The authors want to thank Roberto, Rueda, and Sergio Mart&#237;nez for their invaluable technical assistance with technical support with animals.

The protocol (B09-17) was approved by the bioethics committee of the INER (Instituto Nacional de Enfermedades Respiratorias &#34;Ismael Cosio Villegas&#34;). Twenty-three clinically healthy Landrace pigs of either sex, weighing between 20-25 kg, were used for this study. The animals were handled according to the technical specifications for the Care and Use of Laboratory Animals of the Official Mexican Standard17 and the Guide for the Care and Use of Laboratory Animals of the USA18. All animals were obtained from the Instituto Nacional de Enfermedades Respiratorias Ismael Cosio Villegas and were housed in individual cages under identical environmental conditions (12 h of light and 12 h of darkness, temperature of 22 &#176;C, on solid slatted floors) and provided with water and food (Pellet) ad libitum. In all animals, a thermodilution catheter was placed in the right jugular vein, and an arterial catheter was placed in the carotid artery on the same side to collect blood gases and then calculate the CO. The details of the reagents and equipment used are listed in the Table of Materials.
1. Experimental preparation
<ol>
	<li>Dilute 1000 IU of heparin in each of three 250 mL 0.9% sodium chloride solutions (saline solution, SS).</li>
	<li>Attach pressure transducers to the vital signs monitor. Use each transducer to measure the pressure at the corresponding port of the thermodilution catheter.</li>
	<li>Connect the heparinized solutions to the pressure transducer using an infusion set, checking that there are no air bubbles inside it.</li>
	<li>Remove the thermodilution catheter from the packaging. Immerse the distal end in 0.9% NaCl to check the integrity of the balloon.</li>
	<li>Check the patency of the distal and proximal catheter connections. Keep the catheter on the surgical instrument table until use.</li>
</ol>
2. Animal preparation
<ol>
	<li>Administer 0.05 mg/kg atropine and 4 mg/kg tiletamine-zolazepam intramuscularly to all pigs in the animal preparation room (following institutionally approved protocols).</li>
	<li>Leave the pigs undisturbed but under surveillance until they become recumbent and remain in this position without signs of excitement or response to nociceptive stimuli.</li>
	<li>Place the sedated animal in the prone position and insert a catheter into the marginal vein of the left ear.</li>
	<li>Transfer the animal to the operating room for surgery.</li>
	<li>Place the animal in the dorsal position and administer 4 mg/kg propofol IV, 300 &#181;g/kg vecuronium bromide, and 0.1 mg/kg fentanyl IV. Apply an ophthalmic ointment to prevent eye dryness during the anesthesia procedure.</li>
	<li>Lower the mandible of the pig with the help of laboratory staff to keep the mouth open and the tongue sticking out.</li>
	<li>Spray 10% lidocaine onto the vocal cords, clear accumulated saliva with gauze held by ring forceps, and separate the epiglottis from the laryngeal opening.</li>
	<li>Identify the tracheal entrance with a laryngoscope and a number 3 straight blade, then insert a 7 Fr endotracheal tube with a balloon.</li>
	<li>Inflate the balloon and fix the tube to the mandible after verifying its placement within the airway.</li>
	<li>Connect the pig to the anesthesia machine to maintain an anesthetic state with 2.5%-3% sevoflurane (Figure 1).</li>
	<li>Ventilate the animal in volume-controlled ventilation mode with a frequency of 25 breaths/min, tidal volume of 6-8 mL/kg weight, FiO2% of 50%-70% to maintain SaO2 greater than 90%, trigger of 2, positive end-expiratory pressure (PEEP) of 5 cmH2O, inspiration ratio of 1:2 s, and inspiratory flow of 15 L/min and maximum of 30 L/min.</li>
</ol>
3. Placement of the thermodilution catheter and measurement of cardiac output
<ol>
	<li>Keep the animal in the dorsal position under general anesthesia and perform antisepsis of the cervical region with iodopovidone and alcohol, three times each (Figure 2). Make a 10 cm paramedian incision using an electrocautery pencil and dissect the subcutaneous tissue to expose the right external jugular vein by blunt dissection.</li>
