Vasopressin in vasodilatory shock: hemodynamic stabilization at the cost of the liver and the kidney?

Infusing arginine vasopressin (AVP) in advanced vasodilatory shock is usually accompanied by a decrease in cardiac index and systemic oxygen transport. Whether or not such a vasoconstriction impedes regional blood flow and thus visceral organ function, even when low AVP is used, is still a matter of debate. Krejci and colleagues now report, in this issue of Critical Care, that infusing 'low-dose' AVP during early, short-term, normotensive and normodynamic fecal peritonitis-induced porcine septicemia markedly reduced both renal and portal blood flow, and consequently total hepatic blood flow, whereas hepatic arterial flow was not affected. This macrocirculatory response was concomitant with reduced kidney microcirculatory perfusion, whereas liver micro-circulation remained unchanged. From these findings the authors conclude that the use of AVP to treat hypotension should be cautioned against in patients with septic shock. Undoubtedly, given its powerful vasoconstrictor properties, which are not accompanied by positive inotropic qualities (in contrast with most of the equally potent standard care 'competitors', namely catecholamines), the safety of AVP is still a matter of concern. Nevertheless, the findings reported by Krejci and colleagues need to be discussed in the context of the model design, the timing and dosing of AVP as well as the complex interaction between visceral organ perfusion and function.