24-hour Total Problems Written Explanation

There are times when it is important to know how much fluid a patient is receiving via IV (i.e., parenteral total). For example, if a patient is on strict I&O, or if a patient is on fluid restrictions, it would matter how much fluid they were getting in this way. So how do we calculate the information? Let’s look in detail at an example:

The patient is receiving LR at 125 ml/hr. He also has three antibiotics ordered:                        Keflex 1 g in 100 ml twice daily (infused over 30 minutes), Cipro 500 mg in 50 ml three times daily (infused over 30 minutes), and Levaquin 2 g in 250 ml daily (infused over one hour). How much (in ml) is the patient receiving IV daily? [NOTE: LR is the primary fluid, the antibiotic are secondary fluids or piggybacks.]

Start with the three secondary fluids, the antibiotics. To determine how much of each of them the patient is receiving per day, all that is needed is the volume of each per dose, and the number of doses per day:

Keflex ml/day = 100 ml/dose x 2 doses/day = 200 ml

Cipro ml/day = 50 ml/dose x 3 doses/day = 150 ml

Levaquin ml/day = 250 ml/dose x 1 dose/day = 250 ml

Then add them together. TOTAL 600 ml – total of the 3 secondary fluids

Note that time does not affect the volume of the secondary fluids in any way. Time affects only the fluid that expresses itself in time (ml per hour), the primary fluid, in this problem the lactated Ringers.

Now, an important thing to know is that the pump can run only one fluid at a time. Thus, when the antibiotics/secondary fluids run, the primary fluid stops. So for the LR in this problem, we cannot just say 125 ml/hr x 24 hours. 

We have to look at the secondary fluids again. How long does it take for one dose of Keflex to run in? 30 minutes. How many doses a day? Two. So for one hour a day, Keflex is running in instead of LR. We could express it this way: Keflex min/day = 30 min/dose x 2 doses/day = 60 min. = 1 hour

Cipro min/day = 30 min/dose x 3 doses/day = 90 min. = 1.5 hours

Levaquin min/day = 60 min/dose x 1 dose/day = 60 min. = 1 hour

TOTAL 3.5 hours

So the lactated Ringer’s does not run 24 hours a day, because for 3.5 hours a day, secondary fluids are running. Thus, the LR runs 24 – 3.5 = 20.5 hours per day. How much LR runs in 24 hours, then?

LR 125 ml/hr x 20.5 hr = 2562.5 ml

So total IV input is LR 2562.5 ml + secondary fluids 600 ml = 3162.5 ml – your answer to the problem.

All this can be abbreviated to a much shorter version, as follows:

    LR                         KEFLEX                        CIPRO                      LEVAQUIN

125 ml/hr            100 ml/dose                50 ml/dose                250 ml/dose

x 20.5 hr                 x2 doses                      3 doses                     x 1 dose

2562.5 ml               +200 ml                        +150 ml             +250 ml = 3162.5ml

                                  - 1 hr -                            1.5 hr -                  1 hr = -3.5 hr

You will follow exactly the same series of steps in doing any 24-hour problem.