Cardiac/Thoracic Anesthesia

Question 0

What effect does hypothermia have on platelets?

Answer 0

Decreased temperature causes reversible sequestration in portal circulation

Question 1

Who needs prophylaxis against infective endocarditis?

Answer 1

Only needed in high risk patients undergoing high risk procedures

High risk patients:

• prosthetic heart valves
• history of infective endocarditis
• unrepaired congenital heart disease (or recently repaired)
• valvulopathy in transplanted heart

High risk procedures:

• Dental work
• Respiratory procedures
• Skin/musculoskeletal procedures

Question 2

What is the most sensitive indicator of left ventricular myocardial ischemia?

Answer 2

Wall motion abnormalities on echo

Question 3

What is normal O2 consumption at rest?

Answer 3

3.5 mL/kg/min

This is equal to 1 MET

For an average 70 kg person, this is about 250 mL/min

Question 4

What does the y-axis of the Frank Starling curve represent? What values can be used?

Answer 4

Left ventricular work

Can be represented by:
LV stroke work index
Stroke volume
Cardiac output
Cardiac index
Arterial blood pressure

Question 5

What does the x-axis of the Frank Starling curve represent? What values can be used?

Answer 5

Left ventricular filling pressure

Can be represented by:
LVEDV
LVEDP
Left atrial pressure
PA wedge pressure
CVP

Question 6

What can cause a rise in PA pressure during cardiopulmonary bypass?

Answer 6

Distal migration of the PA catheter (very common - should resolve if catheter is withdrawn 3-5 cm)

Inadequate ventricular venting / ventricular distention

Question 7

How does body temperature affect tissue metabolic rate?

Answer 7

For each degree Celsius below 38, tissue metabolic rate decreases approximately 5%

Question 8

How might malposition of the aortic cannula during cardiopulmonary bypass present? What about the venous cannula?

Answer 8

Aortic cannula - unilateral facial blanching

Venous cannula - facial or scleral edema

Question 9

Pts with bicuspid aortic valves are predisposed to what other cardiac abnormality?

Answer 9

Aortic dissection

Question 10

How does an intra-aortic balloon pump work? What are common indications? What are the contraindications?

Answer 10

Deflates just before systole, reducing aortic pressure and afterload, which enhances LV ejection and reduces wall tension and O2 consumption

Inflates during diastole, just after closure of the aortic valve, which increases diastolic aortic pressure and coronary blood flow

Common indications include cardiogenic shock, failure to wean from CBP, severe MR, or as a bridge to transplantation

Contraindications include AI, aortic disease, and severe peripheral vascular disease

Question 11

What special mechanism makes epinephrine so useful in the treatment of Vfib?

Answer 11

Epinephrine reduces the ventricular fibrillation threshold and cellular refractory period, thereby stabilizing fibrillation

Question 12

What type of drugs are Milrinone and Inamrinone? How do they work? What is the difference?

Answer 12

PDE III inhibitors

• decreases in both SVR and PVR via vasodilation
• increases CO (inotropy) via increase intracellular calcium

Inamrinone is associated with thrombocytopenia and has largely been replaced by Milrinone

Question 14

What are the hemodynamic goals for aortic stenosis?

Answer 14

1) Decrease heart rate (increase filing)
2) Maintain sinus rhythm
3) Maintain/increase preload

4) Maintain/increase afterload
- in order to maintain coronary perfusion

5) Maintain PVR

Question 15

What are the hemodynamic goals for aortic regurgitation?

Answer 15

1) Maintain preload
2) Increase HR (less time for the blood to regurgitate)
3) Maintain contractility
4) Decrease/maintain afterload

Question 16

What are the hemodynamic goals for mitral stenosis?

Answer 16

1) Maintain/increase preload
2) Decrease HR (to increase injection time)
3) Maintain contractility
4) Maintain afterload
5) Decrease/maintain PVR

Question 17

What are the hemodynamic goals for mitral regurgitation?

Answer 17

“fast, full, forward” by avoiding bradycardia, ensuring adequate preload, and avoiding high afterload

Question 18

What are the hemodynamic goals of tricuspid stenosis?

Answer 18

1) Maintain/increase preload
2) Decrease/maintain HR
3) Maintain/increase afterload
4) Maintain PVR
5) Maintain contractility

Question 19

What are the hemodynamic goals of tricuspid regurgitation?

Answer 19

1) Maintain/increase preload
2) Maintain/increase HR
3) Maintain afterload
4) Decrease PVR
5) Maintain contractility

Question 20

What are the hemodynamic goals of pulmonic stenosis?

Answer 20

1) Increase preload
2) Increase HR
3) Maintain preload
4) Decrease PVR
5) Maintain contractility

Question 20

What is the difference between concentric and eccentric hypertrophy?

Answer 20

Concentric hypertrophy is increased wall thickness with no change in chamber size and is pressure related

Eccentric hypertrophy is increase wall thickness with increased chamber size and is volume related

Question 21

What happens if Protamine is given to a patient who has not received Heparin?

Answer 21

It can cause anticoagulant effects by binding to platelets and soluble coagulation factors

Question 22

What is normal daily production of cortisol? What about during times of stress?

Answer 22

Normal daily production is 15 to 20 mg. Under stress, production can increase to 75 to 150 mg/day.

Question 23

What is the Fick equation for cardiac output?

Answer 23

Oxygen consumption / [(arterial O2 content - mixed venous O2 content) x 10]

Question 24

What is normal myocardial O2 consumption?

Answer 24

8 to 10 mL/100 g/min

Question 25

What is resting coronary artery blood flow?

Answer 25

75 mL/100 g/min About 5% of cardiac output

Question 26

How much Protamine is required to reverse Heparin?

