Prospective study on non-invasive assessment of ICP in head injured patients: comparison of four methods

• DOI: 10.17863/cam.10515
• Publication Date: 2016-04-15
• Authors: Marek Czosnyka; Marek Czosnyka; Brenno Caetano Tr...; Gustavo Frigieri; Manuel Cabeleira; Joseph Donnelly; Bernhard Schmidt; Danilo Cardim; Chiara Robba; Peter Smielewski; Xiuyun Liu; Georgios V. Varsos; Sérgio Mascarenhas; Maxwell Damian; Michal Bohdanowicz
• Keywords: Adult; Male; Traumatic Brain Injury; Intracranial Pressure; Ultrasonography, Doppler, Transcranial; traumatic brain injury; Transcranial Doppler; noninvasive ICP monitoring; Blood Pressure; Middle Aged; Models, Theoretical; transcranial Doppler; Non-invasive ICP monitoring; noninvasive ICP monitoring; transcranial Doppler; traumatic brain injury; Adult; Blood Flow Velocity; Blood Pressure; Brain Injuries, Traumatic; Cohort Studies; Female; Humans; Intracranial Pressure; Male; Middle Aged; Prospective Studies; Ultrasonography, Doppler, Transcranial; Young Adult; Models, Theoretical; Neurology (clinical); Cohort Studies; Young Adult; 03 medical and health sciences; 0302 clinical medicine; Brain Injuries, Traumatic; Humans; Female; Prospective Studies; Blood Flow Velocity

Elevation of intracranial pressure (ICP) may occur in many diseases, and therefore the ability to measure it noninvasively would be useful. Flow velocity signals from transcranial Doppler (TCD) have been used to estimate ICP; however, the relative accuracy of these methods is unclear. This study aimed to compare four previously described TCD-based methods with directly measured ICP in a prospective cohort of traumatic brain-injured patients. Noninvasive ICP (nICP) was obtained using the following methods: 1) a mathematical "black-box" model based on interaction between TCD and arterial blood pressure (nICP_BB); 2) based on diastolic flow velocity (nICP_FVd); 3) based on critical closing pressure (nICP_CrCP); and 4) based on TCD-derived pulsatility index (nICP_PI). In time domain, for recordings including spontaneous changes in ICP greater than 7 mm Hg, nICP_PI showed the best correlation with measured ICP (R = 0.61). Considering every TCD recording as an independent event, nICP_BB generally showed to be the best estimator of measured ICP (R = 0.39; p < 0.05; 95% confidence interval [CI] = 9.94 mm Hg; area under the curve [AUC] = 0.66; p < 0.05). For nICP_FVd, although it presented similar correlation coefficient to nICP_BB and marginally better AUC (0.70; p < 0.05), it demonstrated a greater 95% CI for prediction of ICP (14.62 mm Hg). nICP_CrCP presented a moderate correlation coefficient (R = 0.35; p < 0.05) and similar 95% CI to nICP_BB (9.19 mm Hg), but failed to distinguish between normal and raised ICP (AUC = 0.64; p > 0.05). nICP_PI was not related to measured ICP using any of the above statistical indicators. We also introduced a new estimator (nICP_Av) based on the average of three methods (nICP_BB, nICP_FVd, and nICP_CrCP), which overall presented improved statistical indicators (R = 0.47; p < 0.05; 95% CI = 9.17 mm Hg; AUC = 0.73; p < 0.05). nICP_PI appeared to reflect changes in ICP in time most accurately. nICP_BB was the best estimator for ICP "as a number." nICP_Av demonstrated to improve the accuracy of measured ICP estimation.