	<li>Place two 2-0 silk sutures, one at the distal portion and the other at the proximal portion of the dissected vessel (Figure 3).</li>
	<li>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 (PA). Ligate the distal portion of the vessel and place a double loop in the proximal portion to secure the catheter once inserted.</li>
	<li>Make a 2 mm transverse incision on the ventral portion of the vessel using iris scissors. Open the edges of the incision with Halsted&#39;s mosquito hemostatic forceps and insert the 5Fr thermodilution catheter into the right jugular vein (Figure 4, Figure 5, and Figure 6). Direct the catheter towards the pulmonary artery (PA) by following the curves displayed on the monitor.</li>
</ol>
4. Placement of the arterial catheter
<ol>
	<li>Once the vein is dissected and reference sutures are placed, displace the sternocephalic muscle (equivalent to the sternocleidomastoid) laterally.</li>
	<li>Dissect the pretracheal (sternohyoid) musculature until the carotid artery is exposed.</li>
	<li>Cannulate the carotid artery similar to the jugular vein and connect it to the pressure transducer for monitoring the systemic arterial pressure.</li>
</ol>
5. Evaluation
<ol>
	<li>Once the thermodilution catheter is placed in the right jugular vein and the arterial catheter is placed in the carotid artery on the same side, take samples for blood gas analysis.</li>
	<li>Obtain the blood gas values and evaluate cardiac output (CO) using the thermodilution method, body surface area, and Fick&#39;s method. 
	NOTE: For detailed procedures, please refer to previously published reports19-21.</li>
</ol>
6. Statistical analysis
<ol>
	<li>Analyze data demonstrating a normal distribution using analysis of variance (ANOVA) and perform Tukey&#39;s post hoc test. Express values as the mean &#177; standard error. Consider p values &#60;0.05 as indicating statistical significance.</li>
</ol>
7. Thermodilution measurement
<ol>
	<li>Inject a 5 mL bolus of cold SS at 4 &#176;C into the proximal lumen of the thermodilution catheter in less than 4 s.</li>
	<li>Observe the thermodilution curve (temperature/time) on the monitor screen. The curve should show a rapid ascent followed by a smooth and gradual descent to the baseline, with numerical values displayed with one or two decimal places.</li>
	<li>Repeat the bolus injection process with two additional boluses of cold SS until the curves are valid, similar, and within 10% of the average value.</li>
	<li>After confirming the validity and similarity of the curves, calculate the average of the three values and record it as the final CO value in liters per minute. Obtain CO and other indices from the thermodilution curve using calculations based on the Stewart-Hamilton equation21.</li>
</ol>
8. Determining adjusted cardiac output for body surface area (BSA) or cardiac index
<ol>
	<li>To determine the adjusted cardiac output (CI), calculate the body surface area (BSA) using the DuBois-DuBois formula19: 
	BSA = 0.007184 &#215; (Height (cm)0.725) &#215; (Weight (kg)0.425).</li>
	<li>Once BSA is obtained, calculate the CI using the formula20: 
	CI = CO/BSA. 
	NOTE: CO is determined in step 7.</li>
</ol>
9. Estimating cardiac output by the Fick&#39;s method
<ol>
	<li>To calculate cardiac output (CO) using the Fick&#39;s method, determine the oxygen consumption (VO2) and the difference in oxygen levels obtained from arterial (SaO2) and venous (SvO2) blood gases. Calculate VO2 using the formula21: 
	VO2 = CO x (SaO2 - SvO2).</li>
	<li>Then, determine cardiac output using the formula21: 
	CO = VO2 / ([SaO2 - SvO2] &#215; 10).</li>
</ol>
10. Estimating cardiac output per body weight
<ol>
	<li>Determine the cardiac output per bodyweight of the animals following previous reports8,15. 
	NOTE: In the EVLP protocol, various groups have reported that the estimated cardiac output (CO) per body weight in pigs is 100 mL/kg8,15.</li>
</ol>
11. Euthanasia
<ol>
	<li>Euthanize all animals with an overdose of sodium pentobarbital (150 mg/kg/IV) via the jugular vein sheath (following institutionally approved protocols) once all measurements are completed.</li>
	<li>Continue general anesthesia and cardiac monitoring until the electrocardiography (ECG) trace shows no cardiac electrical activity17,18.</li>
</ol>

