Rhabdomyolysis

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Background

  • Muscle necrosis and release of intracellular muscle constituents into the circulation
  • Recurrent episodes suggests inherited metabolic disorder
  • Alcohol and drugs play a role in up to 80% of cases

Etiology

  1. Trauma or muscle compression
  2. Nontraumatic Exertional
  3. Nontraumatic Nonexertional
    • Drugs and toxins
      • Coma induced by sedatives
      • Alcohol
        • Coma-induced muscle compression
        • Direct toxic effect
        • Nutritional compromise increases risk (hypoK, hypoMg, HypoPhos)
      • Statins
      • Colchicine
      • CO Poisoning
    • Infection
      • Viral myositis - Influenza, Coxsackie, EBV, HSV, HIV, CMV
      • Bacterial pyomyositis
      • Septicemia
    • Endocrine
    • Inflammatory myopathies
      • Moderate CK elevations only (rhabdomyolysis only described in case reports)
    • Miscellaneous

Clinical Features

  • Myalgia, stiffness, weakness, malaise, low-grade fever, dark urine
    • Musculoskeletal symptoms may be present in only half of cases
  • Nausea and vomiting, abdominal pain, tachycardia in severe cases
  • Mental status changes secondary to urea-induced encephalopathy

Differential Diagnosis

Extremity trauma

Red Urine

  • Hematuria
  • Hemoglobinuria
  • Porphyria
  • Myoglobinuria (rhabdomyolysis)
  • Foods
    • Blackberries
    • Beets
    • Blackberries
    • Rhubarb
    • Food coloring
    • Fava beans
  • Drugs
    • Laxatives
    • Phenophthalein
    • Rifampin
    • Doxorubicin
    • Deferoxamine
    • Ibuprofen
    • Chloroquine
    • Hydroxocobalamin

Evaluation

Work-up

  • Obtain immediate ECG (electrolyte abnormalities)
  • Total CK
  • Urinalysis
  • CBC
  • Chemistry, including Mag, Phos
  • Uric acid
  • LFTs
  • DIC panel
    • Coags, FSP, fibrinogen

Evaluation

  • Total CK
    • Most consider rhabdomyolysis if 5x or greater increase above upper limit of normal (~2000)
    • Serum CK begins to rise 2-12hr after injury, peaks within 24-72hr
    • Degree of CK elevation correlates with muscle injury, but NOT renal failure
  • CK-MB
    • May be normal or mildly elevated (<5% of total)
  • Uric Acid - elevates before CK
  • Myoglobinuria
    • Urinalysis = +blood, no RBCs (Sn ~80%)
    • Myoglobin is cleared within 1-6hr (often see elevated CK with no myoglobinuria)
  • Acute renal failure
    • Creatinine increase
  • Electrolyte abnormalities

Management

Trend:

  • Volume status
  • Urine pH
  • Chemistry
  • CK
  • Calcium, phosphorus

IV Fluids

  • Start with NS 1-2 L/hr
  • Once urination occurs maintain urine output of 200-300 mL/hr (3 cc/kg/hr)
  • Frequently need ~10 L/day

Urinary alkalinization

  • Admistered as bicarbonate drip
    • Mix 150 mL [3 amps] of 8.4% sodium bicarbonate with 1 L D5W
    • Infuse at 200 mL/hour; rate is adjusted to achieve urine pH of >6.5
  • Controversial; no RCT to date have demonstrated benefit
  • Consider if CK >5000, severe muscle injury (crush injury), rising CK AND urine pH <6.5
  • Contraindications:
    • Severe hypocalcemia
    • Arterial pH > 7.50
    • Serum bicarbonate > 30 meq/L
    • Arterial pH and serum calcium should be monitored q2hr
  • Discontinue alkalinization:
    • Urine pH does not rise above 6.5 after 3-4hr
    • Patient develops symptomatic hypocalcemia
    • Arterial pH > 7.5
    • Serum bicarbonate >30 meq/L

Mannitol

  • Mannitol administration can worsen dehydration and oliguria and although used in the past should generally be avoided
  • No RCT to date has demonstrated benefit

Intubation/RSI

  • Use Rocuronium due to the potential elevations in potassium that result from the rhabdomyolysis

Disposition

  • Discharge if:
    • Exertional rhabdo
    • Otherwise healthy
    • No comorbidities (heat stress, dehydration, trauma)
    • Downtrending total CK
      • Consider admission for CK >30,000
  • Otherwise admit to monitored bed

Complications

  • Acute Renal Failure
    • Neither presence of myoglobinuria nor degree of CK rise is predictive of ARF
    • Rare in exertional rhabdomyolysis with out presence of dehydration, heat stress, trauma
    • Most commonly oliguric
  • Hyperkalemia
    • Renal function, not release of K+, is most important determinant
    • Treat aggressively; insulin may be ineffective; may require dialysis
  • Hypocalcemia (initial phase)
    • Treat only if symptomatic or severely hyperkalemic (often have rebound hypercalcemia)
  • Hypercalcemia (recovery phase)
  • Hyperphosphatemia
    • Treat cautiously (treatment may worsen calcium precipitation in muscle)
    • Consider oral phosphate binders when level >7
  • DIC
    • Usually resolves spontaneously within several days
  • Compartment Syndrome
  • Peripheral nerve injury
    • Usually resolves within few days-weeks

See Also

References

  1. O'Connor AD et al. Prevalence of Rhabdomyolysis in Sympathomimetic Toxicity: A Comparison of Stimulants. J Med. Toxicol. 2015;11(2)195-200