Plasma volume

Microwave discharges at pressures below 1 Pa witli low collision frequencies can be generated in tlie presence of a magnetic field B where tlie electrons rotate witli tlie electron cyclotron frequency. In a magnetic field of 875 G tlie rotational motion of tlie electrons is in resonance witli tlie microwaves of 2.45 GHz. In such low-pressure electron cyclotron resonance plasma sources collisions between tlie atoms, molecules and ions are reduced and the fonnation of unwanted particles in tlie plasma volume ( dusty plasma ) is largely avoided. 

Modelling plasma chemical systems is a complex task, because these system are far from thennodynamical equilibrium. A complete model includes the external electric circuit, the various physical volume and surface reactions, the space charges and the internal electric fields, the electron kinetics, the homogeneous chemical reactions in the plasma volume as well as the heterogeneous reactions at the walls or electrodes. These reactions are initiated primarily by the electrons. In most cases, plasma chemical reactors work with a flowing gas so that the flow conditions, laminar or turbulent, must be taken into account. As discussed before, the electron gas is not in thennodynamic equilibrium... 

The volume of extracellular fluid is direcdy related to the Na" concentration which is closely controlled by the kidneys. Homeostatic control of Na" concentration depends on the hormone aldosterone. The kidney secretes a proteolytic enzyme, rennin, which is essential in the first of a series of reactions leading to aldosterone. In response to a decrease in plasma volume and Na" concentration, the secretion of rennin stimulates the production of aldosterone resulting in increased sodium retention and increased volume of extracellular fluid (51,55). 

Hydroxyethylstarch [9005-27-0] has been investigated by hydrodynamic and magnetic spectroscopic methods (128) because of its increasing use as a plasma volume expander. 

Multiples of plasma volume, ie, number given multiphed by plasma volume equals total volume in which the factor is located. 

The apparent volume of distribution (Vd) slightly increases depending on plasma volume (Fp), tissue volume (Ft), and free tissue fraction (ft) whereas the half-life slightly decreases with significantly increasing free plasma fraction. 

The corticosteroids are administered with caution in older adults because they are more likely to have preexisting conditions such as congestive heart failure, hypertension, osteo-poros s and arthritis which may be worsened by the use of such agents The nurse monitors older adults for exacerbation of existing conditionsduring corticosteroid therapy. In addition, lower dosages may be needed because of the effects of aging, such as decreased muscle mass renal function, and plasma volume. 

Plasma protein fractions include human plasma protein fraction 5% and normal serum albumin 5% (Albuminar-5, Buminate 5%) and 25% (Albuminar-25, Buminate 25%). Plasma protein fraction 5% is an IV solution containing 5% human plasma proteins. Serum albumin is obtained from donated whole blood and is a protein found in plasma The albumin fraction of human blood acts to maintain plasma colloid osmotic pressure and as a carrier of intermediate metabolites in the transport and exchange of tissue products. It is critical in regulating the volume of circulating blood. When blood is lost from shock, such as in hemorrhage, there is a reduced plasma volume. When blood volume is reduced, albumin quickly restores the volume in most situations. 

The IV solutions of plasma expanders include hetastarch (Hespan), low-molecular-weight dextran (Dextran 40), and high-molecular-weight dextran (Dextran 70, Dextran 75). Plasma expanders are used to expand plasma volume when shock is caused by bums, hemorrhage surgery, and otiier trauma and for prophylaxis of venous thrombosis and diromboembolism. When used in die treatment of shock, plasma expanders are not a substitute for whole blood or plasma, but tiiey are of value as emergency measures until die latter substances can be used. 

Notes Assuming a moderately active 70 kg man with 40% of body weight as muscle (28 kg), a liver weight of 1.8 kg, a plasma volume of 3 L, and 9 kg of adipose tissue. Endurance trained individuals store -125-150 mmol/kg wet muscle of glycogen in muscle and 400-700 mmol/kg wet tissue of glycogen in liver,... 

Dextran 70 70000 6% w/v in 5% w/v glucose injection or 0.9% w/v sodium chloride injection Autoclave IV used to produce an expansion of plasma volume in conditions associated with loss of plasma proteins... 

