, et al
Effects of hydration on blood rheology in sickle cell trait carriers during exercise
Am J Physiol Heart Circ Physiol
; doi:

Investigators from Guadeloupe and Senegal measured blood and plasma viscosity in 11 college athletes with sickle cell trait (SCT) and 12 college athletes with normal hemoglobin (controls) in response to 40 minutes of submaximal exercise (55% aerobic peak power) performed in two conditions: one with free access to water and one without access to water. Viscosity was measured prior to exercise, at the end of exercise, and after a two-hour recovery. No differences were noted between the SCT group and controls for height, weight, age, maximum heart rate, peak power output, core body temperature, hematocrit, or volume of water ingested. The mean concentration of HbS in the SCT group was 38% ± 0.9%.

The SCT group and control groups lost 1.0 ± 0.7 kg and 1.6 ± 0.6 kg of body weight, respectively, following water-restricted exercise, while subjects in both groups with access to water did not lose weight during exercise. Blood viscosity at rest was greater in SCT subjects than in the control group. With exercise, blood viscosity in the control subjects increased and then returned to normal after the two-hour recovery regardless of whether they had access to water. In the SCT subjects, however, blood viscosity failed to normalize after two hours of recovery unless the subjects received hydration during the exercise session.

The authors conclude that the extended blood hyperviscosity state observed in the SCT patients without access to water during exercise could be considered a risk factor for exercise-related adverse events, including sudden death. Adequate hydration of SCT carriers during exercise should be strongly promoted to reduce the risk of complications due to blood hyperviscosity.

Dr Villella has disclosed no financial relationship relevant to this commentary. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.

SCT is exceedingly common, with more than 100 million carriers worldwide. More than two million persons in the United States carry SCT, representing about 8% of the African American population, 0.5% of Hispanics, and 0.2% of whites.1 Carriers are at increased risk for complications from traumatic hyphema, hyposthenuria, renal papillary necrosis, renal medullary carcinoma, splenic infarction, venous thromboembolism, and exertional rhabdomyolysis.1,2 

An association of SCT and sudden death was first described in 1970 when four US Army recruits died during or immediately after strenuous exercise during basic training.3 Since then, multiple reports of sudden death during exercise have been reported in individuals with SCT.4 

The current study provides much-needed basic science data to complement these clinical studies. Although an association between hyperviscosity and the risk of severe illness from strenuous exercise among individuals with SCT has yet to be demonstrated, the findings of this study are illuminating. The major abnormality found in the...

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