TSRA Content:
Author: Cynthia L. Miller, MD
This is a revision and update from the previous edition of the TSRA Primer in Cardiothoracic Surgery written by Bryan Whitson, MD, PhD
Logistics of the Procurement
Prior to leaving for the procurement, discuss with the coordinator and the implanting surgeon to identify any concerns. Clarify whether the procurement will be from a donation after brain death (DBD) or donation after circulatory death (DCD) donor, and the lung preservation strategy that will be used (conventional cold static storage vs ex vivo lung perfusion (EVLP)). DCD donation involves additional logistics discussed in the “DCD Procurement” section. Make sure to have a concrete sense of the travel arrangements (where you are going, what hospital, how you are traveling, plane tail number, pilot cell phone number). In addition, know who the surgical recovery coordinator on site is and their phone number. Know the blood type of the recipient, the donor, and the UNOS identification number. Clear knowledge of any particular anatomic or recipient issues is key.
When on site, review the general donor checklist (consent for donation, verification of brain death if DBD donor, ABO blood type compatibility with recipient, donor serologies/virology, appropriate supplies, any new data related to donor history). Examine the donor history and physical to confirm that there is no significant pulmonary disease, minimal (<20 pack year ideally) smoking history, donor PaO2:FiO2 >400 (with FiO2 100% and PEEP 5-8 cm H2O), and age <55 years. In addition, review chest imaging (for presence of infiltrate), bronchoscopy findings (secretions, etc.), virology and sputum/blood culture results.
There are typically several points of communication that should occur with the implanting transplant center/surgeon, many of which apply to both DBD and DCD procurement. The first is on arrival at the donor hospital. For DBD procurement, the next is when the donor arrives in the OR and then upon completion of donor lung examination/visualization; make sure to relay the condition of the lungs, any anatomic abnormalities or adhesions, and bronchoscopy findings (including mucosal erythema). For a DCD procurement, there are additional aspects of the timeline that will be necessary to relay to the implanting surgeon and are described in the “DCD Procurement” section. For DBD procurement, the subsequent points of communication are: estimated time of donor heparin administration (prior to aortic cross-clamp), when all teams are ready to administer heparin, and when ready to cross-clamp the aorta. For DBD and DCD procurements, you should inform the implanting surgeon when you are leaving the donor hospital (and relay any procurement issues), the estimated time of arrival at the transplant center, and when you are approximately 15 minutes away.
DBD Procurement
Prior to beginning the procurement, perform a flexible bronchoscopy to visualize the anatomy, tracheal mucosa, and secretions. Discuss with the anesthesia team the need to minimize administration of fluid volume and the importance of a lung-protective ventilation strategy (tidal volumes of 6-8 ml/kg). Ask that vasopressors be used if necessary. Keep the central venous pressure <10 mmHg. If there is a heart procurement team, the sites of left and right heart venting, division of the left atrial cuff, and cannulation/division of the main pulmonary artery (PA) should be discussed in advance (and agreed upon by both teams during the procurement).
1. Visualization and Preliminary Dissection:
Perform a generous median sternotomy in the standard fashion; extension of the incision cephalad to the thyroid cartilage helps expose the head vessels and trachea. Open and "T" the pericardium. Retract the pericardium using 3 stay sutures on each side, with tags to allow for lung evaluation. Make sure to communicate with the anesthesia team during the dissection so that any manipulation of the heart or great vessels may be anticipated, and the blood pressure can be optimally managed.
After the heart team has visualized the heart, hold ventilation and open each pleura widely from the apex to the diaphragm. Resume ventilation and evaluate the lungs for edema, consolidation, atelectasis, contusion, bullae, masses, adhesions, or injury. Ask anesthesia to recruit atelectatic segments using a sustained inflation pressure of 30 cm H2O, and then perform a compliance check by asking them to disconnect the ventilator at the end of inspiration to evaluate for prompt deflation of the lungs.
