SURGERY
Article sponsored by Petcam ®
The Finer Points: Injecting Common
Sense into your Regional Anaesthesia
Strategy
By Hilal Dogan, BVSc, CCTP
I’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?”
Testicular blocks
Testicular blocks will make your neuters go more
smoothly and can help reduce the use of systemic
drugs.
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. 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.
.
vet360
Issue 05 | NOVEMBER 2018 | 4
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:
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).
Aminoamides
Lidocaine
Etidocaine
Prilocaine
Mepivacaine
Bupivacaine
Levobupivacaine
Ropivacaine
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.