Normal systolic blood pressure via Doppler ultrasonography is 131 to 154 mm Hg in dogs and 115 to 162 mm Hg in cats.6
Clinician experience, patient anxiety, and patient familiarity with the environment can affect blood pressure readings. Patients should thus be given 5 to 10 minutes in a quiet area to acclimate to the environment before blood pressure is measured.
Veterinary oscillometric devices with specially designed cuffs should be used. Circumference of the patient’s limb should be measured to determine appropriate cuff size; cuff width should be 40% of the limb circumference in dogs and 30% of the limb circumference in cats. The cuff should be placed at the base of the tail, on a pelvic limb above the tarsus, or on a thoracic limb above the carpus. Hair should be clipped at the transducer location. Using ultrasonic gel, the transducer should be placed distally over the coccygeal artery at the base of the tail, the anterior tibial artery, or the ulnar artery on the palmar side of the distal aspect of the limb. Approximately 5 to 7 consecutive, consistent measurements should be obtained.14 Measurements with extreme variation should be discarded.
Environmental factors (eg, stress), disease processes (eg, secondary hypertension), and idiopathic factors can affect blood pressure. Kidney disease, hyperadrenocorticism, diabetes mellitus, obesity, primary hyperaldosteronism, and pheochromocytoma are associated with hypertension.14 CBC, serum chemistry profile, urinalysis, and abdominal ultrasonography are warranted in affected patients. Cardiac diagnostic investigation may be necessary to verify normal cardiac function. Complete eye examination should be performed, including Schirmer tear test, tonometry, fluorescein stain, and indirect ophthalmoscopy.17-22
Treatment is needed in patients with systolic blood pressure consistently >160 mm Hg via the Doppler oscillometric method. Patients with clinical signs of hypertension, a single measurement >160 mm Hg, and concurrent retinopathy lesions, encephalopathy, or chronic kidney disease also warrant treatment.14 Systolic blood pressure of 160 to 179 mm Hg is associated with moderate risk for damage to the kidneys, heart, brain, and eyes.14 Blood pressure >180 mm Hg indicates high risk for organ damage. Factors that can affect blood pressure and concurrent systemic disease should be considered when choosing a treatment protocol.
Effective early treatment of hypertension can resolve ocular clinical signs and result in vision recovery.4,23,24 Lack of treatment for ≥3 weeks generally results in a less favorable prognosis for recovery.24
Hypertension can be situational, secondary, or idiopathic. Once situational factors are ruled out, possible underlying disease or pharmacologic agents (eg, glucocorticoids, mineralocorticoids, erythropoiesis stimulants, phenylpropanolamine, phenylephrine, toceranib, sodium chloride) associated with secondary hypertension should be identified. Treatment for secondary hypertension should begin before the underlying condition is stabilized.
Once-daily treatment with antihypertensive medication is generally preferred, with the goal of gradual, consistent decrease in blood pressure to <140 mm Hg over several weeks.14 Rapid decrease in blood pressure should be avoided. If the first medication is not effective, the dose should be increased or consideration given to adding a second therapeutic agent. Therapy should be gradually adjusted if blood pressure remains between 140 and 160 mm Hg. Blood pressure <120 mm Hg may be associated with lethargy, tachycardia, syncope, and/or weakness, and treatment should be adjusted. Dietary salt restriction is generally not associated with a decrease in blood pressure.25,26
Hypertension in dogs is typically not an emergency. Angiotensin-converting enzyme inhibitors (eg, benazepril, enalapril, telmisartan) or calcium channel blockers (eg, amlodipine) are recommended. Amlodipine besylate is the first-choice treatment for cats with hypertension.27-29
Systemic Hypertension Medication Guidelines14
- Dogs: 0.5 mg/kg every 12 to 24 hours
- Cats: 0.5 mg/kg every 12 hours
- Dogs: 0.5 mg/kg every 12 to 24 hours
- Cats: 0.5 mg/kg every 24 hours
- Dogs: 0.1-0.25 mg/kg every 24 hours
- Cats: 0.625-1.25 mg per cat every 24 hours
- Dogs: 1-2 mg/kg every 24 hours
- Cat: 1-2 mg/kg every 24 hours