| Element | Comment |
|---|---|
| Definition | Syndrome resulting from skeletal muscle injury with release of myocyte contents into plasma |
| Causes | |
| Traumatic causes | Crush injury Electrical injury (Chapter 109) |
| Non-traumatic causes | |
| Infection | Bacterial pyomyositis Legionella infection Viral infections Falciparum malaria |
| Electrolyte abnormalities | Hypokalaemia (Chapter 86) Hypocalcaemia (Chapter 87) Hypophosphataemia (Chapter 88) Hyponatraemia (Chapter 85) |
| Immune-mediated | Pyomyositis |
| Drugs | Medications: antipsychotics, statins, SSRI, lithium, colchicines, antihistamines Non-prescription drugs: heroin, cocaine, methadone |
| Metabolic disorders | Myophosphorylase deficiency Phosphofructase deficiency Carnitine palmitoyltransferase deficiency |
| Others | Status epilepticus (Chapter 16) Coma of any cause with muscle compression Hypothermia (Chapter 107) Diabetic ketoacidosis (Chapter 83) Hyperosmolar hyperglycaemic state (Chapter 84) Neuroleptic malignant syndrome (Appendix 69.2) Malignant hyperthermia Prolonged strenuous exercise |
| Investigation and management | |
| Biochemical markers | Raised plasma creatine kinase: levels >50,000units/L are associated with an incidence of acute kidney injury of >50% Myoglobinuria: myoglobin gives positive result on stick test of urine for blood |
| Complications | Hypovolemia due to extravasation of fluid into muscle Acute kidney injury from hypovolemia and renal tubular obstruction, tubular damage and renal vascoconstriction Metabolic effects of muscle injury: hyperkalaemia, hypocalcaemia, hyperphosphataemia, hyperuricaemia |
| Management of severe rhabdomyolysis | Diagnose and treat underlying cause Vigorous fluid resuscitation with crystalloid Transfer the patient to high-dependency unit Put in a bladder catheter to monitor urine output and, in patients over 60 or with cardiac disease, a central venous catheter so that central venous pressure can be monitored to guide fluid replacement and avoid fluid overload Manage acute kidney injury along standard lines |