Improper arterial catheter blood sampling method affects hemoglobin test results: A cautionary tale

Area of Science:

• Clinical Pathology
• Critical Care Medicine
• Medical Laboratory Science

Background:

• Arterial catheter blood sampling is common in critically ill patients to avoid repeated venipunctures.
• Improper sampling techniques can lead to significant pre-analytical errors and misleading laboratory results.
• Hemoglobin discrepancies between analyzers can impact clinical decision-making.

Purpose of the Study:

• To report a case of significant hemoglobin discrepancy during arterial catheter sampling.
• To identify pre-analytical errors contributing to artifactual hemoglobin variations.
• To emphasize the importance of proper catheter sampling techniques in critical care.

Main Methods:

• A case report detailing hemoglobin analysis from arterial catheter samples in a patient with cerebral infarction.
• Comparison of hemoglobin values obtained from a blood gas analyzer and an automated hematology analyzer.
• Investigation of pre-analytical factors, including discard volume and sample contamination.

Main Results:

• A clinically significant hemoglobin discrepancy of 13 g/L was observed between analyzers post-catheterization.
• The discrepancy was attributed to inadequate discard volume (4-5 mL) of heparinized saline-contaminated blood, causing sample dilution.
• Prior concordance in hemoglobin values was lost after catheter placement.

Conclusions:

• Inadequate discard volume during arterial catheter sampling can lead to sample dilution and artifactual hemoglobin variations.
• Strict adherence to catheter sampling protocols, focusing on dead space clearance, is essential for accurate laboratory results.
• Tailoring discard volume guidelines based on patient factors is critical for ensuring test accuracy in hemodynamically unstable patients.