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139 Cards in this Set
- Front
- Back
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Myocardial cells are high in ____ and low in ___ and ___.
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high-K
low- Na, Ca |
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Pacemaker cells are located in the
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SA node
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Slow ____ influx opens calcium channels
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sodium
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Slow ____ ion channels account for the heart's refractory period.
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calcium
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In cardiac action potential, phase 0 represents
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upstroke/ rising phase
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In cardiac action potential, phase 1 represents
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early rapid repolarization
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Phase 0 upstroke occurs due to
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rapid influx of sodium into cell
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In cardiac action potential, phase 2 represents
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plateau - slow influx of Ca causes K outflow
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In cardiac action potential, phase 3 represents
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final repolarization - moving back toward equilibrium
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In cardiac action potential, phase 4 represents
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resting potential diastolic repolarization
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What is the primary difference between cardiac and skeletal muscle?
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no calcium-mediated plateau phase in skeletal muscle
intercalated disks fire faster and carry action potential faster |
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____ fibers arise from segments _____ of the spinal cord to stimulate the AV node and myocardium.
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sympathetic, T2-T4
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The ____ nerve provides parasympathetic control to the heart by depression of the ____.
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vagus, AV node
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The right sided nerves affect the ____ node, and the left sided nerves affect the ____ node.
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SA, AV
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Halothane, enflurane and isoflurane all depress automaticity of
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the SA node,
minimal effects on AV node |
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Administration of anticholinergics frequently results in
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junctional tachycardia
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Activation of alpha 1 and beta receptors potentiates ______ and causes _____.
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catecholamines, dysrhythmias
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Depressing calcium channels has _____ effects.
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antiarrhythmic
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Local anesthetics affect sodium channels. At low levels they are _______, and at high levels they cause ______.
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therapeutic (lidocaine),
deperession of SA node and dysrhythmia or CV collapse |
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In excitation-contraction coupling, everything start with a ____ receptor stimulation. This causes a chain of events in which ___ is the energy source that the cells run on (From Ca and ATP). _____ breaks down cAMP and Ca is sequestered in the ______ when not in use.
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beta receptor, cAMP,
phosphodiesterase, sarcoplasmic reticulum |
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Thin filaments are _______ and thick filaments are ______.
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actin, myosin
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Describe the 4 steps of the contractility cycle of muscle
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1. myosin cross bridge attaches to actin myofilament
2. working stroke - myosin head pivots and bends as it pulls on the actin filament, sliding it toward the M line 3. as new ATP attaches to the myosin head, the cross bridge detaches 4. as ATP is split into ADP and Pi via ATP hydrolysis, cocking of the mysoin head occurs |
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_____ is the most notorious local anesthetic for cardiac toxicity, and is treated with intralipid 10 cc/kg bolus.
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bupivicaine
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What effects do anesthetics have on contractility?
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-depress contractility by decr Ca entry into cells
-halothane and enflurane have most negative inotropic effects -N20 and ketamine have minimal effects - locals, esp bupivicaine, ropivicaine and tetracaine cause myocardial depression by inhibitng Ca transport |
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LVEDP should be ____ mmHg
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10-15
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The AV valve closes at the end of
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diastole
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Diastolic pressures are much higher (60-80 mmHg) in the
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periphery
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CVP waveform reflects
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atrial pressures
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A wave of CVP
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Atria contracts
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C wave of CVP
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early ventricular contraction, and bulging of tricuspid into R atrium during isovolumetric systole
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What does the v wave on CVP represent?
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atrial venous filling against a closed tricuspid
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What does x descent on CVP represent?
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atrium relaxaes and tricuspid valve moves downward
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What does y descent on CVP represent?
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filling of ventricle after tricuspid valve opening
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Systole represents ventricular _____ and diastole represents ventricular ______. Both are energy dependent and active processes
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ejection, filling
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What is the main determinant of CO in normal hearts?
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venous return (preload)
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SV x HR =
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CO
normal=5-5.5 L |
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CO / BSA =
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CI
normal=2.6-4.2 CI relates peformance of heart to the size of the individual |
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A sudden drop in BP (getting out of bed) results in ______ and therefore decreased stroke volume. However, heart rate increases due to _____ activity, and normal CO is maintained.
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low venous return,
sympathetic activity |
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Is CI a reliable indicator?
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no, has a wide normal range, depends on HR, decreases are much more meaningful during exercise, usually signifies gross impairment
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What is a better measure of cardiac performance than CI?
