About This Calculator

The Ketamine Infusion calculator is a clinical support tool designed for healthcare professionals to determine appropriate intravenous (IV) ketamine dosing regimens for various clinical indications. It calculates the total bolus dose, infusion pump rate, and provides a titration table based on patient weight, desired dose, and IV solution concentration.

This tool is intended for educational and informational purposes only and is not a substitute for professional clinical judgment, institutional protocols, or direct patient evaluation. All calculations must be independently verified prior to drug administration.

Outputs Explained

After entering the required patient and dosing information, the calculator provides the following key outputs:

• Total Bolus Dose (mg): The total mass of ketamine to be administered as a loading dose.
• Volume to Administer (mL): The volume of the prepared IV solution required to deliver the calculated bolus dose.
• Infusion Rate (mg/hr): The total mass of ketamine to be delivered per hour via continuous infusion.
• Pump Rate (mL/hr): The rate at which the infusion pump should be set to deliver the desired dose, based on the specified IV solution concentration.
• Bedside Titration Table: A convenient reference table showing pump rates (mL/hr) for doses slightly above and below the target infusion rate, facilitating quick adjustments based on patient response.

How to Use the Tool

Follow these steps to perform a calculation:

1. Enter Patient Weight: Input the patient's weight and select the unit (kg or lbs).
2. Select Dosing Weight Basis: Choose "Actual Body Weight" (ABW) or "Ideal Body Weight" (IBW). If IBW is selected, you must also enter the patient's height and sex to calculate it. IBW is often considered for obese patients to avoid potential overdose.
3. Choose Clinical Indication: Select the primary reason for ketamine administration (e.g., Analgesia, Procedural Sedation). This will populate typical dosing ranges as a reference.
4. Define Dosing Regimen: Check whether a loading dose (bolus) and/or a continuous infusion will be administered.
5. Input Dose Parameters: Enter the desired bolus dose (in mg/kg) and/or infusion dose (in mcg/kg/min or mg/kg/hr).
6. Set IV Solution Concentration: Specify the amount of ketamine (in mg) and the total volume of the carrier fluid (in mL). You can use a common preset or enter custom values.

The results will update in real-time as you enter the data.

Dosing Overview

Ketamine dosing varies significantly based on the intended therapeutic effect, ranging from sub-dissociative doses for analgesia to fully dissociative doses for procedural sedation or induction.

• Analgesia (Sub-dissociative): Typically involves a small bolus (e.g., 0.1-0.3 mg/kg) followed by a low-dose infusion (e.g., 1-10 mcg/kg/min). The goal is pain control without significant psychomimetic side effects.
• Procedural Sedation (Dissociative): Requires a larger IV bolus (e.g., 1-2 mg/kg) to induce a trance-like state of consciousness while maintaining spontaneous respirations and protective airway reflexes.
• Rapid Sequence Intubation (RSI): A standard induction dose (e.g., 1-2 mg/kg) is used for its rapid onset and favorable hemodynamic profile, especially in hypotensive patients.
• Status Asthmaticus: A bolus followed by a continuous infusion (e.g., 0.5-2.5 mg/kg/hr) is used for its bronchodilatory properties in severe, refractory cases.

Switching & Adjuvant Therapy

Ketamine is frequently used as an adjunct to traditional analgesics like opioids, often with an opioid-sparing effect. When initiating a ketamine infusion for pain, it is common practice to reduce the dose of concurrent opioids by 25-50% to minimize the risk of respiratory depression and excessive sedation. Close monitoring is essential during this transition. When discontinuing a ketamine infusion, doses should be tapered gradually over several hours, if administered for a prolonged period, to prevent withdrawal or rebound pain.

Missed or Interrupted Dose

For continuous infusions used in critical care or pain management, an interruption in therapy can lead to a rapid decline in plasma concentration due to ketamine's short half-life. If an infusion is stopped for a short period (e.g., < 30 minutes), it can typically be resumed at the previous rate. For longer interruptions, a clinician may consider administering a small re-bolus dose (e.g., 25-50% of the initial loading dose) before restarting the infusion to quickly re-establish a therapeutic level. This decision must be based on the patient's clinical status, including level of sedation and pain score.

Safety Alerts

Frequently Asked Questions (FAQ)

When should I use Ideal Body Weight (IBW) versus Actual Body Weight (ABW)?

For obese patients, dosing based on ABW can lead to excessive dosage as ketamine is lipophilic. Using IBW (or an adjusted body weight) is often recommended to prevent overdose and reduce side effects. The decision should be guided by institutional protocol and clinical judgment.

Why does the calculator ask for height and sex?

Height and sex are required to calculate the Ideal Body Weight (IBW) using standard formulas (e.g., Devine formula). This information is only necessary if you select the "Use Ideal Body Weight" option.

What is the difference between mcg/kg/min and mg/kg/hr?

These are two different units for expressing an infusion rate. The calculator allows you to input the dose in either unit and handles the conversion automatically. 1 mg/kg/hr is approximately equivalent to 16.7 mcg/kg/min.

Why are the dosing ranges so wide for some indications?

Ketamine dosing must be individualized. The appropriate dose depends on patient age, comorbidities, concurrent medications (especially sedatives), and the desired level of sedation or analgesia. The provided ranges represent common starting points.

Can this calculator be used for Intramuscular (IM) dosing?

No, this calculator is designed specifically for IV bolus and continuous infusion administration. IM doses are typically higher (e.g., 4-5 mg/kg for procedural sedation) and have a different onset and duration of action.

What does "sub-dissociative" dosing mean?

This refers to using ketamine at low doses that provide potent analgesia without causing the profound detachment from reality ("dissociation") seen at higher anesthetic doses. This is the goal for most pain management applications.

How should an infusion be prepared?

Aseptically add the required amount of ketamine from a vial to a compatible IV fluid (e.g., 0.9% Sodium Chloride or 5% Dextrose in Water). The calculator helps determine the final pump rate based on the concentration of this mixture.

What are common IV solution concentrations?

Common concentrations for ketamine infusions are 1 mg/mL (e.g., 100 mg in 100 mL) or 2 mg/mL (e.g., 200 mg in 100 mL). Higher concentrations may be used for fluid-restricted patients.

References

1. U.S. Food and Drug Administration. (2020). KETALAR (ketamine hydrochloride) injection, for intravenous or intramuscular use. Prescribing Information. Link to FDA Label
2. Schwenk, E. S., et al. (2018). Consensus Guidelines on the Use of Intravenous Ketamine Infusions for Acute Pain Management From the American Society of Regional Anesthesia and Pain Medicine, the American Academy of Pain Medicine, and the American Society of Anesthesiologists. Regional Anesthesia and Pain Medicine, 43(5), 456–466. doi:10.1097/AAP.0000000000000806
3. Bell, R. F., & Kalso, E. A. (2013). Ketamine for pain management. Pain Reports, 1(1), e554. doi:10.1097/PR9.0000000000000018
4. American College of Emergency Physicians. (2014). Clinical Policy: Procedural Sedation and Analgesia in the Emergency Department. Annals of Emergency Medicine, 63(2), 247-258.e18. Link to ACEP Policy