How are donor lungs preserved prior to transplantation?

Updated: Aug 19, 2019
  • Author: Bryan A Whitson, MD, PhD; Chief Editor: Mary C Mancini, MD, PhD, MMM  more...
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Answer

With current techniques, satisfactory graft function can be obtained after an ischemic interval of as long as 6-8 hours. Ischemic injury to the pulmonary vascular endothelium increases permeability and results in pulmonary edema.

Hypothermic flush perfusion is the method used most commonly for pulmonary preservation in clinical practice. After systemic heparinization of the donor, the pulmonary vasculature is flushed with a cold solution. Commonly used solutions are modified Euro-Collins solution, University of Wisconsin solution, and Perfadex. These are delivered via a large pulmonary artery cannula at a volume of 50-60 mL/kg over 4-5 minutes. Most flush solutions are administered at a temperature of 4°C, while topical cooling is carried out by filling the pleural cavity with iced crystalloid solution. The harvested lungs are immersed in crystalloid solution, packed in ice, and transported at a temperature of 1-4°C. The infusion and transport is performed during active ventilation and static inflation with O2 respectively.

Ex vivo lung reconditioning can increase lung donor availability by permitting the use of marginal donor lungs that were initially deemed unsuitable for transplantation because of inadequate arterial oxygen pressure. [37] For reconditioning, donor lungs are removed along with the heart and undergo ex vivo lung perfusion (EVLP) in an extracorporeal membrane oxygenation circuit. The lungs are gradually and gently rewarmed, reperfused, and ventilated, which reduces edema and atelectasis and allows full inspection and assessment. [37, 38]

Two protocols for EVLP have been developed: Lund and Toronto. The Lund model utilizes a priming/perfusion solution specifically designed for EVLP, such as the Steen solution, which was developed by Swedish surgeon Stig Steen. [37] It is a buffered extracellular solution that includes human albumin to provide an optimal colloid osmotic pressure.The EVLP procedure is performed with a mixture of Steen solution and washed erythrocytes in order to reach a hematocrit of 15%, and the left atrium is kept open, providing the possibility of a normal cardiac output (5-6 L/min) during EVLP. In the Toronto protocol, the EVLP procedure is carried out with an acellular Steen solution and a closed left atrium. [38]

In a 10-year follow-up study, researchers from Lund University reported no difference in long-term survival or pulmonary function between 15 patients who received conventional double-lung transplantations and six patients who received initially rejected donor lungs that had been reconditioned using EVLP. Rates of freedom from chronic lung allograft dysfunction (CLAD) were likewise comparable. [39]

In April 2019 the US Food & Drug Administration (FDA) approved the XVIVO Perfusion System (XPS™) with STEEN Solution™ Perfusate (XVIVO Perfusion, Inc, Englewood, CO) for use on previously unaccepted donor lungs that will be transplanted into a patient with end-stage lung disease.  Donor lungs can remain in the machine for up to 5 hours, for reconditioning and assessment. [40]


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