Fluids intracellular/extracellular compartments

The major adverse reactions associated with mannitol administration are headache, nausea, vomiting, chest pain, and hyponatremia. Too rapid an administration of large amounts may cause an excessive shift of fluid from the intracellular to the extracellular compartment and result in congestive heart failure. 

OHSS is characterized by cystic ovarian enlargement, increased capillary permeability, and third space fluid accumulation (that is in an extracellular compartment that is not in equilibrium with either the extracellular or intracellular fluid, for example the bowel lumen, subcutaneous tissues, retroperitoneal space, or peritoneal cavity). Risk factors include a previous history of OHSS, age under 30 years (probably because more follicles are available), and polycystic ovary syndrome. Non-pregnant patients usually recover within 14 days with supportive treatment. The severe form (with ascites or pleural effusion and hemoconcentration) occurs in 1-10% of patients (64,65). In critical cases, hypoxemia, renal insufficiency, thromboembolism, and rarely death can occur (66). 

Prenatal diagnosis of I-cell disease has been based on greatly reduced phosphotransferase activity (cf. Biochemical Perspectives section) and abnormal intracellular-extracellular distribution of lysosomal enzymes in cultured amni-otic fluid cells (Table 17-3).As indicated in Table 17-3, amniotic fluid cells secrete large amounts of lysosomal enzymes into the extracellular medium. Decreased levels of lysosomal enzymes in chorionic villi obtained by biopsy have also been observed in I-cell disease however, the characteristic secondary effect (i.e.,increased levels of lysosomal enzymes in the extracellular compartment) is only partially expressed or not expressed at all in chorionic villi, suggesting an alternative mechanism for the transport of lysosomal proteins. Although... 

Magnesium is distributed in three major compartments extracellular, 1.3% intracellular, 13% and bone, 67%. Because of its predominantly intracellular distribution, measurement of magnesium in the extracellular compartment may not accurately reflect the total body magnesium content. The majority of magnesium in the extracellular fluid is in the ionized form only 20% to 30% is protein bound. The normal range for serum magnesium is 1.4 to 1.8 mEq/L, which equals 1.7 to 2.3 mg/dL or 0.85 to 1.15 mmol/L. 

Another use for mannitol and urea is in the treatment of dialysis disequilibrium syndrome. Too rapid removal of solutes from the extracellular fluid by hemo- or peritoneal dialysis reduces the osmolality of the extracellular fluid. Consequently, water moves from the extracellular compartment into the intracellular compartment, causing hypotension and CNS symptoms (i.e., headache, nausea, muscle cramps, restlessness, CNS depression, and convulsions). Osmotic diuretics increase the osmolality of the extracellular fluid compartment and thereby shift water back into the extracellular compartment. 

Water. Water is distributed between intracellular and extracellular compartments, the latter comprising interstitial fluids, blood, and lymph. Because water is a dipolar molecule with an uneven distribution of electrons between the hydrogen and oxygen atoms, it forms hydrogen bonds with other polar molecules and acts as a solvent. 

Extracellular fluid (ECF) is divided into smaller compartments. These spaces between the cells are called the interstitial space. The space is occupied by plasma and lymph, transcellular fluid, and fluid in the bone and connective tissues. This makes up 20% of body weight. About a third is plasma and two thirds of extracellular fluid is in the space between the cells. Transcellular fluid is also ECF but is found in the gastrointestinal (GI) tract, cerebrospinal space, aqueous humor, pleural space, synovial space, and the peritoneal space. Although fluid in the transcellular space is a small volume when compared with intracellular and extracellular compartments, the increase or decrease in volumes in transcellular spaces can have a dramatic effect on the fluid-electrolyte balance. 

Let us consider a two-compartment model (Fig. 1.2) consisting of an intracellular pool (compartment 1) and an extracellular pool (compartment 2). Urea is produced by the intracellular pool and is transported across the cell membrane into the interstitial fluids and then into the blood stream. Mass balance for these two compartments can be expressed as... 

The body fluids do not constitute a homogeneous solution of electrolytes. Body fluids are classically categorized as intracellular and extracellular. The extracellular compartment is further divided into an intra- and extravascular compartment. The intravascular fluid constitutes the blood plasma, but even blood plasma does not form a homogeneous compartment. The composition of plasma varies with anatomical location and physiological conditions. The electrolyte compositions of plasma obtained from venous and arterial blood differ, and there are diurnal variations in the electrolyte concentrations of the plasma. 

In this model, there are mass transfer eflFects between the CSF and extracellular compartments (given by the mass transfer coefficient K2) and between the extracellular compartment and the intracellular compartment (Ki). G is the natural rate of generation of the contaminant urea, L is the flow rate of CSF fluid that flows directly into the extracellular fluid, and F is the rate of urea removal due to dialysis with an artificial kidney. 

As already explained, the renal response to loss of extracellular fluid volume results in a low plasma potassium concentration. As shown in Figure 3.8B, the lowering of the extracellular concentration of potassium results in an increased potassium concentration gradient from intra- to extracellular fluid. Consequently, potassium difl uses from the intracellular to the extracellular compartment. To maintain electrochemical neutrality, hydrogen ions move in the opposite direction, from extracellular to intracellular fluid. The extra-... 

