Early detection of delayed traumatic intracranial hematomas using near-infrared spectroscopy

The Development of Non-Invasive Optical Brain Pulse Monitoring: A Review

Early detection of neurological deterioration in serious acute brain injury is seen as an important goal to reduce death and disability, but monitoring for neurological deterioration remains challenging. Routine methods, such as neurological examination and brain imaging, often identify brain injuries only after they have progressed to an irreversible stage. Alternate approaches such as invasive brain monitoring, are complex, costly and carry inherent risks. The optical brain pulse monitor (OBPM) is a novel, non-invasive, safe, and continuous monitoring device designed to provide earlier detection of neurological deterioration and address the limitations of traditional approaches. This review presents the development, technical aspects, and clinical results from past and ongoing trials over the last five years.

Preliminary experience with diffuse correlation spectroscopy in acute ischemic stroke neurointerventional procedures

BACKGROUND

Diffuse correlation spectroscopy (DCS) is a non-invasive optical technique that enables continuous blood flow measurements in various organs, including the brain. DCS quantitatively measures blood flow from temporal fluctuations in the intensity of diffusely reflected light caused by the dynamic scattering of light from moving red blood cells within the tissue.

METHODS

We performed bilateral cerebral blood flow (CBF) measurements using a custom DCS device in patients undergoing neuroendovascular interventions for acute ischemic stroke. Experimental, clinical, and imaging data were collected in a prospective manner.

RESULTS

The device was successfully applied in nine subjects. There were no safety concerns or interference with the standard angiography suite or intensive care unit workflow. Six cases were selected for final analysis and interpretation. DCS measurements with photon count rates greater than 30 KHz had sufficient signal-to-noise to resolve blood flow pulsatility. We found an association between angiographic changes in cerebral reperfusion (partial or complete reperfusion established in stroke thrombectomy cases; temporary flow arrest during carotid artery stenting) and those observed intraprocedurally with CBF measurements via DCS. Limitations of the current technology included sensitivity to the interrogated tissue volume under the probe and the effect of local changes in tissue optical properties on the accuracy of CBF estimates.

CONCLUSION

Our initial experience with DCS in neurointerventional procedures showed the feasibility of this non-invasive approach in providing continuous measurement of regional CBF brain tissue properties.

Cerebrovascular Responses in a Patient with Lundberg B Waves Following Subarachnoid Haemorrhage Assessed with a Novel Non-Invasive Brain Pulse Monitor: A Case Report

Subarachnoid haemorrhage (SAH) can trigger a range of poorly understood cerebrovascular responses that may play a role in delayed cerebral ischemia. The brain pulse monitor is a novel non-invasive device that detects a brain photoplethysmography signal that provides information on intracranial pressure (ICP), compliance, blood flow and tissue oxygen saturation. We monitored the cerebrovascular responses in a patient with Lundberg B waves following a SAH. The patient presented with a Fischer grade 4 SAH that required urgent left posterior communicating artery aneurysm coiling and ventricular drain insertion. On hospital day 4 oscillations or spikes on the invasive ICP were noted, consistent with Lundberg B waves. Brain pulse monitoring demonstrated concurrent pulse waveform features consistent with reduced brain compliance and raised ICP over both brain hemispheres. Oxygen levels also demonstrated slow oscillations correlated with the ICP spikes. Brief infrequent episodes of reduced and absent brain pulses were also noted over the right hemisphere. Our findings suggest that the brain pulse monitor holds promise for early detection of delayed cerebral ischemia and could offer insights into the vascular mechanisms at play.