Surgical Technique for Jugular Vein Thermodilution Catheter Placement in Pigs

<ol>
	<li>Mohite, P. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+lung+perfusion+made+easy.">Ex vivo lung perfusion made easy.</a> Multimed Man Cardiothorac Surg. 23, 2021 (2021).</li><li>Cypel, M., Keshavjee, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+lung+perfusion.">Ex vivo lung perfusion.</a> Oper Tech Thorac Cardiovasc Surg. 19 (4), 433-442 (2014).</li><li>Langmuur, S. J. J., Max, S. A., &#199;elik, M., Mahtab, E. A. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+lung+perfusion:+A+procedural+guide.">Ex vivo lung perfusion: A procedural guide.</a> Multimed Man Cardiothorac Surg. 2023, (2023).</li><li>Kesseli, S. J., Davis, R. P., Hartwig, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Commentary:+Making+lungs+great+again-introducing+new+modifications+to+the+Toronto+ex+vivo+lung+perfusion+protocol.">Commentary: Making lungs great again-introducing new modifications to the Toronto ex vivo lung perfusion protocol.</a> J Thorac Cardiovasc Surg. 161 (6), 1974-1975 (2021).</li><li>Roman, M. A., Nair, S., Tsui, S., Dunning, J., Parmar, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+lung+perfusion:+A+comprehensive+review+of+the+development+and+exploration+of+future+trends.">Ex vivo lung perfusion: A comprehensive review of the development and exploration of future trends.</a> Transplantation. 96 (6), 509-518 (2013).</li><li>Van Raemdonck, D., Neyrinck, A., Cypel, M., Keshavjee, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex-vivo+lung+perfusion.">Ex-vivo lung perfusion.</a> Transpl Int. 28 (6), 643-656 (2015).</li><li>Machuca, T. N., Cypel, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ex+vivo+lung+perfusion.">Ex vivo lung perfusion.</a> J Thorac Dis. 6 (8), 1054-1062 (2014).</li><li>Beller, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduced-flow+ex+vivo+lung+perfusion+to+rehabilitate+lungs+donated+after+circulatory+death.">Reduced-flow ex vivo lung perfusion to rehabilitate lungs donated after circulatory death.</a> J Heart Lung Transplant. 39 (1), 74-82 (2020).</li><li>Garc&#237;a, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Estimating+cardiac+output,+utility+in+the+clinical+practice:+Available+invasive+and+non-invasive+monitoring.">Estimating cardiac output, utility in the clinical practice: Available invasive and non-invasive monitoring.</a> Med Intensiva. 35 (9), 552-561 (2011).</li><li>Blanco-Tencio, F. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparability+of+cardiac+output+measured+by+pulse+contour+analysis+compared+with+transesophageal+echocardiography+at+the+Calder&#243;n+Guardia+Hospital+from+April+to+July+2021.">Comparability of cardiac output measured by pulse contour analysis compared with transesophageal echocardiography at the Calder&#243;n Guardia Hospital from April to July 2021.</a> Tesis Especialidad en Anestesiología y Recuperaci&#243;n. Universidad de Costa Rica. San Jose, Costa Rica. , (2021).</li><li>Physiology, Cardiac output. StatPearls Publishing Available from: <a target="_blank" href="https://www.ncbi.nlm.nih.gov/books/NBK470455/">https://www.ncbi.nlm.nih.gov/books/NBK470455/</a> (2022)</li><li>Johnson, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+physiology.">Cardiac physiology.</a> Essentials of Cardiac Anesthesia. , 53-66 (2008).</li><li>Corsini, A., Cercenelli, L., Zecchi, M., Marcelli, E., Corazza, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Basic+hemodynamic+parameters.">Basic hemodynamic parameters.</a> Advances in Cardiovascular Technology. , 463-474 (2022).</li><li>Mateu Campos, M. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Techniques+available+for+hemodynamic+monitoring:+Advantages+and+limitations.">Techniques available for hemodynamic monitoring: Advantages and limitations.</a> Med Intensiva. 36 (6), 434-444 (2012).</li><li>Cypel, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Technique+for+prolonged+normothermic+ex+vivo+lung+perfusion.">Technique for prolonged normothermic ex vivo lung perfusion.</a> J Heart Lung Transplant. 27 (12), 1319-1325 (2008).</li><li>National Transplant Organization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=National+protocol+for+the+maintenance+of+potential+donor+in+brain+death.">National protocol for the maintenance of potential donor in brain death.</a> SEMICYUC. , (2020).</li><li>Estados Unidos Mexicanos. AF&#205;A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Especificaciones+T&#233;cnicas+para+la+Producci&#243;n,+Cuidado+y+Uso+de+Animales+de+Laboratorio+de+la+Norma+Oficial+Mexicana+NOM-062-ZOO-1999.">Especificaciones T&#233;cnicas para la Producci&#243;n, Cuidado y Uso de Animales de Laboratorio de la Norma Oficial Mexicana NOM-062-ZOO-1999.</a> Diario Oficial de la Federaci&#243;n 6 dic. , (1999).</li><li>National Institutes of Health U.S.A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gu&#237;a+Para+el+Cuidado+y+Uso+de+Los+Animales+de+Laboratorio.">Gu&#237;a Para el Cuidado y Uso de Los Animales de Laboratorio.</a> Department of Health and Human Services, Public Health Service, National Institutes of Health U.S.A. , (2002).</li><li>Flint, B., Hall, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Body+surface+area.">Body surface area.</a> StatPearls. , (2023).</li><li>Ewah, P. A., Oyeyemi, A. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Relation+between+derived+cardiovascular+indices,+body+surface+area,+and+blood+pressure/heart+rate+recovery+among+active+and+inactive+Nigerian+student.">Relation between derived cardiovascular indices, body surface area, and blood pressure/heart rate recovery among active and inactive Nigerian student.</a> Bull Fac Phys Ther. 27, 34 (2022).</li><li>Kobe, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cardiac+output+monitoring:+Technology+and+choice.">Cardiac output monitoring: Technology and choice.</a> Ann Card Anaesth. 22 (1), 6-17 (2019).</li><li>Nelson, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Animal+models+of+ex+vivo+lung+perfusion+as+a+platform+for+transplantation+research.">Animal models of ex vivo lung perfusion as a platform for transplantation research.</a> World J Exp Med. 4 (2), 7-15 (2014).</li><li>Argueta, E., Paniagua, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermodilution+cardiac+output+a+concept+over+250+years+in+the+making.">Thermodilution cardiac output a concept over 250 years in the making.</a> Cardiology Rev. 27 (3), 138-144 (2019).</li><li>Perry, D. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Changes+in+tissue+oxygen+tension,+venous+saturation,+and+Fick-based+assessments+of+cardiac+output+during+hyperoxia.">Changes in tissue oxygen tension, venous saturation, and Fick-based assessments of cardiac output during hyperoxia.</a> Acta Anaesthesiol Scand. 63 (1), 93-100 (2019).</li></ol>

The authors have declared that no competing interests exist.

