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Presenter: Benjamin, Bryner, Ann Arbor, United States
Authors: Alvaro Rojas-Peña, Benjamin Bryner, Yao Nie, Cory Toomasian, Robert Bartlett, Martin Bocks, Gabe Owens
Prolonged Ex-situ Perfusion: Twelve Hours of Heart Perfusion
Alvaro Rojas-Peña1,2, Benjamin Bryner2, Yao Nie2, Cory Toomasian2, Robert Bartlett2, Martin Bocks2,3, Gabe Owens2,3
1General Surgery-Section of Transplantation, University of Michigan, Ann Arbor, MI, United States, 2General Surgery-Extracorporel Life Support Laboratory, University of Michigan, Ann Arbor, MI, United States, 3Pediatric and Cardiology, University of Michigan Congenital Heart Center, Ann Arbor, MI, United States
Background: Ex situ organ perfusion can extend time before transplant, expand the donor pool, and allow for optimization of donor organs.
Methods: Forty-kilogram swine are used as heart and blood donors. The swine’s blood is centrifuged, and perfusate is created by reconstituting erythrocytes and plasma (leukocytes are discarded) with a target hemoglobin of 3-4 mg/dL. The perfusion circuit includes a membrane oxygenator, heat exchanger, collapsible rotary pump, pressure-release valve, and bubble trap (figure 1). Perfusate enters the aortic root at a goal pressure of 50-55mmHg, and drains passively into the reservoir. Once the heart is rewarmed, it is defibrillated to restore sinus rhythm, but is not continually paced. A portion of the perfusate is exchanged hourly to dilute out metabolic byproducts. A sampling catheter is placed in the coronary sinus, and EKG leads are placed in the myocardium. Perfusion pressure, flow, temperature, and blood gas measurements are monitored. Experiments were ended when resistance rose above a critical threshold, or at 12 hours.
Results: We perfused nine hearts ex situ at body temperature (37-39°C) and two at room temperature. Initial pathology results showed patchy hemorrhage within the myocardium, prompting us to decrease the target perfusion pressure in later experiments from 65mmHg to 55mmHg. The room-temperature hearts were perfused for 7 and 8.5 hours; the normothermic hearts for 9-12 hours. Normothermia was necessary for hearts to regain sinus rhythm (fig 2); this did not occur at lower temperatures despite defibrillation. Despite regular changes of perfusate, lactate increased significantly by the end of the perfusion in most experiments. Mean weight gain was 17% over the course of perfusion.
Conclusion: Perfusion of a swine heart for 12 hours with maintenance of sinus rhythm is feasible
Figure 1
Figure 2
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