Abstract

Hypovolemia and reduced blood sodium levels have been reported in some athletes. Sweat sodium concentration has been shown to be directly proportional to percent plasma volume loss and, therefore, may serve as useful proxy indicator of hypovolemia. This case, a 44-year old male physician with ten years of experience in long distance triathlons and endurance racing, reports himself to be a salty, heavy sweater; has noted significant weight loss during some competitions; and, occasionally, encounters symptoms that could be attributed to hypovolemia, despite drinking to thirst. This case relates his attempts to measure sweat sodium concentration using regional patches and two tools, the Horiba LAQUA twin B-721 Compact Salt Meter and the AquaChek strip (from the swimming pool industry) as compared to a pilocarpine test using a standard approved by the Cystic Fibrosis Foundation. Both tools yielded comparable results, with wide variation in sweat sodium concentration across the samples. The AquaChek showed a consistent bias of -4.16 sodium mEq/L compared to the Horiba. Both are comparable to a pilocarpine standard and validity and reliability of each method was robust when later tested against standard saline solutions. In this case, ease of application, sufficient sweat volume, and potentially reduced contamination from body hair suggest this site for further evaluation of sweat sodium in the field. Additionally, compared to laboratory testing, each method is cost efficient.