Arginine vasopressin (AVP) is increasingly used in the therapy of septic patients with hypotension [1]. In a prospective, controlled laboratory experiment we studied AVP-associated changes in the villus microcirculation of the septic rat ileum.

Twenty-four hours after caecal ligation and perforation to create sepsis, moderately hypotensive rats (average decrease in mean arterial pressure [MAP] 20% from pre-septic values) were anaesthetized. Next, intravital video-microscopy was performed on 6-10 villi of ileum mucosa (M₀). The treatment group then received a continuous infusion of AVP to increase MAP by 20 mmHg (M₁) and 40 mmHg (M₂) from M₀, while the control group received only normal saline. Measurements were repeated at M₁ and M₂. Video recordings were analysed by a blinded investigator. Diameter of terminal arterioles (Art_d) were determined and stopped flow across the villus microcirculation (total arrest of villus blood flow > 1 s) was quantified.

ANOVA with post-hoc test (Student-Newman-Keuls). Data are mean ± SD.

These preliminary data demonstrate severe abnormalities in gut mucosal blood flow following AVP infusion in septic rats. Because no change occurred in terminal arteriolar diameters, the observed flow abnormalities could be due to either activities of AVP on larger arterioles or to a concomitant reduction in cardiac output [1].