These are contained in two major compartments within the body. The extracellular fluid, the internal sea that bathes the cells, is comprised of the blood plasma and the interstitial (between the cells) fluid. A larger part of the body fluid is contained in the second compartment, the intracellular (inside the cell) compartment. Fluids in each compartment have a different chemical composition. Lymph, cerebrospinal, pericardial, pleural and peritoneal fluids are specialized interstitial fluids. 

BODY FLUID COMPARTMENTS. Fluids—water, electrolytes, and other dissolved substances—are contained in two major compartments within the body. In order to gain this concept of body compartments, all the cells of the body must be thought of as a whole. Then, all fluid outside of the cells is termed extracellular fluid, while all fluid within the cells is termed intracellular fluid. Fluids in each compartment differ in composition. 

Identify the electrolytes primarily found in the extracellular and intracellular fluid compartments. 

Volumes of the intracellular and extracellular body fluid compartments are kept constant by the osmotic pressure, which is created by the concentration of dissolved ions (electrolytes) in each compartment. The normal osmotic concentration is in the range of 280-310 mOsm/L. 

The total volume of the fluid compartments of the body into which drugs may be distributed is approximately 40 L in a 70-kg adult. These compartments include plasma water (approximately 10 L), interstitial fluid (10 L), and the intracellular fluid (20 L). Total extracellular water is the sum of the plasma and the interstitial water. Factors such as sex, age, edema, pregnancy, and body fat can influence the volume of these various compartments. 

In this theory, calcium enters the cell down the enormous electrochemical gradient that normally exists between the extracellular and intracellular fluid compartments. In doing so, it actually reverses the calcium pump and synthesizes ATP in a similar way as the reversal of the sarcoplasmic calcium pumps617 (Fig. 7). There is however, no evidence to support this theory and it has a number of unlikely features. It stresses the need for relevant data rather than circumstantial evidence, and this is particularly necessary in considering intracellular theories. 

Usually after a toxicant or drug is absorbed it can be distributed into various physiologic fluid compartments. The total body water represents 57% of total body mass (0.57 L/kg) (Table 6.5). The plasma, interstitial fluid, extracellular fluid, and intracellular fluid represent about 5, 17, 22, and 35% body weight, respectively. The extracellular fluid comprises the blood plasma, interstitial fluid, and lymph. Intracellular fluid includes... 

Cells are broadly classified as either eukaryotes or prokaryotes (see Appendix 3). Both types have a membrane, known as the cytoplasmic or plasma membrane (see Appendix 3), that separates the internal medium (intracellular fluid) of the cell from the external medium (extracellular fluid). Cytoplasmic membranes may also divide the interior of a cell into separate compartments. In addition to the cytoplasmic membrane, the more fragile membranes of plants and bacteria are also protected by a rigid external covering known as a cell wall. The combination of cell wall and plasma membrane is referred to as the cell envelope (Appendix 2). 

Much as liquid water is essential for life, frozen water, ice, is frequently lethal, especially if ice formation occurs within the cell. Upon formation of ice, loss of liquid water may impair or preclude the four basic water-related functions listed above. In particular, the structures and the activities of macromolecules and membranes may be severely damaged. In fact, the harmful effects of ice formation are due to a suite of physical and chemical effects. Physical damage from ice crystals that form within a cell can lead to rupture of membranes and the consequent dissipation of concentration gradients between the cell and external fluids or between membrane-bounded compartments within the cell. Ice formation in the extracellular fluids also can lead to damage to membranes as well as to lethal dehydration of the cell, as water moves down its concentration gradient from the intracellular space to the now depleted pool of liquid water in the extracellular space. Dehydration of the cell not only deprives it of water, but also leads to harmful and perhaps lethal increases in the concentrations of inorganic ions, which remain behind in the cell. Because the activities and structures of nucleic acids and proteins are affected by the concentrations of ions in their milieu, dehydration is expected to lead to perturbation of macromolecular structure and metabolic activity. It should come as no surprise, therefore, that with rare exceptions such as the fat body cells of certain cold-tolerant insects (Lee et al., 1993b Salt, 1962), ice formation within cells is lethal. 

Body fluids may be distributed into several compartments that interact with each other. It is possible to speak of the intracellular fluid, which is the fluid present inside the approximately 100 trillion cells found in the human organism, including red blood cells extracellular fluid, which includes blood plasma, interstitial fluid (fluid found between cells and in lymph), cerebrospinal fluid, synovial fluid, intraocular fluid, and fluids found in the gastrointestinal tract, the peritoneal cavity, the pericardial cavity, and others. The amounts of some such fluids present in normal individuals are summarized in Table 16.3. Overall, water accounts for 55-67% of an individual s weight. 

The most common molecules in the body are water and inorganic molecules such as sodium, potassium and chloride ions. A feature that is common among all living cells is that the concentrations of these ions are different in the extracellular and intracellular compartments. The extracellular fluid is high in sodium (Na+) and chloride (CT) ions, but low in potassium (K" ) ions (Figure 10.1). In contrast, the intracellular solution is... 

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