preparation of pigs for hemodynamic monitoring studies 

Surgical Technique for Jugular Vein Thermodilution Catheter Placement in Pigs

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.

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

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 metal. 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.

Preparation of Pigs for Hemodynamic Monitoring Studies 

To begin, dilute 1, 000 international units of heparin in three 250-milliliter, 0.90%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.

preparation-of-pigs-for-hemodynamic-monitoring-studies

Research

JoVE Journal

Medicine

37 Views. To begin, dilute 1, 000 international units of heparin in three 250-milliliter, 0.90%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 sedate...

Video: Preparation of Pigs for Hemodynamic Monitoring Studies 

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.

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).

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

Thermodilution Catheter Placement and Cardiac Output Measurement in Pigs

After placing the anesthetized pig in the dorsal position on a surgical table, perform antisepsis of the cervical region with iodopovidone and 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's Mosquito hemostatic forceps, and insert the 5 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 five-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.