Rhabdomyolysis
Rhabdomyolysis: Excerpt from The 5-Minute Pediatric Consult
Thomas L. Kennedy III, MD
Rhabdomyolysis - BASICS
Rhabdomyolysis - description
Skeletal muscle injury resulting from trauma, from infection, or from inadequate delivery, production, or consumption of energy or oxygen relative to demands. Release of intracellular contents may cause severe electrolyte disturbances including life-threatening hyperkalemia, myoglobinuria, and acute renal failure.
Rhabdomyolysis - epidemiology
- Rhabdomyolysis is more common in adults, where it is seen most frequently in patients in comas resulting from heroin or cocaine abuse and long periods of remaining motionless.
- Rhabdomyolysis is uncommon in childhood and unusual in the 1st decade.
- Rhabdomyolysis may be a common clinical problem in a catastrophic disaster (e.g., an earthquake); therefore, familiarity is important.
Rhabdomyolysis - risk factors
Rhabdomyolysis - genetics
Many unusual causes of rhabdomyolysis, including muscle enzyme deficiencies, muscular dystrophy, and disorders of mitochondrial metabolism, are heritable disorders, so a careful familial family history should be sought.
Rhabdomyolysis - pathophysiology
Acute manifestations of muscle destruction, which may lead to acute myoglobinuric renal failure
Rhabdomyolysis - etiology
- Additionally, the most common causes include muscle trauma from crush or compression injury, burns, or electric shock. Others include viral illnesses (e.g., influenza, Epstein-Barr virus infection), heat stroke, severe exertion, status epilepticus, and vasculitis with myositis.
- A common cause in adolescents is exercise which is novel, intense or prolonged, often the result of competition or punitive measures, may be responsible (so-called “March Myoglobinuria”).
- Less common causes in childhood include penetrating trauma (e.g., gun shot), congenital metabolic myopathies; acute dystonic reactions; malignant hyperthermia syndrome; other infections; exposure to some medications, toxins, or illicit drugs; and severe electrolyte disturbances.
- Myopathies involving muscle enzyme or energy substrate deficiencies include carnitine palmitoyl transferase deficiency, type 5 glycogenosis, mitochondrial deficiency disorders, and phosphofructokinase deficiency.
- Rhabdomyolysis is more likely to occur after exertion in association with the dystrophinopathies, which include all forms of muscular dystrophy.
- Infections, in addition to the viral illnesses listed above, include Coxsackievirus, HIV, Plasmodium, Legionella spp., mycoplasma, SARS and toxic shock syndrome.
- Causative medications include the lipid-lowering “statin” drugs (HMG-CoA reductase inhibitors), inhalation anesthetics, propofol, cyclosporine, amphotericin B, itraconazole, and isotretinoin. An overdose of epinephrine and high dose IV norepinephrine are also on the list.
- Toxins and illicit drugs include snake, spider and vespid venoms, fish toxins, some mushrooms, hydrocarbons, ethanol, cocaine, heroin, and phencyclidine (PCP) and recently ecstasy. Rhabdomyolysis has also been reported, possibly due to copper toxicity, in Wilson disease.
- Electrolyte disturbances include hypokalemia, severe hypophosphatemia, hypernatremia, hyponatremia, hypocalcemia, and hyperosmolar states.
- It is important to remember that the muscle injury caused by severe hypokalemia (e.g., Bartter syndrome) may rapidly lead to life-threatening hyperkalemia.
- The insult may lead to muscle cell destruction or failure of membrane function with release of intracellular contents including proteins and electrolytes and uptake of large amounts of extracellular water leading to severe hypovolemia and decreased renal perfusion.
- The list of causes here is not exhaustive. Any child with sudden onset of muscle pain, tenderness, or weakness should be suspected of having rhabdomyolysis, and any child with dark urine suspected of myoglobinuria.
Rhabdomyolysis - associated conditions
In addition to the previously mentioned causes, rhabdomyolysis has also been reportedly associated with diverse conditions, including asthma, hemolytic-uremic syndrome, and diabetes mellitus. It may also occur in Kawasaki disease and adrenal insufficiency, associations which are rare, but must not be missed.
