Effectiveness of sugammadex versus neostigmine on restoration of neuromuscular function in surgical patients with myasthenia gravis undergoing rocuronium-induced neuromuscular blockade: a systematic review protocol

REVIEW QUESTION/OBJECTIVE

The objective of this systematic review is to identify the effectiveness of sugammadex versus neostigmine on the reversal of rocuronium-induced neuromuscular blockade in surgical patients with myasthenia gravis undergoing general anesthesia.

Efficacy and safety of sugammadex versus neostigmine in reversing neuromuscular blockade in adults

BACKGROUND

Acetylcholinesterase inhibitors, such as neostigmine, have traditionally been used for reversal of non-depolarizing neuromuscular blocking agents. However, these drugs have significant limitations, such as indirect mechanisms of reversal, limited and unpredictable efficacy, and undesirable autonomic responses. Sugammadex is a selective relaxant-binding agent specifically developed for rapid reversal of non-depolarizing neuromuscular blockade induced by rocuronium. Its potential clinical benefits include fast and predictable reversal of any degree of block, increased patient safety, reduced incidence of residual block on recovery, and more efficient use of healthcare resources.

OBJECTIVES

The main objective of this review was to compare the efficacy and safety of sugammadex versus neostigmine in reversing neuromuscular blockade caused by non-depolarizing neuromuscular agents in adults.

SEARCH METHODS

We searched the following databases on 2 May 2016: Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE (WebSPIRS Ovid SP), Embase (WebSPIRS Ovid SP), and the clinical trials registries www.controlled-trials.com, clinicaltrials.gov, and www.centerwatch.com. We re-ran the search on 10 May 2017.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) irrespective of publication status, date of publication, blinding status, outcomes published, or language. We included adults, classified as American Society of Anesthesiologists (ASA) I to IV, who received non-depolarizing neuromuscular blocking agents for an elective in-patient or day-case surgical procedure. We included all trials comparing sugammadex versus neostigmine that reported recovery times or adverse events. We included any dose of sugammadex and neostigmine and any time point of study drug administration.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened titles and abstracts to identify trials for eligibility, examined articles for eligibility, abstracted data, assessed the articles, and excluded obviously irrelevant reports. We resolved disagreements by discussion between review authors and further disagreements through consultation with the last review author. We assessed risk of bias in 10 methodological domains using the Cochrane risk of bias tool and examined risk of random error through trial sequential analysis. We used the principles of the GRADE approach to prepare an overall assessment of the quality of evidence. For our primary outcomes (recovery times to train-of-four ratio (TOFR) > 0.9), we presented data as mean differences (MDs) with 95 % confidence intervals (CIs), and for our secondary outcomes (risk of adverse events and risk of serious adverse events), we calculated risk ratios (RRs) with CIs.

MAIN RESULTS

We included 41 studies (4206 participants) in this updated review, 38 of which were new studies. Twelve trials were eligible for meta-analysis of primary outcomes (n = 949), 28 trials were eligible for meta-analysis of secondary outcomes (n = 2298), and 10 trials (n = 1647) were ineligible for meta-analysis.We compared sugammadex 2 mg/kg and neostigmine 0.05 mg/kg for reversal of rocuronium-induced moderate neuromuscular blockade (NMB). Sugammadex 2 mg/kg was 10.22 minutes (6.6 times) faster then neostigmine 0.05 mg/kg (1.96 vs 12.87 minutes) in reversing NMB from the second twitch (T2) to TOFR > 0.9 (MD 10.22 minutes, 95% CI 8.48 to 11.96; I2 = 84%; 10 studies, n = 835; GRADE: moderate quality).We compared sugammadex 4 mg/kg and neostigmine 0.07 mg/kg for reversal of rocuronium-induced deep NMB. Sugammadex 4 mg/kg was 45.78 minutes (16.8 times) faster then neostigmine 0.07 mg/kg (2.9 vs 48.8 minutes) in reversing NMB from post-tetanic count (PTC) 1 to 5 to TOFR > 0.9 (MD 45.78 minutes, 95% CI 39.41 to 52.15; I2 = 0%; two studies, n = 114; GRADE: low quality).For our secondary outcomes, we compared sugammadex, any dose, and neostigmine, any dose, looking at risk of adverse and serious adverse events. We found significantly fewer composite adverse events in the sugammadex group compared with the neostigmine group (RR 0.60, 95% CI 0.49 to 0.74; I2 = 40%; 28 studies, n = 2298; GRADE: moderate quality). Risk of adverse events was 28% in the neostigmine group and 16% in the sugammadex group, resulting in a number needed to treat for an additional beneficial outcome (NNTB) of 8. When looking at specific adverse events, we noted significantly less risk of bradycardia (RR 0.16, 95% CI 0.07 to 0.34; I2= 0%; 11 studies, n = 1218; NNTB 14; GRADE: moderate quality), postoperative nausea and vomiting (PONV) (RR 0.52, 95% CI 0.28 to 0.97; I2 = 0%; six studies, n = 389; NNTB 16; GRADE: low quality) and overall signs of postoperative residual paralysis (RR 0.40, 95% CI 0.28 to 0.57; I2 = 0%; 15 studies, n = 1474; NNTB 13; GRADE: moderate quality) in the sugammadex group when compared with the neostigmine group. Finally, we found no significant differences between sugammadex and neostigmine regarding risk of serious adverse events (RR 0.54, 95% CI 0.13 to 2.25; I2= 0%; 10 studies, n = 959; GRADE: low quality).Application of trial sequential analysis (TSA) indicates superiority of sugammadex for outcomes such as recovery time from T2 to TOFR > 0.9, adverse events, and overall signs of postoperative residual paralysis.

AUTHORS' CONCLUSIONS

Review results suggest that in comparison with neostigmine, sugammadex can more rapidly reverse rocuronium-induced neuromuscular block regardless of the depth of the block. Sugammadex 2 mg/kg is 10.22 minutes (˜ 6.6 times) faster in reversing moderate neuromuscular blockade (T2) than neostigmine 0.05 mg/kg (GRADE: moderate quality), and sugammadex 4 mg/kg is 45.78 minutes (˜ 16.8 times) faster in reversing deep neuromuscular blockade (PTC 1 to 5) than neostigmine 0.07 mg/kg (GRADE: low quality). With an NNTB of 8 to avoid an adverse event, sugammadex appears to have a better safety profile than neostigmine. Patients receiving sugammadex had 40% fewer adverse events compared with those given neostigmine. Specifically, risks of bradycardia (RR 0.16, NNTB 14; GRADE: moderate quality), PONV (RR 0.52, NNTB 16; GRADE: low quality), and overall signs of postoperative residual paralysis (RR 0.40, NNTB 13; GRADE: moderate quality) were reduced. Both sugammadex and neostigmine were associated with serious adverse events in less than 1% of patients, and data showed no differences in risk of serious adverse events between groups (RR 0.54; GRADE: low quality).

Worldwide experience with sugammadex sodium: implications for the United States

Sugammadex sodium is a modified γ-cyclodextrin with a very high affinity for rocuronium and, to a lesser extent, vecuronium molecules. In vivo administration results in immediate encapsulation of rocuronium and vecuronium, resulting in termination of neuro- muscular blockade, usually within 3 minutes. This new neuromuscular blocking agent is specific for the aminosteroidal neuromuscular blocking agents rocuronium and vecuronium. Experience gained through worldwide clinical use of sugammadex offers US anesthesia providers the opportunity to better understand this new drug and its clinical applications. The seminal and current literature concerning clinical use of sugammadex is reviewed, and considerations for its incorporation into practice are provided.

