Significance and treatment of hypotension

1. Big picture

In neurology, hypotension is dangerous because the brain depends on continuous blood flow. If systemic blood pressure falls, cerebral perfusion may fall below the level needed for normal neuronal function. This can cause presyncope, syncope, watershed infarction, global cerebral ischemia, hypoxic-ischemic encephalopathy, worsening of acute ischemic stroke, or secondary brain injury after trauma or hemorrhage.

The key exam sentence:

Hypotension is especially dangerous in patients with impaired cerebral perfusion reserve, such as carotid stenosis, acute ischemic stroke, raised intracranial pressure, shock, cardiac arrest, or autonomic failure.

A very important neurological formula is:

Cerebral perfusion pressure = mean arterial pressure − intracranial pressure.

So hypotension reduces perfusion directly, and raised intracranial pressure reduces it indirectly.

---