Cardiac Anesthesia Flashcards
On what type of CPB pump can excessive pressure build up proximal to an outflow occlusion, potentially causing the tubing to rupture or the tubing connections to separate?
A roller pump
Flow of a roller pump is predictable and depends on the revolutions per minute of the pump. Although retrograde flow is not possible, if there is outflow occlusion to the pump, excessive pressure can build, causing the tubing to rupture or the tubing connections to separate.
On what type of CPB pump can retrograde flow occur and how?
The Centrifugal Pump
It operates on a principle of a constrained vortex, where the rotator (impeller) is housed within a rigid container shaped like a cone.
Flow depends on the pressure differential created by spinning cones that create a negative pressure (pressure drop), propelling fluid forward.
Flow varies depending on pump preload and after load.
In a patient with Vfib refractory to repeated attempts at defibrillation and lidocaine administration, what is the most appropriate drug management?
The administration of bretylium
At what point in the arterial waveform is an intraarterial balloon pump inflated?
At the dicrotic notch, which marks the start of diastole so that there is better coronary perfusion
For what procedures and what patients is prophylactic antibiotics recommended against infective endocarditis?
It is only recommended for dental/skin/respiratory tract procedures
In high risk patients with a prosthetic valve or unprepared congenital heart disease(CHD) or recently repaired CHD with prosthetic materials
Describe pacemaker syndrome
It is characterized by hypotension, vertigo, fatigue, and weakness.
It occurs when pacer leads fail, leading to symptoms which initially indicated the pacemaker placement.
Describe the different phases of the cardiac action potential
1) Phase 0 (UPSTROKE): at rest with rapid influx of Na+ causes DEPOLARIZATION (Na+ entry; decreased K+ permeability)
2) Phase 1 (EARLY RAPID REPOLARIZATION): partial repolarization (K+ out)
3) Phase 2 (PLATEAU): plateau phase, when Ca2+ is going in and K+ is going out
4) Phase 3 (FINAL REPOLARIZATION): the potential goes back down towards baseline as more and more K+ is driven out
5) Phase 4 (RESTING POTENTIAL and DIASTOLIC REPOLARIZATION): little ion flux occurring during diastole, when pacemaker cells spontaneously depolarize and “generate the cardiac rhythm” Na+ - K+ ATPase pumps K+ in and Na+ out; Diastolic depolarization allows a slow leakage of Ca2+ into cells
How do volatile anesthetics effect the SA and AV nodes?
They depress the SA node (with NO effect on the AV node)
What is the most resistant arrhythmia to cardioversion?
Atrial flutter, often needing 200 joules of biphasic current energy
Which current is superior in cardioversions; biphasic or monophasic current?
Biphasic current is superior to monophasic current
How does blood flow differ between the left and right heart?
The left ventricle is supplied ONLY during diastole
Right-sided coronary blood flow is CONTINUOUS throughout the cardiac cycle (because the lower pressure in the RV compared to the LV causes substantially less extravascular compression during systole)
What is the resting coronary blood flow rate? What percentage of the cardiac output goes to the heart?
250 mL/min in an adult
5% of CO
What is the best measurement of ventricular function (in the absence of anemia and hypoxia)?
Measurement of mixed venous oxygen saturation (MVO2)
What do the x-axis and the y-axis represent on the Frank-Starling curve?
x-axis: LV volume (i.e. LVED volume)
y-axis: LV pressure/work (i.e. cardiac output)
Normal value for SVR
900-1500 dynes cm5
Increasing the afterload has what effect on stroke volume (SV)?
Increasing afterload DECREASES SV
What is the most likely valvular pathology in a young pregnant patient presenting with increasing SOB?
Mitral stenosis
What is the most common cause of mitral stenosis?
Rheumatic
What is the most likely disease process in a patient with a high PCWP and a low LVEDP?
Mitral Stenosis or Pulmonary HTN
NYHA Classification
I. Completely asymptomatic
II. Comfortable at rest, symptomatic with “ordinary physical activity”
III. Comfortable at rest, symptomatic with “less than ordinary physical activity”
IV. May be symptomatic at rest, symptomatic with any physical activity
What ECG leads correspond to the lateral heart? inferior heart? antero-septal heart?
Lateral heart: lead I, V5, V6
Inferior heart: leads II, III, aVF
Ant/Sept heart: leads V1-V4
What is the most likely ECG abnormality seen intraoperative in a patient with acute ischemia?
