Codman ICP Monitor

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