Transfontanelle photoacoustic imaging of intraventricular brain hemorrhages in live sheep

Intraventricular (IVH) and periventricular (PVH) hemorrhages in preterm neonates are common because the periventricular blood vessels are still developing up to 36 weeks and are fragile. Currently, transfontanelle ultrasound (US) imaging is utilized for screening for IVH and PVH, largely through the anterior fontanelle. However for mild hemorrhages, inconclusive diagnoses are common, leading to failure to detect IVH/PVH or, when other clinical symptoms are present, use of second stage neuroimaging modalities requiring transport of vulnerable patients. Yet even mild IVH/PVH increases the risk of moderate-severe neurodevelopmental impairment. Here, we demonstrate the capability of transfontanelle photoacoustic imaging (TFPAI) to detect IVH and PVH in-vivo in a large animal model. TFPAI was able to detect IVH/PVH as small as 0.3 mL in volume in the brain (p < 0.05). By contrast, US was able to detect hemorrhages as small as 0.5 mL. These preliminary results suggest TFPAI could be translated into a portable bedside imaging probe for improved diagnosis of clinically relevant brain hemorrhages in neonates.

Development and characterization of transfontanelle photoacoustic imaging system for detection of intracranial hemorrhages and measurement of brain oxygenation: Ex-vivo

We have developed and optimized an imaging system to study and improve the detection of brain hemorrhage and to quantify oxygenation. Since this system is intended to be used for brain imaging in neonates through the skull opening, i.e., fontanelle, we called it, Transfontanelle Photoacoustic Imaging (TFPAI) system. The system is optimized in terms of optical and acoustic designs, thermal safety, and mechanical stability. The lower limit of quantification of TFPAI to detect the location of hemorrhage and its size is evaluated using in-vitro and ex-vivo experiments. The capability of TFPAI in measuring the tissue oxygenation and detection of vasogenic edema due to brain blood barrier disruption are demonstrated. The results obtained from our experimental evaluations strongly suggest the potential utility of TFPAI, as a portable imaging modality in the neonatal intensive care unit. Confirmation of these findings in-vivo could facilitate the translation of this promising technology to the clinic.

Functional near-infrared spectroscopy in pediatric clinical research: Different pathophysiologies and promising clinical applications

Over its 30 years of existence, functional near-infrared spectroscopy (fNIRS) has matured into a highly versatile tool to study brain function in infants and young children. Its advantages, amongst others, include its ease of application and portability, the option to combine it with electrophysiology, and its relatively good tolerance to movement. As shown by the impressive body of fNIRS literature in the field of cognitive developmental neuroscience, the method's strengths become even more relevant for (very) young individuals who suffer from neurological, behavioral, and/or cognitive impairment. Although a number of studies have been conducted with a clinical perspective, fNIRS cannot yet be considered as a truly clinical tool. The first step has been taken in this direction by studies exploring options in populations with well-defined clinical profiles. To foster further progress, here, we review several of these clinical approaches to identify the challenges and perspectives of fNIRS in the field of developmental disorders. We first outline the contributions of fNIRS in selected areas of pediatric clinical research: epilepsy, communicative and language disorders, and attention-deficit/hyperactivity disorder. We provide a scoping review as a framework to allow the highlighting of specific and general challenges of using fNIRS in pediatric research. We also discuss potential solutions and perspectives on the broader use of fNIRS in the clinical setting. This may be of use to future research, targeting clinical applications of fNIRS in children and adolescents.

Transfontanelle photoacoustic imaging for in-vivo cerebral oxygenation measurement

The capability of photoacoustic (PA) imaging to measure oxygen saturation through a fontanelle has been demonstrated in large animals in-vivo. We called this method, transfontanelle photoacoustic imaging (TFPAI). A surgically induced 2.5 cm diameter cranial window was created in an adult sheep skull to model the human anterior fontanelle. The performance of the TFPAI has been evaluated by comparing the PA-based predicted results against the gold standard of blood gas analyzer measurements.

Near-infrared spectroscopy for intracranial hemorrhage detection in traumatic brain injury patients: A systematic review

PURPOSE

To synthesize evidence of the use of near-infrared spectroscopy (NIRS) to detect intracranial hemorrhage in traumatic brain injury (TBI) patients.

