ENDOMETRIAL NA-ATPASE PUMP FUNCTION AND VASOPRESSIN LEVELS DURING HYSTEROSCOPIC SURGERY IN PATIENTS PRETREATED WITH GNRH AGONIST(, K+)

Study Objective. To investigate the effects of gonadotropin-releasing hormone (GnRH) analog pretreatment on endometrial Na+, K+-adenosine tr iphosphatase (ATPase) pump function and peripheral blood vasopressin l evels, and their role in fluid absorption and mechanisms of hyponatrem ia in patients undergoing hysteroscopic endometrial ablation. Design. Prospective, randomized, placebo-controlled study (Canadian Task Force classification I). Setting. University-affiliated hospital. Patients. Seventeen women with dysfunctional uterine bleeding. Intervention, Ni ne women received a GnRH analog and eight received saline approximatel y 6 to 8 weeks before hysteroscopic ablation by electrosurgery. Measur ements and Main Results. Both before randomization and immediately bef ore surgery, endometrial biopsy samples were obtained and numbered con secutively without patient identification. Operative hysteroscopy was performed with glycine 1.5% mixed with 2% alcohol. The amount of irrig ant and irrigant deficit; blood levels of albumin and ethanol; hematoc rit and hemoglobin; changes in sodium levels; and central venous press ure were compared. The Na+, K+-ATPase pump activity was significantly increased in the GnRH analog group compared with the saline group and correlated with decreased estradiol levels (0.4 +/- 0.08 vs 0.26 +/- 0 .06 mu mol/min/ml). Vasopressin levels were significantly lower in the GnRH group (3.2 +/- 0.9 vs 7.6 +/- 1.7 mu mol/L). Mean volume of irri gant used and operating time were similar in both groups. Volume defic it, decrease in protein, and hematocrit were less in GnRH than in the saline group. Blood ethanol levels, decrease in sodium, and irrigant d eficit were significantly lower in GnRH group. Conclusion. Pretreatmen t with GnRH analogs may prevent the adverse effects oi estradiol on en dometrial Na+, K+-ATPase and creates a protective mechanism against ia trogenic hyponatremia, which is more critical in women than men in cas e of absorption of irrigating fluid. Moreover, created hypoestrogenism may enhance Na+, K+-ATPase activity in brain as well as endometrium, thus decreasing women's susceptibility to hyponatremic complications a nd brain damage. Suppressed vasopressin levels may be protective again st fluid absorption in GnRH analog-treated patients.