Organ injury is unfortunately a common adverse effect of cardiopulmonary bypass [CPB]. Therefore, practitioners have been searching for ways to better predict and limit such injuries. One measure that is of current interest is the indexed delivery of oxygen [DO2i], which reflects how much oxygen is being delivered via the arterial blood to the body’s tissues. Various studies have been conducted in an effort to identify the ‘critical’ DO2i level, which is the value at which oxygen demands surpass oxygen delivery, resulting in acidosis. Theoretically, this would establish the DO2i value to target during CPB to prevent organ injury. Studies found that the critical DO2i for acute kidney injury [AKI] is 260 to 280 mL/min/m2 in adults, 340 mL/min/m2 in neonates, and 400 mL/min/m2 in infants. Longer cumulative time and depth below critical DO2i levels were also found to be associated with higher AKI occurrence. The critical DO2i for brain injury was found to be 225 mL/min/m2 in adults. Clinical application of the critical DO2i with goal directed perfusion [GDP] studies found that GDP significantly increases DO2i levels during CPB and reduces AKI rates. Although these studies had significant findings, each study had their own limitations. The controversial credibility of these studies, as well as the disputability of perfusion enhancement strategies, makes it unclear how many perfusionists utilize DO2i in their decision making, and if so, what DO2i value they target during CPB. There were no existing DO2i surveys found during a thorough search utilizing the PubMed search engine. The goal of this project was to utilize a survey to determine if there is a critical DO2i that perfusionists are targeting during CPB and to capture their perceptions of this clinical indicator.
Following approval from the Milwaukee School of Engineering [MSOE] Institutional Review Board [IRB], a survey was created to ascertain the usage and perceptions of DO2i by certified and practicing perfusionists in the United States. Specifically, the survey asked questions regarding participant demographics, DO2i goals during CPB, and what clinical decisions participants make based on DO2i. The survey was dispersed to and forwarded by various perfusion societies and groups.
A total of 222 certified and practicing perfusionists volunteered to participate in the survey. Among the 203 participants that chose to answer the question about how they use DO2i, 73% reported they use DO2i in some capacity during CPB. The DO2i value that perfusionists reported they target during CPB was somewhat comparable to the critical DO2i values identified in the literature review. Survey results showed that adult perfusionists mostly target a DO2i of 276 to 300 mL/min/m2, and the literature identified a critical value of 260 to 280 mL/min/m2 for AKI prevention in adults. Survey results showed that pediatric perfusionists mostly target a DO2i of 276 to 375 mL/min/m2, and the literature identified a slightly higher critical value of 340 to 400 mL/min/m2. Participants also further detailed their DO2i usage, such as lowering their target DO2i or utilizing the DO2i to VO2i ratio during hypothermic CPB cases. Additional input shared by the survey participants affirmed that utilization of DO2i continues to be a topic of controversy in the field of perfusion.
