What are the units that intracranial pressure (ICP) is measured in?

Units of Intracranial Pressure Measurement

Intracranial pressure (ICP) is measured in millimeters of mercury (mmHg).

Standard Unit of Measurement

• ICP is universally measured and reported in mmHg across all clinical guidelines and research literature 1, 2, 3.

• Normal ICP values are below 10 mmHg, with pathological elevation defined as sustained pressures exceeding 20 mmHg 4, 5.

Clinical Thresholds in mmHg

The use of mmHg as the standard unit allows for consistent clinical decision-making across different monitoring systems:

• Treatment threshold: ICP values of 20-25 mmHg typically trigger aggressive intervention 4, 5, 6.

• Moderate elevation: ICP of 20-40 mmHg is associated with a 3.95 times higher risk of mortality and poor neurological outcomes 2, 3.

• Severe elevation: When ICP exceeds 40 mmHg, mortality risk increases 6.9 times 2, 3.

Cerebral Perfusion Pressure Calculation

• The formula CPP = MAP - ICP uses mmHg for all pressure measurements, with the target CPP maintained between 60-70 mmHg 1, 2.

• Mean arterial pressure (MAP) should be measured at the level of the external ear canal (foramen of Monro) to ensure accurate CPP calculation 1.

Monitoring Methods

Both primary ICP monitoring techniques report values in mmHg:

• Intraparenchymal probes: Preferred method with lower complication rates (2.5% infection, 0-1% hemorrhage) 1, 3.

• Intraventricular catheters: Higher complication rates (10% infection, 2-4% hemorrhage) but allow therapeutic CSF drainage 1, 3.