Animal Care Services

General Pre-Operative and Post-Operative Practices; applicable to each transmitter implantation described below

Preoperative physical evaluation of the animal will be conducted.  This includes visual inspection of the animal and an assessment of their behavioral status.  The animal should be alert and behaving normally, and should have a smooth coat and clear eyes.  Any animals with physical or behavioral abnormalities will be brought to the attention of the ACS veterinary staff before having an implant placed.

Anesthesia will be induced by placing the animal within an induction chamber and introducing 5.0% isoflurane gas.  Anesthesia will be maintained by 1.0 – 3.0 % isoflurane delivered by nose cone.  Toe pinch (withdrawal) reflex will be used to determine that an acceptable surgical plane of anesthesia has been achieved before beginning the surgical procedures.
Beginning approximately 5 minutes before the completion of these procedures, gas anesthesia will be turned down by 0.5% each minute.

Ophthalmic ointment is applied to both eyes, after induction of anesthesia.

For all animals, body temperature is maintained throughout these procedures and until fully recovered from anesthesia by use of a re-circulating water heating pad and is monitored using a rectal probe. 

The fur is shaved from the surgical site.  When animal size permits, a 1.0 cm border will be shaved around the intended incision site.  The surgical site will be disinfected with germicidal surgical scrub, beginning at the center of the incision site and proceeding toward the periphery.  The scrub solution will be removed with a 70% alcohol (or sterile water) rinse, again beginning at the center of the incision site and proceeding toward the periphery.  This scrub will be repeated twice more, for a total of three alternating applications of both scrub and alcohol.   Following this initial surgical site preparation, a germicidal solution will be applied to the site in the same manner.  The germicidal solution will not be rinsed off.  The surgical site is isolated with sterile drapes.    All implants are gas sterilized. 

All surgical instruments, drapes, swabs etc. are autoclaved before use.  The transmitter cannula and housing are sterilized either by ethylene oxide gas or by a commercial liquid sterilant, specifically 2.0% activated glutaraldehyde.  If liquid sterilants are used the implant materials will be rinsed (twice) in sterile water for 30 minutes prior to implantation. 

Rehydration at the end of surgery is by subcutaneous administration of 10-20 mL/kg BW of sterile isotonic NaCl for both rats and mice. 
Post-operative analgesia will be Buprenorphine, 0.01-0.05 mg/kg SQ, q12h, for rats, and 0.05-0.1 mg/kg SQ, q12h, for mice.  The initial dose of Buprenorphine will be administered either before the surgery is started or when skin closure is begun.  Analgesic therapy will be continued every 12 hours for a minimum of 48 hours, and then as needed for the control of pain.

All rats/mice are closely monitored during the surgery and for 1 hour after recovery from general anesthesia.  Rats/mice are then monitored twice daily for 2 days and are checked for; weight gain, general appearance, grooming behavior, production of feces, and integrity of the incision sites.  Rats/mice exhibiting any signs of pain or distress will be euthanized immediately, i.e. failure to gain weight, anorexia, fever/shivering, breakdown at the incision sites. 

Should euthanasia become necessary, it will be performed by which ever method is described in the IACUC approved protocol to which the animal is assigned

Skin sutures/staples are removed 7 – 10 days after surgery. 

Rat Transmitter: The C40 transmitter consists of a blood pressure sensor probe housed within a polyurethane catheter (size 0.7 mm) and a reusable battery-powered electronics module, which is enclosed in a biocompatible silicone elastomer housing sized for rats weighing 150-500 gm.  The catheter is permanently attached to the C40 transmitter module.  The electronics module is cylindrical in shape, (27mmX12mmX8mm).  It is manufactured by the DSI Company, St Paul, MN.

Mouse Transmitter: The C10 transmitter consists of a blood pressure sensor probe housed within a polyurethane catheter (size 0.5 mm) and a reusable battery-powered electronics module, which is enclosed in a biocompatible silicone elastomer housing sized for the mouse (20-60gm).  The catheter is permanently attached to the C10 transmitter module.  The electronics module is cylindrical in shape, (13mm X 10mm X 6mm).  It is manufactured by the DSI Company, St Paul, MN.

