Upon arrival to the operating room, routine monitors in the form of pulse oximetry, electrocardiogarm and non-invasive blood pressure monitors were applied. Intravenous line was secured and routine premedications (ranitidine 50 mg and ondansetron 4 mg) were administered.
IVC evaluation was done for the patients in the supine position. The examination was performed after 5 minutes rest. A curved ultrasound transducer set to abdominal mode (1-5 MHz; Acuson x300; Siemens Healthcare, Seoul, Korea) was placed in the subcostal area to visualize the IVC in the paramedian long-axis view. The IVC was visualized using two-dimensional mode as it enters the right atrium; then, pulse wave doppler was used to differentiate the IVC from the aorta. Respiratory variations of the IVC diameter were evaluated using M-mode imaging at medium sweep speed 2 to 3 cm distal to the right atrium. The measures were obtained 3 times and their average was calculated. Maximum and minimum IVC diameters over a single respiratory cycle were used to calculate the collapsibility index as follows:
(dIVCmax- dIVCmin)/dIVCmax Collapsibility index was expressed as a percentage.
IJV measurements were obtained in the supine position using a linear ultrasound transducer (5 - 13 MHz; Acuson x300; Siemens Healthcare, Seoul, Korea). The probe was placed horizontally at the middle level of the thyroid cartilage. After obtaining a clear transverse view of the right IJV, the IJV area was measured. The measures were repeated after changing the patient's position to the 10° Trendelenburg position. The maximum area of the IJV in the supine and Trendelenburg positions was recorded and the rate of change in IJV area was calculated as follows:
IJV change rate with posture = (IJV area in Trendelenburg position - IJV area in supine position)/(IJV area in Trendelenburg position) All ultrasonographic measurements were performed by a single trained anesthesiologist.
IJV measurements were obtained in the supine position using a linear ultrasound transducer (5 - 13 MHz; Acuson x300; Siemens Healthcare, Seoul, Korea). The probe was placed horizontally at the middle level of the thyroid cartilage. After obtaining a clear transverse view of the right IJV, the IJV area was measured. The measures were repeated after changing the patient's position to the 10° Trendelenburg position. The maximum area of the IJV in the supine and Trendelenburg positions was recorded and the rate of change in IJV area was calculated as follows:
IJV change rate with posture = (IJV area in Trendelenburg position - IJV area in supine position)/(IJV area in Trendelenburg position) All ultrasonographic measurements were performed by a single trained anesthesiologist.
