Hi Khalid,

I have recently been implanting BP telemetry devices into the abdominal aorta of normotensive and hypertensive rats. 

A couple of questions first:

Do you occlude blood flow above and below the puncture point?

How much do you separate the aorta from the surrounding tissue?

I've seen some procedures recommend occluding above and below, which helps with seeing the point for insertion of the catheter tip easier after puncture (less blood flow). If you occlude below and some glue gets near the occlusion point then the abdominal aorta will be glued in that configuration and obstruct blood flow to the hind limbs. This also leads to how much you separate the abdominal aorta from surrounding tissue. Ideally, as minimal separation as possible is best. You need to separate the aorta upstream of the puncture point to place a thread for occlusion, but only as much more so as to see the puncture point is needed. Too much separation can lead to the vetbond glue enveloping the aorta and obstruction blood flow. Also, try not to use too much glue. If the surgical procedure is done smoothly the mortality in the hours to days following the implantation should be relatively low. 

However, I have had problems with the surgery being unsuccessful and the animal dying (excessive hemorrhage) during the procedure. The most common problem I seem to have is from the need to reuse BP devices to save money (these telemetry devices are expensive!). Recycled devices always have some vetbond glue left near the catheter tip (despite attempts to clean completely), which makes getting a tight seal around the puncture a lot more difficult. I have a had a number of animals where I think the puncture is well sealed but in reality is not with obvious outcomes.

As long as you make sure there is a good seal around the catheter puncture and the blood flow below the catheter tip is not obstructed then there shouldn't be many long-term complications. 

I hope this helped. If you have any other questions feel free to ask.

Hi Michael, thanks for sharing! I occlude above and below the puncture site. I typically separate the vessels just enough to wrap the occlusion threads beneath the aorta, (around a few millimeters). I find that the more I separate the more likely I am to encounter smaller bleeds. We also only use a few tiny drops of vetbond to secure the catheter, but also noticed that having too much caused issues. In addition, we secure a little piece of cellulose fiber patch the further secure the catheter. 

We aim to keep the time occluded under 2 minutes, with most animals only being occluded around 1 minute. However, I know that some people apply lidocaine to the vessel to dilate the aorta and minimize vasospasms. Do you have experience with this? I'm going to try on the next round of surgeries with the hope that the lower limbs will receive better blood flow after the catheter is in place. 

The paper I reference below cites that the aortic implant procedure only has a 57% success rate in mice. We're working with rats, but we also see high mortality rates that we aren't sure what the cause is. The animals that do die generally do so within 24-48 hours after implantation. As you said, these are expensive devices and re-using probes has some drawbacks, so we're really hoping to figure out how to keep all of our animals healthy.

"Applications of Telemetry in Small Laboratory Animals for Studying Cardiovascular Diseases" by Braga and Burmeister. 

Dear Khalid,

I'd be happy to discuss the techniques involved for the surgery and any post-operative complications you may be experiencing. What size and type of rats are you using? It might be easiest to arrange a conference call with you. Please feel free to contact me directly at [email protected] and we can plan a date/time.

Best Regards,

Heather Bogie, Senior Research Surgeon-Lead

DSI

Hi Khalid, Michael's response was very thorough, however he indicated that he too was having mortality issues especially with re-used implants. The single most important tip I can give you is to make sure you have completely stopped the leakage from the insertion site before applying the Vetbond.  This will allow you to use a minimum amount of glue which will avoid issues with the glue interfering with the blood flow in the aorta and it will reduce the glue residue on the catheter for future implantations.    

The duration of occlusion is not as important as getting the catheter properly positioned and using a minimum of glue. Lidocaine is an effective vasodilator for more peripheral vessels but I have not noticed an effect with the adult rat aorta.  

The article that you reference does not have a lot of carryover for the rat procedure. The aorta procedure is a lot more traumatic for the mouse than it is for the rat.  The recommended application for mouse BP is to advance the tip of the catheter into the thoracic aorta via the left carotid artery.  I would suggest reviewing the surgical implant videos for any of the DSI devices. They are available by contacting DSI Tech Support at [email protected] or by calling 800-262-9687.         

@ Heather and Daniel:

Our lab uses female wistar rats that are generally 220-250 grams. We've observed that this strain is more susceptible to issues from ketamine/xylazine anesthesia, but we've largely avoided those problem by adjusting the dosages. Most of the animals we lose recover from anesthesia. Are there other issues with the wistar strain that are important to consider? I think a conference call would be most fruitful, we will contact you to set one up. Thanks!

Dear Khalid 

My success rate in 99%. I developed a novel method for implantation of transmitter. You can go through my publication and try my method. If you have any question, please feel free to contact me.

Publication- simultaneous recording of.....

Good luck

Irfan