Arterial blood gas analysers: accuracy in determining haemoglobin, glucose and electrolyte concentrations in critically ill adult patients.

Arterial blood gas (ABG) machines are vital tools in the assessment of critically ill patients. Current ABG point-of-care (POC) analysers provide information on concentrations of haemoglobin, glucose and electrolytes in addition to acid-base balance. Awaiting results from venous analysers may present a significant delay in diagnosis and management, thus reliance on arterial blood gas determination of these parameters is increasing. However, published data on the concordance between the two modalities are limited. This study aims to assess the concordance of ABG machines in analysing haemoglobin, glucose and electrolyte concentrations compared to standard venous analysers as the gold standard. Results from 100 patients undergoing ABG analysis and simultaneous venous sampling without therapeutic intervention between sampling were compared. Differences in haemoglobin, glucose, sodium and potassium concentrations were determined and analysed using statistical software (Statview). There was a significant difference (P < 0.02, paired signed test) in the mean haemoglobin concentration between the two modalities of 0.91 g/dL (range: 0-4.3 g/dL). Mean discrepancy in glucose concentrations was 1.16 mmol/L (range: 0-10.5 mmol/L; P < 0.012, paired-signed test). Sodium and potassium showed no significant difference within the physiological range. At higher concentrations of potassium (> 5 mmol/L), ABG readings varied significantly (P < 0.0013, paired sign test) from standard venous estimates (mean difference: 0.44 mmol/L). Arterial blood gas analysers are invaluable for rapid assessment of critically ill patients; however, estimations of haemoglobin, glucose and potassium concentrations (> 5 mmol/L) obtained from such machines should be interpreted with caution and confirmed using standard venous samples.