11.4: Htn Flashcards
What is blood pressure a product of?
- Cardiac output
2. Systemic vascular resistance
MAP equation
MAP = DBP + (SBP - DBP) / 3
What impacts stroke volume related to kidney?
Na balance
How does kidney in pact peripheral resistance?
RAS leads to vasoconstriction
Is hypertension usually result of increase CO or PVR?
Usually increased PVR
What are EDRF and endothelin?
Endothelium: causes constriction
EDRF: Causes dilation
What does increased adrenergic tone lead to?
Hypertension
- Increases vasc tone
- Increases NA Retention
- Increases inotropy
- Blockade of sympathetics reduces BP
Effects of angiotensin II?
- Vasoconstriction
- Na resorption in prox tubule
- Increases aldosterone: increases Na reabsorption in ducts
Effect of salt on Htn.?
- Increases BP
- There is a subset of hypertensives who show exaggerated increase
- It is recommended everyone should restrain Na although it does not impact everyone
What is the guyton hypothesis?
“Pressure natriuresis”
- Kidneys regulate arterial pressure by altering renal Na and water excretion
- Pressure goes up, excretion goes up
- In Htn., pressure natriuresis is maintained at higher BPs
What is monogenic Htn. usually result of?
- Na retention
- Most hypertension is polygenic
Role of kidneys in development of Htn.?
- Pressure natriuresis is abnormal in all types of Htn.
- No particular renal defect has been determined however
Main causes for secondary Htn.?
- Kidney disease
- Renal artery stenosis
- Hyperaldosteronism
- Pheochromocytoma
Volume mediated causes of secondary hypertension?
Non renal: 1. Hyperaldosteronism 2. Cushings 3. Mineralocorticoid tumors Renal: 1. Renal failure 2. Acute glomerulonephritis
Vasoconstrictor mediated causes of secondary Htn.?
- Pheochromocytoma
- Unilateral renal artery stenosis
- Hypercalcemia
What is pheochromocytoma?
- Tumor of Adrenal medulla
- Enormous Ne productions
- Leads to massive vasconstriction
How is pheochromocytoma treated?
- Surgery is standard of care
- Phenoxybenzamine or Phentolamine used before surgery
- These are Adrenergic blockers
What does hypercalcemia cause?
- Enters smooth muscle cells and causes vasoconstriction
Clinical presentation of renal artery stenosis?
- Severe and Difficult to control Htn.
- Kidney failure
- Flash pulmonary edema
Disease processes of renal stenosis?
- Atherosclerotic 95%
2. Fibromuscular dysplasia
Physiology when one kidney is stenosed?
- Ischemic kidney releases renin
- Healthy kidney has suppressed renin but demonstrates pressure natriuresis
- Htn develops because ischemic kidney cant turn off RAS
- **Treat by blocking RAS system of fix kidney
How is treatment of stenosis different if ptn. only has solitary kidney?
- RAS inhibitors can be used
- However, must also couple with diuretic as don’t have healthy kidney to decrease volume
Problem in bilateral renal stenosis?
- Both kidneys have increased RAS
- Neither can diurese so volume is problem
Effect of excess aldosterone?
- Increased Na and H2O retention leading to Htn.
What is hyperaldosteronism usually a result of?
- Adrenal hyperplasia
- Tumor is rare
- Diagnosed by high ADH w/ low Angiotensin
- Ratio > 35% means primary aldosteronism
How does kidney disease lead to Htn?
- Decrease GFR leads to decrease Na/H20 excretion
- Leads to excess volume worsening Htn.
- In advanced kidney disease, Htn is volume related
What leads to fibrinoid necrosis?
Malignant Htn.
Kidney size change in essential and malignant Htn.?
Essential: Kidney size shrinks, hyaline arteriosclerosis
Malignant: Fibrinoid necrosis seen, normal kidney size
What are the characteristics malignant retinopathy?
- Flame shaped hemorrhages
- Cotton wool exudates
- Papilledema
How do kidneys protect self in systemic htn.?
- Vasoconstriction of afferent arteriole
What is autoregulatory range of kidney?
- 60 -160 mmHg
- Beyond this GFR increase dramatically
2 Mechanisms of autoregulation of GFR?
- Myogenic response
2. Tubuloglomerular feedback
What is the myogenic response?
- Reflex vasoconstriction of afferent in response to increase pressure by smooth muscle contraction
- Can also be dilation
- **Main mechanism of autoregulation
What impairs autoregulation of kidneys?
- Dihydropyridine Ca antagonists
- Prevent normalization of glomerular pressure
- Prevent Ca from entering which normally would allow for constriction
Impact of dihydropyridine Ca antagonists?
Disables ability of kidneys to autoregulate
Contraindications of dihydropyridine Ca antagonists?
- Renal disease
2. Proteinuria
Impact of diabetes on autoregulation?
Impairs it
In which form of renal stenosis is htn volume related? RAS?
RAS: unilateral, treat with blockers
Volume: Bilateral, one kidney,
