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.
