Laboratory Animal Science Center (BUMC)
Subcutaneous (SC) Implant in Rodents
Indications
This procedure may be used for subcutaneous implantation of osmotic pumps, drug capsules or pellets, tumor fragments, or other materials that are free of microbial contaminants.
Materials
- anesthetic agent(s)
- animal clippers with #40 surgical prep blade
- alcohol, betadine, &/or other suitable skin prep solutions
- sterile surgical gloves
- sterile surgical instruments:
- scalpel blade w/wo handle
- hemostat
- forceps
- needle holder or skin stapler
- implantable material or device, free of microbial contaminants
- sterile suture material, tissue glue, or skin staples
Methods
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Anesthetize the animal with an appropriate anesthetic agent. During anesthetic induction with injectable agents, the animal should be placed in a cage by itself to prevent disturbance and injury caused by other animals. Consult lab animal anesthesia and monitoring guidelines.
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Remove the anesthetized animal's hair at the surgical site. Use an animal clippers with a surgical (#40) blade to obtain a close shave without nicks in the skin. An area 3-4 times the size of the implant should be clipped. Implants are best tolerated in the dorsal subcutis slightly caudal (posterior) to the shoulders. An appropriately inserted implant in this site will not interfere with manual restraint, impinge upon vital organs, or restrict normal activities of the animal. This site is also relatively inaccessible to manipulation by the animal, although it is subject to scrutiny by cagemates.
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Prepare the clipped skin for surgery using a surgical scrub &/or alcohol. Do not contaminate the surgical site after scrubbing.
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With a sterile scalpel blade, make an incision cranial (anterior) to the site where the implant will rest. Incision length of approximately 1.5 times the diameter of the implant will facilitate insertion. The incision will be perpendicular to the long axis of the implant.
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Insert the closed hemostat into the incision. Open the jaws to bluntly dissect the subcutaneous tissue. Withdraw the hemostat slightly, close jaws, and repeat the blunt dissection steps until a suitable implant pocket has been created. The pocket should be slightly wider than the implant diameter and about 1 cm longer than the implant. A larger-than-implant pocket will reduce the tensile stress on the pocket closure.
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Place a suitably prepared implant into the subcutaneous pocket. (For mini-osmotic pumps, insert the delivery portal end of the pump first. Positioning the delivery port into the closed end of the pocket will minimize test agent leakage through the incision and potential interference with wound healing.) If the pocket is not large enough to hold the implant comfortably, remove the implant and enlarge the pocket as described above.
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Close the incision with sutures, tissue glue, or skin staples. Skin edges should be closely opposed to minimize healing time. Try to position the skin edges exactly as they were prior to surgery. Skin edges should meet and not overlap. Tissue death and sloughing due to inadequate vascular perfusion will result if too much skin is bunched with a skin staple or suture. Do not permit the edge of the incision to curl under the adjacent skin, as any buried epidermal surface will be sloughed.
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Leave the closed incision clean and dry. Do not swab the site with alcohol or any other agent that will damage tissue. (General rule: Don't douse exposed tissue or broken skin with anything that you would not be willing to put in your eye!) If you need to clean the suture line, use normal (0.9% NaCl) saline or dilute (3%) hydrogen peroxide. Do not anoint the closed incision with antibacterial ointment or cream—the antibiotics will be quickly removed by the animal's grooming and may cause GI upset.
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Place the animal in a clean, dry cage in a warm place. Supplemental heat may be helpful, particularly if anesthesia is prolonged. During recovery from anesthesia, the animal should be placed in a cage by itself to prevent disturbance, injury, &/or death caused by other animals.
More information on drug delivery options can be obtained from sources such as:
Alzet Corporation (implantable osmotic pumps) (877)922-5938
Innovative Research of America (drug pellets) 800-421-8171
Training Videotape Available
A videotape that demonstrates osmotic pump implantation is available for viewing in the LASC office. Training in these procedures is also available from LASC. Please call 638-4086 for more information.
