An observational study and clinical trial of the neuromuscular blocker advisory system

Terence Gilhuly1,2, Bernard MacLeod1, Guy Dumont2, Stephan Schwarz1. 1Department of Pharmacology and Therapeutics, 2Department of Electrical and Computer Engineering, University of British Columbia, Vancouver, British Columbia, Canada. 2176 Health Sciences Mall, Vancouver, BC V6T 1Z3 Canada.

The Neuromuscular Blocker Advisory System (NMBAS) is a computer program developed to provide advisory guidance to anesthesiologists on the timing and dose of drug used to paralyze patients during surgery. NMBAS implements rudimentary computer-control with estimation of drug levels based on observed effect to formulate a recommendation. This is meant as a stepping-stone towards full computer controlled neuromuscular blockade (NMB).

The objective of this work is to test the NMBAS in a clinical setting, under the hypothesis that this system will administer the minimal effective NMB drug, and will thereby improve patient safety and result in more efficient use of medical resources. This presentation describes an observational study to gather data for the initial patient model and the planned prospective randomized clinical trial protocol. The protocol was approved by the institutional Human Ethics Boards and informed consent was obtained for all procedures.

Neuromuscular response and blockade observations were recorded from fourteen human patients undergoing prostate brachytherapy procedures under general anesthesia. Patients were male, of average age 61.9 years and American Society of Anethesiologists physical status class I to III. After the patient was anesthetized, rocuronium was administered according to the attending anesthesiologist's judgement and at or below the manufacturer's recommended dosage of 0.6mg/kg. Patients then underwent their scheduled procedure without interference. There were no complications and physiological parameters were maintained within physiological norms. Estimations of patient response were formed from the observed train-of-four (To4) data, using a sixth order Laguerre model. Modelling of response included data from the first rocuronium injection until the next NMB related drug - rocuronium or reversant – was given. Error between the measured data and the estimated responses varied from 4.8 to 14% with a mean of 8.5+/-3.2%. The patient response estimates were averaged to form the average response to be used as the patient model in the clinical trial of the NMBAS.