Electrolytes, blood/plasma/serum

The blood plasma is an aqueous solution of electrolytes, nutrients, metabolites, proteins, vitamins, trace elements, and signaling substances. The fluid phase of coagulated blood is known as blood serum. It differs from the plasma in that it lacks fibrin and other coagulation proteins (see p. 290). 

Instruments are offered in the market for clinical determination of electrolytes in blood, plasma or serum. One of them, for example, carries out simultaneous determinations of Na, K, Ca, Mg, hematocrit and pH. The cations are of the free type (see Section m.A) and are measured with specific ion-selective electrodes. In complex matrices such as blood or its derived fractions the concentration of free Ca and Mg is affected by the pH of the solution, for example, a slight change of pH will produce or neutralize anionic sites in the proteins, binding or releasing these cations furthermore, the response of the Mg-selective electrode is also affected by the concentration of free Ca(II). The correction... 

Changes in biochemical composition of CSF could serve as a useful tool for investigations of pathological processes in the CNS. CSF is also in contact wdth the blood plasma through the blood-brain barrier, thus resembling an ultrafiltrate of plasma in its protein constituents. CSF contains sugars, lipids, electrolytes and proteins. Protein concentration in CSF ranges from 0.2mg/ml to 0.8mg/ml (0.3 - 1% of serum protein concentration) wdth more than 70% of the proteins in CSF... 

Five patients with low-renin essential hypertension, well-controlled for 4 months or more with spironolaetone 100 to 300 mg daily, took part in a crossover study. Aspirin 2.4 to 4.8 g daily given over 6-week periods had no effect on blood pressure, serum electrolytes, body-weight, blood-urea-nitrogen or plasma renin activity. ... 

No standard reference material and procedure is actually available for molal ion activity assays. Calibration of the electrode is required. The calibration solution should match the mean sample composition as closely as possible. Addition of albumin to the calibration standard does not guarantee high accuracy of the results due to a shift of the assay standard potential that is different for plasma, serum, and albumin. Reports on comparisons of clinical analyzers show that interinstrumental deviations may be considerable. Recommendations for calibration and standardization by the IFCC Committee on Electrolytes and Blood Gases are in preparation. 

The patients, whether on Allopurinol or placebo, received identical-looking tablets. The study was not a double-blind one, as the doctors who were following the patients knew the group to which eveiy patient belonged. No special dietary restrictions were imposed on the patients. The patients were seen at least once a month. Each time, in addition to body weight and blood pressure, blood was drawn for plasma uric acid, electrolytes, and plasma urea. The patients collected, for every monthly visit, a 24-hour urine collection for creatinine clearance. Once every three months, maximal urine osmolality was determined, and blood drawn for determination of plasma cholesterol, glucose, Hb., serum iron, total iron binding capacity, in addition to the other monthly determined parameters. 

The extracellular fluid (ECF) is the fluid outside the cell and is rich in sodium, chloride, and bicarbonate. O The ECF is approximately one-third of TBW (14 L in a 70-kg man or 12 Lin a 70-kg woman) and is subdivided into two compartments the interstitial fluid and the intravascular fluid. The interstitial fluid (also known as lymphatic fluid) represents the fluid occupying the spaces between cells, and is about 25% of TBW (10.5 L in a 70-kg man or 8.8 L in a 70-kg woman). The intravascular fluid (also known as plasma) represents the fluid within the blood vessels and is about 8% of TBW (3.4 L in a 70-kg man or 2.8 L in a 70-kg woman). The ECF is approximately one-third of TBW or 14 L in a 70-kg male. Because the exact percentages are cumbersome to recall, many clinicians accept that the ECF represents roughly 20% of body weight (regardless of gender) with 15% in the interstitial space and 5% in the intravascular space.6 Note that serum electrolytes are routinely measured from the ECF. 

PLASMA. The portion of the blood remaining after removal of the white and red cells and the platelets it differs from serum in that it contains fibrinogen, which induces clotting by conversion into fibrin by activity of the enzyme thrombin. Plasma is made up of more than 40 proteins and also contains acids, lipids, and metal ions. It is an amber, opalescent solution in which the proteins are in colloidal suspension and the solutes (electrolytes and nonelectrolytes) are either emulsified or in true solution. The proteins can be separated from each other and from the other solutes by nltrafiltration, nltracentrifugation, electrophoresis, and immuno-chemical techniques. See also Blood. 

The method was designed for the determination of ionized (free) magnesium (iMg2"1") together with other major electrolytes (Na+, K+, Cl and Ca2+) and pH in blood serum, plasma or whole blood in the environment of the commercially available Microlyte 6 analyzer supplied by Thermo Fisher Scientific, Finland (previously KONE Instruments, Finland) [1-3]. 

Dofetilide is 100% bioavailable. Verapamil increases peak plasma dofetilide concentration by increasing intestinal blood flow. Eighty percent of an oral dose is eliminated by the kidneys unchanged the remainder is eliminated by the kidneys as inactive metabolites. Inhibitors of the renal cation secretion mechanism, eg, cimetidine, prolong the half-life of dofetilide. Since the QT-prolonging effects and risks of ventricular proarrhythmia are directly related to plasma concentration, dofetilide dose must be based on the estimated creatinine clearance. Treatment with dofetilide should be initiated in hospital after baseline measurement of the QTc and serum electrolytes. A baseline QTC of > 450 ms (500 ms in the presence of an intraventricular conduction delay), bradycardia of < 50 beats/min, and hypokalemia are relative contraindications to its use. 

