Locoregional analgesia for pain management in veterinary medicine

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Pet owners want to know that their pets are comfortable during visits to the clinic. Fortunately, locoregional analgesia is a well-explored method of pain management in veterinary medicine. At the dvm360® Directions in Veterinary Medicine conference, Tasha McNerney, BS, CVT, CVPP, VTS (Anesthesia & Analgesia) and Bryce Dooley, DVM, MS, DACVAA presented on local blocks and the advantages of these types of anesthetics.¹

How it works and common types of analgesia

Dooley stated, “[Local anesthetics] exist in a solution in both an unionized form and an ionized form, meaning sometimes they have H+ on them and sometimes they don’t.” Only the unionized version, however, can diffuse across the nerve membrane due to its lipid solubility, then re-ionize to block sodium channels. This causes the inhabitation of nerve impulse formation, leading to loss of sensation locally or regionally near the blocked nerves.

The presenters explained Lidocaine and bupivacaine can both be administered for local and nerve blocks, making them the two most common local anesthetics in the United States. Lidocaine’s main selling point is that it can be used intravenously with a notably quick onset. Bupivacaine, on the other hand, can take 5 to 10 minutes to set in. However, while lidocaine typically provides just an hour of pain relief, the effects of bupivacaine can last up to 6 to 8 hours.

When professionals combine lidocaine and bupivacaine, Dooley said they are typically trying to create “a superblock,” merging lidocaine’s quick onset and bupivacaine’s longer duration. This is highly inadvisable as mixing these anesthetics alters the pH, which can cause a longer onset time, a shorter duration, and less blockade, Dooley explained.

Most blocks can be performed as long as the practitioner has anatomical knowledge. Toxicity, while a possibility, shouldn’t dissuade practitioners from administering local anesthetics. Dooley argued that commonly feared medication methods, like epidurals, are harmless so long as “you know your anatomy [and] know what you’re looking for.”

While there are many benefits of locoregional analgesia, veterinary professionals should practice good judgement. No 2 situations and no 2 pets are the same, so no matter the anesthetic technique, the application should be approached with individualized care. McNerney noted that if a practice is passionate about elevating its standard of care, it should familiarize itself with locoregional analgesia. “You don’t have to be an anesthesiologist to do excellent pain control,” McNerney said.

Reference

1. Dooley SB, McNerney T. It's not a pain! Pain management and regional analgesia options. Presented at: Directions in Veterinary Medicine; Miami, Florida. May 19-20, 2023.