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In patients with myasthenia gravis should respect certain principles applicable to the anesthesia.
The recommended method for perioperative care for patients with myasthenia gravis.
1. Critical conditions associated with myasthenia gravis (MG):
1.1 Development of cholinergic crisis:
Cholinergic crisis caused by absolute or relative overdose inhibitors cholinesterase (ICHE) used in the treatment of MG: pyridostigmin (Mestinon), distigmin (Ubretid), neostigmine (Syntostigmin). It is characterized by a combination of nicotine symptoms (tremor, fasciculations, twitching, muscle weakness) and autonomous muscarinic symptoms (hypersalivation, bronchial hypersecretion, nausea, vomiting, diarrhea, abdominal pain, bradycardia, miosis). When administered anticholinergics may the autonomous signs mitigované. In that case, you can use in the differential diagnosis effect neostigmine: if after worsening muscle weakness, it is probably cholinergic crisis.
1.2 The development of myasthenic crisis, the need for protracted mechanical ventilation The development of myasthenic crisis may be a natural course of disease psychological or physical stress, infections with hyperpyrexia, or improper administration medication. Among the drugs affecting neuromuscular transmission is used in many preparations in anaesthesiology, intensive care and other related fields. Some can be totally avoided (benzodiazepines) for other general point that the indications must be clearly supported and their use is governed by special arrangements (eg, peripheral nondepolarizing muscle relaxants at a reduced dose of a neuromuscular transmission monitoring, etc.).
The main groups of substances affecting neuromuscular transmission:
1.2.1 Benzodiazepines: if possible, do not serve
1.2.2 Central relaxants (guaiphenesine, baclofen ...) do not serve
1.2.3 Peripheral nondepolarizing muscle relaxants: increased sensitivity and prolonged action is appropriate in patients in remission, the ongoing subclinical MG and with minimum (eye) symptoms. Generally, we choose the preparation of short-lived and fast. Elimination: atracurium, vecuronium, mivacurium. CAVE:patients treated with the ICHE
be affected by degradation mivacuria cholinesterase. Condition of use:
a. Performance nature necessarily requiring muscle relaxation (laparoscopy,
extensive abdominal interventions ...)
b. Reduction of the initial calculated dose to 20-50%
c. Monitoring of neurumucular transmission (NMT). The monitoring neuromuscular method is mostly used electrical neurostimulation pulse monofazic
using skin electrodes stuck over the course of the selected nerve (mostly n. ulnaris). Motor response (in this case an inch of movement) is scanned accelerometry. Evaluated either an irritation, or four successive stimuli (train of four - TOF). On a similar principle works most of the equipment available, either have separate or integrated in monitoring systems anesthesologic devices. Through the use of reduced dose should always be counted prolonged effect, repeated administration with the exception of extremely long output is not appropriate.
1.2.4 Peripheral nonpolarizing relaxants - succinylcholine (SCHJ) is better
tolerated, its effect may be even smaller than in healthy subjects. Nevertheless, the majority recommends reducing the dose. Repeated administration threatened protracted II. phase blockade.
CAVE: patients treated Iche may be affected by degradation SCHJ cholinesterase.
Before submitting SCHJ not to use the "priming" - even a small dose of relaxant might lead to premature palsy, hypoventilation, DC, and occlusion as a result of prolonged action. Indications for use: the impossibility of endotracheal intubation (ETI), even a mere or inhalation anesthesia particularly with the rapid introduction of a full stomach. NMT monitoring is appropriate.
1.2.5 Volatile inhalation anesthetics: they have a direct effect on neuromuscular transmission, increased potency peripheral relaxants, medication in general is chosen primarily to a shorter elimination (desfluran, sevoflurane).
1.2.6 Local anesthetics (LA) LA increased serum levels may affect the neuromuscular transmission, but the general profit local / regional anesthesia that exceeds the risk. Techniques made with fewer ingredients are sometimes preferred (SAB versus epidural block), the introduction of epidural anesthesia catheter, however, allows better titrovatelnost extent of blockade and postoperative analgesia with a reduction of system-made opioids. Better tolerated the amide LA, patients treated with Iche may be affected by degradation ester-like LA. Procaine is absolutely contraindicated.
1.2.7 Dantrolene: indication is malignant hyperthermia, neuroleptic malignant syndrome, hyperpyrexia of intoxication budivými amines
1.2.8 Corticosteroids: initiation of treatment of indications MG (or other) may cause paradoxical transient worsening of weakness. Conversely, when administered chronically in MG as immunosuppression, is extremely dangerous to their withdrawal.
1.2.9 Antibiotics aminoglycoside, macrolide less, glykopeptidová, doxycycline,
erythromycin, ofloxacin, ciprofoxacin, penicillins, sulfonamides.
1.2.10 Calcium channel blockers
1.2.11 Beta blockers
1.2.12 Magnesium especially in higher doses than 1000 mg po, or even brought
1.2.13 Antiepileptics
1.2.14. Anticholinergics
The group 1.2.10 - 1.2. 14 should always consider the individual benefit versus risk
