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CRITICAL ILLNESS MYOPATHY INTRODUCTION The most common causes of newly acquired weakness arising in the ICU setting are critical illness myopathy and critical illness polyneuropathy. Critical illness myopathy is probably the major contributor to severe ICU-acquired weakness, causing most instances of failure to wean from a ventilator in patients with severe systemic diseases in the ICU, while critical illness polyneuropathy affects 70% to 80% of patients with severe sepsis and multiorgan failure DEFINITION The hallmark of critical illness myopathy is weakness that is typically diffuse in distribution, affecting both limb and neck muscles. As is typical of most myopathic disorders, weakness tends to have a proximal predominance in the limbs, but it may also involve distal muscles profoundly There may be facial muscle involvement, and rarely, extraocular muscles are affected other muscles supplied by cranial nerves are usually spared. A serious and common complication of the myopathy is failure to wean from a ventilator due to marked weakness of the diaphragm PATHOPHYSIOLOGY Myosin loss and muscle fiber necrosis probably contribute to persisting weakness. Myosin loss is characteristic of CIM and is essentially pathognomonic of the disorder. Corticosteroids may cause the loss of myosin, but other factors trigger the process, such as an abnormal neuromuscular junction caused by pharmacologic blockade who are systemically ill, often with metabolic acidosis, can also develop the myopathy. Acidosis may stimulate glucocorticoid production, lead to an increase in muscle protein degradation, and trigger thick filament loss CLINICAL SIGNS Mixed motor and sensory neuropathy but motor signs tend to predominate. tends to cause proximal muscle weakness predominance, particularly affecting limbs, diffuse, flaccid and usually symmetrical weakness often presents with difficulty in weaning Respiratory difficulties can be caused by atrophy of the intercostals muscles, atrophy of the diaphragm muscle, and degeneration of the nerve that stimulates the diaphragm.This can prolong the time the wean a person of a mechanical ventilation by as much as 7 – 13 days. Deep tendon reflexes may be lost or diminished, and there may be bilateral symmetric flaccid paralysis of the arms and legs possibly due to a generalized reduction in membrane excitability that occurs in sepsis. The nervous system manifestations are typically limited to peripheral nerves. Muscles spared. innervated by cranial nerves are usually RISK FACTORS Severe sepsis and septic shock disturbances of glucose metabolism resulting in hyperglycaemia Adminstration of corticosteroids, vasopressors, catecholamines, Aminoglycosides, Beta agonists use of neuromuscular blocking agents Electrolyte Imbalance : Hyperkalemia, Hypokalemia, Hypermagnesemia trauma, prolonged immobility status epilepticus, toxin and hypothermia and heat stroke. D/D Spinal cord disorders, Gullain-Barre syndrome Chronic inflammatory demyelinating neuropathy, Diabetic polyneuropathy, Myasthenia gravis Lambert-Eaton syndrome. Metabolic Abnormalities Hypothermia DIAGNOSIS Electrophysiological studies (such as needle EMG or nerve conduction studies) and muscle biopsy may both be necessary to diagnose critical illness myopathy. Muscle biopsy Laboratory investigations. i) Electrophysiological studies This studies show reduced amplitude of nerve action potentials but normal conduction velocities in patients with CIM Advantages : can be conducted in unconscious/sedated patients high sensitivity and specificity in mechanically ventilated, sedated patients can differentiates between primary nerve or muscle dysfunction Disadvantages : requires some expertise and certain devices to perform these measurements ii) Muscle biopsy : Features seen on biopsy include fibre atrophy and angulated fibres, fatty degeneration and fibrosis with minimal necrosis Thick filament myopathy Acute necrotizing myopathy Thick filament myopathy characterised by selective loss of myosin filaments plasma creatinine kinase levels are often elevated, and progression to diffuse myonecrosis (rhabdomyolysis) is possible can be produced by surgical denervation of muscle followed by exposure of the muscle to corticosteroids this causes an upregulation in the number of steroid receptors and a resultant steroid hypersensitivity Acute necrotizing myopathy myonecrosis with vacuolisation and phagocytosis of muscle fibres is prominent plasma creatinine kinase levels are frequently raised, and in a minority of patients frank rhabdomyolysis may ensue has also been described in patients admitted to ICU with status asthmaticus that were generally non-septic and received high-dose corticosteroids, either alone or in combination with muscle relaxants this rare type of myopathy has a poor outcome The CPK rise which is found in about 50% of affected patients, only occurs early in the course of the illness, Peaks within a few days of onset, and then declines back into the normal range. CPK will raise 10-100 folds to normal level PREVENTION • • • • Symptomatic treatment of sepsis and controlling the most important risk factor. Corticosteroid and NMBAs (if indicated) should be used at a minimal dose for as short a period as possible The need for neuromuscular blocking agents should be reviewed frequently and overdosing should be avoided by the use of a peripheral nerve stimulator Avoiding hyperglycemia using insulin therapy to maintain strict glycemic control. Lower incidence of CIM was Observed in pts who had treated with IvIg. Patients that are prescribed neuromuscular blocking agents and/or steroids should be monitored for the development of neuropathy and myopathy, including serial serum creatinine kinase measurements and repeated electrophysiological testing. Correct Electrolyte imbalance. Early mobilization can prevent prolonged hospitalization and associated immobilization risks Therapeutic exercises are aimed to improve function and reduce disabilities and complications Percutaneous neuromuscular electrical stimulation A method to induce skeletal muscle growth, to enhance strength and endurance capacity in chronic critically ill patient to prevent loss of muscle mass May be considered to be an alternative treatment to active exercise Has shown to increase muscle strength and reduce the number of hospital stays Long term use have positive effect on tissue healing Medical Research Council Neuromusclar Score (MRC Score) Movement Tested Score For Each Movement Arm Abduction 0 = No Visible Contraction Elbow Flexion 1 = visible contraction but no limb movement Wrist Extension 2 = active movement insufficient to overcome gravity Hip Flexion 3 = active movement against gravity Knee Extension 4 = active movement against gravity and resistance Ankle Dorsiflexion 5 = normal strength • Each Limb is assigned a score from 0 – 15 • Total score range from 0 (tetraplegia) to 60 (normal muscle strength) • ICUAW defined as a score of less than 48 PROGNOSIS Associated with increased mortality, prolonged mechanical ventilation and prolonged rehabilitation majority of survivors have persistent functional disability, decreases in health-related quality of life and restriction of autonomy Due to decreased mobility it increases the risk of pneumonia, deep vein thrombosis, and pulmonary embolism. Modern critical care must therefore no longer solely focus on survival, but particularly consider health-related quality of life after ICU discharge. Thank You.