Podcast
Questions and Answers
What is the first step after inserting the introducer needle during a CVC procedure?
What is the first step after inserting the introducer needle during a CVC procedure?
Where is the internal jugular vein typically located in relation to the carotid artery?
Where is the internal jugular vein typically located in relation to the carotid artery?
Which is true regarding performance of skin prep before a CVC procedure?
Which is true regarding performance of skin prep before a CVC procedure?
At what angle should the needle be inserted during a CVC procedure?
At what angle should the needle be inserted during a CVC procedure?
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Which step confirms proper catheter placement during a CVC procedure?
Which step confirms proper catheter placement during a CVC procedure?
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What is the main indication for arterial monitoring?
What is the main indication for arterial monitoring?
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Which complication is associated with arterial line placement?
Which complication is associated with arterial line placement?
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What is the purpose of Allen's test?
What is the purpose of Allen's test?
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When performing the Modified Allen’s Test, what does a negative result indicate?
When performing the Modified Allen’s Test, what does a negative result indicate?
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What does the 'a' wave in the CVP waveform represent?
What does the 'a' wave in the CVP waveform represent?
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Which condition might lead to deliberately induced hypo- or hypertensive technique for arterial monitoring?
Which condition might lead to deliberately induced hypo- or hypertensive technique for arterial monitoring?
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When does the 'c' wave in the CVP waveform typically occur?
When does the 'c' wave in the CVP waveform typically occur?
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What characterizes the 'x' descent in the CVP waveform?
What characterizes the 'x' descent in the CVP waveform?
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What is the normal/positive time frame for recirculation in Allen's test?
What is the normal/positive time frame for recirculation in Allen's test?
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Which event leads to the 'y' descent in the CVP waveform?
Which event leads to the 'y' descent in the CVP waveform?
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What does a normal CVP value indicate in a spontaneously breathing patient?
What does a normal CVP value indicate in a spontaneously breathing patient?
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Which complication is NOT associated with CVP line insertion?
Which complication is NOT associated with CVP line insertion?
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What is the best way to estimate centra venous catheter length according to the text?
What is the best way to estimate centra venous catheter length according to the text?
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What complications can arise if a central line catheter is too short, based on the text?
What complications can arise if a central line catheter is too short, based on the text?
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Which statement about the subclavian vein is true according to the text?
Which statement about the subclavian vein is true according to the text?
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What is the purpose of Peres Formula modifiers?
What is the purpose of Peres Formula modifiers?
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Why should the subclavian approach be avoided in patients with coagulation disorders?
Why should the subclavian approach be avoided in patients with coagulation disorders?
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What potential issue can occur in patients with devices in the subclavian vein according to the text?
What potential issue can occur in patients with devices in the subclavian vein according to the text?
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The 'a' wave in the CVP waveform reflects atrial contraction and tricuspid valve closure.
The 'a' wave in the CVP waveform reflects atrial contraction and tricuspid valve closure.
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The 'c' wave in the CVP waveform occurs during late diastole.
The 'c' wave in the CVP waveform occurs during late diastole.
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The 'v' wave in the CVP waveform reflects a decrease in atrial pressure due to passive filling during early diastole.
The 'v' wave in the CVP waveform reflects a decrease in atrial pressure due to passive filling during early diastole.
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A normal value for CVP in a spontaneously breathing patient is around 10-15 mmHg.
A normal value for CVP in a spontaneously breathing patient is around 10-15 mmHg.
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CVP is a reliable indicator of patient fluid status and can be used alone to determine the need for fluid therapy.
CVP is a reliable indicator of patient fluid status and can be used alone to determine the need for fluid therapy.
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What does the 'v' wave in the CVP waveform represent?
What does the 'v' wave in the CVP waveform represent?
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During which cardiac phase does the 'x' descent occur in the CVP waveform?
During which cardiac phase does the 'x' descent occur in the CVP waveform?
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What is the primary event leading to the 'y' descent in the CVP waveform?
What is the primary event leading to the 'y' descent in the CVP waveform?
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What is the key role of the 'c' wave in the CVP waveform?
What is the key role of the 'c' wave in the CVP waveform?
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What characterizes an overdamped waveform in arterial monitoring?
What characterizes an overdamped waveform in arterial monitoring?
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Which factor can contribute to underdamping in arterial monitoring?
Which factor can contribute to underdamping in arterial monitoring?
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What is the purpose of the Square Test in arterial monitoring?
What is the purpose of the Square Test in arterial monitoring?
