Cardiac Flashcards
What determines the “dominance” of coronary blood flow?
The blood supply to the AV node:
RCA in 85-90% of people
LCx in 10-15% of people
When in PCI contraindicated?
left main disease where distal vessels are not protected by collaterals
diffuse/multivessel disease
no discrete lesion
What is the normal LVEDP (or PA occlusion pressure)?
6-15 mmHg
How is LV wall motion characterized by echocardiography?
normal: thickening > 30%
hypokinetic: thickening 10-30%
akinetic: thickening < 10%
dyskinetic: outward motion during systole
What are the determinants of myocardial oxygen consumption?
wall tension
contractility
heart rate
What is the equation of wall tension?
The Law of LaPlace:
T = P x R /2Th
T-tension, P-pressure, R-radius, Th-thickness
What are the determinants of myocardial oxygen supply?
coronary perfusion pressure (aortic diastolic pressure - LVEDP)
coronary vascular tone
coronary patency
arterial oxygen content
Is digoxin continue through heart surgery?
No, it is stopped 2 days (one half life) in advance to prevent toxicity after bypass
Do ß-blockers have more effect on heart rate or contractility?
reductions in HR occur with lower serum levels that depression of contractility
What is a normal Allen’s test?
Palmar flush occurs in < 7 seconds, indicating adequate collateral ulnar flow
Where is core temperature measured? Peripheral temperature?
Core temperature: esophageal, nasopharyngeal, bladder, tympanic
Peripheral: axiallary, rectal
How can you tell when the PA catheter advances from the RV into the PA?
1) Diastolic pressure is higher in the PA than in the RV
Normal RV: 20-25/0-5
Normal PA: 20-25/5-10
2) PA pressure tracing has a dichrotic notch from pulmonic valve closure
What is the normal PA occlusion pressure?
4-12 mmHg
What are the complications specific to PA catheter insertion?
arrhythmias
PA or RA perforation
tricuspid injury
What is the earliest and most sensitive sign of myocardial ischemia?
RWMA on echocardiography
What is the sensitivity, specificity, and predictive values of PAOP for myocardial ischemia?
Bad (40-60%)
What combination of ECG leads has the best sensitivity for detecting myocardial ischemia?
II and V5: 80%
V4 and V5: 90%
II, V4, and V5: 96%
*V5 has the best sensitivity of any single lead*
Is IV or inhaled anesthesia preferable for cardiac cases?
There is no consensus.
There is some data that inhaled anesthetics protect myocardium against ischemia-reperfusion injury.
Should isoflurane be used for patients with CAD?
There is no consensus.
Some data suggests coronary vasodilatation with isoflurance that decreases blood flow and causes coronary steal
Why should nitrous oxide be avoided after cardiopulmonary bypass?
It could expand remaining air bubbles in the coronary and cerebral circulation.
Why is pancuronium nice for cardiac surgery?
long-lasting
vagolytic effects usually counteracted by the presence of ß-blockers
How do you treat intra-opertive ST depressions?
increase oxygen supply: correct hypotension, hypoxemia and anemia
decrease oxygen demand: correct hypertension and tachycardia
Should you give prophylactic nitroglycerin to patients undergoing CABG?
No, it does not prevent myocardial ischemia
Should PA occlusion pressure be monitored continuously?
No, the gradient between PAOP and PA diastolic pressure should be noted on insertion, then PA diastolic pressure can be followed
What are the strategies for blood conservation during cardiac surgery?
pre-operative autologous donation
pre-operative erythropoietin
intraoperative normovolemic hemodilution
TXA
cell saver
What are the considerations for intraoperative normovolemic hemodilution?
blood, platelets, and clotting factors are spared the stress of bypass, improving coagulation
not recommended if Hct < 33
not recommended with left main disease or severe aortic stenosis
What is the dose of heparin before bypass? ACT goal?
300 (200-400) units per kg
ACT goal > 400
Why does the LV need to be vented on bypass?
To prevent distention of the LV with blood from:
bronchial veins
pleural veins
Thebesian veins
aortic insufficiency
What kind of oxygenator is used on the CPB machine?
membrane oxygenator (more economical and efficient, less traumatic to blood)
What is the CBP machine primed with (500-1000mL)?
a balanced salt solution, albumin, and mannitol
What should MAP be during cardiopulmonary bypass?
50-70 in patients at low risk for cerebral embolization
80-100 in patients at high risk for cerebral embolization
If using cerebral oximetry to monitor cerebral blood flow during CPB, what is the goal?
