Postoperative residual neuromuscular block: a survey of management

Neuromuscular blocking agents and monitoring in the equine patient

This article briefly reviews the physiology of the neuromuscular junction and the pharmacologic mechanisms of neuromuscular blocking agents. The clinical use of modern agents is discussed. Monitoring techniques used to assess the level of neuromuscular block and to exclude residual paralysis at the end of an anesthetic procedure are reviewed.

[Clinical evaluation of post-surgical bleeding after a sugammadex injection]

OBJECTIVE

Sugammadex reverses neuromuscular blockade by chemical encapsulation of nondepolarizing neuromuscular blocking drugs (rocuronium and vecuronium). The imprint of this new molecule has recently been supplemented with a section on haemostasis notifying a longer clotting time without documented clinical consequences. This has resulted in recommendations on the use of sugammadex in the presence of coagulation disorders (pharmacologically-induced or not). The objective of this study was to analyze the experience gathered with this molecule on clinically-evaluated bleeding. No study on this subject is currently available.

METHODS

This is a retrospective study over 1 year between August 2009 and August 2010. All patients with laparotomies for cancer surgery requiring suction drains were included. Patients were allocated to groups according to the type of reversal (without sugammadex versus sugammadex 2 or 4 mg/kg). The endpoint was clinically-evaluated postoperative bleeding (reoperation for haemostasis, blood-stained laparotomy dressings in the post-anaesthesia care unit [PACU], cumulative volume collected in suction drains upon arrival in PACU and then after 2 hours and the next morning at 6a.m).

RESULTS

One hundred and ninety-three patients were included in three groups, 78 in the group "without sugammadex", 95 in "sugammadex 2mg/kg" and 20 in "sugammadex 4 mg/kg". There were no reoperations for haemostasis. The comparison among different groups for the endpoint of bleeding showed no significant difference.

CONCLUSION

In this retrospective study performed in patients at high risk of postoperative bleeding, sugammadex at doses of 2 and 4 mg/kg was not associated with increased bleeding. This study, the first in this field, suggests that future prospective investigations should target patients receiving 4 or 16 mg/kg of sugammadex and/or with documented preoperative abnormal coagulations tests.

Failure to reverse prolonged vecuronium-induced neuromuscular blockade with edrophonium in an anesthetized dog

A case of prolonged muscle relaxation after vecuronium in an anesthetized dog is presented. After using peripheral nerve stimulation to confirm partial recovery of neuromuscular transmission, administration of 0.5 mg/kg IV of intravenous edrophonium failed to complete the reversal process. Subsequent administration of neostigmine resulted in complete recovery from blockade. Without monitoring neuromuscular function with a peripheral nerve stimulator until reversal was complete, it was very likely this patient would have been extubated with incomplete neuromuscular transmission. Several factors affecting the duration of neuromuscular blockade and its reversal are addressed.

Short term non-invasive ventilation post-surgery improves arterial blood-gases in obese subjects compared to supplemental oxygen delivery - a randomized controlled trial

BACKGROUND

In the immediate postoperative period, obese patients are more likely to exhibit hypoxaemia due to atelectasis and impaired respiratory mechanics, changes which can be attenuated by non-invasive ventilation (NIV). The aim of the study was to evaluate the duration of any effects of early initiation of short term pressure support NIV vs. traditional oxygen delivery via venturi mask in obese patients during their stay in the PACU.

METHODS

After ethics committee approval and informed consent, we prospectively studied 60 obese patients (BMI 30-45) undergoing minor peripheral surgery. Half were randomly assigned to receive short term NIV during their PACU stay, while the others received routine treatment (supplemental oxygen via venturi mask). Premedication, general anaesthesia and respiratory settings were standardized. We measured arterial oxygen saturation by pulse oximetry and blood gas analysis on air breathing. Inspiratory and expiratory lung function was measured preoperatively (baseline) and at 10 min, 1 h, 2 h, 6 h and 24 h after extubation, with the patient supine, in a 30 degrees head-up position. The two groups were compared using repeated-measure analysis of variance (ANOVA) and t-test analysis. Statistical significance was considered to be P < 0.05.

RESULTS

There were no differences at the first assessment. During the PACU stay, pulmonary function in the NIV group was significantly better than in the controls (p < 0.0001). Blood gases and the alveolar to arterial oxygen partial pressure difference were also better (p < 0.03), but with the addition that overall improvements are of questionable clinical relevance. These effects persisted for at least 24 hours after surgery (p < 0.05).

CONCLUSION

Early initiation of short term NIV during in the PACU promotes more rapid recovery of postoperative lung function and oxygenation in the obese. The effect lasted 24 hours after discontinuation of NIV. Patient selection is necessary in order to establish clinically relevant improvements. TRIAL REGISTRATION#: DRKS00000751; http://www.germanctr.de.

