Serum potassium level as a biomarker for acute caffeine poisoning.

AIM

Acute caffeine poisoning presents with hypokalemia, although a relationship between potassium levels and blood concentrations of caffeine has not been established. A correlation between serum potassium level and blood caffeine concentration could establish serum potassium as a simple marker to assess caffeine toxicity in patients with acute toxicity. We investigated whether serum potassium, a symptom of acute caffeine poisoning, could be a parameter correlated with blood caffeine levels.

METHODS

We enrolled 85 patients treated for acute caffeine poisoning between January 2012 and March 2019 with blood caffeine levels measured after an overdose of a caffeine-containing over-the-counter drug and for whom serum potassium levels were available. We examined the correlation between serum potassium and blood caffeine concentration. A receiver operating characteristic curve was created with serum potassium values to stratify participants into two groups by blood caffeine concentrations: <20 or ≥20 mg/L (toxic dose) and <80 or ≥80 mg/L (lethal dose). The lethal cut-off value was calculated.

RESULTS

The correlation coefficient between serum potassium level and blood caffeine concentration was -0.612 (  = 0.374), indicating a negative correlation. The areas under the curve at blood caffeine concentrations of 20 mg/L (toxic dose) and 80 mg/L (lethal dose) and serum potassium levels were 0.716 and 0.888 (sensitivity, 0.829 and 0.919; specificity, 0.568 and 0.818; cut-off, 3.3 mEq/L and 2.9 mEq/L), respectively.

CONCLUSION

Serum potassium levels are associated with blood caffeine concentrations; K of 3.3 mEq/L and 2.9 mEq/L indicate acute caffeine poisoning in the toxic and lethal dose, respectively.