What are the uses, indications, contraindications, and potential side effects of ketamine in a pre-hospital context?

Ketamine in Pre-Hospital Context

Primary Indications

Ketamine is an ideal drug for pre-hospital use due to its unique combination of analgesia, sedation, and relative hemodynamic stability without causing respiratory depression or hypotension, making it particularly valuable for trauma patients and combative or agitated patients requiring procedural sedation. 1

Specific Pre-Hospital Uses:

• Analgesia for trauma patients, particularly when hypotension is present or opioids are insufficient 2, 3
• Rapid sequence induction (RSI) for pre-hospital emergency anesthesia (PHEA), especially in trauma settings 1, 4
• Sedation of combative or agitated patients when intravenous access is difficult or unavailable 1, 2
• Procedural sedation for fracture reductions, wound repairs, and other painful procedures 1
• Intramuscular administration when IV access cannot be established, as ketamine does not cause respiratory or cardiovascular collapse 1

Dosing in Pre-Hospital Settings

Intravenous Route:

• Induction/RSI: 1.5-2 mg/kg IV 1
• Analgesia: 0.5 mg/kg IV bolus 5, 2
• Onset: Approximately 96 seconds (range 20 seconds to 5 minutes) 1

Intramuscular Route:

• Sedation/analgesia: 2.5-4 mg/kg IM 1
• Onset: Approximately 4-5 minutes (range 1-15 minutes) 1
• Use when IV access unavailable, particularly in combative patients 1

Contraindications

Absolute Contraindications (FDA):

• Patients for whom significant elevation of blood pressure would constitute a serious hazard 6, 7
• Known hypersensitivity to ketamine or any excipient 6, 7

Relative Contraindications/Cautions:

• Severe cardiac disease or recent cardiac arrest: The sympathomimetic effects may be disadvantageous after resuscitation from cardiac arrest 1, 4
• Uncontrolled cardiovascular disease, ischemic heart disease, cerebrovascular disease, or hypertension 4, 5
• Active psychosis 4
• Severe liver dysfunction 4
• High ocular pressure 4

Important Note on Head Injury:

• Historical concerns about ketamine increasing intracranial pressure are of little practical significance 1, 4
• Ketamine is now frequently used in PHEA for patients with head injury and does not worsen outcomes in traumatic brain injury 1, 4

Potential Side Effects

Common Side Effects:

• Emergence reactions (10-30% in adults): Floating sensations, vivid dreams, hallucinations, delirium 4

  • Can be minimized with co-administration of benzodiazepines (e.g., midazolam 0.05-0.1 mg/kg) 1, 4

• Emesis/nausea: 7-19% of patients 1, 3

• Increased salivation: Can be managed with anticholinergics (atropine or glycopyrrolate) 1

• Transient ataxia: 7-8% of patients, lasting 0.5-2 hours 1

• Cardiovascular stimulation: Dose-dependent increases in heart rate (approximately 18%), blood pressure, and cardiac output 1, 4

Serious Adverse Effects (Rare):

• Respiratory depression: Significantly less common than with opioids or benzodiazepines 8, 3
• Hypotension: May occur paradoxically in critically ill or septic patients where sympathetic reserves are depleted 4
• Laryngospasm: Rare but possible 8

Key Advantages in Pre-Hospital Setting

• Maintains airway reflexes and spontaneous ventilation 8, 3
• Preserves hemodynamic stability through sympathomimetic effects, making it superior to other sedatives in shock states 1, 4, 5
• Can be administered IM when IV access unavailable 1, 2
• Provides both analgesia and amnesia 8
• Does not prolong emergency department length of stay compared to morphine or fentanyl 9
• Fewer side effects than morphine when used alone 3

Critical Pitfalls to Avoid

• Do not assume hemodynamic stability in all patients: In septic or critically ill patients with depleted catecholamine stores, ketamine may cause hypotension rather than hypertension 4
• Always have airway management equipment immediately available, though respiratory depression is rare 8
• Consider co-administration of benzodiazepines to minimize emergence reactions, especially in adults 1, 4
• Avoid in patients with severe uncontrolled hypertension or acute coronary syndromes where sympathetic stimulation could be harmful 4, 6, 7
• Monitor for excessive salivation and consider anticholinergic pretreatment 1

Recovery and Transport Considerations

• Recovery time: 75-90 minutes average for both IV and IM routes 1
• Continuous monitoring required during transport: ECG, blood pressure, pulse oximetry, and capnography 1
• Maintain sedation during transport with small frequent doses to minimize hemodynamic side effects 1
• ED LOS is not prolonged compared to traditional opioid analgesics 9