Postoperative residual curarization from intermediate-acting neuromuscular blocking agents delays recovery room discharge

BACKGROUND

Postoperative residual curarization (PORC) [train-of-four ratio (T4/T1) <0.9] is associated with increased morbidity and may delay postoperative recovery room (PACU) discharge. We tested the hypothesis that postoperative T4/T1 <0.9 increases PACU length of stay.

METHODS

At admission to the PACU, neuromuscular transmission was assessed by acceleromyography (stimulation current: 30 mA) in 246 consecutive patients. The potential consequences of PORC-induced increases in PACU length of stay on PACU throughput were estimated by application of a validated queuing model taking into account the rate of PACU admissions and mean length of stay in the joint system of the PACU plus patients recovering in operation theatre waiting for PACU beds.

RESULTS

PACU length of stay was significantly longer in patients with T4/T1 <0.9 (323 min), compared with patients with adequate recovery of neuromuscular transmission (243 min). Age (P=0.021) and diagnosis of T4/T1 <0.9 (P=0.027), but not the type of neuromuscular blocking agent, were independently associated with PACU length of stay. The incidence of T4/T1 <0.9 was higher in patients receiving vecuronium. Delayed discharge significantly increases the chances of patients having to wait to enter the PACU. The presence of PORC is estimated to be associated with significant delays in recovery room admission.

CONCLUSIONS

PORC is associated with a delayed PACU discharge. The magnitude of the effect is clinically significant. In our system, PORC increases the chances of patients having to wait to enter the PACU.

Residual neuromuscular block: lessons unlearned. Part I: definitions, incidence, and adverse physiologic effects of residual neuromuscular block

In this review, we summarize the clinical implications of residual neuromuscular block. Data suggest that residual neuromuscular block is a common complication in the postanesthesia care unit, with approximately 40% of patients exhibiting a train-of-four ratio <0.9. Volunteer studies have demonstrated that small degrees of residual paralysis (train-of-four ratios 0.7-0.9) are associated with impaired pharyngeal function and increased risk of aspiration, weakness of upper airway muscles and airway obstruction, attenuation of the hypoxic ventilatory response (approximately 30%), and unpleasant symptoms of muscle weakness. Clinical studies have also identified adverse postoperative events associated with intraoperative neuromuscular management. Large databased investigations have identified intraoperative use of muscle relaxants and residual neuromuscular block as important risk factors in anesthetic-related morbidity and mortality. Furthermore, observational and randomized clinical trials have demonstrated that incomplete neuromuscular recovery during the early postoperative period may result in acute respiratory events (hypoxemia and airway obstruction), unpleasant symptoms of muscle weakness, longer postanesthesia care unit stays, delays in tracheal extubation, and an increased risk of postoperative pulmonary complications. These recent data suggest that residual neuromuscular block is an important patient safety issue and that neuromuscular management affects postoperative outcomes.

Control of perioperative muscle strength during ambulatory surgery

PURPOSE OF REVIEW

This review describes strategies to control perioperative muscle strength in patients undergoing ambulatory surgery.

RECENT FINDINGS

Although it is impossible to improve muscle relaxation (defined as absence of electrical activity) of intact resting muscle by hypnotics, analgesia is required to prevent pain-evoked muscular contractions during surgery. Regional anesthesia, as well as hypnotics and opioids, promotes intraoperative muscle relaxation. Neuromuscular blocking agents (NMBAs) induce dose-dependent muscle relaxation, but their effects vary widely between individuals, and postoperative residual curarization (PORC) exposes patients to additional risk. Low doses of NMBAs should, therefore, be used, effects be monitored quantitatively by acceleromyography, and residual neuromuscular block be reversed. Acetylcholinesterase inhibitor reversal can cause respiratory side effects, so the lowest efficacious dose should be used: as little as 0.015-0.025 mg kg(-1) of neostigmine is required at a train-of-four count of four with minimal fade. Sugammadex encapsulates steroidal NMBAs. Sugammadex reversal is a viable approach to rapidly antagonize deep levels of neuromuscular block.

SUMMARY

Optimal muscle relaxation for ambulatory surgery results from a judicious combination of regional anesthesia, opioids, and low doses of NMBAs. The effects of NMBAs should be monitored quantitatively by acceleromyography and reversed appropriately.

Sugammadex, a selective reversal medication for preventing postoperative residual neuromuscular blockade

BACKGROUND

Sugammadex is the first selective relaxant binding agent that has been studied for reversal of neuromuscular blockade induced by rocuronium and other steroidal non-depolarizing neuromuscular blocking agents (NMBAs).

