Veterinary Medicine - January 2009 - (Page 34)

Anesthesia techniques PEER-REVIEWED easily placed during a surgical procedure, such as a limb amputation or large tumor resection, just before closure. In addition, they can be positioned nonsurgically at the site of a lesion that is painful but cannot be resected or when a course of palliative care has been chosen. Efﬁcacy and adverse effects. The veterinary literature regarding the use of soaker-type catheters is limited, but human medical experience is extensive and, for the most part, positive. A 2007 study demonstrated the viability of soaker-type catheters in postoperative pain management in dogs, cats, and goats.36 In another veterinary study, continuous infusion of bupivacaine into normal dogs’ sti es for eight hours demonstrated plasma concentrations well below the toxic dose.37 Unfortunately, no studies have evaluated the ef cacy of continuous infusion of local anesthetics in veterinary patients with surgical or traumatic wounds. Results from human trials are largely encouraging, with most showing an improvement in patient pain scores or a decrease in opioid requirements,38-46 whereas others have not found a bene t.47-50 Of great interest is the reduction in chronic pain in people a minimum of four years after bone graft harvesting with the use of continuous bupivacaine infusion at the graft site for 48 hours.51 Divergent conclusions about the utility of soaker-type catheters may be due to different catheter placement depths (fascial layers vs. subcutaneous tissues), study end points (opioid consumption vs. length of hospital stay or patient satisfaction), innervation at various surgical sites (inguinal region vs. sternum), and other study design disparities. Few serious adverse effects attributable to local anesthetic in ltration are reported in veterinary patients. One case of lidocaine toxicosis with continuous infusion of 3 mg/kg/hr for three days has been described in a dog36; additional complications could include infection, hematoma formation, intravascular injection and subsequent 4. A commercially available soaker-type catheter and drug reservoir; the catheter has been inserted into the soft tissue over the humerus of a dog with osteosarcoma to provide palliative analgesia. achieve surgical anesthesia distal to the tourniquet, which will last up to 90 minutes. To avoid ischemic tissue damage, do not leave the tourniquet in place for more than 90 minutes.1,2 Sensation will return within ve to 10 minutes of removing the tourniquet, and residual analgesia is minimal (20 to 30 minutes), so provide other analgesics postoperatively.2 This technique provides a blood-free surgical site and lidocaine or mepivacaine doses below the toxic doses (Tables 2 & 4) will minimize the possibility of toxicosis should the tourniquet become dislodged. The mechanism by which local anesthetics produce intravenous regional anesthesia is unknown but probably results from local diffusion of the anesthetic and the blockade of nerve endings and nerve trunks and from leakage under the cuff, resulting in systemic Do not leave the tourniquet in place for more than 90 minutes. is also used with injectable antibiotics to obtain high tissue concentrations in a distal extremity.33,34 This technique is associated with few side effects as there is minimal systemic absorption of local anesthetic as long as the tourniquet remains in place and prevents blood ow to and venous return from the extremity.1,2 It is important to ensure that the tourniquet is not dislodged too early, as this will result in rapid plasma uptake of the anesthetic. Using absorption.1 Some systemic absorption is also thought to occur from interosseous vessels.35 Soaker-type catheter placement A soaker-type catheter, also referred to as a diffusion or wound catheter, is simply fenestrated tubing that is sterilely placed at a painful site for the continuous or intermittent administration of local anesthetics. Soaker-type catheters are 34 January 2009 VETERINARY MEDICINE

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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