Infection

• Staphylococcal Toxic Shock Syndrome (see Staphylococcal Toxic Shock Syndrome, [[Staphylococcal Toxic Shock Syndrome]])

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

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

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