Studydroid is shutting down on January 1st, 2019



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which is the more potent vasoconstricotr, ADH or angiotensin II
ADH (vasopressin
what happens ot arterial BP during inspiration in spontaneously breathing pt?
decreases b/c with inspiration, bl flow from lungs to left side of heart decreases, causing a decrease in stroke volume and arterial BP
what is the funiton of the capillaries?
allow exchange of O2, fluid, nutrients, lytes, hormones, and other stuff b/t bl. and interstitial spaces
change in any of what 4 factors may prmote peripheral edema
  • decreased plama colloid osmotic pressure
  • increase capillary hydrostatic pressure
  • increase interstitial protein (lymphatic obstruction)
  • increase permeability in the capillary wall
what % of CO is delivered to the highly perfused organs
75% of resting CO (even though they constitute only 10% of total body mass)
what is the colloid osmotic pressure of albumin?  how does albumin contribute to the total colloid osmotic pressure in plasma?
22 mmHg
it is responsible for app. 80% of total colloid osmotic pressure
what determine blood flow thoruhg an organ or tissue?  whose law?
pressure gradient and resistnace to flow
Ohm's law: Blood Flow = (P1-P2)/R
what are the 2 most important determinants of oxygen delivery to the tissues?
CO and arterial O2 content
How does hypercapnia affect the cerebral and systemic vasculature?
vasodilation of both
Doe hypercarbia affect pulmonary vascular resistance?
it increases pulmonary vascular resistance
How does severe acidosis alter pulmonary vascular resistance and systemic vascular resistance?
increase PVR and decreased SVR
describe the flow pattern in th eleft and right coronary arteries during systole and diastole?
right: flow is maintained druign both systole and diatole
left: during early systole, compression of the vasculature causes brief cessation of flow
resting coronary artery blood flow in ml/min? as % of CO?
225-250 ml/min
4-5 % of CO
How is coronary artery perfusion pressure coalculated?
CorPP=aortic diastolic pressure (AoDP) - PCWP
nl 60-160 mmHg
what most determines coronay blood flow?
myocardial metabolism
as myocardial metabolism increases, coronary arteries dilate and increase coroanry flow (vasodilation theory)
what is the most potent local vasodilator substance released by cardiac cells?
Adenosine
O2 consumption rate of the heart?
8-10 mlof O2/g/min
what 4 factors determine myocardial O2 demand?
  • HR
  • contractility
  • preload
  • afterload
what cardiovascular parameter correlates best with myocardial O2 consumption?
HR
describe myocardial preconditioning
short-term rapid adaptation to brief ischemia such that during a subsequent, more severe ischemic insult, myocardial necrosis is delayed
describe the cellular mechanisms that mediate myocardial preconditioning
  • activation of adenosine receptors
  • protein kinase C
  • ATP
what anesthetic agents can trigger of modulate the myocardial preconditioning response?  what anesthetic agent can antagonize the affect?
  • volatiles mimic preconditioning and can tirgger intracellular events that lead to myocardial prtoeciton that lasts long after anesthesia is over
  • opioids or adenosine delivered into coronary ciculation
  • ketamine antagonizes this effect
what layer of the ventricle has highest metabolic demand and is most vulnerable to ischemia: subendocardium or subepicardium
subendocardium
define rhythmicity
the ability of cells ot generate action potentials automatically ona rhythmic or regular basis
identify the only site through which cardiac impulses can be transmitted from the atria to the ventricles.  normally they pause at this site is how long?
AV node
100 milliseconds
in what segemt of the cardiac conduction system is the action potential conducted slowest? fastest?
slow: AV node
fast: Purkinje fibers
what is the function of the purkinje system?
synchronizes left and right contraction
what are the intrinsic firing rates of the SA node, AV node, and purkinje fibers
SA: 60-100
AV: 40-60
purkinje: 15-40
what cardiac electrical event is represented by the P waave? the T wave? PR interval
P: atrial depolarization
T: ventricle depolarization
PR interval: action potential passing through the AV node
what ion controls the resting membrane potential and what ion controls threshold?
K: membrane potential
Ca controls threshold
does hypocalcemia increase or decrease the excitability of the nerve and cardiac muscle?
increases membrane excitability.  the threshold becomes more negative, so the membrane potential and threshold approach each other and cells are m ore excitable
an increase in Ca conentration will stabilize the cardiac cell (decrease excitability).  an increase in conentrationof what other ion decrease excitabilty?
Mg
Ca and Mg ions are membrane potential stabilizers
is the heart equally innervated by the parasympathetic and sympathetic system?
No,
sympathetic: innervates atria, ventricle, AV and Sa node
parasympathetic: AV, SA and atria only (innervation arises from the dorsal motor nucleus of the vagus nerve in the medulla of the brain)
the pt with wolff-parkinson-white syndrome develops afib.  how should it be treated?  what drugs should be avoided?
if life threatening hypotension develops: electrical cardioversion
if afib is toleratied: IV procainamide
Avoid: verapmil or digitalis b/c can speed conduction through accessory pathway
how does CVP compare with PCWP if pulmonary HTN is present?
CVP will be elvated b/c right ventricular output will be decreased, so right atrial pressure and CVP will increase
what is the most ominous sign of coronary artery disease?
unstable angina that occurs during rest ismost common sign.  it is ominous of severity and frequency of attacks increase
which test is best for dtermining coronary artery disease: resting ECG, holtor monitor ECG, stress (exercise) ECG, or stress (exercise) thalium testing
exercise ECG has high specifity of 90%
what identifies myocardial ischemia during surgery?
ST segment depression of >1 mm
what is theprimary goal of anesthesia in pt with CAD?
maintain CV stability, avoid hypotension, hypertension and tachycardia
during surgery, pt with anginat the is well controlled with NTG suddenly becomes tachycardic and hypertensive with no ECG signs of ischemia.  what should you do?
increase anesthetic depth
then if needed use beta blocker such as esmolol
a pt with CAd is having non-cardiac surgery PB 155/115, CO 3, PCWP 22.  what would be an appropriate antihypertnesive?
appears ot be due to increased SVR (preload is increased and CO is down)
Nitroglycerin
what are the 2 most significant risk factors identified by the Goldman Cardiac risk Index for noncardiac surgery?
  • myocardial infarction
  • S3 gallop
what is the incidence of perioperative reinfarction for non-cardiac surgery at 0-3 months, 4-6 months, and after 6 months for a pt wiht a history of myocardial infarction?
  • 0-3:27-37%
  • 3-6:11-16%
  • >6: 5-6%
Elective surgery is best no performed until how mcuh time ahs elapsed after an MI?
6 months
which type of surgery cause the biggest risk of perioperative reinfaction
intrathoracic or intrabdominal surgery lasting longer than 3 hours
you pt had an MI 3 months ago and is now requireing surgery and needs GA.  which of the following will most increase the chance of reinfarction: labile hemodynamics. modest increase in HR, stable angina
labile hemodynamics
identify appropriate maintenance agents for a pt with CAD.  what agent would you avoid?
volatiles (if pt has good ventricular function)
low EF: opioid-based without nitrous( cna produce cardiac depression)
Avoid nitrous
3 signs of poor righ ventricular function
  • systemic venous congestion
  • peripheral edema
  • congestive hepatomaegaly
  • pulsating neck veins indicate venous congestion decondary to right vent. failure
how is left ventricular compliance assessed?
doppler electrocardiography
in general what usually causes left ventricle diastolic dysfunction
a decrease in left ventricular compliance (myocardial ischmia, pericardial effusion, shock)
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