Whole blood consists of water, cells, proteins, and electrolytes (Figure 3.15). Cells comprise approximately 45% of total blood volume. The noncellular components of blood are called plasma. Plasma is mostly water with some proteins (8% by weight). Plasma proteins may be divided into three categories serum albumin (60%) the a-, j8-, and -y-globuhns (36%) and fibrinogens (4%). Blood serum is the residual liquid left behind after whole blood is allowed to clot.5... 

Several relatively common disorders result in aldosterone secretion abnormalities and aberrations of electrolyte status. In Addison s disease, the adrenal cortex is often destroyed through autoimmune processes. One of the effects is a lack of aldosterone secretion and decreased Na+ retention by the patient. In a typical Addison s disease patient, serum [Na+] and [CL] are 128 and 96 meq/L, respectively (see Table 16.2 for normal values). Potassium levels are elevated, 6 meq/L or higher, because the Na+ reabsorption system of the kidney, which is under aldosterone control, moves K+ into the urine just as it moves Na+ back into plasma. Thus, if more Na+ is excreted, more K+ is reabsorbed. Bicarbonate remains relatively normal. The opposite situation prevails in Cushing s disease, however, in which an overproduction of adrenocorticosteroids, especially cortisol, is present. Glucocorticoids have mild mineralocorticoid activities, but ACTH also increases aldosterone secretion. This may be caused by an oversecretion of ACTH by a tumor or by adrenal hyperplasia or tumors. Serum sodium in Cushing s disease is slightly elevated, [K+] is below normal (hypokalemia), and metabolic alkalosis is present. The patient is usually hypertensive. A more severe electrolyte abnormality is seen in Conn s syndrome or primary aldosteronism, usually caused by an adrenal tumor. Increased blood aldosterone levels result in the urinary loss of K+ and H+, retention of Na+ (hypernatremia), alkalosis, and profound hypertension. 

Potentiometry is widely used clmicaUy for the measurement of pH, PCO2 and electrolytes (Nah K, CL, Ca h LP) in whole blood, serum, plasma and urine, and as the basis for some biosensors for metabolites of clinical interest. 

Serum, heparinized plasma, whole blood, sweat, urine, feces, or gastrointestinal fluids may be assayed for Nah Timed collections of urine, feces, or gastrointestinal fluids are preferred to allow comparison of values with reference intervals and to determine rates of electrolyte loss. Serum, plasma, and urine may be stored at 2 C to 4 C or frozen. Erythrocytes contain only one tenth of the Na" present in plasma, so hemolysis does not cause significant errors in serum or plasma Na values. Lipemic samples should be ultracen-trifuged and the infranatant analyzed unless a direct ISE is used. 

Abnormalities of acid-base status of the blood are always accompanied by characteristic changes in electrolyte concentrations in the plasma, especially in metabolic acid-base disorders. Hydrogen ions cannot accumulate without concomitant accumulation of anions, such as CL or lactate, or without exchange for cations, such as or NaL Consequently, electrolyte composition of blood serum or plasma is often determined along with measurements of blood gases and pH and to assess acid-base disturbances. 

Neat VX, 20 ig kg-1, was applied to the skin of four subjects, while four other subjects received 20 p.g kg-1 mixed 1 1 with octylamine, and four others received neat VX, 35 pg kg-1 (Lubash and Clark, 1960). Seven were symptomatic with insomnia, nightmares, lightheadedness, nausea, epigastric discomfort, vomiting and diarrhea. (The whole blood activity was 14-38% of control in these subjects.) The whole blood erythrocyte activity was above 42% of control activity in the five asymptomatic subjects. Plasma and urinary electrolytes, BSP excretion, SGOT, SGPT and serum amylase were all normal following exposure. 

Blood glucose should be monitored hourly at the bedside until less than 1.5 mmol/l. Thereafter checks may continue 2-hourly. The plasma glucose should be confirmed in the laboratory every 2-4 hours. The frequency of monitoring of blood gases depends on the severity of DKA. In severe cases it should be performed 2-hourly at least for the first 4 hours. The serum potassium level should be checked every 2 hours for the first 6 hours, while urea and electrolytes should be measured at4-hourly intervals (Fig. 3). 

Since the early days of analytical applications of ion-selective electrodes they have been used in clinical analysis. The progress in construction and miniaturisation of electrodes as well as contemporary development of computerised potentiometric apparatus have led to the production of automatic analyzers designed especially for clinical applications/ The high degree of response selectivity of the membrane sensors used today eliminates practically the mutual interaction of various blood, serum, plasma or urine components. Nevertheless when drugs or their metabolites are introduced into the body they in some cases may influence the electrode response and cause errors in estimation of the content of the ions present naturally, i.e., potassium, sodium, calcium and chloride. Such parasitic effects may be caused by the interaction of drugs with the electrode membrane. The aim of this study was to check whether some selected drugs can influence the determination of the above mentioned electrolyte ions in the serum. 

The interpretation of measured pH values becomes more vague in higher ionic strength electrolytes (above 0.1 mol/kg). Such is the case, for example, with blood, serum, and plasma measurements, and this situation calls for the use of a special operational standard [1]. 

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