Corrected Carotid Flow Time for Predicting Spinal Anesthesia-induced Hypotension

Spinal anaesthesia is a standard technique frequently preferred for caesarean section. However, spinal anaesthesia-induced hypotension remains a critical problem causing undesirable maternal symptoms such as nausea, vomiting and dyspnoea and adverse consequences for umbilical acidosis and the fetus. One of the reasons aggravating hypotension is aortocaval compression of the growing uterus and consequent decrease in preload and stroke volume . Therefore, left lateral tilt position is recommended in pregnant women after the 20th gestational week to prevent supine hypotension. This position decreases uterine compression on the vena cava and increases venous return to the heart and thus stroke volume. Recently, carotid artery Doppler has been used to assess stroke volume. Many studies have shown that carotid corrected flow time increases significantly after expansion of intravascular volume in hypovolaemic patients . In one study, it was reported that the change in carotid artery blood flow time induced by passive leg raising predicts fluid sensitivity in critically ill patients. It has been reported that changes in carotid artery blood flow time against hemodynamic interventions (such as Trendelenburg position) reflect maternal hypovolemic status and distinguish hypovolemic patients with a higher risk of spinal anesthesia-related hypotension. The investigators also think that the left lateral tilt position may increase the corrected carotid flow time by affecting hemodynamics and may differentiate the patient with a high risk of hypotension.