Factors That Influence the Ability to Perform Autologous Priming

The process of displacing crystalloid prime solution with the patient’s own blood to reduce hemodilution during the onset of cardiopulmonary bypass (CPB), known as autologous priming (AP), is neither new nor novel. A prospective trial by Rosengart et al. (1) at the New York Hospital-Cornell Medical Center brought the technique into contemporary literature and led the way for other investigators (1). The study of Rosengart et al. was limited to first-time coronary artery bypass grafting patients and had a small sample size(n = 60), but established that AP limits hemodilution and reduces the number of patients needing red cell transfusions. Since the report of Rosengart et al., several groups have reported similar results in both randomized and observational trials (2–6), with reported benefits of reduced transfusion requirements and higher CPB hematocrits being consistent. However, one observational study concluded that AP does not offer a clinical benefit as a blood conservation technique. The trial was limited by design (retrospective cohort, single surgeon) and the restrained reporting of AP techniques and volume management strategies prevents replication (7). Given that the majority of reports, including all of the randomized trials, support the use of AP, the technique should be considered a standard blood conservation strategy during CPB. Reducing transfusion use and exposure is a well-understood goal, but the importance of maintaining higher hematocrits during CPB is becoming more apparent. Several groups have reported that lower nadir hematocrit on CPB is exponentially associated with poor outcome. In a very large series of patients(n = 3800), Habib et al. (8) found that increased hemodilution during cardiac surgery (Hct = 22%–24%) was associated with higher incidences of perioperative organ dysfunction, increased resource use, and higher mortality (8). In a similar large, multicenter series(n = 6980), the Northern New England Study Group found that lower CPB hematocrits were significantly associated with increased post-CPB mechanical support and increased mortality (9). It is clear from these studies and others that the avoidance of anemia and avoiding transfusion triggers during CPB is critical, and AP is an effective method for supporting this goal. Although AP techniques are known to reduce CPB volume balance, reduce transfusion of homologous red blood cells, and maintain higher hematocrits, most studies have compared AP vs. no AP in defined, limited patient populations. Therefore, it is not clear what level of AP is needed to achieve benefit or what impacts the ability to perform this procedure. The purpose of this study was to evaluate different levels of effective AP on hematocrit and transfusion requirements. A second goal was to identify any demographic or operative parameters that may influence the effectiveness of AP.