Anaesthetic Considerations in Neuromuscular Disorders

Dr. Hemant OjhaIntern, Department of AnaesthesiaKMCTH

OverviewA. Neuromuscular Disorders – An

IntroductionB. Classification of Neuromuscular

DisordersC. General Considerations D. Specific ConsiderationsE. SummaryF. References

A. Neuromuscular Disorders – An IntroductionFirst described in 1836 by Conte in

Naples, Italy.Heterogenous group affecting skeletal

muscles.Abnormalities may be in motor nerves,

neuromuscular junction, cellular matrix, ion channels or metabolic.

Number of anaesthetic implications

B. Classification

C. General Considerations1. Pre - operative Management

Precise diagnosis.Full discussion regarding potential risks

and complications.Thorough pre-assessment of function and

associated conditions.Anaesthetic strategies and preparation.Planning of postoperative care.

C. General Considerations2. Peri - operative Management

MonitoringThermoregulationRegional AnaesthesiaGeneral AnaesthesiaNeuromuscular Blocking Agents

2. Peri – operative Managementa. Monitoring• EEG• Oxygen saturation• Capnography• Blood Pressure

C. General Considerations

2. Peri – operative Managementb. Thermoregulation• Risk of both hypo- and hyperthermia.

C. General Considerations

2. Peri – operative Managementc. Regional Anaesthesia• Better in presence of significant

cardiovascular or respiratory involvement• Should be avoided in rapidly progressive

neurological deterioration.

C. General Considerations

2. Peri – operative Management d. General Anaesthesia• Volatile agents – usually not favoured.• Some disorders associated with malignant

hyperthermia, e.g. DMD.• IV agents preferrable.

C. General Considerations

2. Peri – operative Managemente. Neuromuscular Blocking Agents• Depolarising agents – usually not

recommended.• Non depolarising agents – may be used

but should be avoided if possible.• IV agents – preferrable.• Anticholineesterases – not recommeded in

muscular dystrophies.

C. General Considerations

C. General Considerations3. Post - operative Management

Intensive CarePhysiotherapyAppropriate analgesia

d. Specific ManagementCharcot-Marie-Tooth Disease

Chronic peripheral neuromuscular denervation.Depolarizing NMB agents should be avoided.Action of non-depolarizing NMB agents may be

prolonged. I.V. or volatile agents must be used.Respiratory compromise may lead to

ventilation postoperatively. Neurological deficits should be noted before

regional anaesthesia.

Fredrich’s AtaxiaThe diaphragm often impaired - can result in

respiratory failure. Depolarizing NMB agents should be avoided

due to denervation.Risk of aspiration d/t UMN involvement. Care must be taken with negatively inotropic

drugs due to the involvement of the myocardium.

d. Specific Management

Deuchenne’s Muscle Dystrophy X-linked recessive disorder. Respiratory insufficiency and cardiac dysfunction related to

cardiomyopathies or arrhythmias. Blood loss may be increased due to smooth muscle and platelet

dysfunction. Hypotensive anaesthesia. Female carriers - elevated CK levels, mild myopathic changes, &

cardiomyopathy. Volatile anaesthesia and depolarizing NMB agents are avoided. Depolarizing NMB agents must be avoided in DMD & BMD. Catastrophic hyperkalaemia - depolarization of synapses, as well as

from rhabdomyolysis d/t damage caused to the muscle cell membrane.2 Non-depolarizing NMB agents – must be used sparingly - leading to a

prolonged block.

d. Specific Management

d. Specific ManagementDeuchenne’s Muscle Dysrophy

Appropriate i.v. anaesthesia technique. Inhalation anaesthetics - extreme caution,

with total i.v.Clean anaesthetic machine.

d. Specific ManagementHyperkalaemic periodic paralysis

Preoperative potassium depletion.Use of loop diuretics.ECG monitoring should be continuous, and

calcium should be available for the emergency treatment of hyperkalaemic-induced weakness.

Fasting should be minimized.Hypothermia should be avoided. Volatile agents and non-depolarizing NMB

agents is thought to be safe.

d. Specific ManagementHypokalemic Periodic Paralysis

Depolarizing NMB agents should not be given. Non-depolarizing NMB agents used should have

a short duration.Perioperative management –

Avoiding drugs that cause serum potassium shifts. Maintaining normothermia Ensuring serum potassium is kept within the normal

range.

d. Specific ManagementMetabolic Myopathies

Aggressive metabolic monitoring - perioperative phase.

