Lecture 16: systemic and pulmonary hypertension

- vasoconstriction: sympathetic

- vasodilation: parasympathetic

What are the neural mechanisms of BP regulation?

- vasoconstriction: catecholamines, endothelin, ADH/vasopressin, RAAS

- vasodilation: NO, histamine, prostacyclin

What are the humoral mechanisms of BP regulation?

- arteriole size

What is the main factor in controlling SVR, which impacts BP (BP = CO x SVR)?

- kidneys

- pressure natriuresis and RAAS

What organ regulates blood volume? With what?

- an increase in systolic blood pressure in the systemic arteries

What is systemic hypertension?

- 133/75

What is the average normal blood pressure in dogs?

- 128/84

What is the average normal blood pressure in cats?

-

Fill in the following.

- idiopathic (primary, essential)

- secondary (underlying disease or medications) >80% of cases

- white coat hypertension

How can you classify hypertension?

- situational, stress-induced elevation of blood pressure = false elevation

- common during veterinary visits

What is white coat hypertension?

- primary or essential

- not a lot of dog or cat cases

- underlying etiologies: environmental factors, genetic predispositions, occult non-azotemic CKD?

What is idiopathic hypertension?

- secondary (80% of cases)

What is the most common type of hypertension?

- CKD

- pheochromocytoma

- primary hyperaldosteronism (PHA)

- hyperadrenocorticism

- hyperthyroidism

- diabetes mellitus

- obesity

secondary hypertension is the most common type of hypertension (80%)? What are examples of causes?

- chronic kidney disease

What is the most common condition associated with systemic hypertension in dogs and cats?

- RAAS activation

- effects on vascular tone and remodeling

- direct aldosterone effects

What are some reasons why chronic kidney disease leads to secondary systemic hypertension?

- rare

- 43-70% of dogs have systemic hypertension

What is the relationship between pheochromocytoma (adrenal medullary tumors) and hypertension?

- excessive circulating catecholamines

- sustained or paroxysmal episodes of hypertension

What is the pathophysiology of pheochromocytoma causing secondary systemic hypertension?

- sodium retention and volume expansion

- effects on vascular tone and remodeling

- direct sympathetic effect

40-60% of cats with primary hyperaldosteronism have secondary systemic hypertension. What is the pathophysiology?

- less common in the cat than the dog

- mild to moderate hypertension in dogs

- severe hypertension in a cats

How is hyperadrenocorticism (Cushing's disease) linked to hypertension?

- can cause mild secondary hypertension in dogs and cats

- BP is higher than healthy animals

How is diabetes mellitus and hypertension related?

- 15 year old cat

- BUN:CREAT is 38:2.2

- II/VI cardiac murmur at the sternal border

- small irregular contoured kidneys on palpation

What is the classic clinical picture of a hypertensive cat?

- eyes

- brain

- heart and vasculature

- kidneys

What are the target organs of systemic hypertension?

- retinal edema and hemorrhage

- retinal detachment

- optic neuropathy

- hyphema

- vitreal hemorrhage

- blindness = end result

What are the consequences of systemic hypertension on the eyes, that can occur at a SBP of 160 mmHg or above?

- hypertensive encephalopathy

- disorientation, seizures, ataxia, depression, vestibular signs

- acute onset and focal signs

What are the consequences of systemic hypertension on the brain?

- elevated systemic vascular resistance --> concentric left ventricular hypertrophy

- cause gallop +/- murmur, and/or arrhythmia

- MMVD, other systemic disease

- contribute to development of CHF

What are the consequences of systemic hypertension on the heart and vasculature?

- exacerbate kidney dysfunction

- glomerulosclerosis

- arteriosclerosis

- proteinuria

What are the consequences of systemic hypertension on the kidneys?

- multiple measurements should be obtained to confirm

- if mild hypertension or moderate risk for target organ damage, can obtain over the course of 1-2 months

- if high concern for TOD, obtain values in 1-2 weeks

How do you diagnose hypertension?

1. consider every 12 months

2. at least every 12 months

3. at least every 6-12 months

4. immediately and every 3-6 months

What monitoring BP recommendations for the following:

1. healthy adults:

2. healthy seniors:

3. healthy geriatrics:

4. CKD, hyperthyroidism, pheochromocytoma, PHA, HAC, TOD:

- equipment and cost

- inconsistency of measurement makes it unreliable as a parameter, technician skill variance

- non-compliant patients

- time constraints

- lack of training

- FRUSTRATION

Why is BP not measured as often as it should be?

- invasive technique that requires an arterial catheters (not always feasible)

What is the gold standard method of maintaining BP?

- doppler or oscillometric

- no standards for validation, interpret results cautiously

What are noninvasive blood pressure monitoring techniques?

