OVERVIEW
- intracranial pressure monitor
- aka ‘bolt’
USES/INDICATIONS
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 - stroke
- cerebral edema
- hydrocephalus
- hepatic encephalopathy
DESCRIPTION
- 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
OTHER INFORMATION
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
ADVANTAGES
- easy to insert (can be done at bedside)
- less invasive than EVD
- more accurate ICP measurements than extradural bolt
- produces high fidelity wave forms
- small
DISADVANTAGES/ COMPLICATIONS
- infection
- 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
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. doi: 10.1056/NEJMoa1207363. Epub 2012 Dec 12. PubMed PMID: 23234472; PubMed Central PMCID: 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. doi: 10.1093/bja/aet418. Epub 2013 Nov 28. Review. PubMed PMID:Â 24293327.
Leave a Reply