Download Dexmedetomidine - National Association of Veterinary Technicians

Continuing Education
Dexmedetomidine:
Analgesic A junct
Your new favorite
Tasha McNerney BS, CVT
This program was reviewed and approved
by the AAVSB RACE program for 1 hour of
continuing education in jurisdictions which recognize AAVSB RACE approval. Please contact
the AAVSB RACE program if you have any
comments/concerns regarding this program’s
validity or relevancy to the veterinary profession.
Objective: After reading this article,
participants will have an increased
understanding of dexmedetomidine,
both as an anesthetic and analgesic. In
addition, readers will be able to identify
several efficient and effective routes of
administration.
Many clinics throughout the world use
dexmedetomidine for sedation. However,
did you know that dexmedetomidine is also
labeled as an analgesic? This is a fact that
often gets overlooked in practice. Dexmedetomidine is the active S-enantiomer of
the α-2 agonist, medetomidine. Removal
of the inactive molecule, levomedetomide
results in dexmedetomidine being a “purified” product with increased potency
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Continuing Education
Dexmedetomidine, continued
and decreased stress on the liver. Many
practices are familiar with dexmedetomidine as an α-2 agonist sedative that is
reliable, fast-acting, and reversible with
atipamezole. But now, more practices are
beginning to expand their use of dexmedetomidine to take advantage of its analgesic effects as well. Dexmedetomidine is
non-narcotic and can be very useful when
combined with opioids for a multimodal
analgesic protocol. Dexmedetomidine also
comes with the benefit of being a time
saver. It’s an unscheduled sedative/analgesic so the clinician does not have to worry
about time spent in drug logs.
Dexmedetomidine’s main effect is to produce sedation and both somatic and visceral
analgesia. Analgesic effects of dexmedetomidine are principally due to spinal anti-nociception via binding to non-noradrenergic
receptors (heteroreceptors) located on the
dorsal horn neurons of the spinal cord. This
mechanism of action inhibits the release
of norepinephrine (a catecholamine
released by the adrenal gland and part
of the fight-or-flight response), and
therefore prevents transmission of
further nerve impulses. This provides
both sedation and analgesia.
Dexmedetomidine was approved for
human use in 1999 as a continuous rate
infusion to provide sedation in the intensive care settings.1 In human medicine
there has also been the recent anecdotal
report of dexmedetomidine use in obstetric
analgesia. The report asserts that, because
of its high lipophilicity, dexmedetomidine is
retained in placental tissue and passes less
readily into the fetal circulation and is less
susceptible to cause harmful fetal bradycardia when compared to other sedatives.2
Dexmedetomidine has also been studied
more recently for the management of pain
and sedation in pre-mature neonates. This
study demonstrated the achievement of
adequate sedation when neonates were
given a continuous infusion of dexmedeto-
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The NAVTA Journal | Aug/Sept 2015
Continuing Education
midine as compared to another group that
were given infusions of fentanyl. Patients in
the dexmedetomidine group required less
adjunctive analgesic and sedation medications compared to the fentanyl group,
suggesting that dexmedetomidine effectively provides both anti-nociception and
hypnosis in premature infants.3
Although dexmedetomidine can be used
alone, it produces an increased level of
analgesia when combine with opioids. Opioids and α-2 agonists such as dexmedetomidine work synergistically with opioids
increasing both the intensity and duration
of analgesia. When dexmedetomidine is
used as part of the pre-operative combination, lower levels of inhalant anesthetics
are required. When dexmedetomidine is
used as part of the post-operative analgesic protocol, rescue doses of opioids are
used less frequently.
Dexmedetomidine is also being used frequently as an in hospital constant rate infusion for rough recoveries and breakthrough
analgesia. Constant rate infusion of low
dose dexmedetomidine (1 to 2 mcg/kg/hr);
can be used in severely painful or anxious
patients to provide sedation and analgesia.
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Dexmedetomidine can also be added to a
preexisting opioid infusion for increased
sedation and analgesia. Because
dexmedetomidine has the potential to
cause severe bradycardia and hypotension, these patients should be monitored
very closely by a dedicated recovery
technician. A loading dose of at least 0.5
µg/kg (0.0005 mg/kg) dexmedetomidine IV
should precede the initiation of the dexmedetomidine CRI.4
Epidural use of dexmedetomidine can enhance the analgesic effects of other agents
given epidurally. Besides the previously
mentioned action at heterotropic spinal
receptors, dexmedetomidine also produces
analgesia by stimulation of cholinergic
interneurons when given epidurally.1 It acts
synergistically with epidural opioids, improving the quality and duration of analgesia, and recent human studies have shown
that the addition of 2 μg/kg dexmedetomidine epidurally to 2.5 ml of intrathecal
bupivacaine prolongs the duration of analgesia, and decreases the requirement of
rescue analgesics in patients undergoing
lower-limb orthopedic surgery.5 It should
be noted that dexmedetomidine is highly
lipophilic, and is rapidly absorbed from the
The International Veterinary Academy of Pain Management has many
resources available for practitioners
who want to increase their knowledge
of various analgesics drugs and protocols. The IVAPM website is also a
valuable resource for finding certified
veterinary pain practitioners (CVPP)
in your area. For more information on
dexmedetomidine and how you can
incorporate this sedative/analgesic in
your practice visit www.IVAPM.org or,
join the Facebook group Veterinary
Anesthesia Nerds to discuss this and
other anesthesia and pain management topics.
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Dexmedetomidine
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Continuing Education
Dexmedetomidine, continued
epidural space, which can lead to systemic
levels of the drug.
