Noninvasive Intracranial Pressure Estimation With Transcranial Doppler: A Prospective Observational Study

Background: Transcranial Doppler (TCD) ultrasonography has been described for the noninvasive assessment of intracranial pressure (ICP). This study investigates the relationship between standard, invasive intracranial pressure monitoring (ICP i ) and noninvasive ICP assessment using a simple formula based on TCD-derived flow velocity (FV) and mean arterial blood pressure values (ICP TCD ). Material and Methods: We performed a prospective observational study on 100 consecutive traumatic brain injury patients requiring invasive ICP monitoring, admitted to the Neurosciences and Trauma Critical Care Unit of Addenbrooke’s Hospital, Cambridge, UK. ICP i was compared with ICP TCD using a method based on the “diastolic velocity-derived estimator” (FV d ), which was initially described for the noninvasive estimation of cerebral perfusion pressure but subsequently utilized for ICP assessment. Results: Median ICP i was 13 mm Hg (interquartile range: 10, 17.25 mm Hg). There was no correlation between ICP i and ICP TCD ( R =−0.17; 95% confidence interval [CI]: −0.35, 0.03; P =0.097). Bland-Altman analysis demonstrated wide 95% limits of agreement between ICP i and ICP TCD (−27.58, 30.10; SD, 14.42). ICP TCD was not able to detect intracranial hypertension (ICP i >20 mm Hg); the area under the receiver operating characteristic curve for prediction was 34.5% (95% CI, 23.1%-45.9%) with 0% sensitivity and 74.4% specificity for ICP TCD to detect ICP i >20 mm Hg. Conclusions: Using a formula based on diastolic FV, TCD is an insufficiently accurate method for the noninvasive assessment of ICP. Further studies are warranted to confirm these results in a broader patient cohort.