Colloids oncotic pressure

The primary disadvantage is the large volume necessary to replace or augment intravascular volume. Approximately 4 L of normal saline must be infused to replace 1 L of blood loss. In addition, dilution of colloid oncotic pressure leading to pulmonary edema is more likely to follow crystalloid than colloid resuscitation. 

Weil MH, Henning RJ, Puri VK. Colloid oncotic pressure clinical significance. Crit Care Med 1979 7 113. 

Gum-Saline. Gum is a galactoso—gluconic acid having molecular weight of approximately 1500. First used (16) in kidney perfusion experiments, gum—saline enjoyed great popularity as a plasma expander starting from the end of World War I. The aggregation state of gum depends on concentration, pH, salts, and temperature, and its colloid oncotic pressure and viscosity are quite variable. Conditions were identified (17) under which the viscosity would be the same as that of whole blood. 

The liver does not synthesise enough albumin and does not metabolise aldosterone. A lack of albumin in the vascular space reduces colloid oncotic pressure and water flows out of the blood vessels to form tissue oedema or ascites (oedema in the peritoneal cavity). Water oozing from the pulmonary arteries causes pulmonary oedema. 

The use of colloids has recently been advocated for the resuscitation of hypovolemic horses and for the treatment of severe hypoproteinemia (McFarlane 1999). Colloids have two advantages over crystalloids that makes them attractive for fluid therapy. Firstly, because of their persistence in the circulation, a three to six times lower volume of a colloid solution is required to produce the same resuscitative effect as a crystalloid solution (Rackow et al 1987). This is particularly useful in acute resuscitation of severely dehydrated horses or in the field where large amounts of crystalloids may be difficult to transport. Secondly, the administration of colloids can increase colloidal oncotic pressure, in contrast to the administration of large volumes of crystalloids, which decreases the colloidal oncotic pressure (Jones et al 1997,2001). 

ALB was one of the first identified biochemical markers of malnutrition and has long been used in population studies. ALB is a relatively insensitive index of early protein malnutrition because there is a large amount normally found in the body (4 to 5 g/kg of body weight), it is highly distributed in the extravascular compartment (60%), and it has a long half-life (18 to 20 days). However, chronic protein deficiency in the setting of adequate nonprotein calorie intake leads to marked hypoalbuminemia because of a net ALB loss from the intravascular and extravascular compartments (kwashiorkor). Serum ALB concentrations also are affected by moderate-to-severe calorie deficiency hepatic, renal, and GI disease and infection, tramna, stress, and burns. In many cases, interpretation of serum ALB concentrations relative to nutrition status is difficult however, a positive correlation between decreased serum ALB concentrations and poor clinical outcome has been demonstrated in a variety of settings. Additionally, serum ALB concentrations of 2.5 g/dL or less can be expected to exacerbate ascites and peripheral, pulmonary, and GI mucosal edema due to decreased colloid oncotic pressure. 

Colloids Resuscitation fluids that restore and/or increase the intravascular oncotic pressure. 

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. 

Filtration is driven by both hydrostatic and oncotic (colloid osmotic pressure) transport. 

One precaution when using colloids is that the plasma total solids or total protein concentration is no longer a useful guide to plasma oncotic pressure (Bumpus et al 1998). 

Oncotic pressure is defined in Dorland s Illustrated Medical Dictionary as the osmotic pressure due to the presence of colloids in a solution. ... 

The pathogenesis of ascites is complex because of a number of simultaneously operating factors. Of these, the most important are (1) increased hydrostatic portal venous pressure, with increased resistance to flow, (2) decreased colloid osmotic (oncotic) pressure because of hypoalbu-... 

All chemistries were determined by the clinical laboratory at the University of Utah Medical Center. A detailed error analysis shows the range of errors for clearance value to be between 10% at the start of dialysis and 15% at the end of dialysis. Oncotic pressures were measured with a colloid osmometer (Model 186, Instrumentation Laboratories, Boston MA) to 0.2 mm Hg. 

Oncotic pressure (or colloid osmotic pressure) is the osmotic pressure that results from the difference between the protein (mainly albumin) concentrations of plasma and the interstitial fluid. Water is lost from the body via feces, urine, salivation, insensible respiration, and through the skin, with sensible perspiration of sweat occurring in a few species. Although the movement of proteins between spaces is restricted, water and small ions can move across permeable membranes between the spaces. The volume of ECF is highly dependent on its sodium concentration and, under physiological conditions, the sodium ion concentrations of plasma and interstitial fluids are similar. 

The effective osmotic pressure of the blood across capillary walls. The greatest contribution to the colloid osmotic pressure comes from plasma proteins, which, unlike the plasma ions, cannot move through the capillary walls. The oncotic pressure balances the effect of capillary blood pressure which tends to force water into the interstitial spaces. 

---