Page 253 - Clinical Small Animal Internal Medicine

22 Systemic Hypertension 221

diseases associated with HT are diseases of older cats TOD is diagnosed as HT, antihypertensive therapy
VetBooks.ir (chronic kidney disease [CKD] and hyperthyroidism), should begin immediately.
Nonspecific screening of patients for HT is not recom-
the age distribution of hypertensive cats tends to include
mended. The prevalence of HT in healthy‐appearing ani-
a greater proportion of older than younger patients.
mals without causative disease is low, so many positive
diagnoses of HT in this patient group will be false posi-
History and Clinical Signs tives due to situational hypertension. Normal animals
may be tentatively diagnosed with HT when elevated BP
Patients with HT are typically identified by BP measure- is a result of agitation or anxiety during BP evaluation.
ments taken when a suspicious underlying disease or These animals may be identified as anxious during meas-
condition (e.g., proteinuria, hyperadrenocorticism) is urement, and repeat measurements later in the day or
diagnosed or suspected. Blood pressure should also be the following day after a period of acclimation may
monitored in any patient receiving drugs that can cause render more accurate results. Animals without causative
vasoconstriction, such as phenylpropanolamine, a disease or evidence of TOD may be accepted as normo-
common medication for urinary incontinence that is tensive if a confirmatory BP measurement after an initial
responsible for BP elevations in some dogs. Additional HT measurement is within normal range. In most cases,
HT patients are recognized when evidence of TOD animals with known causative disease or TOD and ini-
(e.g., ocular hemorrhage, neurologic signs, gallop heart tially elevated BP are confirmed as “true” HT if confirm-
sound) is identified. In these patients, further evaluation atory measurement is performed.
(see Table 22.1) after diagnosis of HT may reveal Commonly available methods to assess BP in dogs
the underlying cause. The clinical history of hyperten- and cats include direct measurement (via arterial punc-
sive patients may be consistent with the underlying ture or arterial cannulation) or indirect (noninvasive)
disease (e.g., polyuria/polydypsia with renal disease), methods, including Doppler sphygmomanometry and
reflect TOD (e.g., acute blindness due to retinal detach- oscillometry. Although high‐definition oscillometry
ment or obtundation due to increased intracranial (HDO) is now available, results may not be comparable
pressure) or reveal use of hypertensive medications to other methods and repeatable measurements may be
(e.g., phenylpropanolamine). Because of the high varia- difficult to obtain in awake cats. “Standard” oscillome-
bility of clinical signs, and because changes in mentation try (widely available in stand‐alone monitors or anes-
and behavior due to HT may be subtle or attributed to thesia monitors) or Doppler sphygmomanometry is
aging changes, a high level of suspicion for HT should currently recommended for clinical use.
be maintained regarding possible reasons for and signs Prior to BP measurement, the patient should be
of HT in clinical patients. allowed to relax with minimal restraint for 5–10 minutes
in a quiet area. The owner may help calm the animal
during the measurement if appropriate. Systolic BP is
Diagnosis typically used for clinical decision making and heart rate
should be recorded in all patients. Notation of heart rate
and any rhythm abnormalities may assist with full evalu-
Patient Selection and Set‐Up
ation of the patient; tachycardia during BP measurement
Blood pressure should be measured in dogs and cats may signal increased patient anxiety, or provide addi-
with diseases known to be associated with HT, and in tional information regarding underlying disease status
those animals showing evidence of TOD. In both species, (e.g., sinus tachycardia or arrhythmias in thyrotoxic
diagnosis or suspicion of renal disease (acute or chronic, cats). A gradually decreasing heart rate during measure-
proteinuric or nonproteinuric), adrenal neoplasias (e.g., ment repetitions may occur in a patient that is slowly
pheochromcytoma or aldosterone‐secreting tumors) relaxing, and additional measurements at the lower heart
and diabetes mellitus should lead to BP assessment. In rate may provide more accurate results than the initial
cats, evaluation of hyperthyroidism should include BP measurements at a higher heart rate.
assessment and BP should be reevaluated after success-
ful therapy for hyperthyroidism. Similarly, suspicion of Methods of Measurement
or diagnosis of hyperadenocorticism in dogs should
include evaluation of blood pressure. Direct Blood Pressure Measurement
Animals with evidence of TOD (see Table 22.1) Direct arterial BP measurement is performed by insert-
should have BP measured at the earliest opportunity ing a needle or catheter attached to a pressure transducer
regardless of underlying disease, so that intervention into a peripheral artery in a clinical patient to obtain
may ease or prevent further damage. If an animal with a pressure trace. Arterial cannulation using the dorsal