From the Guidelines
The recommended dose of ketamine for dissociative anesthesia without paralysis is 1-2 mg/kg intravenously (IV) or 4-5 mg/kg intramuscularly (IM). This dosing is based on the most recent and highest quality evidence available, which prioritizes minimizing adverse effects while achieving the desired dissociative state 1. Administration should be slow, typically over 1-2 minutes for IV dosing, to minimize adverse effects. Onset of action is rapid, occurring within 30 seconds for IV administration and 3-4 minutes for IM administration, with a duration of action lasting approximately 10-20 minutes for IV and 15-30 minutes for IM.
Key Considerations
- Supplemental doses of half the initial amount may be given as needed to maintain the dissociative state.
- Ketamine works by blocking NMDA receptors in the brain, creating a dissociative state characterized by analgesia, amnesia, and sedation while preserving respiratory drive and protective airway reflexes.
- Patients should be monitored for potential side effects including emergence reactions (hallucinations, vivid dreams), increased blood pressure and heart rate, increased intracranial pressure, and excessive salivation.
Management of Side Effects
- Consider premedication with a benzodiazepine such as midazolam to reduce the incidence of emergence reactions.
- An antisialagogue like glycopyrrolate may be used to manage hypersalivation. It is crucial to weigh the benefits of ketamine against its potential risks and to carefully monitor patients during its administration, especially in settings where increased intracranial pressure or other contraindications may be a concern 1.
From the Research
Ketamine Dosage for Dissociation without Paralysis
The recommended dose of ketamine to provide dissociation without paralysis is not explicitly stated in the provided studies. However, some studies suggest the following:
- Ketamine is most commonly administered in the dose of 0.5 mg/kg, but some patients may respond to doses as low as 0.1 mg/kg, and others may require up to 0.75 mg/kg 2.
- A dose of 2 mg/kg of ketamine has been used in a study to induce dissociation and analgesia in healthy subjects 3.
- A dose of 0.5 mg/kg of ketamine has been used in a study to treat treatment-resistant depression, with dissociative symptoms assessed using the Clinician-Administered Dissociative States Scale (CADSS) 4.
- A dose of 0.5 mg/kg of racemic ketamine has been used in a study to assess the relationship between dissociation intensity and antidepressant effects in treatment-resistant depression 5.
Factors Influencing Ketamine-Induced Dissociation
Several factors can influence the intensity of ketamine-induced dissociation, including:
- Dose: Higher doses of ketamine may induce more intense dissociation 3, 5.
- Route of administration: The route of administration, such as intravenous or intramuscular, may affect the intensity of dissociation 2.
- Individual variability: Patients may respond differently to ketamine, with some experiencing more intense dissociation than others 2, 4.
- Context: The context in which ketamine is administered, such as in a clinical or therapeutic setting, may influence the intensity of dissociation 6.
Relationship between Dissociation and Antidepressant Effects
Some studies suggest a positive relationship between the intensity of ketamine-induced dissociation and antidepressant effects:
- A study found that for every 1-point increment in the CADSS score, there was a mean change of -0.5 (SD = 0.25; p-value 0.04) of predicted MADRS score from baseline to 24 hrs 5.
- Another study found that the abatement of dissociation was observed in time with no sequelae nor harm, but no significant association between dissociation and treatment outcome was found 4.