 Thirty two septic shock patients requiring vasopressor support to maintain mean arterial pressure between 65 and 75 mmHg despite adequate volume resuscitation will be enrolled in the study. Patients will be randomly allocated to be treated with either a titrated phenylephrine, b titrated norepinephrine control; each n 16, to achieve a mean arterial pressure MAP between 65 and 75 mmHg, if necessary. Data from right heart catheterization, thermo-dye dilution catheter, gastric tonometry as well as data from organ function, will be obtained at baseline and after 12 hours. 