GUIDE 2022/2023

22 mmHg

Describe the Cushing response:

The Cushing reflex (vasopressor response) is a physiological nervous system response to acute elevations of intracranial pressure (ICP) resulting in Cushing's triad of widened pulse pressure (increasingsystolic, decreasing diastolic), bradycardia, and irregular breathing.

Describe the Monro-Kellie Doctrine:

Explains intracranial pressure dynamics.

In a closed head injury, total volume of intracranial contents must remain constant.

ICP rises if intracranial contents (e.g. blood, fluid) increases.

Venous blood and CSF can be compressed out of the container, providing a degree of pressure buffering.

Very early after injury, a mass (e.g. hematoma) can displace enough venous blood and CSF to maintainadequate ICP.

Once the limit of displacement is reached, ICP increases exponentially and decompensation occurs.

Severe TBI can markedly reduce cerebral blood flow (CBF) during the first few hours after injury. How does CBF differ in those who remain comatose and those that recover?

In those that recover, CBF will increase in 2-3 days.