Onset and Duration of Rocuronium-induced Meeting Abstracts in Patients with Duchenne Muscular Dystrophy

Spontaneous recovery from neuromuscular block after a single dose of a muscle relaxant in pediatric patients: A systematic review using a network meta-analytic and meta-regression approach

BACKGROUND

Age-related differences in the pharmacokinetics and pharmacodynamics of neuromuscular blocking agents (NMBAs) and the short duration of many surgical procedures put pediatric patients at risk of postoperative residual curarization (PORC). To date, the duration of neuromuscular blocking agent effect in children has not been analyzed in a quantitative review. The current meta-analysis aimed to compare spontaneous recovery following administration of various types and doses of neuromuscular blocking agents and to quantify the effect of prognostic variables associated with the recovery time in pediatric patients.

METHOD

We searched for randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that compared the time to 25% T1 (t25), from 25% to 75% T1 (RI25-75), and to ≥90% train-of-four (tTOF90) neuromuscular recovery between common neuromuscular blocking agent treatments administered as a single bolus to healthy pediatric participants. We compared spontaneous t25, RI25-75, and tTOF90 between (1) neuromuscular blocking agent treatments and (2) age groups receiving a given neuromuscular blocking agent intervention and anesthesia technique. Bayesian random-effects network and pairwise meta-analyses along with meta-regression were used to evaluate the results.

RESULTS

We used data from 71 randomized controlled trials/controlled clinical trials including 4319 participants. Network meta-analysis allowed for the juxtaposition and ranking of spontaneous t25, RI25-75, and tTOF90 following common neuromuscular blocking agent interventions. For all neuromuscular blocking agents a log-linear relationship between dose and duration of action was found. With the neuromuscular blocking agent treatments studied, the average tTOF90 (mean[CrI95]) in children (>2-11 y) was 41.96 [14.35, 69.50] and 17.06 [5.99, 28.30] min shorter than in neonates (<28 d) and infants (28 d-12 M), respectively. We found a negative log-linear correlation between age and duration of neuromuscular blocking agent effect. The difference in the tTOF90 (mean[CrI95]) between children and other age groups increased by 21.66 [8.82, 34.53] min with the use of aminosteroid neuromuscular blocking agents and by 24.73 [7.92, 41.43] min with the addition of sevoflurane/isoflurane for anesthesia maintenance.

CONCLUSIONS

The times to neuromuscular recovery are highly variable. These can decrease significantly with age and are prolonged when volatile anesthetics are administered. This variability, combined with the short duration of many pediatric surgical procedures, makes quantitative neuromuscular monitoring mandatory even after a single dose of neuromuscular blocking agent.

[Trigger-free anesthesia : Indications and safe application]

The safe anesthesiological care of patients with neuromuscular diseases poses a particular challenge for anesthetists. Only a small group of muscle diseases and syndromes are associated with an increased risk of malignant hyperthermia and therefore require trigger-free anesthetic procedures avoiding volatile anesthetics and succinylcholine. These diseases are frequently associated with mutations in the RYR1, CACNA1S or STAC-3 genes. In other neuromuscular diseases, anesthetic-induced rhabdomyolysis can occur. Therefore, volatile anesthetics should be avoided in these patients in addition to the contraindication for succinylcholine. In other neuromuscular diseases the risk of a propofol infusion syndrome or myotonic crises can be elevated or the duration of the effect of non-depolarizing muscle relaxants can be changed in an incalculable way. In every case an individual anesthetic aproach including the avoidance of potential pharmacological or non-pharmacological triggers is essential for the safety of the patients.

European Neuromuscular Centre consensus statement on anaesthesia in patients with neuromuscular disorders

BACKGROUND AND PURPOSE

Patients with neuromuscular conditions are at increased risk of suffering perioperative complications related to anaesthesia. There is currently little specific anaesthetic guidance concerning these patients. Here, we present the European Neuromuscular Centre (ENMC) consensus statement on anaesthesia in patients with neuromuscular disorders as formulated during the 259th ENMC Workshop on Anaesthesia in Neuromuscular Disorders.

