Onset Time of Neuromuscular Block as a Function of the Period of Baseline Stabilization

Abstract

In Response: We would like to thank Dr. Kopman for his interesting and important observations on our study examining the onset of neuromuscular block [1]. The influence of the duration of anesthesia including the use of nitrous oxide may well be important and is being investigated. Nitrous oxide, however, with its low blood-gas solubility, equilibrates rapidly and would have influenced the results in the groups with shorter periods of control stimulation. Our results showed a progressive reduction in the onset time throughout the period of study. Although the influence of an increase in muscle temperature may affect the electromyographic recordings [2], there is no evidence at present about its influence on evoked twitch tension. Moreover, the authors of this study commented that "the correlation between the EEMG response and the muscle temperature in the study may be coincidental." There may be many reasons for the increase in muscle blood flow, including the duration of control stimulation and the duration of anesthesia itself prior to administration of the relaxant, but whatever the cause, both Dr. Kopman and we agree that standardization of these variables would make for better comparison of data from different investigators. The mechanisms of increase in the blood flow to the muscle itself need further investigation. E. P. McCoy, FFARCSI R. K. Mirakhur, MD F. M. Connolly, FFARCSI P. B. Loan, FRCA Department of Anaesthetics, The Queen's University of Belfast, Belfast, Northern Ireland