5230Association of cardiac output during targeted temperature management with mortality after out-of-hospital cardiac arrest

Abstract Purpose Myocardial dysfunction and low cardiac output are common after out-of-hospital cardiac arrest (OHCA) as part of the post-cardiac arrest syndrome. This study investigates the association of cardiac output during targeted temperature management (TTM) with mortality. We hypothesized that low cardiac output during TTM is associated with mortality. Methods In the TTM-trial, which randomly allocated patients to TTM of 33°C or 36°C for 24 hours, we prospectively and consecutively monitored 171 patients with protocolized measurements from pulmonary artery catheters (PAC). Clinical and hemodynamic variables were registered at pre-specified time points in addition to 30-day survival status. Lactate, heart rate and cardiac index were measured at 3 time-points during TTM and averaged. We defined low cardiac output as a cardiac index during TTM <2.4 l/min/m2 in the TTM36-group and <1.8 l/min/m2 in the TTM33-group, since hypothermia affects cardiac output. We further stratified patients according to serum lactate (above/below 2 mmol/L) and heart rate (above/below median, which was 65 beats/min.). Results Of 152 patients with available hemodynamic measurements, 71 (47%) had low cardiac output during TTM (TTM33: 38 (49%), TTM36: 33 (44%)). Low cardiac output was not associated with mortality in univariate analysis (hazard ratio (HR): 1.47 [0.83–2.59], p=0.19) or multivariate analysis adjusted for potential confounders (HRadjusted: 0.74 [0.38–1.44], p=0.37). Low cardiac output combined with HR>65 was associated with increased mortality (HR: 2.69 [1.51–4.79], p=0.0007) in univariate, but not in multivariate analysis (p=0.22) (Figure). Low cardiac output and HR<65 was associated with decreased mortality in multivariate analysis (HRadjusted: 0.36 [0.14–0.93], p=0.03). Low cardiac output and lactate>2mmol/L was associated with increased mortality (HR: 2.73 [1.49–4.99], p=0.001) in univariate, but not in multivariate analysis (p=0.53), whereas patients with low cardiac output and lactate<2mmol/L had low mortality (HRadjusted: 0.58 [0.27–1.24], p=0.16) compared to the rest of the population (Figure). Figure 1 Conclusion This study found, that a frequent symptom during TTM is low cardiac output, which was not associated with mortality. However, patients with low cardiac output combined with either increased lactate or heart rate seems to be a population at risk. Whether low cardiac output should be corrected by inotropes or mechanical support to reduce mortality remains to be studied in prospective trials, but the efficacy of goal-directed therapy to increase cardiac output during TTM may be modest, especially if lactate and heart rate are normal. Acknowledgement/Funding The research fund Gangstedfonden and the Research fund of Rigshospitalet has supported this study with unrestricted salary in Dr. Grand's PhD project.