Colloidal plasma volume

Table 9.3. Some colloidal plasma volume expanders currently in therapeutic use. In addition to these, albumin and plasma protein fraction may also be used...

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. 

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... 

To eliminate the threat of shock, replenishment of the circulation is essential. With moderate loss of blood, administration of a plasma volume expander may be sufficient Blood plasma consists basically of water, electrolytes, and plasma proteins. However, a plasma substitute need not contain plasma proteins. These can be suitably replaced with macromolecules ( colloids ) that like plasma proteins, (1) do not readily leave the circulation and are poorly filtrable in the renal glomerulus and (2) bind water along with its solutes due to their colloid osmotic properties. In this manner, they will maintain circulatory filling pressure for many hours. On the other hand, volume substitution is only transiently needed and therefore complete elimination of these colloids from the body is clearly desirable. 

Three colloids are currently employed as plasma volume expanders— the two polysaccharides, dextran and hydroxyethyl starch, as well as the polypeptide, gelatin. 

Alternatively, colloidal plasma expanders (Table 9.3) are used. When administered at appropriate concentrations, they exert an osmotic pressure similar to that of plasma protein, hence vascular volume and blood pressure are maintained. The major disadvantages of colloidal therapy include its relatively high cost, and the risk of prompting a hypersensitivity reaction. Determined elforts to develop blood substitutes were initiated in 1985 by the US military, concerned about the issue of blood supply to future battlefields. 

Human plasma has a colloid osmotic pressure of 3.6 kPa, of which 2.8 kPa is contributed by albumin. Volume-for-volume, 4.5% albumin is approximately four times more effective in expanding the plasma volume than crystalloid solutions, and the effect lasts 6-8 hours, compared to only 15-20 min with crystalloids. Although popular in the past as volume expanders, albumin solutions have fallen into disfavour. They are prepared from pooled human plasma, with all the inherent risks of pooled blood products. Albumin can cause adverse reactions, similar to other transfusion reactions, such as chills, urticaria, and vasodilatation. These may be caused by organic or inorganic substances formed during the processing... 

Hetastarch (Hespan) [Plasma Volume Expander] Uses Plasma volume expansion adjunct in shock leukophoresis Action Synthetic colloid acts similar to albumin Dose Volume expansion 500-1000 mL (1500 mL/d max) IV (20 mL/kg/h max rate) Leukapheresis 250-700 mL X- in renal failure Caution [C, +] Contra Severe bleeding disorders, CHF, oliguric/anuric renal failure Disp Inj SE Bleeding (T PT, PTT, bleed time) EMS Observe for anaphylactic Rxns OD Unlikely but may cause fluid overload in susceptible pts... 

Use Photographic film sizing textile and paper adhesives cements capsules formedicinals matches light filters clarifying agent desserts, jellies, etc. culture medium for bacteria blood plasma volume expander microencapsulation printing inks nutrient protective colloid in ice cream. 

Crystalloid solutions are preferred over colloid solutions for circulatory insufficiency owing to decreased plasma volume. 

ALBUMIN Albumin is a normal plasma protein with two main functions to maintain the colloid osmotic pressure in blood plasma and bind and transport low molecular substances e.g. bilirubin, fatty acids, hormones and certain drugs. Administration of 1 g albumin increases the circulating plasma volume by about 18 ml. At normal serum albumin levels, 40-50 g/1 albumin is responsible for about 80% of the colloid osmotic pressure. 

Among the colloids prepared from human blood and used for plasma volume expansion, human serum albumin (HSA) and plasma protein fractions (PPF) are the most important products. HSA is a monodisperse, relatively symmetrical protein with a calculated molecular weight between 66,300 and 69,000 daltons, prepared from plasma by fractionation (for review, see Tullis 1977). PPF is a solution of plasma proteins containing about 85% albumin and 15% globulins of which the... 

Dissolved in normal saline with a concentration of about 6%, dextran exhibits similar colloid osmotic pressure and viscosity as human blood. Therefore, dextran has been used as plasma volume expander for several decades.Dextran 40 and 70, with molecular weight of 40 and 70 kDa, respectively, are prescribed for the treatment of shock or impending shock due to hemorrhage, bums, or trauma. 

HES are S5mthetic colloid solutions used as plasma volume expanders in a range of clinical settings, including hypovolaemia. The EU Pharmacovigilance Risk Assessment Committee reviewed the benefits and risks of HES products in different patient groups. The review concluded that there was a clear indication of harm when HES was used for fluid resuscitation and there was no evidence of extended benefit when compared with crystalloid solutions [34 ]. 

The fluid portion of the blood, the plasma, accounts for 55 to 60% of total blood volume and is about 90% water. The remaining 10% contains proteins (8%) and other substances (2%) including hormones, enzymes, nutrient molecules, gases, electrolytes, and excretory products. All of these substances are dissolved in the plasma (e.g., oxygen) or are colloidal materials (dispersed solute materials that do not precipitate out, e.g., proteins). The three major plasma proteins include ... 

Albumin is the most abundant (about 55%) of the plasma proteins. An important function of albumin is to bind with various molecules in the blood and serve as a carrier protein, transporting these substances throughout the circulation. Substances that bind with albumin include hormones amino acids fatty acids bile salts and vitamins. Albumin also serves as an osmotic regulator. Because capillary walls are impermeable to plasma proteins, these molecules exert a powerful osmotic force on water in the blood. In fact, the plasma colloid osmotic pressure exerted by plasma proteins is the only force that retains water within the vascular compartment and therefore maintains blood volume (see Chapter 15). Albumin is synthesized in the liver. 

Whole blood could be used for large volume blood loss, but most institutions use component therapy, with crystalloids or colloids used for plasma expansion. 

Iso-oncotic colloid solutions (plasma and plasma protein fractions), such as 5% albumin and 6% hetastarch, offer the advantage of more rapid restoration of intravascular volume with less volume infused, but there is no significant clinical outcome differences compared with crystalloids. 

The main function of albumin in the plasma is to provide colloid osmotic pressure. It is of major importance in maintaining blood volume and in the exchange of fluid between blood and the tissues. Heavy proteinuria may involve the loss of >3.5 g of albumin per day and this, in turn, causes a reduction in plasma oncotic pressure. When plasma oncotic pressure is reduced, fluid is not completely reabsorbed from the tissues at the venous end of capillaries. The fluid is retained within the tissues, causing oedema. The effects of gravity on fluid accumulation in the body causes oedema to be more marked in the lower body than in the upper parts, so oedema is often noticed first around the ankles. 

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