METHODS

International experts in the field of (paediatric) anaesthesia, neurology, and genetics were invited to participate in the ENMC workshop. A literature search was conducted in PubMed and Embase, the main findings of which were disseminated to the participants and presented during the workshop. Depending on specific expertise, participants presented the existing evidence and their expert opinion concerning anaesthetic management in six specific groups of myopathies and neuromuscular junction disorders. The consensus statement was prepared according to the AGREE II (Appraisal of Guidelines for Research &amp; Evaluation) reporting checklist. The level of evidence has been adapted according to the SIGN (Scottish Intercollegiate Guidelines Network) grading system. The final consensus statement was subjected to a modified Delphi process.

RESULTS

A set of general recommendations valid for the anaesthetic management of patients with neuromuscular disorders in general have been formulated. Specific recommendations were formulated for (i) neuromuscular junction disorders, (ii) muscle channelopathies (nondystrophic myotonia and periodic paralysis), (iii) myotonic dystrophy (types 1 and 2), (iv) muscular dystrophies, (v) congenital myopathies and congenital dystrophies, and (vi) mitochondrial and metabolic myopathies.

CONCLUSIONS

This ENMC consensus statement summarizes the most important considerations for planning and performing anaesthesia in patients with neuromuscular disorders.

[Anesthesia for patients suffering from neuromuscular diseases]

Neuromuscular diseases (NMD) are a heterogeneous group of motor unit disorders. Common to all is the main clinical symptom of muscle weakness. Depending on entity and phenotype, a broad range of disorders of neuronal, junctional or myocytic structures occurs. In addition to a weakness of the skeletal musculature, NMD can also affect throat musculature, respiratory and heart muscles. The possible consequences are immobility, deformities, tendency to aspiration as well as respiratory and cardiac insufficiency. In the context of surgery and anesthesia, complications that can result from the underlying disease and its interaction with anesthesia must be anticipated and averted. This article describes along the treatment pathway how preoperative evaluation, choice of the anesthetic procedure and postoperative care can be effectively and safely tailored to the needs of patients with NMD. Concise and practical recommendations for carrying out anesthesia for the most important NMDs are presented as well as relevant external sources of practice recommendations.

Anaesthesiological approach to the floppy child

Children with symptoms of hypotonia (reduction of postural tone of lower limbs and trunk with or without changes in phasic tone) are frequently anaesthetized for diagnostic and therapeutic interventions. This review outlines the underlying causes and classifications, and the anaesthesiologic pre- and peri-operative management of hypotonic children. Hypotonia may have a large range of aetiologies that be categorized into central and/or peripheral hypotonia. A multidisciplinary approach towards the (differential) diagnosis of the underlying cause of the symptoms in cooperation with a paediatrician and/or paediatric neurologist is emphasized. Anaesthetic management involves the anticipation of an increased risk in difficult airway management because of macroglossia, reduced mouth opening, obesity and limited neck mobility, which increases with age. There are no specific restrictions towards the use of intravenous or inhalational anaesthetics. Short acting opioids and hypnotics, avoiding neuromuscular blockade, and locoregional techniques are preferred. Most patients are sensitive to the cardiac and depressive effects of anaesthetics and all dystrophic myopathies are considered at risk of malignant hyperthermia. Depolarizing neuromuscular blockers are contraindicated. The use of a peripheral nerve stimulator is recommended to detect the severity of muscle relaxation before extubating. Accurate control and management of IV fluids, electrolytes and temperature is mandatory. Adequate postoperative pain treatment is essential to limit stress and metabolic alteration. Preferably a locoregional technique is used to reduce the increased risk of respiratory depression. A multidisciplinary preoperative approach taking into account the differential diagnosis of the underlying disease of the floppy child is recommended.

