Procurement of Lungs for Transplantation

Rishindra M. Reddy

Philip W. Carrott Jr

DEFINITION

The process of procuring lungs for transplant begins with the clinical assessment and management of donor lungs. The surgical procedure involves the visual assessment of the donor lungs and then the dissection, perfusion, removal, and packaging of the lungs for travel to the lung recipient site. The operation requires the close coordination between the abdominal and cardiac transplant surgeons with regard to timing of placing the cross-clamp and the separation of the heart and lungs.

PATIENT HISTORY AND PHYSICAL FINDINGS

The first step for lung procurement is the organ offer. The recipient transplant surgeon usually receives the organ offer, but at some centers, it is the pulmonologist or another member of the transplant team. Pertinent donor information includes medical history, history of the acute injury, documentation of brain death, arterial blood gas (ABG) values focusing on the PaO₂, bronchoscopy, and review of available imaging. Close monitoring of the ventilator, fluid, and pressor management is essential.
A seminal paper from Washington University¹ has set donor standards that continue to be used today. A minimum PaO₂ of 300 mmHg on ventilator settings of 100% FiO₂, positive end-expiratory pressure (PEEP) of 5, and tidal volumes of 10 to 12 mL/kg is needed. A bronchoscopy that is either negative for pneumonia or, if there are secretions, that they clear easily without reaccumulation. A chest x-ray that is clear bilaterally, although atelectasis may be present. If there are concerns about pneumonia or contusion, a chest computed tomography (CT) may be of use to differentiate between these and a pattern of reversible basilar atelectasis.
Lungs that are not optimized but have reversible conditions (fluid overload, atelectasis) may be managed by the recipient team in conjunction with the other organ teams. Diuresis and recruitment maneuvers may improve PaO₂ levels. Progressive pneumonia or contusions after trauma may be reversible in the long term but often are not reversible or treatable in the window of time needed to preserve the lungs.
Contraindications to lung procurement are changing. Programs are procuring more marginal lungs and even lungs from donors following cardiac death (DCD). The advent of ex vivo lung perfusion (EVLP) may allow the procurement and resuscitation of lungs that would not have otherwise been taken, and augment the current 16% lung procurement rate from potential donors. Current contraindications to lung use include donor history of more than 20 pack-year smoking history; age older than 50 years; prior history of lung disease including asthma, pulmonary hypertension, or pulmonary emboli; prior malignancy (except for potential brain tumors); and renal failure. Contraindications found during the donation workup and surgery include lungs with a structural abnormality such as a bleb or nodule of uncertain significance, current pneumonia or aspiration with likely pneumonia, and pulmonary edema that is not felt to be reversible prior to procurement.
Coordinating the recipient and donor operating room (OR) teams is vital for successful procurement. There is no standard with regard to coordination of the donor and recipient operations, but our group has the recipient in the OR awake with central intravenous (IV) lines placed at the time the donor OR begins. Minimize the time that the recipient is intubated. Thus, we do not intubate, prep, and drape the recipient until we know the expected aortic cross-clamp time of the donor. Consideration is also given to the expected time needed to mobilize the recipient’s lungs. This careful planning requires that the donor team communicates when they’ve arrived at the donor site, when the donor OR begins following bronchoscopy and initial intraoperative assessment of the lungs, the expected cross-clamp time (with regular updates as this changes constantly), the cross-clamp time, and an estimated time of arrival at the recipient site. The donor team should also contact the recipient OR 15 to 20 minutes from arrival. This will allow time for cardiopulmonary bypass, if clinically necessary. This close coordination is necessary to minimize the lung cold ischemia time. Generally, the upper limit of an acceptable cold ischemia time is 6 hours.

IMAGING AND OTHER DIAGNOSTIC STUDIES

A bronchoscopy should be performed locally, assessing for purulent secretions and sending lavage specimens for culture. A chest x-ray is also needed to rule out obvious structural concerns or trauma. Chest CT scans are helpful when assessing marginal lungs or a possible pneumonia.

SURGICAL MANAGEMENT

Preoperative Planning

Upon arrival at the donor site, the lung procuring surgeon must review a few key elements. The first step is to review the brain death evaluation and the consent to donate. Next, a thorough review of the donor’s history and hospital course is needed, including re-review of the acute injury that led to the donor’s status. Specific attention should be paid to the ventilator management and peak airway pressures of the donor, as high pressures may result in irreversible injury during the organ preservation process. Often, details of the donor’s history may not be communicated by the organ donation team to the recipient surgeon, and it is incumbent on the donor surgeon to ensure that the lungs are safe. Within this context, most lung transplant centers send out their own procurement team, as opposed to working with a local thoracic surgeon at the donor site. The donor team must review the ABG results, focusing not only on the actual values but also on the trends.

