British Journal of Anaesthesia, 1990, Vol. 64, No. 1 28-32
© 1990 The Board of Management and Trustees of the British Journal of Anaesthesia
research-article |
A SIMPLIFIED APPROACH TO THE EFFECT KINETICS OF ATRACURIUM
School of Physiology and Pharmacology and the School of Surgery of the University of New South Wales
Department of Anaesthesia and Resuscitation, School of Physiology and Pharmacology and the School of Surgery of the University of New South Wales
*Address for correspondence: Department of Anaesthesia and Intensive Care, Prince Henry Hospital, Little Bay, NSW 2036, Australia.
The combination of the Hill equation, which describes the concentration—effect relation, with the monoexponential function for the terminal decline of plasma concentration, yields a compound time constant, 
. This constant is a combination of the terminal elimination half-life (
) and the exponent (s) of the Hill equation and may be used to describe the time course of recovery from neuromuscular block. The constant may be estimated by non-linear curve fitting to f, the effect expressed as fraction of maximal effect, or by linear regression of the logit function of f. The methods were validated using plasma concentration and effect data from seven patients administered atracurium. The two methods utilizing effect data alone yielded values of 4.2 (0.7) min and 4.3 (0.5) min (mean (SEM)), respectively, for compared with 4.1 (0.6) min when the constant was calculated using plasma concentration data for and curve fitting to the concentration—effect data to determine s. These methods offer and objective measure of the rate of recovery and a means of testing if redistribution or elimination is the primary process in the termination of drug effect.