ST elevation
What component of the vascular tree has NO direct sympathetic innervation?
Capillaries
Where does the sympathetic outflow derive from?
The Thoracolumbar Spine
What is the cause for vasovagal syncope?
It is a result of reflex activation of both vagal and sympathetic vasodilatory fibers
MOA of Digoxin and its elimination
Blocks Na+, K+ = ATPase to cause less Na+
which leads to Ca2+ influx and increased contractility (therefore, calcium administration potentiates digoxin toxicity)
*Prolongs AV conductance
Renal elimination
MOA of Adenosine
Suppresses AV nodal conduction
MOA of Amiodarone
Depresses SA and AVnode
*anti-adrenergic effect may cause an atropine-resistant bradycardia and hypotension during general anesthesia
What does Dopamine stimulate at low doses, intermediate doses, and high doses?
At low dose (o.5-3 mcg/kg/min): stimulates dopa 1 receptors
At intermediate dose (3-10 mcg/kg/min): stimulates beta receptor
At high dose (10-20 mcg/kg/min): stimulates beta and alpha1
MOA of Dobutamine. Half life?
Dobutamine is a synthetic catecholamine that is a DIRECT Beta 1 AGONIST with very limited Beta 2 and alpha 1 effects
It has NO alpha 2, no dopaminergic activity
It primarily acts as a VASODILATOR
Plasma half life is 2 minutes
MOA of Norepinephrine
It is the primary physiologic post-ganglionic sympathetic neurotransmitter
Acts as a direct alpha 1, alpha 2, and beta 1 AGONIST
MOA of Isoproterenol
A synthetic catecholamine that is a direct Beta 1 & 2 AGONIST
NO alpha stimulation
MOA of Milrinone
Phosphodiesterase inhibitor that is an INODILATOR, increasing intracellular concentrations of cAMP by inhibiting its breakdown.
In cardiac myocytes: postive inotropy, lusitropy, chronotropy, dromotropy as well as increased automaticity.
In vascular beds: vasodilatation
What is the half life of Nitroglycerin
1-3 minutes
How does potassium effect a pacemaker’s function?
Any acute INCREASE in K+ decreases the potential across the membrane, therefore making the pacemaker MORE likely to capture. (VICE VERSA)
(Hyperventilation may decrease likelihood of capture
Can cardiac oxygen extraction be increased via exercise?
NO. Cardiac oxygen extraction is near maximal under resting conditions and cannot be substantially increased during exercise.
By what percent is myocardial oxygen consumption of the heart decreased at 22 degrees Celsius WITHOUT cardioplegia solution compared to that of a normal heart?
[What is myocardial oxygen consumption of the heart normally; when empty and normothermic; when empty, hypothermic & has cardioplegia?]
Normal myocardial oxygen consumption is 10 mL/100g/min.
When the heart is empty and at 37 degrees Celsius, it is reduced to 5.5 mL/100g/min
When the heart is cooled to 22 degrees, its consumption decreases to 2 mL/100g/min, which is an 80% reduction from normal
Had cardioplegia solution been given, it would have been reduced to 0.3 mL/100g/min
What are the primary determinants of myocardial oxygen demand?
Contractility and wall tension
What is the appropriate management of cardiac tamponade?
“full, fast, and tight”
Full = maintain preload Fast = myocardial contractility should be slightly higher Tight = SVR is high
What is pulsus alternans indicative of on a arterial waveform?
It is a condition in which there are alternating smaller and larger pulse waves.
Commonly seen in LV Dysfunction
What is pulsus paradoxus indicative of?
Cardiac tamponade & sometimes RV infarction
A decrease in the blood pressure of > 10 mmHg with inspiration
What is pulsus parvus and pulses tardes indicative of on an arterial waveform?
Aortic stenosis
Characterized by a diminished pulse wave and delayed upstroke, respectively
What is the appropriate initial amount of energy to be set for biphasic cardioversion of atrial flutter?
50-100 Joules
Synchronized cardioversion of an adult with Aflutter requires less Joules than other tachydysrhythmias.
What does the S on the ECG tracing represent?
The S-wave is a small negative wave following the large R-wave. It represents depolarization in the Purkinje fibers
Describe coronary steal phenomenon
It cause dilation of healthy blood vessels which direct blood AWAY from ischemic areas and thereby worsen ischemia.
