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Rhabdomyolysis

Suspect rhabdomyolysis in patients with typical history (particularly those found unconscious), symptoms and clinical findings.
When a suspicion arises, the diagnosis is easy to verify (plasma myoglobin; plasma 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.

Rhabdomyolysis refers to an injury of striated muscle when myoglobin molecules can block the renal tubules. It may result in acute renal failure (AKI, acute kidney injury Acute Kidney Injury) unless treatment is instigated early enough.

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.
Contusion injuries, excessive muscle strain (running, body building etc.) or convulsions
Burns
Alcohol and illegal drugs (heroin, cocaine)
Medication (statins)
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)) and hypothermia
Metabolic disorders (hyperosmolar coma Hyperglycaemic Hyperosmolar Syndrome, ketoacidosis Diabetic Ketoacidosis, hypokalaemia Hypokalaemia, hypophosphataemia)
Infections (e.g. influenza, pneumococcus, HIV)
Myopathy (congenital muscle enzyme deficiency Hereditary Myopathies, alcohol)

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.

If rhabdomyolysis is suspected, measure plasma creatine kinase (CK) or plasma myoglobin.
- CK activity is often clearly elevated.
  - The plasma CK cut-off value for severe rhabdomyolysis is usually considered to be 5 000 U/l.
- There is no generally accepted diagnostic cut-off value for plasma myoglobin concentration.
  - Plasma myoglobin > 5 000 µg/l can be considered to be the cut-off value for severe rhabdomyolysis.
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.

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
- The aim is to prevent the development of acute renal failure Acute Kidney Injury, caused by myoglobin which is being released from the muscles.
In a hospital
- Intensive fluid therapy is the cornerstone of the treatment. The target is to maintain diuresis of > 1.5-2 ml/kg/h.
  - In rhabdomyolysis, the fluid deficit can be several litres, so hydration may be abundant in the initial stage, even 1-2 litres per hour.
  - The fluid of choice is a balanced electrolyte solution or NaCl solution or a combination of them.
  - The fluid is selected on the basis of monitoring electrolyte levels (plasma sodium, plasma potassium, plasma chloride) and acid-base balance.
- Dialysis is indicated if the patient is anuric and diuresis is not induced with enhanced 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.

Kidney function is usually reversible even after severe rhabdomyolysis.
- If compartment syndrome is not treated early enough, residual nerve and muscle damage may persist.

Bosch X, Poch E, Grau JM. Rhabdomyolysis and acute kidney injury. N Engl J Med 2009;361(1):62-72. [PubMed]