Bedside study of cerebral critical closing pressure in patients with severe traumatic brain injury: a transcranial Doppler study.
OBJECTIVE
Cerebral critical closing pressure (CrCP) is the arterial pressure (AP) below which small arterial cerebral vessels collapse. Our objective was to estimate cerebral CrCP in 12 severe TBI patients, relating transcranial Doppler flow velocity (FV) and AP data.


METHODS
FV, intracranial pressure (ICP) and invasive AP were prospectively acquired at 50 Hz. CrCP was estimated using three methods (M): M(1): amplitude ratio of FV/AP first harmonics; M(2): AP axis intersection of the regression line between systolic and diastolic values of FV and AP; M(3): AP axis intersection of the regression line between decreasing AP and FV simultaneous values.


RESULTS
There were 12 patients. Frequent negative CrCP values were found. Average M(1):-12 mmHg; M(2):-33 mmHg; M(3):-43 mmHg. Correlation between the three methods was significant (P < 0.01). M(1) showed the lowest range and more positive values. The better limits of agreement (Bland and Altman test) were between M(2) and M(3).


CONCLUSIONS
The frequently found negative values do not allow us for the moment, to use any of these three methods for clinical guidance.
Universidad de la República School of Medicine, Montevideo, Uruguay. coripuppo@gmail.com
Corina
C
Puppo
J
J
Camacho
B
B
Yelicich
L
L
Moraes
A
A
Biestro
H
H
Gomez
D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology*; D001930:Brain Injuries / Q000000981:diagnostic imaging* / Q000503:physiopathology* / Q000601:surgery; D056424:Decompressive Craniectomy / Q000379:methods; D015150:Echocardiography, Doppler; D005260:Female; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D013223:Statistics as Topic; D055815:Young Adult