EVLP in pigs has a direct translation to human clinical practice, given the comparability in the size, physiology, and genomic sequence of the two species22. According to the EVLP protocol selected by the researcher, the measurement of CO is essential for determining the flow required to perfuse the lungs. Moreover, depending on the resources and knowledge available, the appropriate method can be chosen. However, no study has compared the methods for evaluating CO simultaneously against a referenc...

In lung transplantation centers, ex vivo lung perfusion (EVLP) is a tool that helps increase the potential for donation of lungs that do not meet the standard criteria for transplantation1. This is achieved by preserving and improving the lung functionality of donors with brain death or cardiac arrest, as well as by evaluating lung performance before transplantation2,3,4. In EVLP, an extracorporeal circulation pump allows perfusion of the lung to be transplanted through a membrane gas exchanger and a leukocyte trapping filter5.
To date, several EVLP protocols have been described (Toronto, Lund, and Organ Care System). These are differentiated by the type of perfusion solution used, whether the left atrium is kept open or closed during perfusion, and by the perfusion flow, which varies from 40% to 100% (depending on the technique used) of the estimated cardiac output (CO) of the donor6,7,8. CO is the amount of blood pumped by the heart per minute9 and is the mechanism by which tissue perfusion is maintained. Thus, CO monitoring ensures proper tissue oxygenation. CO, a product of the heart rate and the stroke volume, is measured in liters10,11,12. However, this approach for maintaining tissue perfusion also depends on other factors, such as venous return, peripheral oxygen use, systemic vascular resistance, respiration, total blood volume, and body position12.
There are several devices for measuring and monitoring CO, some of which use simple physical principles, while others use mathematical models. These methods include the Fick principle, thermodilution (transpulmonary or lithium dilution), analysis of the arterial pressure wave to estimate stroke volume (SV), and less invasive methods such as Doppler or thoracic bioreactance. However, no CO monitoring device can meet all clinical requirements due to the limitations of the corresponding monitoring technique10,13.
The measurement of CO by transcardiac thermodilution is a simple and easily reproducible method in pigs. It involves placing a catheter with a thermistor in the pulmonary artery and injecting a volume of liquid with a temperature lower than that of the blood. The thermistor detects changes in temperature over time, which are then plotted in the form of a curve, with the area under the curve representing minute volume14. Various studies have described that for EVLP animal models, CO can be calculated by weight (100 mL/kg)15, thermodilution, and Fick&#39;s method10,13. However, in the clinic, CO is calculated using the cardiac index (CI), which is the CO adjusted to the donor&#39;s body surface area16. Nevertheless, there are no studies comparing these methods in experimental pig models.
The objective of this study was to reproduce the measurement of CO by thermodilution in pigs and compare its precision and accuracy with those obtained using CO adjusted by BSA, weight, and Fick&#39;s method to establish perfusion flow during EVLP.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Anesthesia machine</td>
			<td>General Electric</td>
			<td>Carescape 620</td>
			<td></td>
		</tr>
		<tr>
			<td>Atropine</td>
			<td>Amixteria, Stern Pharma GmbH</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Catheter Insyte Autoguard 20 GA</td>
			<td>Becton Dickinson</td>
			<td>381434</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrocautery pencil</td>
			<td>BBraun Aesculap</td>
			<td>GN211</td>
			<td></td>
		</tr>
		<tr>
			<td>Endotracheal tube with a 7 Fr balloon</td>
			<td>Rush</td>
			<td>MG 027770 002</td>
			<td></td>
		</tr>
		<tr>
			<td>Fentanyl</td>
			<td>Janssen-Cilag</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Iodopovidone</td>
			<td>Degasa</td>
			<td>NDC6732635208</td>
			<td></td>
		</tr>
		<tr>
			<td>Laryngoscope</td>
			<td>Riester</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Lidocaine Spray</td>
			<td>Pisa</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Pressure transducers</td>
			<td>Edwards Lifesciences</td>
			<td>PX260</td>
			<td></td>
		</tr>
		<tr>
			<td>Propofol</td>
			<td>Pisa</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sevofluorane</td>
			<td>Pisa</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Silk sutures 2-0</td>
			<td>Covidien</td>
			<td>GS833</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium pentobarbital</td>
			<td>Pfizer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>straight blade of laryngoscope #3</td>
			<td>Miller; Riester</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Swan-Ganz 5Fr thermodilution catheter</td>
			<td>Arrow Thermodilution Ballon Catheter</td>
			<td>Ref AI-07165</td>
			<td></td>
		</tr>
		<tr>
			<td>Tiletamine-zolazepam</td>
			<td>Virbac</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Vecuronium bromide</td>
			<td>Pisa</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

determination of cardiac output in a porcine model for ex vivo pulmonary perfusion

