Recognizing and avoiding significant maternal hyponatremi

Abstract

Hyponatremia during peripartum period is a recognized but underreported complication. Hyponatremia has significant adverse effects on mother as well as infant. Hyponatremia can be dilutional or nondilutional. Dilutional or hypervolemic hyponatremia is more common during the labor and postpartum period. The blood sodium concentration during pregnancy is lower, 130–140 mmol/L, which is being considered normal compared to 135–145 mmol/L in nonpregnant women. Thus, when the blood sodium level is below 130 mmol/L, we should consider it as hyponatremia of pregnancy. Oxytocin can play a major role to cause dilutional hyponatremia if large volumes of hypotonic fluids are consumed or infused intravenously simultaneously. Hyponatremia during labor is such a complex problem that it can be the result of several factors. In hyponatremia, there is progressive dysfunction of the neurological system, which in association with cerebral edema results in various symptoms. Symptoms may vary from headache, nausea, vomiting, lethargy, muscle cramps, and disorientation, progressing to seizures, coma, respiratory arrest, and death. A proper clinical history and various blood tests including serum sodium are important to diagnose the severity of hyponatremia. Women in labor should be advised to drink water only up to their thirst impulse; excessive fluid intake should be avoided. The treatment depends on cause, severity, and duration of hyponatremia, as well as clinical status of patient, and associated comorbidities. Once acute water intoxication and hyponatremia have been diagnosed, it is necessary to correct the hyponatremia by water restriction and to watch sodium concentration in the blood. Severe hyponatremia (sodium <125 mmol/L + symptoms) is a medical emergency. The primary idea of treatment should be to improve symptoms instead to normalize the blood sodium level.