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Rhabdomyolysis
Essentials
- Suspect rhabdomyolysis in patients with typical history (particularly those found unconscious), symptoms and clinical findings.
- When suspicion arises diagnosis is easy to verify (serum creatine kinase, CK).
- Intensified fluid therapy is the most essential treatment measure: start with infusing 1 000 ml of 0.9% saline solution during the first hour.
Definition
- Rhabdomyolysis refers to an injury of striated muscle. It may result in acute renal failure unless treatment is instigated early enough.
Aetiology
- The most common causative factor is lying unconscious on a hard surface either as a result of intoxication (alcohol or medication), or due to an illness. The long lasting pressure will cause muscle damage.
- Crush injury, excessive muscle strain (running, body building etc.) or convulsions
- Alcohol and illegal drugs (heroin, cocaine)
- Medication (statins very rarely)
- Hyperthermia Acute Heat Illnesses (malignant hyperthermiahttp://www.orpha.net/consor/cgi-bin/Disease_Search.php?lng=EN&data_id=649&Disease_Disease_Search_diseaseGroup=hyperthermia&Disease_Disease_Search_diseaseType=Pat&Disease(s) concerned=Malignant-hyperthermia&title=Malignant-hyperthermia&, neuroleptic malignant syndrome Neuroleptic Malignant Syndrome (Nms))
- Metabolic disorders (hyperosmolar coma Hyperglycaemic Hyperosmolar Syndrome, ketoacidosis Diabetic Ketoacidosis, hypokalaemia Hypokalaemia, hypophosphataemia)
- Infections (pneumococcus, salmonella, legionella, influenza, cytomegalovirus)
- Myopathy (congenital muscle enzyme deficiency Hereditary Myopathies, alcohol)
Signs and symptoms
- The affected area (limbs, buttocks, back) is painful, swollen or tender to touch.
- The patient may be unconscious, confused, dehydrated or febrile.
- Paresis or sensory disturbance may be present in the limbs (increased compartment pressure).
- Urine may be dark (myoglobin), orurine output may be decreased.
- Urine strip test may be positive to haematuria (due to myoglobin), even when no red cells are seen in the sediment.
Diagnosis
- If rhabdomyolysis is suspected, measure serum creatine kinase (CK).
- CK activity is often clearly elevated (10 000-100 000 U/l).
- In clinical practice, the measurement of other muscle enzymes is not needed.
- Plasma myoglobin concentration is also increased.
- Other typical laboratory findings include
- hypocalcaemia (calcium deposited in muscle tissue)
- hyperkalaemia
- hyperphosphataemia (renal failure and release from cells)
- urine dipstick test positive (+) for erythrocytes in approximately 50% of patients
- increased serum creatinine as renal failure develops.
- Differential diagnosis: Local symptoms may resemble those of deep venous thrombosis.
- Palpate the muscles, note tenderness and swelling.
Treatment
- The patient is usually admitted to hospital.
- In primary care the first aid consists of the correction of hypovolaemia and dehydration.
- Start with physiological saline.
- 1 000 ml during the first hour
- Followed by 400 ml/h
- The aim is to prevent the development of acute renal failure Acute Kidney Injury, caused by myoglobin which is being released from the muscles.
- Follow-up treatment in a hospital
- Intensive fluid therapy is the cornerstone of the treatment. The target is to maintain diuresis of 200-300 ml/h.
- Initially 1 000 ml of 0.9% NaCl over 1 hour
- Fluid therapy may also be continued with a solution containing 0.3% NaCl and 5% glucose, at rate 400 ml/h.
- Alkalization of the urine may be considered if the urine pH is less than 6.5 (even if there is no evidence to support this therapy): administer by turns 1 000 ml of plain 0.9% NaCl and 1 000 ml of 0.45% NaCl with an addition of 50-75 ml of 7.5% bicarbonate.
- Dialysis is indicated if the patient is anuric and diuresis is not induced with rehydration.
- Dialysis will have no effect on the renal state, but will keep the patient alive until renal function spontaneously returns. This may take several days, even weeks.
- Fasciotomy is indicated if increased compartment pressure threatens to cause muscle necrosis or nerve damage Muscle Compartment Syndromes; readily consult a surgeon.
- Correction of symptomatic hypocalcaemia must be carried out cautiously, because hypercalcaemia often develops during recovery. Asymptomatic hypocalcaemia requires no treatment.
Prognosis
- Prognosis is good even in cases where renal failure has developed, since the failure is reversible.
- If compartment syndrome is not treated early enough, residual nerve and muscle damage may persist.
References
- Bosch X, Poch E, Grau JM. Rhabdomyolysis and acute kidney injury. N Engl J Med 2009;361(1):62-72. [PubMed]