Monitoring - Quiz 2 Flashcards
What causes the most pressure monitoring errors?
air within a catheter or transducer
What is the recommended mode of monitoring temp on a cardiac surgical pt? (CSP)
One core site (nasal) AND
One shell site (bladder or rectal)
True or False. Although low serum Ca may affect myocardial pumping fx, admin of Ca during potential neural ischemia or repercussion may likely worsen the outcome and should be avoided.
True
Which EKG leads are most useful for monitoring the inferior wall of the heart?
II, III, aVF
Which EKG leads are most useful for monitoring the lateral wall of the heart?
I, aVL
Where is the precocial unipolar lead placed to best monitor the LV?
V5 position along the anterior axillary line in the 5th intercostal space
The best single lead in diagnosing myocardial ischemia in a pt w CAD
V5
> 90% of ischemic episodes will be detected by EKG is which 2 leads are analyzed simultaneously?
leads II and V5
How can one monitor for posterior wall ischemia?
7- lead system or esophageal lead
most useful leads in the post-op dx of complex conduction problems and dysrhythmias
AV pacing wires (epicardial electrodes)
None of the standard EKG leads can detect ischemia in which 2 locations?
posterior wall
RV
How well do noninvasive monitoring devices function when pulsatile blood flow is absent (during CPB or LVAD use)
They don’t.
True or false: Correct damping of a pressure-monitoring system should not affect the natural frequency of the system
true
A system that overestimates SBP and underestimates DPB would be ____damped
Underdamped
A system that underestimates SBP and overestimates DBP would be ____damped
Overdamped
An optimally or critically damped system will exhibit a ________ frequency response in the range or frequencies up to the natural frequency of the system
constant/flat
critical part of a transducer that acts to link fluid wave to electrical input
diaphragm
True or False: most transducer systems used in clinical anesthesia can be described as underdamped systems with low natural frequency
true
Systolic pressure measured in a radial A line may be up to ___ - ___ mmHg higher than aortic pressure. WHY?
20-50 mmHg
because of decreased peripheral arterial elastance and wave summation
What is the most common site used for arterial cannulation? Why?
Radial artery
- it is convenient
- it provides a reasonably accurate estimation of the true aortic pressure
What indicates limited collateral ulnar artery flow into the hand?
positive Allen’s test
even w a positive Allen’s test, radial artery cannulation still has had very few ischemic complications
True or False: The distal location of DP and PT arterial line sites leads to increased distortion of the arterial wave.
True.
Factors that may cause a narrow pulse pressure on an A-line
pericardial tamponade
hypovolemia
factors that may cause an increased pulse pressure on an A-line
worsening aortic valvular insufficiency
hypovolemia
A decreased SBP with PPV suggests….
Hypovolemia
Positive intrathoracic pressure impedes venous return to the heart w a more pronounced effect in a hypovolemic pt
Rate of pressure rise during systole can reflect…
contractility
HR, preload, and after load can affect it tho
area under the aortic pressure wave from the onset of systole to the dicrotic notch can reflect….
Stroke volume
Position of the dicrotic notch on the A-line wave form correlates w….
SVR
high notch = high SVR; low notch = low SVR
What has more risk of thrombus development, A-lines or central venous catheters? Why?
A-lines because they are not heparin bonded
Why is radial artery pressure significantly lower than aortic pressure at completion of CPB?
- forearm vasodilation secondary to rewarming may lead to A-V shunting, resulting in steal phenomenon 5-30 min longer in duration
OR - hypovolemia and vasoconstriction
most common IV access route in cardiac anesthesia
internal jugular vein
Relative contraindications for IJ central line placement
- presence of carotid dz
- recurrent cannulation of IJV (thrombus risk)
- contralateral diaphragmatic dysfunction
- Thyromegaly or prior neck surgery
What site is recommended as the first option for PAC placement?
