Non-invasively estimated ICP pulse amplitude strongly correlates with outcome after TBI.
BACKGROUND
An existing monitoring database of brain signal recordings in patients with head injury has been re-evaluated with regard to the accuracy of estimation of non-invasive ICP (nICP) and its components, with a particular interest in the implications for outcome after head injury.


METHODS
Middle cerebral artery blood flow velocity (FV), ICP and arterial blood pressure (ABP) were recorded. Non-invasive ICP (nICP) was calculated using a mathematical model. Other signals analysed included components of ICP (n" indicates non-invasive): ICP pulse amplitude (Amp, nAmp), amplitude of the respiratory component (Resp, nResp), amplitude of slow vasogenic waves of ICP (Slow, nSlow) and index of compensatory reserve (RAP, nRAP). Mean values of analysed signals were compared against each other and between patients who died and survived.


RESULTS
The correlation between ICP and nICP was moderately strong, R = 0.51 (95% prediction interval [PI] 17 mm Hg). The components of nICP and ICP were also moderately correlated with each other: the strongest correlation was observed for Resp vs. nResp (r = 0.66), while weaker for Amp vs. nAmp (r = 0.41). Non-invasive pulse amplitude of ICP showed the strongest association with outcome, with the -difference between those who survived and those who died reaching a significance level of p < 0.000001.


CONCLUSIONS
When compared between patients who died and who survived mean nAmp showed the greatest difference, suggesting its potential to predict mortality after TBI.
Department of Clinical Neurosciences, Addenbrooke's Hospital, Cambridge, UK. kpb26@cam.ac.uk
Karol P
KP
Budohoski
Bernhard
B
Schmidt
Peter
P
Smielewski
Magdalena
M
Kasprowicz
Ronny
R
Plontke
John D
JD
Pickard
Jurgen
J
Klingelhöfer
Marek
M
Czosnyka
D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001930:Brain Injuries / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D023261:Glasgow Outcome Scale; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000503:physiopathology; D013223:Statistics as Topic; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult