Plasma total carbon dioxide

Methods for Determination of Serum or Plasma Total Carbon Dioxide... 

The question often arises whether a sample must be analyzed immediately or can be stored, and if so, under what conditions and for how long (B4a, H5a, W9a). Freshly drawn blood maintained anaerobically (A3) at 38 C decreases in pH at the rate of —0.062 unit per hour and in pCOj, at 4.8 1.3 mg Hg per hour. At 0-4°C, the change is minimal — 0.006 0.004 pH unit and 0.6 0.06 mm Hg. There has been controversy concerning the use of minerol oil to maintain specimens for carbon dioxide analysis (G2). Paulsen found that values of total carbon dioxide in plasma collected in stoppered tubes with and without paraflSn oil were identical if the tubes without oil were completely filled to the stopper (P4). The loss of carbon dioxide in tubes stored at room temperature without oil was about 6 mEq/1 in 2.5-4 hours. The problem for the laboratory is unfilled tubes and the storage of separated serum or plasma before analysis and in plastic cups during continuous-flow procedures. 

Total carbon dioxide is used here to describe the quantity that is measured most often in automated analyzers by acidification of a serum or plasma sample and measurement of the carbon dioxide released by the process, or by alkaliniza-tion and measurement of total bicarbonate. Under certain conditions of collection and specimen handling, total carbon dioxide values determined in this manner may be almost identical with values for the calculated concentration of total carbon dioxide obtained in blood gas analysis (see later section in this chapter on blood gas methods). The patho-... 

Total carbon dioxide (CO2) content of plasma consists of carbon dioxide dissolved in an aqueous solution (dCOa), CO2 loosely bound to amine groups in proteins (carbamino compounds), HCO3 and vanishingly small amounts of CO ions, and carbonic acid (H2CO3). Bicarbonate ions make up ail but 2 mmol/L of the total carbon dioxide of plasma (22 to 31 mmol/L). Measurement of the tota CO2 as part of an electrolyte profile is useful chiefly to evaluate HCO3 concentration in assessment of acid-base disorders. 

R2. Rechnitz, G. A., Nogle, G. J., Bellinger, M. R., and Lees, H., Determination of total carbon dioxide in serum and plasma using a carbonate ion-selective membrane electrode. Clin. Chim. Acta 76, 295-307 (1977). 

The classical manifold architecture in Fig. 8.22, upper was exploited in the pioneering work incorporating GD in flow injection analysis for the spectrophotometric determination of total carbon dioxide in blood plasma [265]. Details of the separation unit are shown in Fig. 8.23, left. The donor stream with the sample zone was acidified and the released CO2 diffused through the membrane towards the acceptor stream, which was an alkaline cresol-red indicator solution. Analyte collection resulted in a transient lowering of the pfi of this stream and hence a transient modification to the monitored absorbance. The recorded peak height was proportional to the CO2 content in the injectate. 

It must be ascertained that serum was obtained from blood that was processed anaerobically during sampling and centrifuging. Total carbon dioxide comprises dissolved CO2 (3%), hydrogen carbonate (64%), and carbamino derivatives of plasma proteins (33%). Hydrogen carbonate is increased in metabolic alkalosis and decreased in acute and chronic acidosis. Hydrogen carbonate concentration (Table 1) is needed for the calculation of the anion gap (see Chloride above). 

IFCC reference measurement procedure for the substance concentration determination of total carbon dioxide in blood, plasma or serum. Clinical Chemistry and Laboratory Medicine 39 283-289. 

Plasma. Normal blood plasma is a clear, slightly yellowish fluid, which is approximately 55% of the total volume of the blood. The plasma is a water solution in which are transported the digested food materials from rhe walls of the small intestine to the body tissues, as well as the waste materials from the tissues to the kidneys. Consequently, this solution contains several hundred different substances. In addition, the plasma carries antibodies, which are responsible for immunity to disease, and hormones. The plasma transports most of the waste carbon dioxide from the tissues back to the lungs. Plasma consists of about 91% water, 7% piotein material, and 0.9% various mineial salts, The icmaindei consists of substances already mentioned. The salts and proteins are important in keeping the proper balance between the water in the tissues and in the blood, Disturbances in this ratio may result in excessive water in the tissues (swelling or edema). The mineral salts in the plasma all serve... 

