The Effects Of Different Preoperative Fasting Periods For Liquid And Preoperative Clyster On Renin-angiotensin-aldosterone System

Objective: To research the effect of 12-h solid food and liquidfasting and 12-h solid food fasting, 2-h liquid fasting before operation on renin-angiotensin-aldosterone system(RAAS).Methods: We studied 90 ASA I and II patients undergoing elective cholecystectomy. All patients were allocated randomly into three groups (n=30 patients in each): 1) D group, patients were asked to fast after 20:00 of the day before surgery, but there were no drink restrictions until 2h before operation. They ingested 200ml-350ml water 2h before surgery; 2) F group, patients fasted from 20:00 of the day before surgery; 3) FC group, patients not only received preoperative 12-h solids and liquids fasting, but were instructed to be clysterized. Hematocrit ratio, plasma concentration of Na+, plasma renin activity, and plasma concentration of angiotensin Hand aldosterone before and after fasting were analyzed. Result: (1) Hematocrit ratio(HCT) and plasma concentration of sodium: There were no differences in HCT between before and after fasting in Dgroup. But in F group and FC group, the HCT after fasting were greater than that before fasting (P<0. 05). Na+ did not change between before and after fasting in three groups (P>0. 05). (2) Plasma Renin Activity (PRA), Angiotensin II(AII) and Aldosterone(ALD) : PRA, A II and ALD after fasting in FC group were greater than before fasting(P<0. 05). The increases in PRA, AII and ALD after fasting observed in F group did not reach statistical significance. In D group PRA, AII and ALD after fasting were consistent with them before fasting(P>0. 05). Conclusion (1) Preoperative 12-h food and drink fasting induced a mild dehydration and a rise in ALD. That may be unfavorable to the patients during operation. So we confirmed itis beneficial for the patients to have no drink restrictions until 2h before surgery, and to ingest some water 2 hours before surgery. (2) As for those who not only fasted but also were clysterized, the dehydration was more serious, and RAAS is activated. So, water should be ingested or intravenous fluids should be given until 2h before surgery .