CV II Flashcards
What frequency response should the ECG be?
0.05 to 100 Hz
What causes most pressure monitoring errors?
air within a catheter or transducer. Air not only decreases the response of the system but also leads to overdamping of the system. (underestimation of systolic and overestimation of diastolic)
At the completion of CPB and for 5 to 30 mins afterwards will the radial artery pressure be lower or higher than the aortic pressure
Lower
Which is the preferred technique for internal jugular catheter placement?
U/s guided
If an unsuccessful attempt at a subclavian vein cannulation occurs, can you try on the contralateral side?
NO….unless you get a CXR first. You don’t want bilateral pneumothoraces
T/F: PACs are indicated for all CPB patients.
False: in routine CPB it has little, if any benefit. May have benefit in high risk pts or those with special indications
Name some core temp sites
Nasal (tells you brain temp as well), bladder, tympanic membrane (also tells brain temp), esophageal (but shouldn’t routinely be used in CPB d/t its influence of blood returning from pump)
What are some examples of shell temperature?
rectal and skin
During reperfusion or neural ischemia can you give Ca2+ if the serum levels are low?
No. Although low Ca2+ can affect pumping function, administration of Ca2+ during these moments may worsen the outcome
Lead V5 is best for diagnosing what?
myocardial ischemia
Which two leads should detect 90% of ischemic episodes?
II and V5
Can the standard ECG leads detect posterior wall ischemia or RV ischemia?
No
Are noninvasive BP measures acceptable during CPB?
No
Although radial artery pressure is lower than aortic pressure soon after completion of CPB it is usually how much higher and why?
20-50 mmHg higher d/t decreased peripheral arterial elastance and wave summation
What are the advantages of placing a femoral artery arterial line?
Can assess central arterial pressure and there is an access site if should placement of IABP become necessary. The femoral artery is most easily entered using the seldinger technique
Narrow pressure on the arterial waveform is a sign of what?
pericardial tamponade or hypovolemia
Worsening aortic valvular insufficiency or hypovolemia may manifest as what on the art line tracing?
Increase in pulse pressure
Hypovolemia will do what to the a-line tracing with PPV (pulse paradox)
systolic will decrease with PPV. Positive intrathoracic pressure impedes venous return
How can contractility be judged on the a-line waveform?
Stroke volume?
Vascular resistance?
- contractility: rate of pressure rise during systole.
- stroke volume: area under the aortic pressure waveform from onset of systole to dicrotic notch
- vascular resistance: dicrotic notch high on waveform means high vascular resistance, dicrotic notch low on waveform indicates low resistance
What are the complications of arterial catheterization?
ischemia, thrombosis, infection, bleeding, false lowering of radial artery pressure immediately after CPB
What are 3 factors that affect CVP?
circulating blood volume
venous tone
RV function
*monitoring CVP is indicated for ALL cardiac surgical pts
cannulation of the left IJV is associated with which complications?
laceration of thoracic duct (chylothorax), laceration of brachiocephalic vein, laceration of superior vena cava
Which cannulation site carries the highest risk for PTX?
subclavian vein (SCV cannulation can be associated with compression of the central line during sternal retraction)
What do the A, C and V waves represent on the CVP?
A: atrial contraction (occurs in conjunction w/P wave)
C: RV contraction/bulging of the tricuspid into the RA (QRS)
X descent: latter part of systolic, tricuspid moves down
V: RA filling before opening of tricuspid (after T wave)
Y descent: after V wave when tricuspid opens and atrium empties
Cannon A wave cause…
when RA contraction occurs against a closed tricuspid
T/F: PCWP is a more direct estimate of LA filling pressures than PAP
true
What are the hallmarks of LV failure in the PAC?
simultaneous readings of high Pa pressures and wedge pressure in the presence of systemic hypotension and low CO
significant ischemia is often associated iwth ad ecrease in ventricular compliance, which is reflected in either a/an _____ in pa pressure or a/an _______ in PCWP
increase; increase
when is the best time during breathing to monitor PAC?
end expiration
What is the normal SvO2?
