Page 83 - Journal of Special Operations Medicine - Fall 2016

An Ongoing Series

Exertional Rhabdomyolysis

Epidemiology, Diagnosis, Treatment, and Prevention

Joseph J. Knapik, ScD; Francis G. O’Connor, MD, MPH

ABSTRACT
Exertional rhabdomyolysis (ER) is a medical condition Keywords: exertional rhabdomyolysis; physical activity; kid-
whereby damage to skeletal muscle is induced by ex- ney injury, acute; myoglobin, free
cessive physical activity in otherwise healthy individu-
als. The individual performs so much activity that he/
she presumably depletes local muscle energy stores Introduction
and muscle cells are unable to maintain cellular integ-
rity, resulting in cell damage and the release of cellular Rhabdomyolysis is a medical condition defined as phys-
contents, with resultant secondary complications. In ical damage to striated muscle fibers due to mechanical
the military services, the incidence of ER appeared to or metabolic stress that results in the release of muscle
increase in the period 2004 to 2015. Risk factors for cell contents into the circulation. These muscle cell con-
ER include male sex, younger age, a prior heat injury, tents may include (but are not limited to) creatine kinase
lower educational level, lower chronic physical activity, (CK), myoglobin, calcium, potassium, organic acids,
and activity in the warmer months of the year. Acute and proteases. Rhabdomyolysis can be induced by either
kidney injury is the most serious potential complication direct physical trauma or a nonphysical injury. Direct
of ER and is thought to be due to a disproportionate trauma includes such mechanisms as a crushing injury,
amount of free myoglobin that causes renal vasocon- thrombosis, hyperthermia (heat stroke), or electrical
striction, nephrotoxic effects, and renal tubular obstruc- shock. Nonphysical injuries include metabolic myopa-
tions. Patients typically present with a history of heavy thies, drugs, toxins, infections, and endocrine disorders,
and unaccustomed exercise with muscle pain, swelling, such as hypothyroidism. Metabolic myopathies are
weakness, and decreased range of motion, largely lo- uncommon and occur in individuals who have genetic
calized to the muscle groups that were involved in the disorders that result in the inability to deliver adequate
activity. Diagnostic criteria include the requisite clinical energy to the muscles (e.g., McArdle disease [inability
presentation with a serum creatine kinase level at least to use muscle glycogen], carnitine palmitoyl transferase
level 5 times higher than the upper limit of normal and/ deficiency, phosphofructokinase deficiency). 1
or a urine dipstick positive for blood (due to the pres-
ence of myoglobin) but lacking red blood cells under Exertional rhabdomyolysis (ER) is a subcategory of
microscopic urinalysis. Core treatment is largely sup- rhabdomyolysis that involves damage to skeletal mus-
portive with aggressive fluid hydration. Although the cle induced by excessive physical activity in otherwise
great majority of individuals return to activity without healthy individuals. In ER, the precipitating event is
consequence, patients should initially be stratified into generally physical activity in excess of that to which the
high and low risk for recurrence, and those at high risk individual is accustomed. The individual performs so
provided additional evaluation. Risk of ER in normal much activity that they presumably deplete local muscle
healthy individuals can be reduced by emphasizing energy stores; in turn, myocytes (muscle cells) are unable
graded, individual preconditioning before beginning a to maintain cellular integrity, resulting in cell damage
more strenuous exercise regimen after recommended and the release of cellular contents. Acute kidney in-
work/rest and hydration schedules in hot weather, and jury is the most serious complication of rhabdomyolysis
discussing supplements and medications with knowl- and is thought to be due to free myoglobin. Myoglobin
edgeable medical personnel. causes renal vasoconstriction, nephrotoxic effects, and

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