[Efficacy and safety of sugammadex (Org 25969) in reversing moderate neuromuscular block induced by rocuronium or vecuronium in Japanese patients]

BACKGROUND

Efficacy and safety of sugammadex in reversing neuromuscular block induced by rocuronium or vecuronium were investgated in Japanese patients.

METHODS

We studied 98 Japanese patients undergoing surgery requiring general anesthesia. Patients were allocated randomly to receive intubation dose of rocuronium or vecuronium. During surgery, patients received additional doses of rocuronium or vecuronium for maintenance of moderate block. At T2 reappearance sugammadex 0-4.0 mg . kg-1 was administered. The neuromuscular block was monitored with acceleromyography using TOF stimuli. Sevoflurane was administered to all treatment groups after intubation.

RESULTS

For the rocuronium-induced neuromuscular block, the mean recovery time of the T4/T1 ratio to 0.9 decreased from 82.1 min in the placebo group to 1.8 min in the 4.0 mg . kg-1 sugammadex group. For the vecuronium-induced neuromuscular block, it decreased from 83.2 min in the placebo group to 2.1 min in the sugammadex 4.0 mg . kg-1 group. Plasma concentrations of sugammadex were approximately dose proportional over the dose range of 0.5 to 4.0 mg . kg-1 and independent of the neuromuscular blocking agents used. No clinical evidence of recurarization or residual curarization was observed.

CONCLUSIONS

The efficacy and safety of sugammadex were confirmed in Japanese surgical patients.

[Efficacy and safety of sugammadex (Org 25969) in reversing deep neuromuscular block induced by rocuronium or vecuronium in Japanese patients]

BACKGROUND

Efficacy and safety of sugammadex in reversing neuromuscular block induced by rocuronium or vecuronium were investgated in Japanese patients.

METHODS

We studied 99 Japanese patients undergoing surgery requiring general anesthesia. Patients were allocated randomly to receive intubation dose of rocuronium or vecuronium. During surgery, patients received additional dose of rocuronium or vecuronium for maintenance of deep block. At 1-2 PTC, 0.5-8.0 mg . kg-1 of sugammadex was administered. The neuromuscular block was monitored with acceleromyography using TOF stimuli. Sevoflurane was administered to all treatment groups after intubation.

RESULTS

For the rocuronium-induced neuromuscular block, the mean recovery time of the T4/T1 ratio to 0.9 decreased from 66.9 min in the sugammadex 0.5 mg kg-1 group to 1.3 min in the sugammadex 8.0 mg kg-1 group. For the vecuronium-induced neuromuscular block it decreased from 79.5 min in the sugammadex 0.5 mg . kg-1 group to 2.9 min in the sugammadex 8.0 mg . kg-1 group. No clinical evidence of recurarization or residual curarization was observed.

CONCLUSIONS

The efficacy and safety of sugammadex were confirmed in Japanese surgical patients for reversal from deep block.

The concept behind sugammadex

Sugammadex is the first selective relaxant binding agent. It allows rapid reversal of any degree of neuromuscular blockade induced by steroidal neuromuscular blocking agents. Sugammadex acts by encapsulation of the neuromuscular blocking agent. This prevents the drug from acting on prejunctional and postjunctional nicotinic receptors, allowing acetylcholine to activate these receptors, and resulting in reversal of the neuromuscular blockade. Objective monitoring of the degree of neuromuscular blockade is strongly recommended to determine the optimal dose of sugammadex. A good understanding of the concept behind sugammadex is essential in order to use this reversal agent in clinical practice.

[Sugammadex--two years in clinical practice]

Sugammadex is a modified gamma cyclodextrin, specifically designed for the reversal of neuromuscular blockade (NMB) induced by the steroidal neuromuscular blocking agents, rocuronium and vecuronium. Sugammadex acts by encapsulating the unbound drug molecules and reducing their concentration at the neuromuscular junction, allowing rapid reversal of NMB at every stage. Unlike acetylcholinesterase inhibitors, sugammadex is also effective in the reversal of profound NMB and is well tolerated. The recommended doses are in the range of 2-16 mg kg(-1), depending on the intensity of the block. Perioperative neuromuscular transmission monitoring is mandatory in enabling the choice of the right doses of sugammadex. This review presents various aspects of the use of sugammadex in adult and paediatric patients, and provides guidelines for practical administration.

[Sugammadex, a novel drug for neuromuscular blockade reversal]

Significant progress in the management of aminosteroid nondepolarizing neuromuscular blockers will follow the introduction of sugammadex (Org 25969). Safety and rapid recovery of muscle force will improve and the adverse effects of acetylcholinesterase inhibitors will be avoided. Sugammadex is a modified gamma-cyclodextrin agent developed for the specific reversal of rocuronium and, to a lesser extent, vecuronium. This novel drug functions by means of encapsulation (chelation). Sugammadex was recently approved by the European Medicines Evaluation Agency and became available in Spain in 2009, leading to a series of changes related to patient safety and surgical conditions. We review the literature on sugammadex published to date.

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.

Preclinical pharmacology of sugammadex

Since the introduction of nondepolarizing neuromuscular blocking agents, acetylcholinesterase inhibitors have been used to increase the speed of recovery from neuromuscular blockade. The major disadvantages of acetylcholinesterase inhibitors are their lack of activity against profound neuromuscular blockade and their activity outside the neuromuscular junction resulting in unwanted side effects, requiring cotreatment with a muscarinic antagonist. An alternative to acetylcholinesterase inhibitors is the encapsulating agent sugammadex. This agent has been specifically designed to encapsulate the steroidal neuromuscular blocking agents rocuronium and vecuronium. This review describes the effects of sugammadex in in vitro tissue and in vivo animal experiments. The encapsulation approach allows reversal of any degree of neuromuscular blockade because the dose of sugammadex can be adjusted to encapsulate sufficient neuromuscular blocking molecules to cause effective reversal. Because this interaction is a drug-drug interaction, reversal can be achieved very fast but is limited by the circulation time. Sugammadex is also effective against neuromuscular blockade under conditions with reduced acetylcholine release, which potentiate the action of neuromuscular blocking agents. Sugammadex does not cause cholinergic side effects, preventing the need of coadministration of muscarinic antagonists. Because of these properties, sugammadex has the potential to become a very useful drug for the management of neuromuscular blockade.

An update on sugammadex sodium

Sugammadex sodium is the generic drug name for the novel modified gamma cyclodextrin that terminates neuromuscular blockade induced by aminosteroidal neuromuscular blocking agents. Published phase II and phase III clinical data support preclinical and clinical phase I study findings of fast, safe, and efficacious reversal of all levels of neuromuscular blockade induced by rocuronium and vecuronium. Low levels of neuromuscular blockade induced by pancuronium have also been successfully reversed by sugammadex. This agent does not reverse the bis-isoquinoline neuromuscular blocking agents. Special patient populations, including pediatric, elderly, cardiac, and renal-compromised subjects, have been studied in phase III. This update focuses on the most recent findings of phase II and III clinical studies.