OBJECTIVES

To assess the efficacy and safety of sugammadex in reversing neuromuscular blockade induced by steroidal non-depolarizing NMBAs and in preventing postoperative residual neuromuscular blockade.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, Issue 3), MEDLINE (1950 to August 2008), and EMBASE (1980 to August 2008). In addition, we handsearched reference lists of relevant articles and meeting abstracts. Furthermore, we contacted the medication's manufacturer for more information.

SELECTION CRITERIA

All randomized controlled trials (RCTs) on adult patients (>/= 18 years old) in which sugammadex was compared with placebo or other medications, or in which different doses of sugammadex were compared with each other. We excluded non-randomized trials and studies on healthy volunteers.

DATA COLLECTION AND ANALYSIS

We independently performed determination of trial inclusion, quality assessment, and data extraction. We applied standard meta-analytic techniques.

MAIN RESULTS

We included18 RCTs (n = 1321 patients). Seven trials were published as full-text papers, and 11 trials only as meeting abstracts. All the included trials had adequate methods of randomization and allocation concealment. The results suggest that, compared with placebo or neostigmine, sugammadex can more rapidly reverse rocuronium-induced neuromuscular blockade regardless of the depth of the block. We identified 2, 4, and 16 mg/kg of sugammadex for reversal of rocuronium-induced neuromuscular blockade at T(2) reappearance , 1 to 2 post-tetanic counts, and 3 to 5 minutes after rocuronium, respectively. The number of trials are very limited regarding vecuronium and pancuronium. Serious adverse events occurred in < 1% of all patients who received the medication. There was no significant difference between sugammadex and placebo in terms of the prevalence of drug-related adverse events (RR 1.20, 95% CI 0.61 to 2.37; P = 0.59, I(2) = 0%, 5 RCTs). Also, no significant difference was found between sugammadex and neostigmine for adverse events (RR 0.98, 95% CI 0.48 to1.98; P = 0.95, I(2) = 43%, 3 RCTs).

AUTHORS' CONCLUSIONS

Sugammadex was shown to be effective in reversing rocuronium-induced neuromuscular blockade. This review has found no evidence of a difference in the instance of unwanted effects between sugammadex, placebo or neostigmine. These results need to be confirmed by future trials on larger patient populations and with more focus on patient-related outcomes.

Monitoring neuromuscular block: an update

The first part of this article presents an update of the basic considerations of neuromuscular monitoring. It emphasises the need to assure supramaximal stimulation, to place the stimulating electrodes correctly and to use appropriate sites for nerve stimulation as well as appropriate stimulation patterns. The second part focuses on current developments and ongoing discussion. The authors describe the performance of acceleromyography and the need for initial calibration when using these quantitative devices.

The undesirable effects of neuromuscular blocking drugs

Neuromuscular blocking drugs are designed to bind to the nicotinic receptor at the neuromuscular junction. However, they also interact with other acetylcholine receptors in the body. Binding to these receptors causes adverse effects that vary with the specificity for the cholinergic receptor in question. Moreover, all neuromuscular blocking drugs may cause hypersensitivity reactions. Often the symptoms are mild and self-limiting but massive histamine release can cause systematic reactions with circulatory and respiratory symptoms and signs. At the end of anaesthesia, no residual effect of a neuromuscular blocking drug should be present. However, the huge variability in response to neuromuscular blocking drugs makes it impossible to predict which patient will suffer postoperative residual curarization. This article discusses the undesirable effects of the currently available neuromuscular blocking drugs including the definitions, diagnosis and causes of hypersensitivity reactions and postoperative residual curarisation.

Clinical limitations of acetylcholinesterase antagonists

Administration of a nondepolarizing neuromuscular blocking drug (muscle relaxant) is a standard practice in many anesthetic scenarios. These muscle relaxants work by competitive antagonism of the neurotransmitter acetylcholine at nicotinic cholinergic receptors within the neuromuscular junction of skeletal muscle (Martyn et al; Neuromuscular physiology and pharmacology, anesthesia. Edited by RD Miller, Philadelphia, Churchill Livingstone, 2000). At the conclusion of the procedure for which the muscle relaxant was administrated, there will be a greater or lesser degree of residual muscle weakness. It is usually necessary to pharmacologically reverse this residual weakness to restore full function to the patient's muscles. Indeed, failure to reverse neuromuscular block is associated with increased perioperative morbidity and mortality (Arbous et al; Impact of anesthesia management characteristics on severe morbidity and mortality. Anesthesiology 2005;102:257-268; quiz 491-2). Pharmacologic reversal currently relies on the administration of an anticholinesterase drug, which decreases the metabolism of acetylcholine at the neuromuscular junction and allows its concentration to increase and hopefully overcome the effect of the muscle relaxant. This approach to reversal has significant limitations; the mechanism of reversal is indirect, the efficacy is limited and unpredictable, and undesirable autonomic responses occur. This review will address these limitations.

