Cardiac surgery with cardiopulmonary bypass is associated with systemic inflammatory response. In some cases this clinical condition is characterized by severe hypotension due to low systemic vascular resistance during and after cardiopulmonary bypass. Afew ofthese cases do not respond to volume or catecholamines. This condition is known as vasoplegic syndrome. Its etiology is notfully understood today and carries associated morbidity and mortality In this syndrome, vasopressin levéis are reduced, as in septic and hypovolemic shock. Supplementary vasopressin improves blood pressure and might be considered as an alternative treatment. Severa! reports have shown benefits when used alone or in combination with catecholamines. However, further studies are necessary to find the most appropriate use ofthe drug for vasoplegic syndrome.