Influence of Continuous Administration of Phenylephrine Versus Dobutamine on Spinal Oxygen Saturation, Measured With Near-infrared Spectroscopy (NIRS).

"Phenylephrine will be administered continuously after intubation in order to maintain blood pressure in a range from MAPbaseline -20% to normal (preoperative) values (MAPbaseline). If MAP decreases to a value lower than MAPbaseline -20%, a higher dose of vasopressor will be administered. If MAP increases to a value above MAPbaseline, the dosing rate will be decreased.~Phenylephrine will be started at 0,2 μg/kg/min and adjusted according to the patient's hemodynamic status. The dose will be adjusted to MAP during a 30-minute study period."

"Dobutamine will be administered continuously after intubation in order to maintain blood pressure in a range from MAPbaseline -20% to normal (preoperative) values (MAPbaseline). If MAP decreases to a value lower than MAPbaseline -20%, a higher dose of vasopressor will be administered. If MAP increases to a value above MAPbaseline, the dosing rate will be decreased.~Dobutamine will be started at 2 μg/kg/min; and adjusted according to the patient's hemodynamic status .The dose will be adjusted to MAP during a 30-minute study period."