What is the recommended dose of ketamine (Ketamine) for maintaining sedation?

Ketamine Dosing for Maintaining Sedation

For maintaining procedural sedation, administer IV ketamine at 1.5-2 mg/kg as the initial dose, with additional aliquots of 0.25-0.5 mg/kg as needed to maintain adequate sedation depth throughout the procedure. 1

Initial Dosing Strategy

Intravenous Route (Preferred for Maintenance)

• Start with 1.5-2 mg/kg IV for optimal sedation maintenance, as this dose requires significantly fewer supplemental doses compared to lower dosing 2, 1, 3
• Only 5.5% of patients require additional ketamine when initially dosed at 1.5 mg/kg, compared to 54% requiring supplementation at 1.0 mg/kg 2, 1
• Onset of action occurs within 30-96 seconds, allowing rapid assessment of sedation adequacy 1

Intramuscular Route (Alternative)

• Use 4 mg/kg IM when IV access is unavailable or impractical 2, 1, 4
• Onset occurs within 3-4 minutes 4
• Repeat doses of 2-4 mg/kg IM may be given after 5-10 minutes if sedation is inadequate 1

Maintenance Dosing During Procedures

Supplemental Dosing Protocol

• Administer 0.25-0.5 mg/kg IV aliquots when sedation begins to lighten during the procedure 5
• Reassess sedation depth after each supplemental dose before administering additional ketamine 5
• Maximum cumulative dose should not exceed 2.0 mg/kg during a single sedation session 5

Avoiding Under-Dosing

• Starting with 1.0 mg/kg results in higher total cumulative doses (median 1.71 mg/kg) compared to starting with 1.5 mg/kg (median 1.60 mg/kg) due to frequent need for supplementation 3
• 18.5% of patients require a third dose when starting at 1.0 mg/kg versus only 7.6% when starting at 1.5 mg/kg 3

Combination Therapy Considerations

Ketamine with Midazolam

• Consider adding midazolam 0.05-0.1 mg/kg IV to ketamine for potentially reduced emergence reactions, though evidence is mixed on efficacy for reducing agitation 2, 1
• The combination of 1-2 mg/kg ketamine with 0.05-0.1 mg/kg midazolam provides effective sedation with 100% procedure completion rates 2
• For patients >10 years old, adding midazolam significantly reduces recovery agitation (5.7% vs 35.7% with ketamine alone) 2

Ketamine with Propofol

• Low-dose ketamine (0.25-0.5 mg/kg) combined with propofol reduces total propofol requirements (0.28 vs 0.40 mg/kg/min) and shortens recovery time by 5 minutes 6

Duration and Recovery Expectations

Sedation Duration

• Average total sedation time is approximately 75-78 minutes with IV ketamine 2
• Recovery time averages 84 minutes (range 22-215 minutes) for IV administration 2, 1
• IM administration results in similar recovery times of approximately 90 minutes 2

Critical Monitoring Requirements

Continuous Monitoring Mandates

• Maintain continuous pulse oximetry, heart rate, blood pressure, and capnography (when available) throughout sedation 1, 4
• Ensure oxygen saturation remains >93% on room air 1
• Have bag-valve-mask ventilation equipment immediately available 4
• Maintain IV access throughout the procedure until cardiorespiratory depression risk has resolved 7

Cardiovascular Effects

• Expect dose-dependent increases in heart rate (18%) and blood pressure (13%) due to sympathetic stimulation 2, 1
• New ECG ischemic changes occur in approximately 9.7% of adults >50 years, though typically without clinical significance 8

Safety Profile and Adverse Events

Common Side Effects

• Recovery agitation occurs in 17.6% of patients (1.6% moderate-to-severe) 1, 4
• Emesis without aspiration in 6.7% of cases 1, 4
• Dysphoric emergence in 10-20% of cases 4

Respiratory Safety

• Hypoxemia (SpO2 <90%) occurs in 1.6-7.3% of patients, typically transient and responsive to supplemental oxygen 2
• Laryngospasm is rare (0.9-1.4% of cases) 4
• Bag-valve-mask ventilation required in approximately 2% of cases 2

Absolute Contraindications

Avoid ketamine in patients with: 1, 4

• Uncontrolled cardiovascular disease or ischemic heart disease
• Cerebrovascular disease or uncontrolled hypertension
• Active psychosis
• Severe hepatic dysfunction
• Elevated intracranial or intraocular pressure
• Pregnancy

Key Clinical Pitfalls to Avoid

• Do not start with 1.0 mg/kg IV thinking you'll save medication—this approach paradoxically results in higher total doses and more frequent supplementation 3
• Do not administer supplemental doses too quickly—allow adequate time (2-3 minutes) to assess sedation depth after each dose 5
• Do not continue ketamine infusions into the postoperative period as this increases hallucination risk without enhancing analgesia 7
• Do not use in patients with cardiac disease without careful consideration of the sympathomimetic effects and potential for myocardial oxygen demand increase 1, 4, 8