LAUSR

Learning Objectives: There is an increasing appreciation of the fact that the immune system can evolve into several states different from healthy or sick. Consequently, the definition of recovery from a serious stressful event (sepsis, surgery, others) is being challenged. While inflammation is expected in the hours and days following an adverse event, few studies examine inflammation in the long-term. This study seeks to assess the effect of cardiac surgery as an insult to the immune system. We are specifically looking at how the immune system behaves at the time of discharge from the hospital as compared to presurgical levels. Methods: This is a longitudinal observation study of the individuals scheduled for non-emergent cardiac surgery as the model of trauma. A total of 39 patients have been recruited to the study. Blood was collected at three time points: 0hr (baseline), 24hr (following surgery) and 7d post-surgery. At each time point, whole blood stimulation was performed with an unstimulated sample and three stimulations per patient, reagents being H3N2 [0.5mg/ mL], Flublok (FB) [0.2 mcg/mL], and LPS [100ng/mL]. Serum was collected after an 18-hour incubation period, and ELISA assays were performed to measure IL-6 and TNFα as indicators of inflammation. Results: We show a significant decrease (84%) between the baseline and 24hr TNFα concentrations for the LPS samples ([TNFα 0hr,LPS ]=515.88 ± 1276.12pg/mL, [TNFα 24hr,LPS ]=82.18 ± 279.38pg/mL, n=39, p=0.0415). Also significant is the increase in IL-6 concentration between baseline and 7d samples for both FB ([IL-6 0hr,FB ]=467.2 ± 1325.25pg/ mL, [IL-6 7d,FB ]=2365.34 ± 2517.76pg/mL, n=35, p=1.90x10-4) and LPS ([IL-6 0hr,LPS ]=1577.89 ± 2075.85pg/mL, [IL6 7d,LPS ]=5536.54 ± 2329.22pg/mL, n=32, p=1.06x10-9). Conclusions: We demonstrated significant suppression of inflammatory response shortly after surgery followed by increased responses at the time of discharge while cells were stimulated with LPS or FB. This early suppression of responses suggests that cardiac surgery results in much quicker evolution of inflammatory response than we previously thought.