brought drugs. In the case of increased risk should seek other treatment alternatives.
1.3 The central depression of breath
Risk are all centrally deadening agents: benzodiazepines, sedatives, inhalation and iv. anesthetics, opioids. In general, we choose the preparation of low accumulation and short context --
sensitive half-life, especially when repeated or continuous application.
Patients treated Iche could theoretically be affected by the degradation of remifentanil, however, is recommended.
2. Practical procedure
2.1 Preoperative preparation
2.1.1 The scheduled performance must be achieved by optimizing the state at the cost of less common methods (Application intravenous immunoglobulin, plasmapheresis).
2.1.2 In addition to neurological examination should be considered spirometry. Forced Vital capacity and negative inspiratory pressure are the main markers of ventilatory reserve and respiratory function muscles.
2.1.3 The post-operative care must be in advance of their area ventilated bed.
2.1.4 Chronic therapy (Iche, corticosteroids) is given in the morning the day of surgery and continues the performance of enteral or parenteral form.
2.1.5 Due to the increased fatigue should be normal training as intrusive. It is appropriate to include a patient at the beginning of the operational program, as the morning is physical strength is greatest.
2.1.6 For patients treated with corticosteroids should be increased intraoperative dose (hydrocortizon 50-300 mg hr iv/24 by output range). At the same time is
necessary to prevent ofulcer (omeprazole 40-80 mg/24 h).
2.1.7 In patients receiving immunosuppressive consider ATB prophylaxis with regard to the type operations and risks above certain ATB (see 1.2.11).
2.1.8 Checking and correction mineralogramu ev. electrolyte imbalance is necessary (CAVE hypokalaemia, hypocalcaemia, hypermagnezemie).
2.1.9 Premedication: generally use reduced doses due to the risk of central depression. Benzodiazepines are inappropriate, except tofisopam.At night you can use common nonbenzodiazepins hypnotic (zolpidem - Hypnogen) dithiaden, neuroleptic (tiapride) or morning prometazin im premedication, pethidine im, ev. tiapride. Maybe it i.v. sedation titrated dose of opioids and propofol after navezení the operational wing, when it is sick under constant supervision.
2.2 Selection and management of anesthesia
2.2.1 It is best to use the local/regional techniques, ev. supplemented i.v. sedation
(opioid + propofol). Advantages and disadvantages subarachnoidealversus epidural anesthesia and LA different groups mentioned above (1.2.6).
2.2.2. if the nature of performance or other contraindications (allergy to LA, disagreement patient, Hemorrhagic diathesis ....) impossible to use a regional technique, applicable as a second choice of general anesthesia without any nondepolarizing muscle relaxants: a combination of iv + inhalation, where fund assets, especially for short performances. Appropriate medication: propofol, etomidate, remifentanil, alfentanil, sufentanil, O2/N2O, desfluran, sevoflurane (izofluran) Ensuring DC: facial mask / Airway, ev. laryngeal mask is the first choice. If necessary ETI, then if possible, without SCHJ (introduction propofol, opioids, ev. Inhalation - sevoflurane). SCHJ is essential for the rapid introduction and for the impossibility laryngoscopy / intubation and the
deep anesthesia.
Ventilation: deepening, ev. controlled.
Intolerance endotracheal tube or interference with the fan is not a reason to muscle
relax!
2.2.3 If the nature of the power necessary muscle relaxation, reduced benefits apply
nondepolarizing muscle relaxants for the safeguards provided for in section1.2.3. Tothe extent permitted intubation ratios, it is appropriate to intubate without the concurrent use SCHJ. Be envisaged synergy effect of volatile anesthetics can stop the supply of anesthetic elusive ahead and go the end of the performance i.v. propofol sedation until return dostatečná muscle strength. Use lump dekurarization not appropriate given the risk of cholinergic crisis.
2.3 Postoperative care
2.3.1 Even after extubation, patients must be monitored at least observován bed with fan in reserve. Muscle weakness and hypoventilation with airway obstruction
may manifest after several hours, allowing constant monitoring and adequate analgesia without the risk of central apnea.
2.3.2. Analgesia: The best is regional (epidural) administration. The systemic analgesia is be used titrated i.v. steerable continuous administration of opioids (sufentanil, remifentanil) with advantage in combination with paracetamol  or other analgesic  (metamizol, ketoprofen)
2.3.3 In the treatment of gastrointestinal paresis consulted before ev. administration of neostigmine or distigmin attending physician (neurologist) due to the risk of cholinergic crisis. Prokinetics type metoclopramide are tolerated. 

List of abbreviations:
ATB - antibiotics
GIT - gastrointestinal tract
ICHE - cholinesterase inhibitors
LA - Local anesthetics
MG - myasthenia gravis
NMT - neurumuskulární transmission
SAB-subarachnoid block (anesthesia)
SCHJ - succinylcholine 

Josef Zavada MD Jiří Piťha MD
General Teaching Hospital Prague, Czech Republic
 
   

 

Proffesional articles - fulltext:
  

Abel M, Eisenkraft JB. Anesthetic Implications of Myasthenia Gravis 2002.

M. Elarief, E. Ibrahim & P. G. Magadi : Myasthenia Gravis: Towards A Safer Anesthesia Technique. Clinical Experience And Review Of Literature. The Internet Journal of Anesthesiology. 2007 Volume 11 Number 2.