- calm quiet room

- no other animals

- in cage, on own bedding, on owners lap = anywhere they are comfortable

- feliway could be used

What is the best environment for taking BP?

- give P at least 5-10 min in room to acclimatize

- allow exploration and interaction

- consider removing top of carrier if possible

How do acclimatization a patient before taking BP?

- minimize number of people involved

- have owner present if this reassures the P

- use trained and experienced person to measure SBP

How do you pick personnel for taking a BP?

- minimal and gentle restraint

- relaxed and comfortable position

- give breaks if needed to take readings when they are not moving

How do you restraint/position the animal for a BP?

- tail or forelimb

Where do take a BP in a cat?

- forelimb

Where do you take a BP in a dog?

- cuff width = 30-40% of circumference of limb/tail

How should the cuff fit a patient?

- need good contact so use alcohol or gel

- position inflatable portion of cuff over the artery to be occluded

- position doppler probe with gentle pressure until pulsatile blood flow is heard

- slowly inflate cuff to 20-40 mmHg above the point where blood flow is no longer heard

- slowly release air from cuff -> SBP is point at which pulsatile blood flow is first detected

How do you a using doppler?

- use it on the tail and make sure the patient is still

- place area where inflation tube enters the cuff closest to the artery

- cuff automatically inflates and deflates

- only record SBP

- device should be linked to a computer or tablet to confirm deflation of cuff is steady and pulse waves are smooth

How do you use a high definition oscillometry?

- do not use the first measurement

- obtain 5-7 consecutive and consistent measurements (no matter the value)

- SBP is calculated as the mean of these

How do you take BP measurements?

- if there is consistent downward or upward trend in readings or >20% variation, further measurements should be made until consistent readings are achieved

- if there is any doubt over SBP validity, repeat the procedure immediately, after further acclimatization or later

How do you interpret BP measurements?

- eval for TOD and underlying disease

- complete PE

- complete clinical history

- lab evaluation

- +/- diagnostic imaging

- +/- serum aldosterone

- +/- additional endocrine testing PRN

How do investigate hypertension?

- anti-hypertensive therapy not always necessary

- recommended frequent monitoring of underlying disease and BP

- consider recheck every 6 months

How do you treat prehypertension, SBP 140-159 mmHg?

- Amlodipine (Ca channel blocker)

- Telmisartan (angiotensin 2 blocker)

- enalapril or benazepril (ACEi; decrease RAAS and BP)

What are 3 medication options for treatment of systemic hypertension?

- Amlodipine frequent PO dosing

- Sodium nitroprusside IV

- Hydralazine IV

What are options of emergency management of systemic hypertension (hypertensive crisis)?

- angiotensin II receptor blocker (ARB) like losartan and telmisartan

Which medications can be given to decrease the effects of angiotensin II in the animal?

- ACE inhibitors like enalapril and benaziprol

Which medications can be given to decrease the amount of angiotensin II in the animal to decrease BP?

- altered renal sodium excretion

- reduced arterial blood pressure

What are the actions of angiotensin II receptor blocker (ARB)?

- blocks calcium influx into vascular smooth muscle leading to arterial vasodilation

Why is amlodipine used to treat hypertension or a hypertensive crisis?

- Alpha antagonism causes vasodilation

- beta antagonism = decreased CO and contractility, blockage of renin release, and decreased vascular resistance

How do adrenergic receptor antagonists like propranolol, atenolol, and prazosin work to decrease BP?

- Hydrazine

Which medications has an not completely understood MOA and is a used in a hypertensive crisis due to its arterial vasodilation effects?

- blocks aldosterone at renal distal tubule and collecting ducts to decrease sodium reabsorption and potassium excretion

How does spironolactone used for hypertension?

- a new peripheral dopamine 1 agonist

- renal arterial vasodilation, natriuresis, increased GFR

What is fenoldopam?

- to drop BP enough that it is in the zone with TOD

- SBP less than or equal to 160 mmHg

What is the goal of hypertensive treatment?

- some eye changes can be partially reversible

- CHS usually requires long-term management

- responsiveness depends on what type of issues

- median survival 7 to 18 months

What is prognosis for systemic hypertension like?

- recheck in one week after starting anti-hypertensive medication

- If patient has evidence of TOD blood pressure should be recheck the following day

- continue rechecking to see if meds need to be adjusted

How do you manage a hypertensive patient?

- ACE-inhibitor = first line

- caution when using Ca channel blocker as sole agent potential for glomerular injury

- make sure P is hydrated first

What is treating hypertension like in dogs?

- Ca channel blocker often first line --> Amlodipine

-ACE-I can be added as a second agent (hydrate first) --> enalapril or benazepril

What medications do you want to use to treat hypertension in cats?

- CKD with mild to moderate hypertension and proteinuria

Telmisartan can be used has been shown to reduce hypertension in cats. what is it used best for?

