The use of synthetic colloids has become commonplace in the treatment of cr
itically ill animals. The theoretical benefits of colloid compared with cry
stalloid fluid therapy for increasing plasma volume include a more rapid an
d longer-lasting fluid resuscitation with cola lesser fluid volume necessar
y to achieve the same level of resuscitation, and reduced loids, a lesser f
luid volume necessary to achieve the same level of resuscitation, and reduc
ed risk of edema formation. These benefits are achieved, in part, by increa
sing or maintaining the patient's colloid osmotic pressure (COP) to retain
fluid within the vasculature and limit extravasation of fluid into the inte
rstitium. COP, and ultimately fluid balance, are normally highly dependent
on the concentration of albumin within the vasculature. Understanding how C
OP is affected in different conditions (e.g., hypovolemia, sepsis, systemic
inflammatory response syndrome, acute and chronic hypoalbuminemia) can gui
de clinicians in the appropriate uses of colloid therapy.