Sugammadex: A Limited But Important Role in Emergency Medicine

Sugammadex reverses neuromuscular blockade by the steroidal nondepolarizing neuromuscular blocking agents rocuronium and vecuronium. In 2015, it was approved in the United States by the Food and Drug Administration for adult use. However, there are ongoing clinical trials investigating its use in the pediatric population. Before approval in adult use in the United States, several adverse effects were noted to occur in patients receiving sugammadex in clinical trials including prolonged QT interval, bradycardia, hypersensitivity reactions, and prolongation of coagulation parameters. Additional investigations further elucidated the risks of these adverse events. Sugammadex is approved for use in children older than 2 years in other countries in Europe and Asia. Investigations suggest that the efficacy, safety, and pharmacokinetic profile is similar in children when compared with adults. Published pediatric data favor the use of sugammadex in children older than 2 years, but there are some data in young children younger than 2 years. Case reports discuss the use of sugammadex in pediatric patients with neuromuscular diseases. Although sugammadex is typically used in the operating room for reversing neuromuscular blockade for surgical procedures, there is a small but important role for sugammadex use in the emergency department. In cases where rapid neurological examination is required after neuromuscular blockage with rocuronium or vecuronium, sugammadex can assist in facilitating a timely comprehensive neurological examination where pharmacologic or surgical management may depend on examination findings such as in the case of cerebral vascular accident, status epilepticus, or traumatic brain injury. Some clinicians have advocated for the use of sugammadex in the cannot intubate, cannot ventilate scenario. However, caution should be exercised in this situation as reversal of paralysis can take up to 22 minutes to occur.

Guidelines on muscle relaxants and reversal in anaesthesia

OBJECTIVES

To provide an update to the 1999 French guidelines on "Muscle relaxants and reversal in anaesthesia", a consensus committee of sixteen experts was convened. A formal policy of declaration and monitoring of conflicts of interest (COI) was developed at the outset of the process and enforced throughout. The entire guidelines process was conducted independently of any industrial funding (i.e. pharmaceutical, medical devices). The authors were required to follow the rules of the Grading of Recommendations, Assessment, Development and Evaluation (GRADE®) system to assess the quality of the evidence on which the recommendations were based. The potential drawbacks of making strong recommendations based on low-quality evidence were stressed. Few of the recommendations remained ungraded.

METHODS

The panel focused on eight questions: (1) In the absence of difficult mask ventilation criteria, is it necessary to check the possibility of ventilation via a facemask before muscle relaxant injection? Is it necessary to use muscle relaxants to facilitate facemask ventilation? (2) Is the use of muscle relaxants necessary to facilitate tracheal intubation? (3) Is the use of muscle relaxants necessary to facilitate the insertion of a supraglottic device and management of related complications? (4) Is it necessary to monitor neuromuscular blockade for airway management? (5) Is the use of muscle relaxants necessary to facilitate interventional procedures, and if so, which procedures? (6) Is intraoperative monitoring of neuromuscular blockade necessary? (7) What are the strategies for preventing and treating residual neuromuscular blockade? (8) What are the indications and precautions for use of both muscle relaxants and reversal agents in special populations (e.g. electroconvulsive therapy, obese patients, children, neuromuscular diseases, renal/hepatic failure, elderly patients)? All questions were formulated using the Population, Intervention, Comparison and Outcome (PICO) model for clinical questions and evidence profiles were generated. The results of the literature analysis and the recommendations were then assessed using the GRADE® system.

RESULTS

The summaries prepared by the SFAR Guideline panel resulted in thirty-one recommendations on muscle relaxants and reversal agents in anaesthesia. Of these recommendations, eleven have a high level of evidence (GRADE 1±) while twenty have a low level of evidence (GRADE 2±). No recommendations could be provided using the GRADE® system for five of the questions, and for two of these questions expert opinions were given. After two rounds of discussion and an amendment, a strong agreement was reached for all the recommendations.

CONCLUSION

Substantial agreement exists among experts regarding many strong recommendations for the improvement of practice concerning the use of muscle relaxants and reversal agents during anaesthesia. In particular, the French Society of Anaesthesia and Intensive Care (SFAR) recommends the use of a device to monitor neuromuscular blockade throughout anaesthesia.

Rocuronium-induced neuromuscular block and sugammadex in pediatric patient with duchenne muscular dystrophy: A case Report

INTRODUCTION

Anesthetic management of patients with Duchenne muscular dystrophy (DMD) is complicated because these patients are more sensitive to nondepolarizing neuromuscular blocking agents (NMBAs) and are vulnerable to postoperative complications, such as postoperative residual curarization and respiratory failure. Sugammadex is a new reversal agent for aminosteroidal NMBAs, but its safety in children is controversial.

