Extracellular fluid volume, significance

Occurs when the volume of extracellular fluid is significantly diminished. Examples include hemorrhage, fluid loss caused by burns, diarrhea, vomiting, or excess diuresis Occurs when the heart is unable to deliver an adequate cardiac output to maintain perfusion to the vital organs. Examples include as the result of an acute myocardial infarction, ventricular arrhythmias, congestive heart failure (CHF), or severe cardiomyopathy. 

Large doses of mannitol used in treating cerebral edema can alter extracellular fluid volume, osmolality, and composition and can lead under some circumstances to acute renal insufficiency, cardiac decompensation, and other complications (1). The patient s body habitus, age, total body water content relative to body weight, pretreatment plasma sodium concentration and plasma osmolality, and the presence of edema or ascites can influence the degree of extracellular fluid change and the rate of mannitol excretion to a significant degree. 

Ca2+) from EDTA in accordance with its 107-fold greater affinity for the chelate. Free lead ions are removed from the blood and tissues (directly from bone and indirectly from parenchymatous organs) as the soluble lead chelate formed is rapidly excreted by glomerular filtration. Because of its ionic character, it is unlikely that CaNa2EDTA significantly penetrates cells the apparent volume of distribution is numerically similar to the extracellular fluid volume. 

A major use of loop diuretics is in the treatment of acute pulmonary edema. A rapid increase in venous capacitance in conjunction with a brisk natriuresis reduces left ventricular filling pressures and thereby rapidly relieves pulmonary edema. Loop diuretics are also used widely for the treatment of chronic CHE when diminution of extracellular fluid volume is desirable to minimize venous and pulmonary congestion. In this regard, a metaanalysis of randomized clinical trials demonstrates that diuretics cause a significant reduction in mortality and the risk of worsening heart failure, as well as an improvement. 

The sodium ion concentrations in body fluids are listed in Table 1 [2]. From a physiological viewpoint, Na provides the bulk of osmotically active solutes in plasma with its associated anions, thus affecting the distribution of the body water significantly. An excess translocation of Na into cells or a loss of it from the body results in a decrease of extracellular fluid volume, affecting circulation, renal function, and nervous system function. 

Plasma volume and the extracellular fluid space have been observed to constrict 30% during reducing diets (300-600 calories per day) (B22). These changes can be accompanied by functional impairment of glomerular filtration and hepatic perfusion with transient increases up to 2 mg/100 ml in serum creatinine and BSP retention up to 40% (B22). In rare instances a significant fall in serum calcium, magnesium, or potassium was observed. Hyperuricemia was also observed, with concentrations as high as 9 mg/100 ml (B22). 

The molecular mechanism of diuretics acting as antihypertensive agents is not completely clear however, use of diuretics causes a significant increase in the amount of water and electrolytes excreted in urine, which leads to a reduction in the volume of extracellular fluid and plasma. This in turn leads to a reduction of cardiac output, which is the main parameter responsible for a drop in arterial blood pressure and venous blood return. Cardiac output is gradually restored, but the hypotensive effect remains, possibly because of the reduced peripheral resistance of vessels. It is also possible that diuretics somehow lower vascular activity of noradrenaline and other factors of pressure in the organism. Methods of synthesizing thiazide diuretics used for hypertension are described in the preceding chapter. Chapter 21. 

Attempts at treatment through head-out water immersion (M. Epstein et al., 1976) can be deemed relatively effective and, above all, low in risk, provided this is feasible with a seriously ill patient. This simple method increases the central blood volume (= redirecting extracellular fluid to the vascular system). There is a significant rise in the volume of the urine and in natriuresis -although one must also reckon with a number of nonresponders when applying this method. 

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