What ketamine loading dose and intra‑operative infusion rate should be used in a healthy pediatric patient undergoing surgery without a muscle relaxant?

Ketamine Infusion Dosing for Intraoperative Pediatric Surgery Without Muscle Relaxant

For healthy pediatric patients undergoing surgery without muscle relaxants, administer a loading dose of ketamine 0.5 mg/kg IV (or 0.25-0.5 mg/kg if using S-ketamine), followed by a continuous infusion of 0.1-0.2 mg/kg/h (maximum 0.4 mg/kg/h) until the end of the procedure. 1

Dosing Algorithm

Loading Dose

• Racemic ketamine: 0.5 mg/kg IV bolus 1
• S-ketamine: 0.25-0.5 mg/kg IV bolus (reduced dose due to increased potency) 1
• Administer after anesthesia induction to prevent psychodysleptic side effects

Maintenance Infusion

• Standard rate: 0.1-0.2 mg/kg/h 1
• Maximum rate: 0.4 mg/kg/h 1
• Continue until the end of the procedure
• This dosing is intended as an adjunct to other anesthetic agents, not as sole anesthetic

Clinical Context and Rationale

The 2024 European Society for Paediatric Anaesthesiology (ESPA) guidelines provide the most current and authoritative dosing recommendations for intraoperative ketamine use in children 1. These doses are specifically designed for ketamine's role as a co-analgesic adjunct during surgery, providing anti-hyperalgesic effects and reducing opioid requirements.

When Ketamine is Particularly Indicated

While the guidelines support ketamine as an adjunct option for most procedures, it is especially valuable in:

• Surgery with high risk of acute or chronic postoperative pain
• Patients with vulnerability to pain
• Patients on long-term opioids or with opioid addiction 2

Important Caveats and Safety Considerations

Cardiovascular Effects

Ketamine produces dose-dependent increases in heart rate, blood pressure, and cardiac output through sympathetic stimulation 3. Avoid or use with extreme caution in patients with:

• Ischemic heart disease
• Cerebrovascular disease
• Uncontrolled hypertension

Airway Management

• Ketamine preserves airway reflexes better than other sedatives 3
• However, laryngospasm can occur, with incidence of 0.9-1.4% in most studies 4
• One study in gastroenterology procedures showed 8.2% incidence, particularly in children <6 years (13.9% vs 3.6% in older children) 4
• Always have appropriate airway equipment and resuscitation capabilities immediately available

Emergence Reactions

• Emergence reactions (floating sensations, vivid dreams, hallucinations, delirium) occur in 10-30% of adults 3
• Co-administration with midazolam minimizes this reaction 3
• Less common in pediatric patients but still possible

Neurodevelopmental Concerns

The FDA label warns that repeated or prolonged use of anesthetic drugs in children <3 years may negatively affect developing brains 5. While this applies to all anesthetics, discuss risks and benefits with parents/caregivers, particularly for prolonged procedures.

Alternative Dosing for Specific Scenarios

For Anesthesia Induction Without Muscle Relaxants

If ketamine is being used as the primary induction agent (different from the co-analgesic role above):

• 2 mg/kg IV provides adequate conditions when combined with appropriate remifentanil dosing 6
• This higher dose is associated with better intubation conditions and less chest wall rigidity compared to lower ketamine doses requiring higher remifentanil 6

For Prolonged Infusions (>2 hours)

Research suggests age-adjusted infusion rates for maintaining steady-state concentrations of 3 mg/L (anesthetic level) 7:

• Loading: 2 mg/kg
• 0-20 min: 11 mg/kg/h
• 20-40 min: 7 mg/kg/h
• 40-60 min: 5 mg/kg/h
• 1-2 hours: 4 mg/kg/h

However, these higher rates are for ketamine as a primary anesthetic and exceed guideline recommendations for adjunctive use. The ESPA guideline doses (0.1-0.2 mg/kg/h) are more appropriate for routine surgical adjunct use.

Postoperative Considerations

• Do not continue ketamine infusion postoperatively for routine cases, as this increases hallucination risk without significant additional analgesic benefit 2
• For breakthrough pain in PACU: 0.5 mg/kg IV ketamine (or 0.25-0.5 mg/kg S-ketamine), titrated to effect 1
• Advise patients/families that residual effects may persist; avoid hazardous activities for 24 hours 5

Monitoring Requirements

• Continuous pulse oximetry
• Blood pressure and heart rate monitoring
• Capnography when available (though one small study showed no hypoventilation with ketamine sedation) 4
• Appropriate resuscitation equipment immediately available
• Personnel trained in pediatric airway management present