Name two principal mechanisms of secondary brain injury after TBI.

• A. Hypoxia and hypotension
• B. Hyperglycemia and fever
• C. Hypertension and hyperoxia
• D. Seizures and infection

Answer: (A)

When brain injury progresses, the most important drivers of additional damage are problems with oxygen delivery and blood flow to the brain. If the brain tissue becomes hypoxic, neurons can’t generate enough ATP, ion pumps fail, cells swell, and a cascade of excitotoxic and inflammatory processes accelerates injury. If systemic blood pressure falls (hypotension), cerebral perfusion pressure drops, so blood flow to the injured brain decreases, compounding oxygen and glucose shortfalls. In the acute phase, the brain’s ability to regulate blood flow is often impaired, so drops in pressure hit the injured tissue particularly hard. Together, hypoxia and hypotension create a dangerous energy crisis in brain tissue that amplifies injury beyond the initial trauma.

Other factors like high blood sugar, fever, seizures, infections, or excessive oxygen can worsen outcomes, but they are not the primary combination that drives secondary injury. They contribute to metabolic stress or additional injury, whereas maintaining adequate oxygen delivery and perfusion targets the main mechanisms at play.