METHODS

The literature search was conducted in PubMed and Google Scholar (from inception to July 2021).

RESULTS

216 original articles were found, 197 of which were omitted, and the final review contained 19 original articles covering 2291 patients.

CONCLUSION

For patients with TBI, a NIRS test may be useful as a screening tool for intracranial hemorrhage, especially at the prehospital level. Negative results may help rule out intracranial hemorrhage and may remove the need for more head computed tomography (CT) scanning. Prehospital testing may guide the decision of whether the patient should be transferred to a craniotomy-equipped specialized hospital. NIRS can also be useful in situations when CT is not available. For future research, a significant objective is to show whether the effects of NIRS can improve outcomes and lead to meaningful improvements in clinical practice and decision making.

Near Infrared Spectroscopy for High-Temporal Resolution Cerebral Physiome Characterization in TBI: A Narrative Review of Techniques, Applications, and Future Directions

Multimodal monitoring has been gaining traction in the critical care of patients following traumatic brain injury (TBI). Through providing a deeper understanding of the individual patient's comprehensive physiologic state, or "physiome," following injury, these methods hold the promise of improving personalized care and advancing precision medicine. One of the modalities being explored in TBI care is near-infrared spectroscopy (NIRS), given it's non-invasive nature and ability to interrogate microvascular and tissue oxygen metabolism. In this narrative review, we begin by discussing the principles of NIRS technology, including spatially, frequency, and time-resolved variants. Subsequently, the applications of NIRS in various phases of clinical care following TBI are explored. These applications include the pre-hospital, intraoperative, neurocritical care, and outpatient/rehabilitation setting. The utility of NIRS to predict functional outcomes and evaluate dysfunctional cerebrovascular reactivity is also discussed. Finally, future applications and potential advancements in NIRS-based physiologic monitoring of TBI patients are presented, with a description of the potential integration with other omics biomarkers.

Neurological deteriorations in mild brain injuries: the strategy of evaluation and management

PURPOSE

Most mild traumatic brain injuries (TBIs) can be treated conservatively. However, some patients deteriorate during observation. Therefore, we tried to evaluate the characteristics of deterioration and requirement for further management in mild TBI patients.

METHODS

From 1/1/2017 to 12/31/2017, patients with mild TBI and positive results on CT scans of the brain were retrospectively studied. Patients with and without neurological deteriorations were compared. The characteristics of mild TBI patients with further neurological deterioration or the requirement for interventions were delineated.

RESULTS

One hundred ninety-two patients were enrolled. Twenty-three (12.0%) had neurological deteriorations. The proportions of deterioration occurring within 24 h, 48 h and 72 h were 23.5, 41.2 and 58%, respectively. Deteriorated patients were significantly older than those without neurological deteriorations (69.7 vs. 60.2; p = 0.020). More associated extracranial injuries were observed in deteriorated patients [injury severity score (ISS): 20.2 vs. 15.9; p = 0.005). Significantly higher proportions of intraventricular hemorrhage (8.7 vs. 1.2%; p = 0.018) and multiple lesions (78.3 vs. 53.8%; p = 0.027) were observed on the CT scans of patients with neurological deteriorations. Subset analysis showed that deteriorated patients who required neurosurgical interventions (N = 7) had significantly more initial GCS defects (13 or 14) (71.4 vs. 12.5%; p = 0.005) and more initial decreased muscle power of extremities (85.7 vs. 18.8%; p = 0.002).

CONCLUSION

More attention should be given to mild TBI patients with older age, GCS defects, decreased muscle power of the extremities, multiple lesions on CT scans and other systemic injuries (high ISS). Most deteriorations occur within 72 h after trauma.

