Femoral puncture is typically used to acquire blood from a patient in an emergency setting as both the veins and arteries are large vessels. In profound hypotension, unlike the radial, the femoral artery remains palpable. In a cardiac arrest, good quality CPR should result in a palpable pulsation. Typically a venous sample is preferred as there is a lower risk of excess blood loss.

However, it is not routinely as it has a tendency to bleed quite significantly and there are more structures to be wary of. Finally, the area is difficult to sterilise and hence there is an increased risk of introducing infection.

Indications for an arterial gas

• Hypoxia
• Drowsiness/reduced GCS or impaired respiratory effort
• Acute exacerbation chronic lung disease e.g. COPD, Asthma
• Unexpected deterioration
• Metabolic concerns: acid/base status or sepsis (lactate)
• Cardiac arrest (to ascertain reversible causes)
• Major trauma

Contraindications

• Overlying infection
• Through or distal to a bypass graft
• Patient refusal

Review of Anatomy “NAVY”

Equipment Needed

• ABG syringe – heparin filled (trust dependant) and blue needle
• Skin preparation/cleaning
• PPE
• Gauze/Tape/Plaster
• +/- Local anaesthetic

Procedure for Arterial Sampling

1. Ensure you have the equipment necessary
2. Ensure access to a sampler (ABG machine) including means of delivering the sample and accessing the results in a timely manner
3. Consent – if possible, otherwise proceed under best interest for clinical need
4. Consider your indication
5. Note the patient’s oxygen therapy % and their temperature (as gas sampling machine adjusts results based on these)
6. Identify your anatomy & femoral pulse
7. Clean the inguinal region with skin preparation & allow to dry
8. Attach the needle to the syringe, expel heparin or depress syringe to coat syringe depending on ABG syringe available to you
9. Proceed by inserting the needle at a 90-degree angle to the skin over the area of maximal arterial pulsation with the syringe drawn back to produce negative pressure until you see a flash of arterial blood in the needle
10. Allow the syringe to self-fill or withdraw plunger until adequate blood volume obtained (<1ml should do for an arterial blood gas sampling)
11. Remove the needle and replace with the supplied ABG cover
12. Apply adequate pressure over the puncture area, apply your selected dressing
13. Expel any air bubbles in the syringe & ensure the sample is kept moving whilst transporting it to the sampler urgently

For venous sampling, the same procedure above applies but you should aim medial of the pulse.

Complications

• Haematoma/Haemorrhage
• Emboli
• Infection
• Nerve or vessel damage/arteriospasm
• Pain
• Needlestick injury

References

• Case courtesy of Assoc Prof Craig Hacking, Radiopaedia.org, rID: 70536

Written by Mr Bakir Al-Dulaimy (Core Surgical Trainee)