Rhabdomyolysis - DIAGNOSIS
Rhabdomyolysis - signs & symptoms
- Muscle pain or weakness
- Brownish urine
Rhabdomyolysis - history
- Increased exertion, viral illness, muscle injury, and electric shock are conditions associated with muscle breakdown and rhabdomyolysis.
- Rhabdomyolysis is associated with muscular dystrophy and reaction to drugs (e.g., anesthetic agents).
- Any prior history of illness or insult associated with rhabdomyolysis may follow certain illnesses (e.g., influenza) and insults (e.g., crush injury) and thus a history positive for these should be sought.
- Muscle pain or weakness may result from rhabdomyolysis and help suggest diagnosis if present.
- Brownish discoloration of the urine
Rhabdomyolysis - physical exam
- Palpate muscle for tenderness and, less commonly, swelling or fullness.
- Test for motor strength.
- Elicit reflexes to exclude neuropathy.
- Examine skin and mucous membranes for signs of vasculitis.
- The child with evidence of rhabdomyolysis must be examined looking for signs of child abuse.
- Examine for signs of a concomitant precipitating illness.
Rhabdomyolysis - tests
- Use of radiocontrast in imaging studies as part of diagnostic evaluation can worsen acute renal failure. Use only if absolutely necessary and be certain the child is well hydrated and voiding briskly.
- Occasionally, hypercalcemia may develop during recovery from myoglobin-induced renal failure.
Rhabdomyolysis - lab
- Serum electrolytes, calcium, and phosphorus to reveal hypo/hyperkalemia, hyperphosphatemia, and/or hypocalcemia. There may be metabolic acidosis with a wide anion gap in those conditions associated with lactate production.
- BUN and creatinine: Creatinine level may be elevated out of proportion to that of blood urea nitrogen.
- CBC and smear because many of the metabolic disorders causing rhabdomyolysis cause a hemolytic anemia as well.
- Creatine phosphokinase will be elevated to over 100 times normal in rhabdomyolysis.
- Serum carnitine
- Serum lactate
- Serum uric acid
- Urinalysis: Urine may appear brown and test positive for blood on dipstick without erythrocytes on microscopy. Granular pigmented casts are common.
- CBC may show anemia with or without microangiopathic changes in cases of hemolytic processes and hemoglobinuria.
- Definitive tests for myoglobinuria:
- Urine immunoelectrophoresis and radioimmunoassay are not generally available in clinical laboratories.
- Ammonium sulfate solubility testing is a reasonable screening test to help differentiate myoglobin from hemoglobin.
- The 2 proteins are best distinguished by the clinical setting in which they occur, the creatine phosphokinase level, and the presence or absence of hemolytic anemia.
- False positives: The result of dipstick test for blood is positive, but examination of a freshly voided urinary sediment reveals few or no erythrocytes.
- In this instance, the diagnostic possibilities are myoglobinuria or hemoglobinuria.
- Rapid rise in serum creatinine: May result from release from muscle
Rhabdomyolysis - diag proced-surgery
Muscle biopsy: Necessary to diagnose metabolic myopathies. A biopsy will demonstrate immunohistochemical features of a myopathy. Immunoblotting is helpful in evaluating the dystrophinopathies.
Rhabdomyolysis - differencial diagnosis
- Any condition associated with muscle pain, tenderness, and/or weakness. Many causes of rhabdomyolysis may be associated with these signs and symptoms but demonstrate no elevation in creatine phosphokinase levels.
- Many viral illnesses
- Lyme disease
- Suppurative myositis
- Guillain-Barré syndrome
- Collagen vascular diseases
Rhabdomyolysis - TREATMENT
Rhabdomyolysis - initial stabilization
Treatment is supportive. If an underlying cause is identified, it should be corrected or removed.
