Reference

Anatomy & Physiology

The mechanisms underneath the monitoring. Each section explains what is physically happening, then what it means for a decision at the bedside.

1. The Monro–Kellie doctrine

   The adult skull is a closed box of fixed volume.

2. Intracranial compliance

   Compliance is the change in volume tolerated per unit change in pressure.

3. Cerebral perfusion pressure

   Perfusion of the brain depends on the pressure gradient across it, not on systemic blood pressure alone:

4. Cerebral autoregulation

   A healthy brain holds cerebral blood flow roughly constant across a wide range of perfusion pressures — conventionally quoted as about 50 to 150 mmHg — by constricting…

5. Determinants of cerebral blood flow

   Four factors dominate, and three are directly manipulable:

6. Venous drainage

   Outflow obstruction is the most easily missed cause of a rising ICP, and the cheapest to fix.

7. Herniation syndromes

   When pressure gradients develop between compartments, brain tissue is displaced across the fixed dural and bony boundaries.