Residual neuromuscular blockade

Despite the availability of modern neuromuscular blocking agents with short or intermediate duration of action, incidence of residual neuromuscular blockade remains very high. Evidences have been recently provided that residual curarization must be defined as a train-of-four ratio below 0.9 at the thumb adductor during the recovery period after anaesthesia. Residual curarization may be associated with serious adverse events related to respiratory depression, pharyngeal dysfunction, hypoxemia and prolongation of the length of stay in the recovery room. Appropriate choice of drugs, perioperative monitoring of neuromuscular function and large indications of pharmacological reversal may reduce the incidence of residual curarization and improve the patient's safety in the postoperative setting.     

Residual paralysis induced by either vecuronium or rocuronium after reversal with pyridostigmine

We investigated postoperative residual curarization after administration of either vecuronium or rocuronium with reversal by pyridostigmine in 602 consecutive patients without perioperative neuromuscular monitoring. On arrival in the recovery room, neuromuscular function was assessed both by acceleromyography in a train-of-four (TOF) pattern and also clinically by the ability to sustain a head-lift for >5 s and the tongue-depressor test. Postoperative residual curarization was defined as a TOF ratio <0.7. One fifth of 602 patients (vecuronium, 24.7%; rocuronium, 14.7%) had a TOF <0.7 in the recovery room. There were no significant differences in the TOF ratios between 10 mg and 20 mg of pyridostigmine. The patients with residual block had several associated factors: the absence of perioperative neuromuscular monitoring, the use of pyridostigmine, which is less potent than neostigmine, a larger dose of vecuronium, shorter time from the last neuromuscular blocker to TOF monitoring, or peripheral cooling. We conclude that significant residual neuromuscular block after vecuronium or rocuronium was not eliminated even with reversal by a large dose of pyridostigmine. IMPLICATIONS: Without monitoring, the significant residual neuromuscular block after vecuronium or rocuronium is not eliminated even by reversal with a large dose of pyridostigmine and can still be a problem in the recovery room.     

Neuromuscular monitoring and postoperative residual curarization

Editor—In their meta-analysis of neuromuscular monitoringand postoperative residual curarization (PORC), Naguib and colleagues¹conclude that they ‘... could not demonstrate that theuse of an intraoperative neuromuscular function monitor decreasedthe incidence of PORC’. We agree that given their hypothesis(that intraoperative neuromuscular monitoring, including bothobjective and non-objective methods, would reduce the incidenceof PORC) and the chosen methodology (a meta-analysis based onboth comparative and non-comparative studies), this conclusionon their work is correct. However, we do question the relevanceof both the hypothesis and the use of a meta-analysis—andaccordingly also their conclusion. In fact, the authors themselvesalso doubt the conclusion reached, based on     

Assessment of residual curarization using low-current stimulation

The present study employed train-of-four (TOF) stimulation at a current of 20 mA to assess the incidence and degree of residual neuromuscular blockade in 64 randomly selected Post Anesthesia Care Unit (PACU) patients. Group C (Control, n = 10) had received anaesthesia without nondepolarizing muscle relaxant; Group V (n = 25) had received vecuronium; and Group P (n = 29) had received pancuronium. At the end of surgery, each patient had been considered by his anaesthetist to have adequate neuromuscular function on the basis of clinical signs and tactile or visual evaluation of responses to TOF stimulation. However, upon testing in the PACU 15 min later, 45% (13 of 29) of Group P patients and 8% (2 of 25) of Group V patients had a TOF ration less than 0.70. This study indicates that residual curarization may be commonly encountered following long-acting relaxants despite qualitative intraoperative TOF monitoring. The present incidence, detected at a current of 20 mA, is consistent with previous reports which employed supramaximal TOF stimulation. We conclude that despite intraoperative monitoring, residual curarization following long-acting nondepolarizing agents is common and that it may be detected with TOF at a low stimulating current (20 mA).     

Neuromuscular monitoring: does it make a difference?

Purpose

The objective of the present prospective study was to evaluate the influence of neuromuscular monitoring. on the level of neuromuscular blockade from induction of anaesthesia until extubdtion of the trachea.

Methods

Forty-two patients aged between 18 and 73 yr undergoing a range of surgical procedures under general anaesthesia were randomly distributed into two groups of 21 patients each. In both groups a Datex NMT Monitor® was used and electromyographic responses of the the ulnar muscles to supramaximal stimulation of the ulnar nerve were recorded. In Group 1, the anaesthetist could see the movements of the stimulated hand, but not the monitor. In Group 2, the anaesthetist could see neither the stimulated hand nor the monitor. The same anaesthetist administered the neuromuscular relaxants which were succinylcholine 1.5 mg · kg^?1 for trachéal intubation and vecuronium 0.1 mg· kg^?1 for neuromuscular relaxation during surgery, followed by 1 to 2 mg maintenance injections. Possible residual curarization was evaluated in the recovery room by head lift tests and pulse oximetry.

Results

Patients in Group 1 had deeper neuromuscular block throughout surgery, despite the use of a comparable dose of vecuronium (10.1 mg for G1 vs 11.2 mg for G2). The EMG values of T₁ and train-of-four values were not different at trachéal intubation or at extubation. No patients presented signs of residual curarization in the recovery room.

Conclusion

The study demonstrates that with the same amount of vecuronium the neuromuscular relaxation was deeper with the use of a simple neuromuscular monitoring (visual evaluation of the thumb movements). Despite the deeper neuromuscular block in the monitored group, there was no residual curarization in the recovery room.     

Bloc résiduel prolongé après injection unique de rocuronium pour l’intubation : une étiologie originale

Postoperative curarization following a single dose of rocuronium is a known risk quickly diagnosed through the monitoring of neuromuscular blockade. Different etiologies can cause a prolonged block. We report the case of a misdiagnosis of prolonged neuromuscular blockade by a failure in the monitoring system of curarization.     

Monitoring of neuromuscular block

The first 150 words of the full text of this article appear below. Key points Postoperative residual curarization occurs evenafter administration of intermediate-acting non-depolarizingneuromuscular blocking drugs, for example, atracurium or vecuronium. Satisfactoryrecovery from neuromuscular block has not occured until thetrain-of-four ratio is >0.9. Quantitative methods of measuringevoked responses, for the example, acceleromyography or mechanomyography,are necessary to ensure adequate recovery from block. Onsetand recovery from neuromuscular block occurs at different ratesin different muscles. Anticholinesterases should not be usedto antagonize residual neuromuscular block unless full recoveryhas been demonstrated.   There is increasing evidence that residual neuromuscular blockis common, and also that it may adversely affect patient outcome.A study by Debaene and colleagues¹ found that 45% of patientshad residual curarization (train-of-four [TOF] ratio<0.9)in the postoperative recovery room after a single intubatingdose of the intermediate-acting drugs atracurium, vecuroniumor rocuronium. Another study found residual curarization (TOFratio<0.7) in 42% of patients in the . . . [Full Text of this Article]