[Reversal of neuromuscular blockade and complications of remaining blocking effect]

We Japanese anesthesiologists can now use rocuronium as well as vecuronium. Although the onset of rocuronium is more rapid, the non-depolarizing neuromuscular blocking (NMB) agent has similar characteristics of duration and recovery compared to vecuronium. Reversal of NMB is therefore essential to recover patients safely. Conventional standard of reversal of NMB [train of four (TOF) >0.7] is not enough to have sufficient vital capacity and inspiratory force, resulting in pulmonary regurgitation or atelectasis. Even though the reversal of NMB cannot sufficiently be completed by anti-cholinesterase (ChE) agents such as neostigmine, it is needed to reverse the NMB because of their late spontaneous recovery. We also have to take care of patients with neuromusclar diseases such as Duchenne-type muscle dystrophy, when we use anti-ChE agents. Sugammadex is a novel and unique compound designed as an antagonist of rocuronium and possibly other steroid NMB agents. Sugammadex exerts its effect by forming very tight water-soluble complexes at a 1 : 1 ratio with steroid NMB agents (rocuronium>vecuronium>>pancuronium). PhaseIII trials in Japan as well as Europe and the US have just been finished, and it is expected to be used clinically in the near future.

Effective reversal of moderate rocuronium- or vecuronium-induced neuromuscular block with sugammadex, a selective relaxant binding agent

BACKGROUND

Sugammadex rapidly reverses rocuronium-induced neuromuscular block. This study explored the dose-response relation of sugammadex given as a reversal agent at reappearance of the second muscle twitch after rocuronium- and vecuronium-induced block. A secondary objective was to investigate the safety of single doses of sugammadex.

METHODS

In this two-center, phase II, dose-finding study, 80 patients (age >or= 18 yr, American Society of Anesthesiologists physical status I or II, surgery >or= 60 min requiring muscle relaxation for intubation) were randomly assigned to receive rocuronium (0.60 mg/kg) or vecuronium (0.10 mg/kg). Sugammadex or placebo was administered at reappearance of the second muscle twitch. The primary efficacy endpoint was time from starting sugammadex administration until recovery of the train-of-four ratio to 0.9.

RESULTS

Compared with placebo, sugammadex produced dose-dependent decreases in mean time to recovery for all train-of-four ratios in the rocuronium and vecuronium groups. The mean time for recovery of the train-of-four ratio to 0.9 in the rocuronium group was 31.8 min after placebo compared with 3.7 and 1.1 min after 0.5 and 4.0 mg/kg sugammadex, respectively. The mean time for recovery of the train-of-four ratio to 0.9 in the vecuronium group was 48.8 min after placebo, compared with 2.5 and 1.4 min after 1.0 and 8.0 mg/kg sugammadex, respectively. Sugammadex was well tolerated.

CONCLUSION

Sugammadex rapidly reversed rocuronium- or vecuronium-induced neuromuscular block at reappearance of the second muscle twitch and was well tolerated. A dose-response relation was observed with sugammadex for reversal of both rocuronium- and vecuronium-induced neuromuscular block.

Emergency Use of Sugammadex After Failure of Standard Reversal Drugs

Administration of sugammadex, 350 mg IV (4 mg/kg), in the postanesthesia care unit immediately (<60 s) relieved acute respiratory distress due to residual neuromuscular blockade in a 42-yr-old patient with chronic renal failure who had received vecuronium, 10 mg IV, for tracheal intubation, after inadequate reversal of neuromuscular blockade in the operating room with neostigmine, 5 mg IV, and glycopyrrolate, 1 mg IV.

Neostigmine-induced reversal of vecuronium in normal weight, overweight and obese female patients

BACKGROUND

The purpose of this study was to compare neostigmine-induced reversal of vecuronium in normal weight, overweight and obese female patients.

METHODS

In total, 15 each of normal weight (18.5<or=BMI<25), overweight (25<or=BMI<30) and obese (BMI>or=30) patients were enrolled. Anaesthesia was induced and maintained with fentanyl, propofol and nitrous oxide. Neuromuscular block was induced with vecuronium 0.1 mg kg(-1) on the basis of the patient's real body weight (RBW) and was monitored using acceleromyographic train-of-four (TOF) of the adductor pollicis. All patients received neostigmine 0.04 mg kg(-1) combined with atropine 0.02 mg kg(-1) at 25% recovery of the first twitch (T1) of TOF and were allowed to recover to a TOF ratio of 0.9.

RESULTS

The time from administration of vecuronium to spontaneous recovery of T1 to 25% of control was significantly longer in the obese [mean (SD, range); 68.4 (16.3, 39.8-110.8) min] and the overweight groups [49.3 (6.2, 39.8-60.8) min] as compared with the normal weight group [41.0 (9.0, 27.5-59.5) min]. The times for facilitated recovery with neostigmine to a TOF ratio of 0.7 did not differ among groups. However, the recovery to a TOF ratio of 0.9 in the obese [25.9 (6.7, 13.5-41.0) min] and the overweight groups [14.6 (7.7, 3.3-28.5) min] were significantly longer than that in the normal weight group [6.9 (2.0, 3.0-10.7) min].

CONCLUSIONS

Early reversal after neostigmine is prompt; however, recovery to a TOF ratio of 0.9 is slow in overweight and obese patients when vecuronium is dosed on the basis of the patient's RBW.

Drugs to facilitate recovery of neuromuscular blockade and muscle strength

Several drugs that quicken recovery from neuromuscular blockade caused by vecuronium in anesthetized patients are reviewed. Ulinastatin, a protease inhibitor, is thought to promote the release of acetylcholine at the neuromuscular junction and increases hepatic blood flow and urine volume. For this reason, ulinastatin quickens recovery from neuromuscular blockade in anesthetized patients receiving vecuronium. Additionally, pretreatment with ulinastatin avoids prolongation of vecuronium-induced neuromuscular blockade in patients with hepatic cirrhosis. Gabexate mesilate is also a protease inhibitor. During a continuous infusion of gabexate mesilate, recovery from neuromuscular blockade was quickened. Amino acid-enriched solution supplies energy to the skeletal muscles and causes an increase in muscle strength. An infusion of amino acid-enriched solution hastens recovery from neuromuscular blockade in anesthetized patients. When amino acids supply energy to the skeletal muscles, they simultaneously produce heat in the skeletal muscles. This thermal generation may be closely related to fast recovery from neuromuscular blockade. Amino acid-enriched solution makes recovery from neuromuscular blockade quick and avoids hypothermia during general anesthesia. Milrinone, a phosphodiesterase III inhibitor, is supposed to increase the release of acetylcholine at the neuromuscular junction and make the neuromuscular junction sensitive to acetylcholine. Therefore, recovery from neuromuscular blockade is hastened. Nicorandil enhances membrane K+ conductance in skeletal muscle and increases contraction of the skeletal muscle. Thus, nicorandil quickens recovery from neuromuscular blockade.

Retracted : Reversal of vecuronium with neostigmine in patients with diabetes mellitus

Reversal of vecuronium-induced neuromuscular blockade with neostigmine was compared in two groups of 16 subjects: patients with Type 2 diabetes mellitus and normal controls. When the first twitch of the train-of-four had returned to 25% of the control value, neostigmine 40 microg x kg(-1) and atropine 20 microg x kg(-1) were given to reverse the neuromuscular blockade. The train-of-four ratio was lower at 3 min, 6 min, 9 min, 12 min and 15 min after reversal in the diabetic group than in the control group but the differences did not reach statistical significance. Fifteen minutes after reversal, the number of patients in whom recovery from neuromuscular blockade was judged insufficient to guarantee good respiratory function (train-of-four ratio < 0.74) did not differ between the groups. However, 15 min after reversal, the number of patients with a train-of-four ratio < 0.9 was significantly higher in the Diabetic Group than in the Control Group (15 vs. 10, p = 0.033).