Near-Infrared Spectroscopy (NIRS) in Traumatic Brain Injury (TBI)

Traumatic brain injury (TBI) occurs when a sudden trauma causes damage to the brain. TBI can result when the head suddenly and violently impacts an object or when an object pierces the skull and enters brain tissue. Secondary injuries after traumatic brain injury (TBI) can lead to impairments on cerebral oxygenation and autoregulation. Considering that secondary brain injuries often take place within the first hours after the trauma, noninvasive monitoring might be helpful in providing early information on the brain's condition. Near-infrared spectroscopy (NIRS) is an emerging noninvasive monitoring modality based on chromophore absorption of infrared light with the capability of monitoring perfusion of the brain. This review investigates the main applications of NIRS in TBI monitoring and presents a thorough revision of those applications on oxygenation and autoregulation monitoring. Databases such as PubMed, EMBASE, Web of Science, Scopus, and Cochrane library were utilized in identifying 72 publications spanning between 1977 and 2020 which were directly relevant to this review. The majority of the evidence found used NIRS for diagnosis applications, especially in oxygenation and autoregulation monitoring (59%). It was not surprising that nearly all the patients were male adults with severe trauma who were monitored mostly with continue wave NIRS or spatially resolved spectroscopy NIRS and an invasive monitoring device. In general, a high proportion of the assessed papers have concluded that NIRS could be a potential noninvasive technique for assessing TBI, despite the various methodological and technological limitations of NIRS.

Combination Therapy Using Prothrombin Complex Concentrate and Vitamin K in Anticoagulated Patients with Traumatic Intracranial Hemorrhage Prevents Progressive Hemorrhagic Injury: A Historically Controlled Study

Warfarin remains crucially involved in the treatment of patients at thrombotic or thromboembolic risk. However, warfarin increases the mortality rate among patients with traumatic intracranial hemorrhage (TICH) through progressive hemorrhagic injury (PHI). Therefore, a rapid anticoagulation reversal could be required in patients with TICH to prevent PHI. Differences in the warfarin reversal effect between combination therapy of prothrombin complex concentrate (PCC) with vitamin K (VK) and VK monotherapy remain unclear. However, studies have reported that PCC has greater effectiveness and safety for warfarin reversal compared with fresh frozen plasma (FFP). This retrospective study aimed to evaluate the warfarin reversal effects of combination therapy of PCC with VK and VK monotherapy on TICH. We compared the clinical outcomes between the periods before and after the PCC introduction in our hospital. There were 13 and 7 patients who received VK monotherapy and PCC with VK, respectively. PHI predictors were evaluated using univariate regression analyses. Warfarin reversal using PCC had a significant negative association with PHI (odds ratio: 0.03, 95% confidence interval: 0.00-0.41, P = 0.004). None of the patients presented with thrombotic complications. Warfarin reversal through a combination of PCC with VK could be more effective for inhibiting post-trauma PHI compared with VK monotherapy. This could be attributed to a rapid and stable warfarin reversal. PCC should be administered to patients with TICH taking warfarin for PHI prevention.

Cerebral ischemia detection using artificial intelligence (CIDAI)-A study protocol

BACKGROUND

The onset of cerebral ischemia is difficult to predict in patients with altered consciousness using the methods available. We hypothesize that changes in Heart Rate Variability (HRV), Near-Infrared Spectroscopy (NIRS), and Electroencephalography (EEG) correlated with clinical data and processed by artificial intelligence (AI) can indicate the development of imminent cerebral ischemia and reperfusion, respectively. This study aimed to develop a method that enables detection of imminent cerebral ischemia in unconscious patients, noninvasively and with the support of AI.

METHODS

This prospective observational study will include patients undergoing elective surgery for carotid endarterectomy and patients undergoing acute endovascular embolectomy for cerebral arterial embolism. HRV, NIRS, and EEG measurements and clinical information on patient status will be collected and processed using machine learning. The study will take place at Sahlgrenska University Hospital, Gothenburg, Sweden. Inclusion will start in September 2020, and patients will be included until a robust model can be constructed. By analyzing changes in HRV, EEG, and NIRS measurements in conjunction with cerebral ischemia or cerebral reperfusion, it should be possible to train artificial neural networks to detect patterns of impending cerebral ischemia. The analysis will be performed using machine learning with long short-term memory artificial neural networks combined with convolutional layers to identify patterns consistent with cerebral ischemia and reperfusion.