Adequate hydration with forced diuresis to avoid myoglobinuria.

Glucose and amino acid infusions to aid muscle metabolism.

Hypothermia should be prevented to avoid shivering and increased muscle activity.

d. Specific ManagementMitochondrial Myopathies

These patients are difficult to anaesthetize, as most anaesthetic drugs have a depressant effect on mitochondria.

Total atrio-ventricular block can occur.Stringent glucose control, avoidance of stress,

prolonged fasting.Respiratory failure can occur postoperatively. Impaired swallowing leading to aspiration.Low dose volatile inhalation anaesthetic and

ketamine recommended.

d. Specific ManagementMotor Neuron Disease

Depolarizing neuromuscular blocking agents should be avoided.

Non-depolarizing neuromuscular blocking agents may be used in reduced doses due to increased sensitivity.

Respiratory complications – common.

d. Specific ManagementGuillain–Barre´ syndrome

Rapidly progressing respiratory muscle weakness may result in intubation and ventilation.

Invasive monitoring due to the risk of autonomic instability.

The use of depolarizing neuromuscular blocking agents should be avoided.

Increased sensitivity to non-depolarizing neuromuscular blocking agents.

Epidural anaesthesia may be useful to avoid postoperative opioid use.

d. Specific ManagementMultiple Sclerosis

Local anaesthetics may exacerbate symptoms due to the increased sensitivity of demyelinated axons to local anaesthetic toxicity.

Non-depolarizing neuromuscular blocking agents may be used in normal doses.

Depolarizing neuromuscular blocking agents must be used carefully if the patient is debilitated.

Temperature maintenance is important demyelinated axons are more sensitive to heat.

d. Specific ManagementDiabetic Neuropathy

Autonomic instability may occur - invasive monitoring should be considered.

Gastropareisis is a feature and care should be taken at induction and in the postoperative period.

Increased likelihood of becoming hypothermic -temperature control is imperative.

d. Specific ManagementMyasthenia Gravis

Relative resistance to depolarizing neuromuscular blocking agents - dose used may need to be increased.

Sensitivity to non-depolarizing neuromuscular blocking agents, requiring only 10% of normal dose.

Cholinesterase inhibitors should be avoided - precipitate a cholinergic crisis.

Drugs that interfere with neuromuscular transmission should be avoided.

Postoperative ventilation may be necessary.

d. Specific ManagementEaton Lambert Syndrome

Sensitivity to depolarizing and non-depolarizing neuromuscular blocking agents.

Anti-cholinesterases can be given. Potential for autonomic dysfunction to the

relative lack of Ach. There may be a need to ventilate

postoperatively.

d. Specific ManagementCritical Illness Myopathy

Prevention in intensive care patients. Prolonged infusions of non-depolarizing

neuromuscular blocking agents should be avoided especially when high dose steroids are used.

Due to the denervation involved, depolarizing neuromuscular blocking agents should be avoided to prevent hyperkalaemic cardiac arrest.

e. SummaryNeuromuscular disorders are a heterogenous

group of diseases.Thorough preoperative assessment and

perioperative planning is vital.Depolarizing neuromuscular blocking agents

may result in life-threatening hyperkalaemia.Complications can include rhabdomyolysis,

autonomic dysfunction, and myotonias.Significant cardiac and respiratory

involvement common.Knowledge of individual disease process is

vital for optimum management.

f. ReferencesMarsh S, Pittard A. Neuromuscular disorders and

anaesthesia. Part I: generic anaesthetic management. Continuing Education in Anaesthesia, Critical Care & Pain. 2011 Jun 10;11(4):119-123.

Marsh S, Pittard A. Neuromuscular disorders and anaesthesia. Part II: specific neuromuscular disorders. Continuing Education in Anaesthesia, Critical Care & Pain. 2011 Jun 10; 11(4):119-123.

Ghazi H, Hirsch N. Neuromuscular disorders: relevance to anaesthesia and intensive care. Anaethesia & Intensive Care Medicine. 2008 Jun;9(6):137-139.

Morgan GE, Mikhail, MS, Murray MJ, editors. Clinical Anesthesiology. 4th ed. New York: Tata McGraw Hill; 2009.

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