Edrophonium effectively antagonizes neuromuscular block at the laryngeal adductors induced by rapacuronium, rocuronium and cisatracurium, but not mivacurium

PURPOSE

To examine the efficacy of antagonism of rapacuronium-, mivacurium-, rocuronium- and cisatracurium-induced neuromuscular block at the laryngeal adductors (LA).

METHODS

One hundred four patients were randomly assigned to one of eight study groups. They either received rapacuronium 1.5 mg x kg(-1), mivacurium 0.25 mg x kg(-1), rocuronium 0.9 mg x kg(-1) or cisatracurium 0.15 mg x kg(-1). Patients in each treatment group either received edrophonium (0.5 mg x kg(-1)) at 10% recovery of the first twitch (T1) of train-of-four (TOF) at the LA or were allowed to recover spontaneously from neuromuscular block. The effect of antagonism on speed of recovery of neuromuscular function at the LA was evaluated.

RESULTS

The time to recovery to a TOF ratio of 0.9 at the LA, when compared to the spontaneous recovery group, was significantly shortened by the administration of edrophonium in patients receiving rapacuronium [19.2 +/- 7.8 vs 26.2 +/- 4.9 (mean +/- SD) min], rocuronium (24.7 +/- 14.3 vs 44.4 +/- 13.0 min) and cisatracurium (24.2 +/- 5.7 vs 35.1 +/- 7.6 min). Edrophonium administration did not shorten complete recovery from mivacurium-induced block (15.7 +/- 8.0 vs 17.6 +/- 6.1 min).

CONCLUSION

Recovery from rapacuronium-, rocuronium- or cisatracurium- induced neuromuscular block to a TOF ratio of 0.9 as measured at the LA was shortened by the administration of edrophonium, when compared to spontaneous recovery.

[The time-course of action of rapacuronium and mivacurium after early reversal following equally lasting relaxation]

This study was designed to compare the time course of action and the safety profile of Rapacuronium and Mivacurium in day case dental surgery. After Ethics Committee approval 61 healthy adult patients, scheduled for dental day case surgery, were randomised in an assessor-blinded manner to receive either 1.5 mg/kg Rapacuronium with and without 0.05 neostigmine 5 min later (19 patients each) or a total of 0.25 mg/kg Mivacurium (n = 16). Anaesthesia was induced using Propofol 2 - 5.1 mg/kg and Remifentanil 24 - 73 mcg/kg/h and maintained with Desflurane in N2O/O2 (2/1). Endotracheal intubation was performed when maximum blockade was achieved and scored by a blinded intubator. Neuromuscular block was monitored using the train-of-four response to supramaximal stimuli at the ulnar nerve every 15 seconds using acceleromyography (TOF Watch SX). Onset time, clinical duration (reappearance of the third twitch of a TOF-stimulation) and recovery to T4/T1 > 0.9 were recorded. Speed of recovery was evaluated by the time difference between reappearance of the third twitch and T4/T1 > 0.9. The intubating conditions at the time of maximum block revealed no statistically significant differences between the three groups. Changes in blood pressure, heart rate and airway pressure were not significant. Onset time in subjects who received Rapacuronium (99 +/- 29 s) was faster compared to the onset time in those who received Mivacurium (157 +/- 36 s). Also clinical duration was significantly shorter following Rapacuronium without reversal (12 +/- 4 min) as well as with reversal (9 +/- 1 min) compared with Mivacurium (21 +/- 5 min)). Patients treated with Rapacuronium and reversal recovered faster (14 +/- 8 min)) compared to the other two groups (Mivacurium: 20 +/- 6 min, Rapacuronium without reversal: 31 +/- 9 min). The fraction of clinical duration of the total duration was highest following Mivacurium (51 %) when compared with Rapacuronium/Neostigmine (43 %) and Rapacuronium (28 %).

Atracurium, cisatracurium, vecuronium and rocuronium in patients with renal failure

AIM

The cumulative index, the recovery, the onset and the duration of action, of atracurium, cisatracurium, vecuronium and rocuronium in uremic patients undergoing kidney transplantation compared to healthy patients undergoing general surgery were studied.

METHODS

In all patients (64 uremic vs 62 "healthy" patients) after anesthesia induction, atracurium 0.5 mgxkg(-1) or cisatracurium 0.15 mgxkg(-1) or vecuronium 0.1 mgxkg(-1) or rocuronium 0.6 mgxkg(-1) were administered, and at the end of surgery when T1 reached 25% neostigmine 0.05 mgxkg(-1) was given. Neuro-muscu-lar transmission was monitored by accelerometry (TOF-GUARD, Organon).

RESULTS

Cumulative index of vecuronium (1.3+/-0.1 vs 1.06+/-0.11, p<0.001) and rocuronium (1.45+/-0.18 vs 1.04+/-0.16, p<0.001), recovery index (time of T1 25-75) of atracurium (14.2+/-5 vs 9+/-4, p<0.005), cisatracurium (18.7+/-3 vs 9.1, p<0.001), vecuronium (18.5+/-3 vs 12.5+/-3, p<0.001) and rocuronium (18+/-6 vs 11+/-4, p<0.001) and interval T1 25% to TOF 0.8 of cisatracurium (20.5+/-1.2 vs 16+/-2.1, p<0.001) and vecuronium (27+/-6.3 vs 20+/-3.3, p<0.001) were longer in uremic patients. The onset time and the duration of action of atracurium, cisatracurium, vecuronium and rocuronium were similar in all groups compared to controls one.

CONCLUSION

In patients with renal failure the use of atracurium, cisatracurium, vecuronium and rocuronium is suitable and predictable in terms of onset, and duration of action. Care has to be taken to vecuronium and rocuronium cumulative index. Neuromuscular trasmission has to be always monitored.

Effect of milrinone on vecuronium-induced neuromuscular block

We examined the effect of milrinone, a phosphodiesterase III inhibitor, on neuromuscular block induced by vecuronium. Thirty adult patients were randomly assigned to one of two equal groups: the milrinone group and the control group. Subjects in the milrinone group received an intravenous loading dose of milrinone 5 microg x kg-1x min-1 for 10 min, followed by an infusion at a rate of 0.5 microg x kg-1x min-1. Subjects in the control group received normal saline at a rate of 0.1 ml x kg-1 x h-1. Thirty minutes after the beginning of the infusion of milrinone, anaesthesia was induced with intravenous thiopental 4 mg x kg-1 and fentanyl 2 microg x kg-1, and was maintained with isoflurane in oxygen and nitrous oxide. Neuromuscular blockade was monitored electromyographically at the adductor pollicis muscle. The times from the administration of vecuronium 0.1 mg.kg-1 to the onset of neuromuscular block and the return of the first, second, third, and fourth response of the train-of-four were compared between the two groups. Times to the recovery of the ratio of the first twitch to the control twitch to 25%, 50% and 75%, and times to the recovery of train-of-four ratio to 25%, 50% and 75% were also compared between the two groups. The onset of neuromuscular block in the milrinone group was significantly slower than in the control group. The times to the returns of the four twitches of the train-of-four, times to recovery of the ratio of the first twitch to the control twitch to 25% and 50%, and the times to the recovery of the train-of-four ratio to 25% and 50% were significantly shorter in the milrinone group than in the control group. We conclude that milrinone delays the onset of neuromuscular blockade but hastens its recovery in anaesthetised patients receiving vecuronium.

