Determination of Cardiac Output in a Porcine Model for Ex Vivo Pulmonary Perfusion

This study was carried out to ensure whether the calculation of cardiac output by the thermal lesion method in pigs allow us to obtain equal values to those obtained by the other techniques to establish the adequate perfusion flow during Ex vivo lung perfusion or EVLP in experimental animal models. One of the challenges is the development of new and low cost solutions and technologies for performing EVLP, which would allow the recovery of lungs that under normal circumstances could be discarded for a lung transplant, as well as allowing prolonged lung preservation. Evaluation of the structural and molecular changes that are present in lung tissue after prolonged preservation to EVLP with different perfusion flow.

Among the new scientific questions that our results have opened is to evaluate what lung, structural, physiological, and molecular changes can occur after EVLP using cardiac output perfusion flow obtained by thermal elution, adjusted by body surface area, weight, and fixed method. In future studies, our laboratory will focus on evaluating how different perfusion flows affect the pulmonary endothelium during EVLP, with the goal for increasing the lung recovery and improving preservation for transplant. To begin, dilute 1000 international units of Heparin in three 250 milliliter 0.9%sodium chloride solutions.

Attach pressure transducers to the vital signs monitor. Connect the Heparinized solutions to the transducer via needleless intravenous infusion. Remove the thermodilution catheter from the packaging and immerse the distal end in 0.9%sodium chloride to check the integrity of the balloon.

Check the patency of the distal and proximal catheter connections. After placing the sedated pig, insert a catheter into the marginal vein of the left ear. Lower the mandible with the help of laboratory staff to keep the mouth open and the tongue sticking out.

Spray 10%Lidocaine onto the vocal cords. Then, clear accumulated saliva with gauze held by ring forceps and separate the epiglottis from the laryngeal opening. Using a laryngoscope and a number three straight blade, identify the tracheal entrance.

Then, insert a seven French endotracheal tube with a balloon. Inflate the balloon and fix the tube to the mandible after verifying its placement within the airway. After placing the anesthetized pig in the dorsal position on a surgical table, perform antisepsis of the cervical region with Iodopovidone alcohol three times each.

Make a 10-centimeter paramedian incision using an electrocautery pencil and dissect the subcutaneous tissue to expose the right external jugular vein by blunt dissection. Place two size 2-0 silk sutures at the distal and proximal portion of the dissected vessel. Insert the catheter extracorporeally from the neck site to the thoracic region where the heart is located.

Measure the insertion depth using markings on the catheter to reach the pulmonary artery. Ligate the distal portion of the vessel and place a double loop in the proximal portion to secure the catheter. Next, use iris scissors to make a two-millimeter transverse incision on the ventral portion of the vessel.

Open the edges of the incision with Halsted mosquito hemostatic forceps and insert the five French thermodilution catheter into the right jugular vein. Following the curves of the right ventricle, pulmonary artery pressure, cardiac output, and systemic arterial pressure, direct the catheter towards the pulmonary artery. Once the vein is dissected and reference sutures are placed, displace the sternocephalic muscle laterally.

Then, dissect the pretracheal musculature until the carotid artery is exposed. Cannulate the carotid artery similar to the jugular vein and connect it to the pressure transducer for monitoring the systemic arterial pressure. Inject a 5-milliliter bolus of cold saline solution into the proximal lumen of the thermodilution catheter within four seconds.

Observe the thermodilution curve on the monitor. After confirming the validity and similarity of the curves, calculate the average of the three values and record it as the final cardiac output value in liters per minute. The cardiac output adjusted by body surface area was greater than that obtained by the thermodilution method and the cardiac output adjusted by weight.