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Query: HUMANGGP:003739 (CO2)
 48,959 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

I report further experience in measuring ionized calcium (Ca2+) with the AMT Electron System and its serum standards and solid-state, dip, calcium-selective electrodes. With this system, serum pH can be adjusted with CO2 gas and Ca2+ and pH simultaneously measured; when 5.2% CO2 (40 mm pco2) is used for sample equilibration, the standard bicarbonate concentration is also provided. I measured serum Ca2+ as a function of pH between pH 7.0 and 9.0 and found the relationship to be reproducible, with no evidence of irreversible complexing of Ca2+. When the pH of aerobically exposed, mailed sera was restored to the original values, their values for Ca2+ were the same as for the fresh sera. Measurement of Ca2+ in routinely (aerobically) handled sera after pH restoration with CO2 gas was therefore validated, both samples from within an institution and mailed specimens. Standardization to pH 7.40 is recommended for routine measurements, is generally more accurate than use of heparin or quasianaerobic techniques, and is a practical approach. In patients with possible uncompensated acid-base disturbance (which may be indicated by an abnormal standard bicarbonate concentration if not suspected clinically), patient pH should be measured independently as part of the usual strict, anaerobic blood-gas-analysis procedures. Abnormal patient pH must be considered in the interpretation of Ca2+ results determined at pH 7.40 which are borderline or slightly abnormal; most accurately, Ca2+ may be measured in the separated sera at the previously determined patient pH value. Studies of aqueous solutions with the currently used Ca2+ electrodes showed a selectivity coefficient (the constant which relates the activity of an interfering ion to the activity of calcium that would contribute the same emf) KNa=0.0031 +/- 0.0003 (SE) and KMg=0.046 +/- 0.004 (SE). At physiological concentrations of Ca2+, physiologically encountered variation in Na+ is of no significance in resulting Ca2+, but extreme variation in Mg2+ may cause an error of approximately 1%.
Clin Chem 1976 Apr
PMID:New techniques for ion-selective measurements of ionized calcium in serum after pH adjustment of aerobically handled sera. 0 97

Several hypotheses have been put forward to explain postdialysis hypocapnia. Three were tested in this study: impairment of tissue oxygenation by dialysis (D)-induced alkalosis (Bohr effect), the D disequilibrium syndrome, and the loss of carbon dioxide (CO2) in D fluid. In 17 patients pre-DPCO2 was significantly correlated with plasma bicarbonate concentration (HCO3) and no disproportionate reduction of PCO2 was discernible. In 10 patients using a bath acetate concentration of 38 mEq/1 PCO2 was unchanged after D (35.4 versus 35.9 mm Hg before D), and was low relative to HCO3 whic increased from 21.2 to 28.0 mEq/1. After a dialysis using an acetate concentration of 25 mEq/1 HCO3 remained constant (20.4 versus 21.1 mEq/1 pre-D), whereas PCO2 fell from 35.3 to 30.8 mm Hg (P less than 0.001). Consequently PCO2 was again low relative to HCO3. Removal of CO2 by D fluid was excluded as a cause for low blood PCO2: addition of gaseous CO2 to the bath had no influence on arterial blood gases. Since post-D hypocapnia was not prevented when HCO3 was kept constant, it was concluded that post-D alkalosis cannot be the main reason for post-D hyperventilation, and that other factors related to the process of D are responsible.
Clin Nephrol 1976 Mar
PMID:Mechanism of post dialysis hyperventilation in patients with chronic renal insufficiency. 0 52

We examined changes in ionized calcium concentration in serum after its exposure to air. Samples with total protein concentrations ranging from 50 to 90 g/liter were equilibrated with CO2 in nitrogen (5/95, by vol) or CO2 alone, to produce pH values of 7.0 to 8.0. Ionized calcium was then measured with an Orion flow-through electrode system. Curves relating pH and ionized calcium concentration had statistically identical slopes regardless of protein concentration. A factor was derived, based on pH change, for correcting values for ionized calcium in serum exposed to air, and its validity was confirmed by comparing corrected values for samples allowed to stand at ambient temperature (23 degrees C) without anaerobic precautions with values initially obtained on anaerobic aliquots of the same samples.
Clin Chem 1976 Jul
PMID:Determination of ionized calcium in serum that has been exposed to air. 0 66

