Hyponatraemia : identification and evaluation in the marathon medical area

Exercise-associated hyponatraemia (EAH) in marathon runners has been reported in the medical literature with incidence varying from 0-130 per 1000 finishers. EAH assessment is enhanced utilising a combination of race weight changes, screening questions, vital signs and clinical examination. Those who fail to lose 0.75kg are seven times more likely to be hyponatraemic than those who lose >0.75kg. Because EAH presentations vary, a three-level surveillance system may help identify mild to moderate cases of EAH that may progress and speed treatment for those in need. After the initial evaluation, the clinical response to treatment is very important to evaluating the severity of EAH. For mild symptomatic hyponatraemia, restrict hypotonic fluids until the runner is urinating and give oral hypertonic solutions if the runner can take oral fluids. For severely symptomatic EAH, intravenous 3% sodium chloride solution will speed recovery and improve outcomes. Pre-race education addressing early symptoms and expected weight changes as well as follow-up instructions detailing the appropriate post-race fluids should be available to all registered runners and specifically given to those runners monitored/treated in the medical area.