Due to their physiological similarities to humans, pigs are used as experimental models for ex vivo lung perfusion (EVLP). EVLP is a technique that perfuses lungs that are not suitable for transplantation via an extracorporeal circulation pump to improve their function and increase their viability. Existing EVLP protocols are differentiated by the type of perfusion solution and perfusion flow, which varies from 40%-100% of the estimated cardiac output (CO) according to the body surface area (BSA). Devices for measuring CO use simple physical principles and other mathematical models. Thermodilution in animal models continues to be the reference standard for estimating CO because of its simplicity and ease of reproduction. Therefore, the objective of this study was to reproduce the measurement of CO by thermodilution in pigs and compare its precision and accuracy with those obtained by the BSA, weight, and Fick's method, to establish perfusion flow during EVLP. In 23 pigs, a thermodilution catheter was placed in the right jugular vein, and the carotid artery on the same side was cannulated. Blood samples were obtained for gasometry, and CO was estimated by thermodilution, adjusted body surface area, Fick's principle, and per body weight. The CO obtained by the BSA was greater (p = 0.0001, ANOVA, Tukey) than that obtained by the other methods. We conclude that although the methods used in this study to estimate CO are reliable, there are significant differences between them; therefore, each method must be evaluated by the investigator to determine which meets the needs of the protocol.

All animals survived the surgical procedure and the study time. One animal (4.3%) developed a jugular vein tear due to excessive traction during catheter insertion. Furthermore, none of the intervened vessels showed bleeding. In the studied animals, an average of 25-30 cm of catheter insertion was required to reach the PA. In three cases (13%), the catheter was directed towards the right upper limb of the pig. In these cases, the catheter was retracted to the insertion site, the pig&#39;s upper limb was repositioned towa...

Author Spotlight: Assessment of Cardiac Output Calculation by Thermodilution in Pigs for Effective Perfusion Flow During EVLP

This protocol describes the surgical technique used for the placement of a thermodilution catheter through the jugular vein in pigs to estimate cardiac output and ensure adequate lung perfusion during ex vivo lung perfusion (EVLP).

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

Due to their physiological similarities to humans, pigs are used as experimental models for ex vivo lung perfusion (EVLP). EVLP is a technique that ...

determination-cardiac-output-porcine-model-for-ex-vivo-pulmonary

Research

JoVE Journal

Medicine

373 Views.  Instituto Nacional de Enfermedades Respiratorias Ismael Cosio Villegas. This protocol describes the surgical technique used for the placement of a thermodilution catheter through the jugular vein in pigs to estimate cardiac output and ensure adequate lung perfusion during ex vivo lung perfusion (EVLP).

Video: Author Spotlight: Assessment of Cardiac Output Calculation by Thermodilution in Pigs for Effective Perfusion Flow During EVLP

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal hyperplasia (IH) that eventually leads to vessel occlusion and graft failure. Mechanical forces, particularly low shear stress and high wall tension, are thought to initiate and to sustain these cellular and molecular changes, but their exact contribution remains to be unraveled. To selectively evaluate the role of pressure and shear stress on the biology of IH, an ex&#160;vivo perfusion system (EVPS) was created to perfuse segments of human saphenous veins under arterial regimen (high shear stress and high pressure). Further technical innovations allowed the simultaneous perfusion of two segments from the same vein, one reinforced with an external mesh. Veins were harvested using a no-touch technique and immediately transferred to the laboratory for assembly in the EVPS. One segment of the freshly isolated vein was not perfused (control, day 0). The two others segments were perfused for up to 7 days, one being completely sheltered with a 4 mm (diameter) external mesh. The pressure, flow velocity, and pulse rate were continuously monitored and adjusted to mimic the hemodynamic conditions prevailing in the femoral artery. Upon completion of the perfusion, veins were dismounted and used for histological and molecular analysis. Under ex&#160;vivo conditions, high pressure perfusion (arterial, mean = 100 mm Hg) is sufficient to generate IH and remodeling of human veins. These alterations are reduced in the presence of an external polyester mesh.

Procedure for Human Saphenous Veins Ex Vivo Perfusion and External Reinforcement

The mechanisms leading to the development of intimal hyperplasia (IH) and vein graft failure are still poorly understood. This study describes an ex&#160;vivo system to perfuse human veins under controlled flow and pressure. Furthermore the efficiency of external mesh reinforcement to limit the development of IH was evaluated.

The mainstay of contemporary therapies for extensive occlusive arterial disease is venous bypass graft. However, its durability is threatened by intimal ...

