[Catecholamine-resistant hypotension -- an update]

Vasoplegia as catecholamine resistent hypotension occurs in severe hemorrhagic or septic shock and post cardiopulmonary bypass. The entire rational behind this phenomenon is still unclear. An ATP-shortage in the vascular musculature, disregulation of vasopressin release, and the activation of ATP-dependent potassium-channels are discussed. In the last years, attention is drawn towards the activation of ATP-dependent potassium-channels and the possible therapeutic inhibition by glibenclamid. However, inhibition of potassium-channels does not normalize blood pressure under all circumstances. In particular in septic shock other mechanisms have to be involved. Overall, the sometimes desperate clinical situation has led to a large number of case reports und uncontrolled series of retrospectively analysed cases, where vasopressin or methylenblue were discribed as successfully reversing catecholamine resistent hypotension. Nevertheless, in hemorrhagic and septic shock scientific evidence of the clinical effects and the right dose as well as placebo controlled studies comparing the agents and possible combinations of agents are desirable but hardly available yet. In the case of severe hypotension following surgery under cardiopulmonary bypass results of the first randomized and placebo controlled studies describe successful restoration of blood pressure and even a decrease in perioperative mortality. Concerning the side effects, vasopressin and methylenblue, like most vasopressors, can cause gastrointestinal ischemia, but with the small number of patients enrolled so far, further major side effects can not be ruled out. Accordingly, the identification of risk factors for the development of vasoplegia and the prediction of the extent of the response or the rate of non-responders to these treatments are widely unknown. However, although the administration of vasopressin and methylenblue can not be recommended as a standard treatment it provides an additional option in individual cases of life threatening vasoplegia.