title: Noninvasive measurement of intracranial pressure via the pulsatility index on transcranial Doppler sonography: Is improvement possible?
abstract: OBJECTIVE
  We hypothesized that using hemodynamic variables could improve the prediction of intracranial pressure (ICP) from the middle cerebral artery pulsatility index (PI) measured with transcranial Doppler sonography.
  
  
  METHODS
  In this prospective study, 39 patients with traumatic brain injury were routinely examined with transcranial Doppler sonography, and the middle cerebral artery PI was calculated. A multivariate model including hematocrit, mean arterial blood pressure, heart rate, and arterial CO2 pressure (PaCO2 ) was evaluated.
  
  
  RESULTS
  Thirty-nine comatose patients (16 women and 23 men; age range 18-73 years; median 44 years) were included, and 234 data pairs (consisting of ICP and corresponding PI values) were analyzed. ICP ranged from -3 mmHg to +52 mmHg, and PI from 0.6 to 2.85. We found a significant but weak correlation between PI and the square root of ICP (R(2) between 0.29 and 0.34, p < 0.0001). A slightly stronger correlation was detected when hemodynamic variables were incorporated (R(2) between 0.37 and 0.43). Of these variables, mean arterial blood pressure had the most significant influence.
  
  
  CONCLUSIONS
  In this study, PI was not a sufficiently strong predictor of ICP to be used in clinical practice. Its reliability did not improve even when hemodynamic variables were considered. Therefore, we recommend abandoning the use of PI for the noninvasive measurement of ICP in clinical practice.
authors.affiliation: Clinic of Neurosurgery, University of Tuebingen, Hoppe-Seyler-Str. 3, D-72076, Tuebingen, Germany.
authors.forename: Matthias H
authors.initials: MH
authors.lastname: Morgalla
authors.affiliation: Clinic of Anaesthetics, University of Tuebingen, Hoppe-Seyler-Str. 3, D-72076, Tuebingen, Germany.
authors.forename: Harry
authors.initials: H
authors.lastname: Magunia
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003128:Coma; D005260:Female; D005544:Forecasting; D006801:Humans; D007427:Intracranial Pressure; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011673:Pulsatile Flow; D012044:Regression Analysis; D017585:Ultrasonography, Doppler, Transcranial / Q000191:economics / Q000592:standards* / Q000639:trends
keywords: cerebral blood flow; intracranial pressure; measurement accuracy; pulsatility index; transcranial Doppler sonography