COLLOID SOLUTIONS AND BLOOD SUBSTITUTES

Colloid solutions are generally administered in a volume equivalent to the volume of blood lost (see Chapter 47 ). The initial volume of distribution is equivalent to the plasma volume. The half-life in circulation of albumin is normally 16 hours, but it can be as short as 2 to 3 hours in pathophysiologic conditions.^[121] The synthetic colloids, processed albumin, and protein fractions have minimal or no risks of infection. Blood substitutes are useful to restore intravascular fluid volume temporarily until definitive treatment can be established. They are inexpensive, have a long storage life, and lack the risk of transmitting viral diseases.

Five Percent Albumin

Five percent albumin or plasma protein fractions (e.g., Plasmanate) have a colloid osmotic pressure of about 20 mm Hg (i.e., near-normal colloid osmotic pressure). Preparation methods eliminate infectious agents. These solutions are chosen when crystalloids fail to sustain plasma volume for more than a few minutes because of low colloid osmotic pressure. These solutions are most appropriate when there is an abnormal loss of protein from the vascular space, such as in cases of peritonitis or extensive burns.