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Ounces to MillilitersWhen caring for patients, nurses often need to convert between ounces and milliliters. Although these equivalencies are typically memorized, let’s start with a simple problem of converting ounces to milliliters to demonstrate the technique of dimensional analysis. Practice Problem #1: Ounces to MilliletersA patient drank an 8 ounce can of juice. The nurse must document the intake in milliliters. How many milliliters of juice did the patient drink? Here is an example of how to solve this conversion problem using dimensional analysis. 1. Identify the unit being solved for as the goal. In this example, we want to convert the patient’s oral intake from ounces to milliliters, so we are solving for milliliters (mL):
2. Set up the numerator in the first fraction to match the desired unit to be solved. In this case, we want to know how many milliliters should be documented, so mL is placed in the numerator. To complete the fraction, we add information already known. In this example, we know that 30 mL is equivalent to 1 ounce, so 30 mL is added to the numerator and 1 ounce is added to the denominator:
3. Add the second fraction to the equation. When using dimensional analysis, fractions are set up so the same units are diagonal from each other so they cancel each other out, leaving the desired unit. For this problem, the second fraction is set up to include ounces in the numerator so that it will cancel out ounces in the denominator of the first fraction. “8” is then added to the numerator because we know from the problem that the patient consumed 8 ounces. “1” is then added to the denominator because the purpose of the second fraction is to cancel out units:
4. Cancel out similar units that are diagonal to each other. After canceling out ounces, we are left with our desired units of mL:
5. Multiply across the numerators and then multiply across the denominators:
6. Divide the numerator by the denominator to get the final answer with the desired goal unit:
Practice Problem #2: Ounces to MilliletersIn a similar manner, dimensional analysis can be used to calculate a patient’s total liquid intake on their meal tray. See Figure 5.6[1] for an example of a patient’s meal tray in a hospital setting. Figure 5.6 Meal TraySample scenario: Your patient consumed 8 ounces of coffee, 4 ounces of orange juice, and 4 ounces of milk. How many milliliters of intake will you document? Calculate using dimensional analysis. 1. Add up the total intake in ounces:
2. Start by identifying mL as the goal unit for which you are solving. In this case, we want to know the number of milliliters:
3. Create the first fraction by matching milliliters in the numerator. Then, using known equivalency that 30 mL is equal to 1 ounce, place 30 in the numerator and 1 ounce in the denominator:
4. Create the second fraction to cross out units. You know you want to cross out ounces, so place ounces in the numerator. Then, add the known amount of ounces consumed, which was 16:
5. Multiply across the numerators and then the denominators. Divide the numerator by the denominator of 1 for the final answer in mL:
Video Review of Calculating Intake and Output[2]Pounds to KilogramsConverting pounds to kilograms is typically memorized as an equivalency, but let’s practice using the technique of dimensional analysis. Sample problem: The patient entered their weight as 137 pounds on their intake form. Convert the patient’s weight to kilograms to document it in the electronic medical record. Round your answer to the nearest tenth. Calculate using dimensional analysis.
Review the
following modules within SWTC’s Dimensional Analysis in Nursing page for more information about solving tablet problems. When measuring intake and output you may need to convert ounces oz to milliliters mL what does 1 oz equal?Basic conversions:
= 1 cc. 1 ounce (oz.) = 30 ml.
When measuring intake and output you may need to convert ounces to milliliters?Many times test questions will give you the amount in ounces (oz), but we record intake and output in milliliters (mL). To convert oz to mL, simply multiply the amount of oz by 30.
Should intake and output be equal?Intake and output (I&O) indicate the fluid balance for a patient. The goal is to have equal input and output. Too much input can lead to fluid overload. Too much output can cause dehydration.
How does the nurse properly measure intake and output?How does a nurse appropriately measure intake and output? Rationale: All liquids consumed must be counted including liquids with meals, gelatin, custards, ice cream, popsicles, sherbets, and ice chips (recorded as 50% of measured volume [e.g., 100 mL of ice chips equals 50 mL of water]) for the intake record.
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