Arterial Line (A-Line)

David Ray Velez, MD

Indications and Site Selection

Indications

Continuous Blood Pressure Monitoring – The Primary Indication and Use
- Hemodynamic Instability
- Titration of Vasoactive Agents
- Morbid Obesity and Unable to Use a Non-Invasive Blood Pressure (NIBP) Cuff
Frequent Blood Sampling
Arterial Drug Administration
Use of an Intra-Aortic Balloon Pump (IABP)

Site Selection

Allen Test

A Procedure to Evaluate the Adequacy of Collateral Blood Flow to the Hand Before Arterial Line Placement to Prevent Hand Ischemia
Technique:
- Manually Occlude Radial and Ulnar Arteries
- Clench Hand 10-Times
- Release Ulnar Artery While Still Occluding the Radial Artery
- Monitor Capillary Refill
Interpretation:
- Negative: Capillary Refill > 6 Seconds
  - Indicates Inadequate Contralateral Flow
- Positive: Capillary Refill < 6 Seconds
  - Indicates Adequate Contralateral Flow
Use in Practice is Debated Due to Poor Accuracy and Interobserver Agreement

Techniques

Blind Placement: Based Solely on Anatomy and Palpation without US Guidance
Ultrasound Guidance: Placed Using an Ultrasound in Real-Time
- Benefits to Ultrasound Use:
  - Increased First-Pass Success
  - Decreased Complication Rate
  - Decreased Failure Rate
- Should Always be Utilized if Available
*Either Method Utilizes a Seldinger Technique

Position/Prep – Radial Artery

Use a Flexible Board or Rolled Towel to Stabilize the Wrist in Dorsiflexion
Extension of the Wrist to 45-Degrees Increases Anterior-Posterior Arterial Diameter and Success Rate
Procedure Should be Performed in a Sterile Manner Unless Absolutely Unable (“Dirty Lines” Used in Trauma for a Crashing Patient in Hemorrhagic Shock)
Consider Performing an Allen Test Prior to Placement – Debated
Inject Local Anesthetic as Appropriate

Position/Prep – Axillary Artery

Anterior Chest Approach:
- Supine with Arms Tucked (Similar to a Subclavian Approach)
- Vessels Located Between the Crease of the Arm and Clavicle in the Deltopectoral Groove
Axillary Approach:
- Open the Axilla by Abduction and External Rotation of the Arm 90-135 Degrees
- May Need to Shave Axilla
- Take Caution to Approach Medially Enough to Avoid the Axillary Artery
Procedure Should be Performed in a Sterile Manner Unless Absolutely Unable (“Dirty Lines” Used in Trauma for a Crashing Patient in Hemorrhagic Shock)
Inject Local Anesthetic as Appropriate

Seldinger Technique

Needle
- Puncture the Artery with a Hollow Introducer Needle
- Needle is Generally Not Attached to a Syringe and Rather Left Open to Monitor Pulsation
- Bright Red Pulsatile Blood Indicates Arterial Puncture
Guidewire
- Pass a Guidewire Through the Needle
- Withdraw the Needle Over the Guidewire, Leaving the Guidewire in Place
- Always Maintain Control of the Guidewire During Placement – Should Never Completely Enter the Artery
Place the Catheter
- Make a Small Skin Incision at the Entry Site
- Do Not Need to Dilate the Tract
- Pass Catheter Over the Guidewire
- Withdraw Guidewire
- Attach the Catheter to the Monitor and Confirm Waveform
Suture Catheter to the Skin and Place a Sterile Dressing

Seldinger Technique – Dart/Arrow Kit

*A Vascular Access Device Kit with a 20 Gauge Angiocatheter and a Preloaded Wire within a Plastic Tube
*Only Used in the Radial Artery
Needle
- Puncture the Radial Artery with the Dart Needle
- Bright Red Pulsatile Blood into the Tubing Indicates Arterial Puncture
Guidewire/Catheter
- Pass the Guidewire Through the Needle
- Advance the Catheter Over the Guidewire
- Withdraw the Guidewire/Needle, Leaving the Catheter
- Attach the Catheter to the Monitor and Confirm Waveform
Suture Catheter to the Skin and Place a Sterile Dressing

Radial Artery

Axillary Artery: Outer Border of the First Rib to the Lateral Border of the Teres Major

Arterial Waveform

Under-Dampened System

Definition: Waveform Appears Saltatory and Abrupt with an Exaggerated Dicrotic Notch
Pressure Changes:
- Increased Systolic Blood Pressure (SBP)
- Decreased Diastolic Blood Pressure (DBP)
- Increased Pulse Pressure
Causes:
- Excessively Long Tubing Length
- Multiple Stopcocks

Over-Dampened System

Definition: Waveform Appears Flattened with a Small Amplitude and Loss of the Dicrotic Notch
Pressure Changes:
- Decreased Systolic Blood Pressure (SBP)
- Increased Diastolic Blood Pressure (DBP)
- Decreased Pulse Pressure
Causes:
- Air Bubbles in the Tubing
- Arterial Thrombus
- Tube Kinging

Arterial Waveform

System Dampening

Bloodstream Infection (BSI)

Incidence: 1.6 Infections/1,000Catheter Days
- Similar Risk as Short-Term Central Venous Catheters (CVC) Despite Dogma that States Arterial Lines Rarely Get Infected
Most Common Source: Skin Colonization
Most Common Organism: Staphylococcus epidermidis
Highest Risk Site: Femoral Artery
Chlorhexidine Impregnated Dressings (BioPatch) Decrease the Risk
Full Barrier Precautions May Not Decrease the Risk Compared to Sterile Gloves Alone for Radial Lines – Minimal Data to Support/Reject

Hand Ischemia After Radial Artery Catheterization

Thrombosis/Temporary Arterial Occlusion is the Most Common Complication of Radial Artery Catheterization (20-33%)
Clinically Significant Ischemia is Rare (< 0.1%)
Brachial Artery is the Highest Risk Site
Risk Factors:
- Low BMI
- Female Gender
- Advanced Age
- Vascular Disease
- Vasopressor Use
- Prolonged Hypotension
- Larger Catheter Size
- Prolonged Catheter Placement (> 48-72 hr)
- Trauma from Multiple Attempts at Placement
General Management: Remove Catheter and Anticoagulation
- May Require Surgical Intervention (Embolectomy, Bypass, or Amputation)

Other Complications