Cardiac/Thoracic Anesthesia Flashcards
What effect does hypothermia have on platelets?
Decreased temperature causes reversible sequestration in portal circulation
Who needs prophylaxis against infective endocarditis?
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
What is the most sensitive indicator of left ventricular myocardial ischemia?
Wall motion abnormalities on echo
What is normal O2 consumption at rest?
3.5 mL/kg/min
This is equal to 1 MET
For an average 70 kg person, this is about 250 mL/min
What does the y-axis of the Frank Starling curve represent? What values can be used?
Left ventricular work
Can be represented by: LV stroke work index Stroke volume Cardiac output Cardiac index Arterial blood pressure
What does the x-axis of the Frank Starling curve represent? What values can be used?
Left ventricular filling pressure
Can be represented by: LVEDV LVEDP Left atrial pressure PA wedge pressure CVP
What can cause a rise in PA pressure during cardiopulmonary bypass?
Distal migration of the PA catheter (very common - should resolve if catheter is withdrawn 3-5 cm)
Inadequate ventricular venting / ventricular distention
How does body temperature affect tissue metabolic rate?
For each degree Celsius below 38, tissue metabolic rate decreases approximately 5%
How might malposition of the aortic cannula during cardiopulmonary bypass present? What about the venous cannula?
Aortic cannula - unilateral facial blanching
Venous cannula - facial or scleral edema
Pts with bicuspid aortic valves are predisposed to what other cardiac abnormality?
Aortic dissection
How does an intra-aortic balloon pump work? What are common indications? What are the contraindications?
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
What special mechanism makes epinephrine so useful in the treatment of Vfib?
Epinephrine reduces the ventricular fibrillation threshold and cellular refractory period, thereby stabilizing fibrillation
What type of drugs are Milrinone and Inamrinone? How do they work? What is the difference?
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
What are the hemodynamic goals for aortic stenosis?
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
What are the hemodynamic goals for aortic regurgitation?
1) Maintain preload
2) Increase HR (less time for the blood to regurgitate)
3) Maintain contractility
4) Decrease/maintain afterload
What are the hemodynamic goals for mitral stenosis?
1) Maintain/increase preload
2) Decrease HR (to increase injection time)
3) Maintain contractility
4) Maintain afterload
5) Decrease/maintain PVR
What are the hemodynamic goals for mitral regurgitation?
“fast, full, forward” by avoiding bradycardia, ensuring adequate preload, and avoiding high afterload
What are the hemodynamic goals of tricuspid stenosis?
1) Maintain/increase preload
2) Decrease/maintain HR
3) Maintain/increase afterload
4) Maintain PVR
5) Maintain contractility
What are the hemodynamic goals of tricuspid regurgitation?
1) Maintain/increase preload
2) Maintain/increase HR
3) Maintain afterload
4) Decrease PVR
5) Maintain contractility
What are the hemodynamic goals of pulmonic stenosis?
1) Increase preload
2) Increase HR
3) Maintain preload
4) Decrease PVR
5) Maintain contractility
What is the difference between concentric and eccentric hypertrophy?
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
What happens if Protamine is given to a patient who has not received Heparin?
It can cause anticoagulant effects by binding to platelets and soluble coagulation factors
What is normal daily production of cortisol? What about during times of stress?
Normal daily production is 15 to 20 mg. Under stress, production can increase to 75 to 150 mg/day.
What is the Fick equation for cardiac output?
Oxygen consumption / [(arterial O2 content - mixed venous O2 content) x 10]
What is normal myocardial O2 consumption?
8 to 10 mL/100 g/min
What is resting coronary artery blood flow?
75 mL/100 g/min
About 5% of cardiac output
How much Protamine is required to reverse Heparin?
1.3 mg of Protamine for each mg of Heparin given
What happens when a magnet is placed over a combined ICD/pacemaker?
The cardioversion and defibrillator functions are disabled
Pacemaker settings are unchanged
- EP must reprogram the pacemaker of changes are desired
Which patients should be started on pre-operative beta blockade?
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
What nerve can be injured during surgical repair of a patent ductus arteriosus?
The recurrent laryngeal nerve (branch of CN X)
What are the hemodynamic goals in HOCM/IHSS
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
Describe the effects of aging on the CV system
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
What are alpha-stat and pH-stat? What is the difference?
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
What are the hemodynamic effects of aortic cross-clamping?
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
Describe the thermodilution method of determining CO. What causes under-/over-estimation?
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
How should you manage the pacemaker when a pacemaker-dependent patient comes to the OR?
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
During one-lung ventilation, what are some strategies to improve oxygenation?
Bronchodilators and suctioning
CPAP to the non-ventilated lung
PEEP to the ventilated lung
Occluding the PA of the non-ventilated lung
What are the risk factors for heparin resistance? What is the treatment?
Risk Factors:
- Preoperative heparin therapy
- Use of LMWH
- Age over 65
Treatment is with FFP, AT3 concentrate, or recombinant AT3
What are the important values of a TEG and what do they tell you?
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
Describe the response to bronchodilators seen in COPD patients
Response to bronchodilators follows a bell-shaped curve
- mild or severe COPD patients usually show MINIMAL response
- moderate COPD patients usually show GREATEST response
How are PFTs used for risk stratification in thoracic surgery?
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
In what situations is a bronchial blocker preferred over a DLT? What would a DLT be better?
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
How does hypothermia effect pH?
For each degree Celsius temperature decrease, the pH of blood increases by approximately 0.017
How do TEE, EKG, and PCWP compare in terms of sensitivity for detecting myocardial ischemia?
From most sensitive to lease:
- TEE
- EKG
- PCWP
How can you estimate transvalvular pressure gradients based off of echo findings?
Bernoulli equation
transvalvular pressure = 4 * (peak velocity)^2
What are the risk factors associated with post-CBP acute kidney injury?
Creatinine over 1.2
Combined valve and bypass procedures
Pre-op intra-aortic balloon pump
Emergency procedures
