Mortality rates for children with congenital heart defects have improved significantly in recent years given improvements in cardiac surgery. However, comorbidities remain extremely common, and that's the goal of our lab. We aim to investigate these comorbidities, uncover underlying causes, and develop preventative measures.
Right now, we are studying neuro abnormalities that develop after cardiac surgery. This protocol offers a feasible and reproducible animal model of simulating pediatric cardiac surgery. So with that, researchers can use it as a base to test many different experimental conditions and a wide variety of other hypotheses.
The peripheral cannulation technique for porcine cardiopulmonary bypass in our model is both practical and cost effective. Furthermore, it does allow a more reliable way to assess postoperative outcomes than the traditional central cannulation technique. The flexibility of our model encourages future work in congenital heart disease and comorbidity studies.
For example, our lab is currently planning to expand this model to study real-time monitoring of cerebral parameters, such as oxygenation status, and cerebral blood flow. To begin place the four to six days old anesthetized piglet in the dorsal recumbency position. After performing orotracheal intubation using a cuffed tube, auscultate the lung bases to confirm appropriate endotracheal tube placement.
Set up mechanical ventilation, and continuously monitor the depth of anesthesia during surgery through heart rate, blood pressure, and oxygen saturation. Adjust ventilatory and sedation parameters as required. Then insert a 3 French catheter in the femoral artery, followed by a 4 French catheter in the vein.
Next, initiate the cardiopulmonary bypass, or CPB, circuit setup by shortening the CPB tubing while maintaining enough distance between the animal and the machine. Create a tubing bridge to connect the membrane oxygenator outflow and pump inflow. Once all the connection points are sealed, sweep the circuit with 300 microliters of heparin saline solution and 300 milliliters of fresh donor pig blood, followed by sodium bicarbonate, heparin, and calcium gluconate.
Once the CPB circuit is ready, expose the left internal jugular vein and insert the needle catheter into it. Similarly, expose the right carotid artery to prepare for cannulation. Once a blood flash is visible, carefully insert a guide wire into the vessel.
Thread a dilator over the wire and into the vessel. Then remove the dilator. Slowly thread an 8 French venous cannula approximately four centimeters into the vessel and remove the wire, ensuring the cannula remains in place.
Then, place a 6 French pediatric arterial cannula into the right carotid artery as previously demonstrated with dilation. Finally, administer an intravenous heparin bolus through the newly placed arterial cannula. After achieving access, use 3-O absorbable sutures to fix both cannulas to the animal and tape to prevent inadvertent removal.
Connect the cannulas to the CPB circuit, ensuring heparin saline is added to the connection points to prevent air in the circuit. Set the initial flow to 80 to 85 milliliters per kilogram per minute. To induce cardiac arrest, administer nine milli equivalents of potassium chloride.
Once the heart is stopped, isolate the animal from the circuit, then maintain the CPB circuit flow to circulate at 1, 500 RPM. After achieving appropriate cardiac arrest conditions, begin extra corporeal cardiopulmonary resuscitation by reconnecting the piglet to the CPV circuit. Administer three milliliters of calcium gluconate and six milliliters of sodium bicarbonate through peripheral arterial access, adding doses as necessary.
The vessel cannulation and CPB with cardiac arrest achieved a 92%success rate in the experiments. MRIs demonstrated clear signs of early brain damage in the CPB with cardiac arrest animals compared to control. The acute diffusion tensor imaging modality better identified the signs of infarction than other conventional MRI sequences.
