What is the duration of action of ketamine (intravenous anesthetic) in pediatric patients?

Duration of Action of Ketamine in Pediatric Patients

Intravenous ketamine has a short duration of action of 15-30 minutes, with rapid onset within 1 minute, making it ideal for brief pediatric procedures. 1

Pharmacokinetic Profile

IV ketamine demonstrates a biphasic elimination pattern:

• Initial alpha phase: Lasts approximately 45 minutes with a half-life of 10-15 minutes, corresponding to the clinical anesthetic effect 2
• Beta phase (redistribution): Half-life of 2.5 hours as the drug redistributes from the CNS to peripheral tissues 2

The rapid onset (30-96 seconds) allows for immediate procedural intervention, while the short duration of action (15-30 minutes) provides adequate sedation for most brief pediatric procedures 1, 3

Clinical Recovery Times

Actual recovery times in pediatric patients are longer than the pharmacologic duration of action:

• Mean recovery time: 82±33 minutes for single IV dose 1, 3
• Median recovery time: 103 minutes (interquartile range: 76-146 minutes) 1
• Range: 22-215 minutes depending on total dose administered 3
• Average total sedation time: 75-78 minutes 3

Approximately 80% of pediatric patients exhibit quiet recovery behavior, with 17% experiencing mild agitation and only 3% showing moderate agitation 1

Route-Specific Considerations

Intramuscular administration:

• Onset of action: 3-4 minutes (slower than IV) 3, 4
• Recovery time: Approximately 90 minutes, similar to IV route 3
• Time from drug administration to discharge: 21 minutes longer compared to IV route 5

The IM route provides comparable total sedation duration but with delayed onset and slightly prolonged recovery compared to IV administration. 5

Dosing Impact on Duration

Higher doses prolong the duration of sedation:

• Standard dose (1.5-2 mg/kg IV): Only 5.5% require additional doses 3
• Lower dose (1.0 mg/kg IV): 54% require supplemental dosing 3
• Single large bolus: Associated with deeper sedation and delayed recovery (up to 70 minutes to reach drowsy state) 6

A critical pitfall is using excessive initial dosing, which significantly prolongs recovery without improving procedural conditions. 6

Factors Affecting Recovery Duration

Recovery agitation is associated with:

• Higher ASA status (>I) 3
• Decreasing age (younger children more prone to agitation) 3

Emesis (occurring in 6.7% of cases) is associated with:

• Increasing age (older children more prone to nausea/vomiting) 1, 3

Discharge Criteria

Patients should not be discharged until:

• Return to baseline mental status 4
• Stable vital signs maintained 1, 3
• Adequate airway reflexes restored 1

The median time from ketamine administration to actual discharge readiness is 110 minutes for single IM dose, though this includes observation time beyond pharmacologic recovery 1

Combination Therapy Effects

Adding midazolam (0.05-0.1 mg/kg) to ketamine:

• Does not significantly alter recovery time 3
• May reduce emergence reactions in children over 10 years old 3
• Shows mixed evidence for reducing overall agitation 3

The 15-30 minute duration of action makes ketamine particularly suitable for brief painful procedures like laceration repair, fracture reduction, and foreign body removal, with full recovery and discharge typically occurring within 90-110 minutes. 1, 3