Rhabdomyolysis - general measures
- Adequate hydration (e.g., 2–3 times maintenance fluids) should be sufficient to provide brisk urine flow (e.g., > 4 mL/kg/h). Myoglobinuric nephrotoxicity is the only clinical situation in which acute renal failure can be averted by maintaining good urine flow. Alkalinization of the urine is probably beneficial. Furosemide and/or mannitol may be helpful to maintain urine output.
- Dialysis is indicated if oliguric acute renal failure occurs and/or if severe electrolyte disturbances are present.
Rhabdomyolysis - medication
- With myoglobinuria, bicarbonate therapy should be given IV to maintain the urine pH >7.0.
- If urine output declines despite adequate hydration, furosemide (1–4 mg/kg/dose IV) should be given to attempt to prevent oliguric renal failure.
- If severe hyperkalemia occurs, measures should be taken to prevent cardiac dysrhythmias (β-agonists, calcium, bicarbonate, glucose, and insulin) and to maximize elimination of potassium by the kidneys (furosemide) and/or GI tract (Kayexalate).
- With hypocalcemia, give calcium only if symptoms are present.
Rhabdomyolysis - FOLLOW UP
Rhabdomyolysis - prognosis
- Depends on extent of pre-existing irreversible renal disease, prompt recognition and institution of appropriate therapy, and the diuretic response to fluid replacement. In general, however, outlook for recovery is good.
- Prompt cessation of rhabdomyolysis may be expected when the inciting cause is corrected or resolves.
- Although most children recover promptly, severe muscle injury may cause prolonged muscle weakness and warrant follow-up by physical and occupational therapy.
- With resolution of myoglobinuria, return to normal renal function is the rule.
Rhabdomyolysis - complications
- Electrolyte release from muscle can lead to hyperkalemia, hyperphosphatemia, and secondarily to hypocalcemia.
- Acute renal failure may occur due to myoglobinuria and does in ~20–40% of patients. Dialysis is required in ~50% of those with acute renal failure. Myoglobin may exert direct renal cytotoxicity, tubular obstruction with myoglobin casts, as well as decreased renal blood flow and glomerular filtration rate as a result of hypovolemia.
- Compartment syndrome may result from muscle swelling.
- Furosemide may interfere with alkalinization of the urine.
- Use of bicarbonate may precipitate symptomatic hypocalcemia.
- Calcium therapy for severe hyperkalemia is necessary, but its use with hyperphosphatemia increases risk of vascular calcification.
- Risk factors for acute renal failure include pre-existing renal disease, delay in recognition and treatment, concurrent use of potentially nephrotoxic agents (e.g., NSAIDs), volume depletion, and either hypotension or hypertension.
- Failure to discontinue IV fluids if oligoanuric renal failure develops could produce iatrogenic fluid overload.
Rhabdomyolysis - bibliography
- Celik A, Ergun O, Ozok. Pediatric electrical injuries: A review of 38 consecutive patients. J Pediatric Surgery. 2004;39(8):1233–1237.
- DiGiacomo JC, Frankel H, Haskell RM, et al. Unsuspected child abuse revealed by delayed presentation of periportal tracking and myoglobinuria. J Trauma. 2000;49:348–350.
- Hollander AS, Olney RC, Blackett PR, et al. Fatal malignant hyperthermia-like syndrome with rhabdomyolysis complicating the presentation of diabetes mellitus in adolescent males. Pediatrics. 2003;111(6 Pt 1):1447–1452.
- Malinoski DJ, Slater MS, Mullins RJ. Crush injury and rhabdomyolysis. Crit Care Clin. 2004;20:171–192.
- Vanholder R, Sever MS, Erek E, et al. Rhabdomyolysis. J Am Soc Nephrol. 2000;11:1553–1561.
Rhabdomyolysis - CODES
Rhabdomyolysis - icd9
728.88 Rhabdomyolysis (idiopathic)
Book Source Details
- Book Title: The 5-Minute Pediatric Consult
- Author(s): M. William Schwartz MD; et al.
- Year of Publication: 2008
- Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: The 5-Minute Pediatric Consult
Authors: M. William Schwartz MD; et al.
Publisher: Lippincott Williams & Wilkins
Copyright: 2008
ISBN: 0-7817-7577-9
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