Dexmedetomidine is gaining some ground
recently as more practices are experimenting with using it transmucosally in felines, in
addition to the intra-muscular and intravenous routes. Transmucosal dosing allows
even fractious cats to receive sedation and
analgesia. Often, cats given transmucosal
dexmedetomidine are not at a surgical
plane of anesthesia but are sedate enough
to allow physical exams, blood draws, and
IV catheter placement. Dexmedetomidine
can also be combined with buprenorphine
and given via the oral-transmucosal route.6
Oral dosing can range from 20-40mcg/kg.
It should be noted that dexmedetomidine
has serious cardiac side effects and seriously affects cardiac output. Dexmedetomidine should be reserved for patients
that are heart healthy and have no exercise
intolerance. α-2 agonists are not intended
for animals with respiratory or cardiovascular compromise.
References
1. Gaynor J.S. & W.W. Muir (eds), Handbook of Veterinary Pain Management, 2nd
Edition, Elselveir, St.Louis, MO
2. Grosu, I. & Lavand, P. (2010) The Use of
Dexmedetomdine for Pain Control. F1000
Medical Reports v.2 2010 http://www.ncbi.
nlm.nih.gov/pmc/articles/PMC3026617/
3. O’Mara, Kelian, et. Al. (2012) Dexmedetomidine vs Standard Therapy with Fentanyl
for Sedation in Mechanically Ventilated Premature Neonates. J Pediatric Pharmacology
& Therapy Jul-Sep; 17(3): 252-262
4. Zeltman, Phil. (2013) CRI’s: Base Drug
Choice on Patient Need, Health. Veterinary
Practice News, June 2013. Pg 35
5. D Jain, RM Khan, D Kumar, N Kumar
(2012) Perioperative effect of epidural dexmedetomidine with intrathecal bupivacaine
on haemodynamic parameters and quality
of analgesia. Southern African Journal of
Anaesthesia and Analgesia Vol. 18 (2)
6. Santos, L.C. Et Al. (2010) Sedative and
cardiorespiratory effects of dexmedetomidine and buprenorphine administered
to cats via oral transmucosal or intramuscular routes. Vet Anaesth Analg. 2010
Sep;37(5):417-24.
About the Author:
Tasha McNerney BS, CVT
Tasha has worked at Rau Animal Hospital in Glenside, PA for ten years as an O.R. / Anesthesia technician. Her areas of interest include
sighthound and brachycephalic anesthesia as well as pain management. Tasha has been a featured speaker on various anesthesia and pain
management topics at conferences such as Atlantic Coast Veterinary Conference, AVMA conference and the Wild West Veterinary Conference. In July of 2012 Tasha authored an article for the NAVTA journal entitled “Anesthesia in the Sighthound Patient”, and several articles for
“Fetch” a blog dedicated to pet parents. Tasha is also the author of the Surgical Pain Management chapter for the textbook “Pain Management for Veterinary Technicians” (Shaffran and Goldberg, eds.). Tasha is also currently working on obtaining her CVPP.
In 2013 Tasha created the Facebook group Veterinary Anesthesia Nerds, which has almost 6000 members participating in education and
exchange of ideas in all aspects of veterinary anesthesia and pain management.
Tasha recently partnered with Firstline magazine to produce a video blog series for technicians entitled “Coffee on the Couch” which showcases various technician job avenues and encourages technician growth and career development.
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The NAVTA Journal | Aug/Sept 2015
Continuing Education
Dexmedetomidine Quiz
6. Dexmedetomidine can be used as an
epidural injection combined with opioids.
a. True
b. False
1. What inactive molecule was removed
from medetomidine to create the
“purified” product?
a. Dexmedetomidine
b. Levomedetomidine
c. Carbon
d. Xylazine
7. Which of the following is NOT
considered an appropriate route of
administration of dexmedetomidine?
a. Intra-muscular injection
b. Intravenous constant rate infusion
c. Tramsmucosal administration
d. Per os, mixed with food
2. Dexmedetomidine has which of
the following properties?
a. Sedation
b. Analgesia
c. Both A and B
d. None of the above
8. Prior to starting a continuous infusion
of dexmedetomidine, what loading dose
of dexmedetomidine should be given
intravenously?
a. 1 mg/kg IV
b. 10 mg/kg IV
c. 5 mcg/kg IV
d. 0.5mcg/kg IV
3. Which type of analgesia is
dexmedetomidine responsible
for producing?
a. Somatic analgesia
b. Visceral analgesia
c. Both A and B
d. None of the above
9. Which of the following drug classes
can be used in combination with
dexmedetomdine?
a. Opioids
b. Inhalant Anesthetics
c. Both A and B
d. None of the Above
10. When dexmedetomidine is used as
part of the pre-operative combination,
what happens to the required levels of
inhalant anesthetics?
a. Increased requirements of inhalant
anesthetics
b. Decreased requirements of inhalant
anesthetics
c. No change in requirements of inhalant
anesthetics
4. Norepinephrine is a catecholamine
released by what organ?
a. Pituitary gland
b. Adrenal gland
c. Liver
d. Lymph nodes
5. Which of the following is
NOT a common side effect of
dexmedetomidine administration?
a. Bradycardia
b. Hypotension
c. Sedation
d. Excitability
This article is worth one continuing education credit and will be accepted for
grading until Sept 1, 2017. To receive credit, please complete the quiz online
at www.VetMedTeam.com. There will be a $5 fee for each quiz.
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*Due to updates and changes authorized by NAVTA, the online quiz may not be the same as
the printed exam within The NAVTA Journal. Read each question thoroughly and answer it as it
appears in the online exam. Please do not simply copy your answers from the printed version.
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