Novel piperidinium and pyridinium agents as water-soluble acetylcholinesterase inhibitors for the reversal of neuromuscular blockade

A series of piperidinium and pyridinium agents containing a common structural fragment of 5,6-dimethoxybenzothiophene have been synthesised as water-soluble acetylcholinesterase inhibitors. Several compounds, for example 42 (AChE IC(50) 0.03 microM) have been found to reverse the neuromuscular blockade induced by vecuronium bromide in vitro and in vivo. Coupled with their high water solubility (up to 30-60 mg/mL), these compounds are potentially useful as intravenous reversal agents of neuromuscular blocking agents in surgical anaesthesia.

Quaternary salts of E2020 analogues as acetylcholinesterase inhibitors for the reversal of neuromuscular block

A series benzylpiperidinium and benzylpyridinium quaternary salts have been synthesised and tested for inhibition of acetylcholinesterase and reversal of neuromuscular block induced by vecuronium. Several potent reversal agents have been identified and their haemodynamic effects measured.

The influence of mild hypothermia on the pharmacokinetics and time course of action of neostigmine in anesthetized volunteers

BACKGROUND

The pharmacokinetics, maximum effect, and time course of action of neostigmine were studied in seven human volunteers.

METHODS

Each volunteer was studied twice, during both normothermia and hypothermia. Anesthesia was induced with 30 microg/kg alfentanil and 3 mg/kg propofol, and was maintained with 60-70% nitrous oxide and 0.7-0.9% isoflurane. The mechanical response of the adductor pollicis to train-of-four stimulation of the ulnar nerve was recorded, and central body temperature maintained stable at either less than 34.5 degrees C or greater than 36.5 degrees C by surface cooling or warming. Before neostigmine administration, a stable 5% twitch height was obtained by an infusion of vecuronium, and the infusion rate remained unchanged thereafter. Neostigmine, 70 microg/kg, was then infused over 2 min, and blood samples for estimation of neostigmine concentrations were collected at intervals for 240 min.

RESULTS

With hypothermia, the central volume of distribution of neostigmine decreased by 38%, and onset time of maximum effect increased (4.6 vs. 5.6 min). Hypothermia did not change the clearance (696 ml/min), maximum effect, or duration of action of neostigmine.

CONCLUSIONS

The efficacy of neostigmine as an antagonist of vecuronium-induced neuromuscular block is not altered by mild hypothermia.

A comparison of neuromuscular effects, tracheal intubating conditions, and reversibility of rapacuronium versus mivacurium in female patients

IMPLICATIONS

Rapacuronium is a new, rapid-onset, short-duration, nondepolarizing neuromuscular blocking drug. We evaluated the intubating conditions at maximum block after the administration of rapacuronium or mivacurium in female patients undergoing laparoscopy. We also evaluated the neostigmine-induced reversibility of neuromuscular block after this single dose of rapacuronium or mivacurium.

Rapacuronium: clinical pharmacology

The need for a rapid-acting non-depolarizing neuromuscular blocking agent with a short duration of action resulted in the synthesis of rapacuronium. The onset of maximum block with rapacuronium occurs in 60-90 s with doses of 1.5-2.5 mg kg-1 with a duration of clinical relaxation of 15-30 min. Rapacuronium provides clinically acceptable intubating conditions in 60 s in a majority of patients with these doses, although the conditions are somewhat inferior to those obtained with succinylcholine in lightly anaesthetized patients, such as those undergoing a rapid-sequence induction. The main drawbacks of rapacuronium are the occurrence of dose-related pulmonary side-effects (increased airway pressure and/or overt bronchospasm) and hypotension and tachycardia. The cause of pulmonary side-effects is not certain but these have been serious enough to make its worldwide introduction doubtful.

The effect of ulinastatin pre-treatment on vecuronium-induced neuromuscular block in patients with hepatic cirrhosis

The aim of this study was to investigate the effect of ulinastatin, a protease inhibitor, on the neuromuscular block produced by vecuronium in patients with hepatic cirrhosis. Thirty adult patients with hepatic cirrhosis were randomly allocated to receive ulinastatin (cirrhosis/ulinastatin group, n = 15) or saline (cirrhosis/saline group, n = 15). Fifteen healthy adult patients without hepatic cirrhosis comprised a control group. Patients were given a standardised anaesthetic that included nitrous oxide and isoflurane in oxygen, and fentanyl. A bolus dose of ulinastatin 5000 unit x kg(-1) was given to members of the cirrhosis/ulinastatin group. The same volume of normal saline was given to the other two groups. Two minutes later, vecuronium 0.1 mg x kg(-1) was given. The onset of neuromuscular block was significantly slower in the cirrhosis/ulinastatin group than in the cirrhosis/saline and control groups (p < 0.05). Spontaneous recovery of neuromuscular function was significantly quicker in the cirrhosis/ulinastatin and control groups than in the cirrhosis/saline group (p < 0.05). The time course of recovery in the cirrhosis/ulinastatin and control groups was similar. We conclude that in cirrhotic patients, ulinastatin delays the onset of neuromuscular block produced by vecuronium. After pretreatment with ulinastatin, the speed of recovery from neuromuscular block in patients with cirrhosis becomes similar to that seen in healthy patients.

Postoperative residual block after intermediate-acting neuromuscular blocking drugs

The frequency and duration of postoperative residual neuromuscular block on arrival of 150 patients in the recovery ward following the use of vecuronium (n = 50), atracurium (n = 50) and rocuronium (n = 50) were recorded. Residual block was defined as a train-of-four ratio of <0.8. An additional group of 10 patients received no neuromuscular blocking drugs during anaesthesia. The incidence of postoperative residual neuromuscular block was 64%, 52% and 39% after the use of vecuronium, atracurium and rocuronium, respectively. Similar numbers of patients were not able to maintain a sustained head or leg lift for 5 s on arrival in the recovery ward. The mean [range] times to attaining a train-of-four ratio of > or =0.8 after arrival in the recovery ward were 9.2 [1-61], 6.9 [1-24] and 14.7 [1.5-83] min for vecuronium, atracurium and rocuronium, respectively. None of the 10 patients who did not receive neuromuscular blocking drugs had train-of-four ratios <0.8 on arrival in the recovery ward. It is concluded that a large proportion of patients arrive in the recovery ward with a train-of-four ratio <0.8, even with the use of intermediate-acting neuromuscular blocking drugs. Although the residual block is relatively short lasting, it may occasionally be prolonged, requiring close observation and monitoring of such patients in the recovery ward.

Comparison of recovery following rapacuronium, with and without neostigmine, and succinylcholine

The neuromuscular blocking effects of a single dose of rapacuronium 1.5 mg x kg(-1) with or without reversal with neostigmine have been examined in the present study and compared with a dose of succinylcholine 1.0 mg x kg(-1). Neuromuscular block was measured mechanomyographically using train-of-four stimulation. Complete block occurred within 1 min with both agents. Twenty-five per cent recovery of the first response of the train-of-four occurred in a median [range] time of 7.6 [5.7-11.3] min in the succinylcholine group and in 14.2 [8.8-23.6] and 15.1 [9.6-23.4] min in the rapacuronium groups with and without neostigmine reversal, respectively. Spontaneous recovery to a train-of-four ratio of 0.8 took 33.4 [20.0-79.0] min with rapacuronium but this was reduced to about 21.2 [13.9-33.7] min when neostigmine was administered at 25% recovery of first twitch of the train-of-four.