Describe ischemic preconditioning
Inhalational anesthesia may confer protection to the heart after an initial ischemic insult by delaying the onset of necrosis. This occurs within 2 hours of mild ischemic episodes. The effect passes, but is observed 1-3 days after the ischemia
It is believed to be the result of the activation of mitochondrial ATP-sensitive potassium channels, which results in decreased calcium levels in the myocytes.
How does supine position effect the audibility of murmurs from pulmonic stenosis?
Pulmonic stenosis leads to an outflow track obstruction, which is exaggerated during the supine position because of a larger end-diasoltic volume and greater stroke volume.
Therefore, the murmur is louder
What are contraindications for LVAD placement?
1) Severe aortic insufficiency
2) Severe mitral stenosis
3) ASD
What location of the aortic cross clamp causes the least hemodynamic effects?
An infrarenal cross clamp produces the least effect hemodynamically.
What are the criteria for diagnosing pulmonary HTN according to the ACC/AHA?
All 3 of the following must be present:
1) Resting mPAP > 25 mmHg
2) PCWP/LAP = 15 mmHg
3) PVR > 3 Woods units
(RVH is NOT required)
What does “chattering” or “fluttering” of the venous cannula during CPB indicate?
This occurs when compliant venous or atrial walls collapse against the annular intake opening as a result of inadequate blood volume or excessive siphon pressure.
This phenomenon is corrected by adding volume to the patient.
What is the function of the intra-aortic balloon pump?
It provides counter pulsation during diastole in order to do 2 things:
1) Increase coronary perfusion
2) Decrease afterload
Other benefits include:
- decreasing myocardial oxygen demand
- decreasing preload
- increasing cardiac output
What cardiac abnormality is associated with acute aortic dissection and aortic aneurysm formation?
Bicuspid aortic valve
What distinguishes a true ventricular aneurysm from a pseudo aneurysm?
A TRUE ventricular aneurysm’s lining consists of:
1) ALL the layers of the of the myocardial wall (MYOCARDIUM, ENDOCARDIUM, EPICARDIUM)
2) Tends to be located at the ventricular apex and appears as a dilated, dyskinetic area with myocardial thinning.
3) Usually occur within 90 days of anterior wall MI
4) Has a smooth transition btw normal myocardium and the aneurysm with a neck to maximal aneurysm diameter ratio of 0.9 - 1
5) Severe mitral regurgitation is common (but NOT a distinguishing trait)
Whereas, a ventricular PSEUDOANEURYSM:
1) Occurs at the side of a chronic ventricular rupture and is lined ONLY by PERICARDIUM.
2) Tend to saccular or globular in shape.
3) Most often the consequence of chronic ventricular rupture after MI and can also result from surgery, trauma, and infection
4) Has a neck to maximal aneurysm diameter ratio usually < 0.5
5) On CDF, noted bidirectional flow of blood btw the LV and the pseudo aneurysm (enters in systole and goes back to LV is diastole); turbulent flow
Both occur after myocardial infarctions.
During deep hypothermic circulatory arrest, how is the PaCO2 from an alpha-stat reading, effected?
Temperature and PaCO2 are directly proportional.
Therfore, as the temperature decreases, so do PaCO2 levels, because the partial pressure of CO2 decreases.
In patients with end-stage heart failure requiring surgery for ventricular assist device placement, what are the goals of anesthesia induction?
Heart rate is a very important determinant of cardiac output. Maintain a HR of 80-90 bp is vital.
What is the most common congenital cardiovascular anomaly? associations?
Bicuspid aortic valve
- associated with coarctation of the aorta
- male predominance
Which papillary muscle is MOST commonly affected by ischemia of the LV?
The posterior papillary muscle, which is fed by the posterior descending artery
What are some drug options for medical cardioversion of atrial flutter?
Amiodarone
Dofetilide (effective in 70-80%)
Ibutilide (effective in 63%) - risk of QT prolongation and tornadoes de pointes
NOT lidocaine (which is useful for the suppression of ventricular dysrhythmias)
What is the recommended heart rate to be maintained in patients with Mitral Regurgitation?
80-100 bpm
What are the effects of initiating CPB with a non-blood priming solution?
- Reduction of mean arterial pressure
- Reduction of blood viscosity
- Reduction in SVR
- Decrease in after load