Method of Isolated Ex Vivo Lung Perfusion in a Rat Model: Lessons Learned from Developing a Rat EVLP Program

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. As this technology expands and improves, the ability to potentially evaluate and improve the quality of substandard lungs prior to transplant is a critical need. In order to more rigorously evaluate these approaches, a reproducible animal model needs to be established that would allow for testing of improved techniques and management of the donated lungs as well as to the lung-transplant recipient. In addition, an EVLP animal model of associated pathologies, e.g., ventilation induced lung injury (VILI), would provide a novel method to evaluate treatments for these pathologies. Here, we describe the development of a rat EVLP lung program and refinements to this method that allow for a reproducible model for future expansion. We also describe the application of this EVLP system to model VILI in rat lungs. The goal is to provide the research community with key information and &#8220;pearls of wisdom&#8221;/techniques that arose from trial and error and are critical to establishing an EVLP system that is robust and reproducible.

Method of Isolated Ex Vivo Lung Perfusion in a Rat Model: Lessons Learned from Developing a Rat EVLP Program

Ex-Vivo Lung Perfusion (EVLP) has allowed lung transplantation in humans to become more readily available by enabling the ability to assess organs and expand the donor pool. Here, we describe the development of a rat EVLP program and refinements that allow for a reproducible model for future expansion.

The number of acceptable donor lungs available for lung transplantation is severely limited due to poor quality. Ex-Vivo Lung Perfusion (EVLP) has allowed ...

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, normothermic ex vivo liver perfusion (NEVLP) has been introduced as a method to evaluate and modify organ function. NEVLP has many advantages in comparison to hypothermic and subnormothermic perfusion including reduced preservation injury, restoration of normal organ function under physiologic conditions, assessment of organ performance, and as a platform for organ repair, remodeling, and modification. Both murine and porcine NEVLP models have been described. We demonstrate a rat model of NEVLP and use this model to show one of its important applications &#8212; the use of a therapeutic molecule added to liver perfusate. Catalase is an endogenous reactive oxygen species (ROS) scavenger and has been demonstrated to decrease ischemia-reperfusion in the eye, brain, and lung. Pegylation has been shown to target catalase to the endothelium. Here, we added pegylated-catalase (PEG-CAT) to the base perfusate and demonstrated its ability to mitigate liver preservation injury. An advantage of our rodent NEVLP model is that it is inexpensive in comparison to larger animal models. A limitation of this study is that it does not currently include post-perfusion liver transplantation. Therefore, prediction of the function of the organ post-transplantation cannot be made with certainty. However, the rat liver transplant model is well established and certainly could be used in conjunction with this model. In conclusion, we have demonstrated an inexpensive, simple, easily replicable NEVLP model using rats. Applications of this model can include testing novel perfusates and perfusate additives, testing software designed for organ evaluation, and experiments designed to repair organs.

A Small Animal Model of Ex Vivo Normothermic Liver Perfusion

There is a significant liver donor shortage, and criteria for liver donors have been expanded. Normothermic ex vivo liver perfusion (NEVLP) has been developed to evaluate and modify organ function. This study demonstrates a rat model of NEVLP and tests the ability of pegylated-catalase, to mitigate liver preservation injury.

There is a significant shortage of liver allografts available for transplantation, and in response the donor criteria have been expanded. As a result, ...

Normothermic Ex Situ Heart Perfusion in Working Mode: Assessment of Cardiac Function and Metabolism

The current standard method for organ preservation (cold storage, CS), exposes the heart to a period of cold ischemia that limits the safe preservation time and increases the risk of adverse post-transplantation outcomes. Moreover, the static nature of CS does not allow for organ evaluation or intervention during the preservation interval. Normothermic ex situ heart perfusion (ESHP) is a novel method for preservation of the donated heart that minimizes cold ischemia by providing oxygenated, nutrient-rich perfusate to the heart. ESHP has been shown to be non-inferior to CS in the preservation of standard-criteria donor hearts and has also facilitated the clinical transplantation of the hearts donated after the circulatory determination of death. Currently, the only available clinical ESHP device perfuses the heart in an unloaded, non-working state, limiting assessments of myocardial performance. Conversely, ESHP in working mode provides the opportunity for comprehensive evaluation of cardiac performance by assessment of functional and metabolic parameters under physiologic conditions. Moreover, earlier experimental studies have suggested that ESHP in working mode may result in improved functional preservation. Here, we describe the protocol for ex situ perfusion of the heart in a large mammal (porcine) model, which is reproducible for different animal models and heart sizes. The software program in this ESHP apparatus allows for real-time and automated control of the pump speed to maintain desired aortic and left atrial pressure and evaluates a variety of functional and electrophysiological parameters with minimal need for supervision/manipulation.

Normothermic ex situ heart perfusion (ESHP), preserves the heart in a beating, semi-physiologic state. When performed in a working mode, ESHP provides the opportunity to perform sophisticated assessments of donor heart function and organ viability. Here, we describe our method for myocardial performance evaluation during ESHP.

