Exam 4 - Systemic Hypertension Flashcards
what is the formula for blood pressure?
BP = HR X SV X SVR
blood pressure is the product of what?
cardiac output & systemic vascular resistance
what is the gold standard for measuring blood pressure? how is it done? what does it measure? is it commonly done?
direct blood pressure measurement - measured via catheterization of an artery & electronic transducer
measures systolic, diastolic, & mean arterial pressure
not commonly done - not practical for screening & management of hypertension
what is the best way to measure blood pressure in cats & small dogs? how is it done?
doppler sphygmomanometry - indirect, non-invasive way to measure
uses the frequency changes between emitted ultrasound & returning echos from moving blood cells or vessel walls to detect blood flow in an artery
why is oscillometry not the best way to measure blood pressure in cats?
it underestimates when blood pressure is high
how does oscillometry measure blood pressure?
microprocessor detects pressure oscillations that result when flow is occluded
what blood pressure reading is used for clinical assessment?
systolic blood pressure
where do you place the cuff for reading blood pressure?
midway between the elbow & carpus
in the tibial region
base of tail
what is the protocol that should be used for measuring blood pressure in a small animal patient?
same individual should take all measurements - allow 5-10 minutes for acclimation, keep patient calm & motionless & not sedated - need to be gently/minimally restrained in ventral or lateral recumbency with the cuff at the base of the heart
discard first measurement - 5-7 consecutive values are recorded & averaged - if they trend down over time, take measurements until plateau is reached & then record 5-7 measurements
written record should include person taking measurements, cuff size & site, values obtained, rationale for excluding any values, & mean result
how is pressure cuff size determined for blood pressure readings? what happens if the wrong size is used?
cuff width should be 30-40% of the limb circumference at the cuff site
if too small - falsely high readings
if too big - falsely low readings
how is doppler used to get blood pressure readings?
good contact between doppler probe & skin achieved with alcohol to dampen hair & plenty of ultrasound gel
inflate cuff 20-40 mmHg above the point where blood flow is no longer heard
what patients should you measure blood pressure on?
in patients with signs of target organ damage
in patients with conditions known to be associated with hypertension
in patients on meds/following toxin ingestion
screening of aging patients
T/F: sighthounds have higher normal ranges of blood pressures than other breeds
true
what were definitions of hypertension developed based off of?
risk of target organ damage
what defines normotensive?
minimal target organ damage risk - systolic blood pressure < 140 mmHg
what defines prehypertensive?
low target organ damage risk - systolic blood pressure 140-159 mmHg
what defines hypertensive?
moderate target organ damage risk - systolic blood pressure 160-179 mmHg
what defines severely hypertensive?
high target organ damage risk - systolic blood pressure > 180 mmHg
in general, hypertension should be documented as persistent for how many occasions?
needs to be documented as persistent for 2 or more occasions
over 4-8 weeks for patients with low or moderate target organ damage risk
over 1-2 weeks for patients with high target organ damage risk
T/F: hypertension with evidence of target organ damage warrants treatment after a single measurement session
true
what is white coat hypertension?
increase in blood pressure that occurs in clinic in a patient that is otherwise normotensive - important to differentiate from true hypertension
how is idiopathic hypertension diagnosed?
diagnosis is suspected when reliable measurements demonstrate persistent increase in blood pressure with a normal CBC, chem panel, & urinalysis
can be difficult to rule out subclinical kidney disease - also hypertension can cause pu/pd
what is secondary hypertension?
> 80% of cases & more common than idiopathic!!!
increased blood pressure due to a concurrent illness, medication, or toxin - hypertension may persist after treatment of the underlying condition
hypertension can occur with any IRIS CKD stage, so is severity of hypertension related to severity of CKD?
nope
what is the pathogenesis of hypertension from chronic kidney disease?
involves sodium & water retention, activation of the RAAS, sympathetic nervous system, & structural changes to arterioles, & endothelial dysfunction
what is the pathogenesis of hypertension in cushingoid dogs?
glucocorticoid induced production of angiotensinogen by the liver & exaggerated sympathetic nervous system response
can cause mild to moderate dose-dependent hypertension
what is the pathogenesis of hypertension in hyperthyroid cats?
