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The Unintended Consequences of Over-Reducing Cardiopulmonary Bypass Circuit Prime Volume
Benjamin C Sun1, Timothy A Dickinson2, Eric A Tesdahl3
1Minneapolis Heart Institute, Minneapolis, Minnesota.
Insights
Minimizing cardiopulmonary bypass prime volume (PV) below 15% of blood volume does not prevent intraoperative red blood cell (RBC) transfusions. Excessive PV reduction may increase RBC transfusion needs in cardiac surgery.
Area of Science:
- Cardiovascular Surgery
- Transfusion Medicine
- Health Services Research
Background:
- Society of Thoracic Surgeons guidelines advocate minimizing cardiopulmonary bypass (CPB) prime volume (PV) for blood conservation.
- Evidence-based guidelines (Class I, Level A) support PV reduction as a key strategy.
Purpose of the Study:
- To evaluate the effectiveness of restricting CPB PV on intraoperative red blood cell (RBC) transfusion.
- To analyze the relationship between PV and RBC transfusion rates in coronary artery bypass graft (CABG) procedures.
Main Methods:
- Analysis of 47,273 isolated CABG procedures from a multi-institutional registry (April 2012-May 2015).
- Primary outcome: intraoperative transfusion of ≥1 unit RBC; Secondary outcome: intraoperative transfusion of ≥4 units RBC.
- Multivariable logistic regression and restricted cubic splines used to model the nonlinear effect of PV on transfusion odds, controlling for 13 confounders.
Main Results:
- A statistically significant nonlinear relationship was observed between PV and the odds of both ≥1 unit RBC (χ² = 116.3, p < 0.001) and ≥4 units RBC (χ² = 25.9, p < 0.001) transfusion.
- The lowest probability of transfusion (≥1 unit RBC) was estimated at a PV to estimated blood volume ratio of 0.152 (15.2%).
Conclusions:
- Minimizing PV below 15% of estimated blood volume does not prevent intraoperative RBC transfusions and may increase transfusion exposure.
- PV management impacts patient morbidity and economic aspects of blood utilization.
- Further research is warranted to fully understand the effect of PV on blood transfusion practices.
Background:
The Society of Thoracic Surgeon blood conservation guidelines recommend minimizing cardiopulmonary bypass circuit prime volume (PV) as an integral, evidence-based (Class I, Level A) blood conservation strategy. We used a large, multiinstitutional registry to evaluate the effectiveness of restricting cardiopulmonary bypass PV on intraoperative red blood cell (RBC) transfusion.
Methods:
We reviewed 47,273 isolated coronary artery bypass graft procedures performed among 189 institutions between April 2012 and May 2015. The primary outcome was intraoperative transfusion of at least 1 unit RBC; the secondary outcome was intraoperative transfusion of 4 or more units RBC. We estimated the adjusted odds of each transfusion type using separate multivariable logistic regression models that controlled for 13 confounding factors. The effect of PV on odds of transfusion was modeled using restricted cubic splines to assess possible nonlinearity.
Results:
We found a statistically significant nonlinear pattern in the relation between PV and odds of transfusion of both 1 or more units RBC (χ2 = 116.3, df = 4, p < 0.001) and 4 or more units RBC (χ2 = 25.9, df = 4, p < 0.001). The lowest probability of transfusion of 1 or more units RBC was estimated at a ratio of PV to estimated blood volume of 0.152 (p < 0.001).
Conclusions:
Efforts to minimize PV below 15% of a patient's estimated blood volume do not protect patients from intraoperative RBC transfusion, and may increase exposure. Prime volume can affect both patient morbidity and the economic impact associated with blood utilization. Further studies on the effect of PV on blood transfusion are warranted.
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