Solutions, colloidal crystalloidal

Three major therapeutic options are available to clinicians for restoring circulating blood volume crystalloids (electrolyte-based solutions), colloids (large-molecular-weight solutions), and blood products. 

Therapeutic intravenous (TV) fluids include crystalloid solutions, colloidal solutions, and oxygen-carrying resuscitation solutions. Crystalloids are composed of water and electrolytes, all of which pass freely through semipermeable membranes and remain in the intravascular space for shorter periods of time. As such, these solutions are very useful for correcting electrolyte imbalances but result in smaller hemodynamic changes for a given unit of volume. 

Initial fluid resuscitation consists of isotonic crystalloid (0.9% sodium chloride or lariated Ringer s solution), colloid (5% Plasmanate or albumin, 6% hetastarch), or whole blood. Choice of solution is based on 02-carrying capacity (e.g., hemoglobin, hematocrit), cause of hypovolemic shock, accompanying disease states, degree of fluid loss, and required speed of fluid delivery. 

The theoretical advantage of colloids is their prolonged intravascular retention time compared to crystalloid solutions. Isotonic crystalloid solutions have substantial interstitial distribution within minutes of IV administration, but colloids remain in the intravascular space for hours or days, depending on factors such as capillary permeability. However, even with intact capillary permeability, the colloid molecules eventually leak through capillary membranes. 

In addition to crystalloid solutions, colloids have been used for plasma expansion in patients with hemorrhagic circulatory insufficiency. In the United States, albumin and starch (i.e., hetastarch) derivatives are used most commonly, although dextran solutions also are available commercially. 

If. in place of bringing two solutions in contact with each other, they be separated by a solid or semi-solid, moist, colloid layer, diffusion takes place in the same way through the interposed layer. Advantage is taken of this hurt to separate cryst oids from colloids the process of dialyeis. The mixed solutions of crystalloid and coUoid are brought into the inner vessel of a dialyser. Fig. 13, whose bottom consists of a layer of moist parchment paper, while tiae outer vessel is filled with pure water. Water... 

Crystalloids are aqueous electrolyte-containing solutions without proteins or large molecules. Examples of crystalloids are normal saline (0.9% NaCI) and lactated Ringer s solution. Colloids are aqueous solutions that contain various proteins or other larger molecules as well as electrolytes. Protein-containing colloids include albumin and PPF. Nonproteinaceous colloids include the dextrans and hetastarch. A list detailing the compositions of several common crystalloids and colloids is given in Table 31.7. 

Surface tension of liquids can be measured by either of the two methods static and dynamic. The static methods are based on the assumption that the liquid has attained surface equilibrium. For pure liquids and solutions of crystalloids the process of attainment of equilibrium is very fast and the static methods are best suitable. But for colloidal solutions a considerable time is required to reach the equilibrium state and therefore the dynamic methods of measuring surfacf tension are preferred. The dynanJc methods measure the tension of a liquid before the surface film has had time to form. TTiere are other methods too which fall between the static and the dynamic methods. Among the static methods, the most commonly used ones are (0 the capillary rise method, (ip the du Nouy ring method, (Up the Wilhelmy balance method, and (iv) the drop-weight method.,... 

Disperse systems that lie between suspensions and crystalloid solutions colloidal solutions. 

Use a crystalloid (normal saline or lactated Ringer s solution) or a colloid (hydroxyethyl starch or albumin 5%) intravenous boluses... 

The volume of colloid administered is primarily confined to the intravascular space, in contrast to isotonic crystalloid solutions that distribute throughout the extracellular fluid space. 

Therapeutic fluids include crystalloid and colloid solutions. The most commonly used crystalloids include normal saline, hypertonic saline, and lactated Ringer s solution. Examples of colloids include albumin, the dextrans, hetastarch, and fresh frozen plasma. 

Colloids are larger molecular weight solutions (more than 30,000 daltons) that have been recommended for use in conjunction with or as replacements for crystalloid solutions. Albumin is a monodisperse colloid because all of its molecules are of the same molecular weight, whereas hetastarch and dextran solutions are polydisperse compounds with molecules of varying molecular weights. 

Colloids (especially albumin) are expensive solutions, and a large study involving almost 7,000 critically ill patients found no significant difference in 28-day mortality between patients resuscitated with either normal saline or 4% albumin. For these reasons, crystalloids should be considered first-line therapy in patients with hypovolemic shock. 

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. 

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... 

It was a Scot, Thomas Graham, who explained colloids, in 1862. He noticed that some solutions passed through parchment paper, others didn t. lie discovered that most of those that filtered through were of chemicals that formed crystals — he called them "crystalloids. The others he called colloids — from Greek kollodes, glue-like. 

Thomas Graham s investigations of diffusion 11861) led hun to characterize as crystalloids substances, such as inorganic salts which in water solutions would diffuse through a parchment membrane and as colloids... 

Colloidal Dispersions or Solutions (Sols) and Colloids. Colloidal solutions (or rather "pseudo solutions ), also called sols (or in case of liquids hydrosols) are heterogeneous systems consisting of a "dispersion medium (mostly a liquid) and a "dispersed or "suspended medium known as a "colloid . Colloidal particles are invisible under ordinary microscope but detectable by the ultramicroscope. Their size ranges from ca 1 x 10 7 to 1 x 5 smm. If the dispersion is a viscous, sticky, transparent liquid, it is what is generally known as a "colloidal solution . As examples of this may be cited a soln of gum-arabic in water and sol ns of NC in acetone, ethyl acetate or ether alcohol. When "solns are dialized, most of the colloidal particles do not pass thru the membrane. This is their principal distinction from "crystalloids , which are substances like Na chloride, etc. If part of the volatile liquid (dispersing medium), is evaporated the resulting tacky, jellylike substance is known as a gel. 

Crystalloid i.v. solutions, such as Ringer s solution, should only be used if the blood loss is relatively small (< 1 litre), since only 25-30% of the crystalloid i.v. solution has an effect on the volume. If administered in excessive amounts, this can lead to an undesired decrease in the colloidal pressure of the plasma. Crystalloid i.v. solutions, often containing glucose as a principal... 

Human albumin solution has proved extremely reliable, especially when used in conjunction with crystalloid infusions. (Synthetic iso-oncotic colloids should be avoided as far as possible because of their negative effects on coagulation and kidney function.)... 

In patients at risk for focal cerebral ischemia, hemodilu-tion has been proposed as a prophylactic and resuscita-tive therapy to ameliorate brain injury. The rationale for hemodilution therapy is based on two facts 1) blood viscosity decreases when blood is diluted with many crystalloid and colloid solutions and 2) an inverse... 

Schierhout G, and Roberts 1.1998. Fluid resuscitation with colloid or crystalloid solutions in critically ill patients a systematic review of randomised trials. Bmj 316 961-964. 

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