Rhabdomyolysis

Epidemiology

  • xxx

Etiology

Infection

Toxin

  • Barium Ingestion (see xxxx, [[Barium]]): accidental or intentional ingestion
  • Widow Spider Bite (see Widow Spider Bite, [[Widow Spider Bite]])

Muscle Trauma

  • Crush Injury
  • Prolonged Pressure: typically in patient who has been unconscious

Physiology

  • xxx

Clinical Manifestations

Renal Manifestations

Acute Kidney Injury (AKI) (see Acute Kidney Injury, [[Acute Kidney Injury]])

  • Epidemiology
    • Rhabdomyolysis accounts for 28% of trauma-associated AKI requiring HD
    • AKI develops in 30-40% of rhabdomyolysis cases
  • Mechanisms of AKI
    • Decreased Glomerular Perfusion
    • Nephrotoxic Effects of Ferrihemate
      • Ferrihemate and globin are breakdown products of myoglobin (occurs when pH is <5.6)
      • Ferrihemate contains iron, which accepts and donates electrons -> generation of free radicals, which cause direct renal cell injury
    • Effects of Heme-Proteins On Nitrous Oxide (NO), Endothelin Receptors, and Various Cytokines
    • Precipitation of Myoglobin and Uric Acid Crystals within Renal Tubules
  • Risk Factors for AKI [MEDLINE]
    • Peak CK >6000 IU/L: AKI may occasionally occur in severely dehydrated patients with peak CK levels as low as 2000 IU/L
    • Dehydration (hematocrit >50, serum sodium level >150 mEq/L, orthostasis, pulmonary wedge pressure < 5 mm Hg, urinary fractional excretion of sodium < 1%)
    • Hyperkalemia/Hyperphosphatemia: present on admission
    • Hypoalbuminemia
    • Sepsis

Electrolyte Abnormlaities

  • Hyperkalemia (see Hyperkalemia, [[Hyperkalemia]])
  • Hyperphosphatemia (see Hyperphosphatemia, [[Hyperphosphatemia]])
  • Hypocalcemia or Hypercalcemia (see Hypocalcemia, [[Hypocalcemia]] and Hypercalcemia, [[Hypercalcemia]])
    • Patients are typically hypocalcemic during the oliguric phase of AKI (ATN): probably due to calcium deposition in the injured muscle tissues
    • Approximately 30% of patients are hypercalcemic during the recovery/diuretic phase of AKI (ATN): due to increased 1,25-Dihydroxyvitamin D3, which occurs during this phase

Abnormal Findings on Urinalysis

  • Large Blood Detected on Urinary Dipstick with Minimal RBC’s on Microscopy: as urinary dipstick detects myoglobin
  • Coca Cola-Colored Urine (see Urine Discoloration, [[Urine Discoloration]])

Orthopedic Manifestations

  • Elevated CK: may be in the hundreds of thousands

Other Manifestations

  • Sites of Muscle Injury: may be notable on exam

Treatment

Management of Electrolyte/Metabolic Abnormalities

  • Hyperkalemia: standard treatment
  • Hypocalcemia (During Early Oliguric Phase of ATN): should not be treated unless patient has arrhythmias, hemodynamic instablity, hyperkalemia, or seizures
    • Administered calcium may complex with phosphate and produce metastatic calciification (especially intramuscularly)
  • Hypercalcemia (During Recovery/Diuretic Phase of ATN): no treatment necessary (as this occurs due to increased 1,25-Dihydroxyvitamin D3, which occurs during this phase)
  • hyperphosphatemia : usually not clinically significant (but will respond to urinary alkalinization with diuresis
  • Hyperuricemia: usually not clinically significant and does not require treatment

IVF Hydration + Urinary Alkalinization

  • IVF Hydration (Normal Saline) + Bicarbonate Drip (3 Amps Sodium Bicarb/1L D5W): titrate bicarbonate drip + normal saline IVF (and diuretics PRN) to maintain urine outpt of >200 ml/hr + urine pH >6.5-7.0
    • Role of Hydration
      • Expansion of extracellular volume is critical: injured myocytes sequester fluids
      • Expansion of intravascular volume increases the glomerular filtration rate, oxygen delivery, and dilutes myoglobin and other renal tubular toxins
      • Although there are no randomized trials of hydration in rhabdomyolysis, retrospective studies in crush injury patients indicate that early (pre-hospital) IVF hydration improves prognosis
      • Patients with CK >15,000 IU/L may require IVF resuscitation in excess of 6L
    • Role of Urinary Alkalinization
      • Urinary alkalinization decreases ferrihemate and myoglobin cast formation (at urine pH >6.5-7.0)
      • Recommended for patients with CK >6000 IU/L
      • Urinary alkalization should be considered earlier in patients with acidemia, dehydration, or pre-existing renal disease
      • Although randomized trials are lacking, retrospective and animal studies support this practice
      • Bicarbonate infusion may precipitate hypocalcemia: must follow serial calcium during bicarbonate infusion
    • Invasive Monitoring (Central Venous Pressure, Swan-Ganz Catheterization, Arterial Line): may be required to assure adequate fluid resuscitation (especially in patients with cardiac or renal disease)
    • Role of Diuretics: lasix or mannitol may be considered in cases with oliguria despite adequate intravascular volume (however, these should be avoided in cases with inadequate intravascular volume)

Monitor Serial CK Levels + Myoglobinuria

  • Follow serial CK levels at least q6hrs
  • Aggressive IVF resuscitation should be continued until myoglobinuria is cleared

Hemodialysis

  • May be required in cases with AKI + refractory hyperkalemia/acidosis or pulmonary edema/congestive heart failure

Free-Radical Scavengers/Antioxidants

  • Examples: pentoxifylline, vitamin E, and vitamin C
  • Despite animal studies, these have an unclear role in management of rhabdomyolysis

Treatment of Fractures/Sites of Muscle Injury

  • Orthopedic treatment, as required
  • Management of Compartment Syndrome (see Compartment Syndrome, [[Compartment Syndrome]]): if present
    • Intracompartment pressure >30 mm Hg: requires fasciotomy
    • Prolonged elevated intracompartmental pressure may lead to further muscle injury and/or irreversible peripheral nerve injury

References

  • Factors predictive of acute renal failure in rhabdomyolysis. Arch Intern Med. Jul 1988;148(7):1553-7 [MEDLINE]
  • Rhabdomyolysis and secondary renal failure in critically ill surgical patients. Am J Surg 2004; 188:801– 806 [MEDLINE]
  • Hypocalcemia and hypercalcemia in patients with rhabdomyolysis with and without acute renal failure. J Clin Endocrinol Metab. 1986 Jul;63(1):137-42 [MEDLINE]