Positioning

Position the donor in a supine fashion, with both arms tucked at the sides. Skin prep the donor from the chin to the pubis to allow both the chest and abdominal teams to work concurrently. Central lines in the chest and neck may be prepped and will be excluded in the draping process.

TECHNIQUES

LUNG ASSESSMENT

The lung procurement begins with a bronchoscopy in the OR, either before or during the prepping and draping of the patient. Verify the endotracheal tube size; a tube less than 7 Fr will not accept a regular-sized bronchoscope. Attach the bronchoscope to suction and evaluate the bronchial anatomy and remove all secretions. Remove purulent secretions and determine whether mucopurulent secretions are limited to the central airways, or if they are coming from a peripheral source indicating pneumonia. If there is concern about pneumonia, repeat the bronchoscopy in 30 to 60 minutes looking for evidence of recurrent purulence. Note that the bronchoscope used for airway management by the anesthesia team is not adequate to remove secretions. Verify that ventilation settings include an FiO₂ of 100% and a PEEP of 5 throughout the procurement process, as repeat ABGs may be needed to reassess suitability of the lungs.
After the bronchoscopy, perform a median sternotomy. Make a skin incision from the sternal notch to the xiphoid process, connecting to the laparotomy incision of the abdominal team. Dissect with electrocautery through the subcutaneous fat, through the midline fascia, between the pectoralis major muscles, and onto the anterior table of the manubrium and sternum. Carry the dissection to the side of the xiphoid process. Place a finger under the xiphoid and lower sternum, freeing the pericardium and anterior mediastinal fat from the posterior table of the sternum. Dissect the sternal notch; first between the strap muscles and then through the ligamentous tissue at the base of the sternal notch. Place a finger behind the manubrium to free the mediastinal fat on the superior aspect of the sternum.
Ask the anesthesiologist to hold lung ventilation to minimize the risk of injury to the lungs. Use a reciprocating blade saw and proceed either at the top or bottom of the sternum. Saw through the midline to the other end, taking care to lift the posterior table with the blunt edge of the saw to elevate the sternum from the structures beneath it. Ventilate the lungs and spread the sternum. Cauterize bleeding from the anterior and posterior table. Bone wax can be used to minimize bleeding from the sternum. Place a laparotomy pad in the midline to tamponade sternal bleeding from the bone.
Place the sternal retractor. Carry the dissection through the thymus gland/fat and identify the innominate vein in the superior aspect of the chest. Incise the pericardium with the use of a plastic Yankauer suction placed under the pericardium on top of the heart. Carry the pericardial incision to the diaphragm and “T” off either side. Make the superior aspect of the pericardial incision to the lower border of the innominate vein (FIG 1). If the heart is being procured, a quick assessment can be made at this time.

Assess the lungs. Open the pleural spaces on either side from the diaphragm to the level of the innominate. Take care to not go too high on the pleural exposure, as the internal mammary vein may be damaged. Inspect the lungs one at a time. Ask the anesthesia provider to give a Valsalva maneuver after the entire lung, especially the lower lobe, is rotated out of the pleural space (FIG 2, right middle and lower lobes rotated out). This rotation may reduce preload and cause the donor to become transiently hypotensive. The donor surgeon must make the anesthesiologist aware of this possibility to prevent a clinical overreaction. Push all of the atelectasis out of the lower lobes to complete the recruitment process of the lungs. This may require milking air into the posterobasilar segments of the lower lobes. Make a full evaluation of the lung, including palpation, to identify possible nodules or structural abnormalities. If the atelectatic lung does not fully expand, then consider either a contusion and/or pneumonia. Once the recruitment and evaluation is completed, place the lungs back in the normal position and place pericardial stay sutures. Clamp them to the drapes or suture them to the skin.

FIG 1 • The sternal retractor is placed with the “L”-shaped portion placed superiorly as to not interfere with the abdominal team’s work. The innominate vein is identified, and the pericardial incision carried to the diaphragm. Here, the pericardial stay sutures (red arrows) have been placed bilaterally after the lungs have already been inspected.

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