Clinical Research Directory

* The cFT is defined as the time between the onset of systolic flow until closure of the aortic valve corrected for the HR and has been found to correlate with the intravascular volume. * carotid ultrasound imaging will be performed 10 minutes before induction of general anesthesia in the preoperative holding area. * Ultrasound measurements will be performed under a vascular setting with a 6.0 to 13.0MHz linear array transducer * The right common carotid artery cFT will be measured in supine position with their heads tilted 30° to the left * After that, a pulse wave Doppler will be chosen, and the sampling frame will be positioned at an angle of less than 60° in the region of the carotid artery with the best color flow to acquire the blood flow spectrum.

* The IVC will be examined while the patient has been spontaneously, quietly breathing and lying in the supine position for at least 5 min before assessment. * A two-dimensional image of the IVC as it entered the right atrium will be obtained through the paramedian long-axis view via a subcostal approach using a curvilinear phased array probe (2-5 MHz) * Then, using M-mode imaging produced at a medium sweep speed, changes in IVC diameter with breathing will be evaluated 2 to 3 cm distal to the right atrium. * During the same respiratory cycle, measurements will be made of the IVC's greatest expiratory diameter (dIVC expiration) and lowest inspiratory diameter (dIVC inspiration). The formula IVCCI = (dIVC expiration - dIVC inspiration) × 100/dIVC expiration will be used to determine IVCCI as a percentage. (12) * IVCCI will be assessed by the same trained anesthesiologist who was blinded to postin duction hemodynamic measurements.