75% with 5-10% change being significant. decreased O2 delivery or increased O2 consumption leads to a lower SvO2
Thermodilutino
Intracardiac shunts will cause erroneous readings, tip of pulmonary catheter must be in the PA and not wedged
Accuracy vs precision
Capability of a measurement to reflect the true CO is accuracy.
Precision is the reproducibility of a measurement.
which is the gold standard for monitoring CO?
PAC
Hemolysis occurs during CPB which causes Hgb levels to _____.
Rise. Urine output should be maintained to avoid damage to renal tubules.
Which is the most important monitor of renal function during cardiac surgery?
urinary catheter
Which electrolytes will decline during CPB?
K+, Mg2+ (secondary to mannitol and improved perfusion)
Which meds should be held on the day of cardiac surgery?
ACE inhibitors, angiotensin receptor blockers, and (selectively) diuretics
-these are associated with hypotension following induction and ACE inhibitor use has been associated with kidney injury with cardiac surgery
Which types of drugs should be prepared prior to induction of anesthesia?
Vasopressor, vasodilator, inotrope, B-adrenergive blocker and heparin
Which meds suppress the stress response?
opioids.
- it suppresses in a dose-related manner until a max effect is reached…usually 8 mcg/kg of fentanyl
etomidate offers hemodynamic stability during induction but what is a disadvantage?
suppresses adreno-cortical function for about 24 hrs (may want to supplement with gluccocorticoids–cortisol/hydrocotisone?)
You’ll definitely postopone the central line insertion until after induction in these cases
ventricular rupture
ruptured or rupturing thoracic aortic aneurysm
cardiac tamponade
-need to open the chest ASAP
Inotropes used during cardiac surgery:
Epi*
dobutamine
dopamine
Phosphodiesterase inhibitors used in cardiac surgery:
milrinone
Vasopressors used in cardiac surgery
Phenylephrine*
norepinephrine*
vasopressin
Vasodilators used in cardiac surgery
Nitroglycerin*
nicardipine
nitroprusside
Antiarrhythmics used in cardiac surgery;
esmolol*
lidocaine*
Anticoags used in cardiac surgery:
heparin*
protamine
What is the most physiologically efficient method of combating hypovolemia?
using balanced salt solutions to augment intravascular volumes
What are the side effects of propofol and thioepental?
reducing BP by inducing venodilation with peripheral pooling of blood, decreasing sympathetic tone to decrease systemic vascular resistance and depressing myocardial contractility
At what level do you want to maintain the cardiac index during surgery?
1.8 L/min/M2
Which induction med can stimulate the CV system/
Ketamine (however in critically ill pts, the BP may still decrease b/c there is a depletion of catecholamines)
Can narcotics induce amnesia?
Can propofol depress the stress response?
No and no
__% of fentanyl is redistributed from the plasma in the first hour
98%
Sufentanil his __-__ times more potent than fentanyl?
where is the pKa compared to fentanyl?
how much is ionized?
Is it very lipid soluble?
- 7-10x more potent than fentanyl
- pKa of sufentanil is higher
- only 20% is ionized
- 1/2 as lipid soluble as fentanyl, lower Vd and recovery time
What is the cause of remifentanil’s rapid recovery time?
it’s subject to hepatic hydrolysis by nonspecifc tissue and blood esterases. Onset is 1 min and offset 9-20 mins. Can give it without impeding rapid recovery
Etomidate is __X more potent than propofol? What is it’s recommended dose range?
10x more potent
0.15-.3mg/kg
when inducing with etomidate what parameters would you expect to stay the same? (in normovolemic pts)
SV
LVEDV
contractility
What increases with administration of etomidate?
HR and CO
MAP and SVR will decrease
If pt has Hx of seizures is etomidate ok to adminsiter?
probably a no
Induction dose of propofol
2 mg/kg…there is direct myocardial depression above .75 mg/kg
What does propofol do to the baroreceptor reflex?
