Page 329 - Feline Cardiology

338 Section I: Systemic Hypertension

hypertension­related lesions (see Figures 21.5, 21.6). It given via syringe PO up to q 12 h; esmolol 50–75 µg/kg/
is considered safe, with few reported adverse effects. min constant rate IV infusion (CRI); labetalol 0.25 mg/
In humans and other species, beta blockers, ACE kg IV over 2 minutes, then repeated as needed up to total
inhibitors, and diuretics commonly are used for treating dosage ≤3.75 mg/kg followed by 25 µg/kg/min CRI; or
systemic hypertension. In the cat, these are considered enalaprilat 0.2 mg/kg as needed up to q 1–2 h (Brown
second­line therapies, if at all. ACE inhibition has pro­ et al. 2007).
vided convincing benefits in the experimental setting
but does not lower arterial BP as consistently as amlo­ MONITORING
dipine. An ACE inhibitor is not routinely used as mono­ Subsequent BP measurements follow the initial diagno­
therapy for systemic hypertension in cats, but it may sis. The interval is dictated by the presence or absence
have beneficial effects in hypertensive patients when its of signs of target organ damage; by the magnitude of
primary use is for the patient’s proteinuric renal disease hypertension; by the ability to control the inciting
or congestive heart failure. Similarly, such beta blockers disease; and by client wishes and abilities (physical,
as atenolol are routinely and safely used in cats, but their financial, emotional, etc). Typical intervals range from a
efficacy for reducing an elevated blood pressure is infe­ few days or 1 week for cats with severe target organ
rior to that of amlodipine. Like ACE inhibitors, beta damage that are recovering and are being discharged
blockers are used in hypertensive patients only when a after inpatient care, to 3–4 months for patients with
concurrent disorder primarily warrants their use (e.g., clinically stable BP and well­controlled underlying dis­
hyperthyroidism). Finally, diuretics recently have orders. Essentially all cats with confirmed systemic
resurged in human hypertensive therapy, despite the hypertension should have their BP measured whenever
activation of the renin­angiotensin­aldosterone system they come to medical attention, including when they
caused by their use. For this reason, and because many
Systemic Hypertension diuretics have not been investigated extensively in man­ OUTCOME AND PROGNOSIS
seem well.
hypertensive cats have compromised renal function,
agement of feline systemic hypertension and are not
recommended for this purpose.
The largest study of survival in cats with systemic hyper­
tension to date assessed 141 hypertensive cats. Cats were
Hypertensive Crisis
Management of severely hypertensive states has been
followed; 89 died and were thus included in survival
reviewed recently (Brown 2009; Brown et al. 2007). treated with amlodipine in an open­label manner and
statistics. Of the variables studied, including age, serum
These are cats in whom ocular or intracranial lesions are creatinine, serum phosphorus, and degree of hyperten­
manifest or have previously been manifested in conjunc­ sion (BP measurements), only proteinuria was corre­
tion with systemic hypertension, and who have persis­ lated with survival (Jepson et al. 2007). Hypertensive
tent arterial BP levels >180 mm Hg (and often much cats with lower urine protein:creatinine ratio (e.g., <0.2)
higher). The white coat effect must be reduced as much before or after treatment with amlodipine lived longer
as possible for an accurate reading; failure to do so poses than cats with higher urine protein:creatinine ratio (e.g.,
a risk of hypotension or hypotensive crisis during acute >0.4). The same study identified that treatment with
antihypertensive treatment. The goal of treatment is not amlodipine was associated with a significant reduction
normalization of the BP but rather an acceptable in urine protein:creatinine ratio.
decrease that reduces the risk of target organ damage
with minimal risk of overtreatment (hypotension
causing renal, cerebral, or coronary ischemia). The REFERENCES
current consensus in human medicine is a reduction in Boldface font indicates key references.
BP of at most 25% within minutes to 1 hour of identi­ Belew AM, Barlett T, Brown SA. Evaluation of the white­coat effect
fication of the emergency, and, if the patient is stable, in cats. J Vet Intern Med 1999;13:134–142.
subsequent reduction of BP to no lower than 160/100– Binns SH, Sisson DD, Buoscio DA, Schaeffer DJ. Doppler ultrasono­
graphic, oscillometric sphygmomanometric, and photoplethys­
160/110 over the next 2–6 hours (Labato 2009). Such mographic techniques for noninvasive blood pressure measurement
guidelines seem appropriate for feline patients, pending in anesthetized cats. J Vet Intern Med 1995;9:405–414.
species­specific data. Drugs used singly (virtually never Brown CA, Munday JS, Mathur S, Brown SA. Hypertensive encepha­
in combination) for the management of hypertensive lopathy in cats with reduced renal function. Vet Pathol 2005;42:
642–649.
crisis include amlodipine 0.25 mg/kg PO q 24, with Brown S, Atkins C, Bagley R, Carr A, Cowgill L, Davidson M, Egner
dosages up to 0.5 mg/kg being used in some cases with B, Elliott J, Henik R, Labato M, Littman M, Polzin D, Ross L,
caution; hydralazine 2.5–5 mg/cat dissolved in water and Snyder P, Stepien R. Guidelines for the identification, evaluation,