Disorders of sodium balance

Editor—Reynolds et al do not specifically mention the acute hyponatraemia quite commonly seen during transurethral resection of the prostate.¹ The syndrome may present dramatically, with pulmonary oedema, convulsions, and, occasionally, cardiac arrest when the plasma sodium falls below 100 mmol/l.

Sodium must be corrected urgently or the patient may die. I give 200 ml of 8.4% sodium bicarbonate (200 mmol sodium) as soon as I have diagnosed the syndrome and taken a blood sample to confirm the sodium value. I then correct the sodium value to 120 mmol with further boluses of 8.4% sodium bicarbonate. Once the sodium value is above 120 mmol, there is little clinical urgency and the sodium concentration can be allowed to rise more slowly with the help of normal saline and furosemide 20 mg intravenously.

I have treated 18 patients in this way without any deaths and without any evidence of brain damage. The transient metabolic alkalosis that accompanies this treatment does not seem to cause any problems to the patient.