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  Arterial puncture for blood gas analysis is a common procedure performed in the emergency department (ED).

  
  
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  Blood obtained from the radial artery can be used to quickly provide quantitative information on the patient’s acid–base status and carboxyhemoglobin, methemoglobin, and electrolyte levels.

  
  
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  Arterial puncture is a useful way to obtain blood for analysis when traditional phlebotomy is limited or difficult on the basis of patient characteristics.

The primary indication for obtaining an arterial blood sample is for the assessment of the partial pressures of oxygen and carbon dioxide and accurate assessment of arterial pH. Secondarily, arterial blood can be analyzed for carboxyhemoglobin, methemoglobin, and basic electrolytes depending on the capabilities of the laboratory. Under certain circumstances it may be necessary to obtain a sample of arterial blood for other routine laboratory tests, such as in patients who are obese or have a history of intravenous drug abuse, in whom the radial artery is palpable, but venous access is difficult or may be delayed.

There are few absolute contraindications for arterial puncture for blood gas analysis. Trauma, infection, or abnormalities of the overlying skin such as a burn are contraindications because of concern for infection or further damage to the vascular structures. Patients with known coagulopathies, taking anticoagulants, or who may require thrombolytic agents should be approached with caution because of the increased risk of bleeding, hematoma formation, or rarely, compartment syndrome. Finally, a known history of insufficient blood flow through the palmar arch or previous surgery to the radial or ulnar arteries should also be considered a contraindication. The Allen test, described later, has been used as a way to determine adequacy of collateral circulation, however, its necessity has been questioned.

Many commercially prepared kits for arterial puncture are available, and if a commercial kit is not available, then equipment is easily found in most EDs. The following equipment is typically used to perform the procedure (Figure 2-1).