Resets the reflex so there isn’t an incr in HR after the reduction of BP
which is superior for cardiac induction, propofol or etomidate?
etomidate…propofol should be reserved for hemodynamically stable pts with good ventricular function
thiopental causes venous pooling and subsequently lowers….
preload
What does thiopental do to the baroreceptor reflex?
activates it and causes incr HR
With thiopental there is a dose related _____-inotropic effect d/t decrease in ____ influx
negative inotropic effect
d/t decr in Ca2+ influx
Ketamine causes increases in what 3 things?
HR
MAP
plasma epinephrine levels
*the stimulatory effect of ketamine depends on a robust myocardium and sympathetic reserve. In the absence of either, hypotension may ensue
In the setting of hypovolemia, major hemorrhage or cardiac tamponade which drug may be advantageous?
Ketamine
All volatile anesthetics produce dose-dependent ______ and also induce a reflex tachycardia which can be attenuated by administration of _____ or _______
vasodilation
beta blocker or opioids
which inhaled agents are more likely to reach concentrations consistent with stress response suppression during a customary induction period?
sevo and des
what are the advantages of pancuronium?
It has vagolytic effects which counter the vagotonia and bradycardia caused by higher doses of opioids
which type of induction may be beneficial for very sick pts with ow ejection fraction
inhalation induction but only if their stomachs are empty
If the pt is hypotensive and the induction drug used cause reduction in SVR and preload without affecting myocardial contractiliy (etomidate or midazolam with an opioid)….which action is best warranted?
phenylephrine instead of fluids
If the pt is hypotensive and HR is low and there is a strong possibility of myocardial depression (propofol was used or >0.5 MAC of a volatile) what would you consider giving a bolus of?
ephedrine or epinephrine
How do you determine R and L dominant pts
If the PDA comes off the RCA = R dominant (85%)
If PDA comes off L circumflex = L dominant
What does the Left Main divide into?
LAD and circumflex
What does LAD branch into?
diagonals and septals
- the LAD supplies anterior wall, continues and passes around apex of LV
What does the circumflex supply?
- supplies lateral free wall
- perfuses SA node in 40% of people
Right Coronary artery gives rise to what?
acute marginals and usually the posterior descending artery
What perfuses the SA node in 60% of people and the AV node in 80-90% of people?
RCA
What are determinants of oxygen supply?
- blood flow
- oxygen content
What can WE affect in terms of maximizing O2 content?
- high Hgb
- highly saturated blood
- high PO2
If pt develops ischemic waveforms what is your first action?
ensure 100% FiO2
Does chronic HTN shift the oxyHgb curve to the right or left?
RIGHT: shifting to the right is caused by warm temp, normal pH, high levels 2,3 DPG, this favors release of O2 to the tissues
formula for CBF
CBF = CPP/CVR
what increases CVR?
- increased O2
- decreased CO2
- decreased H+ (hyperventilation not necessarily good, can cause vasoconstriction)
- increased alpha (norepi) and cholinergics (ACH)
- vasopressin, angiotensin, thromboxane
- incr blood viscosity and hypothermia
what decreases CVR?
decr O2 incr CO2 incr H+ adenosine incr B-adrenergic activity prostacyclin
Which med is probably the most important metabolic blood flow regulator?
adenosine. from ATP breakdown–> causes coronary vasodilation and incr blood flow
which area of the heart muscle is most at risk for ischemia?
subendocardium
subendocardial CPP = DBP-LVEDP
When does most of the blood flow to the coronaries take place? systole or diastole?
Diastole 85%
Systole only 15%
- aim for normal to high DBP, low HR (more time in diastole), and low LVEDP
What is the difference between fixed or dynamic stenosis?
fixed: atherosclerotic plaque
dynamic: vasospasm or prinzmetal’s angina
What are the 3 determinants of myocardial O2 demand?
HR* (incr HR more than doubles demand)
contractility
wall stress
Most deleterious factor of myocardial oxygen demand is…
tahcycardia
-decreases blood supply AND increases demand
What are the contributors to wall stress?
Afterload, preload and wall thickness
- thicker wall = less stress
- low preload keeps wall stress low
What is coronary steal?
