Current state of high-fidelity multimodal monitoring in traumatic brain injury

Abstract

Introduction Multimodality monitoring of patients with severe traumatic brain injury (TBI) is primarily performed in neuro-critical 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 latest Brain Trauma Foundation guidelines from 2016 provide 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. Conclusions 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.

Multi-Mechanistic Approaches to the Treatment of Traumatic Brain Injury: A Review

“…Multimodal neuromonitoring (MMM) entails the measurement and integration of multiple biological parameters to better understand a patient’s pathophysiologic state and guide treatment decisions [ 107 ]. Measurement of cerebral physical, metabolic, and electrical physiologic parameters through MMM sensors allows for the collection of a wide range of physiologic and pathophysiological data.…”

“…Among the most commonly studied MMM parameters are intracranial pressure (ICP), cerebral perfusion pressure (CPP), and cerebrovascular autoregulatory capability (PRx). As elevated ICP reduces CPP and prevents optimal brain perfusion, evidence-based guidelines recommend ICP monitoring for patients with severe TBI [ 10 , 107 , 120 ], as well as establishing ICP and CPP-based thresholds for pharmacologic and surgical interventions [ 10 ]. TBI treatment based on MMM-derived optimal cerebral perfusion has demonstrated improved clinical outcomes, especially in older patients who may have reduced autoregulatory capacity [ 114 ].…”

“…Measurement of P bt O 2 , CPP and arterial oxygen saturation has been used to guide treatment of cerebral hypoxia in severe TBI, helping to uncover physiologic states that may lead to impaired brain oxygen metabolism [ 115 ]. CMD-based parameters, including LPR and pH, can directly characterize cerebral metabolic states, including ischemia, metabolic stress, and mitochondrial dysfunction [ 107 , 124 ], and has been shown to predict cerebral metabolic crisis and disruptions in cerebral perfusion requiring therapeutic intervention [ 110 , 119 ]. The identification of metabolic derangement, including mitochondrial dysfunction via CMD-based MMM, has also been used to guide targeted metabolic treatment of TBI [ 111 ].…”

Intracerebral hematomas are capable of altering air-pouch intracranial pressure monitoring

“…The clinical relevance of ICP monitoring has been demonstrated in a myriad of studies and treatment parameters guided by ICP have been associated with improved outcome(s) and mortality. [3,10,11] A threshold of 22 mmHg has been de ned as pathological by the Brain Trauma Foundation guidelines; such ICPs warrant an escalation of medical and/or surgical care. [1] Therefore, a simple and reliable measure of ICP is crucial as physicians/surgeons manage critical ill patients.…”

Intracerebral Hematomas are Capable of Altering Air-Pouch Intracranial Pressure Monitoring

“…The clinical relevance of ICP monitoring has been demonstrated in a myriad of studies and treatment parameters guided by ICP have been associated with improved outcome(s) and mortality. [3,10,11] A threshold of 22 mmHg has been defined as pathological by the Brain Trauma Foundation guidelines; such ICPs warrant an escalation of medical and/or surgical care. [1] Therefore, a simple and reliable measure of ICP is crucial as physicians/surgeons manage critical ill patients.…”