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Flashcards in diuretics Deck (30)
1

what are forces that favor filtration?

-glomerular hydrostatic pressure 60 mmHg (pushing out)
-bowman's capsule colloid osmotic pressure of 0 (pulling in)

2

what are forces that oppose filtration?

bowman's capsule hydrostatic pressure 18 mmHg (pushing against)
glomerular capillary osmotic pressure 32 mmHg (pulling in)

3

what is the net filtration pressure in the glomerular capsule?

10 mmHg

4

what is the best way to increase urine output?

increase perfusion to kidneys by increasing BP, which increases filtration pressure

5

how is GFR normally preserved?

autoregulation: maintaining constant RBF over a range of systemic BP with MAP 50-150 mmHg
*HTN pts. have higher GFR when RBF is constant
*CHF pts. have decreased RBF and GFR

6

describe autoregulation

-myogenic: increased arterial pressure stretches afferent arteriolar wall then a reflex constriction occurs; decreased arterial pressure causes arteriolar dilation
-tubuloglomerular: decreased RBF leads to decreased GFR which results in afferent arteriolar dilation which increases GFR and RBF and restores filtration
-renin released, causes conversion of angiotensin I into II (aldosterone follows angiontensin II as well) causing vasoconstriction and increased GFR

7

what makes up urine besides water?

solutes
-electrolytes: primarily sodium, potassium, chloride, and bicarbinates
-waste products: creatinine
-pharmacologic metabolites

8

what determines urine excretion rate?

filtration rate - reabsorption rate + secretion rate

9

what are uses for diuretics?

-reduce HTN (decrease intravascular fld. vol.)
-treat pulmonary and peripheral edema
-electrolyte and pH corrections (hyperkalemia)
-reduce ICP, brain bulk
-prevent ARF d/t ischemic insult
-drug clearance

10

which drugs are loop diuretics?

-furosemide (Lasix)
-torsemide (Demadex)
-bumetanide (Bumex)
-ethacrynic Acid (Edecrin)

11

what is the MOA of loop diuretics?

inhibit reabsorption of NaCl in ascending loop of Henle
-stimulate production of prostaglandins (vasodilation, increased RBF)
*non increase in GFR

12

describe loop diuretics

-used more to decrease intravascular fld. vol.
-most effective diuretic class
-works faster than thiazide diuretics
-rapid excretion of drugs (used in ER for OD pts.)

13

what are some clinical uses of loop diuretics?

-rapid intravascular fld. removal
-hyperkalemia
-acute pulmonary edema
-kidney stone extraction, lithotripsy
-reduce intracranial pressure (systemic diuresis and decreased CSF production; used w/ mannitol)

14

what are concerns with loop diuretics?

-hypokalemia (potentiates digitalis toxicity; enhances NMB)
-ototoxic (permanent or transient deafness
-potassium replacement may be needed
-cardiac dysrhythmias can occur
-fld. vol. replacement may be indicated (orthostatic hypotension, hemoconcentration like increased BUN, Hct)
-mild hyperglycemia

15

what drugs are thiazide diuretics?

-chlorothiazide (Diuril)
-chlorthalidone
-indapamide (Lozol)
-hydrochlorothiazide (Microzide, Esidrix)
-benzthiazide
-cyclothiazide
-metolazone (Zaroxolyn)

16

what is the MOA of thiazide diuretics?

-inhibits reabsorption of NaCl in loop, proximal and distal tubules
-decrease HTN by diuresis, vasodilation (SNS in peripheral vascular smooth muscle d/t decreased total body stores of Na+
-excretion of Na+, Cl-, Bicarb, Mg++ and ultimately K+

17

what are clinical uses of thiazide diuretics?

-reduces edema (edema from CHF)
-reduces intravascular fld. vol (HTN)
-renal failure
*used in combination with antihypertensive drugs

18

what are effects of thiazide diuretics?

-decreased K+, Mag++, Cl-
-hypochloremic metabolic alkalosis
-hyperglycemia
-hyperuricemia (gouty arthritis)
-hypokalemia (potential for digitalis toxicity, cardiac dysrhythmias, muscle weakness, neuropathy, enhance NMB)
*potassium replacement may be indicated
*fld. vol. replacement may be indicated (orthostatic hypotension, hemoconcentration)

19

what drugs are osmotic diuretics?

-mannitol
-urea

20

how do osmotic diuretics work?

-work at the proximal convoluted tubule and loop of Henle
-osmotic diuresis
-increased plasma osmolarity
*does not alter GFR

21

describe osmotic diuretics

-large molecular weight molecule (pulls water with it)
-filtered but is too large to reabsorb (filters fast!)
-acute expansion of intravascular fluid vol.
-use in craniotomies to reduce brain bulk
-decrease in CSF production

22

what are side effects of osmotic diuretics?

-increased intravascular fld. vol. until filtered
-rebound HTN in non-intact BBB (pulled in brain causing HTN in brain and increased ICP, resulting in rebound HTN)
-pulmonary edema
-can exacerbate CHF
-electrolyte disturbance (not often)
*give slow

23

describe mannitol use

-reduction of intracranial pressure and brain mass
-reduction of high intraocular pressure when unable to lower pressure by any other mechanism
-urinary excretion of toxic materials
*may need something to keep BP up

24

describe the aldosterone antagonist?

-spironolactone (Aldactone)
-competes with aldosterone
-allows secretion of Na+ and Cl-
-used in combination with thiazide diuretics, to hold on to K+

25

what are uses for spironolactone?

used for edema r/t
-CHF
-Liver Cirrhosis
*both lead to increased aldosterone
*side effect may be hyperkalemia

26

describe potassium sparing diuretics

-triamterene, amiloride
-spares potassium independent of aldosterone
-weak diuretic effects
-distal tubules and collecting ducts
-increased excretion of Na+, Cl-, and bicarb
*not used alone as an anti-HTN or for edema
*used in combination with loop diuretics to limit potassium losses in the distal tubule

27

what are side effects of potassium sparing diuretics?

primarily hyperkalemia
*use catiously w/ pts. at risk for hyperkalemia, pts. using ACE inhibitors and NSAIDS (both cause increased K+)

28

describe carbonic anhydrase inhibitors (CAI)

-acetazolamide (Diamox), methazolamide (Neptazane)
-works in proximal tubules
-inhibiting CA blocks NaBicarb and causes diuresis
-used in glaucoma to reduce intraocular pressure by decreasing aqueous humor

29

what are side effects of CAIs?

-hyperchloremic metabolic acidosis
-drowsiness
-paresthesia
-renal calculi

30

what are some combination drugs with diuretics?

-spironolactone/HCTZ (Aldactazide)
-triamterene/HCTZ (Dyazide)
-Hydralazine/HCTZ (Hydra-Zide)
-Clonidine/Chlothalidone (Clorpress)