Preliminary dissection should proceed while the abdominal team is working, with the goal of isolating all key structures to facilitate prompt explant. This includes 1) circumferential dissection of the SVC to separate it from the right PA, 2) circumferential dissection of the IVC, 3) mobilization/ separation of the aorta from the main PA to allow for cross-clamp application (+/- encirclement of the aorta with an umbilical tape), 4) wide opening of the pleura, 5) division of the pulmonary ligaments (if accessible), and 6) mobilization/dissection of the trachea lying posteriorly between the proximal aorta and the SVC. During this dissection, the SVC can be isolated with a heavy silk tie cephalad to the azygos vein and secured with a loosely applied Rommel tourniquet. The azygos vein may be ligated approximately 0.5 cm away from its takeoff of the SVC. Gentle retraction of the SVC and the aorta facilitates opening of the posterior pericardium above the right PA for access to the trachea. The plane around the trachea should be further developed using finger dissection. Carefully dissect the interatrial groove with input from the heart team to ensure adequate atrial cuff for both teams.
2. Cannulation and Explant:
Set up the sterile pressure tubing and the perfusate. Typically, 4 L of low potassium, dextran-rich pulmonary preservation solution (Perfadex®) is used; 3 L for the antegrade flush and 1 L for the retrograde flush. Place a 4-0 Prolene purse string into the main PA 1.5 cm proximal to its bifurcation (at a location agreed upon with the heart team, to ensure the cannula is not placed too close to the pulmonary valve sinuses). After confirming cross-clamp time with the other teams and the implanting transplant center, systemically heparinize with 400 U/kg. Cannulate the main PA using a PA vent or infusion catheter with the cannula tip pointing toward the pulmonary valve and secure in place with a Rommel tourniquet; place a bumper or heavy tie on the cannula at 1.5 cm to prevent deeper migration of the cannula into the distal PA. Once the cannula is secured, de-air and connect the lines to the cannula. Inject prostaglandin E (500 mcg) into the main PA just distal to the cannula and allow it to circulate for 1 minute; this may cause systemic blood pressure to drop.
Next, ligate the SVC (cinch the silk tie using the Rommel tourniquet) and partially transect the IVC. A pool-tip sucker should then be placed into the IVC to drain the abdominal perfusate. Vent the left side of the heart by opening/excising the left atrial appendage or by making an incision in the interatrial groove. Alternatively, the heart can be vented through a large incision in the left atrial wall anterior and medial to the left pulmonary veins; this approach requires exposure of the coronary sinus by reflecting the apex of the heart anteriorly, medially, and superiorly. Place the aortic cross-clamp across the proximal aortic arch. Start antegrade pulmonary perfusion via gravity into the PA catheter once the heart has arrested. See "Heart Procurement" chapter for heart procurement logistics. Once the aortic cross-clamp is applied, place copious amounts of ice slush into both pleural spaces for topical cooling of the lungs by moving the tagged pericardial retention sutures. Venting the warm blood and dropping the temperature is key. Make sure that the anesthesia team continues gentle ventilation (decrease tidal volumes to 250-300 mL but keep PEEP on) to prevent atelectasis and homogeneously distribute the perfusate. Positioning of the PA catheter should be checked intermittently during this time to ensure equal flow to both lungs, which should blanch equally with infusion of the perfusate. Antegrade pulmonary perfusion is continued until the effluent from the left atrium becomes clear.
After completion of the 3 L antegrade pulmonary flush, remove the PA cannula. Completely free the IVC posteriorly and dissect up to the level of the right atrium, taking care not to injure the right inferior pulmonary vein. Work with the heart team to open the interatrial groove into the left atrium at the previously made dissection point. With the apex of the heart elevated, extend the incision in a plane parallel to the AV groove toward the base of the left atrial appendage on the left and the inferior edge of the IVC on the right. Complete the left atrial incision from inside the left atrium; all four pulmonary vein orifices should be visible with a rim of residual left atrial muscle around each. Transect the SVC and divide the aortic arch vessels and the main PA at the level of the PA cannula.