L subclavian
A “Cannon A wave” on a CVP indicates ________
AV dissociation
RA is contracting against a closed tricuspid valve
Abnormal V wave on CVP indicates _______
tricuspid valve insufficiency
retrograde flow through the incompetent valve –> increased RA pressure during systole
PA pressure reflects….
- RV fx
- PVR
- LA filling pressure
PCWP is a more direct estimate of
LA filling pressure
a valveless hydrostatic column exists b/t the distal port and the LA at end-diastole
2 indications that cannot be performed w CVP alone
- differentiation of L vs R ventricular fx
2. assessment of intracardiac filling pressures during cardioplegia administration
Increase in CVP
Decrease in CVP to mean PA gradient
Low CO
…all indicate _______
RV failure
hallmarks of LV failure
simultaneous readings of high PA pressures and PCWP in the presence of systemic HoTN and low CO
if the PA diastolic and wedge pressures do not agree closely with one another, what would you suspect is occurring?
Pulm HTN
Primary diagnostic modality for tricuspid and pulm valve stenosis in adults
TEE
increase in PA pressure or increase in PCWP reflects a decrease in ventricular compliance. What would this be associated with?
Significant ischemia
The established convention is to evaluate PA pressures during which part of the breathing cycle?
end expiration
4 mechanisms that may result in decreased SvO2
- decreased CO
- Decreased hgb concentration
- decreased arterial O2 sat
- increased O2 utilization
True or False: Changes in SvO2 usually precede hemodynamic changes by a significant period of time.
True
most common complication associated w PAC insertion
dysrhythmias
Which approach offers the most direct route to the RA and thus results in the highest rate of successful PA catheterization?
Which approach is next most effective?
R IJ
L subclavian
most common arrhythmia during PAC placement
PVCs
usually resolved with either catheter withdrawal or with advancement of the catheter tip from the RV into the PA
The PAC should not be advanced more than _______ from the RIJ approach because this increases the risk for PA rupture or catheter knotting
60 cm
Although thrombus formation of PACs has been noted at 24h, the incense of thrombogenicity substantially increases by ________
72 hrs
How is a CO measurement altered with R sided valvular lesions when using the thermodilution method?
How is it altered with mitral or aortic valve lesions?
CO is underestimated w RV valvular lesions
CO remains accurate for forward LV CO for LV valvular lesions
5 factors that may alter the CO reading from normal when using the thermodilution method
- Volume of injectate (less volume = falsely higher CO volume and vice versa)
- Temp of injectate (increase 1*C = 3% overestimation of CO
- Shunts
- Timing with resp cycle
- Catheter position (must be in PA but not wedged)
practical gold standard for evaluating CO
PAC
thermodilution method is most commonly utilized
True or False: Adequacy of perfusion is likely when a pulse oximeter shows a saturation reading.
True
because the pulse ox utilizes plethysmography as part of its basic operation
3 factors for which EtCO2 offers evidence
- endotracheal intub
- ventilation
- perfusion
What does core temperature represent?
The temp of the vital organs
How does hypercarbia affect PA pressures and RV fx?
increases PA pressures
worsens RV fx
Why should an esophageal temp probe not be routinely used for cases involving CPB?
the esophagus will be greatly affected by the temp of the blood returning from the extracorporeal pump
Shell temperature represents
the temp of the majority of the body (musc, fat, bone) which receives a smaller portion of the blood flow
single most important monitor of renal rx during surgical cases involving CPB
Urinary catheter
Which 2 electrolytes typically decline during CPB?
K and Mg
What is the basic principle of clinical EEG monitoring?
cerebral ischemia causes slowing of the electrical activity of the brain, as well as a decrease in signal amplitude
True or False: Microshock cannot occur unless the skin resistance has been bypassed.
True
Most common means of monitoring adequate heparin effect
ACT (activated clotting time)
What ACT level is adequate during CPB?
> 400s
(if off pump CABG cases using partial heparinization, ACT target is ~300s
How often should blood glucose be measured during cardiac surgery, and at what level should an insulin gtt be started?
q 30-60 min
200 mg/dL
