Hypertension and RAAS Flashcards

1
Q

How and when should BP be measured in a dog/cat during a visit?

A

In a quiet area, away from other animals, before other procedures, and after the patient has acclimated for 5-10 minutes. Owner should be present and restraint should be minimal, but the patient should be in ventral or lateral recumbency

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2
Q

What should the width of the BP cuff be?

A

30-40% of the circumference of the extremity at the site of cuff placement

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3
Q

How many BP measurements should be obtained?

A

Discard the first measurement. Then 5-7 consecutive, consistent readings

If BP is trending downward as the animal adjusts, continue until a plateau is reached, then take 5-7 readings

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4
Q

If the vertical distance from the heart to the base of the cuff is more than 10cm, what correction can be applied?

A

Add 0.8 mmHg/cm below or above the heart base

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5
Q

Blood pressure in hounds (Greyhounds, Deerhounds) is how much higher than other dogs?

A

10-20mmHg higher

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6
Q

What is situational hypertension?

A

Increases in BP that occur as a consequence of the in clinic measurement process in an otherwise normotensive animal

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7
Q

What causes situation hypertension?

A

Autonomic nervous system alterations

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8
Q

What is secondary hypertension?

A

Persistent, pathologically increased BP concurrent with a disease or condition known to cause hypertension or administration of a drug or toxin known to cause hypertension

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9
Q

Name 6 disease conditions associated with secondary hypertension

A

CKD, AKI, hyperadrenocorticism, DM, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism

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10
Q

Name 5 drugs associated with secondary hypertension

A

Glucocorticoids, mineralocorticoids, EPO, PPA, Ephedrine/pseudoephedrine, Palladia

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11
Q

What is primary/essential/idiopathic hypertension?

A

Persistent, pathological hypertension in the absence of any identifiable underlying cause

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12
Q

How can BP affect USG?

A

Hypertension can cause polyuria from pressure diuresis, so a USG <1.030 in a patient with hypertension does not necessarily mean that CKD is present

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13
Q

What percent of cats have idiopathic hypertension?

A

13-20%

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14
Q

How can hypertension affect the kidneys?

A

Causes proteinuria and histological renal injury. Proteinuria, in turn, leads to more rapid progression of renal disease

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15
Q

What are the findings with hypertensive retinopathy and choroidopathy?

A

Exudative retinal detachment - most common
Retinal hemorrhage or edema, retinal vessel tortuosity, vitreal hemorrhage, hyphema, secondary glaucoma, and retinal degeneration

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16
Q

What is hypertensive encephalopathy?

A

White matter edema and vascular lesions from hypertension

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17
Q

When is hypertensive encephalopathy more likely to occur?

A

Cats with a sudden increase in BP, systolic BP >180 mmHg, or both

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18
Q

What are the clinical signs of hypertensive encephalopathy?

A

Lethargy, seizures, acute onset of altered mentation, altered behavior, disorientation, vestibular signs

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19
Q

Hypertension is also a risk factor for ischemic myelopathy of the cranial cervial spinal cord. How does this present?

A

Cats with ambulatory tetraparesis or tetraplegia with intact nociception

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20
Q

What is the most common cardiac change associated with hypertensive cardiomyopathy?

A

Left ventricular concentric hypertrophy

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21
Q

What are the indications for measuring BP in a dog or cat?

A
  • Patients with clinical abnormalities consistent with hypertensive target organ damage
  • The presence of diseases or conditions or the treatment with drugs associated with secondary hypertension
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22
Q

In the majority of cases, BP results should be repeated on >2 occasions before starting treatment. What is the exception?

A

When there is evidence of target organ damage along with an elevated BP - start treatment now

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23
Q

What are the classifications of hypertension in dogs/cats?

A

Normotensive: SBP < 140
Prehypertensive: SBP 140-159
Hypertensive: SBP 160-179
Severely hypertensive: SBP >180

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24
Q

If a patient’s BP is <160 mmHg, when should they be rechecked?

A

3-6 months

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25
Q

If a patient’s BP is 160-179 mmHg with no evidence of target organ damage, when should they be rechecked?

A

Repeat BP twice within 4-8 weeks
- If repeatedly above 160, look for underlying causes and start antihypertensives

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26
Q

If a patient’s BP is >180 mmHg with no evidence of target organ damage, when should they be rechecked?

