the therapeutic role of vasopressin on improving lactate clearance during and after vasogenic shock: microcirculation, is it the black box?

arginine vasopressin as a supplementary vasopressor in septic shock restores vascular tone and mean arterial pressure, meanwhile decreases dose and exposure time to catecholamines. the objective of this study was to evaluate the effect of vasopressin on lactate and lactate clearance as markers of tissue perfusion during septic shock. in this prospective, randomized, controlled trial, 30 patients with septic shock were enrolled in two groups. one group received norepinephrine infusion (titrated to reach the target map of ≥65 mm hg) and the other group in addition to norepinephrine, received vasopressin at a constant rate of 0.03 u/min. serum lactate levels were assessed at baseline, 24 and 48 hours after randomization. lactate clearance was estimated for each patient at 24 and 48 hours. venous lactate was measured in both groups. despite a tendency toward higher venous lactate at 24 and 48 hours in the norepinephrine group (3.1 vs. 2.5, p =0.67 and 1.7 vs. 1.1, p =0.47), the conflict was not statistically significant among them. while lactate clearance after 24 hours was significantly higher in vasopressin treatment group (46% vs. 20%, respectively; p =0.048), the 48-hour lactate clearance did not differ from statistic viewpoints despite their clinical values (66% vs. 40%, p =0.17). although lactate levels did not significantly differ between treatment groups, lactate clearance at 24 hours was significantly higher in vasopressin group. this may be the effect of vasopressin effect on microcirculation and tissue hypoperfusion or its catecholamine sparing effect.