Veterinary Medicine - January 2009 - (Page 35)

Anesthesia techniques PEER-REVIEWED 5. A red rubber soaker-type catheter in place, along with a wound drain, in a dog that underwent radical excision of a soft tissue sarcoma. Note that the catheter is placed dorsally in the wound. A tacking suture holds the catheter to the skin, and the catheter will be wrapped to further secure it to the dog. Bupivacaine (1 mg/kg) will be administered through the catheter every six hours. cardiovascular collapse, or intraneural administration of local anesthetics and resulting nerve damage. Obtaining a catheter. Soaker-type catheters can be purchased commercially (Diffusion/Wound Catheter—MILA International; On-Q PainBuster Post-Op Relief System—I-Flow Corp) (Figure 4) or can be fashioned in a sterile manner from materials commonly found in the veterinary clinic. Commercial catheters are made of plastic tubing, often polyurethane, and typically range in length from 2.5 to 10 in. The fenestrated areas vary in length and are designed to spread local anesthetic over a predetermined area (5 to 22 cm). Homemade catheters are readily constructed intraoperatively.52,53 For instructions on how to make a soakertype catheter, see the boxed text on pages 36 to 37. The catheter can be made ahead of time and gas-sterilized with either hydrogen peroxide or ethylene oxide if facilities are available. Placing the catheter. Intraoperative placement of either a commercially manufactured or homemade soaker-type catheter is quick and easy, being similar in nature to placing a drain during closure. Place the catheter in the deepest layer of the wound, and make sure all fenestrations are within the muscle layers or subcutaneous tissues. Loose tacking absorbable sutures can be used in the deep layer, but the catheter should slide out easily for removal. If a drain is also to be placed, position the soaker-type catheter dorsally and the drain ventrally. The catheter can be tacked to the skin with suture to keep it in place and then bandaged as necessary (Figure 5). Soaker-type catheter placement can be accomplished outside the operating room as well when a painful lesion is not to be surgically addressed. Commercially available catheters are advantageous in such situations because they have tear-away applicators that allow for minimal tissue trauma during placement. Homemade versions could also be placed in such a situation but would require some tissue dissection to appropriately localize the catheter. Tunneling the catheter some distance in the subcutaneous tissues before exiting the skin will help provide stability to the placement. Elastomeric and electronic reservoirs that allow for continuous infusion of local anesthetic can be purchased from the same companies that supply commercial soaker-type catheters. Syringe pumps can also be used to provide continuous infusion. Lidocaine or mepivacaine are likely the safest choices for continuous infusion, and care should be taken to avoid toxic doses, especially in cats. Infusions of lidocaine or mepivacaine of 1 to 2 mg/kg/hr should be safe and effective in most cases. For intermittent administration, bupivacaine at 1 to 2 mg/kg is the best option because of its long duration of action (four to six hours). Catheters are typically left in place for one to three days, but can be left in longer if strict aseptic technique is followed. SUMMARY The techniques described above are easy to perform and require simple materials and drugs available in most small-animal veterinary practices. By providing preemptive and multimodal analgesia, reducing the need for systemic analgesics and anesthetics and the attendant side effects, and decreasing the perioperative VETERINARY MEDICINE January 2009 35

Table of Contents Feed for the Digital Edition of Veterinary Medicine - January 2009

Veterinary Medicine - January 2009 Contents Leading Off Letters Research Updates Idea Exchange A Modified Subconjunctival Enucleation Technique in Dogs and Cats Local and Regional Anesthesia Techniques Author Guidelines Product Preview CE Form/Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - January 2009

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