Vasodilators Flashcards
Vasodilators MOA
direct smooth muscle relaxation, (production of intracellular NO, SNP and nitrates) (calcium channel blockers)
Alpha 1 antagonists
prazosin and labetolol
Alpha 2 agonists
clonidine and alpha-methyldopa
ACE Inhibitors
captopril and enalopril
____% of coronary artery perfusion to the LV is delivered during diastole
70-90%
What governs perfusion pressure?
aortic diastolic pressure
T/F: In the presence of ischemic heart disease, the collateral arteries are maximally dilated and coronary perfusion is largely pressure dependent
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Coronary Steal
narrowed coronary arteries are always maximally dilated, dilating nearby vessels may shunt blood away from these necessary pathways and cause further ischemia.
Thiocyanide/Cyanide toxicity
s/s: hypotension, blurred vision, fatigue, metabolic acidosis, pink skin, absence of reflexes, faint heart sounds
What dose does risk of cyanide toxicity increase?
> 4 mcg/kg/min, > 2 days of therapy
Thiocyanate Levels
therapeutic = 6-29 mcg/ml toxic = 35-100 mcg/ml fatal = >100 mcg/ml
Cyanide Levels
normal = <0.2, smoker = <0.4 toxic = >2 mcg/ml fatal = >3 mcg/ml
Tx of Toxocity
stop infusion, oxygen, treats acidosis.
hydroxocobolamine (precursor of vit B12)
sodium thiosulfate - donates sulfur group, breaks down thiocyanate
Alpha 1 Receptor Activation
increased intracellular calcium smooth muscle contraction peripheral vasoconstriction inhibits insulin secretion stimulates glycogenolysis and gluconeogenesis GI relaxation Mydriasis
Alpha 2 Receptor Activation
Inhibits neuronal firing in PNS and CNS
Sedation
BP drop
Analgesia
Uses of alpha agonists in anesthesia
post op shivering, reduce sedation needs
Alpha 2 Agonists and Cardiac Surgeries
reduce cardiac complications, overall mortality, cardiac mortality, MI
especially beneficial for vascular surgery
monitor for excessive hypotension and bradycardia
RAAS - Adrenal Gland response
release aldosterone
NA reabsorption and K excretion at distal tubule
RAAS - ADH
from posterior pituitary
water reabsorption at collecting duct
ACE inhibitors and hypertensive pt
good, decreased renal vascular resistance
improved RBF and GFR
ACE inhibitors and hypotensive pt
bad, deteriorate renal function d/t compensatory efferent arteriole constriction mediated by angiotensin 2 in blocked –> decreased GFR pressure –> acute hyperkalemia
T/F: ACE Inhibitors have increased hypotensive effect of diuretics, vasodilators and anesthetics
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Functions of calcium
signal transduction, CNS and heart
muscle contraction: smooth muscle, cardiac muscle, vessel
bone health
clotting cascade
How do verapamil and diltiazem enhance myocardial oxygen balance?
decreasing myocardial oxygen consumption by afterload reduction and/or negative inotropic effect. increase oxygen delivery through coronary vasodilation