Ischemic areas are already maximally dilated and anything that dilates normal vascular beds diverts blood away from the ischemic areas.
Ex: Nitroprusside, iso is controversial…
coronary vasodilator steals blood from ischemic areas of heart
Acute CHF leads to _____ dysfunction
Chronic CHF leads to ______ dysfunction
- diastolic with decreased LV compliance and pulm congestion
- systolic with low CO and pulm congestion
In the anesthetized pt what could a new BBB or dysrhythmia indicate?
ischemia or infarction
Endocardial ischemia is denoted by what on the EKG
ST segment depression
ST segment elevation denotes what
transmural ischemia (full thickness)
Can you tell if there is ischemia by one PAP reading?
No, not diagnostic. Need to trend it
Is ST elevation after cross clamp removal expected?
Yes its not uncommon. Usually resolves with reperfusion. (watch for ventricular distention…increasing PAPs when on full CPB and heart is supposed to be empty)
What are the interventions for an air embolism?
Maintain high infusion pressures…phenylephrine gtt may help
Which is the best beta blocker to treat myocardial ischemia during cardiac surgery
esmolol….short 1/2 life
indiscriminate use of inotropes can do what to ischemia? what interventions should you implement first?
they can aggravate it…maximize preload, rate, rhythm and afterload first
milrinone
MOST potent smooth muscle vasodilator and also an inotrope
What dos IABP do to CPP and afterload
increases CPP
decreases afterload
Is LR okay for renal failure?
- No because it has lots of K+
- UOP is increased with the use of NS
- LR is most similar to plasma
What do membrane oxygenators act most similarly to?
the lungs, imposing a membrane btw the ventilating gas and the flowing blood, thereby eliminating direct contact btw blood and gas
what does the oxygenator do
removes CO2 as well as adds oxygen to proved the desired PaO2 and PaCO2
what does the arterial pump do?
supplies the energy to maintain systemic blood for arterial pressure and organ perfusion
Which is the most effective cannulation technique for totally diverting blood away from the heart?
bicaval cannulation
How is venous drainage usually accomplished? How is flow influenced?
- gravity (siphon effect)
- flow is influenced by CVP, height differential btw the pt and the H-L machine and resistance in the venous cannula tubing
Blood is returned to the systemic arterial system through what?
the arterial cannula
Venous reservoir receives drainage from what?
how does it act as a buffer?
- the pt
- acts as a buffer by adjusting fro fluctuation imbalances btw venous return and arterial flow
- if drainage is abruptly stopped or reduced the venous drainage provides a source of blood
what is an advantage to a closed venous reservoir?
eliminates gas-blood interface and reduces the risk of massive air embolism…because of the elimination of the gas-blood interface their use may be associated with less inflammatory response
What are the disadvantages with the roller pump?
- output is afterload independent, if the arterial line becomes occluded, high pressure will develop which may cause ruptures of connections in the arterial line.
- these also cause more damage to blood components and can result in massive air embolism if venous reservoir becomes empty
What are the advantages to centrifugal pumps?
- less risk of pumping massive air emboli into the arterial line
- less damaging to RBCs
_____oxygenators produce less blood trauma and microemboli, permit more precise control of arterial blood gases and improve pt outcomes compared with _____ oxygenators
membrane oxygenators; bubble oxygenators
_____ oxygenators functions similarly to the natural lungs, imposing a membrane btw the ventilating gas and the flowing blood and eliminating direct contact btw the blood and gas
membrane oxygenators
How are arterial CO2 levels controlled in the CPB machine?
flow of fresh gas through the oxygenator….arterial PO2 is controlled by varying FiO2 (fractional inspired oxygen)
What can excessive warming lead to in the H-L machine?
can lead to gases coming out of the solution and causing a GME (gaseous microembolism) and it could cause heating of the brain
why should cardiotomy blood be used sparingly?
