Module C: CV, Renal, Hematologic Flashcards
Role of Intracellular Ca+ in CV system
- essential to actin-myosin interaction (causing contraction)
- higher the intracellular Ca+ = ^ force of contraction (inotropic effect), ^ conduction velocity (chronotropic effect-HR), and vasoconstriction
- decreased intracellular Ca+ causes the opposite
4 factors affecting Cardiac Output
- Preload- ventricular filling pressure (pressure on ventricular walls at end of diastole)
- Afterload- force against which heart must pump blood- reflected by systemic vascular resistance (SVR)
- Contractility- how well cardiac muscle contracts
- Heart Rate
Primary action of diuretics
inhibit Na+ reabsorption in early portions of the nephron (PCT, Loop of Henle)
5 Types of Diuretics
- loop
- carbonic anhydrase inhibitors
- thiazides
- potassium-sparing
- osmotic
Thiazides
- most commonly used oral diuretics
- moderate nature tic effect
- aka low-ceiling diuretics (^ dose does not promote more diuresis- flat dose-response curve)
- few side effects
- inhibit NaCl reabsorption in early distal tubule
- Tx for HTN, edema associated with CHF, nephrolithiasis and diabetes insipidus
Carbonic Anhydrase Inhibitors
- rarely used as diuretic
- used for glaucoma and acute mountain sickness
- side effect:metabolic acidosis
Loop Diuretics
- most potent diuretics
- inhibit NaCl reabsorption by inhibiting Na/K/2Cl transport system in ascending limb of Loop of Henle
- aka high-ceiling diuretics (diuresis increases with dose)
- used for acute pulmonary edema
- can cause K+ secretion, can also increase secretion of Ca and Mg into filtrate
Potassium-Sparing Diuretics
- two types: Aldosterone receptor antagonists and epithelial sodium channel blockers
- reduce Na+ absorption in late distal tubule and collecting duct (do not exchange Na for K)
- used for excess aldosterone and to counteract hypokalemic diuresis
Osmotic Diuretics
- increase blood osmolarity (water is drawn from interstitial and transcellular spaces into blood)
- freely pass into filtrate but not easily reabsorbed resulting in increased filtrate osmolarity
- used to decrease ICP, intraocular pressure, cerebral edema and to increase urine volume
Edema
accumulation of fluid in either interstitial spaces or body cavities due to increased hydrostatic pressure or decreased colloid osmotic pressure in the plasma
What causes increased hydrostatic pressure
heart and/or kidney failure
How is colloid osmotic pressure determined
by amount of Na+ and proteins in the plasma; decreased colloid osmotic pressure is due to low protein diet and/or hepatic disease
Lasix (Furosemide)
- loop diuretic
- strong natriuretic effect
- aka high-ceiling diuretics
- side effects: variety of electrolyte abnormalities
- PO or IV
- used for edema associated with CHF, liver failure or kidney disorder; also for HTN
Apo-Hydro (Hydrochlorothiazide)
- thiazide diuretic
- most frequently prescribed thiazide
- HTN, edema
Diamox (Acetazolamide)
- carbonic anhydrase inhibitor
- Tx of acute mountain sickness and glaucoma; rarely used as diuretic
Aldactone (Spironolactone)
- aldosterone inhibitor (K+ sparing)
- competitively blocks aldosterone binding reducing sodium reabsorption and accompanying secretion of K+
- long duration of action
- used to prevent hypokalemia and in Tx of primary hyperaldosteronism
Mannitol
- osmotic diuretic
- increase osmotic pressure of plasma
- Tx of cerebral edema and to reduce ICP, acute glaucoma (reduces intraocular pressure)
- as diuretic, used to improve renal function in oliguric phase of acute renal failure
- used to promote renal excretion of toxins in OD or poisoning
- primary adverse effect: eccessive plasma volume expansion which can lead to CHF and edema
Blood pressure equation
BP = CO x SVR(PVR)
antihypertensives work on reducing either or both factors
4 categories of Antihypertensives
- diuretics
- sympatholytics - sympathetic nervous system
- angiotensin inhibitors - renin-angiotension-aldosterone system
- vasodilators - vascular smooth muscle
Natriuresis
excretion of sodium in urine
How do diuretics reduce BP
by increasing renal sodium excretion
Thiazides in Tx of HTN
- most frequently used diuretics for HTN
- one example: Diuril (Chlorothiazide)
- typically 2 or more antihypertensives needed for Tx
- may cause hypokalemia by typically only in high doses
- advantage is protection against osteoporosis (probably due to decreased urinary excretion of calcium)
Loop Diuretics for Tx of HTN
-less effective at reducing BP if normal kidney function exists; therefore, more commonly used where abnormal kidney function exists
Potassium Sparing Diuretics for Tx of HTN
- ex. Aldactone (Spironolactone)
- cause mild natriuresis and mild antihypertensive effect
- primarily used in conjunction with thiazides to counteract K+ loss of thizades
2 classifications of sympatholytic agents
- adrenergic blockers, or antagonists (a or b)
2. central-acting agents
Adrenergic Blockers/Antagonists
a1 Antagonists
-ex. Minipress (Prazosin)
-cause vasodilation and reduce SVR
-disadvantages:
:reflex cardiac stimulation and increased circulating Norepi
:activation of renin-angio-aldo system = fluid retention (therefore must be given in conjunction with a diuretic)
Adrenergic Blockers/Antagonists
B Antagonists or Blocks
-can be selective or non-selective
-reduce HTN by
: blocking B1 receptors on heart=reduce HR and force of contraction
:block B1 on juxtaglomerular cells=prevent stimulation of renin-angio-aldo system
:reduce sympathetic outflow from CNS
Central Acting Agents
ex. Aldomet (Methyldopa)
- too many side effects
- used when other antihypertensives are ineffective or during HTN emergencies
- stimulate a2 receptors in CNS inhibiting sympathetic outflow from brain stem to heart, vessels, etc
- cause vasodilation without greatly reducing HR and SV
- cause immunologic effects ie. hemolytic anemia
