When is arterial catheter placement indicated, which artery is preferred, what are the contraindications (e.g., INR > 1.5, platelets < 50 × 10⁹/L, local infection, arterial disease), and what is the step‑by‑step aseptic technique for insertion, securing, monitoring, and removal?

Arterial Line Insertion: Evidence-Based Guidelines

Indications for Arterial Catheter Placement

Arterial catheterization is indicated for continuous hemodynamic monitoring in critically ill patients and high-risk surgical patients requiring real-time blood pressure assessment and frequent arterial blood sampling. 1

• Place arterial lines when continuous invasive BP monitoring is required in hemodynamically unstable patients, those receiving vasopressors, or during high-risk surgery 1, 2
• Arterial access facilitates repetitive blood sampling without repeated punctures in critical care settings 3
• Consider arterial catheterization when noninvasive BP monitoring may be unreliable (severe hypotension, arrhythmias, vasopressor infusion) 4

Contraindications

Relative Contraindications

• Severe peripheral vascular disease – increases risk of ischemic complications 5
• Coagulopathy – though bleeding risk is lower than commonly believed 5
• Local synthetic grafts at the insertion site 5

Important Clarification on Coagulopathy

Routine correction of coagulopathy is NOT required unless platelet count < 50 × 10⁹/L, aPTT > 1.3 × normal, or INR > 1.8. 5

• Below these thresholds, hemorrhage risk during arterial catheterization is not increased 5
• The risks of prophylactic correction (infection, lung injury, thrombosis) may exceed local bleeding risk 5
• Therapeutic anticoagulation alone does not mandate routine laboratory testing before arterial line placement 6

Preferred Arterial Site Selection

The radial artery is the preferred first-choice site for arterial catheterization when a suitable peripheral site is available. 5

Site Selection Algorithm

1. First choice: Radial artery 5, 3

   • Most commonly used in surgical ICU patients (78% of cases) 3
   • Easily compressible, superficial location 5
   • Major complications (permanent ischemic damage, sepsis, pseudoaneurysm) occur in < 1% of cases 5

2. Alternative peripheral sites: Brachial artery 3

   • Used in 0.5-3% of cases when radial access is not feasible 3
   • Similar complication rates to radial and femoral sites 5

3. Femoral artery 5, 3

   • More commonly used in medical ICU patients (45% of cases) 3
   • Some studies report higher catheter-related infection rates, though major complication rates are similar to peripheral sites 5
   • May be preferred in patients with severe coagulopathy due to easier vessel compression 5

Pre-Insertion Assessment

Do NOT rely on Allen's test to assess collateral perfusion – it is unreliable. 5

• Use ultrasound to assess vessel patency and size before insertion 5
• Ultrasound guidance significantly increases first-attempt success rates and decreases complications compared to landmark-based techniques 5, 2

Step-by-Step Insertion Technique

Preparation

• Use strict aseptic technique for all arterial catheter insertions 5
• Employ needle guards to reduce needlestick injury risk 5
• Choose the smallest practical catheter size to minimize vessel trauma 5

Insertion Methods

Two primary techniques are available: 5

1. Catheter-over-needle technique
2. Catheter-over-wire (Seldinger or modified Seldinger) technique

Ultrasound-Guided Insertion (Strongly Recommended)

Ultrasound guidance for radial arterial cannulation significantly improves first-attempt success rates. 5, 2

• Ultrasound is particularly valuable in critically ill patients with hypotension, peripheral edema, or obesity 2
• Multiple ultrasound techniques exist for both radial and femoral arterial catheter insertion 2
• Use color Doppler to confirm vessel patency and assess flow 5

Insertion Steps

1. Position the patient appropriately with the target limb accessible and supported 1
2. Prepare the insertion site with antiseptic solution using aseptic technique 5
3. Use ultrasound to identify the target artery and assess vessel size and patency 5, 2
4. Infiltrate local anesthetic if the patient is awake 1
5. Insert the catheter using either direct puncture or Seldinger technique 5
6. Confirm arterial placement by pulsatile blood return 1
7. Secure the catheter meticulously to prevent dislodgement 1

Post-Insertion Management and Monitoring

Transducer Setup

• Level and zero the transducer correctly to ensure accurate BP readings 1
• The transducer should be leveled to the phlebostatic axis (mid-axillary line at the fourth intercostal space) 1

Waveform Quality Assessment

Check the quality of the BP waveform immediately after insertion and continuously during monitoring. 1

• A high-quality arterial waveform has a sharp upstroke, clear dicrotic notch, and appropriate morphology 1
• Poor waveform quality may indicate catheter malposition, air bubbles, or damping 1

Flushing Protocol

Use ONLY heparinized saline to flush arterial catheters – never use glucose solutions. 5

• UK national alerts have documented severe hypoglycemia from misdirected insulin administration when glucose solutions were used to flush arterial lines 5
• Flush the catheter after each blood sampling to maintain patency 5

Site Rotation

• There is no evidence to support routine rotation of arterial catheter sites 5
• Change the site only when clinically indicated (infection, malfunction, ischemia) 5

Complications and Their Management

Major Complications (< 1% incidence)

• Permanent ischemic damage 5
• Sepsis 5
• Pseudoaneurysm 5

Common Complications

• Vascular insufficiency (3.4-4.6% of cases) – most common complication 3
• Bleeding (1.8-2.6% of cases) 3
• Infection (0.4-0.7% of cases) 3

Complication Rates by Site

Infection rates are similar between radial and femoral arterial sites, contrary to widespread belief. 3

• Major procedural complications are similar for radial, femoral, and brachial sites 5
• Vascular insufficiency and bleeding are more common after catheter changes using a guidewire 3
• Arterial spasm and pulselessness occur more frequently after new-site insertion 3

Catheter Removal

Removal Technique

• Position the patient flat with the exit site below heart level to reduce air embolism risk 5
• Apply firm digital pressure for at least 5 minutes 5
• Place an occlusive dressing after achieving hemostasis 5
• Use a skin stitch if persistent bleeding occurs 5

Coagulation Thresholds for Safe Removal

Routine reversal of coagulopathy before arterial line removal is only required when platelet count < 50 × 10⁹/L, aPTT > 1.3 × normal, or INR > 1.8. 5, 6

• The compressible nature of arterial puncture sites permits safe removal even during therapeutic anticoagulation 6
• Do not order routine labs before every arterial line removal – this adds cost without improving safety 6

Critical Pitfalls to Avoid

• Do NOT use Allen's test as the sole assessment of collateral circulation – it is unreliable 5
• Do NOT flush arterial lines with glucose solutions – use only heparinized saline to prevent medication errors 5
• Do NOT routinely correct coagulopathy when INR < 1.8, aPTT < 1.3 × normal, and platelets > 50 × 10⁹/L 5, 6
• Do NOT avoid arterial catheterization in patients on therapeutic anticoagulation – the compressible site allows manageable bleeding 6
• Do NOT place arterial lines without ultrasound guidance when available – it significantly improves success rates 5, 2
• Do NOT routinely rotate arterial catheter sites – change only for clinical indications 5