Awareness with Recall During General Anesthesia

Abstract

In Response: Dr. Metz addresses the important issue of muscular relaxation and awareness during general anesthesia. Indeed, the use of neuromuscular blocking drugs seems to be a prerequisite for awareness and recall [1,2]. Only very few case reports of awareness without paralysis have been published [3,4]. In our recent study, there were three patients with possible awareness in whom muscle relaxants were not used [5]. However, these were all patients with very unspecific memories, and their recollections may have originated in the recovery room or may even have been illusions or hallucinations. The data regarding the use of muscle relaxants in the study material [5] are shown in Table 1. Several relaxants were used during the study. In the database of 554 anesthetic records that we used for the analysis, atracurium was used for 63.2% of cases, succinylcholine for 10.8%, vecuronium for 3.4%, pancuronium for 1.4%, and rocuronium for 0.2%. We created a Table in which we summed all relaxants as either used or not used. The Table wasanalyzed with Yates corrected chi squared statistics, as the expected frequencies in the group of patients with awareness were low.Table 1: The Use of Muscle Relaxants Versus Awareness with RecallThere was no statistically significant difference in the frequency of use of muscle relaxants. However, when only patients with objective intraoperative memories are considered (Groups 2 and 3 in the original study), all the patients with awareness received muscle relaxants, and there seems to be a trend toward the use of relaxant drugs among patients with awareness. In the original study, we used a regression model to measure the statistical significance of the various anesthetics used. We believe that one must interpret the data of a frequency Table very cautiously because the dosing of the drugs does not play any role in such a table. However, we strongly agree with Dr. Metz that muscle relaxants should be used as sparingly as possibly so as to give the anesthetized patient an opportunity to signal awareness by movement. Seppo O-V Ranta, MD Department of Anaesthesia; Children's Hospital; Helsinki University; FIN-00290 Helsinki, Finland Markku Hynynen, MD Department of Anaesthesia and Intensive Care; Jorvi Hospital; FIN-02740 Espoo, Finland