Ketamine in Prehospital Care
Ketamine is a dissociative anesthetic that has become one of the most versatile medications in the prehospital pharmacology toolkit. At sub-dissociative doses, it provides powerful analgesia. At higher doses, it produces procedural sedation. It is also used for managing severe agitation and excited delirium. Understanding the different applications and dosing strategies is important for paramedic-level providers.
Mechanism of Action
Ketamine primarily blocks NMDA (N-methyl-D-aspartate) receptors in the central nervous system, producing dissociation between the thalamus and the limbic system. This creates a trance-like state with profound analgesia, amnesia, and sedation while generally preserving airway reflexes, respiratory drive, and hemodynamic stability. Unlike opioids, ketamine does not cause respiratory depression at analgesic doses and does not lower blood pressure.
Pain Management Dosing
For analgesia (sub-dissociative ketamine):
- IV: 0.1 to 0.3 mg/kg administered slowly over 1 to 2 minutes. May repeat every 15 to 20 minutes.
- IM: 0.5 to 1 mg/kg. Onset is slower (3 to 5 minutes) but useful when IV access is not available.
- IN (intranasal): 0.5 to 1 mg/kg. Provides non-invasive analgesic administration, particularly useful in pediatric patients.
Agitation and Sedation Dosing
For severe agitation or excited delirium:
- IM: 4 to 5 mg/kg. This is the preferred route when IV access is not established in a combative patient.
- IV: 1 to 2 mg/kg administered over 1 minute when IV access is available.
Safety Considerations
While ketamine has a favorable safety profile, providers must be aware of potential adverse effects. Emergence reactions (vivid dreams, confusion, or agitation upon waking) occur in approximately 10 to 20% of adult patients. Coadministration of a benzodiazepine can reduce this risk. Hypersalivation may occur and can be managed with suctioning. Laryngospasm is rare but possible, especially in pediatric patients. At dissociative doses, providers must be prepared for airway management.
Monitor the patient closely after ketamine administration. Have airway equipment, suction, and monitoring equipment immediately accessible. Document the indication, dose, route, time, and patient response. Follow your local protocols for approved indications and dosing ranges.