Early water intake restriction to prevent inappropriate antidiuretic hormone secretion following transsphenoidal surgery: low BMI predicts postoperative SIADH.

OBJECTIVE

The goals of this study were to assess the incidence of and risk factors for the syndrome of inappropriate antidiuretic hormone secretion (SIADH) in patients following transsphenoidal surgery (TSS), and to validate the effectiveness of early prophylactic restriction of water intake.

DESIGN

Retrospective analysis was performed for 207 patients who had undergone TSS, including 156 patients not placed on early prophylactic water restriction. Sixty-four patients received treatment for SIADH.

METHODS

We compared the incidence of SIADH between patients with and without early water intake restriction, and analyzed various risk factors for SIADH using statistical analyses.

RESULTS

BMI was significantly lower for patients with SIADH than for those patients without SIADH. Statistical analysis revealed that the threshold BMI predicting SIADH was 26. Serum sodium levels on postoperative days 5-10 and daily urine volumes on postoperative days 5-10 were significantly lower in patients with SIADH than in those without SIADH. Postoperative body weight loss on days 6, 8, 10, and 11 was significantly higher in patients with SIADH. The incidence of SIADH after starting prophylactic water intake restriction (14%) was significantly lower than the rate before early water restriction (38%; P<0.05).

CONCLUSIONS

SIADH is relatively common after TSS, and serum sodium concentrations and daily urine volumes should be carefully monitored. Patients with low preoperative BMI should be closely observed, as this represented a significant preoperative risk factor for SIADH. Early prophylactic water intake restriction appears effective at preventing postoperative SIADH.