may involve increased sensitivity to catecholamines & direct effect of thyroid hormone on cardiac myocytes
what are some toxins associated with causing hypertension?
ephedrine/pseudoepinephrine
cocaine
methamphetamine
5-hydroxytryptophan
T/F: hypertension can cause retinal detachment & acute onset blindness
true
what is seen on physical exam that clues you into hypertension?
ocular lesions are common in both dogs & cats
CNS signs from hypertensive encephalopathy
systolic murmur/gallop sounds associated with left ventricular hypertrophy
epistaxis due to hypertension-induced vascular changes
what should you include in your diagnostic work up for a hypertensive patient?
BUN, creatinine, SDMA, usg - assess kidney function
assess for proteinuria
look at liver enzymes & electrolytes
look at blood glucose
what is the purpose of doing a urine protein:urine creatinine ratio in a hypertensive patient?
need to quantify the proteinuria
when may you do an echo in a cat with hypertension?
left ventricular hypertrophy secondary to hyperthyroidism!!! but may be indistinguishable from feline idiopathic hypertrophic cardiomyopathy
what organ damage occurs to the kidneys from hypertension?
hypertension associated with proteinuria
anti-hypertensive medication decreases severity of proteinuria!
hypertension results in histological renal injury - sclerosis
what organ damage occurs to the eyes from hypertension?
retinopathy/choroidopathy!!! retina & choroid have separate blood supplies & either can be affected
acute onset blindness, exudative retinal detachment, retinal hemorrhage/edema,tortuosity, perivascular edema, papilledema, vitreal hemorrhage, hyphema, secondary glaucoma, & retinal degeneration
what organ damage occurs to the brain from hypertension?
encephalopathy or stroke - neuro signs reported in 1/3-1/2 of cats with hypertension
signs - lethargy, seizures, acutely altered mentation, altered behavior, disorientation, & central vestibular signs
in hypertensive animals that become acutely blind, is vision restored after blood pressure is corrected?
not commonly restored
what organ damage occurs to the cardiovascular system from hypertension?
can result in concentric left ventricular hypertrophy
left sided heart failure rarely develops (but can happen after fluid therapy is started)
aortic aneurysm - rare
hemorrhage - epistaxis or stroke
what is your first step before deciding to treat a patient for hypertension?
you must exclude situational hypertension!!!!
if there is an underlying condition causing hypertension in a patient, do you just treat that without anti-hypertensive medications? why?
no - treating the underlying cause often doesn’t resolve it!!!! don’t without treatment!!!
what is the optimal goal for treating a hypertensive patient? what is your minimal goal?
optimal - < 140 mmHg
minimal - < 160 mmHg
if you are managing a patient for hypertension with medication and they come in with a systolic blood pressure < 120 mmHg with weakness, syncope, & tachycardia, what do you do?
need to lower the dose of the anti-hypertensive!!!
once blood pressure is controlled in a hypertensive patient, how often should you schedule rechecks?
at least every 3 months
how do you treat a patient that is prehypertensive with a condition that is predisposed to causing hypertension?
need to monitor them every 6 months
how do you treat a patient with gradual onset hypertension without target organ damage?
gradual persistent decrease in blood pressure should be achieved over several weeks, so begin therapy & recheck after 7-10 days
adjust meds as needed & recheck again after 7-10 days
monitor every 4-6 months once target blood pressure is reached
be aware of potential for acute exacerbation of azotemia when combining anti-hypertensive therapies
how do you treat a patient with systolic blood pressure > 200 mmHg and/or hypertension with target organ damage?
begin therapy - monitor blood pressure & clinical signs closely in the first 24-72 hours & adjust meds as needed
what is considered to be a hypertensive emergency? what is the goal of treatment? what is required?
acute ocular or neurological target organ damage
goal is an incremental decrease in blood pressure because an acute drop can result in hypoperfusion
treatment should be immediate & aggressive & requires in hospital 24 hour care
why do you not want to just use amlodipine for a hypertensive dog? how do you counter act this?
