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ISSN 2448-8909 (Print)

2006, Number 4

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Med Crit 2006; 20 (4)

Acido-base balance. Current concepts

Carrillo ER, Visoso PP

Language: Spanish
References: 27
Page: 184-192
PDF size: 120.73 Kb.


ABSTRACT

Acid-base (AB) equilibrium alterations are common in the intensive care unit (ICU) and when they are extreme and develop quickly cause organ dysfunction, increasing the morbi-mortality. The Henderson-Hasselbalch model does not explain satisfactorily these alterations in the critical ill patient. The approach of the acid-base alterations proposed by Stewart is fundamented in the mass conservation and electroneutrality laws and explains that the hydrogen ions and consequently the pH origin come from the water dissociation produced by and increment of the strong ions difference (SID), the partial pressure of carbon dioxide (pCO2) and total concentration of dissociated weak non-volatile acids (ATOT).
There are three models to approach the AB alterations, the one, Henderson-Hasselbalch model is fundamented in the mass action law taking independent variables like bicarbonate anions (HCO3-) and the pCO2, a systematized diagnostic approach of this model is the Rule of Five, that can be used to diagnose simple, double and triple AB alterations. The second model has evolved till the concept of titratable H+ concentration of the extracellular liquid (ctH+ Ecf), defined as the number of H+ added or removed in relation to pH of reference which is 7.40, this model uses the Van Slyke equation and Siggaard-Andersen diagram to calculate and graphic respectively the AB alteration. The third is Stewart’s model, which is fundamented in the mass conservation and electroneutrality laws, taking like independent variables the pCO2, SID and Αtot, all this variables cause water dissociation and consequently more hydrogen ions. From this approach, come out, diagnoses like hyperchloremic metabolic acidosis (HCMA) and metabolic acidosis of unmeasured anions, the first one secondary to reanimation with unbalanced solutions, and the second one to sepsis.


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