Plasma volume of distribution Area under the curve ... 

Plasma volume of distribution Half-life time of absorption Transfer constant of absorption Half-life time of elimination Transfer constant of elimination Area under the curve ... 

Hence, the slope of the semilogarithmic plot of 1 - Cp tVC versus time t yields the transfer constant of elimination kp. From the known rate constant of infusion k, the transfer constant of elimination kp and a graphical estimate of one can then derive the plasma volume of distribution Vp, using the steady-state condition which has been derived above. 

In practice, one will seek to obtain an estimate of the elimination constant kp and the plasma volume of distribution Vp by means of a single intravenous injection. These pharmacokinetic parameters are then used in the determination of the required dose D in the reservoir and the input rate constant k (i.e. the drip rate or the pump flow) in order to obtain an optimal steady state plasma concentration... 

This model is an extension of the one-compartment model for intravenous injection (Section 39.1.1) which is now provided with a peripheral buffering compartment which exchanges with the central plasma compartment. Elimination occurs via the central compartment (Fig. 39.12). The model requires the estimation of the plasma volume of distribution and three transfer constants, namely for... 

We now turn our attention to the graphical determination of the various parameters of our two-compartmental model, i.e. the plasma volume of distribution Vp,... 

In the special case of a one-compartment open model, it can easily be shown that the steady-state volume is identical to the plasma volume Vp which has been defined before in Section 39.1.1 (eq. (39.12)) ... 

FIGURE 10-2. Distribution of body fluids showing the extracellular fluid volume, intracellular body fluid volume, and total body fluids in a 70 kg adult. Extracellular volume (ECV) comprises 14 liters of total body fluid (42 liters). Plasma volume makes up approximately 3 liters of the 14 liters of ECV. Intracellular volume accounts for the remaining 28 liters of total body fluids with roughly 2 liters being located within the red blood cells. Blood volume (approximately 5 liters) is also depicted and is made up of primarily red blood cells and plasma. (Reprinted from Guyton AC, Hall JE. Textbook of Medical Physiology. 8th ed. Philadelphia Saunders, 1991 275, with permission.)... 

If hemorrhagic cystitis occurs, the goals of treatment are to decrease exposure to the offending etiology, establish and maintain urine outflow, avoid obstruction and renal compromise, and maintain blood and plasma volume. Restoration of normal bladder function is the ultimate goal following acute treatment. 

Human albumin is a colloid used as a plasma volume expander and is not a source of nutrition. Albumin should be administered separately from PN because it may be incompatible and... 

Vasopressin is a peptide hormone produced by the hypothalamus and secreted by the posterior pituitary in response to stimulation. Normal stimuli for vasopressin release are hyperosmolarity and hypovolemia, with thresholds for secretion of greater than 280 mOsm/kg and greater than 20% plasma volume depletion. A number of other stimuli, such as pain, nausea, epinephrine, and numerous drugs, induce release of vasopressin. Vasopressin release is inhibited by volume expansion, ethanol, and norepinephrine. The physiological effect of vasopressin is to promote free water clearence by altering the permeability of the renal collecting duct to water. In addition, it has a direct vasoconstrictor effect. Consequently, vasopressin results in water retention and volume restoration. In patients with septic shock, vasopressin is appropriately secreted in response to hypovolemia and to elevated serum osmolarity (R14). 

As plasma volume decreases, less blood is available for ventricular filling. 

Hypertension (blood pressure >140/90 mmHg) may be caused by an elevation in cardiac output or excessive vasoconstriction. Diuretics are used in these patients to reduce cardiac output. Assume that the hearts of these individuals are operating on the ascending portion of the cardiac function curve. As the plasma volume is reduced in response to treatment with diuretic drugs, venous return and preload are reduced, as are ventricular filling and stroke volume, and cardiac output, thus bringing blood pressure back within the normal range. 

Diuretics. The primary mechanism by which diuretics reduce blood pressure is to decrease plasma volume. Acting at the kidney, diuretics increase sodium loss and, due to the... 

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