Patients with epilepsy require special attention from anesthesiologists. They may require anesthesia in otherwise routine procedures, such as dental restorations or imaging studies [1]. Anti-epileptic medications (AEMs) can produce various pharmacologic and physiologic effects that impact anesthesia [2]. Additionally, many anesthetics have been reported to have proconvulsant effects, meaning that care must be taken to avoid abrupt intraoperative seizures that could complicate surgery [3]. Understanding the relationship between epilepsy and anesthesia is crucial to ensuring the best possible outcome for affected patients.
Generally, AEMs facilitate inhibitory or suppress excitatory neurological signals [4]. While first and second-generation AEMs can both result in adverse side effects, the second generation is generally deemed safer and less likely to interact with other drugs [2]. Regardless, medical teams must assess patients’ preoperative AEM levels to avoid and prepare for any adverse AEM-anesthesia interactions [4]. Because AEMs can affect metabolic enzymes, they may invoke resistance to aminosteroid non-depolarizing neuromuscular blockers (NMBs) [4]. Postoperative prescriptions should be tailored to consider that certain drugs can risk AEM toxicity by increasing AEM serum concentration [4]. Conversely, enzyme-inducing AEMs may interact with other drugs to reduce the latter’s serum concentration [4].
Another important consideration is the anticonvulsive effects of anesthesia in certain contexts. Anesthetics can act as anticonvulsants when administered at the level required to induce general anesthesia [4]. Thiopental is a safe and effective anesthetic that can be used to counter bouts of convulsive status epilepticus (CSE) [4]. Propofol can also be administered intraoperatively to suppress epileptic events [4]. However, the recordings central to interoperative electrocorticography (ECoG) may be obscured when patients are under the influence of anticonvulsants [3]. Therefore, medical teams performing ECoGs must manage patients’ anticonvulsant levels while avoiding intraoperative seizures.
Certain anesthetics can also increase the risk of seizures when administered at low levels [4]. Indeed, drugs such as ketamine, etomidate, and methohexital are proconvulsant and anticonvulsant, depending on dosage [5]. Other medications can promote epileptic episodes when combined with others [5]. For example, inhalational agents (such as isoflurane, halothane, desflurane) are not proconvulsive when administered alone [5]. To avoid epileptic events during procedures, anesthesia providers can consider using morphine and hydromorphone [3]. These drugs have not been shown to induce convulsions when applied at clinically relevant doses [3].
In the event of an intraoperative seizure, there are various remedies that physicians can turn to. If a seizure occurs during neurosurgery, particularly intraoperative ECoG, studies suggest that sterile ice-cold saline should be placed onto the cortex [3]. This method is useful during ECoG because it can minimize the effect of suppression on brain recordings [3]. If the intraoperative seizure is tonic-clonic, anticonvulsive anesthetics or thiopental medications may be needed [3]. If the patient has experienced more than five minutes of continuous seizure activity, ketamine may also be effective against CSE if other anesthetics fail to resolve the event [4].
Given the variety of considerations that anesthesia providers must account for when treating epileptic patients, emphasis must be placed on monitoring anesthetic levels and AEM treatments before, during, and after surgery. The presurgical evaluation is essential to gauge the anesthetics that are safe to use during the procedure in question [6].
References
[1] W. H. P. Ren, “Anesthetic Management of Epileptic Pediatric Patients,” International Anesthesiology Clinics, vol. 47, no. 3, p. 101-116, July 2009. [Online]. Available: https://doi.org/10.1097/AIA.0b013e3181ac2539.
[2] A. W. Kofke, “Anesthesia management of the patient with epilepsy or prior seizures,” Current Opinion in Anaesthesiology, vol. 23, no. 3, p. 391-399, June 2010. [Online]. Available: https://doi.org/10.1097/ACO.0b013e328339250b.
[3] J. Chui et al., “The anesthetic considerations of intraoperative electrocorticography during epilepsy surgery,” Anesthesia and Analgesia, vol. 117, no. 2, p. 479-486, August 2013. [Online]. Available: https://doi.org/10.1213/ANE.0b013e318297390c.
[4] E. L. Carter and R. M. Adapa, “Adult epilepsy and anaesthesia,” BJA Education, vol. 15, no. 3, p. 111-117, June 2015. [Online]. Available: https://doi.org/10.1093/bjaceaccp/mku014.
[5] A. Shetty et al., “Anesthesia considerations in epilepsy surgery,” International Journal of Surgery, vol. 36, part B, p. 454-459, December 2016. [Online]. Available: https://doi.org/10.1016/j.ijsu.2015.07.006.
[6] J. Chui, “Presurgical Evaluation of Patients with Epilepsy: The Role of the Anesthesiologist,” Anesthesia & Analgesia, vol. 116, no. 4, p. 881-888, April 2013. [Online]. Available: https://doi.org/10.1213/ANE.0b013e31828211af.