Exercise associated hyponatraemia leading to tonic-clonic seizure

A 34-year-old Filipino lady presented to the emergency department with breathlessness and muscle cramping following a Bikram yoga workout. The patient reported sweating excessively while performing 90 min of strenuous exertion in a humidified room heated to an ambient temperature of 40.6°C. After the workout she drank 3.5 litres of water before experiencing breathlessness, severe muscle cramps, nausea and general malaise. Initial investigations revealed severe hyponatraemia (120 mmol/l). Despite early sodium replacement the patient dropped her Glasgow coma scale to 9/15 and developed tonic clonic seizures, requiring intubation and admission to the intensive care unit. The hyponatraemia was slowly corrected on the intensive care unit and the patient made a full recovery over the course of 5 days. This case highlights the dangers of overzealous fluid replacement following severe exertion in a hot environment.