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
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]