HSE INTERACTIVE MODULES

DEMONSTRATED BY DR. MICHAEL PARKER

Demo VI: Effect of Input / Output on Body Fluid Compartments

For this interactive module, Dr. Michael Parker has developed a real-time simulation that allows students to explore how the contents of intravenous (IV) fluids distribute in a patient's body - a complex concept for students, residents, and doctors alike. The module is based around the principle that a bag of IV fluid might, for example, have more sodium or less potassium, depending on the end-goal for the patient. In addition, once the fluid is given to a patient and depending on its content, it equilibrates in different places in the body: some stays inside blood vessels, some goes inside cells, and some remains outside to bathe the cells. It's a lot to keep a handle on, and Dr. Parker wanted a way to help students intuit the entire process.

The main part of the diagram shows an IV fluid bag, which flows down into a schematic representation of the body. The schematic has two "compartments," one for ECF or extracellular fluid and one for ICF, or intracellular fluid. To begin, the compartments are set with simple fluid volumes that make sense for an average human being. The extracellular fluid compartment also starts with a specified sodium concentration. Students who want to play around with the diagram can manipulate it in several ways. In the upper left-hand corner of the screen, there is a box with pre-set IV fluids that they can click on. Or they can go to the right side of the diagram, where a box with custom controls lets students choose their own parameters for the composition of the fluid.

Either way, once the fluid is set, students are asked to do one more thing. In another box on the right of the screen, they make predictions about where the fluid influx will be distributed in the body. Then they click the "Run Fluids" button to see if their predictions were accurate. There is also a "Show/Hide Components" box that allows students to turn on a colored shading tool that outlines where the fluid will be distributed before the "Run Fluids" button is pressed. As Dr. Parker points out, there are endless variations to this diagram, and students can use trial and error to test their understanding of the concept.

Key Lesson: This module's real-time simulation allows students to play with an almost infinite variation of IV fluid components and watch the results in the body.