- significant hypertension (>180) without TOD

- reduce pressure over hours to days

what is a hypertensive crisis urgency?

- marked hypertension (> 180)with TOD requires

- immediate reduction in blood pressure

What is a hypertensive crisis emergency?

- acute blindness or visual disturbance (detachment or hemorrhage)

- acute neurologic abnormalities

- congestive heart failure

- progressive renal insufficiency

- epistaxis

What is seen with hypertensive emergencies?

- reduce BP ASAP, but avoid excessive drops

- hospitalize and monitor

How should you treat a hypertensive emergency?

- an increase in pulmonary arterial pressure leads to right sided heart strain

- classified with echo measurements

- normal systolic pulmonary artery pressure and dog and cat is less than 30 mmHg

- usually secondary to a primary disease process so look for a cause

- pre-capillary versus post capillary causes

What is pulmonary hypertension?

- before lungs; pulmonary artery

What does pre-capillary mean?

- after lungs; left heart

What does post capillary mean?

- pre-capillary

- idiopathic, left to right shunts (congenital heart disease, PDA/VSD)

- drugs, toxins (smoke, CO, chronic steroids, vasopressors, and some chemo)

What is pulmonary hypertension group 1: pulmonary arterial, hypertension caused by?

- post capillary

- Chronic left sided congestive heart failure - mitral regurgitation or cardiomyopathy

What is pulmonary hypertension group 2: pulmonary venous hypertension caused by?

-COPD, chronic bronchitis, interstitial, lung disease, high altitude exposure, and chronic airway obstruction

What is pulmonary hypertension group 3: respiratory disease or hypoxia caused by?

- Pulmonary thromboembolism

Pulmonary hypertension group 4>

- Heartworms

- angiostrongylus

What is pulmonary hypertension group 5: parasitic diseases cause by?

- Multifactorial, systemic or unclear mechanism

What is pulmonary hypertension, group 6?

- CS: respiratory distress, syncope, exercise, intolerance, tachycardia, signs of right sided heart failure

- PE: right sided systolic murmur tricuspid regurgitation

- Lab testing

- ECG

- ECHO = GOLD STANDARD

- BP: exclude systemic hypertension

- thoracic rads: right ventricular, enlargement and main pulmonary artery dilation

How do you diagnose of pulmonary hypertension?

- increased tricuspid regurgitation velocity (estimate systolic pulmonary arterial pressure)

-right heart enlargement develops overtime and with severity

How do you diagnose pulmonary hypertension with echo?

- thrombus occludes flow through the pulmonary vessels

- can be minor/clinically unimportant, moderate, or massive

- Associated with high risk of death if untreated

What is a pulmonary thromboembolism?

- Hypercoagulability

- altered blood flow

- endothelial damage

- the drives of clot formation

What is the Virchow's triad?

- increased platelet activation

- increased activation of coagulation factors

- reduced endogenous anticoagulant

- reduced fibrinolysis

What are causes of hypercoagulability?

- thrombocytopenia or thrombocytosis

- PT and PTT: prolong clotting times

- D-dimers: a fibrin degradation product seen with thrombolysis

- TEG: positive + many animals with severe systemic illness

- Antithrombin levels: low levels may increase risk for thrombosis

What tests might increase your suspicion or concern about thrombotic disease?

- treat underlying cause

- prevent thrombotic disease of indicated

- pulmonary arterial vasodilation with sildenafil (PDE5 inhibitor)

- supplemental oxygen

How do you treat pulmonary hypertension?

- identify patient at risk

- Nonpharmaceutical: limit IV catheters, encourage activity, and treat underlying disease

- Pharmaceutical: aspirin, cloistered, heparin, low molecular weight heparin, Coumadin, rivaroxaban

How do you prevention of pulmonary thromboembolism?

- low shear stress, fibrin and RBC, due to activation of coagulation

- treat with: unfractionated heparin,

LMW heparin, warfarin, or other factor Xa inhibitors

What is venus thrombi? How do you treat?

- high shear stress

- platelet activation (platelet rich)

- treat with: direct platelet agonist receptor inhibitors (Plavix), indirect intracellular platelet inhibitors (Aspirin), Integrin alpha2b beta3 inhibitors

What is arterial thrombi? How do you treat?

- thrombolytics breakdown thrombus formed by the body

How do thrombolytic drugs work like tissue plasminogen activator?

- binds to plasminogen on fibrin surface of thrombus to convert plasminogen to plasma and then break down thrombus

What is the thrombolytic drugs MOA like tissue plasminogen activator?

- unfractionated heparin or low molecular weight heparin

- thrombolytics = tissue plasminogen activator

- surgical hemodynamically unstable cases

What is the confirmed pulmonary thromboembolism therapy?