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ABG arterial blood gas sampling site radial artery technique
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ABG Sampling Sites
Here is a complete overview of the sites used for Arterial Blood Gas (ABG) collection:
1. Radial Artery (Most Common / First Choice)
- Located just medial to the styloid process of the radius, palpable between the radius and the flexor carpi radialis tendon
- Preferred because of its accessibility and the presence of collateral circulation via the ulnar artery (confirmed by the Allen Test before puncture)
- Needle inserted at a 45° angle, aimed toward the artery, bevel up
- Blood fills the syringe under arterial pressure - no need to pull back the plunger
- Apply firm pressure for 5 minutes after puncture
- First choice in adults, infants, and children
2. Brachial Artery
- Located in the antecubital fossa
- Used when the radial artery is not accessible
- Caution: The brachial artery has minimal collateral circulation, so thrombosis poses a significant ischemic risk
- Also carries risk of median nerve damage
- Reserved as a last resort in emergencies (especially in pediatric patients)
3. Femoral Artery
- Located in the groin; pulse palpated and needle inserted between two fingers placed longitudinally over the pulse
- Gives bright red arterial blood under pressure
- Site of choice in some surgical/emergency settings (e.g., Pye's Surgical Handicraft recommends it for adults)
- In infants and children, reserved for emergencies only due to higher risk of thrombosis
- Seal syringe immediately after collection to prevent air contamination
- Apply firm pressure for 3 minutes after puncture
4. Dorsalis Pedis & Posterior Tibial Arteries
- Alternative/optional sites, primarily in pediatric patients
- Each carries its own specific complication risks
5. Umbilical Artery (Neonates only)
- An indwelling umbilical artery catheter is the best method for blood gas specimens in neonates - minimizes repeated puncture trauma
6. Temporal Artery
- Not recommended - high risk of neurologic complications due to proximity to cerebral circulation
Allen Test (Pre-procedure for Radial Site)
Before radial artery puncture, perform the Allen test to confirm adequate ulnar collateral circulation:
- Compress both radial and ulnar arteries simultaneously
- Have the patient make a fist until the hand blanches
- Release the ulnar artery only
- If the hand flushes pink within 5-10 seconds - Allen test is positive (safe to proceed)
- If flushing is delayed or absent - inadequate collateral flow, choose another site
Quick Comparison Table
| Site | Collateral Flow | Angle | Notes |
|---|---|---|---|
| Radial | Good (ulnar) | 45° | First choice; needs Allen test |
| Brachial | Poor | 45° | Median nerve risk; last resort |
| Femoral | Good | 90° | Large vessel; emergencies, surgical use |
| Dorsalis pedis | Moderate | 45° | Pediatric alternative |
| Umbilical artery | N/A | Via catheter | Neonates only |
Sources:
- Pfenninger and Fowler's Procedures for Primary Care, 3rd ed. - Pediatric Arterial Puncture section
- Pye's Surgical Handicraft, 22nd ed. - Arterial Puncture section
- WHO Guidelines on Drawing Blood - Arterial Blood Sampling
- IEM Education Project - ABG Sampling 2025
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