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Anaesthesia for Thymectomy in Adult and Juvenile Myasthenic Patients

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Anaesthesia for Thymectomy in Adult and Juvenile Myasthenic Patients REVIEW CURRENT OPINION Anaesthesia for thymectomy in adult and juvenile myasthenic patients Zerrin Sungur and Mert Sentu¨rk Purpose of review Myasthenia gravis, a chronic disease of the neuromuscular junction, is associated with an interaction with neuromuscular blocking agents (NMBAs). As thymectomy is often the method of choice for its treatment, anaesthetic management requires meticulous preoperative evaluation, careful monitoring, and adequate dose titration. The frequency of video-assisted thoracoscopic extended thymectomy (VATET) is also increasing, making the use of NMBA obligatory. The number of cases of the juvenile form has also increased over years; airway management in juvenile one-lung ventilation is another challenge. Recent findings Sugammadex appears to be a safe choice to avoid prolonged action of NMBA also in patients with myasthenia gravis, although this information has to be confirmed in further series. The number of VATETs is increasing so that the experience with sugammadex will also increase in time. In non-VATET operations, use of NMBA should and can be avoided as much as possible. New scoring systems are defined to predict a postoperative myasthenic crisis. For VATET in juvenile cases, blockers can be a good option for the airway management. Summary Anaesthetic management of thymectomy in myasthenia gravis requires experience concerning different approaches. Sugammadex should be considered as a possible further step toward postoperative safety. Keywords muscle relaxants, myasthenia gravis, one-lung ventilation INTRODUCTION currently accepted for patients between 0–19 years The last review about myasthenia gravis in Current of age [2]. Neonatal myasthenia gravis, which is Opinion in Anaesthesiology was in 2001 [1]. Since caused by passive transfer of maternal acetylcholine then, a lot of things have changed in this topic: receptor (AChR) antibodies, cannot be included in there is new information concerning it’s pathology, JMG. Muscle weakness is relieved in 2–4 weeks, and which has also changed and improved the thera- therapy remains mostly symptomatic. peutic approach. Regarding surgical treatment, not Prevalence and incidence of myasthenia gravis only the experience has improved, there are also appears to be increased, probably caused by better new procedures which are associated with better diagnosis and better treatment [3]. The pooled inci- outcome. Not at least, regarding the anaesthesio- dence rate is reported to be about 5.3 per million logical approach, there are new solutions for classi- person-years and the estimated pooled prevalence cal problems. But overall, the multidisciplinary rate about 77.7 per million. For JMG, the incidence challenge of myasthenia gravis remains. This review in Europe is about 0.1–0.5/100.000 per year [4–5]. will focus more on the anaesthesiological chal- lenges, which include not only the intraoperative Department of Anaesthesiology, Istanbul Medical Faculty, Istanbul strategies, but also the perioperative management. University, Istanbul, Turkey Myasthenia gravis is a well known neuromus- Correspondence to Mert Sentu¨rk, Istanbul Tıp Fak, Anesteziyoloji AD, cular junction disease, described first at the end of Istanbul University, 34039 Capa-Istanbul, Turkey. Tel: +0090 212 the 19th century. The paediatric or juvenile form 6318767; fax: +0090 212 5332083; e-mail: [email protected] of the disease was defined later in the middle of Curr Opin Anesthesiol 2016, 29:14–19 the 20th century. The term ‘juvenile MG’ (JMG) is DOI:10.1097/ACO.0000000000000272 www.co-anesthesiology.com Volume 29 Number 1 February 2016 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Anaesthesia for thymectomy Sungur and Sentu¨rk CLINICAL COURSE KEY POINTS Main feature of the disorder is muscle weakness, Anaesthesiologists should have a key place regarding which improves at rest and which worsens with decisions concerning timing, strategy of operation and activity [8]. More than half of patients have ocular postoperative course in myasthenia gravis and signs like diplopia or ptosis. Extremity muscles are JMG patients. also affected and result in fatigue more prominent at Use or avoidance of neuromuscular blocking agents is the end of the day. Proximal muscle groups are more still a question, but they appear to be absolutely frequently impaired. Dysphagia or dysarthria are indicated in video-assisted thoracoscopic extended present with bulbar impairment and indicate a more thymectomies [because of one-lung ventilation]. severe level of disease. Aspiration or malnutrition Sugammadex is a new reversal drug, and can be a should be investigated in serious myasthenia