DISCUSSION

Early signs of cerebral ischemia could be detected more rapidly by identifying patterns in integrated, continuously collected physiological data processed by AI. Clinicians could then be alerted, and appropriate actions could be taken to improve patient outcomes.

Limitations of Cerebral Oximetry in a Patient With an Intracerebral Hemorrhage and Brain Edema on Extracorporeal Membrane Oxygenation: A Case Report

Regional cerebral tissue saturation monitoring is frequently used in patients on mechanical cardiac assist devices with the intention to promptly detect critical imbalances between cerebral oxygen delivery and oxygen extraction and ultimately circumvent permanent brain injury. We report a case where an intraparenchymal bleed in the supply zone of the middle cerebral artery-followed by severe hemispherical brain edema, leading to life-threatening intracranial hypertension-escaped cerebral oximetry monitoring using near-infrared spectroscopy. Potential explanations for our observation, as well as the specific limitations of these devices, are discussed.

Non-invasive High Frequency Median Nerve Stimulation Effectively Suppresses Olfactory Intensity Perception in Healthy Males

Median nerve stimulation (MNS) had been performed in the existing literature to alleviate symptoms of nausea and vomiting. The observed facilitative effects are thought to be mediated by the vagal pathways, particularly the vagus nerve (VN) brainstem nuclei of the dorsal motor nucleus of vagus and nucleus tractus solitarius (DMV-NTS). Sense of smell is one of the major sensory modalities for inducing vomiting and nausea as a primary defense against potentially harmful intake of material. This study aimed to test effects of non-invasive, high and low frequency MNS on human olfactory functioning, with supplementary exploration of the orbitofrontal cortex (OFC) using near-infrared spectroscopy (NIRS). Twenty healthy, male, adults performed supra-threshold odor intensity tests (labeled magnitude scale, LMS) for four food-related odorant samples (presented in three different concentrations) before and after receiving high-, low frequency MNS and placebo (no stimulation), while cortical activities in the OFC was monitored by the NIRS. Data of the NIRS and LMS test of separate stimulation parameters were statistically analyzed using mixed-model analysis of variance (ANOVA). Only the high frequency MNS showed effects for suppressing the intensity perception of the moderate concentration of Amyl Acetate (p:0.042) and strong concentration of Isovaleric Acid (p:0.004) and 1-Octen-3-ol (p:0.006). These behavioral changes were coupled with significant changes in the NIRS recordings of the left (p:0.000) and right (p:0.003) hemispheric orbitofrontal cortices. This is the first study that applied non-invasive, high frequency MNS to suppress the supra-threshold odor ratings of specific concentrations of odors. The vagal networks are potential relays of MNS to influence OFC. Results from the current article implore further research into non-invasive, high frequency MNS in the investigation of its modulatory effects on olfactory function, given its potential to be used for ameliorating nausea and malnutrition associated with various health conditions.

The Effects of Filgrastim on Complications of Patients with Cerebral Hemorrhage Due To Head Trauma

BACKGROUND

Filgrastim, a neopogen brand, is a blood-forming agent and a natural protein in the body that plays a role in stimulating the growth of white blood cells and protecting them against infectious agents. To the best of knowledge, human and animal specimens have shown the effect of Filgrastim on treating brain injuries regarding bone marrow transfusion into the blood, neuroprotection, stimulation of neurons for forming new neural networks and reducing the risk of bacterial infections.

AIM

This study aimed to investigate the effect of Filgrastim on the prognosis of a cerebral haemorrhage in patients with traumatic brain injury.

