title: Complex analysis of intracranial hypertension using approximate entropy.
abstract: OBJECTIVE
  To determine whether decomplexification of intracranial pressure dynamics occurs during periods of severe intracranial hypertension (intracranial pressure >25 mm Hg for >5 mins in the absence of external noxious stimuli) in pediatric patients with intracranial hypertension.
  
  
  METHODS
  Retrospective analysis of clinical case series over a 30-month period from April 2000 through January 2003.
  
  
  METHODS
  Multidisciplinary 16-bed pediatric intensive care unit.
  
  
  METHODS
  Eleven episodes of intracranial hypertension from seven patients requiring ventriculostomy catheter for intracranial pressure monitoring and/or cerebral spinal fluid drainage.
  
  
  METHODS
  None.
  
  
  RESULTS
  We measured changes in the intracranial pressure complexity, estimated by the approximate entropy (ApEn), as patients progressed from a state of normal intracranial pressure (<25 mm Hg) to intracranial hypertension. We found the ApEn mean to be lower during the intracranial hypertension period than during the stable and recovering periods in all the 11 episodes (0.5158 +/- 0.0089, 0.3887 +/- 0.077, and 0.5096 +/- 0.0158, respectively, p < .01). Both the mean reduction in ApEn from the state of normal intracranial pressure (stable region) to intracranial hypertension (-0.1271) and the increase in ApEn from the ICH region to the recovering region (0.1209) were determined to be statistically significant (p < .01).
  
  
  CONCLUSIONS
  Our results indicate that decreased complexity of intracranial pressure coincides with periods of intracranial hypertension in brain injury. This suggests that the complex regulatory mechanisms that govern intracranial pressure may be disrupted during acute periods of intracranial hypertension. This phenomenon of decomplexification of physiologic dynamics may have important clinical implications for intracranial pressure management.
authors.affiliation: ETSI-Telecomunicación de Valladolid, University of Valladolid, Spain.
authors.forename: Roberto
authors.initials: R
authors.lastname: Hornero
authors.forename: Mateo
authors.initials: M
authors.lastname: Aboy
authors.forename: Daniel
authors.initials: D
authors.lastname: Abasolo
authors.forename: James
authors.initials: J
authors.lastname: McNames
authors.forename: Wayne
authors.initials: W
authors.lastname: Wakeland
authors.forename: Brahm
authors.initials: B
authors.lastname: Goldstein
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D001930:Brain Injuries / Q000150:complications* / Q000175:diagnosis; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D019277:Entropy; D005260:Female; D005500:Follow-Up Studies; D015600:Glasgow Coma Scale; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D015278:Intensive Care Units, Pediatric; D019586:Intracranial Hypertension / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery*; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods; D011336:Probability; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014696:Ventriculostomy / Q000379:methods*