Blood electrolyte analysis

The relative simplicity of the sensor setup allows them to be implemented into portable automated devices or bed-side analyzers (Fig. 4.2), which are easily installed at patient beds, eliminating the time-consuming laboratory analyses. On the other hand, modem high throughput clinical analyzers may process more than 1000 samples per hour and simultaneously determine dozens of analytes, using a handful of analytical methods. Blood electrolyte analysis, however, remains one of the most important in... 

R.W. Burnett, A.K. Covington, N. Fogh-Andersen, W.R. Kulpmann, A. Lewenstam, A.H.J. Maas, O. Muller-Plathe, A.L. Vankessel, and W.G. Zijlstra, Use of ion-selective electrodes for blood-electrolyte analysis. Recommendations for nomenclature, definitions and conventions. Clin. Chem. Lab. Med. 38, 363-370 (2000). 

The properties of a pH electrode are characterized by parameters like linear response slope, response time, sensitivity, selectivity, reproducibility/accuracy, stability and biocompatibility. Most of these properties are related to each other, and an optimization process of sensor properties often leads to a compromised result. For the development of pH sensors for in-vivo measurements or implantable applications, both reproducibility and biocompatibility are crucial. Recommendations about using ion-selective electrodes for blood electrolyte analysis have been made by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) [37], IUPAC working party on pH has published IUPAC s recommendations on the definition, standards, and procedures... 

Carbon dioxide devices were originally developed by Severinghaus and Bradley (59) to measure the partial pressure of carbon dioxide in blood. This electrode, still in use today (in various automated systems for blood gas analysis), consists of an ordinary glass pH electrode covered by a carbon dioxide membrane, usually silicone, with an electrolyte (sodium bicarbonate-sodium chloride) solution entrapped between them (Figure 6-17). When carbon dioxide from the outer sample diffuses through the semipermeable membrane, it lowers the pH of the inner solution ... 

Background current, 21, 65 Background subtraction, 40, 106 Bacteria electrode, 182 Band microelectrodes, 130, 135 Beryllium, 82 Bienzyme electrodes, 175 Biocatalytic devices, 172 Biological recognition, 171 Biosensors, 50, 171 Bipotentiostat, 106 Blood electrolyte, 165 Boltzmann equation, 19 Brain analysis, 40, 116 Butler-Volmer equation, 14... 

Frequent serum electrolyte analysis is essential during therapy with the high-ceiling diuretics. Overdose may result in a rapid reduction of blood volume, dizziness, headache, orthostatic hypotension, hyponatremia, and hypokalemia. Nausea, vomiting, diarrhea, and loss of appetite are especially common with ethacrynic acid. 

Frequently monitor both ethylene glycol levels and acid-base balance, as determined by serum electrolyte (anion gap) or arterial blood gas analysis... 

Continuous hemodynamic monitoring is essential during all phases of hypothermia. Cardiac monitoring is necessary because of the increased risk of arrhythmias. Cardiac output is decreased 5% for every 1°C of body temperature reduction. This is thought to be secondary to bradycardia, which has been shown to occur with hypothermia (3). A pulmonary artery catheter may be placed if there is any question of hemodynamic instability. Arterial catheters are used for continuous blood pressure measurement, as well as for access to arterial blood for blood gas and electrolyte analysis. 

Mollard J-E Single phase calibration for blood gas and electrolyte analysis. In D Orazio P, ed. Preparing for critical care analyses in the 2P century. Proceedings of the 16 International Symposium. Washington AACC Press, 1996. 

Table 24.1 summarizes the normal range of concentrations of some clinically important constituents in human blood. We should emphasize that these normal ranges are approximations. Table 5.3 summarizes the major electrolyte composition (cations and anions) in blood. The analysis of some of the more commonly determined constituents will be discussed below. The physiological significance of the results is also discussed. 

The next diagnostic steps usually include arterial gas analysis, blood electrolytes (including anion gap), serum lactate (if there is doubt about the cause of the acidemia), complete blood cell count, biochemical assessment of liver and renal fnnction, blood and nrine cnltures, myocardial biomarkers (if there is suspicion of a myocardial infarction), ECG and chest X-ray. In this context it is advantageons that most modem gas analysers also readily provide potassinm concentrations. Another recent advantage is the advent of bedside ketone body monitors. It is thus nowadays possible to have... 

In a study in 73 healthy subjects, celecoxib 400 mg was given daily for 2 weeks, then selenium enriched baker s yeast (Saccharomyces cerevi-siae) 200 micrograms daily or matched placebo were added for 30 days. Following blood chemistry analysis (urea and electrolytes, full blood count etc), there were no clinically significant changes from baseline, nor were there any changes in celecoxib steady-state plasma levels. ... 

Pearl Jones was admitted to the intensive-care unit alter a car accident with approximately 3 L of blood loss three days ago. She is semiconscious but irritable and has a blood pressure (BP) of 92/40 mm Hg, pulse (P) of 140 beats/minute, and respiration (R) of 38 breaths/minute, and her skin is cool and pale with pale mucous membranes. Arterial blood-gas analysis reveals a pH of 7.32, Pco of 33 mm Hg, of 70 percent, and HCO3 of 14 mEq/L. Urine output is 200 mL for the past 24 hours. Diagnostic tests ordered include an electrolyte panel (Na% K, CP, and CO ). What additional data would be beneficial to determine care measures for Ms. Jones ... 

A different concept based on amperometry was described by Fasching et al. [45], They have developed a miniaturized amperometric sensor for CO2 in liquids for applications in clinical blood gas analysis. The detection principle is based on the pH-dependent dissociation of copper complexes. Different CO2 concentrations result in corresponding pH shifts of the internal hydrogel electrolyte. These pH variations lead to certain dissociation levels of the copper complexes... 

Clinical Applications Perhaps the area in which ion-selective electrodes receive the widest use is in clinical analysis, where their selectivity for the analyte in a complex matrix provides a significant advantage over many other analytical methods. The most common analytes are electrolytes, such as Na+, K+, Ca +, H+, and Ch, and dissolved gases, such as CO2. For extracellular fluids, such as blood and urine, the analysis can be made in vitro with conventional electrodes, provided that sufficient sample is available. Some clinical analyzers place a series of ion-selective electrodes in a flow... 

Clinical chemistry, particularly the determination of the biologically relevant electrolytes in physiological fluids, remains the key area of ISEs application [15], as billions of routine measurements with ISEs are performed each year all over the world [16], The concentration ranges for the most important physiological ions detectable in blood fluids with polymeric ISEs are shown in Table 4.1. Sensors for pH and for ionized calcium, potassium and sodium are approved by the International Federation of Clinical Chemistry (IFCC) and implemented into commercially available clinical analyzers [17], Moreover, magnesium, lithium, and chloride ions are also widely detected by corresponding ISEs in blood liquids, urine, hemodialysis solutions, and elsewhere. Sensors for the determination of physiologically relevant polyions (heparin and protamine), dissolved carbon dioxide, phosphates, and other blood analytes, intensively studied over the years, are on their way to replace less reliable and/or awkward analytical procedures for blood analysis (see below). 

Stool analysis studies include examination for microorganisms, blood, mucus, fat, osmolality, pH, electrolyte and mineral concentration, and cultures. 

---