Because it does pose some risk of microemboli and hemoylsis during CPB
What are the consequences of distention of the left heart during CPB
causes ventricular dysfunction, myocardial ischemia, increased LAP leading to pulmonary edema and hemorrhage, interferes with surgical exposure
What is the best way of evaluating the adequacy of Lv decompression
TEE
How long should the anesthetist wait after going on “full bypass” before arresting the heart
Wait 2 minutes before arresting heart to be sure there are no serious complications that can be managed by discontinuing CPB
What determines the cardiac output on the CPB
the pump flow rate which can be set at any level but is limited by the amount of venous return (venous return is influenced by the height of the operating table above the H-L machine, size of the venous cannula,, blood vol, and venous tone)
What is the goal for MAP during adult CPB? what is the lower limit of brain autoregulation?
- 50-60
- during CPB autoregulation avgs 66mmHg
What should clinicians strive to maintain SvO2 at?
greater than or equal to 80%….normal is about 75%
As body temp decreases which way does the oxyHgb curve shift?
Left. that means the partial pressure of O2 in the tissues has to be lower for Hgb to deliver the same amount of oxygen
When the ascending aorta is unclamped where do you want perfusion pressures?
higher. to maintain adequate myocardial perfusion pressures in pts with cardiac hypertrophy
Postoperatively after a CPB surgery what may the lungs exhibit/
lower PaO2, edema from increased pulmonary hydrostatic pressure, ischemia/reperfusion, atelectasis from lung deflation
In pts with AS, the early use of ________ agonists such as _____ is indicated to prevent drops in bp than can lead to sudden death
- alpha adrenergic agonists
- phenylephrine
In mitral regurg which states can lead to increase in LV volume, reduction in forward CO, and an increase in regurgitant fraction (RF).
Bradycardia can cause this…..the heart rate should be kept in the normal to elevated range
In tricuspid regurg, what should be avoided? if inotropic support is necessary, which drugs should be used?
- high airway pressures during pulmonary ventilation and agents that can increase Pa pressure should be avoided
- inotropic agents that dilate the pulmonary vasculatures should be used: dobutamine, isporterenol or milrinone
If a pt has AS and mitral regurg which takes precedence/
treat the AS first because that can lead to deadly introperative situations
What is an example of a fixed obstruction and a dynamic obstruction?
fixed: AS
dynamic: HOCM (obstruction is only present for part of the cardiac cycle
pressure overload leads to which type of hypertrophy and volume overload leads to which type?
pressure: concentric (Law of LaPlace)
volume: eccentric
What do you wand to do to preload perioperatively in the pt with AS?
preload augmentation is necessary to maintain a normal stroke volume
Where do you want the HR in the pt with AS?
Maintainn a HR in the 50-70 range to allow time for systolic ejection across the stenosed valve. IT IS ESSENTIAL TO MAINTAIN A SINUS RHYTHM (since the ventricular compliance is decreased and there is impared early filling in diastole, the atria contribute up to 40% of LV filling)
How should contractility be altered in the pt with AS
It should be maintained….beta blockade is not well tolerated and can lead to LVEDV increase and a decrease in CO
How should SVR be maintained in the pt with AS
systemic blood pressure reduction does LITTLE to decrease afterload. if hypotension develops the hypertrophied myocardium doesn’t receive sufficient blood to adequately perfuse the coronaries. So SVR must remain elevated
With AS is a heavy narcotic based anesthetic ok?
Yes, anesthetic agents causing myocardial depression ar, bp reduction and tachycardia are detrimental. small amounts of volatile anesthetics are ok.
what happens to the heart anatomically in HCOM
- abnormal thickening of myocardium
- as septum enlarges it extends into the LVOT (during systole there is further narrowing of the LVOT)
- rapid blood flow creates the venturi effect pulling the anterior mitral leaflet into the LVOT causing further narrowing
- abnormal SAM leads to the degree of obstruction which varies based upon cardiac loading conditions and contractility
The degree of obstruction in HCOM is ______ proportional to LV contractilitiy and ______ proportional to LV preload and afterload
directly proportional to contractility
inversely proportional to preload and afterload
Why is a sinus rhythm important in HCOM?
because of the hypertrophy and decreased compliance the diastolic filling is dysfunctional, atrial contraction and sinus rhythm is important to ensure adequate diastolic filling
In HCOM how should preload, HR, contractility, SVR and PVR be maintainted?
