INDEX

    Rhabdomyolysis – Diagnosis

    Critical Care / Resuscitation, Metabolic / Endocrine, Trauma, Urological

    Last Updated Dec 05, 2021
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    Context

    • Syndrome characterized by muscle necrosis and the release of intracellular muscle constituents into the circulation.
    • Complications can range from subclinical to acutely life threatening.
    • Represents approximately 7 to 10% of all cases of acute kidney injury (AKI).
    • AKI is independently associated with mortality in patients with rhabdomyolysis.
    • The causes of rhabdomyolysis are numerous and therefore should be ruled out in any patient presenting with a traumatic or non-traumatic mechanism for muscle injury.
    • Look for underlying causes: MI, shock, dead gut, dead limbs, occult seizures can all cause elevated CK.

    Complications

    • Acute renal failure (may be up to 33% of patients presenting with rhabdomyolysis).
    • Hypovolemia from “third-spacing”.
    • Hyperkalemia, hyperphosphatemia, hypocalcemia and hyperuricemia.
    • Metabolic acidosis.
    • Compartment syndrome.
    • Disseminated intravascular coagulation.

    Diagnostic Process

    Diagnosis

    • Elevated serum CK levels.
    • May have signs, symptoms, or a mechanism consistent with muscle injury.
    • Consistent signs and symptoms are non-specific and not always present. The diagnosis, therefore, requires a high level of suspicion from the treating physician in the setting of elevated CK levels.

    Causes

    • Trauma (crush injuries, burns, electrocution).
    • Exertion (strenuous exercise, seizures, alcohol withdrawal).
    • Muscle hypoxia (limb compression, compartment syndrome, prolonged immobilization – coma or extended time on the ground).
    • Genetic defects (disorders of glycolysis, glycogenolysis, lipid metabolism)
    • Infections: viral (severe influenza), clostridium.
    • Body temperature changes (hyperthermia, heat stroke, hypothermia)
    • Metabolic and electrolyte disorders: thyroid storm, phaeochromocytoma, DKA, hypokalemia, hypophosphatemia
    • Drugs and toxins:
      • Lipid lowering drugs,
      • Sedatives: heroin, alcohol (causing coma).
      • Stimulants: cocaine, amphetamines, malignant hyperthermia, serotonin syndrome, neuroleptic malignant syndrome.

    Presentation

    • Classic triad: myalgia, weakness and dark tea coloured urine (myoglobinuria).
    • Muscle pain, when present is typically most prominent in proximal muscle groups (affected limb).
    • Depending on the underlying etiology, patients may also present with malaise, nausea, vomiting and abdominal pain.

    Physical

    • Muscle tenderness.
    • Muscle swelling.
    • Muscle weakness.
    • Depending on the underlying etiology, may see skin changes of ischemic tissue such as discoloration or blisters.
    • If severe, shock due to third spacing, acidosis.

    Investigations

    • Serum CK > 5 times upper limit of normal at presentation:
      • No cut-off value that conclusively diagnoses rhabdomyolysis.
      • CK > 5,000 significant (some report to be 50%) risk of AKI.
      • Begins to rise 2 – 12 hours following muscle injury, reaches maximum within 24 hours.
    • Blood urea nitrogen, creatinine, and routine electrolytes:
      • This is the focus rather than the CK level.
      • Acute kidney injury and severe electrolyte abnormalities are common.
    • Urinalysis:
      • Myoglobinuria will have positive blood test on urine dipstick.
      • Red/brown urine; POS dipstick result for blood, few RBC on R&M highly suggestive but, if indicated, may require further lab tests), proteinuria.
      • Lab will evaluate the colour of the supernatant after centrifugation of the urine; hematuria will have a clear supernatant, whereas hemoglobinuria and myoglobinuria will not. To differentiate hemoglobinuria from myoglobinuria, evaluate the plasma colour; hemoglobinuria will have a pink to red plasma colour, whereas myoglobinuria will not.
    • Complete blood count, including differential and platelet count.
    • Calcium (can be low or high), phosphate, albumin, and uric acid (high):
      • Often abnormal.
    • Venous blood gas (metabolic acidosis).
    • Electrocardiography (hypocalcemia, hyperkalemia).
    • Other investigations should be guided by your decision for the underlying etiology.

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