With the heart removed, if one decides to do the retrograde pulmonary flush in-situ, perform now. Using a soft catheter, infuse ~250 mL of Perfadex (total 1 L) into each pulmonary vein. Watch for clot and then clearing return in the PA to make sure that the flush is adequate; when the effluent from the PA is clear, the donor lungs are ready for explant.
Next, incise the posterior aspect of the pericardium from lateral to medial on both sides. Externalize the right lung out of the chest and incise the pulmonary ligament (if not already done); vertically incise the mediastinal pleura lateral to the esophagus, transect the azygos vein (if not already done), and extend the plane of dissection cephalad to obtain circumferential control of the trachea. Return the right lung to the chest. Next, reflect the left lung out of the chest and incise the pulmonary ligament (if not already done). Incise the mediastinal pleura along the esophagus and continue working cephalad. Finish releasing all connections to the anterior wall of the esophagus, dissecting in the areolar tissue anterior to the esophagus. Return the left lung to the chest.
Inflate the lungs to remove atelectasis and hold at a static pressure of 12-15 cm H2O. A double staple line is applied to the trachea distal to the endotracheal tube and proximal to the carina, using two 3.5 mm loads of the TA stapler. Transect the trachea between the two loads. Lyse any remaining bands or tissues. Remove the lungs and place on the back table.
3. Packaging:
If the retrograde flush was not performed in-situ, perform it on the back table. If the lung is to be split on-site, discuss the arrangement with the other lung team as to who gets the carina; this typically will go with the right lung. In this setting, the lungs are separated by dividing the left atrium between the pulmonary veins and the main PA at the bifurcation. The proximal left mainstem bronchus is divided between a double staple line of two 3.5-mm loads of the TA stapler. After inspection for surgical damage, persistent atelectasis, or areas of inadequate flush, place each lung into a separate, appropriately labeled sterile bag containing 1 L of Perfadex solution at 4°C. Purge any air from the bag prior to sealing it. Place the first bag into a second bag containing ~250-500 mL of saline slush and seal. Place this bag into a third bag containing saline slush, seal this tightly, and place into a cooler containing crushed ice. Of note, some transplant centers prefer that the lungs are returned en-bloc for a double lung transplant. Seal the cooler and ensure that it is labeled with the appropriate information. Obtain your copy of the donor and UNOS paperwork. Sign the organ procurement organization's operative report. Make sure you have the correct organ and you're off!
DCD Procurement
Additional logistics are involved in a DCD procurement and include a pre-withdrawal meeting at the donor institution (with representatives from the anesthesia, transplant surgery, and critical care teams, as well as OR and ICU nursing staff). During this meeting, the patient’s history and informed consent are reviewed, and procurement roles are assigned. A time for withdrawal of life-sustaining therapy (WLST) is determined based on the wishes of the family, and involves NG tube aspiration, cessation of inotropic drugs, and extubation. This may occur in the ICU or the OR, and the timing should be communicated to the implanting surgeon/transplant center. If allowed by the donor center, have 30,000 units of heparin administered 3-5 minutes prior to WLST. Death is defined as asystole (lack of pulsatility on the arterial line with or without electrical cardiac activity); the time at which asystole occurs should also be communicated to the implanting surgeon/center. There is a “stand-off” period of 2-5 minutes between asystole and declaration of death to exclude spontaneous return of circulation. The donor is then quickly brought to the OR (if not already there), reintubated, and a single breath is administered to confirm the presence of end tidal CO2. Further ventilation is held until cold perfusion of the heart/ lungs or aortic cross-clamp to avoid the possibility of auto-resuscitation/ cerebral reperfusion. Bronchoscopy is performed after re-intubation and can be done while the chest is being opened. According to the ISHLT registry, the median time from WLST to death (agonal phase) is 15 minutes and from WLST to cold perfusion (warm ischemic time) is 30 minutes1. The allowable duration of the agonal phase or warm ischemic time is unknown but may be up to or greater than 60 minutes2.