70% of baseline or >40% saturation, whichever is higher
How is hypertension treated during CPB?
increasing the depth of anesthesia
**pump flow rate should NOT be reduced**
What is the normal pump flow rate on CPB
2-3 L/min/m2 (for both adults and children)
Why is muscle relaxant given during CPB?
prevent diaphragmatic movement
prevent shivering
How do you assess adequate perfusion during CPB?
urine output
no metabolic acidosis
PmvO2 40-45 mmHg
cerebral oximetry
What is the V/Q ratio of the CBP machine?
2L of gas for every 1L pump flow
Why should hypocapnea be avoided on CPB?
decreased cerebral blood flow
decreased O2 delivery (left shift in curve)
hypokalemia
What is the difference between alpha-stat and pH stat strategies?
alpha stat maintains a constant ratio of OH-/H+
pH stat maintains a constant pH
When is alpha stat used? pH stat?
alpha stat for adult CPB
pH stat for pediatric deep hypothermic circulatory arrest
What is the goal hematocrit during CPB?
18-20%
What are cardioprotective strategies during CPB?
When crossclamp is off:
avoid tachycardia
prevent and treat V-fib
vent the left ventricle
maintain coronary perfusion pressure
When crossclamp is on:
cardioplegia
hypothermia
When should retrograde cardioplegia be used?
severe obstructive coronary lesions (to avoid poor distribution of cardioplegia)
significant aortic insufficiency
How long can the aorta be crossclamped?
60-120 minutes (the shorter the better)
Why would the urine become pink on CPB?
massive hemolysis
How warm should the patient be before coming off pump?
core temperature: 37oC
peripheral temperature: 35oC
What energy is used for internal defibrillation?
5-10 J
Why do blood glucose levels rise during CPB?
NPO starvation state
sympathetic activaiton
hypothermia reduces insulin production
cardioplegia contains dextrose
Is is platelet dysfunction or decreased clotting factors that causes most non-surgical bleeding after CPB and heparin reversal?
platelet dysfunction
What is the checklist for coming off CPB?
ABG normalized
patient warm
adequate ventilation
rate/rhythm/contractility treated
afterload treated
preload visualized on TEE
What considerations go into starting an inotrope to come off CPB?
patient age
pre-op ventricular function
duration of cross clamp
success of surgical repair
**IABP should be considered if predicted EF < 25%**
What is the dose of protamine?
1 mg per 100 units of the initial heparin bolus
How does protamine reverse heparin?
Heparin is highly negatively charged.
Protamins is highly positively charged.
They form a stable, inactive salt.
What is wrong with giving too much protamine?
It is an anticoagulant due to its inhibition of platelet aggregation and direct thrombin inhibition.
What are the effects of protamine on cardiovascular function (i.e., why do we give it slowly)?
1) systemic hypotension due to histamine release (side effect)
2) anaphylactic or anaphylactoid reactions (decreased SVR and PVR, patient on NPH isulin at risk)
3) catastrophic pulmonary hypertension and bronchoconstriction (mediated by C5a anaphylotoxins and thromboxane, steroids and antihistamines ineffective)
What is the principle of IABP?
increased myocardial oxygen supply during diastole
decrease myocardial oxygen consumption during systole
Is PAOP a surrogate for LVEDV after CABG?
no, they are poorly correlated, likely due to changes in ventricular compliance
Where is the optimal position of an IABP?
between take-off of the left subclavian artery and the take-off of the renal arteries
What are the contraindications for IABP?
significant aortic insufficiency
aortic pathology (aneurysm, dissection, severe plaque)
sepsis
coagulopathy
What factors decrease VAD output?
hypovolemia
increased afterload (SVR or PVR)
How is ACLS different in a patient with a VAD?
external chest compressions are contraindicated as they may dislodge the catheters
What is the primary concern in a patient undergoing LVAD placement?
RV failure (hypoxia, hypercarbia, and acidosis must be avoided)
What equation describes a pressure gradient across a valve?
Gorlin’s equation
pressure gradient = {flow rate/(K x valve area)}2
What symptoms are associated with aortis stenosis?
angina
syncope
congestive heart failure
How should you think about pre-medication with valvular lesions?
AS: good, prevents tachycardia
AI: good, prevents increased SVR
MS: be careful, hypercapnea can worsen PVR and RV failure
MR: maybe, hypercapnea can worsen PVR, but decreased SVR can improve forward flow
What are the hemodynamic goals for aortic stenosis?
HR: 60-70 and sinus (dependent on atrial kick)
preload: full (maximize LV filling)
afterload: maintain (coronary perfusion)
contractility: maintain
What are the hemodynamic goals for AI?
HR: 80-90 (minimize time in diastole)
preload: maintain
afterload: reduce (SVR is driving force for regurgitant flow)
contractility: support (dilated LV ineffective)
What are the hemodynamic goals for MS?
HR: 60-70 (need time to fill LV)
preload: full (maximize LV filling)
afterload: maintain
contractility: support (disuse atrophy of LV)
What are the hemodynamic goals of MR?
