In the January issue of Veterinary Medicine, we presented an overview of the drugs used for local and regional anesthesia and then described five techniques—infiltration anesthesia, splash blocks, digital nerve blocks, intravenous regional anesthesia, and soaker-type catheters—that can greatly enhance the analgesic management of veterinary patients (see "Local and regional anesthesia techniques, Part 1: Overview and five simple techniques"). In this article, we discuss several more techniques you can begin using immediately in practice to alleviate pain, reduce stress, and optimize recovery in your patients—intra-articular stifle blocks, intercostal nerve blocks, intrapleural analgesia, and various options for forelimb analgesia including a recent alternative to the traditional brachial plexus nerve block, the paravertebral brachial plexus block. We also discuss electrical nerve stimulation and the use of a nerve locator to improve the success rate of peripheral nerve blocks.
Table 1: Indications and Drug Dosages for Local and Regional Anesthesia Techniques
For each technique, perform a sterile scrub, wear sterile gloves, and use only sterile needles, syringes, and catheters. Strict adherence to aseptic technique will reduce complications from infection. An overview of each technique is presented in Table 1. The onset of the blockade and duration of analgesia depend on the local anesthetics chosen and the use of adjunctive agents.
INTRA-ARTICULAR STIFLE BLOCK
This block provides analgesia to a joint before (preemptive) or after surgical intervention. It is most commonly used to block the stifle but may be performed in other joints.1-3 To block the stifle joint, flex the joint slightly, and apply digital pressure to the medial side of the patellar ligament. Insert the needle on the lateral side of the patellar ligament midway between the patella and the tibial tuberosity, and direct it medially and toward the intercondylar space of the tibia (Figure 1). After aspirating to ensure correct placement (joint fluid is often identified), inject the chosen drug or drugs.
Figure 1. The landmarks for performing an intra-articular stiﬂe block.
Lidocaine or bupivacaine are commonly used; morphine or buprenorphine can also be used alone or, more commonly, in combination with a local anesthetic.4,5 Clonidine, an alpha2 agonist, is effective in people as an adjunct to local anesthetics when administered intra-articularly,6 and the alpha2 agonist fadolmidine was shown to suppress peripheral arthritic pain when administered into the stifle joints of rats.7 As outlined in the previous article, adding alpha2 agonists, opioids, or both to a local anesthetic may enhance efficacy and extend duration of regional anesthetic techniques. Bupivacaine, with or without an opioid or alpha2 agonist, is most commonly used in intra-articular blocks, with onset in about 30 minutes and a duration of action, when given alone, of four to six hours.
INTERCOSTAL NERVE BLOCKS
Intercostal nerve blocks provide effective analgesia after a lateral thoracotomy or in patients with rib fractures.1,2,8 The intercostal nerves descend in the intercostal space along the caudal border of each rib, associated with the ventral branches of the intercostal artery and vein. For a lateral thoracotomy, the block can be performed immediately after anesthetic induction and surgical preparation of the chest wall (preemptive analgesia) (Figure 2), or it can be performed before closing the chest wall, allowing visualization of the nerves and blockade of both the dorsal and ventral branches (Figure 3).
Figure 2. Positioning of the needles for a preoperative intercostal block.