Utility of Transcranial Doppler in Estimating Cerebral Perfusion Pressure in Traumatic Brain Injury: A Prospective Observational Trial

Title Utility of transcranial Doppler (TCD) in estimating cerebral perfusion pressure (eCPP) in traumatic brain injury—a prospective observational trial. Aim To validate the utility of a noninvasive technique of eCPP estimation using transcranial Doppler (TCD). Materials and Methods Eighteen patients with severe traumatic brain injury (TBI) requiring intracranial pressure (ICP) monitoring as per the Brain Trauma Foundation guidelines were prospectively recruited for the study. ICP was measured in all patients using an intraventricular catheter. Mean arterial pressure (MAP) was recorded from an intra-arterial catheter. Cerebral perfusion pressure (CPP) was calculated as the difference between MAP and ICP. Middle cerebral blood flow velocities were recorded using TCD, and CPP was estimated from the middle cerebral artery (MCA) flow velocities (eCPP) using the formula eCPP = (MAP × end diastolic velocity [EDV]/mean velocity [MV]) + 14. Total 185 simultaneous readings of CPP and eCPP were available for analysis. Reliability statistics between CPP and eCPP were computed to calculate the intraclass correlation (ICC). Results The average CPP measured using intraventricular catheter was 73.2 (+/−12.4), and the mean estimated eCPP was 76.7 (+/−10.9). We found a very good Pearson's correlation between CPP and eCPP (r = 0.743) with a Cronbach's α of 0.843. In 86.2% of examinations, the estimation error of measuring CPP was within 10 mm Hg, and in 93.1% examinations, it was within 15 mm Hg. Conclusion eCPP estimated using TCD can serve as reliable noninvasive alternative in situations in which ICP monitoring is not available, even in moderate or mild head injury.