Abstract: Objective:To explore the significance of body fluid balance in prevention of cardio-pulmonary complications in elderly patients after thoracotomy.Methods:One hundred and thirty-five elderly patients undergoing thoracotomy were grouped according to the volume of liquid in 1-3 days after thoracic surgery.The cases with positive balance of body fluid (≥ 800 ml) were enrolled in groupⅠ,cases maintaining negative balance in groupⅡ and the others in group Ⅲ.A retrospective analysis and comparison about the incidence of cardio-pulmonary complications were made among the three groups.Results:In group Ⅰ,9 cases presented postoperative cardio-pulmonary complications,including 5 cases of cardiovascular complications and 8 cases of respiratory complications,and 2 patients died;in group Ⅱ,5 cases presented postoperative cardio-pulmonary complications,including 2 cases of cardiovascular complications and 4 cases of respiratory complications,and no one died;in group Ⅲ,15 cases developed postoperative cardio-pulmonary complications,including 5 cases of cardiovascular complications and 13 cases of respiratory complications,and 1 patient died.The incidences of arrhythmia,heart failure,lung infections,asthma,hypoxemia,pulmonary edema and respiratory failure complications differed significantly among the three groups (P<0.05-P<0.01).In group Ⅱ,the incidence of hypoxemia had a significant reduction and no pulmonary edema or respiratory failure occurred.Conclusions:Positive fluid balance should be avoided in the elderly patients early after thoracotomy.Positive fluid balance may be turned to negative fluid balance by controlling the liquid input,which would contribute to the reduction of morbidity and mortality due to postoperative cardiopulmonary complications.