Nexfin system This device provides continuous blood pressure monitoring and parameters of heart function (stroke volume, cardiac output, stroke volume variation, systemic vascular resistance and dp/dt) via finger cuff that contains photo-plethysmograph sensor to monitor arterial volume and pressure. The sensor is a small, 6 by 3 cm cuff, that is placed over the middle of the finger (see picture below). The parameters from the device have been validated to traditional non-invasive blood pressure measurements 5 and traditional cardiac output assessment devices 6. The device inflates to a pressure that allows for assessment of the pulsatility of the arteries of the digit. It is important to note that the device does not significantly reduce perfusion to the digit and has been FDA approved for over two hours of continuous use (www. http://www.edwards.com/eu/products/mininvasive/pages/clearsightsystem.aspx). For this study the device will be placed on the patient for no more than 5 minutes.