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mixed venous O2 sat
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SVO2 (mixed venous O2 sat) reflects ______.
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oxygen extraction
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What are the 4 values derrived from SV02 monitoring?
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CO, O2 sat, O2 carrying capacity of Hgb, and O2 consumption
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What are the 5 determinants of stroke volume?
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1. preload/venous return
2. afterload 3. contractility 4. wall motion abnormalities 5. valvular dysfunction |
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This law of the heart represents the relationship between EDV and CO.
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Starling's law of the heart
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What effect does an incr in preload have on SV?
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if preload incr, so does SV!
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If a pt has heart failure, their heart is weak, enlarged and doesn't perform well. Therefore, as volume is added...
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stroke volume decreases because pumping capacity is overwhelmed
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What is the main factor in ventricular filling?
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diastolic time
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Increases in HR occur at the expense of
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diastolic filling
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Atrial kick accounts for ____ % of ventricular filling
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30+
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If the ventricles are less compliant, this means they will be
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difficult to fill, stiff
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What are the 2 causes of diastolic dysfunction?
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problems w active relaxation (Contributes to stiffness) and increased passive stiffness
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Hypertrophy, ischemia, and asynchrony of the ventricles cause problems with
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active relaxation
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Hypertrophy, fibrosis, pericardial disease (restrictive, prevents heart from expanding) or external compression (From fluid in cavity) cause problems with
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increased passive stiffness
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During hypertrophy, an enlarged septum may eventually lead to
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LV obstruction! uh oh!
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This term is defined by systolic wall tension or arterial impedance to ejection
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afterload
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LaPlace's Law
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stress = pressure in heart x radius / 2xthickness (h)
S = P x R / 2h |
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Ohms Law
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SVR = 80 x (MAP - CVP)/CO
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80 x (pulm art pressure - L atrial pressure) / CO =
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Pulm Vasc Resistance
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Pulmonary vascular resistance refers to the afterload of
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the R ventricle
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Anesthetics are vasodilators and typically _____ Afterload.
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decrease
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CO is ____ related to afterload.
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inversely
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The failing heart is very _____ sensitive.
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afterload
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The ____ ventricle is thin walled and is more sensitive to changes in afterload than the _____ ventricle.
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right, left
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You don't wanna give phenylephrine to patients in
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heart failure -- buckle under incr afterload
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Bad hearts thrive with pharmacologic ______.
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afterload reduction
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Contractility is dynamic. It is increased by _______ And decreased by ________.
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incr: SNS, meds, hormones
decr: anoxia, acidosis, ischemia |
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RVEF may be measured by _____, but afterload will affect its readings.
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PA catheter
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EF =
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(EDV-ESV)/ EDV
normal EF= 55-75% |
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EF does not reflect contractility, it is ______ dependent.
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load (preload/afterload)
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In the left ventricular pressure-volume loop, end diastole occurs with _____ and end systole occurs with ______.
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isovolumetric contraction, aortic valve closure
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Ischemic heart disease is present in ____ % of pts undergoing sx.
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30%
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Risk factors for ischemic heart disease include
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male gender, incr age, high chol, HTN, smoking, sedentary, genetics
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Angina pectoris occurs when
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myocardial O2 demands exceed supply
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Describe angina pectoris
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chest, jaw, left arm pain/pressure/heaviness;
dyspnea-like |
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What are non-cardiac causes of angina?
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GI problems, costochondritis, esophogeal spasm
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How is ischemia diagnosed?
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standard EKG and exercise EKG; nuclear stress imaging, stress echocardiography, coronary angiography
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What are the limitations of angiography?
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cannot predict stability of plaques
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Unstable angina nad MI are most commonly due to plaque rupture in what vessels
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<50% stenosis
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Most frequent cause of intraop MI?
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plaque rupture
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How do you treat ischemic heart disease?
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- lifestyle modification
- meds (antiplatelet drugs, beta blockers, Ca channel blockers, nitrates, ace inhibitors, statins) - revascularization w CABG or percutaneous intervention (Stents) |
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This is a hypercoagulable state that occurs with STEMI, NSTEMI or UA
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acute coronary syndrome
build up of RBCs and platelets |
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Diagnosis of an MI requires 2 out of these 3 criteria:
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1. chest pain
2. serial EKG changes 3. incr and decr of serum cardiac enzymes |
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Treatments for MI:
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reperfusion therapy (clot busting w tPa, stenting), angioplasty (balloon introduced stents), CABG
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Complications of acute MI
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1. dysrhythmia (vfib, vtach, afib, bradyarrhythmias, heart block)
2. pericarditis 3. mitral regurg 4. Ventricular septal defect 5. CHF/cardiogenic shock 6. myocardial rupture |
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RV MI is rare because
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RV has better O2 supply/demand ratio, and receives coronary blood flow in systole and diastole
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What is the clinical triad for RV MI?
