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Ensuring Accurate Arterial Line Readings

Arterial catheters are used for the direct monitoring and measurement of systolic, diastolic, and mean arterial pressures. Direct measurement accounts for systemic vascular resistance and blood flow resulting in highly accurate data. Whereas methods such as oscillometry, auscultatory, or doppler data are indirect and only measure blood flow.

Clinical Indications for Arterial Pressure Monitoring

Escalating Vasopressors

Maintaining close monitoring in patients requiring increasing vasopressor support.

Shock

Continuous monitoring in patients presenting with signs of shock to assess systemic perfusion.

Suspicion of Sepsis

Indicated for patients where sepsis is suspected, aiding in the assessment of perfusion.

Continuous Antihypertensive Infusion

Monitoring essential for patients receiving continuous antihypertensive infusion.

An arterial catheter may also be appropriate for patients exhibiting signs of high systemic vascular resistance, requiring reliable continuous blood pressure monitoring for precise management.

How to Prime an Arterial Line

Priming an arterial line is a critical step in ensuring accurate hemodynamic monitoring. It involves removing air from the tubing to prevent air embolisms and ensure proper pressure transduction.

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ARTERIAL MONITORING SYSTEM LEVELING METHOD

The following information is a summary from this article.

Understanding Transducer Leveling and Positioning

1

Phlebostatic Axis

The ideal reference point for transducer leveling is the phlebostatic axis, which corresponds to the fourth intercostal space at the midpoint of the sternum, approximating the aortic root level. This position ensures that the transducer is aligned with the patient's heart, providing the most accurate readings.

2

Importance of Proper Leveling

Accurate transducer leveling is crucial because it ensures that the pressure readings accurately reflect the patient's true blood pressure. Improper leveling can lead to significant discrepancies, particularly in diastolic pressure measurements, which are more sensitive to the transducer's position relative to the patient's heart.

Transducer Locations and Their Effects

Locations Explored

The study investigated the effects of several alternative transducer locations, including:

  • IV Pole
  • Taped to the upper arm
  • Rolled cloth adjacent to the upper arm
  • Wrist placement

Findings

The study found that diastolic blood pressure readings varied significantly with the leveling method, especially when using the IVP position with visual alignment. However, no significant differences were observed in systolic or mean arterial pressure readings across the different transducer locations when properly leveled.

Transducer Positioning Considerations

Aortic Root Alignment

Ensure the transducer is positioned at the level of the patient's aortic root to obtain the most accurate readings.

Precise Leveling

Visual reference to carefully level the transducer, ensuring a horizontal orientation with the aortic root.

Patient Mobility

Consider the taped-arm position when patients need to be transported within the hospital to maintain measurement accuracy.

Patient Position Changes

Monitor the transducer's alignment during patient position changes to avoid inaccurate readings, particularly for diastolic pressure.

Clinical Implications and Practical Application

1

Traveling with Patients

The taped-arm position may be preferable for patients moving within the hospital, as it eliminates the need for additional equipment and maintains measurement accuracy.

2

Patient Position Changes

Clinicians should ensure that the transducer remains in the proper horizontal alignment with the aortic root, especially when turning patients, to avoid inaccurate readings.

3

Importance of Proper Leveling

Careful attention to transducer leveling, regardless of the location, is crucial to ensure the reliability and accuracy of arterial line readings, particularly for diastolic pressure measurements.

4

Individualized Approach

The optimal transducer location and leveling method may vary based on the patient's specific needs and clinical situation, requiring clinicians to evaluate and adapt their approach accordingly.

Normal Arterial Waveform

  • Anacrotic limb: Rapid ejection of blood through aortic valve, sharp rise in pressure.
  • Systolic Peak: End of ventricular contraction, highest point of arterial waveform.
  • Dicrotic Limb: Gradual fall of pressure, filling peripheral vessels post ventricular contraction.
  • Dicrotic Notch: Aortic valve closure, pressure in ventricle less than aortic root.
  • End Diastole: Lowest point on arterial waveform.

Assessing Art Line accuracy

  • Zero line qshift/PRN
  • Turn transducer stopcock off to patient and remove and discard white cap.
  • Press zero on monitor and wait until monitor reads "0" and completion is indicated.
  • Alcohol swab the port and cover with a new white cap, place stopcock back into neutral position.