CLINICAL FEATURES

An 11-year-old boy with DMD underwent general anesthesia for a percutaneous nephrolithotomy. We used rocuronium bromide and sugammadex to reverse the deep neuromuscular block. Reversal of neuromuscular block was done 15 minutes after administration of 2 mg/kg of sugammadex. The patient's recovery from anesthesia was uneventful, and he was discharged to the postoperative recovery ward.

CONCLUSION

A delayed recovery was achieved, but no adverse events were observed, such as recurarization or hypersensitivity to sugammadex. We report safe use of 2 mg/kg of sugammadex to reverse a deep neuromuscular block in a child with DMD.

The kalaemic and neuromuscular effects of succinylcholine in centronuclear myopathy: A pilot investigation in a canine model

BACKGROUND

Myopathies are generally considered to increase the risk for succinylcholine-induced hyperkalaemia and may affect the duration of action of neuromuscular blockers. Centronuclear (myotubular) myopathy (CNM) is congenital and produces various degrees of muscular weakness and associated complications such as respiratory failure. The effects of succinylcholine and the potentially lethal consequences of hyperkalaemia on patients with CNM are unknown due to its rarity. One source of information is the dog, as CNM occurs naturally in dogs. Because of its remarkable similarity with the disease in man, canine CNM can serve as a model to further our knowledge of the effects of succinylcholine.

OBJECTIVES

We examined the kalaemic and neuromuscular effects of succinylcholine in dogs with and without autosomal-recessive CNM.

DESIGN

A prospective, experimental study.

SETTING

Anaesthesiology laboratory, College of Veterinary Medicine, Cornell University, New York, USA.

PATIENTS

Six dogs with autosomal-recessive CNM and six control dogs.

INTERVENTIONS

Dogs received succinylcholine 0.3 mg kg during isoflurane anaesthesia.

MAIN OUTCOME MEASURES

Whole blood potassium concentration was measured 5 min before and after succinylcholine administration. Neuromuscular function was measured with acceleromyography and single twitch stimulation.

RESULTS

All dogs recovered uneventfully from anaesthesia. The increase in potassium concentration [mean (SD)] following succinylcholine was similar between groups: CNM 0.5 (0.4) mmol l and control 0.7 (0.4) mmol l (P = 0.47). Recovery of the single twitch to 25, 75 and 90% was longer in the CNM group (all P < 0.001); 90% recovery took 35.5 (1.18) min for the CNM group and 23.3 (1.68) min for the control group.

CONCLUSION

CNM did not exacerbate the increase in blood potassium that is ordinarily seen with succinylcholine. Recovery from succinylcholine was nearly 50% longer in dogs with CNM. Although our sample size is too small to evaluate the incidence of succinylcholine-induced hyperkalaemia, extrapolation of these findings suggests that increased duration of action should be expected if succinylcholine is given to a patient with autosomal-recessive CNM.

The effect of rocuronium and sugammadex on neuromuscular blockade in a child with congenital myotonic dystrophy type 1

Myotonic dystrophy type 1 (MD1) is the commonest muscular dystrophy found in adults; however, it may present in the neonatal period with hypotonia, talipes, poor feeding, and respiratory failure. Inheritance is autosomal dominant with a defect in the DMPK gene found on the long arm of chromosome 19 with variable expansion of the cytosine-thymine-guanine (CTG) triplet repeat. A 14-month-old boy with congenital MD type 1 was scheduled for percutaneous endoscopic gastrostomy (PEG) insertion, orchidopexy, and division of tongue-tie. Following induction of anesthesia, acceleromyography was used to monitor neuromuscular function. This revealed a very rapid onset of profound neuromuscular block which lasted significantly longer than would be expected in a child without MD1. Sugammadex reversed the block rapidly. The anesthetic management of children with MD1 has been well described but not the acceleromyographic monitored use of rocuronium and its subsequent reversal with the new cyclodextrin sugammadex.

