Evaluation of a New Brain Tissue Probe for Intracranial Pressure, Temperature and Cerebral Blood Flow Monitoring in Patients with aneurysmal subarachnoid hemorrhage

Objective: To evaluate a brain tissue probe for intracranial pressure (ICP) and temperature (TEMP) monitoring as well as determination of cerebral hemodynamics using a near infrared spectroscopy (NIRS) and indocyanine green (ICG) dye dilution method (NIRS-ICP probe). Methods: The NIRS-ICP probe was applied after aneurysmal subarachnoid hemorrhage if multimodal monitoring was established due to poor neurological condition. ICP and TEMP values were obtained from ventricular catheters and systemic temperature sensors. Repeated NIRS-ICG measurements (2 injections within 30 minutes) were performed daily for determination of cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time of ICG (mttICG). Delayed cerebral ischemia was defined as brain tissue oxygen tension 35. Results: A total of 128 NIRS-ICG measurements were performed in 10 patients. The correlation coefficient between ICP and TEMP values obtained with the NIRS-ICP probe and values from routine monitoring was r=0.72 and r=0.96, respectively. The mean value was 30.3 ± 13.6 ml/100g/min for CBF, 3.3 ± 1.2 ml/100g for CBV, and 6.8 ± 1.6 sec for mttICG. The coefficient of variation from repeated NIRS-ICG measurements was 10.9% for CBF, 11.7% for CBV, and 3.8% for mttICG. The sensitivity for delayed cerebral ischemia detection was 85% and the specificity 83% using a CBFthreshold of 25 ml/100g/min. Conclusion: Multimodal monitoring using the NIRS-ICP probe is feasible with high reproducibility of measurement values and the ability to detect delayed cerebral ischemia. No safety concerns exist for the routine clinical use of the NIRS-ICP probe