Unlike brain death procurements, DCD procurements require expediency for rapid cannulation and initiation of cold perfusion to minimize the duration of warm ischemia. Coordination with the anesthesia and other procurement teams is critical, particularly if the heart is also being procured. Exposure is obtained in a similar fashion as with DBD procurement via median sternotomy, after which the pericardium is sharply opened to expose and cannulate the PA as quickly as possible. PA cannulation should proceed with the same technique as in DBD procurement; it may help to place a hemostat on the adventitia of the PA proximal to the cannulation site and provide gentle retraction. After successful cannulation, incise the left atrial appendage to prevent pulmonary edema and initiate cold pulmonary flush (Perfadex at a dose of 50-70 mL/kg). Open both pleura to expose the lungs and quickly inspect for any irregularities. Place ice slush into both pleural cavities for topical cooling. After completing the 3 L of pulmonary flush, remove the lungs using the same technique as described above for DBD procurement.
Ex-Vivo Lung Perfusion (EVLP)
EVLP may be used to evaluate marginal or extended criteria donor lungs, defined as one or more of the following: DCD, PaO2:FiO2 ≤ 300, ischemic time >6 hours, age ≥ 55 years, >20 pack-year smoking history, abnormal chest radiograph, and/ or positive sputum microbiology. There are several commercially available platforms for EVLP, which are either portable (donor lungs are immediately placed on EVLP after procurement) or fixed (donor lungs must be transported to a specialized perfusion center).
To establish EVLP, the lungs are dissected, flushed, and cooled as described above depending on whether the procurement is from a DBD or DCD donor. The EVLP circuit is primed with a perfusate, and the donor lungs are attached to the circuit using custom cannulas. The flow and temperature are gradually increased until 37°C is reached; ventilation is continued in a lung-protective mode. Upon completion of EVLP, perfusion and ventilation are discontinued, and the lungs are cooled back to 4°C for implantation.
If the portable Organ Care System (OCSTM by TransMedics®) protocol is used, the lungs are not divided on the back table and are instead attached to the EVLP platform by cannulating the PA and connecting the airway using the supplied tracheal connector. Other non-portable platforms (XVIVO Perfusion System (XPS)™ by XVIVO® and Vivoline LS1™ by Vivoline Medical®) use the Toronto or Lund protocol: after standard DBD/ DCD procurement, the lungs are transported using static cold storage until arrival at the recipient institution where the lungs are connected to the EVLP circuit3.
Potential Pitfalls
There are a number of structures that may be injured during lung procurement. The pulmonary veins are particularly susceptible to injury; specifically, the right inferior pulmonary vein may be damaged during division of the left atrial cuff or IVC. Venous injury may also result from excessive dissection of the inferior pulmonary ligament or atrial cuff within the pericardium. Atrial cuff reconstruction/ repair is possible using donor pericardium. Pulmonary artery injury may also occur and more frequently affects the right PA due to its course behind the aorta and SVC. Fortunately, the right PA is long and rarely needs repair if damaged; if it does, this can be achieved with simple suturing or reconstructed using available donor PA, azygous vein, or pericardium.
Unequal delivery of pulmonary preservation solution from a poorly placed main PA catheter can lead to graft ischemia-reperfusion injury due to insufficient protection during procurement. It is essential to ensure the cannula is aimed at the pulmonary valve and does not migrate into the distal PA, and that the lungs are blanching equally indicating appropriate delivery of preservation solution to both lungs.
References:
1. Copeland H, Hayanga JWA, Neyrinck A, et al. Donor heart and lung procurement: A consensus statement. J Heart Lung Transplant. Jun 2020;39(6):501-517. doi:10.1016/j.healun.2020.03.020
2. Levvey B, Keshavjee S, Cypel M, et al. Influence of lung donor agonal and warm ischemic times on early mortality: Analyses from the ISHLT DCD Lung Transplant Registry. J Heart Lung Transplant. Jan 2019;38(1):26-34. doi:10.1016/j.healun.2018.08.006
3. Van Raemdonck D, Neyrinck A, Cypel M, Keshavjee S. Ex-vivo lung perfusion. Transpl Int. Jun 2015;28(6):643-56. doi:10.1111/tri.12317