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What is an advantage of continuous ST-segment monitoring compared to serial 12-lead ECG recordings?
What can cause baseline ST-segment abnormalities and reduce the specificity of standard ECG criteria for diagnosing myocardial ischemia?
What can be used to distinguish positional ST-segment changes from true ST-segment deviations?
What do most cardiac monitors with ST-segment monitoring software provide?
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Why may changes in body position cause false ST-segment alarms?
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What is a potential limitation of using standard ECG criteria for diagnosing myocardial ischemia in patients with preexisting ECG abnormalities?
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What is the primary advantage of using an anterolateral precordial lead (V3, V4, or V5) in ECG monitoring?
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What is the most commonly observed form of perioperative ischemia?
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What type of ischemia is indicative of the myocardial territory and coronary artery involved?
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What is the common technique used by automated noninvasive arterial blood pressure measuring devices?
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In which patients should caution be exercised when using automated noninvasive arterial blood pressure measuring devices?
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What is the primary importance of ECG monitoring in noncardiac surgery?
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What is the reported sensitivity of simultaneously examining leads II, V4, and V5 for ischemia detection?
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Which of the following ECG leads was found to be the most sensitive for detecting perioperative ischemia?
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What is the minimum ST-segment change required for detection of ischemia in a single lead?
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What is the minimum duration required for ST-segment changes to be considered significant?
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In which type of surgery is ECG monitoring particularly important for detecting ischemia?
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What is the term for the abnormal elevation of the ST segment on an ECG, as seen in ischemia?
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What is the term for the type of ischemia that occurs in the deeper layers of the heart muscle?
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What is the benefit of using waveform analysis in physiological monitoring?
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What is the primary advantage of using ultrasound guidance in radial artery cannulation?
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What is used to indicate preload reserve and volume responsiveness in cardiac monitoring?
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What is the primary limitation of using radial artery cannulation?
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What is the benefit of using ultrasound guidance in catheterization of other vessels beyond the radial artery?
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What is used to trigger intra-aortic balloon counterpulsation?
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What is the benefit of using radial artery cannulation in cardiac monitoring?
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What is a limitation of thermodilution cardiac output monitoring?
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What is mixed venous hemoglobin oxygen saturation a measure of?
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What percentage of information used in monitoring a patient's cardiovascular status comes from electronic devices?
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What type of monitoring is improved when considering both in monitoring and clinical evaluation?
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What can affect the accuracy of mixed venous hemoglobin oxygen saturation measurement?
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What is a common technique used in cardiovascular monitoring?
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What is a limitation of using pulmonary artery wedge pressure to estimate left atrial pressure?
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What is a reason why pulmonary artery catheter monitoring has not been shown to improve patient outcomes?
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What is a confounding factor that affects the use of central venous pressure as an estimate of left ventricular preload?
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What is a limitation of using central venous, pulmonary artery diastolic, or pulmonary artery wedge pressures as estimates of left ventricular preload?
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Why is pulmonary artery wedge pressure not a reliable measure of left atrial pressure in all cases?
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What is a potential problem with hemodynamic therapies guided by specific hemodynamic indices?
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What is a disadvantage of using central venous catheters?
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Why has pulmonary artery catheter monitoring not been shown to improve patient outcomes?
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Study Notes
Cardiovascular Monitoring
- Electrocardiogram (ECG) monitoring provides continuous monitoring of heart rate, identification of arrhythmias and conduction abnormalities, and detection of myocardial ischemia.
ECG Monitoring Considerations
- Accurate and reliable ECG monitoring requires attention to lead placement and selection, choice of filter, and gain that will influence the displayed ECG tracing.
- An anterolateral precordial lead (V3, V4, or V5) should be selected for the most sensitive detection of myocardial ischemia.
ST-Segment Changes
- Demand-mediated subendocardial ischemia resulting in ST-segment depression is the most commonly observed form of perioperative ischemia.
- ST-segment depression is most commonly observed in an anterolateral precordial lead regardless of the coronary territory responsible.
- Supply-mediated transmural ischemia resulting in ST-segment elevation is uncommonly observed intraoperatively except during cardiac operations.
- ST-segment elevation is indicative of the myocardial territory and coronary artery involved.
Arterial Blood Pressure Measurement
- Most automated noninvasive arterial blood pressure measuring devices use an oscillometric measurement technique and rarely cause complications.
- Caution should be exercised in patients who cannot complain of arm pain, those with irregular rhythms that force repeated cuff inflation, and those receiving anticoagulant therapy.
ST-Segment Monitoring Advantages
- One major advantage of continuous ST-segment monitoring is that the electrodes stay in place and do not vary as they may with serial 12-lead ECG recordings.
Limitations of ST-Segment Monitoring
- Many patients have preexisting ECG abnormalities that confound interpretation of ST-segment changes.
- Changes in body position may cause ST-segment changes and lead to false ST-segment alarms.
- Early repolarization, intraventricular conduction delays, LV hypertrophy, digitalis, pericarditis, and other conditions may cause baseline ST-segment abnormalities.
Cardiac Monitor Software
- Most cardiac monitors with ST-segment monitoring software provide displays of ST-segment trends in a single lead or the sum of absolute ST-segment deviations from multiple leads.
- Monitoring continuous 12-lead ST-segment changes greater than 0.2 mV from baseline in a single lead or more than 0.1 mV in two contiguous leads at J+60 ms, lasting longer than 10 minutes, can detect perioperative ischemia.
- Leads V3 and V4 are more sensitive than V5 in detecting perioperative ischemia.
Central Venous and Pulmonary Artery Catheters
- Catheter misuse and data misinterpretation are common complications of central venous and pulmonary artery catheters
- Pulmonary artery wedge pressure is a delayed and damped reflection of left atrial pressure and may underestimate capillary pressure in patients with sepsis
Limitations of Catheter-Derived Data
- Use of central venous, pulmonary artery diastolic, or pulmonary artery wedge pressures as estimates of left ventricular preload is subject to many confounding factors
- Pulmonary artery catheter monitoring has not been shown to improve patient outcomes due to misinterpretation of catheter-derived data and failure of hemodynamic therapies
Cardiac Output Monitoring
- Thermodilution cardiac output monitoring is subject to measurement errors introduced by rapid intravenous fluid administration, intracardiac shunts, and tricuspid valve regurgitation
- Mixed venous hemoglobin oxygen saturation is a measure of the adequacy of cardiac output relative to body oxygen requirements
Hemodynamic Monitoring
- Electronic devices provide the majority of information used in monitoring a patient's cardiovascular status
- Waveform analysis in physiologic monitoring has become more popular and can be used to indicate preload reserve and volume responsiveness
- Arterial pressure waveform characteristics include the dicrotic notch and respiratory-induced variation in pressure measurements
Arterial Blood Pressure Monitoring
- Techniques for radial artery cannulation have been unchanged for decades, but the use of ultrasound in guiding catheter placement has improved first-pass cannulation success rates
- Ultrasound guidance in catheterization of other vessels or in special populations may be of substantial benefit
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Description
This quiz covers the key points of cardiovascular monitoring, including ECG monitoring, lead placement, and identification of arrhythmias and conduction abnormalities.
