This protocol is one of the most straightforward lung transplant protocols for large animal models and provides the most detail in terms of surgical management. The main advantages of this technique are describing the surgery, assessing isolated left lung function post-transplant, and stabilizing the pig during surgery. The method is beneficial in ex-situ lung profusion research to validate ex-situ findings with an in vivo reperfusion transplantation model.
The in vivo reperfusion model of lung transplantation is beneficial for testing ex-situ lung profusion findings and could also be used in artificial organ testing, such as bio-engineered or mechanical lungs. Begin by positioning the pig in a right lateral decubitus position for the left anterior lateral thoracotomy. Then identify the tip of the left scapula in the xiphoid process, inferior to the sternum with palpation, and connect the two identified spots to mark the 20 centimeter long thoracotomy incision site.
After inducing the anesthesia, use a scalpel to make an incision on the skin and then use electrocautery to dissect the subcutaneous layers and muscle layers of the animal. The latissimus dorsi must be divided. After identifying the rib immediately below the incision, cauterize on top of the rib to expose the intercostal muscles while avoiding the intercostal neurovascular bundle.
Use a mosquito hemostat to puncture the intercostal muscles immediately above the rib and then feel inside the chest for adhesions with a finger. While the top edge of the rib is being cauterized, push the lung away using a Yankauer suction to extend the thoracotomy anteriorly until one inch away from the sternum, and posteriorly to the paraspinal muscles. By inserting a Cooley sternal retractor, open the thoracotomy 10 centimeter wide to retract the lung and expose the left hemiazygos vein.
Use Metzenbaum scissors and a fine lower to dissect the left hemiazygos vein circumferentially. By circling the vessel with silk ties, ligate and transect the vein. Dissect out the left pulmonary artery, or PA, and left pulmonary veins, or PV, before encircling the veins in the silk ties.
After five minutes of heparin administration, clamp the PA with a DeBakey cross clamp, the left anterior PV with a Satinsky clamp and the left bronchus with Spoon Pots clamp. Transect the PA, the left inferior PV and the left bronchus leaving at least 0.5 centimeters of tissue cuff. After dividing the left inferior pulmonary ligament, remove the left lung.
For transplantation, insert the donor lung into the recipient's chest, beginning with the lower lobe without forcing the lung into the place. Then perform the bronchial anastomosis using a 4.0 Prolene suture on a TF needle. To assess the bronchial anastomosis in suction secretions, perform left and right lung bronchoscopy by inserting a bronchoscope into the endotracheal tube using an adapter connection, then connect the scope to suction before advancing the bronchoscope into the left bronchus.
Observe the lung breathing and inspect the vitals in bronchial anastomosis. Repeat the process on the right side. Next, use a 6.0 Prolene suture on BV-1 Needles to perform end-to-End left atrium or LA anastomosis followed by trimming excess tissue.
After incorporating the donor SVPs into the inferior PV and LA anastomosis, complete the PA anastomosis with a 6.0 Prolene suture on BV-1 needles using a running end-to-End anastomosis. Later, confirm heparinization and administer a potassium shift to the animal. Then open the PA clamp partially to de-air and let the blood flow through the suture line.
Next, release the LA clamp and let the suture line back bleed to further release any trapped air. Tie the LA and then remove the PA clamp completely. Once done, remove the bronchial clamp and increase tidal volumes to target 10 milliliters per kilogram.
After inserting a 20 French malleable chest tube, close the thoracotomy in three layers. Using Metzenbaum scissors, open the left pleura to take blood samples from the left lower lobe. Open the right pleura to dissect out the right pulmonary artery.
Then place a clamp to stop right lung perfusion. Direct a 21 gauge needle toward the left pulmonary veins and away from the common left atrium to take a blood sample from the LA anastomosis to assess left lung function. After clamping, take the blood samples from the left PV anastomosis with a 21 gauge needle directed toward the left lung.
The representative analysis indicates typical PF ratio changes and edema formation during the lung transplant protocol. At the reperfusion, the PF ratios dropped by approximately 100 millimeters of mercury as the left lung was not immediately effective at oxygenation. In isolated left lung assessment at four hours, the PF ratio was stable.
In a successful transplant, the left lung could experience approximately 20%to 50%weight gain due to residual blood in the circulation. After 12 hours of the left lung transplant, the blood gas analysis was performed. It was observed that the potassium level was increased during 60 to 120 minutes of reperfusion.
Approximately two to four shifts were required during four hour reperfusion to keep potassium lower than five millimoles per liter. Instead of suture ligating the recipient's superior pulmonary veins, the side biting clamps can be used for vascular control and the vessels can be easily over sewn.