METHODS

This study was conducted as a clinical trial, in which the initial diagnosis of patients with cerebral haemorrhage due to head trauma was performed with a clinical examination and CT scan. After the patient arrives at the emergency room, the patient's initial examination is performed, and blood tests are taken from the patient. Moreover, CBC values (Hb, Platelet, Hematocrit) were checked and recorded in the checklist. The intervention group received 150 mcg/day Filgrastim injected subcutaneously for 4 days. Furthermore, patients in the control group received the same amount of sterile water. At the end of the treatment period, blood tests were performed again in all patients, and their results were then recorded. All data were analysed by SPSS v.21 software package.

RESULTS

Our findings revealed that the mean volume of bleeding in the intervention group based on CT scan was significantly reduced after four days as compared to the control group. Moreover, the mean score of consciousness and muscular strength of patients in the intervention group was significantly higher than the control group. Also, WBCs in the intervention group exhibited a significant increase after four days of intervention, while platelet and hematocrit levels in the intervention group decreased significantly compared to the control group.

CONCLUSION

Regarding the results, the therapeutic application of filtration is considered to be effective. Given the lack of serious complications of the proposed dosages, the use of this drug can be suggested.

Improvement of Olfactory Function With High Frequency Non-invasive Auricular Electrostimulation in Healthy Humans

In past literature on animal models, invasive vagal nerve stimulation using high frequencies has shown to be effective at modulating the activity of the olfactory bulb (OB). Recent advances in invasive vagal nerve stimulation in humans, despite previous findings in animal models, used low frequency stimulation and found no effect on the olfactory functioning. The present article aimed to test potential effects of non-invasive, high and low frequency vagal nerve stimulation in humans, with supplementary exploration of the orbitofrontal cortex using near-infrared spectroscopy (NIRS). Healthy, male adult participants (n = 18) performed two olfactory tests [odor threshold test (OTT) and supra-threshold test (STT)] before and after receiving high-, low frequency vagal nerve stimulation and placebo (no stimulation). Participant's olfactory functioning was monitored using NIRS, and assessed with two behavioral olfactory tests. NIRS data of separate stimulation parameters were statistically analyzed using repeated-measures ANOVA across different stages. Data from olfactory tests were analyzed using paired parametric and non-parametric statistical tests. Only high frequency, non-invasive vagal nerve stimulation was able to positively modulate the performance of the healthy participants in the STT (p = 0.021, Wilcoxon sign-ranked test), with significant differences in NIRS (p = 0.014, post-hoc with Bonferroni correction) recordings of the right hemispheric, orbitofrontal cortex. The results from the current article implore further exploration of the neurocircuitry involved under vagal nerve stimulation and the effects of non-invasive, high frequency, vagal nerve stimulation toward olfactory dysfunction which showcase in Parkinson's and Alzheimer's Diseases. Despite the sufficient effect size (moderate effect, correlation coefficient (r): 0.39 for the STT) of the current study, future research should replicate the current findings with a larger cohort.

Italian guidelines on the assessment and management of pediatric head injury in the emergency department

OBJECTIVE

We aim to formulate evidence-based recommendations to assist physicians decision-making in the assessment and management of children younger than 16 years presenting to the emergency department (ED) following a blunt head trauma with no suspicion of non-accidental injury.

METHODS

These guidelines were commissioned by the Italian Society of Pediatric Emergency Medicine and include a systematic review and analysis of the literature published since 2005. Physicians with expertise and experience in the fields of pediatrics, pediatric emergency medicine, pediatric intensive care, neurosurgery and neuroradiology, as well as an experienced pediatric nurse and a parent representative were the components of the guidelines working group. Areas of direct interest included 1) initial assessment and stabilization in the ED, 2) diagnosis of clinically important traumatic brain injury in the ED, 3) management and disposition in the ED. The guidelines do not provide specific guidance on the identification and management of possible associated cervical spine injuries. Other exclusions are noted in the full text.

CONCLUSIONS

Recommendations to guide physicians practice when assessing children presenting to the ED following blunt head trauma are reported in both summary and extensive format in the guideline document.

