The accuracy of arterial blood gas analysis in detecting electrolytes and anionic gap in ICU patients

Objective To explore the accuracy of bedside arterial blood gas analyzer in detecting electrolytes and anionic gap (AG) in ICU patients, and compare it with auto-analyzer. Methods Results of blood sodium, potassium, chlorine, bicarbonate ions and AG measured by arterial blood gas analyzer and auto-analyzer of 376 ICU adult patients admitted to ICU were retrospectively analyzed. With the outcomes of auto-analyzer as standard, the correlation and difference of electrolytes and AG measured by 2 methods were analyzed. Results The sodium, potassium, chlorine and AG measured by auto-analyzer were 121 -183 mmol/L, 2.13 -6.77 mmol/L, 86 -146 mmol/L and 1 -62 mmol/L. The blood sodium, potassium, chlorine and AG measured by arterial blood gas analyzer were 114 -180 mmol/L, 1.78 -6.36 mmol/L, 94 -150 mmol/L, -7 -40 mmol/L. The blood sodium, potassium and AG measured by arterial blood gas analyzer were lower than those measured by auto-analyzer, but the blood chlorine was higher than that measured by auto-analyzer. There were statistical differences in the difference of low, normal and high electrolytes and AG between 2 methods (P <0.01). Conclusions The electrolytes and AG measured by arterial blood gas analyzer and auto-analyzer are significantly different, and the electrolytes measured by arterial blood gas analyzer are unreliable to calculate AG. Key words: Blood gas analysis; Electrolytes; Anions; Intensive care units; Retrospective studies