Abstract
It would be clinically useful to be able to estimate bicarbonate concentration (BC) from standard blood biochemical values in hemodialysis patients, because at present bicarbonate concentration is usually measured by blood gas analysis. The formula for estimating bicarbonate concentration was determined from blood gas analyses and blood biochemical values using samples obtained from 83 hemodialysis patients. Because anion gap (AG) is well correlated with serum inorganic phosphorus concentration (IP), we were able to estimate anion gap with the formula IP (AG=7.33+IP×0.99). We transformed the formula of anion gap (AG=Na-Cl-BC) and were able to derive the formula of estimated bicarbonate concentration (BC=Na-Cl-IP×0.99-7.33). We further simplified the formula to ‘estimated BC=Na-Cl-P-7’ for ease of use at the bedside. Results from this ‘estimated BC’ formula correlated well with bicarbonate concentration values determined by gas analysis (r=0.76). The present study indicates that hyperphosphatemia is an important factor in metabolic acidosis related to increased anion gap and is associated with other unmeasured fixed acids in hemodialysis patients.
