Using Athena
168
CAEAthena
PN: 905K520652 v2.8
Hematology Model
The physiological model calculates hematocrit values (i.e. percentage of total blood hemoglobin)
dynamically and continuously, taking into account blood and fluid losses, as well as the intravenous
infusion of fluids such as whole blood, packed red blood cells, colloids and crystalloids.
Instructors can create patients with both normal and pathophysiological hematocrit levels. In
addition, learners discover how administering various fluids affects hematocrit, the oxygen-carrying
capacity of blood, and the resulting patient response.
The following important assumptions have been made in the design of the Hematology Model:
• Blood is comprised of two components: red blood cells and plasma
• Plasma is comprised of two components: colloid and crystalloid. The term colloid is used
to describe substances that generate a clinically significant colloid osmotic pressure - for
example, fresh frozen plasma, albumin and hetastarch. The term “crystalloid” is used to
describe salt solutions for infusion - for example, normal saline, dextrose in water and
Ringer’s Lactate.
• The mixing of blood and its various constituents is instantaneous and homogeneous. In
other words, one liter of crystalloid administered intravenously equilibrates immediately
and homogeneously throughout the entire circulation.
• This Hematology Model does not distinguish between the differing clinical effects of
colloids and crystalloids. For example, osmotic pressures and capillary leakage rates are
not taken into account. Likewise, fluid kinetics and fluid distribution within the circulation
and interstitial and intracellular spaces are also not modeled.
In the Hematology Model, the following model variables, definitions and relationships have been
established:
• Red Blood Cell Volume: The volume of red blood cells within the circulation
• Plasma Volume: The volume of plasma within the circulation
• Total Blood Volume: The volume of blood (i.e. Red Blood Cell Volume + Plasma Volume)
within the circulation
• Blood Volume Loss: The amount or rate of decrease in the total blood volume. A given
amount or rate of blood loss proportionally decreases both the Red Blood Cell Volume
and the Plasma Volume according to the current hematocrit.
• Plasma Volume Loss: The amount or rate of decrease in the plasma volume. A given
amount or rate of plasma loss decreases the plasma volume without changing the red
blood cell volume. Plasma Volume Loss refers collectively and generically to all plasma
fluid losses, including evaporative, transcellular (e.g. ascites, pleural effusion), bowel and
third space losses.
• Hematocrit: The ratio of Red Blood Cell Volume to Total Blood Volume, expressed as a
percentage
To Next Page
Loading...
