blood gas vs. serum electrolytes

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