Veterinary Medicine - January 2009 - (Page 33)

3. A Bier block provides excellent anesthesia to the extremity distal to the tourniquet as long as the tourniquet remains tightened. Lidocaine is being injected slowly into an intravenous catheter. Digital nerve blocks These blocks are especially bene cial for onychectomies and will block the super cial branches of the radial nerve, the median nerve, and dorsal and palmar branches of the ulnar nerve, providing effective analgesia of a distal extremity.3,30 Because of its long duration of action, 0.5% bupivacaine is the drug of choice for this block, and it is often combined with lidocaine for immediate onset of the block. Do not use epinephrine because of the potential for ischemia in extremities. Inject 0.2 to 0.4 mg/kg of local anesthetic subcutaneously in three sites (Figure 2): lateral and proximal to the accessory carpal pad, medial to the accessory carpal pad, and at the dorsal-medial aspect of the proximal carpus. Alternatively, a simple ring block proximal to the carpus will block these nerves, and, although hindlimb onychectomy is discouraged, a ring block can be used for this procedure as well. In addition, individual digits can be blocked by injecting the local anesthetic subcutaneously in a ring proximal to the digit. Because it requires restricted movement for a period of time, dogs often tolerate the procedure with moderate sedation, while cats often require heavy sedation. Sicker patients often tolerate this technique with minimal sedation, as they usually accept restraint for longer periods. This technique is indicated for mass removal, wound management, surgical biopsy, or fracture repair of a distal extremity. For this technique, place an intravenous catheter into a distal vein of a limb, usually the cephalic vein or the saphenous vein. Place a rubber tourniquet, or a blood pressure cuff attached to a sphygmomanometer, around the limb proximal to the intravenous catheter, and tighten it to completely occlude arterial blood ow (pressure must be greater than systolic arterial pressure) (Figure 3). The advantage to using the sphygmomanometer and blood pressure cuff is that you can measure the pressure required to occlude arterial ow, avoiding excessive pressure that may cause direct tissue trauma and ischemic damage. Limb exsanguination with an Esmarch bandage is often described in reference texts for this technique1,2 but, in our experience, is not required in dogs or cats to produce an effective block. Inject lidocaine or mepivacaine into the catheter (Table 4). Never use bupivacaine, as intravenous administration of bupivacaine is always contraindicated. Five to 10 minutes are required to Intravenous regional nerve blocks Intravenous regional anesthesia, or a Bier block, is a rapid and reliable method for producing short-term (< 90 minutes) anesthesia and muscle relaxation of a distal extremity and can be performed in anesthetized or sedated animals.2,3,30 VETERINARY MEDICINE January 2009 33

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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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