HR: 80-90 (avoid overfilling of LV and annular dilatation)
preload: maintain
afterload: reduce (encourage forward flow)
contractility: support (dilated LV ineffective)
What are the anesthetic consideration for valve replacement with AS?
avoid hypotension and hypoxia
maintain sinus rhythm (particularly during atrial cannulation)
hypertophied LV may be poorly protected by cardioplegia
LV still poorly compliant after valve replaced
What are the anesthetic considerations for valve replacement with AI?
increased SVR must be combined with increased inotropy (e.g., ephedrine and epinehrine are better than phenylephrine)
retrograde cardioplegia is often necessary
inotropic support is often necessary
What are the anesthetic considerations for valve replacement with MR?
decreased SVR promotes forward flow
may need inotropic support for chronically dilated LV after valve is fixed
Should patient with bifascicular or trifascicular block get a PPM prior to anesthesia?
No, they rarely progress to CHB intraoperatively
What is the three-letter code that describes pacemaker modes?
1st letter: the chamber(s) paced (A, V, or D)
2nd letter: the chamber(s) sensed (A, V, or D)
3rd letter: response when intrinsic activity is sensed (Triggered, Inhibited, or D)
What are the three pacing modes of modern pacemakers?
asynchronous (e.g., VOO)
single chamber (e.g., AAI, or VVI)
dual chamber (e.g., DDD)
What is the difference between DDD and DDI?
In DDD mode, AV sequencial pacing is maintained whether the atrial beat is sensed or paced; in DDI mode AV sequencial pacing only happens when the atrial beat is paced
Why does intra-operative hyperventilation increase heart rate in a patient with a PPM?
“rate response” pacing increase heart rate in response to motion or changes in minute ventilation
What is an AICD measuring? How does it respond?
R-R interval
If there is a run of short R-R intervals, it will choose anti-tachycardia pacing or shock dependin on the algorithm
What does a magnet do to a PPM? To an AICD?
A magnet will put a PPM in a fixed-rate pacing mode.
A magnet will disable the ICD functions of an AICD but will not affect its pacing functions
If a patient with an AICD goes into VT or VF intraoperatively, what do you do?
stop electrocautery
remove the magnet and wait ~12 sec to charge
if no response, proceed with external defibrillation
Is ESWL contraindicated in patients with PPMs?
No
AICDs should have a magnet placed
Is ECT contraindicated in patients with PPMs?
devices should be reprogrammed into an asynchronous mode and tachycardia detection should be disabled
How does pacemaker-mediated tachycardia occur?
In DDD mode, a PVC is conducted retrograde up the AV node and sensed as an atrial beat, which triggers ventricular pacing.
**most PPMs can detect and terminate this process**
What are the risks of asyncrhonous pacing?
R-on-T leading to VF
competing nonperfusing rhythms
How does a dipyridamole stress test work?
it vasodilates normal coronary arteries causing “coronary steal” and revealing at-risk myocardium
What is equalization of diastolic pressures classically a sign of?
cardiac tamponade: CVP = PADP = PAOP
**often not seen after cardiac surgery because compression is not homogeneous**
What is pulsus paradoxus? Kussmaul’s sign?
drop in SBP with inspiration of > 10 mmHg
distention of neck veins on inspiration
Does the normal heart experience ischemia during tamponade?
No, reduced coronary perfusion is offset by reduced oxygen consumption (less preload and afterload)
What are the hemodynamic goals in a patient with tamponade?
Fast: stroke volume is limited so CO is dependent on HR
Full: to maximize filling with poor compliance
Tight: to maximize end-organ perfusion is setting of reduced CO
Describe induction options for cardiac tamponade.
Patient prepped and draped and surgeon scrubbed and gloved prior to induction
awake w/ local: usually not possible
inhalational: often too slow
etomidate or ketamine w/ muscle relaxant: minimize PPV until tamponade relieved
Why are patient considered “preload-dependent” after heart transplant?
Donor heart sinus node is denervated from the vagus nerve and only modulate HR in response to catecholamines
Do you need to give glycopyrrolate or atropine with neostigmine in a patient who has had a heart transplant?
Yes, slow reinervation is possible and neostigmine can cause bradycaria
What is cardiac allograft vasculopathy?
accelerated atherosclerosis in the transplanted heart
What are the five RCRI predictors of cardiac risk?
History of:
ischemic heart disease
CHF
cerebrovascular disease
insulin-dependent diabetes
Cr > 2.0
How long does dual anti-platelet therapy need to be continued after stent placement?
4-6 weeks after bare metal stent
6-12 month after DES
Does clonidine premedication prevent adverse cardiac events?
No, nonfatal cardiac arrest and significatn hypotension were higher with clonidine in the POISE-2 trial
