Blood buffer calculations

It is apparent from the pK values that neither equilibrium can serve as a buffer system at the physiological pH of 7.4. However, carbonic acid (the proton donor) is in equilibrium with dissolved CO2, which in turn is in equilibrium with gaseous CO2  

The hydration reaction (1.11), coupled with the first dissociation of carbonic acid (1.9), produces an apparent pK of 6.1 for bicarbonate formation. Thus, the summation of Equations (1.9) and (1.11) yields 

The ratio of HCOJ to H2CO3 at a physiological pH of 7.4 can be calculated by using the Henderson-Hasselbalch relationship  

The numerical value of a depends on the solvent and the temperature. For normal plasma at 37°C, a = 

mmol of dissolved CO2 per liter of plasma per mm Hg of CO2 pressure. Assuming that 37°C (310 K) is approximately the same as standard temperature, 25°C (298 K), and that [H2CO3] in Equation (1.16) includes both carbonic acid and dissolved CO2, the value of a can be derived from two facts  

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Chapter 9 focuses on acids and bases and their chemistry. This chapter now explains how to quickly estimate pH from hydronium ion or hydroxide ion concentrations to a reasonable degree of accuracy without the use of calculators. The non-hnearity of the pH scale is emphasized and the blood buffering system is introduced. The practical acid-base properties of many common household chemicals are discussed. 

When a person exercises, muscle contractions produce lactic acid. Moderate increases in lactic acid can be bandied by tbe blood buffers without decreasing the pH of blood. However, excessive amounts of lactic acid can overload tbe blood buffer system, resulting in a lowering of the blood pH. A condition called acidosis is diagnosed if the blood pH falls to 7.35 or lower. Assume the primary blood buffer system is the carbonate buffer system described in Exercise 45. Calculate what happens to the [H2C03]/[HC03 ] ratio in blood when the pH decreases from 7.40 to 7.35. 

When blood is taken from a patient for examination of acid-base status, the haemoglobin concentration of the blood is also measured routinely. Blood from an anaemic patient, being less well buffered than normal blood, yields a line on the Siggaard-Andersen plot with a slope nearer to - 1 than normal blood. To calculate the contribution of the anaemia, it is necessary to introduce the concept of normal buffer base . The normal buffer base of a sample of... 

Example 22 (a) Choose from Table 14.1 a conjugate acid-base pair suitable for making a buffer solution of pH 7.4 (the pH of blood), (b) Calculate the acid-base ratio required in this buffer. 

Lactic acid, QH C, is a weak organic acid present in both sour milk and buttermilk. It is also a product of carbohydrate metabolism and is found in the blood after vigorous muscular activity. A buffer is prepared by dissolving lactic acid, HLac (ffa = 1.4 X 10-4), and sodium lactate, NaC3H503, NaLac. Calculate [H+] and the pH of the buffer if it is made of... 

Although the condition is hypothetical, it can be calculated that if all of the skeletal muscles in the body degraded glycogen to lactic acid at the maximum rate and, if aU of the protons that were produced were transported into the blood, it would exceed the buffering capacity of the blood and the pH would fall dramatically (see below). This could soon result in death. Hence the inhibitory effect of protons... 

From a healthy volunteer 200 ml blood is collected. An aliquot of 8.4 ml blood is mixed with 1.4 ml ACD-buffer in polystyrol tubes and centrifuged at 1000 rpm for 15 min. The resulting platelet-rich plasma (PRP) is collected and an aliquot is taken for platelet counting. Ten milliliters of PRP are mixed with 1 ml ACD-buffer (ACD-PRP, pH 6.5) 5 ml portions of ACD-PRP are transferred to plastic tubes and centrifuged at 1600 rpm for 20 min. The resulting supernatant is decanted, and each pellet is resuspended in 500 pi Tyrode buffer C. An aliquot is taken for platelet counting to calculate the loss of platelets. The platelet suspension is then transferred to the Sepharose-packed column which... 

As in plasma, CO2 equilibration of whole blood depends on the buffer value of nonbicarbonate buffers. Thus CO2 equilibration in whole blood is dependent on hemoglobin concentration and also on pH and oxygenation status. It is possible to derive an approximate equation for whole blood CO2 equilibration and calculation of whole blood base excess as follows ... 

This equation for whole blood base excess (Icnown as the Van Slyke equation ), together with the Henderson-Hasselbalch equation, provides the simplest algorithm for calculation of the various acid-base variables. The buffer... 

The pH of blood plasma is 7.40. Assuming the principal buffer system is HC0 /H2C03, calculate the ratio [HC0J]/[H2C03]. Is this buffer more effective against an added acid or an added base ... 

The red blood cells of a guinea pig were found to migrate 38 mm in 86.5 minutes when placed in a 0.15 phosphate buffer. A current of 12 ma was used. Calculate the mobility and the heat evolved. The cell was 1.0 cm in diameter and had a constant of 18.9 cm and resistance of 8140 ohms when the buffer was in the cell. 

Sultatos (2002). For fenitrothion, equilibrium was achieved by 60 min and was clearly stable during 120 min of dialysis (37 C). Based on these results, it was feasible to experimentally determine both tissue blood and tissue buffer partitioning and calculate a Uver blood PC. Poulin and Krishnan (1995, 1996) also developed an algorithm-based approach for determining PCs using the chemical s octanobwater partitioning and the tissue lipid content. This approach was utilized to calculate PCs for chlorpyrifos, diazinon, and their oxen metabolites, and these are presented in Table 2. 

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