Diuretics HTN Flashcards
Arterial BP =
Cardiac output + peripheral vascular resistance
Cardiac output depends on?
Myocardial contractility
Ventricular filling pressure
Ventricular filling pressure is composed of?
Blood volume and venous tone
Vascular resistance depends on?
State of smooth muscle cells (contracted/relaxed)
Activity of the systems (controlling the diameter of resistance vessels)
Define Myocardial contractility
How the heart is contracting
Define ventricular filling pressure
How much blood if filling into the heart
What is the main function of the kidneys?
Maintain normal body fluid volume and electrolyte balance
- Filtration, reabsorption, secretion and excretion
Reabsorption of what?
Ions, amino acids, glucose, water,
Normal filtration rate?
120 mL/min
How much of fluid and electrolytes are reabsorbed?
99.9%
Rate if urine production?
1 mL/min
Nephron (urine forming unit) =
Glomerulus (filtration) + Tubule (reabsorption and conditioning)
What does the afferent arteriole do?
Brings the blood to the glomerulus
What does the efferent arteriole do?
Removes left over blood from the glomerulus
What is different about the glomerulus than other places in the body?
Endothelial cells are not tightly connected to each other leading to easier permeabilty
What holds filtered blood?
Bowman’s capsule
Where is reabsorption the greatest?
Proximal tubule and it declines distally towards the collecting ducts
Proximal tubules reabsorbs?
65% of sodium and highly permeable for water
Loop of Henle reabsorbs?
25% of sodium
Thin descending limb reabsorbs
Water but not sodium
Early distal tubule and distal convoluted tubules reabsorb?
5% of sodium
NO water or urea
Sodium reabsorption is controlled by?
Aldosterone
Water reabsorption is controlled by?
ADH
What is a major determinant of extracellular fluid volume?
NaCl
What do diuretics do?
Increase the rate of urine flow and sodium and chloride excretion
Diuretics –>
Increase Na and Cl excretion –> Decreased ECF volume –> decreased venous return –> Decreased cardiac output –> Decreased BP
Continued administration of diuretics cause?
Sustained net deficit of sodium & decreased ECF volume and BP
Compensatory mechanisms mean what?
Balance between sodium intake and excretion
Chronic effects of diuretics –>
Increased excretion and decreased fluid –> compensatory mechanisms –> decreased excretion & extracellular volume returns to normal –> decreased peripheral resistance –> BP remains low
Initial BP lower effects of diuretics is due to?
Sodium excretion and ECF volume decrease
Chronic BP lowering effect of diuretics is due to?
Reduction of peripheral resistance
Loop diuretics drugs?
Bumetanide (Bumex)
Furosemide (Lasix)
Torsemide (Demadex)
Loop diuretics site of action
Thick ascending limb of the Henle Loop where 25% of sodium reabsorption occurs
Loop diuretics MOA
Inhibition of Na/K/Cl symporters
Inhibit the reabsorption of Na, K, Cl and indirectly inhibits reabsorption of Ca and Mg
Loop diuretics urinary and hemodynamic effects?
Increased urine flow: excretion of Na, K, Cl, Ca, and Mg
Volume depletion and decrease of BP via renin release and SNS activity
With acute use of loop diuretics what can you see that is lost during chronic use?
Increased excretion of uric acid
What are Loop Diuretics main therapeutic uses?
Acute pulmonary edema HTN and HF Edema and scites Drug overdose Hypercalcemia
Define ascites
Accumulation of fluid in the peritoneal cavity
What are the main adverse effects of loop diuretics due to fluid changes?
HYPOnaemia, hypotonia, circulatory collapse, thromboembolic episodes
Hypochloremic
Hypokalemia
Hypomagnesemia and hypocalcemia
Hypokalmeia and hypomagnesmia are risk factors for?
Cardiac arrhythmias
What are other main adverse effects of loop diuretics NOT due to fluid changes?
Ototoxicity
Hyperuricemia
Increased LDL cholesterol and decreased HDL
What is the strongest diuretic?
Bumetanide
Thiazide Diuretics
Chlorthalidone (Hygroton)
Hydrochlorithiazide (Microzide)
Indapamide (Lozol)
Metolazone (Zaroxolyn)
Thiazide Diuretics Site of Action
Distal convoluted tubule
where 5% of Na reabsorption occurs
Thiazide Diuretics MOA
Inhibition of Na/Cl symporters
No reabsorptions of Na or Cl
What are the main effects of thiazide diuretics?
Increased excretion of Na, Cl, K (indirectly) and water
Lower BP bc of increased Na excretion
What are the main effects of chronic thiazide diuretics uses?
Decreased excretion of Calcium and uric acid
Main therapeutic uses of Thiazide diuretics?
HTN
Edema
Nephrogenic diabetes insipidus
Calcium nephrolithiasis & osteoporosis
Define Nephrogenic diabetes insipidus?
Kidney is unable to conserve water
What are other main adverse effects of thiazide diuretics due to fluid changes?
Extracellular volume depletion, HYPOtension HYPOnaemia, HYPOclemia HYPOkemia HYPERcaemia HYPERuricemia
Hyperuricemia leads to a risk of?
Gout
What are other main adverse effects of thiazide diuretics NOT due to fluid changes?
Reduction of glucose tolerance due to reduced insulin secretion or K depletion
Increased risk for sexual impotency
Increase levels of LDL, total cholesterol and TGs
Is chlorathalidone or hydrochlorthiazide more potent with a longer half life?
Chlorthalidone is 50% more potent and a MUCH longer halflife
What is THE most potent thiazide diuretic?
Indapamide
Inhibitors of renal epithelial Na Channels Potassium Sparing Diuretics
Amiloride (Midamor)
Triamterene (Dyrenium)
Potassium-Sparing Diuretics Site of Action
Late distal tubule and collecting duct where ~2% of Na reabsorption occurs
Inhibitors of renal epithelial Na Channels MOA
Inhibition of renal epithelial Na channels
Decreased reabsorption of Na and increased reabsorption of K
Involves principal cells collecting as much sodium as they can but not potassium
Inhibitors of renal epithelial Na Channels main adverse effects
HYPERkalemia
N/V/D
Headache
Triamterene can cause?
Glucose tolerance and photosensitization
Aldosterone Antagonists Potassium Sparing diuretics
Eplerenone (Inspra)
Spironolactone (Aldactone)
Aldosterone Antagonists site of action
Late distal tubule and collecting duct where ~2% of Na reabsorption occurs
Aldosterone cascade
Aldosterone binds to its receptors in the cytoplasm –> translocates into the nucleus and binds to DNA where is stimulates expression of aldosterone-induced proteins and causes the retention of Na and the excretion of potassium
Aldosterone antagonists bind?
At the receptor and block the effects of aldosterone causing the increased excretion of sodium and increased reabsorption of K
Potassium sparing diuretics main therapeutic uses?
Used with other diuretics to spare K
Heart failure
Spironolactone therapeutic uses are helpful in?
Primary (adrenal adenoma) and Secondary (overactivity of RAS) hyperaldosteronism
In pts with hepatic cirrhosis
Potassium diuretics adverse effects?
HYPERkalemia
Spironolactone: gynecomastia, sexual impotency, decreased libido and altered clearance of digitalis glycosides