Non-Encapsulated Heme Levels in Adult Cardiac Surgery

Non-encapsulated (free) heme, a breakdown component of hemoglobin, is associated with oxidative stress and inflammation with consequent cellular and tissue injury (Ryter & Tyrrell, 2000) (D T G Wagener, et al., 2001). Cardiopulmonary bypass is known to cause trauma to cellular components of the blood, to trigger an inflammatory response, and alter the rheology of the circulation. Prior research has demonstrated an increase in levels of free heme with cardiopulmonary bypass (Wetz, Richardt, Schotola, Bauer, & Bräuer, 2017) (Kubota, Egi, & Mizobuchi, 2017). The stress response to cardiac surgery and utilization of blood salvage techniques independent of cardiopulmonary bypass may affect plasma free heme levels as well as regulation of heme metabolism pathways. It is unclear whether and to what degree plasma levels of free heme may vary at discreet time points in the perioperative period during cardiac surgery involving both cardiopulmonary bypass and "off-pump" techniques.

This is an observational, prospective cohort study in which we will assess for red blood cell trauma, free heme levels, and biomarkers for acute kidney injury at various time points throughout cardiac surgery. Urine and arterial blood samples will be collected at our routine, standard of care time points pre-, intra-, and post-operatively and in addition to the standard clinical tests that will be performed (arterial blood gas analysis and activated clotting time) several additional serum biomarkers will be analyzed. Clinical correlation will be performed with levels. Sub-analysis will be performed on the basis of off vs. on pump CABG cases and also in patient that do/not develop AKI post-operatively.