Indications for intracranial pressure monitoring

By Alex Yartsev - 30/06/2015

Under which circumstances must one be so interested in intracranial pressure, so as to introduce things into the patient's skull? This question, in a variety of permutations, is a College favourite. For instance, it has recently appeared in Question 27 of the first paper of 2014, less recently in Question 16 of the first paper of 2009, and Question 27.2 from the first paper of 2008. The advantages and disadvantages of various ICP monitoring techniques are discussed elsewhere; this is the chapter which debates the very need for something like this.

In brief summary:

Indications for Invasive Intracranial Pressure Monitoring
Anyone with an abnormal CT and GCS 3-8 gets ICP monitoring.

(Recommendations of The Brain Trauma Foundation, 4th edition)

This probably did not merit a box. Anyway, the old third edition of the guidelines had some slightly more complex wording:

Anyone with an abnormal CT and GCS 3-8 gets ICP monitoring
Anyone with a normal CT, GCS 3-8, and any two of the following features:
- Age over 40
- Systolic BP <90
- Motor posturing

Advantages of Invasive Intracranial Pressure Monitoring
Prediction of outcome: average ICP in the first 48 hrs is a good independent predictor of both mortality and neuropsychological outcome There seems to be an improvement in mortality associated with the use of an ICP monitor in patients with severe traumatic brain injury, at least in some studies. Response to ICP-lowering therapies (or lack thereof) is a useful predictor of poor outcome. ICP monitoring did not appear to increase the length of stay or intensity of "brain-specific treatments" at least in one large 2012 study (Chestnut et al, NEJM) The BTF recommends ICP monitoring (i.e. the weight of international authority is behind this practice, whatever that means in court) An EVD is both a monitoring tool and a means of managing ICP. ICP monitoring is continuous, while clinical examination is intermittent; thus ICP monitoring can result in an earlier detection of new-onset intracranial hypertension from some new pathology, eg. a rebleed.

Disadvantages of Invasive Intracranial Pressure Monitoring
Routine ICP monitoring for all trauma patients may not influence mortality outcomes; or at least, there seems to be a lack of good evidence for a mortality-reducing role. Its role is therefore greatest in the management of severe TBI. Some studies suggest that it in fact does increase both length of stay and treatment intensity without any positive influence on outcome. The college, in their answer, quotes some sort of "BEST TRIPPS study". Presumably, that is the BEST:TRIP trial from 2012 ( Benchmark Evidence from South American Trials: Treatment of Intracranial Pressure). Indeed, it demonstrated an absence of mortality benefit. The exact conclusions were "for patients with severe traumatic brain injury, care focused on maintaining monitored intracranial pressure at 20 mm Hg or less was not shown to be superior to care based on imaging and clinical examination". ICP monitoring is associated with significant risk: Risks of anaesthesia Risks of craniotomy Risks of haemorrhage, especially in view of brain injury associated coagulopathy Risk of infection Malposition and poor monitoring quality Incorrect readings may stimulate incorrect management EVDs may clog with debris; parenchymal monitors may "drift" from their zero calibration value, leading to errors in decisinmaking.

In detail:

The Brain Trauma Foundation recommends (without any Level 1 evidence) that any severe brain injury patient (i.e. GCS 3-8) should have an ICP monitor of some sort. That's pretty obvious. ICP monitoring both guides treatment, reveals evolving pathology and predicts outcome.

The more salient question is, who requires ICP monitoring among those patients who have a normal CT, but still have a reduced level of consciousness?

Well.

The BTF gives us Level III guidelines for this. This is not a very strong set of recommendations. They are based on a retrospective observational study by Narayan et al. The overall risk of intracranial hypertension was only about 13% among patients with normal CT scans, but the authors found that the patients who met two of the abovementioned criteria (old age, posturing, hypotension) this risk increased to 60%.

I should think that any sort of abnormal posturing (or any focal neurological deficit) combined with a decreased level of consciousness following a traumatic brain injury should be a concern. The normal CT, in these circumstances, may reflect the deficts of CT in visualising posterior fosssa damage, like some sort of hideous brainsteam contusion, vertebral artery dissection, and what have you. Or perhaps the patient is not waking up because of a diffuse axonal injury. None of these pathologies benefit from ICP monitoring because raised ICP is not usually a feature.

