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When is arterial cannulation indicated?
Patient with significant hemodynamic instability
Patient who will require frequent arterial blood draws
Patients with severe hypotension (shock)
Unstable respiratory failure
What does the dicrotic notch represent on an arterial pressure waveform?
Closure of the aortic valve
When vasodilators such as sodium nitroprusside are administered, it is important to monitor the fall in blood pressure because low blood pressure can?
Vasodilators may reduce diastolic pressure more rapidly than systolic or mean pressure
Which may result in compromised coronary perfusion
The pulse pressure is important hemodynamically because it is an indication of?
Is a reflection of stroke volume (SV) by the left ventricle and arterial system compliance.
A pulse pressure <30 mm Hg indicates low SV by the left ventricle. If pulse pressure increases with fluid therapy, the patient was probably hypovolemic)
What are complications of direct arterial monitoring?
Ischemia resulting from embolism, thrombus, or arterial spasm
The central venous pressure represents?
Represents the end-diastolic pressure in the right ventricle (RVEDP)
[during distole when the tricuspid valve is open between RA & RV]
CVP is the pressure of blood in the RA or Vena Cava
Reflects preload (filling volume) for the RV
Monitoring of central venous pressure is indicated when there is a need to assess?
To assess the ciculating blood volume (adequacy of cardiac filling)
The degree of venous return
To evaluate right ventricular function
The "a" wave would be absent in what dysrhythmia?
Atrial Fibrillation (when there is no atrial contraction)
An exaggerated "v" wave would be found in condition?
When an AV valve does not close all the way (incompetent or leaky valve), some of the blood is ejected backward into the atrium during systole (tricuspid regurgitation), creating exaggerated V waves and an elevated CVP measurement.
What change is seen on the central venous pressure waveform when the patient takes a spontaneous deep breath?
The waveform should fall below baseline as intrathoracic pressure falls with inspiration
When a pressure manometer is used to measure central venous pressure, the reading usually is taken at?
With the patient in the supine position, the zero level of the manometer is placed at the pt's right atrial level.
CVP is ideally read at the end of expiration
What causes an increase, and a decrease in central venous pressure?
Increase Venous return (volume)
decrease ability of the right heart to move blood
decrease intrathoracic pressure
increased ability for heart to move blood forward
Central venous pressure can be used to estimate left ventricular filling pressures if there is?
In patients with EF > than 0.50 (50% of LVEDV) and
No cardiopulmonary disease
Central venous pressure is most likely to correlate well with left ventricular filling pressure in what type of patient
In young patients with no history of heart disease or hypertension
What complications are involved in the use of central venous pressure catheters?
Subclavian artery accidentally penetrated
Development of thrombus around the catheter
The pulmonary artery catheter allows assessment of?
Allows assessment of the filling pressures of the left side of the heart
The purpose of the balloon at the tip of the pulmonary artery catheter insitu is to?
To float the catheter into position
To obtain wedge pressure measurements
When the pulmonary artery catheter is inserted, the balloon is inflated in the right atrium before it is inserted further. Why is this done?
This encourages the catheter to follow blood flow into the right and then into the PA and,
Decreases the risk of PVCs occurring while the catheter is in the ventricle
If, when the pulmonary artery catheter is inserted, there is a rapid increase in the height of the pressure waveforms with the downstroke dropping near zero, the respiratory therapist should do what?
The balloon is deflated, and the catheter is withdrawn until the tip is in the atrium. The balloon is then reinflated and the catheter is reinserted.
With a properly inserted and positioned pulmonary artery catheter, a systolic pressure reading in the pulmonary artery of 50 mm Hg could be due to?
PA pressures increase when pulmonary blood flow increases or when PVR increases.
increased blood flow: volume overload, left-to right intracardiac shunts (atrial/septal defects, PDA)
increased PVR: caused by constriction, obstruction, or compression of the pulmonary vasculature or by backpressure from the left heart
An increase in pulmonary artery systolic pressure could be seen in what type of patient?
Acute or chronic lung disease that causes pulmonary vasoconstriction in response to hypoxia
Cardiac tamponade or increased intrathoracic pressure compressing the vasculature and impeding forward flow
Left heart failure and mitral valve regurgitation causing backpressure from the left heart into the lungs
A difference between the pulmonary artery diastolic pressure and the pulmonary capillary wedge pressure greater than 5 mm Hg is seen in what conditions?
ARDS, Sepsis, Excessive PEEP, or other conditions that increase PVR
Normal pulmonary capillary wedge pressure is ______ mm Hg. In left ventricular failure, the pulmonary capillary wedge pressure is expected to?
For the pulmonary capillary wedge pressure to reflect pulmonary venous and left atrial pressures, blood flow must be uninterrupted between the catheter tip and the left heart. This condition exists only in which West's zone? Which zone is dominant in the supine position? What conditions could cause a shift to zone I or II?
Zone III (uninterrupted blood flow)
Zone II conditions dominate in supine patients
When intravascular volume decreases (diuresis, hypovolemia, hemorrhage) or alveolar pressure increases (PEEP), zone III areas can convert to zone I or II.
What could cause large fluctuations in the net distending pressure within the left ventricle (transmural pressure)?
Positive pressure ventilation
Labored respiratory effort
PEEP levels lower than what value has a limited effect on intrapleural pressure?
Less than 10 cm H2O
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