Endocrine Abstracts

Background: Severe hyponatremia can be associated with oxytocin infusion. The incidence of hyponatraemia after oxytocin is around 5%. There are reported cases of serious neurological complications including seizures, coma and maternal death.

Case report: A 37-year-old female with known partial central diabetes insipidus following a head injury was established on Desmopressin nasal spray 10 mg twice a day. She had an uneventful pregnancy on the same dose. For delivery, she was commenced on Oxytocin infusion and eventually underwent a caesarean section and delivered a healthy baby. Eleven days post-partum, she presented with a 1-day history of frontal and parietal headache with no other associated symptoms. It did not improve with paracetamol or Ibuprofen. Her blood test showed sodium of 119 mmol/l. She was admitted under the medical team in a Gynaecology ward. The medical team reviewed her in the evening. Her examination showed euvolemic status and Brisk reflexes. Other biochemistry showed serum osmolality 246mOsmol/kg, urine sodium 6 mmol/l and urine osmolality 445mOsmol/kg in keeping with SIADH. The endocrine team was consulted and advised to hold Desmopressin, replace serum sodium slowly by less than 8 mmol/24 hours with an IV infusion of 125 ml/hour normal saline, repeat the serum sodium after 6 hours, check for 9 am cortisol and TFT, request an urgent pituitary MRI, and keep a strict input/output fluid chart. The Sodium level after 6 hours showed Na of 126 mmo/l. Unfortunately, the fluid was stopped later and VBG after 6 hours reported Sodium of 136 mmol/l while the serum sodium level was 139 mmol/l. The Urine output was noted to be 8 L in 12 hours. The patient was given 500ml of Dextrose 5% over 1 hour and prescribed her usual Desmopressin dose. The ITU team was called and an urgent Head & Pituitary MRI was done with no abnormality. Cortisol & TFT were normal. The patient was observed for 2 days and discharged later.

Conclusion: The antidiuretic effect of oxytocin can result in water intoxication and hyponatremia that may lead to serious neurological sequelae and maternal death. Early suspicion could prevent these complications. Rapid correction of sodium should be avoided as it can result in osmotic demyelination syndrome which can cause profound neurological damage. Our patient had oxytocin for delivery 11 days prior to her presentation and was also exclusively breastfeeding. The postulated theory for her profound hyponatraemia was secondary to synthetic oxytocin as well as oxytocin produced from exclusively breastfeeding.