Résumé : The vasopressor effect of arginine vasopressin, a mixed V1a/V2 receptor (V1aR/V2R) agonist, is mediated through the V1aR. Because V2R stimulation may aggravate sepsis-induced vasodilation, fluid accumulation, and microvascular thrombosis, a higher V1aR vs. V2R selectivity might be advantageous. The objective of this study was to elucidate the effects of a first-line therapy with the selective V1aR agonist Phe2-Orn8-Vasotocin vs. arginine vasopressin or norepinephrine on cardiopulmonary hemodynamics and organ function in ovine septic shock.