What is the induction agent of choice in a patient with raised Intracranial Pressure (ICP)?

Etomidate is the Induction Agent of Choice for Patients with Raised Intracranial Pressure

Etomidate is the preferred induction agent for patients with raised intracranial pressure (ICP) due to its ability to decrease ICP while maintaining hemodynamic stability and cerebral perfusion pressure. 1, 2, 3

Mechanism and Benefits of Etomidate in Raised ICP

• Etomidate reduces ICP by approximately 26-27% for more than 10 minutes following administration 4, 5
• Unlike thiopental and other induction agents, etomidate maintains mean arterial pressure and cerebral perfusion pressure (CPP) 3, 5
• Onset of action is rapid (5-15 seconds) with short duration (5-15 minutes), allowing for quick neurological assessment after intubation 2
• Cerebroprotective effects include ability to decrease ICP while maintaining cerebral perfusion 2

Dosing and Administration

• Standard induction dose: 0.3 mg/kg IV administered over 15-20 seconds 6
• For patients with severe cardiovascular disease, doses up to 0.6 mg/kg have minimal effect on myocardial metabolism, cardiac output, and circulation 6
• Consider pre-treatment with fentanyl (0.1 mg IV) 1-2 minutes before induction to reduce etomidate requirement 6

Advantages Over Other Induction Agents

• Unlike thiopental, propofol, and midazolam, etomidate has minimal respiratory or cardiovascular depression 2
• Thiopental causes significant reduction in blood pressure, which can compromise CPP in patients with raised ICP 4, 5
• Ketamine is contraindicated as it causes prolonged increase in ICP with reduction in blood pressure and CPP 4
• Propanidid induces fluctuations in ICP and blood pressure, making it less suitable 4

Special Considerations

Hemodynamic Management

• Etomidate is particularly valuable in geriatric patients with hypertension, where it may cause less hemodynamic instability than other agents 6
• For hypotensive patients, etomidate is preferred as it maintains blood pressure better than alternatives 2

Potential Side Effects

• Transient adrenal suppression (6-8 hours) may occur but is not clinically significant with single induction doses 6, 2
• Other potential side effects include pain on injection, myoclonic movements, hiccups, nausea, and vomiting 2
• Continuous infusion is not recommended due to risk of prolonged adrenal suppression and propylene glycol toxicity 7

Additional Management for Raised ICP

While etomidate is the preferred induction agent, comprehensive management of raised ICP should include:

• Head elevation to 30° to improve jugular venous outflow 1
• Adequate analgesia and sedation (propofol, midazolam for sedation; morphine or alfentanil for analgesia) 1
• Consider osmotic therapy with mannitol or hypertonic saline for persistent elevated ICP 1
• Target ventilation to PaO₂ ≥13 kPa and PaCO₂ 4.5-5.0 kPa 8
• Avoid hyperventilation except for temporary management of acute herniation 1

Conclusion

Etomidate provides the optimal balance of ICP reduction while maintaining hemodynamic stability and cerebral perfusion pressure, making it the induction agent of choice for patients with raised ICP. Its favorable safety profile and minimal cardiovascular effects make it particularly suitable for this vulnerable patient population.