Multimodal neuromonitoring for traumatic brain injury management
Multimodal neuromonitoring for traumatic brain injury management is primarily performed in neurointensive care units to prevent secondary harmful brain insults and facilitate patient recovery. Several metrics are commonly monitored using both invasive and non-invasive techniques. The Guidelines for the Management of Severe Traumatic Brain Injury, Fourth Edition from 2016 provides recommendations and thresholds for some of these. Still, high-level evidence for several metrics and thresholds is lacking.
Methods: Regarding invasive brain monitoring, intracranial pressure (ICP) forms the cornerstone, and pressures above 22 mmHg should be avoided. From ICP, cerebral perfusion pressure (CPP) (mean arterial pressure (MAP)-ICP) and pressure reactivity index (PRx) (a correlation between slow waves MAP and ICP as a surrogate for cerebrovascular reactivity) may be derived. In terms of regional monitoring, partial brain tissue oxygen pressure (PbtO2) is commonly used, and phase 3 studies are currently ongoing to determine its added effect to outcome together with ICP monitoring. Cerebral microdialysis (CMD) is another regional invasive modality to measure substances in the brain extracellular fluid. International consortiums have suggested thresholds and management strategies, in spite of lacking high-level evidence. Although invasive monitoring is generally safe, iatrogenic hemorrhages are reported in about 10% of cases, but these probably do not significantly affect long-term outcome. Non-invasive monitoring is relatively recent in the field of TBI care, and research is usually from single-center retrospective experiences. Near-infrared spectrometry (NIRS) measuring regional tissue saturation has been shown to be associated with outcome. Transcranial doppler (TCD) has several tentative utilities in TBI like measuring ICP and detecting vasospasm. Furthermore, serial sampling of biomarkers of brain injury in the blood can be used to detect secondary brain injury development.
In multimodal monitoring, the most important aspect is data interpretation, which requires knowledge of each metric's strengths and limitations. Combinations of several modalities might make it possible to discern specific pathologic states suitable for treatment. However, the cost-benefit should be considered as the incremental benefit of adding several metrics has a low level of evidence, thus warranting additional research 1).
Reviews
Bögli et al. aimed to provide clinicians, researchers, and healthcare professionals with detailed, compelling examples of potential applications of multimodality neuromonitoring, focused on high-resolution modalities within the field of traumatic brain injury. This case series showcases how neuromonitoring techniques such as intracranial pressure, brain tissue oxygenation, near-infrared spectroscopy, and transcranial Doppler can be integrated with cerebral microdialysis, neuroimaging, and systemic physiology monitoring. The aim is to demonstrate the value of a multimodal approach based on high-resolution data and derived indices integrated in one monitoring tool. This allows for improving the diagnosis, monitoring, and treatment of patients with traumatic brain injury. For this purpose, key concepts are covered, and various cases have been described to illustrate how to make the most of this advanced monitoring technology 2).