**5. Acid base physiology**

Two types of variables, dependent and independent, are important in acid-base balance [20]. Bicarbonate, hydroxyl ion, hydrogen ion or pH, weak acid, anion and carbon trioxide are dependent variables and they are determined by three independent

**189**

*Acidosis and Anion Gap*

**7. Base excess approach**

**8. Stewart approach**

Here H<sup>+</sup>

then there is bicarbonate loss from the body.

CO2 [21]. The dependent variables are H+

Weak acid dissociates in body fluid (Eq. (3)).

*DOI: http://dx.doi.org/10.5772/intechopen.91760*

**6. Traditional physiological approach**

calculated by Hasselbalch-Henderson Equation (2) [7, 9].

pH. In this equation, PCO2 is the respiratory component and HCO3

traditional approach balance is determined by the influx and efflux of H+

variables pCO2, total weak acid and net strong ion charge [21]. Lungs, kidneys, liver and gut regulated this balance. Traditional bicarbonate/carbon-di-oxide approach, base excess approach and Stewert's physicochemical methods are widely discussed for measuring the acid base disorders as well as to explore the physiology of body fluid.

HCO3/CO2 buffer system is the basis of this approach. Carbonic acid freely moves in the body fluid and dissociates into bicarbonate automatically when needed. Bicarbonate in the body acts as alkaline reserve. CO2, pH and HCO3 can be

−

This equation states that not only HCO3 and CO2, but also their ratio determines the

Astrup and Siggaard-Anderson introduced base excess approach, which is close to the traditional approach [22, 23]. Base excess can be calculated from bicarbonate concentration and pH of the body [4]. It can estimate the acid base status of nonrespiratory origin. If base excess is too high, then it is metabolic alkalosis. If base excess is too low, then it is metabolic acidosis. When a deviation of normal blood pH is corrected by administrating base, then it is called base deficit. Which is a characteristic of metabolic acidosis. Base deficit with increase anion gap suggest the addition of acid in the body fluid. If there is a base deficit with normal anion gap,

/proton is the preliminary determinant in acid base disturbances, not the

, OH<sup>−</sup>, CO3

anions), HCO3<sup>−</sup> and pH. The independent variables are strong ion difference (SID), total non-volatile weak acids (Atot) and PaCO2 [24]. Among them the strong ion difference has maximum effect on the hydrogen ion concentration. With that, acid base disorder can be divided into three categories: 1. respiratory (increase or decrease PaCO2), 2. SID changes (excess or deficit of strong ions or water) and 3. inorganic phosphate or albumin deficit or excess (Atot changes). In Stewart approach, a large number of variables are needed to calculate SID. Sodium, potassium, calcium and magnesium are strong positive ions, and chloride and lactate are the negative ions [25]. Bicarbonate and albumin are the balancing ion in strong ion difference. Strong ion difference (mEq/L) = [strong cations] − [strong anions].

/s. PCo2] (2)

−

<sup>2</sup><sup>−</sup>, HA (weak acid), A<sup>−</sup>(weak

HA ← → H<sup>+</sup> + A<sup>−</sup> (3)

is the metabolic

and HCO3.

pH = pK + log10[HCO3

component of the acid base imbalance. This buffer system is the largest and independent buffer system of the body and whole body acts as an open system for CO2. In *New Insights into Metabolic Syndrome*

pH. Under normal environment Na+

<sup>−</sup> and Cl<sup>−</sup>) and H+

dent variables that regulate blood pH [15].

acid neutralizes strong base (Eq. (1)).

is then buffered by hemoglobin [18].

form than the oxygenated form [19].

, if there is H+

<sup>−</sup> and HPO4

and donate H+

in the blood H2PO4

**5. Acid base physiology**

in the kidneys.

acidification.

anion (HCO3

results in alkalosis, and decrease in BHCO3 and increase in H2CO3 results in acidosis [13]. The body contains many acids. They are hydrochloric acid, carbonic acid, citric acid, lactic acid, phosphoric acid and carboxylic acid. Acute metabolic acidosis is developed by the overproduction of organic acids, like lactic acid and keto acid. Chronic acidosis is caused by bicarbonate wasting and impaired urinary

Blood cells are more acidic than serum, which influences the distribution of electrolyte and water between them. These transports took place with the oxygen-

and K+

Shifting of water and electrolyte through membrane results from the change in

relative electrolyte concentration and weak acid concentrations are three indepen-

The body has different buffer systems to maintain the normal pH of the body. Elkinton Jr. reported that multiple level of buffering linked different series of ionic exchanges which includes hydrogen, sodium, potassium, and other anions. The buffers absorb excess hydrogen and hydroxyl ions. They help in the maintenance of

A buffer system consists of a weak acid with its conjugate base, or a weak base with its conjugate acid. Blood is a strong solution, and it has many important components that maintain the buffer systems. These include hemoglobin, bicarbonate, carbonic acid, plasma proteins, RBCs and plasma phosphate [17]. HCO3/CO2 buffer is the most important buffer system of the body, and plays a major role in regulating pH of the blood. But, the rest of the buffer systems have minimum contribution in pH regulation. In dissolved state, bicarbonate and carbon dioxide ion remains in equilibrium. Bicarbonate reduces strong acid to carbonic acid, whereas carbonic

CO2 + H2O <−−> H2 CO3 <−−> H<sup>+</sup> + HCO3

When CO2 and water is converted to HCO3 and hydrogen ions, this hydrogen ion

The phosphate buffer system works in the internal environment of all cells. But,

dihydrogen phosphate neutralizes strong bases and sodium monohydrogen phosphate neutralizes strong acids. The Phosphate buffer system plays an important role

Two types of variables, dependent and independent, are important in acid-base balance [20]. Bicarbonate, hydroxyl ion, hydrogen ion or pH, weak acid, anion and carbon trioxide are dependent variables and they are determined by three independent

Proteins have a buffering capacity, including hemoglobin. Protein can accept

of buffer action. When blood passes through the capillaries, it loses oxygen and took CO2 to raise the PaCO2 and maintain the pH. Hemoglobin plays an important role in transporting both oxygen and carbon dioxide. In 1914, Douglas, Haldane and Christiansen tried to prove that the hemoglobin binds more CO2 in the reduced

, K+

concentration, and that changes in cell volume. CO2,

do not diffuse through the cell wall.

−

excess or it is reduced. Hemoglobin has a distinct types

<sup>2</sup><sup>−</sup> are found in a very low concentration. Sodium

. (1)

) due to changes in

ation and reduction of hemoglobin and shift of bases (Na<sup>+</sup>

neutrality during redistribution of the hydrogen ion [16].

**188**

variables pCO2, total weak acid and net strong ion charge [21]. Lungs, kidneys, liver and gut regulated this balance. Traditional bicarbonate/carbon-di-oxide approach, base excess approach and Stewert's physicochemical methods are widely discussed for measuring the acid base disorders as well as to explore the physiology of body fluid.
