The finer points: Injecting common sense into your regional anesthesia strategy

July 18, 2018
Hilal Dogan, BVSc, CCTP
Hilal Dogan, BVSc, CCTP

Frequent Fetch dvm360 speaker Dr. Hilal Dogan practices medicine in Denver, Colorado. She started the Veterinary Confessionals Project as a senior veterinary student at Massey University in New Zealand.

Fetch dvm360 educators Mike Barletta, Tasha McNerney and Oriana Scislowicz take a full-circle approach to maximizing the effectiveness of local nerve blocks in veterinary practice.

Shutterstock.comI've always been afraid of doing local blocks for some reason-probably because I just never really got comfortable with them. So they usually aren't top of my mind in practice until somebody says, “We can do a local block.” And I think to myself, “Well, duh! Why didn't I think of that?”

Realizing my severe lack of local-block knowledge, I hightailed it to the lecture “Regional anesthesia: Minimize pain; maximize profit and efficiency” at a recent Fetch dvm360 conference. This was a Full Circle session, covering the clinical details (led by Mike Barletta, DVM, MS, PhD, DACVAA), application to the business side of practice (led by Ori Scislowicz, BS, LVT) and how to best leverage the team (led by Tasha McNerney, BS, CVT, CVPP, VTS [anesthesia and analgesia]).

Here are some of my key takeaways-I can't wait to practice them in clinics!

Testicular blocks

Testicular blocks will make your neuters go more smoothly and can help reduce the use of systemic drugs, says Dr. Barletta.

How local blocks work

Simply put, a local nerve block involves delivering a local anesthetic close to a key nerve via injection, says Dr. Mike Barletta, who discussed the pharmacology of local anesthetic drugs during his part of the Fetch dvm360 session.

To put it more precisely, local anesthetics close the sodium channel in the nerve, effectively blocking different types of nerve fibers, such as A-delta and C fibers. A-delta fibers are responsible for processing and transmitting sharp, acute, well-localized pain when activated, while C fibers are involved in slow-onset, burning, non-well-localized pain.

Local anesthetics fall into two classes-aminoamides and aminoesters. Here are some of the most commonly used:

Aminoamides

Lidocaine

Etidocaine

Prilocaine

Mepivacaine

Bupivacaine

Levobupivacaine

Ropivacaine

Aminoesters

Procaine

Benozocaine

Chlorprocaine

Tetracaine

Cocaine (yes, you read that right-Dr. Barletta says that in some countries cocaine is used for its vasoconstrictive action).

A simple way to remember the difference? If a drug name contains two i's it's most likely an aminoamide (which also contains two i's); if it has just one i it's an aminoester (only one i)-but this doesn't work in every case, so use the rule with caution.

I tried this once and had so much bleeding I vowed to never do it again because I was convinced the lidocaine was making this dog bleed like a hemophiliac on speed. I ended up sending him to the emergency room for “observation.” Yeah, so, I never used a testicular block again.

Then I realized I'd done it wrong. My mistake? I'd dripped the lidocaine into the incision site postneuter, happily thinking I was doing this dog a favor. According to the Fetch dvm360 experts, it's much more effective to use the lidocaine preneuter, injecting it directly into the testicle, and not to use it after you've already taken the testicles out!

Lidocaine does cause vasodilation and can increase bleeding; however, used appropriately, it will make your neuter go much more smoothly and cause your patient to feel less to no pain. You don't have to use a long-acting agent here, such as bupivacaine-most of your local anesthetic will end up in the trash when the testicles are discarded, McNerney says.

Sacrococcygeal blocks

Sacrococcygeal blocks will make your life much easier when it comes to blocked toms, tail amputations, and basically any surgery you're doing in the urogenital and perineal regions, says the Fetch dvm360 team. According to Dr. Barletta, the beauty of this block compared with an epidural is that your patient will retain its ability to walk immediately after the procedure.

Tips from the tech

Tasha McNerney insists that veterinary technicians can and should be doing local nerve blocks in general practice. She finds local hands-on labs to be the most useful way for techs to learn the process.

In McNerney's experience, local nerve blocks are most commonly used in dentistry-specifically the caudal mandibular block and the maxillary block. Her favorite anesthetic for these blocks is bupivacaine.

Other common applications include:

Retrobulbar blocks for enucleation

Testicular blocks for neuters, which can cut down on the need for inhalant anesthetic (McNerney usually uses lidocaine)

Incisional blocks-inject a local anesthetic along the incision site

Sacrococcygeal blocks for urethral obstruction in cats-using a 5/8-in needle, inject bupivacaine in the space where the tail goes up and down and wait 60 to 90 seconds. The anesthetic will affect the tail, anus, penis and perineum. And no, pets do not poop all over afterward.

McNerney singlehandedly convinced me to try this the next time I encounter a blocked tom that proves difficult to catheterize. “Instead of wrestling with the penis until it becomes a swollen, bloody mess, just sacrococcygeal-block that baby,” she says. “The penis pops right out.”

She also says to Instagram-story her when that happens and she'll do a happy dance for you. It's a win-win-win situation. You win, the cat wins and McNerney wins.

Building better business

Nerve blocks make a lot of sense for the business and management side of veterinary practice, says manager Ori Scislowicz. Here are the reasons:

Nerve blocks require a minimal equipment investment. For most blocks, all you need are a syringe and needle, although Dr. Mike Barletta does say you can use a nerve locator and ultrasound machine to help with the process.

Nerve blocks result in a smoother recovery for the patient and help pets maintain greater comfort throughout a procedure and the recovery period. This can set your practice apart if you educate clients about the details and even market these services more broadly.

If you empower techs to learn how to do nerve blocks, you build positive morale on your team and allow technicians to build their patient advocacy toolbox.

All in all, Scislowicz says, you'll have happier employees who are more skilled, and you'll have happier patients that are more comfortable.

What not to do

As I realized when I used lidocaine after a neuter, there are definite no-nos when it comes to local nerve blocks. Here are a couple:

1. Thou shalt not mix two anesthetic agents. For example, don't mix bupivacaine and lidocaine in hopes of achieving a middle ground in terms of speed of onset and duration of effect. They don't work that way, Dr. Barletta says-you'll end up with an in-between onset and duration, deriving the benefits of neither. It's better to use anesthetics sequentially when necessary: first a fast-acting agent, followed by a longer-lasting one-for example, at the end of the procedure for more postoperative analgesia.

2. Thou shalt not use epinephrine mixed with a local anesthetic on terminal blood supply areas. For example, don't use epinephrine on the tail area or ears because it causes vasoconstriction, and you may cause ischemic necrosis of the area because you cut off the blood supply for too long. 

An eternal conundrum

Last but not least, I leave you with the eternal sodium bicarbonate conundrum: to mix or not to mix? The Fetch dvm360 experts say yes, it's OK to mix sodium bicarb with your anesthetic to decrease the sting of a local block. However-and this is a big however-some local anesthetics precipitate out when mixed with sodium bicarb, so it's important to know which ones! Commit them to memory-they are bupivacaine and etidocaine.

With these tips blended together from the minds of a talented trio of experts, I am now ready to incorporate nerve blocks into my regular practice. Join me?

Dr. Hilal Dogan is the founder of The Vet Confessionals project. A frequent speaker at the Fetch dvm360 conferences, she is a certified clinical trauma professional (for humans) and a relief veterinarian with Veterinary System Services in Denver, Colorado. Mindy Valcarcel, clinical channel director for dvm360, contributed to this report.