Interaction Between Fluids and Vasoactive Agents on Mortality in Septic Shock

Objective: Fluids and vasoactive agents are both used to treat septic shock, but little is known about how they interact or the optimal way to administer them. We sought to determine how hospital mortality was influenced by combined use of these two treatments. Design: Retrospective evaluation using multivariable logistic regression to evaluate the association between hospital mortality and categorical variables representing initiation of vasoactive agents and volumes of IV fluids given 0–1, 1–6, and 6–24 hours after onset, including interactions and adjusting for potential confounders. Setting: ICUs of 24 hospitals in 3 countries. Patients: Two thousand eight hundred forty-nine patients who survived more than 24 hours after after onset of septic shock, admitted between 1989 and 2007. Interventions: None. Measurements and Main Results: Fluids and vasoactive agents had strong, interacting associations with mortality (p < 0.0001). Mortality was lowest when vasoactive agents were begun 1–6 hours after onset, with more than 1 L of fluids in the initial hour after shock onset, more than 2.4 L from hours 1–6, and 1.6–3.5 L from 6 to 24 hours. The lowest mortality rates were associated with starting vasoactive agents 1–6 hours after onset. Conclusions: The focus during the first hour of resuscitation for septic shock should be aggressive fluid administration, only thereafter starting vasoactive agents, while continuing aggressive fluid administration. Starting vasoactive agents in the initial hour may be detrimental, and not all of that association is due to less fluids being given with such early initiation of vasoactive agents.