Rat model / Abdominal Aorta Cannulation and Intraperitoneal Transmitter Housing Implantation

The midline of the abdomen is opened, through both the skin and the peritoneum.  This incision is approximately 3.5 cm long.  The intestines are wrapped in warm saline-soaked gauze and displaced laterally to allow visualization of the aorta.  Two drops of lidocaine are applied to the artery area.  The aorta is dissected from the adjacent vena cava.  A ligature tie is placed around the aorta just below the left renal artery (proximal ligature).  A second tie is placed just above the bifurcation of the iliac arteries (distal ligature).  In most cases, the ligation will last no longer then 3 minutes. A 21 gauge needle (with the tip bent at a 90 degree angle) is used to make a puncture into the aorta.  Iris scissors and fine tipped forceps may be used to make an incision instead of this needle puncture technique.  Approximately 1.5 cm of catheter is introduced cranially into the aorta.  The needle is removed and then the catheter is anchored in place with tissue adhesive followed by a 5 x 5 mm cellulose patch that is secured in place with tissue adhesive. After the tissue adhesive on the cellulose patch has dried (generally 15-20 sec.), the distal ligature is released.  The proximal ligature is slowly released while observing for small blood leaks. Minor hemorrhaging can be controlled with direct pressure using swabs and/or a drop of tissue adhesive.  Ligature material is removed and discarded.
The transmitter is aligned parallel to the long axis of the body, on top of the intestines, with the catheter directed caudally.  The transmitter is anchored to the peritoneal wall using a simple interrupted suture pattern with 3-0 non-absorbable monofilament suture material.  A non-absorbable suture is necessary in order to keep the transmitter anchored in place for extended periods of time.  Closure of the peritoneum is accomplished with this set of interrupted sutures as well.  The skin is then sutured with 3-0 non-absorbable monofilament suture or surgical staples.
Post-operative analgesia will be administered as described above.
Post-operative procedures will be followed, as described above. 

Mouse model / Thoracic Aortic Cannulation via the Carotid Artery and Subcutaneous Transmitter implantation

Animals are placed on their backs on a heated surgical surface with forelimbs secured using tape and the head held parallel to the body by a small length of suture material looped around the upper incisors and anchored to the surface. This allows easier access to the region to be dissected.
A ventral midline skin incision is made from the lower mandible caudally to the sternum (3 cm).  The thyroid and parathyrod glands are gently separated using sterile cotton swabs.  Apply 2 drops of lidocaine to the artery area. The artery is isolated using fine forceps, with care being taken to avoid disturbing the nerve fibers running parallel to the artery. Two non-absorbable ligatures (6–0 non-absorbable monofilament) are passed under the vessel and used for both ligation and retraction. The cranial ligature is placed just below the bifurcation of the interior and exterior carotid arteries and is used to ligate the artery. The caudal ligature is placed loosely about 0.5 cm below the cranial tie and will used to secure the catheter into the artery.  Gentle tension is applied to both ligatures to retract and lift the vessel slightly as needed to maintain working access.  A 25 gauge needle (with the tip bent to a 90 degree angle) is used to make a tiny puncture in the carotid artery just below the cranial ligature. Iris scissors and fine tipped forceps may be used to make an incision instead of this needle puncture technique.  After the puncture/incision has been made, the catheter is introduced caudally into the artery.  Fine forceps are used to hold the vessel puncture/incision open.  Temporarily release tension on the caudal ligature and slide the catheter beyond it. The catheter is advanced until the small notch on the tubing (~10 mm from the tip) is at the vessel puncture/incision site.  Inserting the catheter up to this landmark notch ensures the critical placement of the pressure-sensing tip just inside of the thoracic aorta.  The caudal ligature is secured around the artery so that it seals the artery wall around the catheter.  The cranial ligature is tied around the catheter to provide additional security to the catheter placement.
Through the same ventral neck incision, a subcutaneous pouch is formed for placement of the transmitter itself along the animal’s left flank. Using a pair of blunt dissecting scissors the skin is gently dissected free from underlying tissue starting at the left neck region and proceeding caudally and dorsally to form a "pocket" along the left flank.  It is important that the pocket be made sufficiently large to house the transmitter without unduly stretching the skin and yet small enough to keep transmitter secure.  The transmitter is slipped under the skin and down into the pocket along the flank as close to the right rear leg as possible. A small drop of tissue adhesive is placed on the catheter in the left neck region to further secure the device.
The neck incision is closed using 6–0 non-absorbable monofilament sutures.  
Post-operative analgesia will be administered as described above.
Post-operative procedures will be followed, as described above. 
Pressure necrosis can result from the presence of the implant.  Mice will be monitored for hair loss, redness, chewing or scratching to the area where the transmitter is located.  Any of these signs would result in immediate euthanasia of the animal. 

