Serum sodium changes during and after transuretheral prostatectomy

OBJECTIVE: This prospective study aims at determining the effect of transurethral resection of the prostate on serum sodium levels during and after the procedure.

METHODS: One hundred consecutive unselected patients with prostatic obstructive symptoms over a period of 11 months underwent transurethral resection of the prostate using continuous flow irrigation with 1.5% glycine running from a height of 70 cm above the table level under epidural anesthesia and were given 1L of intravenous normal saline/hour during the procedure. Resection time ranged between 25 and 90 minutes (mean 32) and was less than 45 minutes in 91 patients (91%). No postoperative irrigation or diuretics were given and the patients were given food and liberal fluids immediately after the operation.

RESULTS: Fifty-four patients (54%) had intraoperative reduction of serum sodium ranging between 2 and 7 mmol/L (mean 3.5), 18 of whom showed further drop of 2-10 mmol/L after 24 hours (mean 3.4). Twenty-five patients (25%) did not have any intraoperative change in their serum sodium level, 6 of whom dropped their serum sodium 24 hours later. After 24 hours, 41 patients (41%) ended with serum sodium lower than their preoperative level by 2-12 mmol/L (mean 4%), 3 of whom had a drop of 10-12 mmol/L. The reduction was manifested 24 hours after the procedure in 27 patients (27%). None of the patients had transurethral resection syndrome nor its prodromal manifestations.

CONCLUSION: After transurethral resection of the prostate, hyponatremia can occur as late as 24 hours postoperatively. Short operative time, giving intravenous sodium supplement intraoperatively and avoiding postoperative irrigation were perhaps factors in avoiding drastic hyponatremia and transurethral resection syndrome in this prospective series of unselected patients.