Intracranial Hematoma Detection by Near Infrared Spectroscopy in a Helicopter Emergency Medical Service: Practical Experience

In (helicopter) emergency medical services, (H)EMS, the prehospital detection of intracranial hematomas should improve patient care and the triage to specialized neurosurgical hospitals. Recently, noninvasive detection of intracranial hematomas became possible by applying transcranial near infrared spectroscopy (NIRS). Herein, second-generation devices are currently available, for example, the Infrascanner 2000 (Infrascan), that appear suited also for prehospital (H)EMS applications. Since (H)EMS operations are time-critical, we studied the Infrascanner 2000 as a “first-time-right” monitor in healthy volunteers (n = 17, hospital employees, no neurologic history). Further, we studied the implementation of the Infrascanner 2000 in a European HEMS organization (Lifeliner 1, Amsterdam, The Netherlands). The principal results of our study were as follows: The screening for intracranial hematomas in healthy volunteers with first-time-right intention resulted in a marked rate of virtual hematomas (false positive results, i.e., 12/17), rendering more time consuming repeat measurements advisable. The results of the implementation of the Infrascanner in HEMS suggest that NIRS-based intracranial hematoma detection is feasible in the HEMS setting. However, some drawbacks exist and their possible solutions are discussed. Future studies will have to demonstrate how NIRS-based intracranial hematoma detection will improve prehospital decision making in (H)EMS and ultimately patient outcome.

Application of optical methods in the monitoring of traumatic brain injury: A review

We present an overview of the wide range of potential applications of optical methods for monitoring traumatic brain injury. The MEDLINE database was electronically searched with the following search terms: "traumatic brain injury," "head injury," or "head trauma," and "optical methods," "NIRS," "near-infrared spectroscopy," "cerebral oxygenation," or "cerebral oximetry." Original reports concerning human subjects published from January 1980 to June 2015 in English were analyzed. Fifty-four studies met our inclusion criteria. Optical methods have been tested for detection of intracranial lesions, monitoring brain oxygenation, assessment of brain perfusion, and evaluation of cerebral autoregulation or intracellular metabolic processes in the brain. Some studies have also examined the applicability of optical methods during the recovery phase of traumatic brain injury . The limitations of currently available optical methods and promising directions of future development are described in this review. Considering the outstanding technical challenges, the limited number of patients studied, and the mixed results and opinions gathered from other reviews on this subject, we believe that optical methods must remain primarily research tools for the present. More studies are needed to gain confidence in the use of these techniques for neuromonitoring of traumatic brain injury patients.

Brain Oxygenation Monitoring

A mismatch between cerebral oxygen supply and demand can lead to cerebral hypoxia/ischemia and deleterious outcomes. Cerebral oxygenation monitoring is an important aspect of multimodality neuromonitoring. It is increasingly deployed whenever intracranial pressure monitoring is indicated. Although there is a large body of evidence demonstrating an association between cerebral hypoxia/ischemia and poor outcomes, it remains to be determined whether restoring cerebral oxygenation leads to improved outcomes. Randomized prospective studies are required to address uncertainties about cerebral oxygenation monitoring and management. This article describes the different methods of monitoring cerebral oxygenation, their indications, evidence base, limitations, and future perspectives.

Clinical application of near-infrared spectroscopy in patients with traumatic brain injury: a review of the progress of the field

Near-infrared spectroscopy (NIRS) is a technique by which the interaction between light in the near-infrared spectrum and matter can be quantitatively measured to provide information about the particular chromophore. Study into the clinical application of NIRS for traumatic brain injury (TBI) began in the 1990s with early reports of the ability to detect intracranial hematomas using NIRS. We highlight the advances in clinical applications of NIRS over the past two decades as they relate to TBI. We discuss recent studies evaluating NIRS techniques for intracranial hematoma detection, followed by the clinical application of NIRS in intracranial pressure and brain oxygenation measurement, and conclude with a summary of potential future uses of NIRS in TBI patient management.

