Monitoring of Intracranial, Cerebral, and Spinal Perfusion Pressures

Intracranial Pressure (ICP) and Cerebral Perfusion Pressure (CPP)

The American College of Surgeons recommends measuring intracranial pressure using invasive monitoring with intraparenchymal probes or intraventricular catheters, with intraparenchymal probes generally preferred due to their better risk-benefit profile, and cerebral perfusion pressure is calculated as CPP = MAP - ICP, with mean arterial pressure measured at the level of the external ear canal (level of the foramen of Monro) 1, 2, 3
The Brain Trauma Foundation suggests that intraparenchymal probes have an infection rate of 2.5% and intracerebral hemorrhage rate of 0-1%, making them a preferred method for ICP monitoring 1, 2
The Neurocritical Care Society recommends that intraventricular catheters have a higher complication rate, with infection rates of 10% and hemorrhage rates of 2-4%, but allow for therapeutic drainage of cerebrospinal fluid 1, 2
The American Heart Association recommends measuring mean arterial pressure at the level of the external ear canal to avoid overestimation of CPP 3
The formula for calculating CPP is CPP = MAP - ICP, as recommended by the Brain Trauma Foundation 3
The therapeutic goal is to maintain CPP between 60-70 mmHg in patients with traumatic brain injury, as recommended by the World Journal of Emergency Surgery 4, 1, 2
CPP thresholds are critical, with CPP <60 mmHg associated with poor neurological outcomes and CPP >90 mmHg potentially worsening vasogenic cerebral edema, as reported by the Brain Trauma Foundation 1, 2, 3

The American College of Surgeons recommends ICP monitoring in patients with severe traumatic brain injury (Glasgow Coma Scale ≤8) with abnormal computed tomography scans 4, 1, 2
The Neurocritical Care Society suggests that ICP monitoring is also indicated in patients with normal computed tomography scans but inability to perform adequate neurological evaluation or hemodynamic instability 1, 2
The Brain Trauma Foundation recommends ICP monitoring after evacuation of intracranial hematoma with at least one of the following: Glasgow motor response ≤5, anisocoria or bilateral midriasis preoperatively, hemodynamic instability, signs of severity on neuroimaging, intraoperative cerebral edema, or new postoperative lesions 2

The American Academy of Neurology states that there is no reliable estimation of ICP using blood pressure or physical examination alone 3
The Brain Trauma Foundation reports that clinical signs such as Cushing's triad (hypertension, bradycardia, irregular respirations) appear only when ICP is critically elevated and herniation is imminent 3
The Neurocritical Care Society notes that pupillary changes such as anisocoria or bilateral midriasis indicate advanced intracranial hypertension, not early elevation 3