It is generally believed that the reduction in plasma [HCO3] characteristic of chronic hypocapnia results from renal homeostatic mechanisms designed to minimize the alkalemia produced by.the hypocapneic state. To test this hypothesis, we have induced chronic hypocapnia in dogs in which plasma [HCO3] had previously been markedly reduced (from 21 to 15 meq/liter) by the prolonged feeding of HCl. The PaCO2 of chronically acid-fed animals was reduced from 32 to 15 mm Hg by placing the animials in a large environmental chamber containing 9% oxygen. In response to this reduction in PaCO2, mean plasma [HCO3] fell by 8.6 meq/liter, reaching a new steady-state level of 6.4 meq/liter. This decrement in plasma [HCO3] is almost identical to the 8.1 meq/liter decrement previously observed in normal (nonacid-fed) animals in which the same degree of chronic hypocapnia had been induced. Thus, in both normal and HCl-fed animals, the renal response to chronic hypocapnia causes plasma [HCO3] to fall by approximately 0.5 meq/liter for each millimeter of Hg reduction in CO2 tension. By contrast, the response of plasma [H+] in the two groups was markedly different. Instead of the fall in [H+] which is seen during chronic hypocapnia in normal animals, [H+] in HCl-fed animals rose significantly from 53 to 59 neq/liter (pH 7.28-7.23). This seemingly paradoxical response is, of course, an expression of the constraints imposed by the Henderson equation and reflects the fact that the percent fall in [HCO3] in the HCl-fed animals was greater than the percent fall in PaCO2. These findings clearly indicate that in chronic hypocapnia the kidney cannot be regarded as the effector limb in a homeostatic feedback system geared to the defense of systemic acidity.
J Clin Invest 1976 Jun
PMID:Regulation of acid-base equilibrium in chronic hypocapnia. Evidence that the response of the kidney is not geared to the defense of extracellular (H+). 0 88

Five male subjects with essential hypertension received chlorthalidone at each of four dose levels (25, 50, 100, and 200 mg/day) for eight week periods each preceded by an eight week placebo period. Dosage order was randomized and double-blind. During the last week of each active and placebo period an upright bicycle exercise study was carried out at three loads (100, 200, 300 kpm/min) for 6 min each. Oxygen consumption at the maximal workload was 42% of predicted at a heart rate of 170. During placebo therapy, increasing workloads were associated with a progressive increase in blood pressure, heart rate, and pressure-rate index (systolic pressure times heart rate). With increasing doses of chlorthalidone up to 100 mg/day, there was a progressive reduction in blood pressure and pressure-rate index. At 200 mg/day there were paradoxical increases in diastolic pressures, heart rates and pressure-rate indices above values observed at 100 mg/day. With increasing doses of chlorthalidone, there was a progressive increase in arterial blood CO2 content and pH. Increasing workloads were associated with increased arterial blood lactate and decreased arterial blood lactate and decreased arterial blood pH. The changes in lactate and pH were not different at the different dose levels. The best antihypertensive effect in these exercising subjects was observed at a daily dose of 100 mg of chlorthalidone. The exercise response was useful in the determination of potentially adverse hemodynamic consequences of the larger dose of chlorthalidone.
Eur J Clin Pharmacol 1976 Mar 22
PMID:Cardiovascular response to exercise under increasing doses of chlorthalidone. 0 91

By measuring the colony size of a variety of anaerobic bacteria isolated from clinical specimens, an evaluation was made of the benefits derived from the addition of several enrichments to blood agar medium commonly used for the growth of anaerobes. Similar methods were used to study the effects of various storage conditions and age of the medium. The results were compared with those obtained on freshly prepared and enriched blood agar plates as well as commercially available blood agar plates. Freshly prepared and enriched blood agar was found to give substantially larger colonies than could be grown on commercially obtained blood agar plates when both were inoculated and incubated under identical conditions. Storage of plating media under CO2 for periods of up to 72 h had only a minor effect on the growth of the anaerobic bacteria studied, but longer periods of storage under CO2 resulted in a less efficient plating medium. Nonenriched brain heart infusion (BHI) was found to be a better basal medium than Trypticase soy agar (TSA) medium. Colony size on fully enriched BHI blood agar plates was greater than nonenriched BHI greater than nonenriched TSA greater than commercially prepared nonenriched TSA plates. The data suggest that freshness of the plates may be as important as using rich media.
J Clin Microbiol 1976 Nov
PMID:Evaluation of enrichment, storage, and age of blood agar medium in relation to its ability to support growth of anaerobic bacteria. 1 Dec 26

