Page 2215 - Cote clinical veterinary advisor dogs and cats 4th

1100.e4 Ethanol Ablation of Thyroid and Parathyroid Tumors

sudden hypotension is sensed during an blockades very close to nerves, nerve roots, ADDITIONAL SUGGESTED
injection (i.e., awake bupivacaine epidurals). and plexuses; these may afford safe, economi- READINGS
VetBooks.ir be replaced every 72-96 hours using aseptic Pearls Valverde A: Epidural analgesia and anesthesia in dogs
• The injection cap, filter, and dressing should
cal, and less technically challenging means
of providing analgesia.
and cats. Vet Clin North Am Small Anim Pract
technique in catheters that are routinely used
38:1205-1230, 2008.
(q 12h to q 8h treatments).
• Swelling or pain over the tunneled site or, • Epidural combinations including corticoster- Veterinary Anesthesia & Analgesia Support Group
(website). www.vasg.org/.
more important, over the catheter entry site oids have been used for treating inoperable
warrants removal of the catheter. Replace- IVDD, nerve impingement, and radiation Reproduced from the third edition in
ment should then be questioned; alternative therapy burn. They have also been used for unabridged form.
analgesic methods are suggested instead. palliative and terminal care.
• Neurostimulation and ultrasound guidance RELATED CLIENT EDUCATION
Alternatives and Their may provide easier placement at the LS SHEET
Relative Merits junction as well as more cranial placement
• General inhalant anesthesia: cardiorespiratory of substances and catheters. Consent to Perform General Anesthesia
depression; expense
• Systemic narcotic administration: side effects SUGGESTED READING AUTHOR: Andrea L. Looney, DVM, DACVAA
EDITORS: Leah A. Cohn, DVM, PhD, DACVIM; Mark S.
of gastrointestinal stasis, respiratory depres- Egger C, et al: Local and regional anesthesia tech- Thompson, DVM, DABVP
sion, and mild anxiety; expense niques. Part 4: epidural anesthesia and analgesia.
• Recent electrostimulation and ultrasound Vet Med 104:460-466, 2009.
techniques have allowed placement of

Ethanol Ablation of Thyroid and Parathyroid Tumors

Difficulty level: ♦♦ be performed bilaterally in cats. It can be • 1 mL of 96% ethanol should be prepared
considered as an alternative to surgery, with no air bubbles and attached to a 25- to
Synonyms radioiodine therapy, or methimazole in cats 27-gauge, 1 2 -inch syringe, and a low-flow
1
Percutaneous ethanol injection, PEI, chemical with unilateral hyperthyroidism. extension set should be placed between the
ablation needle and syringe and primed with ethanol
Equipment, Anesthesia before injection.
Overview and Goal • Intravenous or inhalant general anesthesia • In the case of a hyperthyroid cat, unilateral
Ethanol ablation under ultrasound guidance • High-quality ultrasound equipment with a hyperthyroidism should be confirmed based
has been used most commonly in veterinary high-frequency probe (at least 10 MHz) and on hormonal testing and nuclear scintigraphy.
medicine for the minimally invasive treatment an ultrasonographer experienced at evaluat- Once confirmed, the preparation is identical
of parathyroid tumors. Additional reported ing cervical structures and aspirating small to dogs with PHPTH.
uses of this procedure include benign thyroid nodules in an accurate fashion
tumors in cats, as well as other tumors, and • 96% ethanol Possible Complications and
renal, liver, and pancreatic cysts. The goal of • At least one 2.5-3 mL syringe Common Errors to Avoid
this procedure is to eliminate the detrimental • Low-flow extension set Possible errors:
secretory function of a benign endocrine tumor • 25- to 27-gauge, 1 2 -inch needles • Not offering owners surgery as an alternative
1
in a minimally invasive fashion. to injection. This is especially true if there
Anticipated Time is concurrent urolithiasis or another reason
Indications The procedure itself lasts seconds after the to have surgery.
For parathyroid ablation in cases of primary needle has been properly inserted into the para- • Attempting to inject a nodule that is too small
hyperparathyroidism (PHPTH). For thyroid thyroid nodule. Depending on the experience without the right equipment, experience, or
ablation, consider in cases of feline unilateral and expertise of the ultrasonographer, the size expertise and without proper anesthesia
hyperthyroidism or feline thyroid cysts. of the nodule, and the ultrasound equipment, • Not properly identifying the parathyroid
30 minutes to 1 hour is a reasonable time frame nodule and differentiating it from the
Contraindications for completion of the procedure. carotid artery, which can look very similar
• There are few contraindications to percu- in a cross-section ultrasonographic view
taneous ethanol injection (PEI) therapy in Preparation: Important of the cervical region. The nodule must
hyperparathyroid dogs. Successful therapy Checkpoints be round or elliptical in the longitudinal
does require a large enough nodule (typi- • The diagnosis of PHPTH should be con- plane and ideally should be documented
cally over 3-4 mm in diameter), a skilled firmed using ionized calcium and parathyroid to have no laminar flow using color-flow
ultrasonographer, and advanced ultrasound hormone (PTH) testing and by ruling out Doppler.
equipment. It should not be attempted if other causes of hypercalcemia (p. 519). • Assuming the tip of the needle is in the
these criteria are not met. • The dog’s neck should be examined nodule and the injection will be success-
• It should also not be attempted in multiple ultrasonographically, and the parathyroid ful without a proper test injection. After
nodules at the same time, especially bilater- nodule should be definitively located and the area has been infiltrated with a large
ally, for fear of transient laryngeal swelling measured. amount of ethanol around the nodule, it
and dysfunction after the injection. • The dog should be anesthetized and placed becomes very hard to visualize the nodule or
• PEI has not worked well in cats with in dorsal recumbency for the procedure, with the needle, and the attempt often must be
bilateral thyroid disease and should never the ventral aspect of the neck clipped. aborted.

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