preferential dilation of the afferent arteriole may increase glomerular pressure which may be detrimental - may worsen proteinuria
offset this by concurrent administration of ace inhibitors
what is the mechanism of action of amlodipine? what patients do we commonly use it in?
calcium channel blocker! potent peripheral arteriolar vasodilator that acts directly on vascular smooth muscle with minimal cardiac effects
commonly used in cats - may also decrease their proteinuria
used in dogs with severe hypertension alongside ace inhibitors
what side effects are associated with amlodipine?
generally well tolerated medication but:
hypotension, gingival hyperplasia, & peripheral edema
what are your ace inhibitor drug options?
enalapril or benazepril
what is the mechanism of action of ace inhibitors?
reduce angiotensin concentration thereby reducing vascular resistance & volume retention - also selectively dilates glomerular efferent arteriole thus decreasing glomerular pressure & proteinuria
what is the effect that ace inhibitors have on blood pressure?
mild reduction - only 10-20%
why are ace inhibitors listed as first line therapy for hypertensive dogs?
high prevalence of ckd & the antiproteinuric effect!
why are ace inhibitors not recommended as first line therapy for hypertensive cats?
they have a small effect on systolic blood pressure
T/F: you can continue using ace inhibitors in dehydrated patients
false
what drugs can be used alongside ace inhibitors?
amlodipine & telmisartan (with caution)
what side effects are associated with ace inhibitors?
generally well tolerated, but:
may worsen azotemia, cause hyperkalemia, hypotension, or gi upset
what is the starting dose used for ace inhibitors for hypertensive animals?
0.5 mg/kg po every 12-24 hours
what is the mechanism of action of telmisartan?
angiotensin receptor blocker - inhibits effect of angiotensin II at AT type 1 receptors thereby reducing vascular resistance & volume retention
can also decrease proteinuria
labeled for treatment of hypertension in cats in the USA
what is the dosing used for telmisartan for hypertensive patients?
cats 1-3 mg/kg po every 24 hours
dogs 1 mg/kg po every 24 hours
what is the mechanism of phenoxybenzamine? when may you use it? what are some other examples of drugs that have this same action?
alpha-blocker - opposes the vasoconstrictive effects of alpha receptors
mainly used in patients with pheochromocytomas
acepromazine, prazosin, etc
how is diet used as a part of therapy for a hypertensive patient?
low salt diet, but salt restriction alone will not decrease blood pressure
so select a diet based on all other medical conditions & avoid a high salt diet
can use diet to promote weight loss in obese patients
why are beta-blockers not used for treating hypertensive animals?
they have negligible anti-hypertensive effects
what are some direct vasodilator drugs that may be used for emergency management of hypertension?
hydralazine & nitroprusside
when may you use spironolactone for a hypertensive patient?
used to manage hypertension secondary to hyperaldosteronism along with potassium supplementation & adrenalectomy often with amlodipine
what kind of blood pressure measurement is shown in this photo?
doppler
what kind of blood pressure measurement is shown in this photo?
oscillometry
what kind of blood pressure measurement is shown in this photo? what is the only reliable measurement taken from this method? what may cause false readings?
high definition oscillometry
provides systolic, diastolic, & mean, but only systolic is reliable!!!
movement may cause false readings
what dosing of amlodipine is used in cats for treating hypertension? what about dogs?
cat with BP < 200 mmHg, 0.625 mg/cat po every 24 hours
cat with BP > 200 mmHg, 1.25 mg/cat po every 24 hours
titrate up to maximum dose of 2.5 mg/cat or 0.5 mg/kg po every 24 hours
dogs - 0.1-0.25 mg/kg po every 24 hours - dose may be increased as needed
T/F: telmisartan has not been evaluated for cats with blood pressures > 200 mmHg
true
if you start anti-hypertensive therapy on an animal with hypertension & a moderate risk of target organ damage, when do you schedule a recheck for monitoring?
recheck in 1 week
if you start anti-hypertensive therapy on an animal with severe hypertension & a high risk of target organ damage, when do you schedule a recheck for monitoring?
recheck in 2-3 days
if you start anti-hypertensive therapy on an animal with blood pressure > 200 mmHg and/or target organ damage, when do you schedule a recheck for monitoring?
recheck them in 24-48 hours!
