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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 Publication of the National Association of Veterinary Technicians in America 15 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- 16 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. CH 3 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. CH 3 CH 3 N HN Dexmedetomidine Publication of the National Association of Veterinary Technicians in America 17 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. 18 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. ® *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. Publication of the National Association of Veterinary Technicians in America 19