title: Regional pressure and temperature variations across the injured human brain: comparisons between paired intraparenchymal and ventricular measurements.
abstract: BACKGROUND
  Intraparenchymal, multimodality sensors are commonly used in the management of patients with severe traumatic brain injury (TBI). The 'gold standard', based on accuracy, reliability and cost for intracranial pressure (ICP) monitoring is within the cerebral ventricle (external strain gauge). There are no standards yet for intracerebral temperature monitoring and little is known of temperature differences between brain tissue and ventricle. The aim of the study therefore was to determine pressure and temperature differences at intraparenchymal and ventricular sites during five days of continuous neuromonitoring.
  
  
  METHODS
  Patients with severe TBI requiring emergency surgery.
  
  
  METHODS
  patients who required ICP monitoring were eligible for recruitment. Two intracerebral probe types were used: a) intraventricular, dual parameter sensor (measuring pressure, temperature) with inbuilt catheter for CSF drainage: b) multiparameter intraparenchymal sensor measuring pressure, temperature and oxygen partial pressure. All sensors were inserted during surgery and under aseptic conditions.
  
  
  RESULTS
  Seventeen patients, 12 undergoing neurosurgery (decompressive craniectomy n = 8, craniotomy n = 4) aged 21-78 years were studied. Agreement of measures for 9540 brain tissue-ventricular temperature 'pairs' and 10,291 brain tissue-ventricular pressure 'pairs' were determined using mixed model to compare mean temperature and pressure for longitudinal data. There was no significant overall difference for mean temperature (p = 0.92) or mean pressure readings (p = 0.379) between tissue and ventricular sites. With 95.8 % of paired temperature readings within 2SD (-0.4 to 0.4 °C) differences in temperature between brain tissue and ventricle were clinically insignificant. For pressure, 93.5 % of readings pairs fell within the 2SD range (-9.4756 to 7.8112 mmHg). However, for individual patients, agreement for mean tissue-ventricular pressure differences was poor on occasions.
  
  
  CONCLUSIONS
  There is good overall agreement between paired temperature measurements obtained from deep white matter and brain ventricle in patients with and without early neurosurgery. For paired ICP measurements, 93.5 % of readings were within 2SD of mean difference. Whilst the majority of paired readings were comparable (within 10 mmHg) clinically relevant tissue-ventricular dissociations were noted. Further work is required to unravel the events responsible for short intervals of pressure dissociation before tissue pressure readings can be definitively accepted as a reliable surrogate for ventricular pressure.
authors.affiliation: Centre for Health and Social Care Research, Sheffield Hallam University, Montgomery House, 32 Collegiate Crescent, Sheffield, S102BP, UK. c.childs@shu.ac.uk.
authors.forename: Charmaine
authors.initials: C
authors.lastname: Childs
authors.affiliation: Department of Biostatistics, Deans Office, National University of Singapore, Level 6, Kent Ridge Wing, National University Hospital, Singapore, 119074, Singapore. liang_shen@nuhs.edu.sg.
authors.forename: Liang
authors.initials: L
authors.lastname: Shen
mesh_terms: D015998:Abbreviated Injury Scale; D000328:Adult; D000368:Aged; D001831:Body Temperature / Q000502:physiology*; D001921:Brain / Q000503:physiopathology*; D001930:Brain Injuries / Q000503:physiopathology*; D003399:Craniotomy; D056424:Decompressive Craniectomy; D005260:Female; D023261:Glasgow Outcome Scale; D006801:Humans; D015601:Injury Severity Score; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D011446:Prospective Studies; D055815:Young Adult