The Carotid Artery Corrected Flow Time (FTC) concept is not new. In fact, it has been well studied as a marker of preload and afterload with Transesophageal Doppler (TED). TED monitors display a wave form of the velocity versus time similar to the image one might obtain doing pulsed wave Doppler (PWD) of the carotid artery. With TED, the waveform has a triangular appearance. The apex of the triangle represents peak velocity, which along with mean acceleration reflects cardiac contractility. The area under the systolic portion of the curve is equal to stroke distance, and when multiplied by the cross sectional area of the descending aorta this value can be used to estimate cardiac output predicated on the assumption that the descending aorta receives 70% of cardiac output. The investigators are interested in the base of the triangle representing systolic ejection time. When corrected for heart rate by dividing by the square root of cardiac cycle time we have the FTC. The FTC would be expected to increase with enhanced preload or reduction in afterload; conversely it should decrease with a reduction in preload or increase in afterload. One study performed in 20 neurosurgical patients with TED showed that the FTC was able to predict fluid responsiveness when used as a static measure with a cutoff of 357 ms prior to loading with 7 ml/kg of hydroxyethyl starch solution. The area under the receiver operating curve (ROC) was 0.944.