- preload: increased
- HR: decreased
- contractility: decreased
- SVR: increased
- PVR: maintained
are symptoms different with chronic aortic regurg and acute aortic regurg?
Yes.
- acute: sudden and severe dyspnea, CV collapse and rapid deterioration
- chronic: may be asymptomatic for years. SOB, palpitations, fatigue, angina
What is the immediate compensatory mechanism for acute aortic regurg?
increased contractility and HR.
Does LVEDP increase in chronic aortic regurg?
only much later when the disease has progressed
Which type of hypertrophy do you see in aortic regurg?
eccentric….as LV dilation increases coronary perfusion decreases leading to irreversible LV damage
Would you expect a narrow or wide pulse pressure with aortic regurg?
Wide pulse pressure since blood from the aorta is regurgitating back into the LV during diastole, the aortic diastolic pressure drops
What intervention is indicated for acute aortic regurgitation?
urgent surgery, inotropic support is usually needed to maintain CO
In the pt with aortic regurg how do you manage preload, HR, contractility, SVR and PVR
- LV preload: increase (maintenance of forward flow depends on preload augmentation)
- HR: increase (around 90 bpm)
- contractility: maintain
- SVR: decrease (maintain forward flow)
- PVR: maintain
IABP is contraindicated in which valvular lesion
Aortic regurg. Because augmentation of the diastolic pressure will increase the amount of regurgitant flow
If afib is developed in the setting of mitral stenosis what can it do to CO?
Can lead to significant impairment in CO since atrial contraction contributes about 30% of LV filling in mitral stenosis
In the pt with mitral stenosis how is LV preload, HR, contractility, SVR and PVR maintained?
- LV preload: increased (forward flow is dependent on adequate preload)
- HR: decrease
- contractility: maintain
- SVR: maintain
- PVR: decrease
In a pt with mitral regurg what would you expect the ejection fraction to be?
Elevated because it has technically 2 outlfow tracts.
After mitral valve repair however the pt is at risk if they had a previously low ejection fraction
How do you maintain LV preload, HR, contractility, SVR and PVR in the pt with mitral regurg?
- LV preload: increase or decrease (usually increasing is best but in some pts dilation of the LA and LV dilates the mitral valve annulus)
- HR: increase/maintain
- contractility: maintain (for forward flow)
- SVR: decrease
- PVR: decrease
In tricuspid stenosis how to you manage RV preload, HR, SVR, PVR, and contractility?
- RV preload: increase
- HR; maintain or increase
- contractility: maintain
- SVR: increase (systemic vasodilation may lead to hypotension in pts with limited flow across the valve)
- PVR: maintain
to selectively reduce PVR which drugs could be used?
- nitric oxide
- dobutamine, milrinone and isoproterenol may decrease PVR and also provide inotropic support
Adaptive rate sensing can have what disadvantages?
Can lead to inappropriate high rate pacing if they sense mechanical or physiologic interference. It should be disabled in periop settings
Typically what will magnet application do to the pacemaker modes?
Usually will switch to an asynchronous pacing mode. Adaptive rate response will shut off
are EMI signals btw 5-100Hz filtered? Why or why not?
No. Because thees overlap the frequency range of intracardiac signals.
What things can increase defibrillation thresholds?
Acute MI
Severe acid-base imbalances
Sever electrolyte imbalances
Hypoxia
How to ICDs typically respond to magnet application?
