What is the safety and efficacy of using ketamine (anesthetic) as a sedative option for a 2.5 kg infant undergoing Computed Tomography (CT) angiography?

Ketamine for Sedation in a 2.5 kg Infant Undergoing CT Angiography

Ketamine is safe and effective for sedating infants during CT imaging, including those as small as 2.5 kg, with a low rate of serious adverse events and high procedural success rates. 1, 2

Recommended Dosing Protocol for This Infant

Intravenous Route (Preferred)

• Administer 1.5 mg/kg IV ketamine as the initial dose, which provides effective sedation with only 5.5% of patients requiring additional doses compared to 54% with lower 1.0 mg/kg dosing 2
• For a 2.5 kg infant, this translates to approximately 3.75 mg IV ketamine
• Onset of action occurs within 30-96 seconds after IV administration 3

Intramuscular Route (Alternative)

• If IV access is difficult, use 4 mg/kg IM ketamine (10 mg for this infant) combined with 0.01 mg/kg atropine (0.025 mg), which produces sedation within 3-4 minutes 2, 4
• IM administration results in a lower incidence of emergence reactions compared to IV 5

Safety Profile Specific to Imaging Procedures

Respiratory Safety

• Ketamine demonstrates excellent respiratory safety for CT imaging, with transient desaturation occurring in only 7.5% of pediatric patients, most resolving spontaneously or with simple head positioning 1
• In a large cohort of 156 pediatric patients receiving IV ketamine, only 1 patient experienced apnea (with rapid IV infusion) and 1 required jaw thrust only, with no patients requiring assisted ventilation or intubation 1
• The FDA label notes that respiratory depression may occur with overdosage or rapid administration, emphasizing the need for adequate oxygenation monitoring 5

Cardiovascular Stability

• Ketamine maintains hemodynamic stability, making it particularly suitable for critically ill infants 1
• Continuous monitoring of vital signs including EKG, pulse oximetry, and blood pressure is required during administration 2

Procedural Success Rate

• Sedation failure rate is less than 1% for CT imaging with ketamine 1
• In comparative studies, 97% of patients were successfully scanned with pentobarbital, but ketamine shows similar or superior efficacy 1

Expected Recovery Timeline

• Mean recovery time is 82±33 minutes after a single IV dose, with median time to discharge of 103-110 minutes 2, 3
• 80% of patients exhibit quiet recovery behavior 3
• Recovery agitation occurs in approximately 17% (mild) and 1.6% (moderate-to-severe) of patients 3

Critical Safety Considerations for This Small Infant

Age-Related Neurotoxicity Concerns

• The FDA warns that ketamine may cause neuronal apoptosis in developing brains when used for longer than 3 hours, particularly in infants under several months of age 5
• For a single, brief CT angiography procedure (typically <30 minutes), this risk is minimal as the exposure duration is well below the 3-hour threshold 5
• The benefits of obtaining critical diagnostic imaging outweigh theoretical neurotoxicity risks for single-use procedural sedation 5

Airway Management Preparedness

• Have airway management equipment immediately available, including bag-valve-mask, appropriate-sized endotracheal tubes (likely 3.0-3.5 mm for a 2.5 kg infant), and suction 4
• Ketamine does not suppress pharyngeal and laryngeal reflexes, but laryngospasm can occur (reported in 8.2% overall, 14% in preschoolers in one series) 1, 5
• Most respiratory events respond to simple interventions without requiring intubation 1, 4

Fasting Status

• While traditional NPO guidelines recommend fasting, recent evidence shows that ketamine sedation within 2 hours of oral contrast intake resulted in higher vomiting rates (18% vs 1%) but no clinical aspiration or difference in hypoxia 6
• For urgent CT angiography in a critically ill infant, ketamine remains safe even if not fully NPO, though vomiting risk is elevated 6

Adjunctive Medication Considerations

Midazolam Co-Administration

• Consider adding midazolam 0.05 mg/kg IV (0.125 mg for this infant) to reduce emergence reactions, particularly if using IV route 2, 4
• Midazolam does not significantly increase respiratory complications when combined with ketamine (1.8% adverse event rate with ketamine/midazolam combination) 1
• The combination shows a strong trend toward less emesis 4

Atropine with IM Dosing

• Always administer atropine 0.01 mg/kg (0.025 mg for this infant) when using IM ketamine to reduce hypersalivation and optimize conditions 2

Common Side Effects to Anticipate

• Vomiting: 7-8% of patients 2
• Nausea: 4-5% 2
• Emesis without aspiration: 6.7% 3
• Dysphoria: 1% 2
• Emergence delirium: approximately 12% during recovery 5

Monitoring Requirements

• Continuous pulse oximetry throughout procedure and recovery 2, 5
• Regular blood pressure measurements 2
• EKG monitoring 2
• Maintain oxygen saturation >93% on room air 3
• Do not discharge until patient has returned to baseline mental status 4

Contraindications and Precautions

Relative Contraindications

• Elevated intracranial pressure (ketamine increases cerebrospinal fluid pressure and requires monitored setting with frequent neurologic assessments) 5
• Procedures of the pharynx, larynx, or bronchial tree where ketamine alone may be insufficient 5

Drug Interactions

• Avoid concomitant theophylline or aminophylline (may lower seizure threshold) 5
• Use caution with sympathomimetics or vasopressin (may enhance sympathomimetic effects of ketamine) 5

Advantages Over Alternative Sedatives for This Scenario

Ketamine is superior to alternatives like pentobarbital or midazolam alone for this clinical scenario because:

• Pentobarbital has longer recovery times (86 minutes vs 82 minutes) and requires higher doses 1
• Midazolam alone has only 19% procedural success for CT imaging compared to 97% with pentobarbital and similar rates with ketamine 1
• Propofol/fentanyl combinations show higher hypoxemia rates (24-31%) compared to ketamine/midazolam (6-7%) 4