Square wave test

  • Preform square wave test q4hr/PRN
  • Pull pigtail briefly and quickly release.
  • Assess for oscillations and return to baseline

Underdamped

  • Underdamped- Extra oscillations after initial downstroke.
  • Blood pressure reading may be falsely high and cause artifact.
  • Check for air bubbles
  • Lengthen tubing

Overdamped

  • Overdamped- slow upstroke and loss of oscillations after initial downstroke.
  • Blood pressure may be falsely low and loss of dicrotic notch and waveform peak.
  • Clear system of blood or air.
  • Check for kinks.
  • Ensure flush fluid is not empty and pressure is maintained at 300 mmHg.
  • Hard flush
  • Shorten tubing

Troubleshooting

  • Assess distal extremity to cannulation site for adequate perfusion.
  • Alert provider immediately if patient is experiencing numbness, loss of pulse, or has signs of inadequate perfusion such as cyanosis or pallor.
  • Assess for bleeding
  • Try to determine if bleeding from insertion site or sutures.
  • Change dressing PRN, may need to consider gauze dressing
  • Provider may be able to assist if bleeding persists.
  • Assess for infection
  • Contact provider if purulent drainage or increased redness at site.
  • Assess for hematoma
  • May be a sign of arterial bleeding under the skin or may be from insertion.
  • Make provider aware and monitor for increasing hematoma size and firmness.

Abnormal Waveforms

1

Pulsus Alterans

Varying pulse strength, associated with heart failure

2

Pulsus Bisferiens

Double systolic peak, seen in aortic regurgitation

3

Reversed Pulsus Paradoxus

Increase in blood pressure during inspiration, caused by cardiac tamponade

4

Sluggish Anacrotic Limb

Slow upstroke in the arterial pulse wave, indicating aortic stenosis

5

Flattened Waveform

Decreased amplitude, seen in severe hypotension or cardiogenic shock

Pulsus Alterans

  • Alternating pulse amplitude related to deceased ventricular performance.
  • Regular and not impacted by respirations.
  • Pulse rate is regular and distinguished from a bigeminal pulse which would also result in a varying pulse amplitude but irregular rate.
  • Sometimes present in patients with severe CHF

Pulsus Bisferiens

  • Single pulse with two peaks with a distinct mid-systolic gap.
  • Causes include
  • Hypertrophic cardiomyopathy with obstruction
  • Aortic valve diseases.
  • Severe aortic regurgitation
  • Significant mitral valve prolapse
  • Large patent ductus arteriosus (PDA)
  • Arteriovenous fistula

Pulsus Paradoxus

  • Exaggerated fall in blood pressure during normal inspiration. To be considered Pulsus paradoxus a minimum of a 10mmHg fall in blood pressure is noted.
  • In extreme cases, pulse may completely disappear during inspiration.
  • Paradox is that heart sounds can be heard but pulse is not well felt during inspiration.
  • Most commonly concurrent with obstructive airway disease
  • May be an indication of cardiac tamponade.
  • Not as likely but could be caused by constrictive pericarditis, restrictive cardiomyopathy, or massive pulmonary embolism.

Reversed Pulsus Paradoxus

  • Increase of arterial systolic and diastolic pressures during inspiration.
  • It is related to increased left ventricle stroke volume.
  • Can be caused by an aortic outflow obstruction or stenosis.
  • Sometimes seen in patients with a permanent pacemaker with only ventricular leads.
  • In these patients the 'P" wave is sometimes superimposed with the paced ventricular beat. In this case the atrial kick is lost and ventricular stroke volume is decreased.
  • During inspiration the sinus rate increases slightly, placing the "p" wave slightly prior to the QRS thus adding back the atrial kick, causing an increase of blood pressure during inspiration.
  • Increased intrathoracic pressures in Ventilated patients with left sided heart failure and pulmonary congestion; squeezes blood from the pulmonary capillaries and forces it into the left ventricle resulting in an increased stroke volume during inspiration.

Rounded waveform with consistent systolic variation

  • Patient on ventilator with higher positive end-expiratory pressure (PEEP)
  • Difference between systolic pressure readings is less than 10mmHg
  • If difference is > 10mmHg consider pulsus paradoxus and be suspicious of cardiac tamponade

Sluggish Anacrotic Limb

  • Indicative of aortic stenosis
  • Auscultate for prolonged systolic ejection murmur and S2 splitting.

Flattened Waveform

  • Hypotension
  • If square-waveform test is normal, assess and treat for hypotension
  • Obstructed by clots or kinks
  • Check for loose connections
  • Overdamped
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