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hypotension, incr JVP, clear lung fields
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How does treatment differ for RV MI?
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vasodilators and diuretics may worsen situation, 3rd degree block common, inotrope may be needed
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Pulmonary edema occurs with ____ heart problems.
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L sided
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Periop MI is more likely in ____ surgeries (5-15% prevalence).
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high risk vascular and emergency surgeries
urgent hip sx 5-7% risk, elective hip sx < 3% |
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Perioperative MIs are more frequently _____ type, and may be heralded by nagging ____ and ____. Plaque rupture is caused by _____ mediators.
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NSTEMI, Tachycardia, ST depression, inflammatory
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Catecholamines, hormones, changes in blood viscosity, cortisol levels, and tissue plasminogen activators can all cause _____ states.
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hypercoagulable
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The highest risk of ischemia, infarction and death occurs after acute ____ days and recent ____ days MI.
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1-7 acute, 18-30 recent
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Several interventions can be made based on a preop cardiac evaluation, which include:
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- forego surgery
- modification of surgical procedure - delay case for treatment of unstable symptoms - medical therapy w beta blockers, statins, alpha 2s - modification of post op monitoring - send to ICU - change location of care (Surgicenter vs hospital) - coronary revascularization |
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High surgery-specific cardiac risk is considered cardiac risk greater than ___%. It includes the following surgery types.
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5%,
emergent major operation, aortic or other major vascular surgery, peripheral vascular surgery, prolonged surgery w large fluid shifts and/or blood loss |
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Intermediate surgical risk (less than 5%) include these procedures:
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head and neck, intraperitoneal/intrathoracic, orthopedic, prostate
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Low surgical risk of cardiac events (<1%) occurs w these procedures
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endoscopic procedures, superficial procedures, cataract sx, breast sx
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Major clinical predictors of incr cardiac risk:
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- unstable or severe angina
- recent MI 7-30 days - decompensated CHF - symptomatic dysrhythmias or high grade AV block - severe valvular disease |
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Moderate clinical predictors of incr cardiac risk:
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-mild angina
-prior MI by hx of EKG -compensated CHF -DM -renal insufficiency |
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Minor clinical predictors of incr cardiac risk:
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-advanced age
-abnormal EKG (LVH, LBBB, ST-T changes) -dysrhythmia -low functional capacity -hx of CVA -uncontrolled HTN |
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Functional capacity is excellent with a score of > 7 METs, which includes
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- carry 24 lbs up to 8 steps
- carry 80 lb object - outdoor work - recreation (Ski/jog) |
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A functional capacity score of moderate (4-7 METs) indicates these signs:
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- have sex without stopping
- walk 4 mph on level ground - light outdoor work - light recreation (dance, skating) |
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A poor functional capacity (<4 METs) indicates these signs:
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- shower/dress without stopping
- lighit housework - walk 2.5 mph on level ground - recreation (golf, bowling) |
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What pts require pre op non-invasive cardio testing?
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2 of the following: high risk sx, low exercise tolerance, moderate clinical risk factors
pts w low functional capacity |
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Which pts don't require non invasive pre op cardio testing?
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pts w/ stable, medically optimized CAD or good exercise tolerance may proceed (even w/ high or intermediate risk surgery and moderate clinical risk factors)
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The risk of MI after having PCI or stenting is not decreased until...
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complete endothelialization occurs and dual antiplatelet therapy completed
bare metal stent 3 mo. drug eluting stent 12 mo. |
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What is the implications of prior CABG on OR candidates?
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cabg within 5 yrs and no change in medical condition is considered safe for OR
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What is the risk of casual use of beta blockers? (They aren't indicated for everybody!)
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increased risk of stroke and death when used casually
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When are beta blockers indicated for perioperative pharmacologic mgmt?
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vascular, high and intermediate risk sx.
pts already on beta blockers pts w multiple moderate clinical risk factors pts w major clinical risk factors or ischemia on preop testing |
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Alpha agonists are helpful in pts with CV risk factors because...
