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Medicine pump: daily dose to ml per hour

How many ml per hour should the pump give, and when should the cartridge be changed?

Answer: In palliative care and at home, many residents receive medication in a pump, e.g. subcutaneously over the whole day. The doctor prescribes a daily dose in mg, and the pharmacist or nurse fills a reservoir with a known concentration. The calculator converts daily dose to ml per day and ml per hour and shows how many days the reservoir lasts so you can check the pump setting and plan changes. It suggests no dose and does not replace the prescription or the delegation you work under.

Formula

Volumen pr. døgn (ml) = ordineret døgndosis (mg) ÷ koncentration (mg/ml)

Hastighed (ml/time) = volumen pr. døgn ÷ 24

Reservoiret rækker (døgn) = reservoirets volumen ÷ volumen pr. døgn

Eksempel: 30 mg/døgn ÷ 2 mg/ml = 15 ml/døgn = 0,63 ml/time. 50 ml rækker 3,3 døgn

Symbols and units in the formula
SymbolMeaningUnit
doegndosis_mgOrdered daily dosemg
koncentrationConcentration in reservoirmg/ml
reservoir_mlVolume in the reservoir or cassetteml
=Pump's speedml/time
=Volume per dayml
=Reservoir lastsdøgn
=Dose per hourmg/time

Validity and source

Source
Medicinregning: volumen = dosis ÷ styrke, fordelt på døgnets 24 timer

Does not apply when

  • The pump is set per prescription and your instructions and the setting is double-checked with a colleague. Extra doses (PN/bolus) are not included in the calculation and cause the reservoir to empty faster. Note each bolus and plan change after what's actually left.

Worked example

The calculator's own default values inserted. The figures are calculated with exactly the formula the tool uses.

Substituted

  • Ordered daily dose30 mg
  • Concentration in reservoir2 mg/ml
  • Volume in the reservoir or cassette50 ml

Giver

  • Pump's speed0.63 ml/time
  • Volume per day15.0 ml
  • Reservoir lasts3.3 døgn
  • Dose per hour1.25 mg/time

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Sådan bruger du den

I palliativ pleje får mange borgere smertestillende eller beroligende medicin i en pumpe over hele døgnet. Ordinationen står som en døgndosis i mg. Du skal kunne kontrollere, at pumpen giver det rigtige antal ml i timen, og vide, hvornår kassetten skal skiftes.

Step by step

  1. Find døgndosis i ordinationen.
  2. Find koncentrationen i reservoiret på etiketten.
  3. Del døgndosis med koncentrationen. Det giver ml pr. døgn.
  4. Del med 24. Det giver ml i timen.
  5. Del reservoirets volumen med ml pr. døgn. Det giver antal døgn, til det skal skiftes.

Typical errors

  • At glemme ekstra doser (bolus). De tømmer reservoiret hurtigere.
  • At bruge en gammel koncentration, når apoteket har lavet en ny kassette.
  • At ændre pumpen uden ordination og delegering.

Examples from everyday life

Smertepumpe i hjemmet

En borger i eget hjem har en pumpe med en ordineret døgndosis på 30 mg morfin. Kassetten indeholder 50 ml med 2 mg/ml.

Ordered daily dose
30 mg
Concentration in reservoir
2 mg/ml
Volume in the reservoir or cassette
50 ml

It means: Pumpen skal give 0.63 ml/time, altså 15 ml om døgnet. Kassetten rækker 3.3 24 hours uden ekstra doser.

Beroligende medicin i en anden pumpe

En borger har også en ordination på 10 mg midazolam i døgnet. Reservoiret er 50 ml med 1 mg/ml.

Ordered daily dose
10 mg
Concentration in reservoir
1 mg/ml
Volume in the reservoir or cassette
50 ml

It means: Hastigheden er 0.42 ml/time, og reservoiret rækker 5 24 hours. Dosis pr. time er 0.42 mg/time.

Dosis er øget

Lægen har øget døgndosis af morfin til 60 mg. Reservoiret er stadig 50 ml med 2 mg/ml.

Ordered daily dose
60 mg
Concentration in reservoir
2 mg/ml
Volume in the reservoir or cassette
50 ml

It means: Pumpen skal nu give 1.25 ml/time, og kassetten rækker kun 1.7 24 hours. Planlæg skiftet, og fortæl aftenvagten det.

Rule of thumb

Ved 1 mg/ml er ml pr. døgn det samme som mg pr. døgn.

How to check the answer

Gang ml/time med 24 og med koncentrationen. Så skal du få døgndosis igen.