Local and regional anesthesia techniques, Part 1: Overview and five simple techniques - Veterinary Medicine
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Local and regional anesthesia techniques, Part 1: Overview and five simple techniques
In this first article in a four-part series, these clinicians describe five easy-to-perform anesthetic techniques to improve patient care: infiltration anesthesia, splash blocks, digital nerve blocks, intravenous regional anesthesia, and soaker-type catheters.


VETERINARY MEDICINE


LOCAL AND REGIONAL BLOCKS

Strict adherence to sterile technique will prevent complications from infection. Always surgically prepare the skin, wear sterile gloves, and use only sterile needles, syringes, and catheters. Sterile skin preparation is not required for digital nerve blocks, but sterile needles and syringes should be used. To avoid complications from intravenous or intra-arterial injection of local anesthetics, always aspirate before injection. In addition, always calculate the maximum total dose for each patient, reducing the dose for debilitated, elderly, or neonatal patients.

Table 4 summarizes the indications, potential complications, drugs, dosages, and equipment required for each regional block technique described below.

Infiltration anesthesia


Figure 1. An incisional infiltration block administered after the closure of an abdominal incision in a dog. Four or five subcutaneous injections were made on each side of the incision, from the caudal to the cranial ends.
Infiltration anesthesia can be used during small laceration repair and small mass excision, as a line block before surgical incision, or before or after incision closure (Figure 1).27-30 The total volume of local anesthetic is deposited in multiple subcutaneous injections around the area to be desensitized. Always aspirate before each injection to ensure intravenous injection does not occur. Lidocaine injections are painful, so make subsequent needle insertions through desensitized skin. Sodium bicarbonate can be added to lidocaine in a 1:9 ratio of bicarbonate to lidocaine to reduce pain on injection.31,32

Splash blocks

A splash block refers to direct application of a local anesthetic to the site of interest, most commonly the body wall upon closure of the abdomen, the peritoneum intraoperatively, or the ovarian ligaments during an ovariohysterectomy. For this technique, 4 mg/kg of lidocaine or 2 mg/kg of bupivacaine is dripped from a syringe onto the area to be blocked, after flushing and suctioning the abdomen. These methods have been shown to reduce anesthetic requirements in some veterinary studies.28,29

Digital nerve blocks

These blocks are especially beneficial for onychectomies and will block the superficial 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.


Figure 2. The digital nerve block to provide effective analgesia for an onychectomy. Inject 0.2 to 0.4 mg/kg of the local anesthetic subcutaneously in three sites—lateral and proximal to the accessory carpal pad to block the dorsal branch of the ulnar nerve (A), medial to the accessory carpal pad to block the median nerve and palmar branch of the ulnar nerve (B), and at the dorsal-medial aspect of the proximal carpus to block the superficial branches of the radial nerve (C).
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.


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Source: VETERINARY MEDICINE,
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