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analgesic, sedative and sympatholytic effects may help decr cardiac events (like dex)
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How are statins helpful in pts w CV risk factors?
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anti-inflammatory effects help stabilize coronary plaques
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What are 2 other drugs (Besides alpha agonists, beta blockers and statins) that are helpful in CV risk pre op candidates?
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insulin and aspirin
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Fact or fiction??
IV nitroglycerin prevents myocardial ischemia during surgery |
Fiction!
no documented advantages, may adversely affect loading conditions and complicate fluid mgmt |
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What are some important strategies for intraoperative mgmt of CV risk pts?
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-prevent myocardial ischemia by optimizing myocardial O2 supply and demand
-monitor for ischemia and treat effectively |
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The 2 primary causes of ischemia are
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decr O2 delivery,
incr O2 requirements |
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What causes decr O2 delivery?
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decr coronary blood flow
tachycardia hypotension hypocapnia coronary spasm- prinzmetal angina anemia hypoxia |
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What causes incr O2 requirements?
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SNS stimulation
tachycardia HTN (incr wall stress) incr myocardial contractility incr preload incr afterload |
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This is the single most important determinant of myocardial demand
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HEART RATE
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Tachycardia is an increase in HR at the expense of...
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diastole
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The LV is perfused during
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diastole
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The _____ is most sensitive to ischemia during systole.
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endocardium
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What are the induction considerations for CV patients?
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-avoid meds that incr HR and BP (ketamine)
-blunt sympathetic response to tracheal intubation w local anesthetics, beta lockers, and swift technique |
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What are the maintenance considerations for CV pts?
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maintain stable hemodynamics by balancing control of SNS while avoiding hypotension
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What considerations should be made for CV pts in choosing muscle relaxants?
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avoid meds that incr HR and BP (pancuronium) or cause histamine release and hypotension (atracurium, morphine)
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What considerations should be made for continuous regional analgesia in CV pts?
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-intensive post op analgesia may decr incidence of perioperative cardiac complications
-important to avoid intraop hypotension |
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Fact or fiction??
IAs are bad for the heart? |
FICTION!
they actually protect the heart from ischemia and provide anesthetic preconditioning |
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What considerations should be made for continuous regional analgesia in CV pts?
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intensive post op analgesia may decr incidence of perioperative cardiac complications, important to avoid intraop hypotension
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Fact or fiction??
Sedation is the safest form of anesthesia in CV pts? |
fiction!
acceptable technique for minor procedures, but incomplete local anesthesia and analgesia increase stress response! |
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Fact or fiction??
Local anesthesia has the lowest risk in CV pts? |
Fiction!
acceptable for a wide variety of minor procedures, but incomplete local anesthesia and analgesia incr stress response and may induce ischemia! |
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What are the benefits/drawbacks of 12 lead EKG?
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inexpensive and sensitive, but impractical in the OR --
use immediately post op and days 1&2 post op |
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What are the benefits of automated ST analysis?
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highly sensitive, diagnoses up to 95% of ischemia episodes with simultaneous monitoring of leads 2 and 5
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What are the benefits/drawbacks of PA catheters?
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unreliable measure of ischemia, indicated in high risk pts undergoing sx w large fluid shifts, not shown to alter outcomes
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What are the benefits/drawbacks of TEE?
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sensitive measure of ischemia, even before EKG changes occur, costly, extensive training needed, misses ischemic events during induction
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What are the main goals of treating intraoperative myocardial ischemia?
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TREAT THE UNDERLYING CAUSE!
- tachycardia: rate control w beta blockers - hypertension: vasodilator w nitroglycerine - hypotension: vasoconstrictor (phenylephrine, ephedrine, epi) be careful w inotropes and fluids to avoid driving myocardial O2 demand even higher |
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What are post op mgmt techniques in pts at risk for myocardial ischemia?
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post op shivering dramatically increases myocardial O2 demand; continue beta blockers post op, plan for smooth emergence and intubation, post op pain and bleeding may lead to disaster!
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Pts undergoing cardiac transplant may present with _____ support.
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inotropic, vasodilator, and mechanical circulatory support
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Pts undergoing cardiac transplantation require intensive intraoperative monitoring and _____ therapy is often used after separation from CPB.
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inotropic
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The failing heart is dependent on circulating....
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catecholamines
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Abrupt decreases in sympathetic outflow may cause acute ______.
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decompensation
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Becoming unconscious during anesthesia causes ______ catecholamines.
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decreased
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