Perioperative management of the paediatric patient with coexisting neuromuscular disease

Children with neuromuscular diseases present a wide range of clinical manifestations and clinical implications for the anaesthesiologist. Neuromuscular diseases in children affect muscle strength by either directly weakening the muscle fibrils or indirectly by a degenerative nerve supply and weak neuromuscular junction. Of the more than 200 neuromuscular disorders known, the vast majority are genetic in origin. This review focuses on four of the more common neuromuscular disorders with emphasis on their pathophysiology and clinical implications for anaesthesiologists: malignant hyperthermia, the muscular dystrophies (Duchenne's, Becker's, and Emery-Dreifuss), mitochondrial disorders, and cerebral palsy.

[Anesthesia with neuromuscular diseases]

Among the neuromuscular diseases (NMDs) over 800 individual entities have been identified. The vast majority of these diseases occur very seldom but all NMDs together add up to a prevalence of 1:1,500. Accordingly the conclusion "seldom diseases are common" seems to be appropriate. The scope of NMDs is very wide varying from the affection of single muscle groups to the complete musculature, from slowly progressive to fulminant progressive forms, from perinatal to the adult manifestation as well as number, course and character of associated comorbidities. Due to the wide heterogeneity concerning NMDs it is of great importance for anesthesiologists to be knowledgeable on relevant comorbidities as well as indications and contraindications for the various anesthetics.

Reversal of rocuronium-induced profound neuromuscular block by sugammadex in Duchenne muscular dystrophy

A case is reported in which a child with Duchenne muscular dystrophy received a dose of sugammadex to reverse a rocuronium-induced profound neuromuscular block. Sugammadex is the first selective relaxant binding agent and reverses rocuronium- and vecuronium-induced neuromuscular block. A fast and efficient recovery from profound neuromuscular block was achieved, and no adverse events or other safety concerns were observed.

[Neuromuscular monitoring in patients with neuromuscular diseases. Options and needs]

The management of general anaesthesia in patients with neuromuscular disorders remains challenging. The underlying causes and clinical presentations of these rare heterogeneous diseases are highly variable and the only common feature is usually skeletal muscle weakness. The appropriate choice and dosage of muscle relaxants are important and an adequate monitoring of the neuromuscular blockade is obligatory. Neuromuscular monitoring can be complicated because of disease-induced alterations in neurophysiology; however, continuous monitoring of the neuromuscular blockade should be realized to accurately determine the recovery from the blockade. These patients very often have an increased risk for postoperative pulmonary complications, which increases further if a residual neuromuscular blockade is present.

Pharmacodynamic modelling of rocuronium in adolescents with Duchenne muscular dystrophy

BACKGROUND AND OBJECTIVE

Studies with rocuronium showed a delayed onset and prolonged recovery in patients with Duchenne muscular dystrophy (DMD). The objective of this study was to identify the pharmacokinetic and/or pharmacodynamic origin of these alterations.

METHODS

Twenty-five male patients (15 with DMD, 10 controls, aged 10-18 years) were studied. Patients were anaesthetized with propofol and sufentanil. Neuromuscular transmission was monitored by acceleromyography. Patients received a single intravenous dose of 0.3 mg kg(-1) rocuronium. In five patients of the DMD group, pharmacokinetic modelling was performed from arterial rocuronium concentrations. The time course of neuromuscular block was analysed with a sigmoid E(max) model including an effect compartment.

RESULTS

The pharmacokinetics of rocuronium in DMD patients were Vc 63 +/- 14 ml kg(-1), Cl 3.0 +/- 1.0 ml min(-1) kg(-1), half-lives 2.0 +/- 0.6, 20 +/- 10 and 129 +/- 98 min, SE. For both the DMD and the control group, the time course of neuromuscular block could be described by a sigmoid E(max) model using the estimated pharmacokinetic parameters of the DMD group. In patients with DMD, the equilibration between the central and effect compartment was significantly slower (T(1/2)ke0: 9.7 +/- 0.3 vs. 1.3 +/- 0.1 min) and the EC(50) was significantly smaller (512 +/- 20 vs. 1170 +/- 64 ng ml(-1)), whereas the ED(50) was 0.16 +/- 0.02 mg kg(-1) in both groups.

