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Questions and Answers
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?
Which is true regarding performance of skin prep before 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?
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What is the main indication for arterial monitoring?
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Which complication is associated with arterial line placement?
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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?
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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?
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When does the 'c' wave in the CVP waveform typically occur?
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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?
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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?
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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?
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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?
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What is the purpose of Peres Formula modifiers?
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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?
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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.
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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.
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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.
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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?
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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?
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What characterizes an overdamped waveform in arterial monitoring?
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Which factor can contribute to underdamping in arterial monitoring?
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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?
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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?
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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?
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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?
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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?
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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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