A Sub-Study of the Target Temperature Management Trial
BACKGROUND: Cardiovascular dysfunction is common after out-of-hospital cardiac arrest as part of the postcardiac arrest syndrome, and hypothermia may pose additional impact on hemodynamics. The aim was to investigate systemic vascular resistance index (SVRI), cardiac index, and myocardial performance at a targeted temperature management of 33°C (TTM33) versus 36°C (TTM36). METHODS AND RESULTS: Single-center substudy of 171 patients included in the Target Temperature Management Trial (TTM Trial) randomly assigned to TTM33 or TTM36 for 24 hours after out-of-hospital cardiac arrest. Mean arterial pressure ≥65 mm Hg and central venous pressure of 10 to 15 mm Hg were hemodynamic treatment goals. Hemodynamic evaluation was performed by serial right heart catheterization and transthoracic echocardiography. Primary end point was SVRI after 24 hours of cooling and secondary end points included mean SVRI, cardiac index, systolic function, and lactate levels. The TTM33 group had a significant increase in SVRI compared with TTM36 (2595; 95% confidence interval, 2422-2767) versus 1960 (95% confidence interval, 1787-2134) dynes m(2)/s per cm(5); P<0.0001, respectively) after 24 hours of cooling with an overall difference of 556 dynes m(2)/s per cm(5) (P(group) <0.0001). TTM33 was associated with decreased cardiac index (-0.4 L/min per m(2); P(group) <0.0001), decreased heart rate (P(group)=0.01), and stroke volume index (P(group)=0.004) compared with TTM36. Left ventricular ejection fraction (P=0.39) and peak systolic myocardial velocity (P=0.62) did not differ between TTM groups. Lactate levels were significantly higher in the TTM33 group (P=0.0008). CONCLUSIONS: Targeted temperature management at 33°C with target mean arterial pressure ≥65 mm Hg is associated with increased SVRI and lower cardiac index because of lower heart rate with unaffected left ventricular systolic function compared with 36°C. CLINICAL TRIAL REGISTRATION URL: http://www.clinicaltrials.gov. Unique identifier: NCT01020916.