The current standard method for organ preservation (cold storage, CS), exposes the heart to a period of cold ischemia that limits the safe preservation ...

A Pre-Clinical Porcine Model of Orthotopic Heart Transplantation

Fifty-years following the first successful report, cardiac transplantation remains the gold-standard treatment for eligible patients with advanced heart failure. Multiple small-animal models of heart transplantation have been used to study the acute and long-term effects of novel therapies. However, few are tested and demonstrated success in clinical trials. It is of critical importance to evaluate new therapies in a clinically relevant large-animal model for efficient and reliable translation of basic studies&#39;&#160;findings. Here, we describe a pre-clinical large-animal (porcine) model of orthotopic heart transplantation that has been firmly established and previously used to investigate novel cardioprotective strategies. This procedure focuses on acute ischemia-reperfusion injury and is a reliable method to investigate novel interventions which have been tested and validated in smaller experimental models, such as the murine model. We demonstrate its usefulness in assessing cardiac performance during the early post-transplantation period and other potential possibilities enabled by the model.

Here, we describe a pre-clinical large-animal (porcine) model of orthotopic heart transplantation that has been firmly established and utilized to investigate novel cardioprotective strategies.

Fifty-years following the first successful report, cardiac transplantation remains the gold-standard treatment for eligible patients with advanced heart ...

Left Lung Orthotopic Transplantation in a Juvenile Porcine Model for ESLP

Lung transplantation is the gold-standard treatment for end-stage lung disease, with over 4,600 lung transplantations performed worldwide annually. However, lung transplantation is limited by a shortage of available donor organs. As such, there is high waitlist mortality. Ex situ lung perfusion (ESLP) has increased donor lung utilization rates in some centers by 15%-20%. ESLP has been applied as a method to assess and recondition marginal donor lungs and has demonstrated acceptable short- and long-term outcomes following transplantation of extended criteria donor (ECD) lungs. Large animal (in vivo) transplantation models are required to validate ongoing in vitro research findings. Anatomic and physiologic differences between humans and pigs pose significant technical and anesthetic challenges. An easily reproducible transplant model would permit the&#160;in vivo&#160;validation of current ESLP strategies and the preclinical evaluation of various interventions designed to improve donor lung function. This protocol describes a porcine model of orthotopic left lung allotransplantation. This includes anesthetic and surgical techniques, a customized surgical checklist, troubleshooting, modifications, and the benefits and limitations of the approach.

This protocol describes a juvenile porcine model of orthotopic left lung allotransplantation designed for use with ESLP research. Focus is made on anesthetic and surgical techniques, as well as critical steps and troubleshooting.

Lung transplantation is the gold-standard treatment for end-stage lung disease, with over 4,600 lung transplantations performed worldwide annually. ...

A Porcine Heterotopic Heart Transplantation Protocol for Delivery of Therapeutics to a Cardiac Allograft

Cardiac transplantation is the gold standard treatment for end-stage heart failure. However, it remains limited by the number of available donor hearts and complications such as primary graft dysfunction and graft rejection. The recent clinical use of an ex vivo perfusion device in cardiac transplantation introduces a unique opportunity for treating cardiac allografts with therapeutic interventions to improve function and avoid deleterious recipient responses. Establishing a translational, large-animal model for therapeutic delivery to the entire allograft is essential for testing novel therapeutic approaches in cardiac transplantation. The porcine, heterotopic heart transplantation model in the intraabdominal position serves as an excellent model for assessing the effects of novel interventions and the immunopathology of graft rejection. This model additionally offers long-term survival for the pig, given that the graft is not required to maintain the recipient's circulation. The aim of this protocol is to provide a reproducible and robust approach for achieving ex vivo delivery of a therapeutic to the entire cardiac allograft prior to transplantation and provide technical details to perform a survival heterotopic transplant of the ex vivo perfused heart.

We present a protocol for utilizing a normothermic ex vivo sanguinous perfusion system for the delivery of therapeutics to an entire cardiac allograft in a porcine heterotopic heart transplant model.

Cardiac transplantation is the gold standard treatment for end-stage heart failure. However, it remains limited by the number of available donor hearts ...

A Rodent Model of The Ross Operation: Syngeneic Pulmonary Artery Graft Implantation in A Systemic Position