Answer 26

1.3 mg of Protamine for each mg of Heparin given

Question 27

What happens when a magnet is placed over a combined ICD/pacemaker?

Answer 27

The cardioversion and defibrillator functions are disabled Pacemaker settings are unchanged - EP must reprogram the pacemaker of changes are desired

Question 28

Which patients should be started on pre-operative beta blockade?

Answer 28

Any patients with 3 or more risk factors for CAD (ischemic heart disease, congestive heart failure, stroke, diabetes, chronic kidney disease) who are undergoing high risk surgery Patients already on beta blockers should continue them peri-operatively

Question 29

What nerve can be injured during surgical repair of a patent ductus arteriosus?

Answer 29

The recurrent laryngeal nerve (branch of CN X)

Question 30

What are the hemodynamic goals in HOCM/IHSS

Answer 30

Preload should be kept up Afterload should be kept up Heart rate should be kept down Contractility should be kept down Sinus rhythm should be maintained

Question 31

Describe the effects of aging on the CV system

Answer 31

Resting systolic function (EF) is unchanged, but exercise-induced increases in CO, SV, and HR are reduced Plasma levels of circulating catecholamines are significantly elevated - Due to decreased sensitivity of Beta receptors Increased vascular fibrosis and diastolic dysfunction, leading to increased reliance on the atrial kick Fibrosis of conduction system can lead to arrhythmia

Question 32

What are alpha-stat and pH-stat? What is the difference?

Answer 32

Alpha-stat and pH-stat are pH management strategies during cardiopulmonary bypass Alpha-stat is temperature uncorrected and maintains normocarbia and normal pH by assuming pt is at 37 degree celcius pH-stat is temperature corrected and maintains normocarbia and normal pH based on the pt's actual temperature - Infuses extra CO2 into the blood to compensate for decreased temperature

Question 33

What are the hemodynamic effects of aortic cross-clamping?

Answer 33

Increased arterial blood pressure above the level of the clamp - decreased blood pressure below the clamp Increased coronary artery blood flow Increased left ventricular wall stress Increased central venous pressure and pulmonary artery wedge pressure Decreased cardiac output Decreased oxygen extraction

Question 34

Describe the thermodilution method of determining CO. What causes under-/over-estimation?

Answer 34

A set volume of injectate at a set temperature is administered through the CVP port of the PA catheter and travels distally towards the thermistor at the tip The thermistor detects how much and how quickly the temperature changes after injection - a smaller change is interpreted as a larger CO (less time for injectate to mix) - a larger change is interpreted as a smaller CO (more time for injectate to mix) Any error that increases the temperature change (larger volume or colder temperature) will lead to an under-estimation of CO Any error that decreases the temperature change (smaller volume or warmer temperature) will lead to an over-estimation of CO

Question 35

How should you manage the pacemaker when a pacemaker-dependent patient comes to the OR?

Answer 35

Ideally, you should re-program the pacemaker to an asynchronous mode at a rate higher than the patient's intrinsic rate You can place a magnet over a pacemaker, but it is unreliable and manufacturer dependent

Question 36

During one-lung ventilation, what are some strategies to improve oxygenation?

Answer 36

Bronchodilators and suctioning CPAP to the non-ventilated lung PEEP to the ventilated lung Occluding the PA of the non-ventilated lung

Question 37

What are the risk factors for heparin resistance? What is the treatment?

Answer 37

Risk Factors: - Preoperative heparin therapy - Use of LMWH - Age over 65 Treatment is with FFP, AT3 concentrate, or recombinant AT3

Question 38

What are the important values of a TEG and what do they tell you?

Answer 38

``` Reaction time (R) is from time zero to initial clot formation - prolonged R values result from coagulation factor abnormalities, factor deficiencies, or heparin ``` ``` Coagulation time (K) measures speed of clot formation and strengthening - prolonged K values result from inadequate fibrinogen ``` ``` Maximum amplitude (MA) measure the strength of the fully formed clot - decreased MA suggest platelet dysfunction ``` Alpha angle is the speed of clot formation - decreased alpha angle results from inadequate fibrinogen

Question 39

Describe the response to bronchodilators seen in COPD patients

Answer 39

Response to bronchodilators follows a bell-shaped curve - mild or severe COPD patients usually show MINIMAL response - moderate COPD patients usually show GREATEST response

Question 41

How are PFTs used for risk stratification in thoracic surgery?

Answer 41

High risk factors include: - FEV1 less than 40% predicted - DLCO less than 40% predicted - VO2 max less than 10 mL/kg/min If PFTs are unfavorable, you can perform split-lung function testing

Question 42

In what situations is a bronchial blocker preferred over a DLT? What would a DLT be better?

Answer 42

It is better to use a blocker for: - selective lobar collapse - challenging airways - patients with trachs - children less than 12 - when post-op mechanical ventilation is expected DLTs are more reliable than blockers when you want true lung isolation

Question 43

How does hypothermia effect pH?

Answer 43

For each degree Celsius temperature decrease, the pH of blood increases by approximately 0.017

Question 44

How do TEE, EKG, and PCWP compare in terms of sensitivity for detecting myocardial ischemia?

Answer 44

From most sensitive to lease: - TEE - EKG - PCWP

Question 45

How can you estimate transvalvular pressure gradients based off of echo findings?

Answer 45

Bernoulli equation transvalvular pressure = 4 * (peak velocity)^2

Question 46

What are the risk factors associated with post-CBP acute kidney injury?

Answer 46

Creatinine over 1.2 Combined valve and bypass procedures Pre-op intra-aortic balloon pump Emergency procedures