Systemic Inflammatory Response and Potential Prognostic Implications After Out-of-Hospital Cardiac Arrest: A Substudy of the Target Temperature Management Trial

Objectives: Whole-body ischemia during out-of-hospital cardiac arrest triggers immediate activation of inflammatory systems leading to a sepsis-like syndrome. The aim was to investigate the association between level of systemic inflammation and mortality in survivors after out-of-hospital cardiac arrest treated with targeted temperature management. Design: Post hoc analysis. Setting: Single-center study of a prospective multicenter randomized study. Patients: One hundred sixty-nine patients (99%) with available blood samples out of 171 patients included in the Target Temperature Management trial, randomly assigning patients to targeted temperature management at 33 degrees C or 36 degrees C. Intervention: None. Measurements and Main Results: At baseline and 24, 48, and 72 hours after out-of-hospital cardiac arrest, blood samples were obtained and screened for a battery of inflammatory markers. Level of interleukin-1 beta, interleukin-2, interleukin-4, interleukin-5, interleukin-6, interleukin-9, interleukin-10, interleukin-12, interleukin-13, tumor necrosis factor-alpha, interferon-gamma, C-reactive protein, and procalcitonin were measured. Mortality at 30 days was evaluated by Cox analysis, and the predictive capability of inflammatory markers was evaluated by area under the curve. Level of all inflammatory markers changed significantly within 72 hours after out-of-hospital cardiac arrest (all p values < 0.001), but only procalcitonin levels showed overall differences between non-survivors and survivors (p = 0.0002). At baseline, interleukin-6 was independently associated with mortality, whereas both interleukin-6 levels (hazard ratio = 1.23 [1.01-1.49]; p = 0.04) and procalcitonin levels (hazard ratio = 1.20 [1.03-1.39]; p = 0.02) 24 hours after out-of-hospital cardiac arrest were associated with 30-day mortality with no interactions between targeted temperature management group and levels of interleukin-6 (p = 0.25) or procalcitonin (p = 0.85). None of the other inflammatory markers were independently associated with mortality. Area under the curve for procalcitonin and interleukin-6, 24 hours after out-of-hospital cardiac arrest, were 0.74 and 0.63, respectively. Conclusions: Level of inflammation, assessed by interleukin-6 and procalcitonin, was independently associated with increased mortality with the highest discriminative value obtained 24 hours after out-of-hospital cardiac arrest. Interventions aiming at decreasing level of inflammation as a way to improve outcome may be investigated in future studies.