Comparison between acceleromyography and visual assessment of train-of-four for monitoring neuromuscular blockade in horses undergoing surgery.
OBJECTIVE
To compare acceleromyography (AMG) with visual assessment of train-of-four (TOF) for monitoring neuromuscular blockade and detecting residual muscle paralysis in horses receiving atracurium.


METHODS
Prospective, controlled clinical study.


METHODS
Nine adult, client-owned horses weighing 577 (436, 727) kg (median, minimum, maximum) and ASA physical status I-II, admitted for surgery.


METHODS
An electrical nerve stimulator was used to stimulate the peroneal nerve with TOFs at 1 minute intervals. Before and after atracurium administration (0.15 mg kg(-1), IV), the number of twitches observed (TOF count, or TOFc) was assessed visually. When four twitches were seen (i.e., TOFc = 4) presence or absence of fade by visual assessment was recorded. Simultaneously, the response to each TOF was assessed by AMG; this measured TOFc, and twitch fade using TOF ratio (TOFR; ratio of fourth to first twitch). The anesthetist performing the visual evaluation was blinded to the AMG readings. Recovery from neuromuscular blockade was defined as the absence of fade by visual inspection or a TOFR > or =90% by AMG.


RESULTS
During onset of action of the drug, fade was first detected 4 (1, 8) minutes earlier by AMG (p = 0.008). Maximal blockade started at 6 (3, 17) minutes by visual assessment and 9 (3, 25) minutes by AMG (not significantly different). Only four horses achieved complete neuromuscular blockade (TOFc of zero by both methods); in those four horses AMG did not detect the start of the return of neuromuscular transmission before visual assessment. Visual assessment indicated the return of four twitches with no fade 12 (8, 42) minutes before AMG gave a TOFR of > or =90% (p = 0.004).


CONCLUSIONS
There was no substantial advantage for AMG in detecting the onset of atracurium-induced neuromuscular blockade. However, AMG detected residual blockade when visual assessment of TOF did not. Application of AMG is likely to reduce the incidence of residual blockade.
Martin-Flores
Manuel
M
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA. mm459@cornell.edu
Campoy
Luis
L
Ludders
John W
JW
Erb
Hollis N
HN
Gleed
Robin D
RD
D000762:Anesthesia Recovery Period; D000777:Anesthetics / Q000494:pharmacology; D000818:Animals; D004576:Electromyography / Q000662:veterinary*; D005260:Female; D006736:Horses; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects; D019148:Neuromuscular Blockade / Q000662:veterinary*; D009466:Neuromuscular Blocking Agents / Q000494:pharmacology*; D015588:Observer Variation
D000777:Anesthetics; D009466:Neuromuscular Blocking Agents