Intracranial Pressure (ICP) 

(Hamby, 2017; Pinto et al., 2021; Popovich, 2011)

What is ICP?

  • ICP is the pressure exerted on the brain by extra tissue (i.e., edema, tumor) or fluid (i.e., CSF or blood) inside the cranium. The increase in pressure (ICP) can cause brain herniation.

Purpose

  • The general purpose is to calculate and manage CPP as well as predict outcomes and worsening pathology. It is measured via an invasive probe inserted into the brain. Pay attention to the parameters ordered and readings throughout the session!

ICP Ranges

  • 5-15 mmHg: Normal ICP; Therapy can proceed as normal

  • 16-19 mmHg: Therapy can be performed, but limited to light activity. Be sure to discuss with the RN and/or medical team.

    • Pressures higher than 18 mmHg require medical intervention with either an external ventricular drain (EVD) or ventriculo-peritoneal (VP) shunt

  • >20 mmHg: Defer therapy

  • >30 mmHg:  Life-threatening, indicates poor prognosis 

Why Do We Care?

  • If ICP is too high (>25 for 5 minutes) it can result in brain herniation

    • Sustained ICP > 25 mmHg is a medical emergency; needs intervention

    • Spikes: ICP is mostly controlled with brief periods of > 25. This may or may not require intervention, but does not necessarily preclude mobility or therapy.

Symptoms of Increasing ICP

  • Symptoms can include: changes in consciousness, confusion, elevated BP and slowing HR, and cranial nerve III involvement 

    • Cushing’s Triad: a set of signs indicative of increased ICP. 1) bradycardia, 2) irregular respirations, and 3) widened pulse pressure.

Causes of Increased ICP

  • Causes of increased ICP can include: increased BP, agitation, nausea/vomiting, increased physical exertion, supine position with HOB flat, compression of the abdomen, or the Valsalva maneuver.

Management of Elevated ICPs

  1. External Ventricular Drain (EVD) (see lines/leads/drain section for more info on EVDs)

  2. Hyperosmolarity therapy: hypertonic saline (3%, 23%) and Mannitol injections (20%, 25%) (see medication section for more physiological info)

  3. Sedation

  4. Surgical intervention: hemicraniectomy

Implications for Therapy

Mobility does not necessarily increase ICP; theoretically sitting up should reduce ICP BUT:

  • If the patient is not tolerating weaning of sedation due to elevated ICP (either sustained or spikes), then they may not be able to wean sedation to perform mobility/participate in therapy

  • Stimulation in any manner can result in elevated hemodynamics, pain, and arousal, which could elevate ICPs

  • Excessive neck flexion in sitting could impede normal CSF drainage & increase ICP

  • Change in position will cause the ICP reading to be inaccurate if the drain is not re-leveled

  • Coughing with a change in position, especially if the patient has an ET tube, can briefly increase ICP (increased ICP with coughing is a normal physiologic response)

If the ICP is increasing, the RN can open the EVD with the patient in a sitting position

  • Be sure that the patient is relatively stationary and stable in sitting if EVD is open

Types of ICP Monitors

(Teach Me Surgery, 2021)

Schematic representing the anatomical insertion site for ICP monitoring 

© By TeachMeSurgery, 2020

ICP Data Only (‘bolts’)

  • Subarachnoid Bolt/Screw: A hole is drilled in the skull and a hollow screw is inserted abutting the dura. CSF is able to fill the hallow screw allowing the pressures to equalize.

    • Positives: infection and hemorrhage risks are low. 

    • Negatives: the possibility of errors from ICP underestimation, misplacement of the screw, and occlusion by debris. 

  • Subdural/Epidural Bolt: A hole is drilled in the skull and a sensor is inserted between the skull and dural tissue. Has decreased infection rate, but limitations include: lack of therapeutic uses, more pronounced signal attenuation often underestimating ICP. 

  • **Typically patients who have bolts in place are not stable enough to participate in therapy, but this needs to be evaluated on a case-by-case basis and could warrant further discussion with the medical team

ICP data plus CSF drainage

  • EVD: the gold standard for elevated ICP.

    • Benefits: used for therapeutic aspiration of CSF, rarely occludes, inexpensive.

    • Limitations: infection and potential for damage to underlying brain parenchyma.

References

Hamby, J. (2017). The Nervous System. In H. Smith-Gabai & S. E. Holm (Eds.), Occupational Therapy in Acute Care (2nd ed.). AOTA Press.

Pinto, V. L., Tadi, P., & Adeyinka, A. (2021). Increased Intracranial Pressure. In StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK482119/

Popovich, K. (2011). The Intensive Care Unit. In H. Smith-Gabai (Ed.), Occupational Therapy in Acute Care (1st ed., pp. 41–73). AOTA Press.

Teach Me Surgery. (2020, October 29). Intracranial pressure monitoring. TeachMeSurgery. https://teachmesurgery.com/neurosurgery/flow-and-pressure/icp-monitoring/