Comparison between acceleromyography and visual assessment of train-of-four for monitoring neuromuscular blockade in horses undergoing surgery

ObjectiveTo compare acceleromyography (AMG) with visual assessment of train-of-four (TOF) for monitoring neuromuscular blockade and detecting residual muscle paralysis in horses receiving atracurium.Study designProspective, controlled clinical study.AnimalsNine adult, client-owned horses weighing 577 (436, 727) kg (median, minimum, maximum) and ASA physical status I–II, admitted for surgery.MethodsAn 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 ≥90% by AMG.ResultsDuring 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 ≥90% (p = 0.004).Conclusion and clinical relevance 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.     

Can we see fade? A survey of anesthesia providers and our ability to detect partial neuromuscular block in dogs

Objective

To assess the ability to visually detect fade during train-of-four (TOF) or double burst stimulation (DBS) in anesthetized dogs recovering from nondepolarizing neuromuscular block.

Twitch potentiation: a potential source of error during neuromuscular monitoring with acceleromyography in anesthetized dogs

ObjectiveTo measure twitch potentiation (the staircase phenomenon) in anesthetized dogs, and assess its relevance during neuromuscular monitoring with acceleromyography (AMG).Study designRandomized, prospective clinical trial.AnimalsSixteen dogs undergoing ovariohysterectomy.MethodsUnder isoflurane anesthesia, neuromuscular function was monitored with train-of-four (TOF) stimuli every 15 seconds and quantified by AMG. Neuromuscular blockade (NMB) was produced with 0.15 mg kg^?1 atracurium IV. Dogs were randomly divided into two groups; a potentiation group (PG) in which TOF stimulation was applied for 20 minutes before atracurium was administered; and a control group (CG) where no such time was allowed. In both groups, the AMG was calibrated (at tCAL) just before atracurium was administered. TOF stimulation continued throughout the experiment in all dogs. The height of the first twitch (T₁) (expressed as a fraction of T₁ at tCAL) and train-of-four ratio (TOFR) were recorded until TOFR returned to ≥90%.ResultsIn PG, T₁ increased significantly (p = 0.0078) from a median of 102% (range, 95, 109) at baseline to 118% (100, 142) at 20 minutes. In PG, no difference was found between T₁ at tCAL (immediately before atracurium administration) and T₁ when neuromuscular transmission returned (p = 0.42). In the CG, T₁ increased significantly between tCAL and the time neuromuscular transmission returned (p = 0.027). TOFR did not increase during twitch potentiation (all p = 0.32).Conclusions and clinical relevanceT₁ increased significantly during 20 minutes of uninterrupted TOF stimulation in the absence of NMB, establishing that twitch potentiation occurs in anesthetized dogs. With no time for potentiation, T₁ increased during the course of recovery from NMB; this phenomenon introduces a bias in T₁ measurements and could affect studies reporting potency and duration of NMB based on T₁ or single twitches. TOFR was unaltered by potentiation emphasizing its clinical usefulness for excluding post-operative residual NMB.     

Speed of reversal of vecuronium neuromuscular block with different doses of neostigmine in anesthetized dogs

Objectives

Neostigmine is routinely used to reverse non-depolarizing neuromuscular block. Given its indirect mechanism, a plateau may exist whereby increasing doses of neostigmine do not result in clinical benefit. This study was designed to measure the speed of reversal of vecuronium-induced neuromuscular block in isoflurane-anesthetized dogs after the administration of three doses of neostigmine as used in clinical practice.