Hello and welcome to the Zero to Finals podcast.

My name is Tom and in this episode I'm going to be talking to you about intravenous fluids.

And you can find written notes on this topic at zero tofinals.com slash IV fluids

or in the general surgery section of the Zero to Finals surgery book. So let's get straight into it.

Prescribing IV fluids is a very common task on your surgical rotations, as well as practically

all inpatient medical jobs. The information here is designed to help you understand the concepts

for your exams. When you're

actually prescribing fluids, follow the national and local guidelines and consult with your seniors

when you're in doubt. This should not be used as a guide for prescribing. Let's start by talking

about the fluid compartments in the body. Fluid within the body is distributed across different spaces.

Water, electrolytes, glucose and proteins constantly move between the fluid spaces to find a balance

and to carry out their functions. There are two categories of fluid spaces in the body. The

intracellular space, which is the space inside the

cells, and this makes up two-thirds of the total body fluids, and the extracellular space,

which is the space outside the cells. And this makes up one-third of the total body fluids.

So two-thirds of the fluid in the body is contained within the cells, and one-third of the fluid in the body is contained within the cells

and one-third of the fluid in the body is outside the cells. The extra cellular space

or the space outside the cells can be further subdivided into three spaces. The intravascular

space, which is the space inside blood vessels, and this makes up

20% of the extracellular fluid, the interstitial space, which is the functional tissue space between

and around the cells, and this makes up 80% of the extracellular fluid, and the third space.

The third space refers to areas of the body that do not normally contain fluid,

...