In Reply:—
We thank Dr. Pollard for his interest in our work. Cardiac arrest was defined as requiring cardiac massage and/or epinephrine. We are happy to provide the following information, which will partly respond to his questions. Because of the uncontrolled nature of the study, it is obvious that information may have been incomplete or may not have been precisely recorded at the time the events occurred, so it might not exactly represent the patients’ situation at the time of cardiac arrest. Analysis of the details contained in table 1should thus be made with caution.
Table 1. Patients’ Characteristics at the Time of Cardiac Arrest Occurring during Spinal Anesthesia
ASA = American Society of Anesthesiologists; HB = hyperbaric; PACU = postanesthesia care unit.
Further comments that can be added are that (1) the factors involved in cardiac arrest were several, and (2) the risk probably increases from the start of the procedure to its end as the number of factors causing hemodynamic instability superimpose on those previously present. Cardiac arrest may occur early because a large dose of local anesthetic can be aggressive enough to trigger the unwanted event in a previously hypovolemic patient (due to a combination of denutrition, preoperative fasting, and antihypertensive treatment in most cases), and several patients noted in table 1clearly received “large” doses of local anesthetic. In other patients, cardiac arrest occurs more “lately” when the patient becomes unable to cope with the additional factor that is inflicted: hemorrhage, cementing, or position change. The patient's underlying hemodynamic reserve delays or accelerates the occurrence of the complication. As it is often clinically difficult to precisely evaluate both the degree of preoperative hypovolemia and the patient's hemodynamic reserve, it is suggested that special attention should be given to correct rapidly all factors that might lead by themselves to decompensation or which may reduce the safety margin and “make the bed” for a complication to occur at the time an additional aggression is being given. Limited or incremental dosing of the spinal anesthesia, intraoperative measurement of hemoglobin concentration, and monitoring of cardiovascular function are among the clinically available means to decrease the incidence of mortality or significant complications after spinal anesthesia.