- inhibits tachycardia sensing and delivery of shock ONLY
- doesn’t interfere with bradycardia pacing or turn to asynchronous pacing
Which types of pts are at higher risk for asystole in the presence of EMI
Pacer dependent pts
If there is a pacemaker-dependent pt and the location of surgery precludes the placement of a magnet how could the anesthetist go about managing the device during the procedure/
Consider programming the device to an asynchronous mode or limiting the EMI to short bursts while watching the response of the pacing. Adaptive rate pacing should be programmed off.
in a situation were an ICD has no device info should a magnet be placed over it
No, not unless EMI is unavoidable. If unavoidable, then the pt needs to be placed on a cardiac monitor and magnet will be put on and kept on during cautery or RF therapy
Phase 0 of action potentials
depolarization
-Na+ in
Phase 1 of action potentials
early repolarization
-little bit of K+ out
phase 2 of action potentials
plateau (recovery phase)
-Ca2+influx
Phase 3 of action potentials
repolarization
-lots of K+ efflux
Phase 4
resting membrane potential
What is the starting defibrillating dose for adults.
What is it for cardioversion.
200 J
20-50 J
Describe failure to pace
For one or both chambers, either no pacing artifacts will be present on ECG, or artifacts will be present on one chamber and not the other
Describe failure to capture
Pacing spikes will appear atria or ventricles will not respond
Describe failure to sense
Will see pacer spikes in the middle of normal p or qrs waves
What monitors can be used to ensure that heart beats are perfusing even during the use of EMI?
arterial line or plethysmography
Is nitroprusside a potent arterial or venodilator?
arterial dilator.
-important to prevent further propagation or aortic dissection as well as the use of a beta blocker to decrease LV ejection fraction
Does CSF drainage help to reduce incidence of post-operative paraplegia and paraparesis in pts undergoing descending thoracic surgery?
Yes
What is the difference btw aortic dissection and aneurysm?
dissection: when blood penetrates the aortic intima, forming an expanding hematoma within the aortic wall or a false channel for flow btw medial layers
aneurysm: dilation of all 3 layers of aortic wall
Differentiate btw type A dissections and type B.
Type A: any involvement of the ascending aorta (these are more emergent and have a virulent course)
Type B: sections that involve the aorta distal to the subclavian artery
Many pts with aortic disease will have evidence of what on the ECG
LVH d/t high incidence of hypertension
Which is more important in the pt with suspected aortic dissection
The first priority is always to control the BP and ventricular ejection velocity as these propagate aortic dissection. Making a definitive diagnosis with radiographic studies should occur after proper management occurs
compare nitroglycerin and nitroprusside
Nitroprusside relaxes both arterial and venous smooth muscle. Nitroglycerinis a less potent vasodilatior than nitroprusside, and it causes more VENOUS than arterial dilation
Ischemic bowel secondary to cross clamping can lead to what pH imbalance
metabolic acidosis
If both the right and left head/neck arteries are involved in the aortic dissection where should the a-line be placed?
Femoral artery
Where can the artery of Adamciewicz arise from
Anywhere from T5 to below L1
Describe anterior spinal syndrome
Motor function is usually completely lost (anterior horns) but some sensation may still be intact (posterior columns)
Which surgery puts the RLN at risk and possibly causing left vocal cord paralysis
descending thoracic aortic surgery
Where is usually the best place to monitor arterial bp
right radial or brachial. Left subclavian may be occluded d/t to the cross clamp
Before the aorta is cross clamped which med can be administered to try and provide some renal protection during clamping
mannitol
After the cross clamp is placed what is common distal to the clamp.
metabolic acidosis secondary to hypoperfusion to organ beds. acidosis should be Rx aggressively with bicarb
What is the time limit for aortic cross clamping?
30 mins
Before the surgeon removes the cross clamp what should be done to prevent hypotension
Volume resuscitation and vasopressors
Declamping shock
severe hypotension and myocardial depression
To attenuate the effects of clamp removal when should volume be optimized intraop?
10-15 mins before unclamping
What will SEPs tell you about the perfusion to artery of adamciewicz and what will MEPs tell you
SEPs tell you posterior column integrity
MEPs tell you anterior horn - MEPs are the superior method of monitors for spinal cord ischemia because they indicate anterior horn integrity. the anterior portion is also more at risk during clamping
Formula for spinal cord perfusion pressure
SCPP = MAP-CVP or CSFP(ICP)
- maintain CSFP btw 10-15 mmHg
