa 
Published: April 2023

Introduction
Refractory status epilepticus (RSE) is seizure lasting longer than 1 hour1 or response failure to one benzodiazepine and one AED2,3. Unfortunately, 30% of patients remain refractory to two AEDs and 15% to three AEDs4. Next line of therapy is intravenous anesthetic drugs (IVADs) which successfully control RSE in majority cases. Still, 15–35% of RSE progresses to super refractory status epilepticus (SRSE)1, defined as sustained seizure greater than 24 hours despite IVADs or recurrent seizure during IVAD weaning5,6. IVADs are associated with increased mortality due to adverse effects of respiratory depression, cardiac compromise and hypotension7. Therefore, alternative treatment such as focal hypothermia is being explored6. Older studies using ventricular irrigation8, extravascular irrigation9 and combination of local and systemic cooling10 demonstrated efficacy of focal cooling to suppress seizures. Recent literature describes use of focal cooling via thermoelectric devices for refractory focal epilepsy11. Choi et al. successfully trialed intracarotid cold saline infusions during cerebral angiography as an endovascular approach for focal hypothermia12. Chen et al. demonstrated the safety of intra‐arterial selective brain cooling in acute ischemic stroke13. This review summarizes studies demonstrating efficacy of hypothermia and introduces a novel technique for seizure suppression in SRSE.

Methods
Literature search of PubMed and Google Scholar was performed for hypothermia for SE. Variables such as etiology and type of SE, number of AEDs, anesthetic used, method to achieve hypothermia, target temperature, induction time, time at target temperature, time to rewarm and seizure response were extracted.

Results
Twelve out of 15 recruited studies used external cooling to achieve hypothermia while 2 studies with total 9 subjects used endovascular cooling. Corry et al. used endovascular cooling only while Ren et al. combined endovascular and external cooling, both used concurrent IVADs. Complications included shivering, post‐rewarming seizures, metabolic derangements, coagulopathy, thromboembolism, arrythmia, infection/sepsis and death collectively. Burst suppression or seizure cessation was achieved in all 9 patients. Outcomes ranged from discharged seizure‐free to poor Glasgow Outcome Scores.

Conclusions
Patients with SRSE may benefit from a trial of hypothermia. Although major complications of hypothermia were reported, concurrent use of IVADs may confound true morbidity of hypothermia alone. Currently available studies suggest an endovascular approach for focal hypothermia may be more effective, efficient and safer12‐15. Endovascular hypothermic cortical irrigation as a novel technique to abort refractory seizures may be a quicker therapeutic option with minimal adverse effects. In this technique, 4C cold heparinized saline is administered to the vascular territory of the epileptiform region as identified on intraoperative encephalography (EEG). Efficacy of treatment can be observed immediately as suppression or change of seizure activity on EEG. Focal hypothermia in the form of selective intra‐arterial treatment is a potential therapeutic target that needs further studies to validate its safety and feasibility.