Efrida Efrida, Ida Parwati, Ike Sri Redjeki


Metabolic acidosis is the most frequent acid-base disorder in patients of the Intensive Care Unit. By conventional approach based on
pH value, [HCO3
–], and base deficit (BD) from blood gas analyzer (BGA) measurement are often inappropriate with the clinical state
and inadequate in explaining the mechanism of the metabolic acidosis. The Stewart approach states that the blood pH is determined
by a strong ion difference (SID), the carbon dioxide tension (pCO2), the total concentration of non-volatile weak acid. The Stewart
approach may give a better understanding of the mechanisms that underlie the metabolic acidosis. The purpose of this study is to know
the correlation of blood pH value measurement from BGA and calculation based on Stewart approach and identifying the mechanisms
that underlie a metabolic acidosis. In this study an analytic observational cross-sectional method was used. The examined subjects
consisted of 71 patients who were admitted with a metabolic acidosis at the ICU from July up to August 2007. All patients were measured
for their blood pH, pCO2, [HCO3
–], BD, sodium, potassium, calcium, magnesium, chloride, lactate, albumin, and phosphate. The result
was reported as the mean and standard deviation. The data were analyzed by Pearson’s correlation test and linier multiple regression.
Statistical significance was determined at p < 0.05. The mean values of blood pH measurement from BGA and blood pH calculation
based on the Stewart approach were 7.33 (0.11) and 7.49 (0.11) (r = 0.681; p < 0.001). Most patients had two underlying mechanisms of
metabolic acidosis. Hyperlactatemia was present in 61.8%, hyperchloremia was present in 58.2% of patients. Based on this study so far,
by using the Stewart approach there is an excellent and significant correlation between the blood pH measurement from BGA and blood
pH calculation. Hyperlactatemia and hyperchloremia are the main causes of the metabolic acidosis in patients of the ICU ward.


The Stewart approach, metabolic acidosis, blood pH, hyperlactatemia, hyperchloremia

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