title: Doppler flow velocity and intra-cranial pressure: responses to short-term mild hypocapnia help to assess the pressure-volume relationship after head injury.
abstract: To anticipate an increase in intra-cranial pressure (ICP), information about pressure-volume (p/v) compliance is required. ICP monitoring often fails at this task after head injury. Could a test that transiently shifts intra-cranial blood volume produce consistent information about the p/v relationship? Doppler flow velocities in the middle cerebral arteries (left: 80.8 ± 34.7 cm/s; right: 65.9 ± 28.0 cm/s) and ICP (16.4 ± 6.7 mm Hg) were measured in 29 patients with head injury, before and during moderate hypocapnia (4.4 ± 3.0 kPa). The ratio of vasomotor response to change in ICP differed between those with high (left: 14.8 ± 6.9, right: 14.4 ± 6.6 cm/s/kPa/mm Hg) and low (left: 1.8 ± 0.6, right: 2.2 ± 0.9 cm/s/kPa/mm g) intra-cranial compliance. Additionally, the ratio identified 12 patients deviating from the classic non-linear p/v curve (left: 5.7 ± 1.3, right: 5.8 ± 1.0 cm/s/kPa/mm Hg). They exhibited an almost proportional relationship between vasomotor and ICP responses (R = 0.69, p < 0.01). Results suggest that a test that combines the responses of two intra-cranial compartments may provide consistent information about intra-cranial p/v compliance, even if the parameters derived from ICP monitoring are inconclusive.
authors.affiliation: Department of Academic Neurosurgery, Addenbrooke's Hospital, Cambridge, UK. chaubrich@ukaachen.de
authors.forename: Christina
authors.initials: C
authors.lastname: Haubrich
authors.forename: Luzius A
authors.initials: LA
authors.lastname: Steiner
authors.forename: Rolf R
authors.initials: RR
authors.lastname: Diehl
authors.forename: Magdalena
authors.initials: M
authors.lastname: Kasprowicz
authors.forename: Piotr
authors.initials: P
authors.lastname: Smielewski
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
mesh_terms: D000328:Adult; D001783:Blood Flow Velocity; D001810:Blood Volume; D001811:Blood Volume Determination / Q000379:methods*; D002245:Carbon Dioxide; D006259:Craniocerebral Trauma / Q000150:complications / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D019586:Intracranial Hypertension / Q000000981:diagnostic imaging* / Q000209:etiology / Q000503:physiopathology*; D007427:Intracranial Pressure; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D017585:Ultrasonography, Doppler, Transcranial
chemical_list: D002245:Carbon Dioxide
keywords: Cerebral blood flow; Hypocapnia; Intra-cranial compliance; Intra-cranial pressure; Pressure-volume compliance; Transcranial Doppler; Vasomotor response