2007, Number 2
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Med Sur 2007; 14 (2)
Approach of the acid-base balance according to the physicochemical Stewart model
Carrillo ER, Carrillo CJR, Carrillo CLD
Language: Spanish
References: 22
Page: 56-63
PDF size: 93.55 Kb.
ABSTRACT
All modern theories of acid-base balance are based on physiochemical principles. As Thermodynamic state equations are independent of path, any convenient set of parameters may be used to describe a physiochemical system. The traditional model of acid-base balance in plasma is based on the distribution of proton acceptor sites, whereas the Stewart model is based on the distribution of electrical charge. Although sophisticated an mathematically equivalent models may be derived from either set of parameters, proponents of the traditional or proton acceptor site approach have advocated simple formulae whereas proponents of the Stewart or electrical charge method have emphasized mathematical rigor. The Stewart model examines the relationship between the movement of ions across biologic membranes and the consequent changes in pH. The Stewart equation relates changes in pH to changes in the three variables, total concentration of weak acids, strong ion difference and pCO
2. The Stewart model corrects the traditional computations of buffer curve, base excess and anion gap. This model has reawakened interest in quantitative acid-base chemistry and has prompted a return to the first principles of acid-base physiology.
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