Page 143 - Athletic Health Handbook
P. 143
Background denominators that potentiate limited, skeletal muscle death occurs
erythrocyte sickling and predispose and the intracellular contents of the
Sickle cell trait is a condition in these individuals to potential skeletal muscle cells are released into
which an individual has inherited catastrophe. the systemic circulation. This process
one gene for normal hemoglobin initiates a potential fatal cascade
and one gene for sickle hemoglobin. One recent review cited exertional of events, including myoglobinuria
Sickle hemoglobin has an increased sickling as the leading killer in NCAA and electrolyte abnormalities.3
propensity to form large polymers Division I football in the last decade.5
on the erythrocyte cell membrane In the review of 16 conditioning- Myoglobin, a component of the
when deoxygenated.2 This sickling, related deaths, 10 (63 percent) were intracellular space within normal
or change in erythrocyte shape presumed to be due to exertional skeletal muscle, is responsible for
from coin-shaped to quarter-moon, sickling. Other causes included cardiac much of the renal damage incurred
causes sluggish flow through smaller (four), asthma (one), and exertional during rhabdomyolysis. Myoglobin
vessels and may lead to end-organ heat stroke (one). Overall, the actual contributes to acute renal failure
damage, especially within the kidney. incidence of exercise-related sudden in two major ways:
death due to exertional sickling
Those with sickle cell trait differ is likely underestimated. Lack of Direct cytotoxicity on renal
from those with sickle cell disease recognition of sickle cell trait and epithelial cells
because those with sickle cell trait few distinct pathological findings Cast formation creating
have a much lower concentration cause exertional sickling and its intra-tubular obstruction.7
of sickle hemoglobin. When the sequelae to be misdiagnosed as While potentially reversible,
intensity of activity increases, local pH exertional heat stroke and hypertrophic rhabdomyolysis and acute renal
decreases and temperature increases. cardiomyopathy during autopsies.6 failure may require renal dialysis
In both subgroups, these conditions and has mortality rates estimated
lead to increased concentrations The relative neglect of sickle cell at 20 percent.8
of deoxygenated hemoglobin and trait by many medical professionals is In addition to acute renal failure,
therefore increases in the amount of surprising given the high prevalence electrolyte imbalances, including
erythrocyte sickling.2 The propensity of the disease, which affects more hyperkalemia and hypocalcemia, are
to sickle is amplified at higher altitudes. than 2 million Americans.1 Experts grave threats during rhabdomyolysis.
While sickling does occur during have estimated that one in 12 When skeletal muscle cells die,
deoxygenated states, those with African-Americans and one in 2,000 potassium, which is found
sickle cell trait usually remain Caucasians possess the sickle cell trait.1 predominantly in the intracellular
asymptomatic without any effects This condition is more prevalent in space, is released into circulation and
of exercise performance because athletes whose ancestors come from serum potassium can reach perilous
these individuals possess a higher malarial regions of the world such heights. At serum potassium levels
ratio of normal hemoglobin.3 as Africa, South or Central America, above 5.0 mEq/l, serious cardiac
Caribbean or Mediterranean arrhythmias can occur and lead
Grave consequences can occur at countries, India, and Saudi Arabia. to cardiac arrest. The cardiotoxicity
extremes of physical exertion, even in associated with hyperkalemia
those with sickle cell trait. Multiple Exertional Sickling is further potentiated by the
case reports have described athletes and Rhabdomyolysis hypocalcemia and metabolic acidosis
and/or military personnel with that accompanies rhabdomyolysis.
sickle trait who sustained disastrous Exertional sickling is dangerous Recognition of the exertional
complications, such as fulminant for athletes because of the potential sickling is important to prevent or
rhabdomyolysis and exercise-associated for progression to rhabdomyolysis, limit progression to rhabdomyolysis.
sudden death, caused by erythrocyte a disease characterized by skeletal Features of exertional sickling
sickling during periods of increased muscle death and release of breakdown collapse are often confused with heat
activity.2,4 Indeed, the exercise-related products. Rhabdomyolysis cramping and heat stroke. However,
sudden death rate is 10 to 30 times preferentially affects those with sickle several key distinctions exist. Because
higher in sickle cell trait carriers cell trait because of the erythrocyte exertional sickling is an ischemic
compared to non-carriers.2 Heat sickling that occurs within the vessels process and not solely a product
exposure, dehydration, and intense supplying skeletal muscle.3 When of hyperthermia and lactic acidosis,
physical activity are the common the circulation to skeletal muscle is

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