Page 244 - Small Animal Internal Medicine, 6th Edition

216 PART I Cardiovascular System Disorders

BOX 11.3
VetBooks.ir Approach to the Patient With Hypertension • Begin initial antihypertensive drug therapy (see

Suspect Hypertension or Disease Associated With
Hypertension (see Box 11.2, text) Table 11.1).
• Measure BP (see text). • Dogs: ACEI
• Use quiet environment. • Cats with proteinuric renal disease: ACEI
• Allow at least 5 to 10 minutes for patient to acclimate • Cats with hyperthyroidism: atenolol ± amlodipine
to environment (if animal is easily stressed, have owner • Other cats: amlodipine
present when possible). • If pheochromocytoma suspected, see p. 219
• Measure limb circumference, and use appropriate-size • If emergent therapy needed, see p. 218
cuff (use same cuff size for subsequent measurements as • Provide client education about the patient’s disease(s)
well). and potential complications, medication and
• Use consistent measurement technique. reevaluation schedules, potential adverse effects of
• Take at least five BP readings; discard highest and medication(s), and dietary concerns.
lowest, average the remaining readings. Patient Reevaluation
• Repeat BP measurements at other (one to three) times,
preferably on different days, to confirm diagnosis of • Recheck BP in 7 to 10 days for clinically stable
hypertension, except: patients.
• If acute, hypertension-induced clinical signs (e.g., ocular • Earlier reevaluation is advised for unstable patients, but
hemorrhage, retinal detachment, neurologic signs) full effects of antihypertensive drugs might not yet be
are present, begin therapy immediately (see p. 217; realized.
Table 11.1). • Obtain other tests as individually indicated.
• Screen for underlying disease(s) (see Box 11.1). • If BP control is not achieved with initial agent, try
• Obtain CBC, serum biochemistry tests, urinalysis, urine combination therapy (add ACEI or amlodipine).
protein-to-creatinine ratio. • Further control can be achieved with dose escalation of
• Obtain other data depending on individual amlodipine.
presentation: endocrine testing, thoracic and abdominal • Continue weekly to biweekly BP monitoring and
radiographs, ocular examination, ECG, underlying disease management. When BP (and
echocardiography, other tests as indicated. underlying disease) is controlled, gradually increase
time between recheck examinations.
If Hypertension Confirmed: • Recheck at least every 3 to 4 months because
• Manage underlying disease(s). medication requirements may change.
• Avoid drugs that can increase BP, if possible. • Recheck baseline laboratory data every 6 months or as
• Consider mildly to moderately reduced-sodium diet. individually indicated.
• Use weight-reduction diet if patient is obese.

ACEI, Angiotensin-converting enzyme inhibitor; BP, arterial blood pressure; CBC, complete blood count; ECG, electrocardiogram.

reduce BP. Dietary salt restriction is controversial. A high- treatment in people); however, a diuretic alone rarely is effec-
salt diet could contribute to development of hypertension in tive in hypertensive animals. Diuretics should be avoided in
some cats, although salt intake does not generally affect BP animals with renal disease because they can cause dehydra-
in normal animals (as is the case in people). Neurohormonal tion and exacerbate azotemia.
activation can occur in animals fed a very low-sodium diet; The ability to monitor BP is important when antihyper-
this can also increase potassium excretion, especially in cats tensive drugs are prescribed. Serial measurements are neces-
with renal dysfunction. However, moderate dietary salt sary to assess treatment efficacy and prevent hypotension.
reduction (e.g., ≤0.22%-0.25% sodium on a dry matter basis) Adverse effects of antihypertensive therapy usually relate to
could be useful in some cases. Although not expected to hypotension, manifested by lethargy or ataxia, or reduced
normalize BP by itself, salt restriction might enhance anti- appetite. Attaining initial BP control may take several weeks.
hypertensive drug effectiveness. Weight reduction usually is Monitoring can be done every 7 to 10 days to assess the
advised for obese animals. It is prudent to avoid prescribing efficacy of antihypertensive treatment in nonurgent cases.
drugs that can potentiate vasoconstriction (e.g., phenylpro- The dosage of antihypertensive drug(s) can be increased if
panolamine and other α 1 -adrenergic agonists). Glucocorti- control has not been achieved or reduced if systolic BP is less
coids and progesterone derivatives should also be avoided than ~110 mm Hg. Once satisfactory regulation is achieved,
when possible because steroid hormones can increase BP. A BP should be measured every 1 to 4 months, depending on
diuretic (thiazide or furosemide; see Chapter 3) might help patient stability. Some animals become refractory to therapy
by reducing blood volume in patients with volume expan- that was initially effective. Increased antihypertensive dosage,
sion (this is a common approach to antihypertensive adjunctive therapy, or a change of antihypertensive drug can