- intracranial pressure monitor
- aka ‘bolt’
Suspected raised intracranial pressure
- severe head injury
— unable to monitor neurologically
— GCS < 8 and abnormal CT
— GCS <8 and normal CT with 2/3 of: age >40y, motor posturing and SBP <90 mmHg
- cerebral edema
- hepatic encephalopathy
- strain gauge tipped catheter or fiberoptic device
METHOD OF INSERTION AND/OR USE
- sterile technique
- bolt through fronto-parietal suture-line, in line with pupil
- zero at external auditory meatus
- penetrates through dura into CSF or intraparencymally
- held in place by bolt
Interpretation of Waveforms
- High amplitude of 50-100mmHg sustained for 15 min (‘A waves’) – raised ICP
- Saw tooth with small changes in pressure every 0.5-2 minutes (‘B waves’) – poor intracranial compliance
- Low amplitude oscillations up to 20mmHg for 1 min (‘C waves’) – normal
- Flat ICP trace – compression or kinking of transducer
- Rounded appearance of the waveform – raised ICP
- easy to insert (can be done at bedside)
- less invasive than EVD
- more accurate ICP measurements than extradural bolt
- produces high fidelity wave forms
- transducer tip may rest on brain and obstruct
- aspiration of CSF not possible
- tends to under-read pressures > 20mmHg
- intracranial transducer cannot be calibrated once in situ
- baseline drift (especially after 5 days)
- remember they don’t give an indication of infratentorial pressure
- no RCT evidence of benefit
References and Links
- 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. PMC3565432.
- 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. PMID: 24293327.
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health, a Clinical Adjunct Associate Professor at Monash University, and the Chair of the Australian and New Zealand Intensive Care Society (ANZICS) Education Committee. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of LITFL.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of two amazing children.
On Twitter, he is @precordialthump.