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Sarah C. Lassey, MD, of the Brigham and Women’s Hospital, Boston, and colleagues noted that a rise in the number of women choosing a home labor means health care professionals may be more likely to encounter patients with hyponatremia secondary to prolonged labor and excessive hypotonic fluid consumption.
They presented the cases of two patients who were transferred to their labor and delivery unit with hyponatremia after a prolonged labor, published in Obstetrics & Gynecology. One woman presented with somnolence and confusion. The other woman was alert on arrival, but post partum had slurred speech and blurry vision.
“A likely mechanism for hyponatremia in these cases includes endogenous oxytocin and excessive free water consumption in the setting of hypovolemia,” they suggested.
One of the patients was managed with an intravenous infusion of normal saline and went on to make a full recovery after being monitored in the intensive care unit.
The other patient also was managed with normal saline, but her serum sodium level rose by 6 mmol/L within 3 hours of delivery, raising concern that the serum sodium correction was dangerously rapid. After consultation with a nephrologist, the patient’s saline IV was discontinued, and she was given desmopressin acetate to “reduce rapid diuresis of free water excretion,” they said.
“The goal of treatment should be to raise the serum sodium concentration by 1-2 mmol/L per hour, with a maximum increase ranging from 8 mmol/L in 24 hours to 25 mmol/L in 48 hours,” Dr. Lassey and colleagues noted. “The risk of raising the serum sodium concentration too quickly is osmotic demyelination syndrome, which has been reported with a serum sodium level increase of more than 12 mmol/L in 24 hours.”
Hyponatremia should be considered in women presenting as home birth transfers and in women undergoing prolonged labor at the hospital, they concluded. It also makes sense to perform electrolyte testing on admission for women with a long labor prior to coming to the hospital and for those whose labor becomes prolonged who drink a lot of fluids.
Considering the risks associated with hyponatremia, if suspicion is high, it may be prudent to start isotonic fluids before lab results are back, they said. Symptoms of mild hyponatremia include headache, lethargy, nausea, vomiting, and anorexia. Moderate hyponatremia can present as agitation, disorientation, and psychosis; if severe, hyponatremia may present as seizure, coma, or death.
Also alert your neonatal colleagues in cases of maternal intrapartum hyponatremia, because “neonatal serum sodium level will be reflective of the mother’s serum sodium level,” Dr. Lassey and associates added.
Dr. Daniela Carusi received payment from UptoDate. The other authors did not report any potential conflicts of interest.
SOURCE: Lassey SC et al. Obstet Gynecol. 2019. doi: 10.1097/AOG.0000000000003306.