CONCLUSION

The pharmacodynamics of rocuronium were significantly altered in patients with DMD, whereas the pharmacokinetics seemed to be similar to those in healthy adults. Patients with DMD were more sensitive with respect to effect site concentration but not with respect to dose.

Neuromuscular and mitochondrial disorders: what is relevant to the anaesthesiologist?

PURPOSE OF REVIEW

The review provides an up-to-date information to the anaesthesiologist about the more frequent and important neuromuscular disorders for which new basic insights or clinical implications have been reported.

RECENT FINDINGS

The findings include the mechanisms of the hyperkalemia after succinylcholine in patients with upregulation of acetylcholine receptors. New insights into the mechanism of malignant hyperthermia-like reactions such as rhabdomyolysis during anaesthesia in patients with Duchenne muscular dystrophy have been published. The importance of mitochondrial defects and the effect of agents used in anaesthesia on mitochondrial function are also highlighted.

SUMMARY

The increased understanding of the genetics and pathophysiology of common muscle disorders may lead to a decrease in life-threatening complications related to surgery and anaesthesia. However, there is still a lack of prospective clinical studies to determine which is the safest anaesthetic technique for these patients.

C Histomorphology of neuromuscular junction in Duchenne muscular dystrophy

BACKGROUND

Our objective was to better understand neuromuscular junction (NMJ) morphology in children with Duchenne muscular dystrophy (DMD).

METHODS

We examined the NMJs of four children, age 6-13 years, who were diagnosed with DMD. Using our previously established staining technique, we examined the gross appearance of the NMJs in patients with DMD and evaluated the spread of acetylcholine receptors (AChRs) in relationship to the NMJs. We used a computerized algorithm to measure the area of staining corresponding to AChRs and NMJ.

RESULTS

Abnormal shape and morphological appearance of some of the NMJs was clearly evident. The spread of AChRs in DMD patients is comparable with the spread of AChRs in nonDMD patients.

CONCLUSIONS

The distribution of AChRs in relationship to the boundaries of NMJs in DMD children is similar to the distribution of NMJs in the erector spinae muscles of idiopathic scoliosis patients.

Reversal of rocuronium-induced neuromuscular blockade by pyridostigmine in patients with Duchenne muscular dystrophy

BACKGROUND

The aim of this study was to investigate the effect and safety of pyridostigmine for the reversal of a neuromuscular block (NMB) in patients with Duchenne muscular dystrophy (DMD). In patients with DMD recovery from a rocuronium-induced NMB is markedly delayed.

METHODS

Fourteen DMD patients (aged between 11 and 19 years) scheduled for elective scoliosis repair were studied. Following tracheal intubation without muscle relaxant, all patients received a single dose of rocuronium 0.6 mg.kg(-1). NMB was monitored by acceleromyography at the adductor pollicis muscle. When the first twitch height (T1) of the train-of-four (TOF) had recovered to 25% seven patients received either pyridostigmine 0.1 mg.kg(-1) (the anticholinergic drug with a long duration of action) or saline in a blinded manner. The times to attain TOF ratio of 0.9 were recorded. For comparison the Mann-Whitney U-test was used.

RESULTS

Recovery to TOF ratio of 0.9 was significantly (P < 0.05) accelerated by pyridostigmine [84 (median), 57-141(range)] compared with controls (148, 84-243 min). The recovery time (time between T1 of 25% and TOF of 90%) was also significantly (P < 0.01) shortened by pyridostigmine (15, 8-49 vs 76, 43-144 min, respectively). Time to recovery of T(1) to 90% was not different between the groups (108, 63-134 vs 169. 61-208 min, respectively).

CONCLUSIONS

Pyridostigmine 0.1 mg.kg(-1) effectively reversed a rocuronium-induced NMB in DMD patients.

