Neurocritical Care

iv.

Cannot recalibrate the catheter, experience “zero drift” in ICP readings after prolonged use.

May not be entirely accurate for duration of use

Intraparenchymal catheter

ii.

Optimal location of placement is not well defined (injured vs. non-injured tissue).

iii.

Transduces partial pressure of brain tissue oxygen

iv.

Low values reflect increased ICP or reduced oxygen delivery.

Typically, will be used in combination with other monitoring modalities

Subarachnoid bolt

Single-lumen screw inserted through a burr hole into the subarachnoid space

ii.

Transduces ICP

iii.

Associated with increased CNS infection

Scalp electrodes are placed externally.

Standard of care for seizure monitoring or if initiating phenobarbital for ICP control to monitor for

attainment of burst suppression

Newer, less cumbersome devices are currently available that may improve accessibility.

Point-of-care EEG systems (e.g., Ceribell) may be useful for faster set up and triage of seizures

compared with traditional EEG set ups.

Ultrasound of intracranial vessels

Threshold values

125 cm/second may suggest vasospasm.

200 cm/second typically suggests severe vasospasm.

Lindegaard ratio: Ratio of target blood vessel (usually middle cerebral artery) to carotid (internal

carotid artery) blood velocity transcranial Doppler values – value of 3 or more suggests vasospasm

Scalp electrodes are placed externally.

BIS 0–100 (100 being completely wakeful)

Little correlation with BIS values and ICP control or extent of pharmacologic coma

A handheld device that uses high-speed camera and computing technology to provide quantitative,

reproductible, and precise measurements regarding the pupilary light reflex. This noninvasive technique

correlates to ICP and has acceptable accuracy to estimate intracranial hypertension (Robba 2020)

Values range from 0.0 to 4.9, and a value of less than 3.0 is considered an abnormal or sluggish response.