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Abstract: SA-PO726

Acute Peripartum Hyponatremia due to Oxytocin

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Jayeola, Olakunle A., University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States
  • Pal, Chaitanya A., University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States
  • Schmidt, Darren W., University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States
  • Teixeira, J. Pedro, University of New Mexico Health Sciences Center, Albuquerque, New Mexico, United States
Introduction

Medication-induced hyponatremia is common in hospitalized patients. In addition, the physiology of pregnancy predisposes to hyponatremia. We present a case of oxytocin-induced peripartum hyponatremia.

Case Description

A 40-year-old woman with diabetes and hypertension is admitted for induction of labor at 34 weeks of pregnancy for preterm rupture of membranes. Admission serum sodium (Na) was 136 mEq/L. Oxytocin was given as an infusion over 36 h at a maximum rate of 0.034 units/min and followed by a bolus of 30 units IV for postpartum bleeding. The first Na level after oxytocin started was 129 [Figure]. At hour 30 of the infusion, Na dropped to 123 and then reached a nadir of 116 an hour after the oxytocin was discontinued. Urine studies revealed osmolality 227 mOsm/L and Na 68 mEq/L. Fluid intake was restricted, urine output increased to ≥700 mL/h for 6 h, and Na levels rapidly normalized over the next 20 h.

Discussion

Along with systemic vasodilation and arterial underfilling, pregnancy is characterized by a reset of the osmotic set point for antidiuretic hormone (ADH) release, predisposing to hyponatremia. Pregnancy-specific causes of hyponatremia include syndrome of inappropriate ADH from hyperemesis gravidarum, Sheehan syndrome, and oxytocin-induced hyponatremia. Oxytocin and ADH are cyclic nonapeptides that differ by only 2 amino acids and are synthesized by overlapping groups of neurons in the hypothalamic supraoptic and paraventricular nuclei. Both bind G protein-coupled receptors with significant overlap in affinity. This cross-reactivity gives oxytocin an ADH-like effect. While well described in the literature, oxytocin-induced hyponatremia is likely underrecognized. Nephrologists and obstetricians alike must be aware of this form of medication-induced hyponatremia, allowing for appropriate monitoring and prompt recognition to prevent the maternal and fetal morbidity associated with hyponatremia in pregnancy.