Subcutaneous Transmitter Surgery Protocol- Implantation Protocol

Contents

1. Introduction

This protocol provides a detailed guide on the placement of electrodes and the surgical implantation of transmitters. It includes supply preparation, surgical procedures, and two methods of transmitter insertion.

Materials Required

• OSI Subucatenouse Transmitter and Electrodes (if applicable)
• Set screws (if applicable)
• Sterile surgical tools (forceps, scissors, scalpel)
• Burr drill
• Stereotaxic stand
• Anesthetic setup (3-4% isoflurane, ketamine, etc)
• Dental cement
• Vetbond or cyanoacrylate
• Hydrogen peroxide (diluted)
• Pain medication (ie. lidocane)
• Animale eye lubricant
• Sterile marker

Related Protocols

1. Sterilization

2. Device Preparation

1. Confirm device channel number and proper functionality before sterilization.
2. Sterilize all components of the implanted devices.
3. If inserting device through head incision (option 1):
   1. Make a general estimate as to how long your leads should be. You can measure one of your mice from the middl of its bak to the top of its head, and add length for wiggl room. If your leads are too long it could irritate the animal, if theyre too short, they tension could distrupt the electrodes or result in teh transitter being pulled forward too far.
   2. Connect accessories or depth electrodes before sterilization.
4. If inserting through back incision (option 2): Sterilize components separately; you will connect electrodes post-transmitter implantation in step 7.

3. Animal Preparation and Anesthetization

1. Weigh the animal.
2. Anesthetize the animal according to protocol. Perform to-pinch method to ensure proper anesthetization. Administer pain medication if necessary and aprt of your instiutional guidlines.
3. If you inserting the transmitter through the back/flank of the animal (Step 5 - Option B) you must shave the incision are on the back now. Make sure to wipe away any loose hairs.
4. Place the animal in a stereotaxic stand, connect to anesthetic, and apply eye lubricant.
5. Shave and disinfect the surgical site.

4. Head Incision and Sterilization

1. Make a vertical incision on the top of the head to expose the skull, clear of the eyes.
2. Remove connective tissue from the exposed skull (can use scissors and bone scraper).

5. Transmitter Insertion - Option A: Head Incision

*this method is only reccommended for our "Pup" A3048 SCT, or our side-mounted battery SCT.

How do I insert a Subcutaneous Transmitter into an animal? Where do I place a Subcutaneous Transmitter?
1. You will insert the transmitter through the back of the head incision
2. Lift the skin at the back of the head incision.
3. Next, you are going to creat a tunnel for the leads to pass through that allows the transmitter to sit in the back of the animal. To prevent irritation in the animals neck, we advise making the tunnel along the back of the animal, up until the neck, and then bringing the tunnel around the side of the neck (rather than directly over the spin) and through the head incision at a bit of an angle.
4. Use forceps to create a tunnel under the skin and above the muscle from the head incision to where the transmitter will lay, about half way around the back, in the mid-dorsal region. To create the tunnel you will clear away connective tissue that connects the muscle and the skin. The tunnel should be about as wide as the transmitter you are inserting.
5. Clear connective tissue between skin and muscle.
6. Gently insert the transmitter, guiding it down the spine to about ¾ of the way down the back.
7. Ensure the transmitter stays centered over the spine to avoid displacement.

5B. Transmitter Insertion - Option B: Back Incision

How do I insert a Subcutaneous Transmitter into an animal? Where do I place a Subcutaneous Transmitter?
1. Use tweezers to pinch and cut skin of mid-dorsal region. Incision must be large enough for the transmitter to fit through.
2. Making a pocket for the SCT
3. Clear connective tissue between skin and muscle where transmitter should lay. There are different schools of thought on where the transmitter should lay. We want to avoid the transmitter directly settling on the spine and also do not want it to fall to the front of the animal, as it will be able to claw it out. We advice taking care to not make too large of a pocket inbetween the skin and the muscle to avoid the transmitter moving too much after placement.
4. Next, you are going to create a tunnel for the leads to pass through that allows the transmitter to sit in the back of the animal. To prevent irritation in the animals neck, we advise making the tunnel along the back of the animal, up until the neck, and then bringing the tunnel around the side of the neck (rather than directly over the spin) and through the head incision at a bit of an angle.
5. Place transmitters where connective tissue was cleared.
6. Feed electrode leads up the back tunnel and pull through the head incision with tweezers.
7. Make sure leads are out of the way when drilling in next steps

6. Burr Hole Mapping and Drilling

1. Glue the skin of the scalp in place Vetbond to prevent bleeding and keep skin retracted for surgery.
2. Zero the stereotaxic stand using bregma.
3. Using your stereotaxic apparatus, locate the desired burr hole coordinates, and mark them on the skull with a sterilized pen.
4. Carefully drill burr holes at marked positions. Stop until there is a thin layer of bone covering the dura. Use a sterile syringe needle or tweezers to pock through to the dura.
5. If using set screws to anchor electrodes, confirm their fit in the burr holes.
6. Dab excess fluid with sterile cotton.

7. Electrode Placement

1. If you used Transmitter Insertion - Back Incision (option 2), you will connect and prepare your electrodes now, before inserting them into the brain. See our Electrode Surgery Notes for detailed descriptions of connection and insertion methods for our different electrodes
2. Insert electrodes into burr holes carefully according to the experimental plan.
3. If bleeding occurs, dab with a cotton bud/Q-tip.
4. Dry the exposed skull
5. Optionally apply Vetbond around burrholes (avoid brain contact).
6. Pull excess leads back into the tunnel. As little wire should be exposed through the scalp incision as possible. Make sure to leave slack in the leads under the skin. If the leads are pulled too tight between the trasnmitter and the electrodes, they can irritate the animal or cause dislodging of device parts.
7. Secure the leads in place where they exit the head incision with a bit of Vetbond.

8. Closing and Cementing

1. There are two methods for closing the open head incision
1. Suturing the head incision closed: This method is less common amongst our customers, as closing the incision over the electrodes and leads creates tension in the skin. THis can result in irritation and a subsequent opening of the head wound
2. Dental cement head fixture: this method, described below, involves creating a head fixture on the head of the animal with dental cement.
1. Secure burr holes in place with a bit of dental cement; allow curing.
2. Clip protruding electrode posts at designed breakpoints.
3. Cover over all exposed areas, metal, and leads with more cement, avoiding too much contact with the the animals fur and skin. The top of the dental cement may remain a bit tacky due to oxidation, it is fine to cover it with more dental cement anyway.
4. Allow cement to fully cure and trim excess.
5. Seal cement–skin interface with small amount of Vetbond.

9. Post-Surgical Care

• Allow several days of recovery in a clean, quiet environment.
• Monitor daily for:
  • Pain
  • Distress
  • Weight loss
  • Infection
• Consult your vet for protocols on antibiotic treatments.
• If the dental cement cap on the head becomes displaced, or if electrodes wired are exposed at all, please consult your vet as the animal will likely need to be culled.

Notes and Best Practices

• Document electrode placements and orientations meticulously.
• Ensure tunnels are just wide enough to prevent device migration.
• Label each SCT with animal ID and date of implantation.
• Some of our customers report the transmitter "fusing" to the skin of the animals back. If you notice the animal is not grooming where the transmitter is and the skin seems thin or stiff, move the transmitter around a bit with your fingers to detach it from the skin and then apply sudocream. While rare, we are unsure why this occurs. Additionally, customers have reported this issue does not occur with our thinner, side-mounted battery SCT.
• You can cohouse animals witht Subcutaneous Transmitter implants, but we advise letting the animals heal on their own for a few days before co-housing them