1. A method of increasing blood pressure to a target blood pressure in a human patient with post-cardiotomy shock wherein the patient has an LNPEP AA or AT rs4869317 genotype, the method comprising: intravenously administering to the patient a pharmaceutical formulation comprising vasopressin at a starting dose of 0.03 units/minute and titrating the dose up by 0.005 units/minute at 10 to 15 minute intervals to maintain the target blood pressure, wherein the maximum dose is 0.121 units/minute.