Draft

76  Arterial Line

76.1 What this covers

  • Contraindications and complications
  • Indication
  • Site

76.2 Learning objectives

  • Contraindications and complications
  • Indication
  • Site
  • Brachial
  • Femoral
  • Axillary
  • Square Wave test

76.3 Bottom line / summary

  • Most commonly, radial artery of non-dominant hand.
  • Other options: femoral (central), dorsalis pedis, ulnar, brachial, axillary (central).
  • Deep dive to different locations here: https://emcrit.org/pulmcrit/a-line/
  • Complication rates: https://journals.lww.com/anesthesia-analgesia/Fulltext/2014/02000/BrachialArteryCatheterizationAnAssessmentof.9.aspx
  • Possibly safer than billed?

76.4 Approach

  1. arterial BP readings (note: central axillary, fem are more reliable and do not correlate all that well). MAP is still the most reliable indicator (as it is a surrogate for the perfusion pressure)
  2. frequent blood gas
  3. 2% chlorhexadine skin prep dispensers
  4. 2% lidocaine (1-3 ml), with syringe and 25g needle
  5. sterile drape

76.5 Red flags / when to escalate

  • TODO: List red flags that require urgent escalation.

76.6 Common pitfalls

  • arterial BP readings (note: central axillary, fem are more reliable and do not correlate all that well). MAP is still the most reliable indicator (as it is a surrogate for the perfusion pressure)

76.7 References

  • https://emcrit.org/pulmcrit/a-line/
  • https://journals.lww.com/anesthesia-analgesia/Fulltext/2014/02000/BrachialArteryCatheterizationAnAssessmentof.9.aspx
  • https://pubmed.ncbi.nlm.nih.gov/28523028/
  • flightbridgeed.com/index.php/blogs/blogs-view/10-artcles/277-well,-i-ll-be-damped-–-how-square-wave-testing-can-assure-accuracy-in-your-hemodynamic-monitoring-interpretations

76.8 Source notes

76.8.1 Arterial Line

77 Arterial Line

77.1 Contraindications and complications

Vascular injury?

77.2 Indication

  • arterial BP readings (note: central = axillary, fem are more reliable and do not correlate all that well). MAP is still the most reliable indicator (as it is a surrogate for the perfusion pressure)
  • frequent blood gas

77.2.1 Materials

  • 2% chlorhexadine skin prep dispensers
  • 2% lidocaine (1-3 ml), with syringe and 25g needle
  • sterile drape
  • 20g cannula (kit) 22g = micropuncture, larger for axillary/femoral. (they are color coded). Cook vs Arrow
  • extension to transducer, 3 way tap to connect to cannula

77.2.2 Site

Most commonly, radial artery of non-dominant hand. Other options: femoral (central), dorsalis pedis, ulnar, brachial, axillary (central).

Deep dive to different locations here: https://emcrit.org/pulmcrit/a-line/

77.2.2.1 Brachial

Complication rates: https://journals.lww.com/anesthesia-analgesia/Fulltext/2014/02000/Brachial_Artery_Catheterization___An_Assessment_of.9.aspx

77.2.2.2 Femoral

Possibly safer than billed? Can be converted for IR procedures, ECMO, etc.

77.2.2.3 Axillary

Have patient place arm behind head.

77.2.3 Technique (Radial)

  • support wrist in slight dorsiflexion -palpate artery

  • steeper line of entry (45 degree entry). When flash is achieved, lower to 30 degree.

77.3 Invasive Blood Pressure Monitoring

Radial arterial lines (probably all peripheral) likely significantly underestimate the central BP (e.g. https://pubmed.ncbi.nlm.nih.gov/28523028/) – if need to know, go for fem or axillary.

77.3.1 Dampening

the amount that a pressure wave transmits from the blood and through the tubing to the transducer. Reference

Over-damped = not transmitting pressure, such as if there is air in the tubing (compressible), a clot in the catheter, kinked/stiff tubing, or catheter is against a wall. Will be indicated by a loss of the dicrotic notch. MAP will still be accurate, but systolic will be underestimated, diastolic will be overestimated, and pulse pressure will be underestimated.

Under-damped = ringing vibrations in the tube. Exagerated dicrotic notch. Overestimate of systolic, underestimate of diastolic, overestimate of pulse pressure. Caused by long tube, many stopcocks, and tachycardia/high cardiac output.

Dicrotic notch = upstroke in the descending part of the tracing due to closure of aortic valve pushing fluid into aorta.

77.3.1.1 Square Wave test

you flush a high pressure wave of saline/heparin through the line, then see how much it reverberates in the line to estimate how easily pressure is transmitted through the system. Over-damped = 1 oscillation; perfect = 2 oscillations; under-damped = many.

77.4 Source materials