Residual curarization in the recovery room after vecuronium

We have investigated residual block after anaesthesia which included the use of the neuromuscular blocking agent vecuronium but no anticholinesterase, in 568 consecutive patients on admission to the recovery room. The ulnar nerve was stimulated submaximally using TOF stimulation (30 mA). Postoperative residual curarization was defined as a TOF ratio < 0.7. Of the 568 patients, 239 (42%) had a TOF < 0.7 in the recovery room. These patients had received a larger cumulative dose of vecuronium than patients who had full recovery (mean 7.7 (SD 3.6) mg vs 6.2 (2.7) mg; P < 0.05) and a shorter time had elapsed since the last vecuronium dose (117 (70) min vs 131 (80) min; P < 0.05). Of 435 patients whose trachea was extubated, 145 (33%) exhibited inadequate recovery from neuromuscular block. Six of these had one or no response to TOF stimulation and were reintubated. In the remaining 139 patients, neuromuscular block was successfully antagonized. Only 20 patients (3.5%) remembered TOF stimulation when questioned 2 h later in the recovery room, and discomfort associated with it was assessed using a visual analogue scale before discharge. We conclude that it is necessary to antagonize residual block produced by vecuronium.

Antagonism of rapacuronium using edrophonium or neostigmine: pharmacodynamics and pharmacokinetics

We have studied the pharmacodynamics and pharmacokinetics of rapacuronium (Org 9487) in 70 healthy patients. Neuromuscular transmission was monitored using TOF stimulation of the ulnar nerve and mechanomyography of the adductor pollicis muscle. Half of the patients were given a single dose of rapacuronium 1.5 mg kg-1 and the remainder rapacuronium 1.5 mg kg-1 with three incremental doses of 0.5 mg kg-1, each given when T1/T0 had recovered to 25%. In all patients, neuromuscular block was antagonized using neostigmine 0.05 mg kg-1 or edrophonium 1.0 mg kg-1 (allocated randomly), 2 min after the final dose of rapacuronium. All patients developed complete block after rapacuronium 1.5 mg kg-1. Mean onset time was 66 (SD 24) s. In patients who received an antagonist 2 min after the first dose of rapacuronium, time to recovery of T1/T0 to 25% was similar after neostigmine (9.8 (3.8) min) and edrophonium (10.3 (4.3) min): in patients who received incremental doses of rapacuronium, spontaneous recovery of T1/T0 to 25% after the first dose was 18.9 (4.7) min. In those who received an antagonist 2 min after the first dose of rapacuronium, times to recovery of T4/T1 to 0.7 were also similar after neostigmine (23.7 (7.7) min) and edrophonium (29.1 (10.7) min). After three incremental doses of rapacuronium, there was a longer time to recovery of T1/T0 = 25% after neostigmine compared with edrophonium (5.1 (1.0) vs 3.3 (1.3) min; P < 0.05) but more rapid recovery to T1/T0 = 75% (10.1 (2.9) vs 16.8 (10.1) min; P < 0.05) and T4/T1 = 0.7 (19.8 (6.3) vs 35.1 (10.4) min; P < 0.05). A three-compartment pharmacokinetic model was justified. Typical values for clearance and initial volume of distribution (V1) were 4.4 ml kg-1 min-1 and 94.8 ml kg-1, respectively. In females, clearance was decreased by 38.5% compared with males and V1 was decreased by 25% in patients aged more than 65 yr.

Early and late reversal of rocuronium and vecuronium with neostigmine in adults and children

We investigated the influence of the timing of neostigmine administration on recovery from rocuronium or vecuronium neuromuscular blockade. Eighty adults and 80 children were randomized to receive 0.45 mg/kg rocuronium or 0.075 mg/kg vecuronium during propofol/fentanyl/N2O anesthesia. Neuromuscular blockade was monitored by train-of-four (TOF) stimulation and adductor pollicis electromyography. Further randomization was made to control (no neostigmine) or reversal with 0.07 mg/kg neostigmine/0.01 mg/kg glycopyrrolate given 5 min after relaxant, or first twitch (T1) recovery of 1%, 10%, or 25%. Another eight adults and eight children received 1.5 mg/kg succinylcholine. At each age, spontaneous recovery of T1 and TOF was similar after rocuronium and vecuronium administration but was more rapid in children (P < 0.05). Spontaneous recovery to TOF0.7 after rocuronium and vecuronium administration in adults was 45.7 +/- 11.5 min and 52.5 +/- 15.6 min; in children, it was 28.8 +/- 7.8 min and 34.6 +/- 9.0 min. Neostigmine accelerated recovery in all reversal groups (P < 0.05) by approximately 40%, but the times from relaxant administration to TOF0.7 were similar and independent of the timing of neostigmine administration. Recovery to T1 90% after succinylcholine was similar in adults (9.4 +/- 5.0 min) and children (8.4 +/- 1.1 min) and was shorter than recovery to TOF0.7 in any reversal group after rocuronium or vecuronium administration. Recovery from rocuronium and vecuronium blockade after neostigmine administration was more rapid in children than in adults. Return of neuromuscular function after reversal was not influenced by the timing of neostigmine administration. These results suggest that reversal of intense rocuronium or vecuronium neuromuscular blockade need not be delayed until return of appreciable neuromuscular function has been demonstrated.

IMPLICATIONS

These results suggest that reversal of intense rocuronium or vecuronium neuromuscular blockade need not be delayed until return of appreciable neuromuscular function has been demonstrated. Although spontaneous and neostigmine-assisted recovery is more rapid in children than in adults, in neither is return of function as rapid as after succinylcholine administration.

The effect of cerebral palsy on the action of vecuronium with or without anticonvulsants

Patients with cerebral palsy who are treated with anticonvulsant medication are resistant to vecuronium. We examined the contributions to vecuronium resistance made by cerebral palsy and anticonvulsants in a study of children with cerebral palsy and a control group. The acceleromyographic responses of the following three groups of children were studied: children with cerebral palsy not taking anticonvulsant medication (n = 11); children with cerebral palsy taking anticonvulsant medication (n = 8); and a control group of children who did not have cerebral palsy and were not taking anticonvulsant treatment (n = 10). Using a standardised technique, general anaesthesia was induced and maintained with 0.5-1. 5% isoflurane in a 60/40 nitrous oxide in oxygen mixture. After a stabilisation period which was performed with supramaximal train-of-four stimuli (2 Hz every 15 s) an intubating dose of vecuronium 0.1 mgkg-1 was administered. The first twitch of the train-of-four response (T1), the onset time, the times to 25, 50, 75 and 90% recovery of T1, recovery index, and the time to 70% recovery of train-of-four ratio were recorded. Recovery times to T1 and train-of-four responses were reduced significantly in both groups of children with cerebral palsy compared with the control group. These results suggest that children with cerebral palsy display resistance to vecuronium whether or not they are taking anticonvulsant drugs.

Spontaneous or neostigmine-induced recovery after maintenance of neuromuscular block with Org 9487 (rapacuronium) or rocuronium following an initial dose of Org 9487

We have examined spontaneous and neostigmine-induced recovery after an initial dose of Org 9487 1.5 mg kg-1 followed by three repeat doses of Org 9487, a 30-min infusion of Org 9487 or two incremental doses of rocuronium. Mean clinical duration after incremental doses of Org 9487 0.5 mg kg-1 increased from 12.3 (SD 3.4) min to 14.0 (4.0) and 15.9 (5.9) min (P < 0.01), and after rocuronium from 14.4 (5.2) min to 19.2 (5.9) min (P < 0.01). Times for spontaneous recovery from a T1 of 25% to a TOF ratio of 0.8 after the last bolus dose of Org 9487 and after a 30-min infusion were 72.4 (16.5) and 66.1 (26.9) min compared with 36.7 (15.8) min in the group receiving reocuronium. These times were significantly reduced to 9.9 (4.5), 8.6 (6.1) and 5.7 (2.5) min, respectively, after neostigmine administration at a T1 of 25% (P < 0.05). We conclude that administration of Org 9487 by repeat bolus doses or infusion was associated with slow spontaneous recovery but neostigmine administration resulted in adequate recovery in less than 10 min.