Residual neuromuscular blockade and critical respiratory events in the postanesthesia care unit

BACKGROUND

Incomplete recovery of neuromuscular function may impair pulmonary and upper airway function and contribute to adverse respiratory events in the postanesthesia care unit (PACU). The aim of this investigation was to assess and quantify the severity of neuromuscular blockade in patients with signs or symptoms of critical respiratory events (CREs) in the PACU.

METHODS

We collected data over a 1-yr period. PACU nurses identified patients with evidence of a predefined CRE during the first 15 min of PACU admission. Train-of-four (TOF) ratios were immediately quantified in these patients using acceleromyography (cases). TOF data were also collected in a control group that consisted of patients undergoing a general anesthetic during the same period who were matched with the cases by age, sex, and surgical procedure.

RESULTS

A total of 7459 patients received a general anesthetic during the 1-yr period, of whom 61 developed a CRE. Forty-two of these cases were matched with controls and constituted the study group for statistical analysis. The most common CREs among matched cases were severe hypoxemia (22 of 42 patients; 52.4%) and upper airway obstruction (15 of 42 patients; 35.7%). There were no significant differences between the cases and matched controls in any measured preoperative or intraoperative variables. Mean (+/-sd) TOF ratios were 0.62 (+/-0.20) in the cases, with 73.8% of the cases having TOF ratios <0.70. In contrast, TOF values in the controls were 0.98 (+/-0.07) (a difference of -0.36 with a 95% confidence interval of -0.43 to -0.30, P < 0.0001), and no control patients were observed to have TOF values <0.70 (the 95% confidence interval of the difference was 59%-85%, P < 0.0001).

CONCLUSIONS

A high incidence of severe residual blockade was observed in patients with CREs, which was absent in control patients without CREs. These findings suggest that incomplete neuromuscular recovery is an important contributing factor in the development of adverse respiratory events in the PACU.

Prolonged residual paralysis after a single intubating dose of rocuronium

It is often argued that neuromuscular monitoring is unnecessary when only one dose of an intermediate-acting neuromuscular blocking agent is given. This case report documents that it may take more than 3.5 h before it is possible to antagonize a block caused by a normal dose of rocuronium (0.6 mg kg(-1)). Possible causes of the extremely prolonged duration of action are discussed, as is the importance of quantitative neuromuscular monitoring.

Neuromuscular monitoring and postoperative residual curarisation: a meta-analysis

We conducted a meta-analysis to examine the effect of intraoperative monitoring of neuromuscular function on the incidence of postoperative residual curarisation (PORC). PORC has been considered present when a patient has a train-of-four (TOF) ratio of < 0.7 or < 0.9. We analysed data from 24 trials (3375 patients) that were published between 1979 and 2005. We excluded data on mivacurium from this meta-analysis because only three studies had examined the incidence of PORC associated with its use. Long- and intermediate-acting neuromuscular blocking drugs had been given to 662 and 2713 patients, respectively. Neuromuscular function was monitored in 823 patients (24.4%). A simple peripheral nerve stimulator was used in 543 patients, and an objective monitor was used in 280. The incidence of PORC was found to be significantly lower after the use of intermediate neuromuscular blocking drugs. We could not demonstrate that the use of an intraoperative neuromuscular function monitor decreased the incidence of PORC.

Incidence and duration of residual paralysis at the end of surgery after multiple administrations of cisatracurium and rocuronium

In a randomised, controlled, double-blind, multicentre trial in 338 patients, we assessed the incidence of residual paralysis following administration of cisatracurium or rocuronium. The incidence at the end of surgery was significantly lower in patients treated with rocuronium (62 of 142 patients, 44%) than in those given cisatracurium (99 of 175 patients, 57%) (p < 0.05). In contrast, with rocuronium the mean (SD) time between skin closure and extubation was 28 (28) min vs 18 (19) min for cisatracurium, and the duration 0.9 (time from administration of last top-up dose to recovery of the train-of-four ratio to 0.9) was significantly longer and more variable for rocuronium than for cisatracurium. Thus, after repeated administration, the duration and variability of duration of action are greater with rocuronium compared with cisatracurium. These pharmacodynamic differences do not necessarily translate into a higher incidence of residual paralysis, because clinicians compensate for the longer duration of action and variability of rocuronium by terminating administration of the neuromuscular blocking earlier.