Regional blockade in patients with a history of a seizure disorder

Systemic local anesthetic toxicity is a potential complication in patients undergoing regional anesthesia, particularly during procedures requiring large doses of local anesthetic, such as epidurals, caudals, and peripheral nerve blocks. It is unknown whether patients with a history of a seizure disorder are at an increased risk of central nervous system toxicity (seizures) after local anesthetic administration.

We retrospectively reviewed the medical records of all patients with documented history of a seizure disorder who underwent epidural, caudal, or peripheral nerve block from January 1, 1988 to December 31, 2001. Patient demographics, character of the seizure disorder, details of the regional procedure, and seizure activity in the perioperative period were recorded. The rate of seizure due to local anesthetic toxicity per 10,000 anesthetics was estimated using a point estimate and corresponding 95% confidence interval (CI).

During the 14-yr study period, 411 procedures in 335 patients with a seizure disorder were identified. Twenty-four patients experienced postoperative seizure activity. The timing of the most recent (preoperative) seizure was found to be significantly related to the likelihood of experiencing a postoperative seizure (P < 0.001). Based on the extended time interval between local anesthetic injection and/or termination of the infusion and the event, it was determined that the regional anesthetic was neither the primary etiology nor a contributing factor for the seizure in 19 of the 24 patients. In the remaining five patients, perioperative seizure activity was characteristic of their usual seizures. Although unlikely to be the cause of the seizure, local anesthetic toxicity could not be absolutely excluded as a contributing factor to the event in these five patients. Assuming that none of the seizures was related to local anesthetic toxicity the estimated incidence is 0 per 10,000 (95% CI 0-89 per 10,000). Conversely, if the seizures were related to local anesthetic toxicity in the five cases, the incidence is increased to 120 per 10,000 (95% CI 40-280 per 10,000).

We conclude that majority of seizures occurring in the perioperative period in patients with a preexisting seizure disorder are likely related to the patient's underlying condition and that regional anesthesia in these patients is not contraindicated. Furthermore, because the likelihood of a postoperative seizure is increased in patients with a recent seizure, it is essential to be prepared to treat seizure activity, regardless of the anesthetic and analgesic technique.