Antagonism of vecuronium-induced neuromuscular block in patients pretreated with magnesium sulphate: dose-effect relationship of neostigmine

We have investigated the dose-effect relationship of neostigmine in antagonizing vecuronium-induced neuromuscular block with and without magnesium sulphate (MgSO4) pretreatment. Neuromuscular block was assessed by electromyography with train-of-four (TOF) stimulation. First, we determined neostigmine-induced recovery in patients pretreated with MgSO4 (group A) or saline (group B) (n = 12 each). The height of T1, 5 min after neostigmine, was 43 (7)% in group A and 65 (6)% in group B (P < 0.01). Respective values after 10 min were 59 (7)% and 83 (5)% (P < 0.01). TOF ratio, 5 min after neostigmine, was 29 (6)% in group A and 29 (5)% in group B. Respective values after 10 min were 38 (11)% and 51 (7)% (P < 0.01). To gain insight into the mechanisms leading to delayed recovery after MgSO4, we calculated assisted recovery, defined as neostigmine-induced recovery minus mean spontaneous recovery. Spontaneous recovery was assessed in another 24 patients. Patients in group C received MgSO4/vecuronium and patients in group D vecuronium only (n = 12 each). Five minutes after neostigmine, assisted recovery was 22 (7)% in the MgSO4 pretreated patients and 28 (6)% in controls (P < 0.05). Ten minutes after neostigmine, values were 24 (7)% and 22 (6)%. Maximum assisted recovery was not influenced by MgSO4 pretreatment (27 (6)% in group A and 32 (6)% in group B) and time to maximum effect was comparable between groups: 6 (4-10) min and 7 (5-8) min, respectively. We conclude that neostigmine-induced recovery was attenuated in patients treated with MgSO4. This was mainly a result of slower spontaneous recovery and not decreased response to neostigmine.

Susceptibility to upper airway obstruction during partial neuromuscular block

BACKGROUND

Airway obstruction after anesthesia may be caused or exaggerated by residual neuromuscular block, with loss of muscle support for collapsible upper airway structures.

METHODS

Six male volunteers were studied before treatment, during stable partial neuromuscular block with vecuronium at a mean train-of-four (TOF) ratio of 50% (95% CI, 36-61%), and after reversal by neostigmine. Catheter-mounted transducers were placed in the pharynx and esophagus to estimate, respectively, the upper airway resistance, and the work of breathing (calculated as the time integral of the inspiratory pressure developed by the respiratory muscles, esophageal pressure time product) during quiet breathing, during breathing 5% carbon dioxide, and while breathing with an inspiratory resistor. Breathing with pressure at the airway opening held at pressures from -5 to 40 cm H2O were also tested to assess airway collapsibility.

RESULTS

Although breathing through a resistor increased upper airway resistance from 1.2 (0.67, 1.72) cm H2O x l(-1) x s to 2.5 (1.32, 3.38) cm H2O x l(-1) x s, and carbon dioxide stimulation reduced resistance to 0.8 (0.46, 1.33) cm H2O x l(-1) x s, no effect of partial neuromuscular block (mean TOF ratio, 52%) on upper airway properties could be shown.

CONCLUSIONS

Neuromuscular block with a TOF ratio of 50% can be present yet clinically difficult to detect in patients recovering from anesthesia. This degree of block has no effect on airway patency in volunteers, even during challenge. Airway obstruction during recovery from anesthesia thus is more likely to be caused by residual effects of general anesthetic agents or centrally acting analgesics, either alone or perhaps in concert with residual neuromuscular block.

The clinical neuromuscular pharmacology of cisatracurium versus vecuronium during outpatient anesthesia

Neither comparisons of the clinical neuromuscular effects of cisatracurium and vecuronium nor comparative studies of their antagonism by neostigmine have been reported. In addition, the efficacy of administering cisatracurium in divided doses has not been investigated. Accordingly, we applied supramaximal electrical stimuli to the ulnar nerve of 165 ASA physical status I and II patients receiving nitrous oxide/alfentanil/propofol anesthesia. Forty-five patients received cisatracurium 5, 10, or 15 microg/kg, and the evoked response at the adductor pollicis was recorded for 15 min. One hundred-twenty patients received cisatracurium 5, 10, or 15 microg/kg or normal saline placebo followed 5 min later by either cisatracurium 100 microg/kg or vecuronium 100 microg/kg (always after placebo). Time to clinical onset (maximal ablation of single twitch response) was measured. When the evoked response spontaneously recovered to 10% of control height, neostigmine 5, 10, 30, or 50 microg/kg or placebo was administered, and recovery of neuromuscular function was recorded for the next 15 min. The clinical onset of vecuronium without priming (2.8 +/- 0.8 min) (mean +/- SD) was significantly (P < 0.05) faster than the onset of cisatracurium without priming (4.6 +/- 1.4 min). Cisatracurium 5, 10, or 15 microg/kg administered before cisatracurium 100 microg/kg significantly (P < 0.05) accelerated the time to complete ablation of the evoked response (3.9 +/- 0.9, 2.9 +/- 0.8, or 3.0 +/- 0.9 min, respectively) compared with cisatracurium 100 microg/kg without priming. The dose of neostigmine required to achieve 50% assisted recovery of the train-of-four ratio at 5 min was significantly (P < 0.05) smaller in patients who received vecuronium (29.1 [17.9-55.3] microg/kg) (mean [95% confidence interval]) compared with those who received cisatracurium (53.7 [31.6-131.5] microg/kg). Given its faster clinical onset and greater sensitivity to antagonism by neostigmine, we conclude that vecuronium may be more suitable than cisatracurium for use in outpatient anesthesia.

IMPLICATIONS

We investigated the onset of muscle relaxation using intravenous vecuronium and cisatracurium and assessed the ability of neostigmine to antagonize (reverse) this effect. Our results suggest that vecuronium works faster than cisatracurium and is more sensitive to neostigmine. Vecuronium therefore may be more useful than cisatracurium in outpatient anesthesia.

Factors affecting neostigmine reversal of vecuronium block during sevoflurane anaesthesia

We examined the influence of the concentration of sevoflurane and the degree of muscle block at the time of reversal on the activity of neostigmine. Ninety ASA 1-2 patients were anaesthetised with 0.2, 0.7 or 1.2 MAC of sevoflurane (30 patients each) in 66% nitrous oxide in oxygen. The electromyographic (EMG) response of the adductor digiti minimi was monitored at 20-s intervals after train-of-four stimulation of the ulnar nerve. The initial neuromuscular block was produced by vecuronium 100 micrograms.kg-1. When the amplitude of the first response (T1) values had recovered to 10%, 25% or 40% of the control, neostigmine 40 micrograms.kg-1 was administered. The train-of-four ratio values were recorded at 1-min intervals during the subsequent 15-min period. Higher endtidal concentrations (p < 0.0001) and more pronounced block at the time of reversal (p < 0.0001) were associated with a delayed recovery in the train-of-four ratio. In addition, the train-of-four ratio 15 min after neostigmine administration was more dependent on the sevoflurane concentration than on the degree of block present (p < 0.0001). These results confirm that neostigmine (40 micrograms.kg-1) can reverse vecuronium-induced but not sevoflurane-induced neuromuscular block.

