blood gas vs. serum electrolytes

26 Mar

HOW CLOSE ARE THEY?
–not a lot of data
–pubmed biopsy produced only 2 articles

ARTICLE 1:
–“Diagnostic accuracy of venous blood gas electrolytes for identifying diabetic ketoacidosis in the emergency department”
–looked at 46 DKA patients, compared serum and VBG electrolytes

  • sensitivity of VBG electrolytes for diagnosing DKA: 97.8%
  • specificity of VBG electrolytes for diagnosing DKA: 100%
  • Correlation coefficients between VBG and serum chemistry
    • sodium 0.90
    • chloride 0.73
    • bicarbonate 0.94
    • anion gap 0.81

ARTICLE 2:
–“Comparison of the point-of-care blood gas analyzer versus the laboratory auto-analyzer for the measurement of electrolytes”
–looked at 200 ICU patients, compared ABG and serum lab Na+ and K+

  • mean ABG sodium value was 131.28 (SD 7.33)
  • mean lab sodium value was 136.45 (SD 6.50) (p < 0.001).
  • mean ABG potassium value was 3.74 (SD 1.92)
  • mean lab potassium value was 3.896 (SD 1.848) (p = 0.2679).

–conclusions: no significant difference between the potassium values; however, the difference between the measured sodium was found to be significant
–decisions can be made by trusting the K+ values obtained from ABG (less so with the sodium)

BOTTOM LINE:
–how close are blood gas electrolytes to the lab serum electrolytes?
not much data, seems close enough for acidosis, potassium
–not as good for sodium

Submitted by S. Lee.


Reference(s): article 1, article 2, picture

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