The course of carbon-14-radioactivity derived from oral (l- C)ascorbic acid in plasma and several tissues was studied in male guinea pigs up to 320 h after intake. The excretion of label was followed in respiratory carbon dioxide, urine, and feces. The evaluation by pharmacokinetic principles yielded an overall half-life of 61 h and a body pool of 21 mg with a total turnover of about 10 mg/d. The total turnover of ascorbate is lower than the daily intake (16 mg/d), indicating incomplete absorption. Ascorbic acid seemed to be bound in several tissues (adrenals, testes) to a higher percentage than in plasma. The maximum rate of excretion as carbon dioxide occurred at 0.5 h, whereas peak concentration of radioactivity in plasma was reached at 1.5 h. Therefore, presystemic metabolism must be considered. 

Plasma The fluid component of blood that consists of 55% of total blood volume is comprised mostly of water and a small percentage of solutes. Solutes are glucose, protein, lipids, amino acids, electrolytes, minerals, lactic and pyruvic acids, hormones, enzymes, oxygen, and carbon dioxide. 

Carbon dioxide, total mmol/L 10 40 Serum or plasma... 

Numerous methods and data have been published for the collection of blood from rats and mice (Riley 1960 Upton and Morgan 1975 Cardy and Warner 1979 Eowler, Brown, and Elower 1980 Archer and Riley 1981 Cochetto and Bjornsson 1983 Neptun, Smith, and Irons 1985 Suber and Kodell 1985 Conybeare et al. 1988 Dameron et al. 1992 Itumi et al. 1993 Matsuzawa et al. 1994 Bernard et al. 1996 Walter 1999 Mahl et al. 2000 Nahas et al. 2000 Schnell et al. 2002). Values obtained from major blood vessels or cardiac puncture are less variable than those samples taken from the tail or retro-orbital plexus this may be in part due to contamination with tissue fluid. Potassium, total protein, and several enzymes are higher in samples collected from the tail or the retro-orbital plexus. The use of carbon dioxide and, to a lesser extent, halothane increases plasma levels of glucose, potassium, and inorganic phosphate. 

Non-Thermal Plasma Synthesis of Formic Acid in CO2-H2O Mixture. Determine the minimum energy efficiency of the plasma-chemical HCOOH synthesis in the CO2-H2O mixture (9-60) required for effective hydrogen production in the double-step cycle (9-60) and (9-61). Assume that thermodynamically about 70% of the total energy required for hydrogen production from water should be consumed in this case for decomposition of formic acid (9-61) to form hydrogen and to recycle carbon dioxide back to the plasma process. 

Human blood is a very complex fluid which contains about 0.04% P and has a pH of about 7.4. It acts as a transport medium for oxygen and carbon dioxide, food, waste products, enzymes hormones etc. An average 70 kg man contains 5.2 L which constitutes 6-8% of the total body weight. This can be separated into blood cells (red + white + platelets) and plasma, by centrifuging (Figure 11.4). The average lifetime of a human red blood cell is -120 days (Table 11.6). 

This bicarbonate buffer system is quantitatively the most important of the three because of the high bicarbonate concentration in blood which results from the large amounts of CO2 produced by the metabolic activity of cells. Loss of CO2 in the lungs displaces the equation to the left once more and prevents build up of hydrogen ions. The p/sT value of this system is considerably below pH 7-4, the normal physiological value for blood, and can be evaluated by applying the Henderson-Hasselbalch equation. The normal plasma bicarbonate value is 27 m-equiv per litre, approximately twenty times the total solubility of carbon dioxide of 1-35 mmol per litre (at a partial pressure of 40mmHg) From Equation (3-11)... 

The difference between the rate of loss of the two isotopes from body water (plasma, saliva or urine) thus reflects the total amount of carbon dioxide that has been produced ... 

Methods in which bicarbonate is liberated as carbon dioxide. When plasma is treated with acid, carbon dioxide is liberated. This carbon dioxide is derived from dissolved CO2, carbonic acid, and bicarbonate (see above equation) and is known as total CO2. The CO2 liberated can be measured by one of several different techniques ... 

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