gravis. reliable choice in this patient group. In 1950s, Osserman suggested a clinical classifi- cation to evaluate the severity of the disease. This Postoperative care is of high importance, yet not was modified by the Myasthenia Gravis Foundation necessarily in the ICU, but complete recovery of of America in the 2000s (Table 1). respiratory functions should be assured. As an autoimmune disease myasthenia gravis can coexist with disorders, which possess dysimmune properties, among them endocrinopathies (thyroid Myasthenia gravis is caused by pathogenic auto- disorders), rheumatoid arthritis, ulcerative colitis, antibodies to components of the postsynaptic and sarcoidosis are mostly encountered [9]. Hypo- muscle endplate. A subgrouping based on the differ- && thyroidism and malnutrition deserve special interest ent antibodies has been defined recently [6 ]. This for perioperative recovery, as they have to be treated classification also affects the clinical approach, prior to surgery. including surgery. Briefly, there are autoantibodies Some conditions may exacerbate the course of against the AChR, muscle-specific kinase, and lip- disease and may even cause need for mechanical oprotein-related protein 4. Myasthenia gravis with ventilation. Infections, thyroid disorders, radiation, AChR antibodies are further divided to ‘early’ and extreme temperature are frequent pathological and ‘late-onset’ myasthenia gravis. Moreover, ‘thy- risk factors; however sleep disorders, pain, or menses moma-associated’, ‘antibody-negative generalized’, may also worsen patient’s status [6&&,9]. Drugs and ‘ocular’ types are also differentiated. Among should be cautiously used in myasthenic patients them, ‘early-onset myasthenia gravis with AChR as a large variety of drugs [antibiotic (e.g. amino- antibodies’ and ‘thymoma-associated myasthenia glycosides), antiarrhythmic (e.g. verapamil), neuro- gravis’ can profit from surgical treatment. Generally, psychiatric] may aggravate the disease. Although there is a close relationship between the indication corticosteroids are a part of the therapy, they may for surgery and cellular abnormalities of thymic cause an early exacerbation of myasthenia gravis. If gland (hyperplasia or thymoma). JMG is often sero- positive with anti-AChR [6&&]. DIAGNOSIS Table 1. Myasthenia Gravis Foundation of America clinical classification of myasthenia gravis; a modification Diagnosis is initiated with clinical suspicion of of Osserman score system fluctuating muscle weakness. Definite diagnosis consists of the edrophonium test, electromyography Stage Clinical status and detection of antibodies. I Only ocular involvement Edrophonium is a short acting anti-acetyl- II Generalized mild muscle weakness choline esterase (AChE) drug. The test is positive if patient’s muscle weakness is ameliorated 45 s IIa Predominantly affects limb and axial muscles after drug administration and this improvement IIb Predominantly bulbar involvement or respiratory weakness continues for approximately 5 min. A decremental III Generalized moderate muscle weakness response of affected muscles for repetitive action IIIa Predominantly affects limb and axial muscles potentials is a characteristic finding of myasthenia IIIb Predominantly bulbar involvement or respiratory weakness gravis in electromyography studies. These findings IV Generalized severe muscle weakness may also be seen in similar disorders, such as Lam- IVa Predominantly affects limb and axial muscles bert–Eaton syndrome, certain myotonies, or motor IVb Predominantly bulbar involvement or respiratory weakness neuron diseases. The presence of anti-AChR anti- V Tracheal intubation or mechanical ventilation bodies is pathognomic for myasthenia gravis [7]. 0952-7907 Copyright ß 2016 Wolters Kluwer Health, Inc. All rights reserved. www.co-anesthesiology.com 15 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. Thoracic anesthesia surgery should be performed at the initial phase of cyclophosphamide, cyclosporine A, and rituximab steroid therapy, the anaesthetist must be aware of [6&&]. this worsening effect [10]. The myasthenic crisis is an emergency case and Apart from drugs, electrolyte imbalance may be has to be treated under ‘intensive care’ conditions associated with increased muscle weakness. Hyper- with respiratory support, treatment of infections, magnesaemia is the most prominent as magnesium and monitoring of vital functions and mobilization. acts as an antagonist to calcium during neuromus- Intravenous immunoglobulin and plasma exchange cular transmission. Hypermagnesaemia is mostly are options for further treatment, both can be given iatrogenic as in preeclampsia/eclampsia therapy. in sequence if necessary, as patients can respond to Serum magnesium levels are not always consistent one but not to the other [14]. with clinical course, so weakness
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