Canis ISSN: 2398-2942

Arterial blood gas sampling

Contributor(s): Graham Bilbrough, Martha Cannon, Elisa Mazzaferro, Sheilah Robertson

Introduction

  • Collection of an arterial blood sample can be performed using a direct arterial puncture with a needle and syringe, or by placing an indwelling arterial catheter Placing an arterial catheter.
  • Although more technically difficult than performing venipuncture, once the operator has had some experience, arterial blood samples can be easy to obtain.
    Follow the diagnostic tree for Blood Gas Analysis Blood gas analysis.

Uses

  • Arterial blood samples are the gold standard for measuring arterial oxygen (PaO2) and carbon dioxide (PaCO2) levels.
  • The arterial blood can also be used to determine metabolic acid-base status, and electrolyte concentrations.
  • The values obtained can be used to determine pulmonary exchange function by calculating Alveolar to arterial oxygen (A a ) gradients, and oxygenation fraction (PaO2/FiO2).

    Arterial catheters should not be used to supply drugs, blood products, or intra-venous fluids.

Advantages

  • Arterial blood sampling is the gold standard for measuring patient oxygenation status.
  • Obtaining an arterial blood sample is more labor intensive and invasive than determining patient oxygenation via pulse oximetry Anesthetic monitoring: pulse oximetry , the results are more reliable and not affected by patient/probe positioning, shivering, patient movement, pigmentation, external heaters or lights, hypothermia, or dyshemoglobinemias (methemoglobinemia, carboxyhemoglobinemia).
  • Rapid and minimally invasive technique.
  • Specialist equipment not required.

Disadvantages

  • Technically more difficult to place an arterial catheter or perform arterial puncture to obtain a sample.
  • Contraindicated in patients with coagulopathies.
  • May be painful for patient, as nerve often runs adjacent to the artery.
  • Possible to accidentally obtain a venous sample:
    • Genuine arterial samples will usually be a brighter red than a venous sample.
    • Results of blood gas analysis may suggest a venous sample was obtained.
  • Small risk of creating ischemia in extremity served by artery.
  • Ideally, analyze sample immediately. Sample will become less representative with time and air contamination. If it cannot be analyzed immediately, keep in air-tight container and store in ice.
  • Arterial catheters require frequent flushing to prevent clotting.
  • Kinks or knots can block catheter preventing sample collection.
  • Arterial spasm or hematoma formation can prevent further sample collection or placement of a catheter in the same artery.

Requirements

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Preparation

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Procedure

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Aftercare

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Wingfield W E, Matteson V L, Hackett T et al (1997) Arterial blood gases in dogs with bacterial pneumonia. J Vet Emerg Crit Care (2), 75-78 VetMedResource.
  • Wingfield W E, VanPelt D R, Hackett T, Martin L et al (1994) Usefulness of venous blood in estimating acid-base status of the seriously ill dog. J Vet Emerg Crit Care (1), 23-27 VetMedResource.
  • King L G, Anderson J G, Rhodes W H, Hendricks J C (1992) Arterial blood gas tensions in healthy aged dogs. Am J Vet Res 53 (10), 1744-1748 PubMed.
  • Ilkiw J E, Rose, R J, Martin I C (1991) A comparison of simultaneously collected arterial, mixed venous, jugular venous and cephalic venous blood samples in the assessment of blood-gas and acid-base status in the dog. J Vet Intern Med (5), 294-298 PubMed.


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