receives Ringer's lactate solution at a rate of 4 ml/kg/h for the first-10 kg of body weight, 2 ml/kg/h for the second-10 kg of body weight, and 1 ml/kg/h for each further kg of body weight. The deficit volume is calculated as the maintenance volume multiplied by fasting hours and given as follows: 50% of the volume in the first hour, 25% of the volume in the second hour, and 25% of the volume in the third hour, in addition to the aforementioned maintenance volume

Patients in the RG receives Ringer's lactate solution at a rate of 3 ml/kg/h from the start to the end of surgery.

Lung ultrasound with a curvilinear probe (DDED) is performed in all patients in a supine position on the lateral wall of the chest at approximately the level of the lower ribs using an ultrasound probe at a frequency of 4-12 MHz (AcusonX300, Siemens Korea, Seoul, South Korea). The mean number of B-lines detected on the ultrasound image and the percentage of patients who showed B-lines on their images were recorded. The mean of three measurements is used. Inter-observer variability is estimated to be 0.766 (95% confidence interval 0.675-0.847).

volume overload using lung ultrasound according to The mean number of B-lines detected on the ultrasound image