A case report on acute severe hyponatraemia following parathyroid surgery for primary hyperparathyroidism—A rare but life threatening complication

INTRODUCTION: Parathyroidectomy is a common operation, which is well tolerated and associated with low morbidity. Patients are usually discharged within 24 hours of surgery. Severe postoperative hyponatraemia is a rare complication which can cause significant morbidity including seizure, coma, respiratory arrest and even death. PRESENTATION OF CASE: We present two patients with clinically significant hyponatremia resulting in seizures and collapse within 24 hours after parathyroidectomy, an unreported complication following surgery for primary hyperparathyroidism. One patient required support on the High Dependency Unit and both were treated with fluid restriction which resulted in correction of their electrolyte balance. DISCUSSION: We believe this was caused by the relative inability to secrete a water load after surgery and non-psychogenic polydipsia. Preoperatively, neither patient was prescribed any routine medications nor did they have any risk factors for hyponatremia. Both had normal preoperative sodium levels. It is usual practice is to advise patients to increase oral water intake when they are hypercalcaemic. The aim of parathyroidectomy is to treat hypercalcaemia by stopping excess PTH secretion from abnormal parathyroid glands. These patients continued to follow this advice after surgery when they were eucalcaemic after their operation and because they were thirsty. The patients drank several litres of water in 12–24 hours after surgery. We believe that this may have contributed to this complication. CONCLUSION: Healthcare professionals need to be aware of this complication and patients should be advised to restrict intake of free water after surgery.