A

Repeat BP twice within 2 weeks
- If repeatedly above 160, look for underlying causes and start antihypertensives

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27
Q

After starting antihypertensive medication, when should the BP be rechecked?

A

7-10 days if no TOD
1-3 days if TOD is present

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28
Q

What is the goal of antihypertensive therapy?

A

Optimal goal: BP <140 mmHg
Minimal goal: BP <160 mmHg

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29
Q

If you achieve the goals of antihypertensive therapy, when should you recheck the patient?

A

Every 4-6 months

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30
Q

A RAAS inhibitor can be used as the first line anti-hypertensive treatment in dogs, except in what situation?

A

Severe hypertension (BP >200) - start BOTH a RAAS inhibitor and CCB

31
Q

Why should a CCB not be used as monotherapy in hypertensive dogs?

A

CCB preferentially dilate the renal afferent arteriole, increasing glomerular capillary hydrostatic pressure and worsening proteinuria

32
Q

Amlodipine is the first line therapy for hypertensive cats. What decrease in BP does it typically cause?

A

28-55 mmHg

33
Q

What is the starting dose of amlodipine in cats?

A

If SBP <200mmHg, 0.625 mg/cat
If SBP >200mmHg, 1.25mg/cat

34
Q

What decrease in BP is seen in cats on ACEi?

A

Small - <10mmHg
Not useful as a single agent, but can be used with amlodipine

35
Q

What adverse effects have been noted with spironolactone in cats?

A

Facial dermatitis and excoriation (rare)

36
Q

In patients with acute hypertensive emergencies (TOD), what is the therapeutic target? Why?

A

Small, incremental decrease in SBP rather than normalization - decrease by 10% over the first hour and 15% over the next few hours

In chronic hypertension, the autoregulatory vascular beds in the brain and kidneys have adapted to higher perfusion pressure; acute marked BP reductions may result in hypoperfusion

37
Q

Due to the requirement for incremental SBP decreases in a hypertensive crisis, what types of agents should be used?

A

Parenteral drugs that can be titrated to effect with rapid onset and rapid conclusion of action

38
Q

What is fenoldopam?

A

Dopamine-1 receptor agonist approved for human hypertensive emergencies - causes renal arterial vasodilation, natriuresis, and increased GFR

39
Q

Apart from fenoldopam, what other drugs can be used in a hypertensive crisis?

A

Hydralazine, nitroprusside, labetolol

40
Q

What percent of cats with AKI were hypertensive?

A

59%, severe (>180) in 28% - was not correlated with grade of AKI, creatinine, oliguria or anuria

41
Q

What is angiotensin converting enzyme 2?

A

Homologue of ACE but produces angiotensin peptides (angiotensin 1-9 and 1-7) that are vasodilatory and natriuretic - counterbalance angiotensin II

42
Q

In a study of 780 healthy cats, what factors were associated with higher systolic BP?

A

Increased age, male sex, increased nervousness, history of being a stray, neutering

43
Q

How does the BP of Birman’s differ from other cat breeds?

A

Lower (125 vs 140)

44
Q

Absent metatarsal pulses correctly identify cats with a SBP of 75mmHg or less what percent of the time?

A

84%

45
Q

Absent metatarsal and femoral pulses correlated with a SBP of what?

A

30mmHg on average

46
Q

Did treatment of CKD in dogs with benazepril improve survival time in a randomized clinical trial?

A

No - MST 305 for benazepril and 287 for placebo

47
Q

Did proteinuria improve with treatment of CKD dogs with benazepril in a randomized clinical trial?

A

Yes - but not that much
All dogs: UPC 1.51 benazepril vs 1.94
Dogs with UPC >0.5: UPC 1.76 benazepril vs 2.98

48
Q

Compared to placebo, telmisartan (1-3mg/kg/day) had what affect on SBP in cats?

A
  • Decreased SBP at all dosages by two weeks after initiation of treatment
  • SBP remained decreased for 2 days after stopping telmisartan
  • No hypotensive events
49
Q

In a prospective, randomized, blinded European trial, what effect did telmisartan have on the BP of 252 cats

A

By day 14, telmisartan decreased SBP from 180 mmHg by 19 mmHg

By day 28, decreased SBP by 25 mmHg

Placebo group decreased by 9 and 11

50
Q

In a prospective, randomized, blinded European trial, what percent of telmisartan cats had achieved an SBP <150mmHg by day 28?

