Feeling the pressure in the TBI?

Chesnut RM, Temkin N, Carney N et al. A trial of intracranial-pressure monitoring in traumatic brain injury. New England Journal of Medicine 2012; 367: 2471-2481

RHH Journal Club. May 2nd, 2013. Dr Phillipa Horsfield

No full-text available

Does the information derived from the monitoring of intracranial pressure in patients with severe traumatic brain injury improve medical practice and patient outcomes?

Study design:

  • Multicentre randomised controlled trial
  • Latin America (Bolivia and Equador) Sept 2008 – Oct 2011

Methodology:

  • Population:
    • All patients > 12 yrs old with traumatic brain injury admitted within 24 hrs of injury
    • GCS 3-8 on admission or within 48hrs (GCS motor component 1-5 if intubated)
    • Intervention/Comparison
      • Randomisation to pressure monitoring or imaging-clinical examination groups
      • General measures eg. sedation, ventilation etc followed for both groups
      • Pressure monitoring group
        •  Intraparenchymal monitor placed as soon as possible following randomisation, treated to maintain ICP < 20mmHg
  • Imaging andclinical examination group
    • Protocol followed – treatment based on clinical and imaging signs of intracranial hypertension  in accordance with pre-trial standard of care at participating hospitals
    • Outcomes
      • Primary
        • Composite of 21 components (measures of survival – mortality at 14 days and 6 months, duration and level of impaired consciousness, functional and neuropsychological status 3 and 6 months after injury)
  • Secondary
    • Length of stay in ICU, systemic complications

Validity

  • 324 patients, predominantly young men
  • Block randomisation,  stratified to site, severity of injury, age
  •  Intervention not blinded but assessors of outcome measures were unaware of the group assignment
  • Patients analysed in the groups to which they were randomised
    • Small number of patients in each group received treatment for other group
    • Groups similar at baseline
    • 92 % followed up for 6 months or until death
    • External validity affected by study population and location of study

Results

  • Primary outcome: No significant difference in 14 day or 6 month mortality
    • Proportional odds ratio greater than 1 in many variables indicating improved outcomes in pressure monitoring group, however study designed to detect a difference corresponding to odds ratio of 1.5
    • Secondary outcomes: No significant difference

Application

  • Study data appears not to support the superiority of management of traumatic brain injury guided by intracranial pressure monitoring, however, caution required in extrapolating results to a UK population
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3 thoughts on “Feeling the pressure in the TBI?

  1. Many thanks to Phillipa for her excellent summary.

    I have significant concerns about the usefulness of this study in the context of TBI management.

    My first concern is an ethical one. If the authors truly felt there was equipoise regarding the use of ICP monitors in TBI, then why was the study not undertaken in the US? Taking a new technology to the developing world, where clinicians are unfamiliar with it, was never going to be a successful intervention. Neurointensivists will agree that the absolute value of the ICP is not important; it only forms a small part of the overall picture of the patient and how they should be managed. In addition why are there no clinicians from the Latin America hospitals amongst the authors?

    The next concern is the applicability of the study to first world centres. Less than 25% of patients made it to hospital in less than 60 min and only 45% came to hospital by ambulance. in the context of this very underdeveloped prehospital care system, it is unsurprising that subsequent ITU management was able to show a difference; in most cases the secondary brain injury would have already occurred. ICP bolts were sited on the basis of GCS alone: this does not reflect UK practice, where other factors such as CT appearance, age etc are taken into account. GCS is a very crude tool for outcome prediction (and was never designed for this) – see the Virginia Prediction Tree for a better risk stratification.

    The intervention ICP target was similar to DECRA (> 20mmHg for > 15 mins). This is not the standard triggered in UK management, as it is felt to be too aggressive.

    Over 55% of the outcome measures were neuropsychological tests; neuropsychological performance is highly influential in the composite endpoint. If eGOS is used there is a slight outcome benefit in favour of ICP monitoring (although at a high risk of a type error, as this endpoint is only powered to 40%).

    Overall I think this study shows that ICP monitoring in isolation will not alter outcome in TBI; however, ICP monitoring as part of a package of interventions is still of great value.

    Reply
  2. Quite agree, thanks for an excellent summary and comment. I might add that targeting just ICP only represents a part of accepted 1st world protocols, where CPP maintainance during periods of high ICP is also important. Where autoregulation is predominately intact raising CPP is a treatment for high ICP in itself.

    Similar concerns over ethics and applicability have been raised over the FEAST trial, but at least in that example treatment interventional was relatively simple and numbers large. This study has neither such advantages.

    Reply
  3. Hi @criticalinsight. Glad we concur on this one. I wonder if the NEJM would have been so keen to publish it had Randall Chesnut not been first author. I never considered the ethics of FEAST but it’s an interesting parallel. Both studies demonstrate the key aspect of study population being the main determinant of applicability; this is becoming an increasing issue with the large volume of studies coming out of China.

    Reply

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