Endocrine Abstracts

Background: Ovarian Hyperstimulation Syndrome(OHSS) complicates up to a third of assisted reproduction cycles. Severe hyponatremia is a rare complication of OHSS. We report a case of severe hyponatremia to highlight the challenges in management.

Case Report: 31 year-old female presented with breathlessness, abdominal pain, increased abdominal girth and hyponatremia (sodium 122 mmol/l) eight days following embryo transfer after ovulation induction with gonadotropins. On examination she had moderate dehydration, reduced bi-basal air entry and ascites. She received 1 litre 0.9% normal saline (NS) and 1litre Hartman’s solution. Repeat investigations showed sodium 121 mmol/l, plasma osmolality 263mOsm/kg, urine osmolality 431mOsm/kg, urine sodium<20mEq/l, random Cortisol 607nmol/l, TSH 8.19mU/l and free T4 21.3pmol/l, indicative of hypovolemic hyponatremia and subclinical hypothyroidism. Chest x-ray showed bilateral moderate pleural effusions. She was started on Levothyroxine. She had 3litres NS and 2units of human albumin solution over 48hours. She had ascitic drainage (6 litres). Hyponatremia worsened with repeat sodium 117 mmol/l. She was given 300 mls 1.8% hypertonic saline and repeat sodium was 114 mmol/l. With no improvement, she was given a trial of Tolvaptan 15 mg for two days. Sodium increased to 128 mmol/l and Tolvaptan was stopped. Weight, abdominal girth, and fluid balance were monitored closely. HCG testing confirmed pregnancy. Two days after discharge she was re-admitted with ascites and underwent paracentesis. She had euvolemic hyponatremia (sodium 132 mmol/l) which improved spontaneously.

Conclusion: Severe OHSS can present with severe hyponatremia due to increased vascular permeability and loss of fluid into the third space. Intravenous fluid replacement is essential to address the acute need for volume expansion. In case of refractory hyponatremia despite aggressive fluid resuscitation, treatment with hypertonic saline or Tolvaptan should be considered.