A

52%

51
Q

In a prospective, randomized, blinded European trial, how long did the effects of telmisartan on BP last?

A

For the entire study period - up to 120 days after initiation of treatment

52
Q

In a prospective, randomized, blinded European trial, how many cats on telmisartan experienced hypotension?

A

2 out of 252

53
Q

What factor influenced the dose of amlodipine needed to control BP in cats?

A

The initial SBP - cats that needed 0.625mg had a median SBP 182 vs 207 in cats that needed 1.25mg

54
Q

In a prospective, randomized, blinded American trial, what was the SBP decrease in cats on telmisartan by day 14?

A

Telmisartan decreased BP by 23mmHg compared to 7.5 in the placebo group

Similar results at day 28

55
Q

In a prospective, randomized, blinded American trial, how long did the decrease in SBP persist while on telmisartan?

A

The entire study period - 6 months of follow up

56
Q

Where is renin synthesized? What form is it synthesized in?

A
  • In the juxtaglomerular epithelioid cells
  • Synthesized as preprorenin, which is cleaved to prorenin, then renin
57
Q

What is the rate limiting step in the RAAS cascade?

A

Release of renin granules - released in a controlled manner, unlike angiotensinogen, which is constitutively released from the liver

58
Q

What factors trigger renin release?

A
  • Low systemic BP
  • Hypovolemia
  • Sodium deprivation
  • Sympathetic stimulation
59
Q

What is the function of renin in circulation?

A

Metabolizes angiotensinogen to angiotensin I

60
Q

Where is angiotensin converting enzyme released and what is it’s function?

A
  • Released from endothelial cells
  • Convers angiotensin I to angiotensin II
61
Q

When angiotensin II binds to angiotensin type 1 receptors, what effects occur?

A
  • Sodium retention
  • Vasoconstriction (including preferential constriction of the efferent arteriole)
  • Stimulation of thirst
  • Enhanced sympathetic nervous system activity
  • Aldosterone release
62
Q

Where is aldosterone released from?

A

The zona glomerulosa of the adrenal glands

63
Q

When angiotensin II binds to angiotensin type 2 receptors, what effects occur?

A

Counter regulatory to the actions of the type 1 receptor - anti-inflammatory, anti-fibrotic, vasodilatory

64
Q

What two things stimulate aldosterone release?

A

Angiotensin II
Increased extracellular K+ concentrations

65
Q

Aldosterone acts on mineralocorticoid receptors. Where are these located?

A

Kidney, colon, salivary and sweat glands

66
Q

What is the ultimate function of aldosterone?

A

Increase in transepithelial Na+ and water reabsorption, K+ excretion

67
Q

Aldosterone and angiotensin peptides are also produced locally in tissues. What roles do locally produced RAAS hormone have?

A
  • Play important roles in normal cardiovascular function and electrolyte-fluid balance
  • Mediate abnormal remodeling (hypertrophy and fibrosis) of tissues
68
Q

Local (tissue) activity of aldosterone can be stimulated by what factors?

A
  • Mechanical stretch of the myocardium and vessels
  • Adipocyte secretions
  • ROS and inflammation
69
Q

Angiotensin II increases sodium reabsorption in what renal tubules?

A

Proximal tubule and loop of Henle

70
Q

ACEi not only decrease formation of angiotensin II, but they decrease the degradation of what vasodilatory compound?

A

Bradykinin

71
Q

In local tissues, what enzyme is more important than ACE for conversion of angiotensin?

A

Chymase

72
Q

Clinical trials evaluating the use of ACEi in dogs with CHF showed that ACEi improved what factors?

A
  • Improvement in pulmonary edema score
  • Improvement in pulmonary capillary wedge pressure
  • Improvement in cough
  • Improvement in survival time and delay to worsening of CHF
73
Q

In a double blinded study of dogs with MMVD Stage B2, treatment with enalapril improved what?

A

All cause mortality

74
Q

Another study evaluating Cavaliers with B1 or B2 MMVD showed what difference between enalpril and placebo?

A

No difference in the onset of CHF