RSI Agents to Avoid in Increased ICP
In patients with increased intracranial pressure, avoid all inhalational anesthetic gases (halothane, enflurane, isoflurane, and nitrous oxide) as they consistently increase ICP through cerebral vasodilation, and exercise caution with succinylcholine due to transient ICP elevation, though the clinical significance remains debated.
Inhalational Gases - Absolute Avoidance
All volatile anesthetic agents and nitrous oxide should be avoided in patients with elevated or suspected elevated ICP:
- Halothane, enflurane, and nitrous oxide cause consistent and significant ICP increases during both induction and maintenance phases 1, 2
- These agents work by causing cerebral vasodilation, which increases intracranial blood volume and subsequently raises ICP 3, 4
- Even with controlled hyperventilation (PaCO2 25 mmHg), ICP elevations persist and do not return to baseline within 5 minutes 2
- Nitrous oxide specifically causes both ICP elevation AND a 16% reduction in blood pressure, creating a dangerous combination that reduces cerebral perfusion pressure below critical thresholds (sometimes <40 mmHg) 1
- Isoflurane in normocapnia causes ICP increases and concurrent MAP reductions, further compromising cerebral perfusion pressure 3
The evidence is clear and consistent across multiple studies: inhalational anesthetics should not be used when decreased intracranial compliance exists or cannot be excluded 5, 4.
Neuromuscular Blocking Agents - Nuanced Approach
Succinylcholine - Use with Caution
The concern with succinylcholine centers on transient ICP elevation, but the clinical significance is controversial:
- One retrospective study in traumatic brain injury patients showed increased mortality with succinylcholine in high-severity TBI (OR 4.1; 95% CI, 1.2-14.1) 6
- However, this was very low-quality evidence due to retrospective design and selection bias 6
- Recent evidence suggests rocuronium may be safer than succinylcholine in TBI patients requiring intubation 7
Rocuronium - Preferred Alternative
Rocuronium (1.2 mg/kg) is the preferred paralytic in patients with increased ICP 6, 7:
- Provides equivalent first-pass success rates to succinylcholine 6
- Avoids the transient ICP elevation associated with succinylcholine
- The previous concern about prolonged paralysis preventing neurologic examination is now mitigated by sugammadex availability 7
- The 2023 SCCM guidelines suggest either agent when no contraindications exist, but the TBI-specific data favors rocuronium 6
Induction Agents - Safe Options
The following induction agents are acceptable in increased ICP:
- Etomidate or thiopental are specifically recommended for anesthesia induction in acute intracranial hypertension 5
- Ketamine is acceptable despite historical concerns about ICP elevation (these concerns have been largely refuted in modern practice)
- Propofol can be used but has the most profound hypotensive effect, which may compromise cerebral perfusion pressure 6
Barbiturates (small doses) and narcotics are considered useful and do not increase ICP 4.
Critical Pitfalls
- Never assume normal ICP - if you cannot exclude raised ICP, avoid all inhalational agents 4
- Maintain cerebral perfusion pressure - the combination of ICP-raising agents with hypotension-inducing agents creates a dangerous scenario where CPP falls below critical levels
- Hyperventilation alone is insufficient - while moderate hyperventilation helps, it does not prevent ICP increases from volatile agents 2
- Benzodiazepines (particularly midazolam at RSI doses) cause venodilation and have slower onset, making them less desirable though not contraindicated 6
Recommended Algorithm for ICP Patients
- Paralytic choice: Rocuronium 1.2 mg/kg (preferred) or succinylcholine 1 mg/kg if rocuronium unavailable
- Induction agent: Etomidate or ketamine (avoid propofol if hemodynamically unstable)
- Maintenance: IV agents only (narcotics, benzodiazepines, barbiturates) - NO inhalational agents
- Always use a sedative-hypnotic with the paralytic to prevent awareness 6