Fast Five Quiz: Hyponatremia Essentials

Romesh Khardori, MD, PhD


October 14, 2019

Patients may present to medical attention with symptoms related to low serum sodium concentrations. However, many patients present owing to manifestations of other medical comorbidities, with hyponatremia being recognized only secondarily. In many cases, therefore, the recognition is entirely incidental. Clinical symptoms may result from the cause of hyponatremia or the hyponatremia itself. Many medical illnesses, such as chronic heart failure, liver failure, renal failure, or pneumonia, may be associated with hyponatremia. These patients frequently present because of their primary disease (eg, with dyspnea, jaundice, uremia, or cough).

A retrospective Chinese study reported hyponatremia in 116 of 175 children (66.4%) with bacterial meningitis. Multivariate analyses showed that convulsions and blood glucose levels > 6.1 mmol/L (> 110 mg/dL) were related to severe hyponatremia. Severe hyponatremia should be considered in pediatric patients with bacterial meningitis who have either of those findings.

Overt neurologic symptoms most often are due to very low serum sodium levels (usually < 115 mEq/L), resulting in intracerebral osmotic fluid shifts and brain edema. This neurologic symptom complex can lead to tentorial herniation with subsequent brain stem compression and respiratory arrest, resulting in death in the most severe cases. Symptoms of hyponatremia range from nausea and malaise with mild reduction in the serum sodium level to vomiting, lethargy, decreased level of consciousness, muscle spasms, headache, and (if severe) seizures and coma.

EAH, which develops during or immediately after physical activity, was first reported in athletes participating in long-duration, high-intensity exercise (eg, ultramarathons) particularly in hot weather, but has since been described in otherwise healthy participants in various sporting and recreational activities, including team sports and yoga classes. EAH results from drinking hypotonic fluids (water or sports drinks) beyond thirst and in excess of sweat, urine, and insensible water losses.

Read more about the symptoms of hyponatremia.


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