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:

• CCC — Codman ICP Monitor
• CCC — Extradural ICP Monitors
• CCC — External Ventricular Drain

OTHER MONITORS

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

References and Links

LITFL

• CCC – Traumatic Brain Injury: Assessment
• CCC – Traumatic Brain Injury: Management
• CCC – Traumatic Brain Injury: Monitoring
• CCC – Traumatic Brain Injury: Prognosis
• CCC – Traumatic brain injury: Overview
• CCC – Increased ICP in TBI
• CCC – Limitations of CT in Traumatic Brain Injury
• CCC – Cerebral Perfusion Pressure (CPP) in TBI

Journal articles

• Chesnut RM, Temkin N, Carney N, Dikmen S, Rondina C, Videtta W, Petroni G, Lujan S, Pridgeon J, Barber J, Machamer J, Chaddock K, Celix JM, Cherner M, Hendrix T. A trial of intracranial-pressure monitoring in traumatic brain injury. N Engl J Med. 2012 Dec 27;367(26):2471-81
• Kirkman MA, Smith M. Intracranial pressure monitoring, cerebral perfusion pressure estimation, and ICP/CPP-guided therapy: a standard of care or optional extra after brain injury? Br J Anaesth. 2014 Jan;112(1):35-46
• Raboel PH, Bartek J Jr, Andresen M, Bellander BM, Romner B. Intracranial Pressure Monitoring: Invasive versus Non-Invasive Methods-A Review. Crit Care Res Pract. 2012;2012:950393
• Smith M. Monitoring intracranial pressure in traumatic brain injury. Anesth Analg. 2008 Jan;106(1):240-8