Traumatic Brain Injury (TBI) Monitoring

OVERVIEW

  • The core physiological monitor used in TBI is ICP monitoring, in addition to standard monitoring used for any critically ill patient
  • Other TBI-specific physiological monitors are less widely used 
  • BTF guidelines consider ICP monitoring mandatory for severe TBI with an abnormal CT as intracranial hypertension develops in 60%
  • Nevertheless, there is currently no evidence of benefit from ICP monitoring in TBI in terms of clinical outcomes

INDICATIONS FOR ICP MONITORING

BTF Guidelines lists the following indications:

  • moderate -> severe head injury who can’t be serially neurologically assessed
  • severe head injury (GCS < 8) + abnormal CT scan
  • severe head injury (GCS < 8) + normal CT if 2 of the following are present:
    1. Age > 40 yrs
    2. BP < 90mmHg
    3. Abnormal motor posturing

BENEFITS OF ICP MONITORING

  • useful for CPP guided therapy
  • alerts clinicians to changes in the unconscious patient
  • easy to measure
  • staff familiarity
  • number and waveform to evaluate
  • continuous measure

RISKS AND LIMITATIONS OF ICP MONITORING

  • invasive procedure
  • intracranial bleeding < 3% (more with intraventricular catheters)
  • infections < 14%
  • malfunction/measurement error -> inappropriate or unnecessary investigations/interventions
  • might be misleading (not a global measurement)
  • no RCTs have demonstrated that ICP-guided therapy improves patient-centered outcomes (including BEST-TRIP)
  • some observational studies have noted an association between ICP guided management and prolonged length of stay and worse outcome (Cramer, 2005, Shafi, 2008)
  • individual ICP monitors have different limitations:
    -> intraparenchymal monitors/subdural bolts: can not be calibrated, subject to drift, does not allow CSF drainage
    -> EVD: require expertise and resource availability for placement, infection

EVIDENCE

  • There is no high level evidence supportive beneficial outcomes from ICP monitoring
  • BEST TRIP (NEJM, 2012)
    — MCRCT, 6 sites in Bolivia and Ecuador
    — n=324 patients >13y old with severe TBI, or GCS 8 or less within 48 hours
    — ICP monitoring (with protcol to keep ICP <20 mmHg) versus clinical exam + CT head only
    — outcome: found no difference in ICU LOS or 6 month mortality / neuropsychological and functional recovery
    — criticisms: performed in South America, limited generalisability, “it’s not the monitor, but what you do with it that matters”, in practice we use ICP + CTH + clinical exam not any subset thereof

TYPES OF ICP MONITORS

These include:

OTHER MONITORS

  • SjO2
  • tbO2 — awaiting the BOOST2 trial (ICP vs tbO2)
  • microdialysis
  • ocular ultrasound for optic nerve sheath diameter

LITFL

Journal articles


CCC 700 6

Critical Care

Compendium

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