Intracranial Hypertension & Herniation
The relationship between the cranial vault and its contents (brain, blood & csf) is a delicate balance that requires intact cerebral autoregulation and a conceptual understanding of the Monroe-Doctrine is a must for any member within the Neuro ICU. This page will introduce you to the foundational concepts of intracranial pressure as well as approaches to management.
Pathophysiology
The understanding of intracranial pressures (ICP), requires a foundational knowledge of the Monro-Kellie Doctrine / Hypothesis, which describes the relationship between the volume of the cranial vault and ICP as the following:
The sum of the volume of brain, csf and blood is constant
The increase in one component must be compensated for by a proportional decrease in the others
When compensatory mechanisms are exhausted, and elevated ICP results.
Components of the Cranial Vault:
Brain (approx 80%)
Venous and arterial blood (each 5%)
CSF (10%)
In general, the volume of intracranial contents can increase up to 10%, but this percentage depends on the volume of the brain parenchyma and its ability or inability to accept changes in volume—a higher percentage may be tolerated in an older brain with atrophy than in a younger brain.
Clinical Presentation
Once compensatory mechanisms fail...
Concepts in ICP Monitoring
One Pagers
OnePager_CerebralMonitoring.pdfCerebral Monitoring I
OnePager_AdvancedMonitoringII.pdfCerebral Monitoring II
ICP1_OnePager.pdfICP Concepts I
ICP2_OnePager.pdfICP Concepts II
Articles for Further Reading
ENLS_Intracranial Hypertension & Herniation.pdfManagement_of_Intracranial_Pressure.8.pdf