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What can lead to overestimation of Diastolic Blood Pressure (DBP) in arterial monitoring?
What can lead to overestimation of Diastolic Blood Pressure (DBP) in arterial monitoring?
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What should be done after inserting the guidewire during a CVC procedure?
What should be done after inserting the guidewire during a CVC procedure?
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How should the skin incision be made during a CVC procedure?
How should the skin incision be made during a CVC procedure?
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What is the correct way to insert the dilator during a CVC procedure?
What is the correct way to insert the dilator during a CVC procedure?
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How can correct placement of the angiocath in a vein be assessed?
How can correct placement of the angiocath in a vein be assessed?
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What action should be taken if the angiocath is incorrectly placed in a vein during CVC insertion?
What action should be taken if the angiocath is incorrectly placed in a vein during CVC insertion?
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What should not be done when using the Raulerson syringe for guidewire insertion?
What should not be done when using the Raulerson syringe for guidewire insertion?
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What is important to consider when selecting the proper cuff size for noninvasive blood pressure measurements?
What is important to consider when selecting the proper cuff size for noninvasive blood pressure measurements?
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Why is it essential to avoid delays in measuring noninvasive blood pressure for more than 2 minutes?
Why is it essential to avoid delays in measuring noninvasive blood pressure for more than 2 minutes?
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Study Notes
Arterial Monitoring
- Indications for arterial monitoring:
- Frequent blood sampling (ABGs)
- Continuous real-time monitoring when rapid changes are anticipated
- Major fluid shifts or probable blood loss
- History of CV disease processes (valvular disease, CAD, stroke, poor EF, etc.)
- Pharmacologic manipulation
- Mechanical manipulation (cardiovascular surgery)
- Failure of indirect BP monitoring (morbid obesity, burned extremity, etc.)
- IABP counterpulsation or LVAD
- Deliberately induced hypo- or hyper-tensive technique
- Major cardiac, vascular, trauma, or neuro surgery
- Long-term administration of vasoactive drug infusions (post-op)
- Supplementary diagnostic information desired
- Complications of arterial monitoring:
- Hematoma (femoral: retroperitoneal)
- Thrombosis/embolization
- Limb ischemia
- Idiopathic blood loss
- Arteriovenous fistula
- Infection
- Nerve damage
- Vasospasm
- Skin necrosis local to catheter site
Allen's Test
- Perform modified Allen's test:
- Occlude radial and ulnar arteries
- Bend patient's elbow to lift hand for exsanguination
- Release ulnar artery to observe recirculation time
- Repeat to compare to radial artery recirculation time
- Normal/positive Allen's test = < 10 seconds
- Negative Allen's test = puncture contraindicated
- Refill timing should be similar between the two tests
CVC Procedure Steps
- Initial scan: place US transducer to identify structures in short axis to complete a pre-procedure risk assessment
- Prep/drape patient and equipment
- Identify insertion point at the apex of Sedillot's Triangle
- Insert needle (bevel up) at 30-45° towards ipsilateral nipple/iliac crest
- Maintain continuous needle aspiration
- Advance central line catheter
- Remove guidewire
- Aspirate, flush, and cap each lumen
- Clean and secure catheter
- Confirm placement via x-ray
Catheter Length Estimation
- Use Peres formula: Height ÷ 10 + [insertion site modifier]
- Insertion site modifiers:
- -1 cm for right SC
- -2 cm for right IJ
- +4 cm for left SC
- +2 cm for left IJ
- Average catheter length to the caval-atrial junction:
- 16 cm for right SC
- 16 cm for right IJ
- 19 cm for left SC
- 21 cm for left IJ
- 40 cm for femoral
CVP Waveform
- Normal CVP waveform consists of three positive peaks (a, c, v) and two negative descents (x, y) in the RA waveform
- a wave: reflects atrial contraction
- c wave: reflects closure of the tricuspid valve
- v wave: reflects atrial pressure increase due to filling of the atrium
- x descent: reflects systolic collapse in atrial pressure
- y descent: reflects diastolic collapse due to passive filling
- CVP waveform abnormalities:
- Atrial fibrillation
- Tricuspid stenosis, RV hypertrophy
- Tricuspid regurgitation
- CVP is approximate to right atrial pressures, which can be used to estimate right ventricular preload
