Page 1057 - Cote clinical veterinary advisor dogs and cats 4th

Hypotension, Systemic 523.e3

Technician Tips
Dog breeders should be counseled to avoid
VetBooks.ir during pregnancy. Hypospadias may be heri- Diseases and Disorders
administration of androgens or progestins
table, and affected animals should be neutered.

SUGGESTED READING
Romagnoli S, et al: Disorders of sexual differentiation
in puppies and kittens: a diagnostic and clinical
approach. Vet Clin North Am Small Anim Pract
36:573-606, 2006.
ADDITIONAL SUGGESTED
READINGS
Grossman J, et al: Use of a preputial circumferential
mucosal flap for hypospadias management in a
Boston terrier. J Small Anim Pract 53:292-296,
2012.
Jurka P, et al: Hypospadias in six dogs. Vet Rec
HYPOSPADIAS Penile hypospadias. Inguinal region of a male dog (cranial is to the left). The opening of 164:331-333, 2009.
the glans penis is deviated, as indicated by the lateralized location of the catheter (toward the patient’s left). Pavletic M: Reconstruction of the urethra by use
(Reprinted with permission from Jurka P, et al: Hypospadias in six dogs. Vet Rec 164:331-333, 2009.) of an inversed tubed bipedicle flap in a dog with
hypospadias. J Am Vet Med Assoc 231:71-73, 2007.
AUTHOR: James A. Flanders, DVM, DACVS
EDITOR: Michelle A. Kutzler, DVM, PhD, DACT

Hypotension, Systemic

BASIC INFORMATION PHYSICAL EXAM FINDINGS ○ Pericardial effusion
• General (see History, Chief Complaint) ○ Arrhythmias (tachyarrhythmia or
Definition • Weak or thready pulses, pale mucous bradyarrhythmia)
A mean systemic arterial pressure (MAP) < membranes, delayed capillary refill time ○ Suppression of contractility (e.g., anesthet-
60 mm Hg and a systolic arterial pressure (SAP) • Dogs likely are tachycardic, whereas cats may ics, beta-blockers, systemic inflammatory
< 80-90 mm Hg display tachycardia or bradycardia. Animals response syndrome)
with hypotension due to decompensatory • Hypovolemic
Epidemiology shock are bradycardic. ○ Hemorrhage
SPECIES, AGE, SEX • Hypothermia can exacerbate hypotension, ○ Gastrointestinal or urinary fluid losses
Affects all species, ages, and both sexes, although partially due to bradycardia. ○ Burns
predispositions may exist for an underlying • Findings related to an underlying disease, ○ Hypoadrenocorticism
causative disease. Cats may be more commonly such as heart murmur, external/internal • Vascular tone
affected with hypotension than dogs during hemorrhage, or evidence of infection (fever ○ Sepsis
critical illness. or injected mucous membranes) are possible. ○ Anaphylaxis
○ Drugs (e.g., phenothiazines, angiotensin-
RISK FACTORS Etiology and Pathophysiology converting enzyme [ACE] inhibitors,
Critical illness, sepsis, hypovolemia, severe heart Systemic blood pressure (BP) is the product calcium channel blockers, nitroprusside,
failure, hypothermia, anemia, acidemia of cardiac output (CO) and systemic vascular some anesthetic agents)
resistance (SVR). SVR is determined by tone ○ Decreased cortisol production (e.g.,
Clinical Presentation of the precapillary arterioles that regulate hypoadrenocorticism, critical illness related
HISTORY, CHIEF COMPLAINT organ-specific perfusion. Vasodilation results adrenal insufficiency)
Signs of hypotension are typically vague and in a decreased SVR. CO is the product of • Decreases in BP trigger immediate sympa-
can include depressed mentation, weakness, heart rate (HR) and stroke volume (SV). SV thetic response by carotid sinus and aortic
lethargy, vomiting/diarrhea, respiratory distress, is determined by preload, afterload, and cardiac body receptor detection of hypotension.
and/or collapse. Specific clinical signs may contractility. Diseases that result in systemic The result is stimulation of vascular smooth
be related to the causative disorder, such as hypotension typically affect one or more of muscle cells and direct vasoconstriction.
cough and respiratory distress in a dog with these parameters (i.e., SVR, HR, intravascular With persistent, often low-grade hypotension/
hypotension due to primary cardiogenic causes, volume, and contractility). hypoperfusion (e.g., long-standing cardiac
and overlap often occurs between signs of Causes of systemic hypotension: disease), the immediate sympathetic response
hypotension and signs due to its underlying • Cardiogenic is lessened, and other mechanisms are
cause. Hypotension may also develop under ○ Cardiomyopathies (dilated, hypertrophic, activated to raise BP, resulting in vasocon-
anesthesia. unclassified) striction, increased intravascular volume,

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