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DescriptionAbnormal systemic release of muscle contents—creatine phosphokinase (CPK), myoglobin, potassium, phosphate, urate—caused by trauma, poisoning, infection, primary muscle disorders, and many other disease states. Complications include:
- Myoglobin-induced renal failure in 15–50% adults, only 5% in children
- Hyperkalemia may lead to sudden death
- Hypocalcemia and acidosis
- Volume loss—fluid sequestration in injured muscle or result of underlying illness
- Compartment syndrome of muscles in crush, worsened by IV fluid sequestration in damaged tissue
- Hepatic dysfunction in 25%
- DIC (Disseminated intravascular coagulation)
- 26,000 per year in US
- Disaster situations lead to 100s of cases of renal failure.
- Inherited myopathy
- Alcohol or drug use
- Medications as listed below
- Overexertion with or without risk factors
- Sarcolemma keeps intracellular calcium low.
- Etiologies disrupt cell membrane and lead to following cascade.
- Breakdown of sarcolemma Na–Ca pumps allows calcium to enter cell.
- Calcium-dependent proteases cause destruction.
- Ischemia and neutrophils cause damage.
- Escape of cell contents: Myoglobin, potassium, phosphate, CPK, lactate, etc.
- Myoglobin causes renal damage by direct toxicity in acidic urine.
- Myoglobin precipitates with other proteins to obstruct renal tubular flow.
- Volume depletion also leads to renal vasoconstriction and failure.
- Hyperkalemia can lead to arrhythmias.
- Calcium precipitates with phosphate, leading to systemic hypocalcemia.
EtiologyCause usually obvious, but not always.
Adults: Trauma, toxicity, infection
Children: Viral myositis, trauma
- Muscle injury—due to trauma/crush, burn, electrical shock—most common cause overall.
- Muscle exertion: Strenuous exercise; marathon running; exercise in hot, humid conditions; exercise in individuals with an inherited myopathy or with poor physical training; status epilepticus; delirium tremens; tetanus; psychotic agitation
- Muscle ischemia: Extensive thrombosis, multiple embolism, generalized shock, sickle cell crisis
- Surgery: Immobilization, hypotension, ischemia due to vessel clamping
- Massive blood transfusion
- Hypothermia, hyperthermia
- Prolonged immobile state without trauma
- Drugs/toxins: Alcohols, cocaine, amphetamines, and analogs (methamphetamine and ecstasy), toluene, opiates, LSD, phencyclidine (PCP), caffeine, carbon monoxide, snake venom, bee/hornet venom, hemlock, buffalo fish, tetanus toxin, mushroom poisoning (Tricholoma equestre)
- Medications: Most common—haloperidol, phenothiazines, HMG–CoA reductase inhibitors (statins) and other cholesterol-lowering agents, antihistamines, selective serotonin receptor inhibitors (SSRIs).
- Sports supplements including ephedra, caffeine, androgenic steroids, creatine, diuretics
- Neuroleptic malignant syndrome (idiosyncratic and not dose-related)
- Metabolic disorders: Hypokalemia, hypophosphatemia, hypocalcemia, hyper- and hyponatremia, diabetic ketoacidosis, hyperosmolar state, hypoxia, hyperthyroid state (rare), pheochromocytoma (rare)
- Viral: Coxsackievirus, herpesviruses, HIV, influenza B, cytomegalovirus, Epstein–Barr virus, adeno/echovirus
- Bacterial: Legionnaires’ disease, pyomyositis, salmonellosis, shigellosis, Staphylococcus, Streptococcus, Listeria, tetanus, toxic shock syndrome, tularemia, gas gangrene, Bacillus cereus
- Parasitic (Plasmodium falciparum), protozoan (leptospirosis), rickettsial
- Inherited myopathic disorders: McArdle disease, Tarui disease, CPT deficiency.
- Immunologic disorders: Dermatomyositis, polymyositis
Commonly Associated Conditions
- Crush syndrome
- Compartment syndrome
- Alcohol and drug abuse
- Elderly and acutely immobile (found on floor)