Comparison of values of traditionally measured venous bicarbonate with calculated arterial bicarbonate in intensive care unit patients of a hospital in a third-world country

BACKGROUND: Measurement of serum or plasma bicarbonate (HCO3 (-)) from a sample of peripheral venous blood is routinely practiced in hospital patient managements. HCO3 (-) status can also be obtained by a simple calculation during blood gas analysis requiring arterial blood as sample which is cumbersome for both patient and doctor. This study compared the measured bicarbonate levels with calculated arterial values in intensive care unit (ICU) patients to determine whether traditionally measured venous HCO3 (-) and calculated HCO3 (-) values [from arterial blood gas (ABG) analyzers] can be used interchangeably. MATERIALS AND METHODS: This prospective study was carried out at a tertiary care teaching hospital in Dhaka, the capital of Bangladesh. A total of 56 adult patients with diverse medical conditions, presenting at the ICU of the health centre were enrolled in this study when deemed by the treating physician to have an ABG analysis. Arterial and venous samples were taken as close in time as possible for gas analysis and routine blood tests. RESULTS: The HCO3 (-) levels from ABG and traditionally measured serum showed acceptably narrow 95% limits of agreement using the Bland-Altman method. CONCLUSIONS: More widely prescribed venous HCO3 (-) measurements can also be a useful substitute for an expensive ABG analyzer in resource-constrained health care sectors when required. However, accuracy of venous blood in assessment of additional ABG parameters is yet to be discovered.