The Ross operation for aortic valve disease has regained new interest due to its outstanding long-term results. Nonetheless, when employed as freestanding root replacement, the possible dilation of the pulmonary autograft and subsequent aortic regurgitation is described. Several animal models have been proposed. However, these are usually limited to ex-vivo models or in-vivo experiments with relatively expensive large animal models. In this study, we sought to establish a rodent model of pulmonary artery graft (PAG) implantation in a systemic position. A total of 39 adult Lewis rats were included. Immediately after euthanasia, the pulmonary root was harvested from a donor animal (n=17). Syngeneic recipient (n=17) and sham-operated (n=5) rats were sedated and ventilated. In the recipient group, the PAG was implanted with an end-to-end anastomosis in infra-renal abdominal aortic position. Sham-operated rats underwent only transection and re-anastomosis of the aorta. Animals were followed with serial ultrasound studies for two months and post-mortem histological analysis. The median PAG diameter in the native position was 3.20 mm (IQR=3.18-3.23). At follow-up, the median diameter of the PAG was 4.03 mm (IQR=3.74-4.13) at 1 week, 4.07 mm (IQR=3.80-4.28) at 1 month, and 4.27 mm (IQR=3.90-4.35) at 2 months (p&lt;0.01). Peak systolic velocity was 220.07 mm/s (IQR=210.43-246.41) at 1 week, 430.88 mm/s (IQR=375.28-495.56) at 1 month, and 373.68 mm/s (IQR=305.78-429.81) at 2 months (p=0.02) and did not differ from the sham-operated group at the end of the experiment (p=0.5). Histological analysis did not show any sign of endothelial thrombosis. This study showed that rodent models may allow for the evaluation of the long-term adaptation of the pulmonary root to a high-pressure system. A systemically placed syngeneic PAG implantation represents a simple and feasible platform for the development and evaluation of novel surgical techniques and drug therapies to further improve the outcomes of the Ross operation.

We demonstrate how to establish a murine model of pulmonary root implantation into the descending aorta to simulate the Ross procedure. This model enables the medium/long-term evaluation of pulmonary autograft remodeling in a systemic position, representing the basis of developing therapeutic strategies to promote its adaptation.

The Ross operation for aortic valve disease has regained new interest due to its outstanding long-term results. Nonetheless, when employed as freestanding ...

Large-Animal Model of Donation after Circulatory Death and Normothermic Regional Perfusion for Cardiac Assessment

The increase in demand for cardiac transplantation throughout the years has fueled interest in donation after circulatory death (DCD) to expand the organ donor pool. However, the DCD process is associated with the risk of cardiac tissue injury due to the inevitable period of warm ischemia. Normothermic regional perfusion (NRP) allows for an in situ organ assessment, allowing the procurement of hearts determined to be viable. Here, we describe a clinically relevant large-animal model of DCD followed by NRP. Circulatory death is established in anesthetized pigs by stopping mechanical ventilation. After a preset warm ischemia period, an extracorporeal membrane oxygenator (ECMO) is used for a NRP period lasting at least 30 min. During this reperfusion period, the model allows the collection of various myocardial biopsies and blood samples for initial cardiac evaluation. Once NRP is weaned, biochemical, hemodynamic, and echocardiographic assessments of cardiac function and metabolism can be performed before organ procurement. This protocol closely simulates the clinical scenario previously described for DCD and NRP in heart transplantation and has the potential to facilitate studies aimed at decreasing ischemia-reperfusion injury and enhance cardiac functional preservation and recovery.

The protocol describes a large-animal (porcine) model of donation after circulatory death, followed by thoracoabdominal normothermic regional perfusion that closely simulates the clinical scenario in heart transplantation, and has the potential to facilitate therapeutic studies and strategies.

The increase in demand for cardiac transplantation throughout the years has fueled interest in donation after circulatory death (DCD) to expand the organ ...

Functional Assessment of the Donor Heart During Ex Situ Perfusion: Insights from Pressure-Volume Loops and Surface Echocardiography

Heart transplantation remains the gold standard treatment for advanced heart failure. However, the current critical organ shortage has resulted in the allocation of a growing number of donor hearts with extended criteria. These marginal grafts are associated with a high risk of primary graft failure and may benefit from ex situ perfusion before transplant. This technology allows for extended organ preservation using warm oxygenated blood perfusion with continuous metabolic monitoring. The only NESP device currently available for clinical practice perfuses the organ in an unloaded non-working state, which does not allow for functional assessment of the beating heart. We therefore developed an original platform of NESP in working mode conditions with adjustment of left ventricular preload and afterload. This protocol was applied in porcine hearts. Ex situ functional assessment of the heart was achieved with intracardiac conductance catheterization and surface echocardiography. Along with a description of the experimental protocol, we herein report the main results, as well as pearls and pitfalls associated with the acquisition of pressure-volume loops and myocardial power during NESP. Correlations between hemodynamic findings and ultrasound variables are of major interest, especially for further rehabilitation of donor hearts before transplantation. This protocol aims to improve the assessment of donor hearts to both increase the donor pool and reduce the incidence of primary graft failure.

Functional Assessment of the Donor Heart During Ex Situ Perfusion: Insights from Pressure-Volume Loops and Surface Echocardiography

A reliable noninvasive approach for functional assessment of the donor heart during normothermic ex situ heart perfusion (NESP) is lacking. We herein describe a protocol for ex situ assessment of myocardial performance using the epicardial echocardiography and conductance catheter method.

Heart transplantation remains the gold standard treatment for advanced heart failure. However, the current critical organ shortage has resulted in the ...