Orthostatic hypotension secondary to a suspected thymoma in a dog: a case report
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(2020) 16:388
CASE REPORT
Open Access
Orthostatic hypotension secondary to a suspected thymoma in a dog: a case report Jeremy Hansford*
and Natalia Henao-Guerrero
Abstract Background: This is the first case report description, to our knowledge, of a cranial mediastinal mass (suspected thymoma) causing orthostatic hypotension in a dog. Case presentation: A Labrador Retriever presented for urethral stent placement during cystoscopy secondary to transitional cell carcinoma diagnosis. During anesthesia, the patient had unexpected severe and poorly-responsive hypotension following a shift in position. Several days later, an intrathoracic mass was discovered, raising concerns that the position of the mass in relation to the great vessels and heart may have been the cause of the hypotension. The patient returned for a second stent placement, and computed tomography of the chest confirmed a cranial mediastinal mass, most suspected to be thymoma based on the results of cytology. The patient was kept in sternal recumbency, but when re-positioning to left lateral recumbency, there was a dramatic blood pressure drop that corrected with a return to sternal positioning. Conclusions: To our knowledge, orthostatic hypotension has not been described in relation to thymoma in dogs. Thymomas are rare; however, they may be associated with disease of autonomic dysfunction, such as myasthenia gravis, that may lead to orthostatic hypotension. This has been described within the human literature, and we hypothesize it was present in the currently described case. Concurrently, thymomas may grow to a substantial size and cause direct compression of the intrathoracic vasculature. As such, it should be on the differential list for poorlyresponsive hypotension following a shift in body positioning under anesthesia. Keywords: Thymoma, Orthostatic hypotension, Positional hypotension, Phenylephrine
Background Postural hypotension, also known as orthostatic hypotension, is described as autonomic dysfunction whereby the cardiovascular system’s adaptive mechanisms fail to respond to a reduction in venous return that is, in humans, associated with moving from the lying to upright position [8]. Prevalence in the human population is heavily age-dependent, occurring in over 30% of individuals greater than 70 years of age. Feelings of dizziness, light-headedness, and faintness are reported, and it is the second leading cause of syncope. Conversely, veterinary medicine has a paucity of * Correspondence: [email protected] Department of Small Animal Clinical Sciences, Virginia Maryland College of Veterinary Medicine, Blacksburg, VA 24061, USA
information regarding symptoms or prevalence of orthostatic hypotension in canines. Hellyer et al. [5], looked at monitoring nerve conduction in 8 dogs, finding that there was a relationship between stellate ganglionic (sympathetic) and vagal nerve activity cessation with a blood pressure decrease upon moving from lying to sitting-up position. However, no dogs exhibited any signs of syncope or collapse and only 39%
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