Ketamine Use in Patients with Intracranial Hypertension
Ketamine is safe and effective for use in patients with intracranial hypertension and should not be avoided based on outdated concerns about increasing intracranial pressure (ICP). 1, 2
Historical Concerns vs. Current Evidence
The traditional contraindication of ketamine in patients with elevated ICP originated from inadequately controlled early studies and case reports 3. Modern evidence demonstrates that these concerns are of little practical significance, and ketamine is now frequently used in pre-hospital emergency anesthesia for patients with head injury 1, 2.
Key Evidence Supporting Ketamine Use:
Ketamine actually decreases ICP by approximately 30% (from 25.8 ± 8.4 to 18.0 ± 8.5 mm Hg, p < 0.001) in mechanically ventilated pediatric patients with intracranial hypertension 4
Meta-analysis confirms ketamine does not increase ICP compared to opioids (MD = 1.94; 95% CI, -2.35,6.23; P = 0.38) 5
Ketamine boluses reduce ICP by median -3.5 mmHg (IQR -9 to +1, p < 0.001) in severe traumatic brain injury patients with refractory intracranial hypertension 6
Clinical Advantages in Intracranial Hypertension
Ketamine offers unique hemodynamic benefits that make it particularly valuable for patients with brain injury:
Maintains or increases cerebral perfusion pressure (CPP) by +2 mmHg (IQR -5 to +12, p < 0.001), unlike other sedatives that commonly cause hypotension 4, 6
Provides relative hemodynamic stability through sympathomimetic effects, making it an attractive induction agent for trauma care 1, 2
Does not depress blood pressure, unlike opioids, benzodiazepines, propofol, and barbiturates which all decrease CPP 4
Recommended Dosing and Administration
For induction in hemodynamically unstable patients with head injury: 1-2 mg/kg IV 7
For sedation boluses in refractory ICP: 1-1.5 mg/kg IV 4
For postoperative pain management: Boluses <0.35 mg/kg or infusions at 0.5-1 mg/kg/h 1
Critical Requirements for Safe Use
Ketamine should only be used in patients with intracranial hypertension when:
- Patient is mechanically ventilated with controlled ventilation 4, 3
- Adequate sedation is maintained (ketamine works best in combination with other sedative agents) 3
- Patient is in a monitored setting with frequent neurologic assessments 8
- PaCO2 is maintained at 4.5-5.0 kPa (35-40 mmHg) and PaO2 ≥13 kPa or oxygen saturation ≥95% 7
Absolute Contraindications from FDA Label
Do not use ketamine in patients with:
- Elevated intracranial pressure who are NOT in a monitored setting 8
- Uncontrolled cardiovascular disease 1
- Active psychosis 1
- Severe liver dysfunction 1
- High ocular pressure 1
Important Caveats
The FDA label states that ketamine increases cerebrospinal fluid pressure 8, which appears contradictory to clinical trial data. This discrepancy reflects outdated labeling that has not been updated to reflect modern evidence. The guideline evidence and multiple clinical trials consistently demonstrate ICP reduction, not elevation 1, 4, 5, 6.
Ketamine's sympathomimetic effects may be disadvantageous after resuscitation from cardiac arrest or in patients with severe cardiac disease 1. The drug produces dose-dependent increases in heart rate, blood pressure, and cardiac output 1, 2.
Emergence reactions occur in 10-30% of adults, manifesting as floating sensations, vivid dreams, hallucinations, and delirium 1. Co-administration with midazolam minimizes this reaction 1.
Clinical Outcomes
Patients receiving ketamine for intracranial hypertension demonstrate lower mortality rates after injury stratification compared to other sedative agents 9. Ketamine administration was not associated with worse survival or disability in traumatic brain injury patients 2.