Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage: Preliminary Results

Aim: Increased intracranial pressure (ICP) is considered to be the most important mechanism of secondary brain injury in patients with acute traumatic brain injury (TBI), and intracranial hemorrhage (ICH) including subarachnoid hemorrhage (SAH). Currently, ICP can be measured and registered only using invasive techniques in routine clinical practice. Routine ICP monitoring in terms of intraventricular and intraparenchymal measurements are invasive, require a surgical procedure, and are associated with complications such as infection and intracranial bleedings. The aim of this ongoing study is the validation of noninvasive absolute ICP measurements with standard methods of invasive measurements obtained with intraventricular or intraparenchymal probes. Additionally, the accuracy and precision of noninvasive absolute ICP will be evaluated. Preliminary results are presented. Methods: The noninvasive ICP measurement device used in this study has been developed in the Telematic Science Laboratory at the Kaunas University of Technology, Lithuania. Noninvasive technique for measurement of ICP is based on simultaneously measuring of an ophthalmic artery (OA) blood flow parameters in the intracranial (IOA) and extracranial (EOA) segments of the OA with two-depth transcranial Doppler (TCD) measurements including mechanical head frame for fixation of ultrasonic transducer on the closed eye lid. No individual patient-specific calibration is required. Approval of Swissmedic and our EC was obtained in December 2013. Results: A total of 43 repeatable simultaneous paired noninvasive and invasive ICP measurements in 10 patients admitted with TBI, SAH, or ICH in our ICU. Preliminary results showed an accuracy (systematic error) of noninvasive absolute ICP measurement of 0.64 mm Hg, and a precision (standard deviation of the random error) SD = 1.76 mm Hg. The mean systematic error (0.64 mm Hg) from 43 data points showed a statistically significant evidence. To reach significant evidence > 95%, more paired data points are needed. During our 15 months study period no adverse event was observed. Conclusion: Preliminary results of this study showed that noninvasive transcranial Doppler absolute ICP measurement correlates with standard invasive ICP measurement. This method seems to be safe and reliable. The introduction of this technique is might be promising for the preoperative evaluation of patients presenting with severe stroke and brain tumors.