The Henderson-Hasselbalch equation has always occupied a central place in the description of the acid-base status of the blood. An equation of similar importance is the equation for the CO2 equilibration curve of blood in vitro. It is proposed to name this the Van Slyke equation: a - 24.4 = - (2.3 X b + 7.7) X (c - 7.40) + d/(1 - 0.023 X b), where a = bicarbonate concentration in plasma/(mmol/l), b = hemoglobin concentration in blood/(mmol/l), c = pH of plasma at 37 degrees C, d = base excess concentration in blood/(mmol/l). These two equations provide an arithmetic algorithm for calculation of the various acid-base variables of the blood after measuring the pH, the pCO2, and the hemoglobin concentration.
Scand J Clin Lab Invest Suppl 1977
PMID:The van Slyke equation. 1 78

This paper reviews the techniques available to the clinical biochemist for measuring ionised calcium concentrations in biological fluids with particular reference to serum. At present ionised calcium may be measured colorimetrically, using tetramethyl murexide, or potentiometrically, using a calcium ion-selective electrode. These techniques compare favourably in terms of precision with existing methods for measuring total calcium. Advantages of measuring ionised calcium in preference to total calcium are (a) that there is no effect of venous occlusion or change of posture on the ionised fraction of the effect on total calcium, (b) that ionised calcium is the physiologically active form of the element, and (c) that the ionised calcium concentration is a more reliable indicator of the calcium status of patients in certain clinical conditions. The main problem in the measurement of ionised calcium is the marked dependence of the ionised fraction of the pH of the sample. Extreme care must be taken to avoid loss of CO2 or build-up of acid during the handling of the blood sample.
Ann Clin Biochem 1976 Nov
PMID:Measurement of ionised calcium in body fluids-a review. 1 2

A close relationship exists between the decrease in concentration of 2,3-diphosphoglycerate (2,3-DPG) and a fall in the pH of stored blood. Buffering the stored red cells with bicarbonate is one solution to the problem of maintaining pH during storage. The effectiveness of this buffer depends upon loss from the stored blood of carbonic acid in the form of CO2. We describe a system in which the CO2 is trapped in a small internal package which contains calcium hydroxide, or calcium hydroxide embedded in Silastic. A medium containing bicarbonate, adenine, glucose, phosphate and mannitol (BAGPM) is added after initial packing of the erythrocytes. With this approach, it has been possible to maintain 2,3-DPG at 92 percent of original, and ATP was approximately 62 percent of initial levels at the end of 42 days of storage if an internal Silastic bag containing calcium was used in bags agitated once weekly. More frequent agitation (five times weekly) produced acceptable maintenance of both 2,3-DPG (78 percent of original) and ATP (44 percent of original) after 42 days of storage when a Silastic block impregnated with calcium hydroxide was utilized to absorb CO2.
J Lab Clin Med 1977 Mar
PMID:Prolonged maintenance of 2,3-DPG in liquid blood storage: use of an internal CO2 trap to stabilize pH. 1 18

A new manual method for the determination of carbon dioxide content in serum and plasma, based on the potentiometric measurement of carbonate, is proposed and evaluated. The new method offers good precision and accuracy in the physiological concentration range as shown by detailed studies on synthetic samples, reference standards, and actual patient samples. Moreover, the method yields results which correlate very well with analyses carried out using various conventional techniques. It is expected that the proposed method could be used for manual determinations of CO2 content, especially where rapid start-up time, minimal sample treatment, and low cost are of importance.
Clin Chim Acta 1977 May 02
PMID:Determination of total carbon dioxide in serum and plasma using a carbonate ion-selective membrane electrode. 1 48


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