Non-traumatic indications for intracranial pressure monitoring

Cochrane reviewers still have not found any studies of this topic worth combining into a meta-analysis.

However, a slightly dated opinion piece on this topic makes a broad suggestion:

"...we conclude that all patients with non-traumatic cerebral insult complicated by raised intracranial pressure or at risk of developing it, should be considered for measurement of intracranial pressure"

References

Our beloved Oh's Intensive Care manual has two excellent chapters to dedicate to this topic:

Chapter 43 (pp. 563) Cerebral protection by Victoria Heaviside and Michelle Hayes, and

Chapter 67 (pp. 765) Severe head injury by John A Myburgh.

However, the discerning reader will recognise this book as an antique, and look instead to the frequently updated Brain Trauma Organisation Guidelines for Management of Traumatic Brain Injury.

Narayan, Raj K., et al. "Intracranial pressure: to monitor or not to monitor? A review of our experience with severe head injury." Journal of neurosurgery 56.5 (1982): 650-659.

Forsyth, Rob J., Susanne Wolny, and Beryl Rodrigues. "Routine intracranial pressure monitoring in acute coma." Cochrane Database Syst Rev 2 (2010).

Badri, Shide, et al. "Mortality and long-term functional outcome associated with intracranial pressure after traumatic brain injury." Intensive care medicine 38.11 (2012): 1800-1809.

Farahvar, Arash, et al. "Increased mortality in patients with severe traumatic brain injury treated without intracranial pressure monitoring: Clinical article."Journal of neurosurgery 117.4 (2012): 729-734.

Chesnut, Randall M., et al. "A trial of intracranial-pressure monitoring in traumatic brain injury." New England Journal of Medicine 367.26 (2012): 2471-2481.

Farahvar, Arash, et al. "Response to intracranial hypertension treatment as a predictor of death in patients with severe traumatic brain injury: Clinical article."Journal of neurosurgery 114.5 (2011): 1471-1478.

Meythaler, Jay M., et al. "Current concepts: Diffuse axonal injury - associated traumatic brain injury." Archives of physical medicine and rehabilitation 82.10 (2001): 1461-1471.

Tasker, R. C., et al. "Monitoring in non-traumatic coma. Part I: Invasive intracranial measurements." Archives of disease in childhood 63.8 (1988): 888-894.

Cremer, Olaf L., et al. "Effect of intracranial pressure monitoring and targeted intensive care on functional outcome after severe head injury*." Critical care medicine 33.10 (2005): 2207-2213.

Shafi, Shahid, et al. "Intracranial pressure monitoring in brain-injured patients is associated with worsening of survival." Journal of Trauma and Acute Care Surgery 64.2 (2008): 335-340.

Lane, Peter L., et al. "Intracranial pressure monitoring and outcomes after traumatic brain injury." Canadian Journal of Surgery 43.6 (2000): 442.

Talving, Peep, et al. "Intracranial pressure monitoring in severe head injury: compliance with Brain Trauma Foundation guidelines and effect on outcomes: a prospective study: Clinical article." Journal of neurosurgery 119.5 (2013): 1248-1254.

Chesnut, Randall M., et al. "A trial of intracranial-pressure monitoring in traumatic brain injury." New England Journal of Medicine 367.26 (2012): 2471-2481.

Su, Shao-Hua, et al. "The Effects of Intracranial Pressure Monitoring in Patients with Traumatic Brain Injury." PloS one 9.2 (2014): e87432.

Dawes, Aaron J., et al. "Intracranial pressure monitoring and inpatient mortality in severe traumatic brain injury: A propensity score–matched analysis." Journal of Trauma and Acute Care Surgery 78.3 (2015): 492-502.

Muizelaar, J. Paul. "Multimodal Monitoring After Traumatic Brain Injury: Useless or Useful?*." Critical care medicine 43.2 (2015): 506-507.

Le Roux, Peter, et al. "The International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care: A List of Recommendations and Additional Conclusions." Neurocritical care (2014): 1-15.

Tisdall, M. M., and M. Smith. "Multimodal monitoring in traumatic brain injury: current status and future directions." British journal of anaesthesia 99.1 (2007): 61-67.

Yuan, Qiang, et al. "Effects and Clinical Characteristics of Intracranial Pressure Monitoring–Targeted Management for Subsets of Traumatic Brain Injury: An Observational Multicenter Study." Critical Care Medicine (2015).

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