Evaluation of Patients After Cardiac Surgery: Novel Ultrasound Parameters for Quantification of Renal Perfusion & Analysis of Phenylephrines' Effect on Invasive Haemodynamics and Echocardiographic Measures

"Three time points: before, during and 20-30 minutes after infusion of phenylephrine.~Patients will receive an infusion of up to 1 mcg/kg/min phenylephrine intravenously to raise mean arterial pressure with 20 mmHg for 10 minutes. Infusion of phenylephrine will start at 0.1 mcg/kg/min with subsequent titration to effect."

"Six time points based on combinations of the following:~Three different levels of PEEP (as set on the ventilator): 0, 6 and 12 mmHg. Two different positions: 1) torso elevated 30 degrees, legs horizontal and 2) torso horizontal, legs elevated 30 degrees."