Circulating vasopressin levels in septic shock

Objective: To assess the frequency of vasopressin deficiency in septic shock. Design: Prospective cohort study. Setting. Intensive care unit at Raymond Poincare University Hospital. Patients. A cohort of 44 patients who met the usual criteria for septic shock for <7 days. A second cohort of 18 septic shock patients were enrolled within the first 8 hrs of disease onset. Interventions: None. Measurements and Main Results: General demographics, severity scores, vital signs, standard biochemical data, and circulating vasopressin levels were systematically obtained at baseline in the two cohorts. Vasopressin deficiency was defined by a normal plasma vasopressin level in the presence of a systolic blood pressure of <100 mm Hg or in the presence of hypernatremia. Baroreflex sensitivity was systematically evaluated in patients of the first cohort when vasopressin deficiency was noted. In the second cohort of patients, plasma levels of vasopressin were obtained at baseline, 6, 24, 48, and 96 hrs after shock onset. In the first population, plasma vasopressin levels were inversely correlated to the delay from shock onset. Fourteen patients had relative vasopressin deficiency: 12 patients had systolic blood pressure <100 mm Hg, with impaired baroreflex sensitivity in four, and three patients had hypernatremia. In the second population, only two patients had relative vasopressin deficiency. The plasma levels of vasopressin significantly decreased over time (p < 10(-3)). Conclusions: Plasma vasopressin levels are almost always increased at the initial phase of septic shock and decrease afterward. Relative vasopressin deficiency is seen in approximately one-third of late septic shock patients.