ICU pharmacology and drug infusions

Standard infusion dilutions and rate maths

Reviewed Nov 2026·2 references
New· views rounded down, updated weekly

Use one standard concentration per drug across the ICU, label the final concentration, and convert doses to mL/h with a single formula: rate (mL/h) = dose (mcg/kg/min) × weight (kg) × 60 ÷ concentration (mcg/mL). Double-check every high-alert infusion.

At the bedside

Timed steps
  1. 1

    Standardise

    Prepare

    One concentration per drug per unit; prefilled or pharmacy-made syringes where possible; label drug, total amount, volume, final concentration, time and preparer.

  2. 2

    Weight-based per minute

    Calculate

    mL/h = dose (mcg/kg/min) × kg × 60 ÷ mcg/mL. Example: noradrenaline 0.1 mcg/kg/min, 70 kg, 160 mcg/mL → 2.6 mL/h.

  3. 3

    Weight-based per hour

    Calculate

    mL/h = dose (mg/kg/h) × kg ÷ mg/mL. Example: midazolam 0.05 mg/kg/h, 70 kg, 1 mg/mL → 3.5 mL/h.

  4. 4

    Fixed dose

    Calculate

    mL/h = dose per hour ÷ concentration. Example: vasopressin 0.03 U/min = 1.8 U/h ÷ 0.4 U/mL = 4.5 mL/h.

  5. 5

    Independent double check

    Check

    Second nurse/doctor verifies drug, concentration, pump programme and line for vasoactives, insulin, heparin, potassium, sedatives. Use pump drug libraries where available.

  6. 6

    Avoid gaps

    Change over

    'Double-pump' or piggyback vasopressor syringe changes; never flush a vasopressor lumen.

Septic shock first-line vasopressor

Noradrenaline (norepinephrine)

IV infusion
Dose
0.05-0.5 mcg/kg/min
Range
0.05–0.5 mcg/kg/min
Worked example
70 kg at 0.1 mcg/kg/min with 160 mcg/mL = 2.6 mL/h.

Add-on vasopressor

Vasopressin

IV infusion
Dose
0.03 U/min fixed
Range
0.01–0.04 U/min
Worked example
20 U in 50 mL (0.4 U/mL): 0.03 U/min = 4.5 mL/h.

Light sedation

Dexmedetomidine

IV infusion
Dose
0.2-1.4 mcg/kg/h, no loading dose
Range
0.2–1.4 mcg/kg/h
Worked example
70 kg at 0.5 mcg/kg/h with 4 mcg/mL = 8.75 mL/h.

DKA fixed-rate infusion

Regular (soluble) insulin

IV infusion
Dose
0.1 U/kg/h
Worked example
70 kg: 7 U/h = 7 mL/h of 1 U/mL.

Common adult ICU syringe-pump dilutions (example chart)

DrugAmount in 50 mLConcentrationUsual dose range70 kg example
Noradrenaline8 mg160 mcg/mL0.05-0.5 mcg/kg/min0.1 mcg/kg/min = 2.6 mL/h
Adrenaline4 mg80 mcg/mL0.05-0.5 mcg/kg/min0.1 mcg/kg/min = 5.25 mL/h
Vasopressin20 U0.4 U/mL0.03-0.04 U/min (fixed)0.03 U/min = 4.5 mL/h
Dobutamine250 mg5000 mcg/mL2.5-20 mcg/kg/min5 mcg/kg/min = 4.2 mL/h
Glyceryl trinitrate50 mg1000 mcg/mL5-200 mcg/min50 mcg/min = 3 mL/h
Midazolam50 mg1 mg/mL0.02-0.1 mg/kg/h0.05 mg/kg/h = 3.5 mL/h
Fentanyl500 mcg10 mcg/mL0.5-2 mcg/kg/h1 mcg/kg/h = 7 mL/h
Propofol 1%Neat10 mg/mL0.3-3 mg/kg/h2 mg/kg/h = 14 mL/h
Dexmedetomidine200 mcg4 mcg/mL0.2-1.4 mcg/kg/h0.5 mcg/kg/h = 8.75 mL/h
Regular insulin50 U1 U/mLPer protocol (DKA 0.1 U/kg/h)0.1 U/kg/h = 7 mL/h
Unfractionated heparin25,000 U500 U/mL18 U/kg/h (VTE), by aPTT/anti-Xa18 U/kg/h = 2.5 mL/h

Example concentrations only; use your unit's approved chart. Diluent NS or D5 as per product (amiodarone and GTN prefer D5).

Red flag · call your senior now
A vasopressor syringe running out or a line flushed: abrupt hypotension or hypertensive surge.
Red flag
mcg vs mg or per-minute vs per-hour errors produce 60-1000-fold overdoses.
Pitfall
Drawing U-40 insulin with a U-100 syringe (2.5-fold error).
Pitfall
Bolusing other drugs through the vasopressor lumen.
Pitfall
Mixing concentrations between shifts ('double strength' noradrenaline without relabelling).
Pearl
Write orders in dose units (mcg/kg/min), not mL/h; let the chart convert.

Calculators for this topic

Infusion rate from mcg/kg/min

Pump rate in mL/h for drugs dosed in mcg/kg/min (noradrenaline, adrenaline, dobutamine, milrinone, nitroglycerin by weight).

Dose from pump rate (mcg/kg/min)

Reverse calculation: what dose is the patient receiving at the current pump rate?

Infusion rate from per-kg-per-hour dose

Pump rate for drugs dosed per kg per hour (insulin U/kg/h, midazolam mg/kg/h, propofol mg/kg/h, fentanyl mcg/kg/h, dexmedetomidine mcg/kg/h).

Infusion rate from a fixed hourly or per-minute dose

Pump rate for non-weight-based infusions such as vasopressin (U/min), labetalol (mg/min) or amiodarone (mg/h).

References

  1. 1

    Kanji S, Lam J, Johanson C, et al. Systematic review of physical and chemical compatibility of commonly used medications administered by continuous infusion in intensive care units. Crit Care Med. 2010;38(9):1890-1898

  2. 2

    Prescott HC, Antonelli M, Alhazzani W, et al. Surviving Sepsis Campaign: international guidelines for management of sepsis and septic shock 2026. Intensive Care Med. 2026;52(5):863-936. Co-published in Crit Care Med. 2026 (doi:10.1097/CCM.0000000000007075)

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