Hypothermia after cardiac arrest does not alter serum inflammatory markers*

Objective:Hypothermia improves survival and neurologic recovery after cardiac arrest. Cardiac arrest also triggers release of cytokines and inflammatory molecules, and it is unknown whether therapeutic hypothermia alters this inflammatory response. This study tested whether therapeutic hypothermia altered levels of inflammatory markers in serum. Design:Prospective, randomized study. Setting:University research laboratory. Subjects:Adult, male, Sprague-Dawley rats. Interventions:Halothane-anesthetized rats were subjected to 8 mins of asphyxial cardiac arrest and resuscitation. Rat temperature was controlled at 37°C throughout the experiment (normothermia) or reduced to 33°C between 1 and 24 hrs after cardiac arrest (hypothermia). Serum cytokines were measured at baseline, 0.5, 1, 3, 6, 12, and 24 hrs after resuscitation using multiplex analyzer or enzyme-linked immunosorbent assay. Measurements and Main Results:Hypothermic rats showed improved neurologic recovery at 12 and 24 hrs. Serum levels of tumor necrosis factor-α; macrophage inflammatory protein-1α; growth-related oncogene/keratinocyte chemokine; interleukin-2, -9, and -10; monocyte chemotactic protein-1; leptin; and intracellular adhesion molecule-1 increased over time, and the levels of interleukin-18 declined over time. No temporal trends in other molecules were detected. Levels of these molecules did not differ between temperature groups during the hypothermia phase (1–24 hrs). Conclusions:These data suggest that altering the inflammatory response after cardiac arrest is not necessary for the beneficial effects of hypothermia. These data do not support a specific role of circulating cytokines in the neurologic injury after cardiac arrest.