Normally, the amount of total body water should be balanced through the ingestion and elimination of water: ins and outs. To ensure this balance, as a nurse, you may need to track and record all fluid intake and output on an intake and output sheet, commonly known as an I&O sheet. This is particularly important for certain groups of clients, like those on special fluid orders, including “encourage fluids” and “restrict fluids;” those who are at risk of developing dehydration, or losing too much body fluid, which impairs normal body functions; or those who might develop edema where swelling occurs in tissues due to excess fluid build up.
High risk of dehydration exists for those who may not be drinking an adequate amount of fluids throughout the day or those who might be losing too much due to receiving certain medications, like diuretics, or through vomiting, diarrhea, bleeding, burns, excessive sweating, fever, or vigorous exercise. Common signs include dry mouth, excessive thirst, and dark urine.
Likewise, clients at risk of developing edema include those receiving intravenous fluids or those with heart or kidney disease, where the body has trouble eliminating excess fluid. The fluid builds up and causes swelling, especially in the lower extremities.
Nurses should check with the plan of care to find out if their clients’ intake and output should be monitored. So, every time one of these clients receives or loses fluids in any way, the exact volume can be recorded. These volumes are then totaled at the end of every shift and then at the end of a 24-hour period.
Figure 1: Track and record all fluid intake and output on an intake and output sheet, commonly known as an I&O sheet.
MEASURING FLUID INTAKE
For fluid intake, you’ll need to count:
- anything the client drinks, including water and beverages
- all foods that are liquid at room temperature, like ice cream, gelatin, sherbert, pudding, custard, ice chips, and popsicles
- the fluids provided through intravenous therapy, enteral, or total parenteral nutrition
Fluid intake is typically measured in milliliters (mL). But some containers use different units, so you may need to be able to make the appropriate conversions.
- 1 mL = 1 cubic centimeter (cc) = 0.001 liters (L)
- 1 fluid ounce = 30 mL
- 1 pint = ~ 500 mL
- 1 quart = ~ 1,000 mL
It’s also important to know the usual serving sizes in your facility. As a rule of thumb,
- 1 teaspoon = 5 mL
- 1 tablespoon = 15 mL
- 1 cup = 250 mL
But for other containers, like mugs, glasses, or bowls, the volume of fluid contained may vary.
Keeping in mind any necessary conversions, gather the supplies you’ll need, including:
- a graduated measuring container
Figure 2: Unit conversions when measuring volume.
MEASURING FLUID OUTPUT
Fluid output includes:
- wound drainage
Special precautions are required for certain clients, like those undergoing chemotherapy, because their urine, stool, and vomit can contain the chemotherapy agent.
Once again, your supplies include:
- a graduated container
- if there’s a possibility of splashing, personal protective equipment, such as a gown, goggles or face shield, and a mask
When measuring a client's fluid intake and output, be sure to report the following to the healthcare provider:
- changes in the usual amount of intake; for example, a client refusing to drink the served fluids
- changes in the color, clarity, or odor of the output
- if the intake and output is not balanced
- if you observe edema, especially in the lower extremities, or signs of dehydration, such as dark urine or a dry mouth
After that, document:
- the date and time
- your observations
- the measured amounts of fluid intake and output on the client’s paper or electronic I&O record
A typical I&O sheet has a column with time and two separate sections for intake and output.
- Intake is divided into oral intake, which you’ll need to fill with the amount you measured, and parenteral intake, where you will add fluid intake coming from intravenous therapy, enteral, or total parenteral nutrition.
- For the output, there’s usually one section for urine and one for everything else.
Document the amount measured as well as how the fluid was collected, such as through voiding or a urinary catheter. Make sure all amounts are in milliliters.