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