Rat model / Femoral Artery Cannulation w/ Subcutaneous Housing Implant

Make a 2.0 cm incision in the left groin area above femoral artery. Using blunt dissection, form a subcutaneous pocket up towards the area between the caudal edge of the ribcage and the most cranial extension of the knee's range of motion. Ideally, the subcutaneous pocket should be just large enough for the transmitter body to be inserted into the pocket. If the pocket is not made large enough, the skin will be stretched too tight across the contours of the transmitter and pressure necrosis may result. Once placed in the pocket, secure the transmitter housing by passing 5-0 non-absorbable monofilament suture through the tissues surrounding the pocket entrance and drawing together the entrance in a purse-string fashion.
Using blunt dissection technique, carefully separate the tissue connecting the femoral artery, vein and saphenous nerve.   Irrigate the femoral artery with 2% lidocaine to dilate the vessel and prevent vasospasms. Using curved forceps to isolate the artery, lift gently and open the forceps to maximize the length of vessel available to be catheterized (~10 mm if possible).  Pass three lengths of 5-0 non-absorbable monofilament suture underneath the isolated artery section.  Two will be positioned proximal to the intended puncture site and one distal to the site.  Secure the most proximal ligature gently to serve as occlusion.  Secure the most distal ligature firmly to serve as a permanent ligation. The middle ligature can be loosely tied at this point. They will also serve to retract the vessel as needed to maintain working access.  
Make an incision through approximately the upper 40% of the vessel diameter with iris scissors as close to the distal ligature as possible.  Hold the artery wall at the incision site with fine Swiss Jeweler Style forceps and the catheter tip with the cannular forceps.  Carefully insert the catheter tip into the artery, and advance it toward the heart, up to the proximal ligature. Temporarily release tension on the proximal occlusion suture and slide the catheter beyond it, advancing it past the iliac region to the bifurcation of the abdominal aorta.  Tie the middle ligature suture and proximal ligature around the artery so that they seal the artery wall around the catheter.  Release the retraction tension on the distal ligature. Secure the distal ligature around the exposed catheter to stabilize the catheter placement.
The skin is then sutured with 3-0 non-absorbable monofilament suture or surgical staples.
Post-operative analgesia will be administered as described above.
Post-operative procedures will be followed, as described above. 
Pressure necrosis can result from the presence of the implant.  Rats will be monitored for hair loss, redness, chewing or scratching to the area where the transmitter is located.  Any of these signs would result in immediate euthanasia of the animal. 

Rat Femoral Artery Catheterization Procedure with Abdominal Transmitter Placement

Make a 2.0 cm incision in the left groin area above femoral artery.
Access the peritoneal cavity with a midline abdominal incision (~3.5 cm).   Pierce the peritoneum with a large bore syringe needle (14g.) from the femoral side into the peritoneal cavity, taking care not to damage organs. Leave the needle in place momentarily. Place the implant body in the peritoneal space with the catheter oriented caudally and thread the catheter tip through the syringe needle so that it passes through the peritoneum. Withdraw the needle leaving the catheter in place.  
Blunt dissect a passage subcutaneously from the abdominal incision to the incision in the left groin.  Place a trocar through the passage and advance the catheter to the groin incision.  Remove the trocar leaving the catheter tip visible within the groin incision site.
Using blunt dissection technique, carefully separate the tissue connecting the femoral artery, vein and saphenous nerve.   Irrigate the femoral artery with 2% lidocaine to dilate the vessel and prevent vasospasms. Using curved forceps to isolate the artery, lift gently and open the forceps to maximize the length of vessel available to be cannulated (~10 mm if possible).  Pass three lengths of 5-0 non-absorbable monofilament suture underneath the isolated artery section.  Two will be positioned proximal to the intended puncture site, and one distal to the site.  Secure the most proximal ligature gently to serve as occlusion.  Secure the most distal ligature firmly to serve as a permanent ligation. The middle ligature can be loosely tied at this point. They will also serve to retract the vessel as needed to maintain working access. 
Make an incision through approximately the upper 40% of the vessel diameter with iris scissors as close to the distal ligature as possible.  Hold the artery wall at the incision site with fine Swiss Jeweler Style forceps and the catheter tip with the cannular forceps.  Carefully insert the catheter tip into the artery, and advance it toward the heart, up to the proximal ligature. Temporarily release tension on the proximal occlusion suture and slide the catheter beyond it, advancing it past the iliac region to the bifurcation of the abdominal aorta.  Tie the middle ligature suture and proximal ligature around the artery so that they seal the artery wall around the catheter.  Release the retraction tension on the distal ligature. Secure the distal ligature around the exposed catheter to stabilize the preparation.
The transmitter is aligned parallel to the long axis of the body, on top of the intestines, with the catheter directed caudally.  The transmitter is anchored to the peritoneal wall using a simple interrupted suture pattern with 3-0 non-absorbable monofilament suture material.  A non-absorbable suture is necessary in order to keep the transmitter anchored in place for extended periods of time.  Closure of the peritoneum is accomplished with this set of interrupted sutures as well. 
The skin of both the abdominal and inguinal incisions is then sutured with 3-0 non-absorbable monofilament suture or surgical staples.
Post-operative analgesia will be administered as described above.
Post-operative procedures will be followed, as described above.