Why Hyperventilation Is Harmful in Head Injury

Hyperventilation (rapid, deep breathing) lowers arterial PaCO₂, causing cerebral vasoconstriction. This reduces cerebral blood flow (CBF) and oxygen delivery to already injured brain tissue, potentially worsening ischemia and secondary injury.

Evidence-Based Guidance

• Avoid prophylactic hyperventilation in acute traumatic brain injury (TBI).
• Brief, mild hyperventilation (PaCO₂ 30–35 mmHg) may be used temporarily for impending herniation as a bridge to definitive therapy (surgery, osmotherapy).
• Continuous end-tidal CO₂ (EtCO₂) or arterial blood gas monitoring is mandatory.

Current guidelines (Brain Trauma Foundation) recommend maintaining normocapnia (PaCO₂ 35–40 mmHg) in most TBI patients.