The objective of the trial was to explore the effect of different infusion volume on perioperative bladder and blood volume in patients undergoing daytime surgery assisted by bladder and vascular ultrasound and transthoracic echocardiography.

The objective of the trial was to evaluate the effects of different infusion volume of Ringer's solution acetate (2 ml/kg,8ml/kg, 16ml/kg) on bladder volume, hemodynamics,transthoracic echocardiography and vascular ultrasound including the inferior vena cava(IVC) and the right subclavian vein(SCV) diameter and the IVC and SCV collapsibility index in patients undergoing daytime surgery through a randomized controlled clinical study, so as to provide better guidance for clinical transfusion avoiding bladder catheterization . The patients in this trial were visited before induction and discharge from the postanaesthesia .We also collected the first time and times of micturition and whether the patients have the dysuria.

Inclusion Criteria:

• 1. ethnic Chinese;
• 2. age, 18 to 65 years old;
• 3. American Society of Anaesthesiologists (ASA) physical status I or II;
• 4. Daytime patients scheduled for general anesthesia

Exclusion Criteria:

• Patients unwilling to cooperate with the experiment
• Body mass index exceeding 30 kg/m2;
• Patients with a history of heart ,liver and Renal failure ,hypertension,diabetes mellitus or arteriosclerosis; and any allergy to drugs used in the study.
• Patients with the urinary diseases, such as kidney, ureteral calculi and tumors, prostatic hypertrophy.