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Small Animal Medicine > Systemic Hypertension > Flashcards

Systemic Hypertension Flashcards

1
Q

What 2 things determine systemic blood pressure?

A

Cardiac output & systemic vascular resistance

*Remember BP = CO x SVR

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2
Q

Describe how the SNS regulates systemic blood pressure.

A

The SNS is activated when baroreceptors in blood vessels & the heart sense a decrease in blood pressure
-> Catecholamines (norepinephrine & epinephrine) are released
-> CO & SVR are increased

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3
Q

Systemic blood pressure is regulated by what 2 things?

A
  1. Sympathetic nervous system
  2. RAAS
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4
Q

Describe how RAAS regulates blood pressure

A

Decreased renal perfusion causes release of renin from kidneys -> converts angiotensinogen (produced by liver) to angiotensin I
-> ACE converts angiotensin I to angiotensin II
-> Angiotensin II causes contraction of smooth m. in vasculature -> inc. SVR
-> Angiotensin II also causes release of aldosterone from adrenals -> stimulates reabsorption of Na & H2O to inc. blood volume -> inc. CO

Angiotensin II also causes excretion of K+

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5
Q

Define systemic hypertension

A

Persistent elevation of systemic blood pressure (systolic > 160mmHg)

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6
Q

What 2 things determine cardiac ouput?

A

Heart rate & stroke volume

*Remember CO = HR x SV

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7
Q

What are the 2 general causes of systemic hypertension in dogs & cats?

A
  1. Primary idiopathic
  2. Secondary to other conditions that increase CO +/- SVR
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8
Q

Of direct and indirect methods to measure blood pressure, which is the gold standard & which is most practical?

A

Indirect = most practical
Direct = gold standard

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9
Q

Which method of measuring blood pressure is preferred in cats and small dogs?

A

Doppler

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10
Q

What are the 2 indirect methods used to measure blood pressure in dogs & cats?

A

Doppler & Oscillometric

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11
Q

Describe how doppler method works to measure systemic blood pressure

A

Arterial blood flow is occluded by inflating a cuff & then deflating it until the flow goes back to normal.

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12
Q

How do you know what size cuff to use when measuring blood pressure in dogs and cats?

A

Cuff width should be 30-40% of the circumference of the chosen site (limb or tail)

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13
Q

If the cuff you have chosen is too big, it could falsely increase/decrease (choose one) blood pressure.

A

Decrease

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14
Q

If the cuff you have chosen is too small, it could falsely increase/decrease (choose one) blood pressure.

A

Increase

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15
Q

Why should you gently restrain the dog/cat in lateral or ventral recumbency when measuring blood pressure?

A

To limit vertical distance from the heart base to the cuff

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16
Q

What are the 4 potential locations you may use to obtain an indirect blood pressure in dogs & cats?

A
  1. Underside of carpus
  2. Underside of metatarsus
  3. On top of the medial aspect of the metatarsus between the long bones of digits 2 & 3 on top of the back of the foot
  4. Underside base of tail (cats)
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17
Q

What are 4 possible areas of target organ damage from systemic hypertension?

A
  1. Eyes (retinopathy, blindness)
  2. Kidneys (proteinuria, progression of CKD)
  3. Brain (encephalopathy, stroke)
  4. Heart/blood vessels (left ventricular hypertrophy, arrhythmias, CHF, etc.)
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18
Q

What systemic blood pressure range is considered to be normotensive & has minimal TOD risk?

A

< 140mmHg

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19
Q

What systemic blood pressure range is considered to be hypertensive & has moderate TOD risk?

A

160-170mmHg

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20
Q

What systemic blood pressure range is considered to be prehypertensive and has low TOD risk?

A

140-159mmHg

21
Q

What systemic blood pressure range is considered to be severely hypertensive and has a high TOD risk?

A

180mmHg or greater

22
Q

Is primary or secondary systemic hypertension more common in dogs & cats?

A

Secondary causes

23
Q

What are the 2 most common secondary causes of systemic hypertension in cats?

Only looking for most common, but feel free to list more for bonus points

A
  1. CKD
  2. Hyperthyroidism

Other (less common) causes include adrenal disorders (Hyperaldosteronism, Pheochromocytoma, Hyperadrenocorticism), and medications

24
Q

What are 4 examples of medications that are associated with causing hypertension?

A
  1. Glucocorticoids
  2. Mineralocorticoids
  3. Phenylpropanolamine (Proin)
  4. Erythropoietin
25
Q

How does renal disease lead to hyperthyroidism?

Looking for 5 things here

A
  1. Activation of RAAS & impaired Na+ excretion -> inc. intravascular volume
  2. Stimulation of SNS
  3. Endothelial dysfunction
  4. Decreased vasodilator production (Nitric oxide)
  5. Increased production of vasoconstrictors (endothelin)
26
Q

How does hyperthyroidism cause hypertension in cats?