Perioperative care of patients with neuromuscular disease and dysfunction

A variety of different pathologies result in disease phenotypes that are summarized as neuromuscular diseases because they share commonalty in their clinical consequences for the patient: a progressive weakening of the skeletal muscles. Distinct caution and appropriate changes to the anesthetic plan are advised when care is provided during the perioperative period. The choice of anesthetic technique, anesthetic drugs, and neuromuscular blockade always depends on the type of neuromuscular disease and the surgical procedure planned. A clear diagnosis of the underlying disease and sufficient knowledge and understanding of the pathophysiology are of paramount importance to the practitioner and guide optimal perioperative management of affected patients.

Rocuronium 0.3 mg x kg-1 (ED95) induces a normal peak effect but an altered time course of neuromuscular block in patients with Duchenne's muscular dystrophy

BACKGROUND

In patients with Duchenne's muscular dystrophy (DMD) recovery from neuromuscular block is delayed. It has been assumed that this is because of a higher potency of muscle relaxants in this patient cohort. We determined the peak effect, and the time course of action of rocuronium 0.3 mg x kg(-1) (ED(95)) in DMD patients.

METHODS

Twenty-four patients (12 with DMD and 12 controls; aged 10-18 years) were studied. All patients were anesthetized with propofol and fentanyl/remifentanil. Neuromuscular transmission was monitored by acceleromyography. After induction all patients received a single dose of rocuronium 0.3 mg x kg(-1). The complete time course of action as onset, peak effect and spontaneous recovery was recorded.

RESULTS

The onset time (s) to maximum block was significantly (P < 0.01) prolonged in DMD patients (median: 315; range: 120-465) compared with controls (195, 75-270). The peak effect (% twitch depression relative to baseline) was not different between the groups (DMD: 59-100; controls: 28-100). In the DMD group, recovery was significantly (P < 0.01) delayed compared with controls at all recorded time points. The clinical duration (min) was 40.3 (22-89) in the DMD group vs 9.8 (6-17) in the control group (P < 0.01).

CONCLUSIONS

The similar peak effect in both groups does not confirm the thesis of rocuronium having a higher potency in DMD patients. The documented very long recovery after the ED(95) of rocuronium emphasizes the need for careful assessment of neuromuscular function in DMD patients.

Onset and duration of mivacurium-induced neuromuscular block in patients with Duchenne muscular dystrophy †

BACKGROUND

To determine the response to mivacurium, we prospectively studied onset time and complete spontaneous recovery from mivacurium-induced neuromuscular block in patients with Duchenne muscular dystrophy (DMD).

METHODS

Twelve boys with DMD, age 5-14 yr, seven of them wheelchair-bound, ASA II-III, and 12 age- and sex-matched controls (ASA I) were enrolled in the study. Anaesthesia was induced with fentanyl 2-3 microg kg(-1) and propofol 3-4 mg kg(-1) titrated to effect, and maintained by continuous i.v. infusion of propofol 8-12 mg kg(-1) and remifentanil as required. The lungs were ventilated with oxygen in air. Neuromuscular transmission was assessed by acceleromyography using train-of-four (TOF) stimulation every 15 s. After baseline readings, a single dose of mivacurium 0.2 mg kg(-1) was given. The following variables were recorded: (i) lag time; (ii) onset time; (iii) peak effect; (iv) recovery of first twitch from the TOF response to 10, 25 and 90% (T(10), T(25), T(90)) relative to baseline; (v) recovery index (time between 25 and 75% recovery of first twitch); and (vi) recovery time (time between 25% recovery of first twitch and recovery of TOF ratio to 90%). For comparison between the groups the Mann-Whitney U-test was applied.

RESULTS

There were no differences between the groups in lag time, onset time and peak effect. However, all recorded recovery indices were significantly (P<0.05) prolonged in the DMD group. The median (range) for time points T(10), T(25) and T(90) in the DMD and control group was 12.0 (8-16) vs 8.4 (5-15) min, 14.1 (9-20) vs 10.5 (7-17) min and 26.9 (15-40) vs 15.9 (12-23) min, respectively. The recovery index and recovery time were similarly prolonged in the DMD group.

CONCLUSIONS

These results support the assumption that mivacurium-induced neuromuscular block is prolonged in patients with DMD.