[Effects of halothane and sevoflurane on reversal of neuromuscular blockade induced by vecuronium in man]

To evaluate residual effects of inhalational anesthetics after reversal of neuromuscular blocking agent, neuromuscular function was monitored after halothane or sevoflurane anesthesia in thirty-seven patients (ASA physical status I or II) for elective surgery after obtaining informed consent. Electromyograph of the adductor pollicis muscle in response to train of four (TOF) stimulation was monitored throughout the study. The first twitch of TOF (T1; % of its control) and the ratio of the fourth twitch to the first twitch of TOF (T4/T1; TR) were recorded at 0, 2, 5, 10, and 15 min after reversal. The patients were divided into five groups; 1) the fentanyl group (n = 7) received fentanyl/N2O; 2) in the halothane stop group (n = 6), halothane was discontinued at least fifteen minutes before neostigmine administration; 3) in the halothane stable group (n = 7), 0.7% halothane was maintained until fifteen minutes after neostigmine; 4) in the sevoflurane stop group (n = 12), sevoflurane was discontinued fifteen minutes before the reversal; 5) in the sevoflurane stable group (n = 5), 3% sevoflurane was maintained until fifteen minutes after the reversal. Anesthesia was induced by thiopental 4 mg.kg-1 and suxamethonium 1 mg.kg-1 and the patients were intubated. After initial dose of vecuronium 0.1 mg.kg-1, the additional dose of 0.02 mg.kg-1 was administered to maintain T1 under 10% of the control value. At the end of the surgery atropine 0.015 mg.kg-1 and neostigmine 0.04 mg.kg-1 were administered to reverse vecuronium when T1 had recovered to 25% of its control. Halothane groups did not differ from fentanyl group. Recovery of T1 at 15 min was suppressed after discontinuation of sevoflurane (86.0 +/- 8.2%) in comparison with fentanyl (97.0 +/- 8.3%). Both T1 (75.4 +/- 12.2%) and TR (68.0 +/- 12.6%) at 15 min after the reversal during 3% sevoflurane inhalation were below those of the stable group. We conclude that the residual sevofulrane after discontinuation of inhalation may impair the neuromuscular transmission after the reversal of neuromuscular blockade. Neuromuscular function should be monitored after the end of anesthesia even though the patient is fully awake.

Neuromuscular blocking action of suxamethonium after antagonism of vecuronium by edrophonium, pyridostigmine or neostigmine

The reported effects of edrophonium on a subsequent dose of suxamethonium are variable and the effects of pyridostigmine have not been evaluated extensively. We have studied this interaction in patients anaesthetized with propofol and sufentanil. After recovery from an initial bolus (1 mg kg-1) of suxamethonium, vecuronium was infused to produce 75% block. After 30 min, the infusion was discontinued and saline 5 ml, edrophonium 0.75 mg kg-1, pyridostigmine 0.24 mg kg-1 or neostigmine 0.05 mg kg-1 was given. Fifteen minutes later the mean durations of a second bolus of suxamethonium were: 10.5 (SD 3.9) min (saline), 10.9 (3.7) min (edrophonium), 18.7 (5.4) min (pyridostigmine) and 23.8 (7.4) min (neostigmine). Corresponding plasma cholinesterase activities (percentage of baseline) were: 91 (18), 87 (9), 21 (10) and 52 (26). When both treatment groups and individual patients were compared, the changes in duration of action did not correlate with changes in cholinesterase activity. These data suggest that other mechanisms in addition to cholinesterase inhibition may contribute to this drug interaction.

Is recovery of neuromuscular transmission complete after the use of neostigmine to antagonize block produced by rocuronium, vecuronium, atracurium and pancuronium?

To test if recovery of neuromuscular transmission is complete after the use of neostigmine under standardized conditions, we have measured adductor pollicis mechanical activity in response to 0.1 Hz (twitch height), train-of-four (TOF) and 100 Hz (RF 100 Hz) ulnar nerve stimulations. We studied 56 adult anaesthetized (thiopentone, fentanyl, nitrous oxide in oxygen) patients, allocated randomly to one of four groups (n = 14) to receive rocuronium (group Roc), vecuronium (group Vec), atracurium (group Atr) or pancuronium (group Pan). Recovery of neuromuscular transmission was studied for 15 min after neostigmine 40 micrograms kg-1 was given at 25% recovery of twitch height. Fifteen minutes after antagonism, the TOF ratio was 0.91 (SEM 0.01), 0.88 (0.02) and 0.92 (0.01) (ns), and RF 100 Hz was 0.78 (0.01), 0.79 (0.02) and 0.78 (0.01) (ns) respectively, in patients in groups Roc, Vec and Atr, respectively. In patients in group Pan, TOF ratio and RF 100 Hz were only 0.76 (0.01) and 0.33 (0.04) respectively (P < 0.01, one-way analysis of variance, Duncan's multiple classification range tests). In contrast with pancuronium, antagonism of rocuronium-, vecuronium- and atracurium-induced neuromuscular blocks produced a similar high degree of recovery of neuromuscular transmission.

[Caffeine antagonizes the neuromuscular blockade of vecuronium]

It is known that theophylline antagonizes the neuromuscular blockade in animals and case reports, where the same phenomenon has been observed in man, are described. One patient is described where another methylxantine-caffeine-caused resistance to neuromuscular blockade by vecuronium, but successful blockade was achieved by pancuronium.

Conditions to optimise the reversal action of neostigmine upon a vecuronium-induced neuromuscular block

BACKGROUND

Since neostigmine was introduced for reversal of neuromuscular block, there has been controversy about the optimum dose for antagonizing neuromuscular block. The purpose of this study was to characterise recovery of neuromuscular transmission following a vecuronium-induced block 15 min after neostigmine administration using different stimulation patterns, and to determine the effects of different doses of neostigmine given at various pre-reversal twitch heights.

METHODS

Adductor pollicis (AP) mechanical activity in response to low (0.1 and 2 Hz) and high (50 and 100 Hz) frequency stimulation, was recorded 15 min after 20, 40 and 80 micrograms/kg neostigmine, given to reverse a vecuronium-induced block at 10, 25 and 50% pre-reversal twitch height (TH). Fifty four ASA class I and II anaesthetised (methohexital, fentanyl, N2O/O2) young adult patients were studied and randomly allocated into 9 groups of 6 patients each.

RESULTS

In contrast to twitch height (TH) and residual force after 50 Hz, 5 s tetanic stimulation (RF50Hz), the greater sensitivity of train-of-four (TOF) ratio and residual force after 100 Hz, 5 s tetanic stimulation (RF100Hz) points out the best reversal conditions (prereversal TH and the optimal neostigmine dose) (P < 0.001, two-way analysis of variance). The highest reversal scores (about 0.9 TOF ratio and RF100Hz) were obtained when 40 micrograms/kg of neostigmine was given at 25 and 50% TH. A 0.9 TOF ratio was also observed when 40 micrograms/kg of neostigmine was given at 10% TH, but, under these conditions, RF100Hz was only 0.6 (P < 0.05, Duncan test).

CONCLUSION

To optimise the reversal action of neostigmine in order to obtain the highest neuromuscular transmission recovery (0.9 TOF ratio and RF100Hz) during a vecuronium-induced neuromuscular block, the 40 micrograms/kg dose has to be given at 25 to 50% recovery of TH.