A

Increased sympathetic activity -> increased SV & HR -> increased CO

27
Q

What are 5 secondary causes of hypertension in dogs?

A
  1. Kidney dz (acute or chronic)
  2. Cushing’s
  3. Diabetes
  4. Pheochromocytoma
  5. Hyperaldosteronism (uncommon)
28
Q

What are 3 cases in which you should definitely treat a patient for hypertension?

A
  1. Severe hypertension
  2. Evidence of TOD w/ moderate to severe hypertension
  3. Persistent BP > 160mmHg w/ dz associated w/ hypertension
29
Q

When is treatment for systemic hypertension not recommended? What should you do instead?

A
  • Tx not recommended w/ prehypertension w/ no clinical signs
  • Monitor BP during future visits
30
Q

Why is it controversial to recommend a sodium restricted diet in cats & dogs with hypertension?

A
  • Not as effective as in humans
  • Usually doesn’t substantially decrease BP (may actually increase BP by activating RAAS)
31
Q

What is the first line of treatment for systemic hypertension in cats?

A

Amlodipine (calcium channel blocker)

32
Q

Describe the mechanism of action of calcium channel blockers

A

Relax vascular smooth muscle -> vasodilation -> decrease SVR

33
Q

What is the first line of treatment of systemic hypertension in dogs?

A

ACE Inhibitor (Benazepril, Enalapril)

Bonus points if you said + Amlodipine in dogs w/ severe hypertension (180-200mmHg)

34
Q

Why can ACE inhibitors be used as a treatment for proteinuria?

A

They preferentially dilate the EFFERENT arteriole of the glomerulus

35
Q

How can ACE inhibitors cause azotemia?

A

They preferentially dilate the EFFERENT arteriole of the glomerulus (decreased pressure within the glomerulus), which can reduce GFR -> azotemia

36
Q

Amlodipine can decrease BP by how much in cats?

A

30-50mmHg

37
Q

Why is Amlodipine not used as a sole treatment for dogs with severe hypertension?

A

Amlodipine preferentially dilates renal AFFERENT arterioles, potentially exposing glomerulus to damaging increases in glomerular capillary hydrostatic pressure

aka can lead to increased proteinuria if BP not significantly decreased

38
Q

You have just started a dog on an ACE Inhibitor. When do you tell the client you would like to see the dog again, and what are you going to do at that visit?

A

Evaluate renal values & electrolytes 7-10 days after starting tx or increasing dose

*Ace inhibitors block the production of Aldosterone, so they can look like an Addisonian patient (hyperkalemia & hyponatremia)

39
Q

Why are ACE inhibitors not the first line of treatment for systemic hypertension in cats?

A

Only has a ~10mmHg reduction in BP in cats

40
Q

What drug class is Telmisartan, and when is it used?

A

Angiotensin II receptor blocker;

used for moderate hypertension & proteinuria in cats (& dogs as an alternative tx to ACE inhibitors)

41
Q

You have started a cat on Telmisartan. When do you tell the owner you would like to see the cat again, and what are you going to do at that visit?

A

Recheck renal values & electrolytes 7-10 days after starting or increasing dose

Can reduce GFR like ACE inhibitors, but has stronger effect on kidneys so use caution in cat that is already azotemic

42
Q

What emergency drugs are used to treat severe life-threatening hypertension?

A

Direct arterial vasodilators (Hydralazine, Sodium nitroprusside)

Have greater risk for hypotension, so rarely used unless absolute emergency

43
Q

When are alpha adrenergic antagonists used to treat systemic hypertension?
Give 2 examples of drugs in this class.

A
  1. Used for treating hypertension caused by pheochromocytomas (excess catecholamine production)
  2. Phenoxybenzamine & Prazosin
44
Q

What diuretic can be used in treatment of systemic hypertension, specifically in cases of hyperaldosteronism?

A

Spironolactone (act as an aldosterone antagonist -> reduces sodium & water reabsorption)

45
Q

A patient you started on Enalapril presents to you one month after starting tx for hypertension. The patient is QAR, tachycardic, and the owner reports the patient seems weak at home & described an episode of syncope. BP in hospital was 110mmHg. What do you do?

A

Concerned for hypotension -> decrease dose

Patients with a BP <120 & showing the clinical signs described in the case are consistent with hypotension

*Our goal is to keep systolic BP <140mmHg

46
Q

A patient has an elevated BP, and there are signs of TOD. When should you recheck BP?

A

3 days

47
Q

A patient has an elevated BP, but there are not signs of TOD. When should you recheck BP?

A

7-10 days

48
Q

Once a patient’s BP is stable with treatment, how often should you recheck BP?

A

Every 3 months

Small Animal Medicine (8 decks)

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