Predictability of Preoperative Carotid Artery Corrected Flow Time for Hypotension After Spinal Anesthesia in Patients Undergoing Cesarean Section

First, place a 4.5-12.0 MHz linear array transducer vertically on the neck with the probe marker facing the patient's head. A long axis B-mode image of the right common carotid artery is obtained at the lower border of the thyroid cartilage. The sample volume is then placed in the center of the lumen located approximately 2 cm proximal to the carotid bifurcation. Next, pulsed wave Doppler tracing is performed in the arterial blood flow. The cycle time using the calliper function in an ultrasonic machine is obtained by measuring the interval between heartbeats at the beginning of the Doppler blood flow upstroke and the Flow time is measured as the time from the beginning of the systolic upstroke to the dicrotic notch.