Assessment of performance of NMT stimulators used during anaesthesia in the Czech Republic

Overview

Objective:
To assess the performance of NMT stimulators used during anaesthesia in the Czech Republic. To test the ability of the stimulators to work as “constant-current generators”.

Design:
Laboratory prospective controlled study

Setting:
Department of Anaesthesiology and Intensive Care, University Hospital and Palacky University, Olomouc.

Materials and Methods:
Six commercially available peripheral nerve stimulators were studied in laboratory settings. Each stimulator (single twitch mode, stimulating current 10, 20, 30, 40, 50 and 60 mA, respectively) was set to work at different loading resistance from 50 to 10000 Ohm. Based on the voltage measured on the load and Ohm’s law, the actual intensity of the current was determined. The loading characteristics were specified.The morphology of the stimulating pulse was recorded from the oscillographic screen. The stimulators were ranked from the best to the worst in each category.

Results:
The TOF-Guard^® (Biometer) and TOF-Watch^® SX (Organon) were the most accurate stimulators in terms of the stimulating current. All stimulators except the Innervator NS252^® (Fisher-Paykel) were less precise at higher currents (60 mA) than at lower stimulation intensities (10 mA). Multistim LA (Pajunk) showed the best impulse morphology; one of the stimulators (AS/3™, Datex-Ohmeda) offered both accelerometric and electromyograhic evaluation of muscle response.

Conclusion:
The manufacturers declare all the tested stimulators to be “constatnt-current generators”. Based on the test results, some of the stimulators did not meet this attribute because their output was load-dependent (ParaGraph^®, Vital Signs).

Key words:
neuromuscular transmission – peripheral nerve stimulator – monitoring – stimulation pattern