- Normal value in a spontaneously breathing patient: 5-10 mmHg
- Rises ~3-5 mmHg during mechanical ventilation
Complications
- Insertion-related complications:
- Arterial puncture
- Air or thrombus embolism
- Arrhythmias
- Hematoma
- Pneumothorax/hemothorax/hydrothorax/chylothorax
- Thoracic duct injury
- Cardiac perforation or cardiac tamponade
- Nerve injury
- Insertion complication rates increased by:
- Practitioner proficiency
- Number of needle passes
- BMI >30 or PV>PA
Noninvasive Blood Pressure
-
Sphygmomanometry:
- Auscultation of Korotkoff sounds created via turbulent flow due to partial collapse of the constricted artery
- Allows for measurement of systolic and diastolic pressures
-
Oscillometry:
- Automated NIBP measures pressure fluctuations due to pulsations transmitted to solid-state transducers
- Microprocessors then interpret these pressure changes
- MAP measured at the greatest amplitude of oscillations
- SBP recorded upon first appearance of blood flow
- DBP is calculated or measured at last detectable oscillation (least reliable)
-
NIBP limitations:
- Deviation of ±10 mmHg compared to intraarterial measurements
- Limitations:
- Proper cuff sizing
- Calibrated for brachial artery only
- Limbs with central access (PICC), fractures, or AV fistula
- Obese patients
- Severe arterial stenosis
- Arrhythmias
- MAP < 65 mmHg
- Sudden hyper- or hypotension
- Delays in measurement timing (> 2 min)
- Surgeon positioning
- Complications:
- Pain
- Neuropathy
- Petechiae and ecchymoses
- Venous stasis à edema à compartment syndrome
- Peripheral ischemia
- Distal IV interference### Damping
-
Damping prevents a system from overresponding to a change
-
Overdamping: too HIGH of resistance, waveform appears with slurred upstroke, absent dicrotic notch, and loss of fine detail
- Causes: blood clots, air bubbles, kinks in the system, extensions (stopcocks/tubing), malpositioned catheters
-
Underdamping: too LOW of resistance, waveform appears with exaggerated peaks and troughs
- Causes: excessively rigid/short/narrow tubing, tachycardia
Square Test
- Assesses frequency and damping characteristics of the transducing system
- Rapid introduction of a high-pressure pulse into the transducing system creates a waveform that reverberates at a frequency and diminishes over time in accordance with resistance
- Overdamped: minimal to no oscillations
- Underdamped: excessive oscillations
Calibration
- Zeroing: transducer should be zeroed by opening the transducer to atmosphere at its three-way stopcock
- Establishes the zero pressure reference value against which all intravascular pressures are measured
Seldinger Technique
- Advance guidewire: insert J-wire through the opening in the distal part of the plunger
- Do not force guidewire at any time and do not advance past 15cm
- Monitor for arrhythmias and maintain control of J-wire at all times
Pressure Manometry Analysis
- Equipment: manometer/extension tubing & angiocath
- Steps:
- Remove the introducer needle
- Thread the conventional angiocath over the guidewire
- Remove the guidewire
- Attach an extension tubing to the angiocath
- Allow tubing to hang so that it fills 2/3 full with blood
- Hold the tubing straight up
- Assess if the angiocath is in a vein: the column of blood will equilibrate about 3-10cm above the right atrium
- Changes with respiration expected but should not be pulsatile
- Blood coloration is a poor indicator of correct placement
- If the angiocath is in an artery: the column of blood will continue to rise
CVC Procedure Steps
- Create a skin incision: slide blunt end of scalpel along the guidewire and make a longitudinal incision ~0.5cm in depth
- Insert dilator: use a circular, twisting motion, to progressively slide the dilator into the skin
- Never hub the dilator
- Remove the dilator and maintain control of the guidewire
CVP Waveform
- Normal CVP waveform consists of three positive peaks (a,c,v) and two negative descents (x,y) in the RA waveform
- a wave: atrial contraction
- c wave: tricuspid closure and ventricular contraction
- v wave: venous filling of atrium
- x descent: atrial relaxation and ventricular contraction
- y descent: emptying of atrium
CVP Waveform Abnormalities
- Atrial fibrillation: tricuspid stenosis, RV hypertrophy
- Tricuspid regurgitation
CVP
- CVP is approximate to right atrial pressures which can be used to estimate right ventricular preload
- Suggestive of blood volume and right-sided cardiac function
- Normal value in a spontaneously breathing pt: 5-10 mmHg
- Rises ~3-5mmHg during mechanical ventilation
- Dependent on functional ventricles, lack of valvular disease, physiologic vasculature
- Poor correlation to patient fluid status
- Fluid therapy should ideally involve monitoring trends and including other measurements
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