Step-by-Step IV Fluid Calculations
Example: A 37lb dog
Step 1. Obtain the weight of the patient in kilograms. Usually, formulas for fluid rates and drug calculations require a patient weight in kilograms (kg). If you are starting with pounds, divide that number by 2.2.
Ex: 37/2.2=16.82kg
Step 2. Decide whether you will need a macro drip set or a micro drip set. If the patient is less than 10kg use a micro drip set. A micro drip set is one that delivers 60 drops of fluid to equal 1 mL. If the patient is larger than 10kg use a macro drip set, which is one that delivers 15 drops of fluid to equal 1 mL. Macro drip sets also come in a 10 drop per mL variety; micro drip sets also come in 50 gtt/mL. *At VTI, we have the 15 drop per mL and 60 gtt/mL.
Ex: This patient (37lb) will need a MACRO drip set, 15gtt/mL
Step 3. Do the calculation to determine your patient’s surgical fluid rate per hour. *Remember the canine surgical fluid rate is 5mL/kg/hr*
Round to 2 decimal places.
Multiply the patient’s weight (in kg) by 5 ml/kg/hr
Ex: 16.82 kg x 5 ml/kg/hr = 84.05 mL/hr
Step 4. Multiply the number in step 3 by the chosen drip set (10, 15 or 60). Also round this number two decimal places.
Ex: 84.05 ml/hr x 15 gtt/ml = 1261.36 gtt/hr
Step 5. Divide the number in Step 4 by 3600. 3600 is the number of seconds in an hour. This answer is the number of drops that your patient should receive each second.
Round to 2 decimal places.
Ex: 1261.36 gtt/hr / 3600 sec/hr = 0.35 gt/sec
Your patient should receive 0.35 gtt of fluid each second. HOW can you possibly count 0.35 gtt every second?! You can’t, so an easier thing to do is to multiply by a whole number. This will give you the number of drops that your patient should receive within that many seconds.
*Varies with each problem
Ex: 0.35 gt/sec x 3 = 1.05 gtt/3 seconds 1 gt/3 sec
A Second Way to Work the Same Problem
LET’S LOOK AT THIS AS AN EQUATION…
Step 1. The equation begins with the amount of fluid that the patient should receive each hour under anesthesia.
Step 2. Multiply by the drip set. (Macro = 15 gtt/mL)
Step 3. To cancel out hours, and get an answer in seconds, divide by 3600.
84.05 mL x 15gtt x 1 hr =0.35 gt/sec x 6sec= 2.1 gtt/6 sec or 1gt/3 sec
1hr 1 mL 3600 sec
A Third Way to Work the Same Problem
If you don’t like fractions with the units attached to them, then plug in the numbers to this equation:
(Patient’s fluid volume each hour) x (drip set) = ______gtt/sec
3600
Then find magic number to get the drops into a countable whole number
*This must be within 0.1 of a whole number
Example: 0.9-1.1