To the Editor:—
I read with great interest the article by Drs. Liu and McDonald published in the May 2001 issue of Anesthesiology. 1They report that the incidence of cardiac arrest during spinal anesthesia is from 1/10,000 to 1/250,000 cases. Their own references do not support these incidences. They reference Auroy et al. who reported 26 cardiac arrests in a prospective study of 40,640 spinal anesthetics for an incidence of 1/1600 cases. 2The other reference cited is also problematic because it was a study of insurance claims for damages following anesthesia. 3Since only a small fraction of adverse events lead to claims for damages, this greatly underestimates the true incidence of these arrests. Other studies confirm a cardiac arrest rate during spinal anesthesia of close to 1/1000 cases. 4–6
Having more accurate information about the incidence of cardiac arrest during spinal anesthesia is important because it makes it clear that this problem is common enough to warrant more attention. Further proof of the immediacy of this problem comes from the observation that there are now more claims in the American Society of Anesthesiologists (ASA) Closed Claims Database for cardiac arrest during spinal or epidural anesthesia (170 cases), than there are for aspiration related injury. 7The severity of injury has remained high with death or brain damage in approximately 90% of these claims.
It is important to emphasize that the worst outcomes may be avoided if patients receive appropriate treatment. 5,8Often this treatment should include use of a strong vagolytic agent. Liu and McDonald acknowledge that there can be a shift in cardiac autonomic balance toward the parasympathetic system related to a sudden decrease in volume. 1They also allude to increases in baroreflex activity but there is no mention of the potential benefits of vagolytic therapy during spinal anesthesia. The first two prophylactic measures that they discussed can help decrease vagal tone partially, but may be inadequate by when used alone. Gratadour et al 9reported that neither volume loading nor infusion of a mixed α- and β-agonist during spinal anesthesia was sufficient to prevent three study patients from experiencing bradycardia and hypotension associated with an increase in baroreflex activity. To help prevent an overwhelming vagal response, prophylactic treatment with atropine should also be considered for patients at risk for severe bradycardia and cardiac arrest during spinal anesthesia. With the popularity of spinal anesthesia and the reported frequency of these arrests, increased use of all three of these interventions to decrease vagal tone could enhance the safety of spinal anesthesia.