Anesthesia & Sedation

Midazolam CRI

ICU sedation and anxiolysis CRI for dogs and cats. Used for patient comfort during mechanical ventilation, prolonged catheter or wound care, or recovery from major procedures. Status epilepticus management when seizures recur after initial bolus benzodiazepine therapy. Anesthetic MAC-sparing during inhalant anesthesia (combine with opioid for balanced anesthesia). Continuous respiratory monitoring required; particularly with opioid co-administration or pre-existing pulmonary compromise.

Stock: 5 mg/mL (5 000 µg/mL), 5 mL vial (25 mg)

How this calculator works

Enter the patient's weight and the desired CRI dose. The calculator picks a concentration (1, 0.5, or 0.2 mg/mL) that keeps the pump in its accurate range (≥ 2 mL/hr for most syringe pumps).

The recommended concentration shows a suggested tag that updates as you change the patient inputs. Click any tab to override; a notice will appear if your choice gives a pump rate outside the precision range.

Two loading-dose scenarios are computed: pre-CRI sedation loading (0.1–0.3 mg/kg IV before starting the CRI) and status epilepticus loading (0.2–0.5 mg/kg IV bolus, may repeat).

Calculation mode

Standard bag → pump rate Bag at a chosen concentration; calculator returns the pump rate to deliver the dose. Target pump rate → bag concentration Set the pump rate; calculator returns the bag concentration and volume of stock to draw.

Species

Dog Cat

Weight

lb kg

Dose (mg/kg/hr)

Typical range: 0.1–0.5 mg/kg/hr (dogs and cats)

Bag preparation

500 µg/mL

5 mL stock (1 vial, 25 mg) into 45 mL of 0.9% NaCl or 5% dextrose, final volume 50 mL

Use a different concentration

All preparations are pharmacologically equivalent. The default (500 µg/mL) fits the most common clinical use case. The alternatives below cover situational needs.

500 µg/mL (default) 5 mL stock (1 vial, 25 mg) into 45 mL of 0.9% NaCl or 5% dextrose, final volume 50 mL Standard preparation for patients 3–10 kg. Uses one full vial of stock, straightforward to prepare and matches the most common dose range.

1000 µg/mL 10 mL stock (2 × 5 mL vials, 50 mg total) into 40 mL of 0.9% NaCl or 5% dextrose, final volume 50 mL Concentrated preparation for patients ≥10 kg or where fluid load matters. Most common ICU prep for medium-to-large dogs.

200 µg/mL 2 mL stock (10 mg) into 48 mL of 0.9% NaCl or 5% dextrose, final volume 50 mL Dilute preparation for patients <3 kg or any patient at very low doses where the 0.5 mg/mL preparation would drop pump rate below 2 mL/hr.

Awaiting input

Enter a patient weight to see the result.

Reference

How the calculation works

Midazolam CRI is dosed in mg/kg/hr. Because the prepared CRI concentration is expressed in µg/mL, the formula needs a × 1000 to convert the mg dose into µg before dividing:

$$\text{mL/hr} = \frac{\text{weight}_{\text{kg}} \times \text{dose}_{mg/kg/hr} \times 1000}{\text{concentration}_{\mu g/mL}}$$

Patient weight (kg) times dose (mg per kg per hour) gives mg per hour. Multiplying by 1,000 converts mg to µg so the units match the bag concentration. Dividing by µg/mL yields mL per hour.

In target-pump-rate mode the pump rate is fixed by the clinician and the bag concentration is the unknown. The preparation runs in three steps.

Step 1: bag concentration

Same numerator as standard-bag mode (the total drug delivered per hour for this patient), but divided by the chosen pump rate instead of by a chosen bag concentration:

$$\text{bag concentration}_{\mu g/mL} = \frac{\text{weight}_{\text{kg}} \times \text{dose}_{\mu g/kg/hr}}{\text{pump rate}_{\text{mL/hr}}}$$

Step 2: total drug in the bag

The bag concentration times the chosen bag volume gives the total micrograms of drug to add. Convert to milligrams (divide by 1,000) for the size of stock you'll actually be drawing:

$$\text{total drug}_{\mu g} = \text{bag concentration}_{\mu g/mL} \times \text{bag volume}_{\text{mL}}$$

$$\text{total drug}_{mg} = \frac{\text{total drug}_{\mu g}}{1{,}000}$$

Step 3: volume of stock to draw

Total drug divided by the stock vial concentration gives the volume of stock to draw and add to the bag:

$$\text{stock volume}_{\text{mL}} = \frac{\text{total drug}_{mg}}{\text{stock}_{mg/mL}}$$

Worked through together: divide the total drug in the bag by the stock vial's mg/mL to get the mL of stock that contains that much drug. That is the volume to pull into the syringe and add to the bag.

Worked example with current inputs

Enter a patient weight to see the worked example.

Reference

Recommended dilutions

Target concentration	Dilution	When useful
1000 µg/mL	10 mL stock (2 × 5 mL vials, 50 mg total) into 40 mL of 0.9% NaCl or 5% dextrose, final volume 50 mL	Concentrated preparation for patients ≥10 kg or where fluid load matters. Most common ICU prep for medium-to-large dogs.
500 µg/mL	5 mL stock (1 vial, 25 mg) into 45 mL of 0.9% NaCl or 5% dextrose, final volume 50 mL	Standard preparation for patients 3–10 kg. Uses one full vial of stock, straightforward to prepare and matches the most common dose range.
200 µg/mL	2 mL stock (10 mg) into 48 mL of 0.9% NaCl or 5% dextrose, final volume 50 mL	Dilute preparation for patients <3 kg or any patient at very low doses where the 0.5 mg/mL preparation would drop pump rate below 2 mL/hr.

Standard preparation is in a 50 mL syringe for syringe-pump delivery; the conventional ICU workflow for short-to-medium term sedation CRIs. For prolonged infusions (>24 hr) or concurrent IV fluid delivery, the same concentrations can be prepared in a 100 mL or 250 mL bag using proportionally more stock. Carrier fluid: 0.9% NaCl and 5% dextrose are both compatible (Plumb's). Midazolam is incompatible with sodium bicarbonate, ranitidine, and most alkaline solutions; do not co-administer in the same line. Photostability: midazolam is stable in standard ambient light. Refrigeration extends stability of compounded dilutions; discard syringe contents per facility policy (24 hours is a common cutoff for compounded benzodiazepine syringes).

Dilution helper — Midazolam CRI

Work out how many mL of stock drug and diluent to combine for any target concentration. Stock is pre-filled for Midazolam CRI; change it if you're using a different vial.

Stock concentration (µg/mL)

Desired concentration (µg/mL)

Suggestions from the reference table above

Final volume (mL)

Draw up

Enter stock, target concentration, and final volume.