The overall goal of this experimental procedure is to assess the effects of anesthetics on the neonatal brain in a clinically relevant translational piglet model. This method can help answer key questions in the field of anesthesia-induced neurotoxicity such as how toxicity occurs and the developmental changes that accompany such toxicity. The primary advantage of this technique is that it provides a translationally relevant animal model for the study of anesthesia-induced developmental neurotoxicity in which physiologic homeostasis is maintained throughout experimentation.
During the anesthesia induction and throughout the procedure, monitor the following:pulse oximetry, noninvasive blood pressure, electrocardiography and temperature. The single most critical step during this procedure is the maintenance of physiologic homeostasis. This includes monitoring, temperature management, mechanical ventilation and blood chemistry analysis.
To prepare the piglet for surgery, first place a 24 gauge peripheral intravenous catheter in the marginal ear vein. Warm the piglet with heated forced air. Monitor its temperature using a rectal thermometer and continuously infuse dextrose containing isotonic fluid at a maintenance rate.
Then put the piglet in the dorsal recumbent position for a tracheal intubation. Next, spray the vocal cords with 0.5 milliliters of 2%lidocaine to prevent spasms during the intubation and then advance a three millimeter cuffed tracheal tube into the trachea. Secure the tube and then check for bilateral breath sounds using chest auscultation with a stethoscope and check for sustained end tidal carbon dioxide.
Next, apply ophthalmic ointment to the eyes. Just prior to starting the surgery, administer a broad spectrum antibiotic via the peripheral intravenous line to prevent surgical site infection. Now, sterilize both groins using at least two scrubs with chlorhexidine to ensure a proper sterile field.
Have the surgery staff wear caps, masks, gloves, and eye protection. Then drape the animal. To begin, palpate the femoral pulse at the inguinal crease.
And then using a scalpel, make a superficial 1.5 centimeter craniocaudal incision. Next, make a blunt dissection between the two heads of the gracilis muscle. Now, locate the femoral neurovascular bundle.
It is typically found between the two muscles. Then with vascular loops or silk ties, isolate the artery at the proximal and distal end. Next, using the loop at the proximal end, pull the artery up to the level of the skin distally and put traction on the proximal tie to interrupt the blood flow.
While maintaining the traction, use tenotomy scissors to make a small arteriotomy. Then advance the catheter or polyethylene tubing directly into the vessel. Blood return should be observed immediately.
Now, immediately attach and secure a catheter connected to a pressure transducer. Then cover the completed incision with sterile gauze and flush the catheter with normal saline. Throughout the anesthetic exposure, monitor the piglet's vital signs.
Look for perturbations that could indicate hypotension, arrhythmia, hypo or hyperthermia, or hypoxia. At least once per hour during the experiment, draw an arterial blood sample from the femoral artery catheter. Then use an automated analysis system to collect blood values from the sample.
After sufficient anesthetic exposure, remove the femoral artery catheter and carefully tie down the proximal vascular silk suture to permanently occlude the femoral artery and prevent bleeding. Next, irrigate the incision with 10 to 20 milliliters of saline to help prevent infection. Once complete hemostasis is confirmed, close the incision using 3-0 silk suture in a simple interrupted pattern.
Now, infiltrate the wound with bupivacaine and epinephrine for pain control. Then coat the incision with a sterile surgical skin adhesive, discontinue the anesthetic and allow the piglet to wake up. 40 male piglets were studied.
Between the control and experimental groups, there was no significant difference with respect to their age or weight. All were comprehensively monitored during the procedure and all tolerated it well. The average laboratory values during the experimentation in the isoflurane group illustrate the internal consistency and reproducibility of the procedure.
The consistency was observed in a span of two years with the data pooled from different operators. After watching this video, you should have a good understanding of how to use a physiologically appropriate translational piglet model to answer nearly any pre-clinical pediatric research question. Don't forget that working with anesthetic agents can be hazardous and precautions such as appropriate anesthetic gas scavenging should always be taken when performing this procedure.