Progressive hemorrhagic injury after severe traumatic brain injury: effect of hemoglobin transfusion thresholds

OBJECT There is limited literature available to guide transfusion practices for patients with severe traumatic brain injury (TBI). Recent studies have shown that maintaining a higher hemoglobin threshold after severe TBI offers no clinical benefit. The present study aimed to determine if a higher transfusion threshold was independently associated with an increased risk of progressive hemorrhagic injury (PHI), thereby contributing to higher rates of morbidity and mortality. METHODS The authors performed a secondary analysis of data obtained from a recently performed randomized clinical trial studying the effects of erythropoietin and blood transfusions on neurological recovery after severe TBI. Assigned hemoglobin thresholds (10 g/dl vs 7 g/dl) were maintained with packed red blood cell transfusions during the acute phase after injury. PHI was defined as the presence of new or enlarging intracranial hematomas on CT as long as 10 days after injury. A severe PHI was defined as an event that required an escalation of medical management or surgical intervention. Clinical and imaging parameters and transfusion thresholds were used in a multivariate Cox regression analysis to identify independent risk factors for PHI. RESULTS Among 200 patients enrolled in the trial, PHI was detected in 61 patients (30.5%). The majority of patients with PHI had a new, delayed contusion (n = 29) or an increase in contusion size (n = 15). The mean time interval between injury and identification of PHI was 17.2 ± 15.8 hours. The adjusted risk of severe PHI was 2.3 times higher for patients with a transfusion threshold of 10 g/dl (95% confidence interval 1.1-4.7; p = 0.02). Diffuse brain injury was associated with a lower risk of PHI events, whereas higher initial intracranial pressure increased the risk of PHI (p < 0.001). PHI was associated with a longer median length of stay in the intensive care unit (18.3 vs 14.4 days, respectively; p = 0.04) and poorer Glasgow Outcome Scale scores (42.9% vs 25.5%, respectively; p = 0.02) at 6 months. CONCLUSIONS A higher transfusion threshold of 10 g/dl after severe TBI increased the risk of severe PHI events. These results indicate the potential adverse effect of using a higher hemoglobin transfusion threshold after severe TBI.

Evidence for cerebral edema, cerebral perfusion, and intracranial pressure elevations in acute mountain sickness

INTRODUCTION

We hypothesized that cerebral alterations in edema, perfusion, and/or intracranial pressure (ICP) are related to the development of acute mountain sickness (AMS).

METHODS

To vary AMS, we manipulated ambient oxygen, barometric pressure, and exercise duration. Thirty-six subjects were tested before, during and after 8 h exposures in (1) normobaric normoxia (NN; 300 m elevation equivalent); (2) normobaric hypoxia (NH; 4400 m equivalent); and (3) hypobaric hypoxia (HH; 4400 m equivalent). After a passive 15 min ascent, each subject participated in either 10 or 60 min of cycling exercise at 50% of heart rate reserve. We measured tissue absorption and scattering via radio-frequency near-infrared spectroscopy (NIRS), optic nerve sheath diameter (ONSD) via ultrasound, and AMS symptoms before, during, and after environmental exposures.

RESULTS

We observed significant increases in NIRS tissue scattering of 0.35 ± 0.11 cm(-1) (P = 0.001) in subjects with AMS (i.e., AMS+), consistent with mildly increased cerebral edema. We also noted a small, but significant increase in total hemoglobin concentrations with AMS+, 3.2 ± 0.8 μmolL(-1) (P < 0.0005), consistent with increased cerebral perfusion. No effect of exercise duration was found, nor did we detect differences between NH and HH. ONSD assays documented a small but significant increase in ONSD (0.11 ± 0.02 mm; P < 0.0005) with AMS+, suggesting mildly elevated ICP, as well as further increased ONSD with longer exercise duration (P = 0.005).

CONCLUSION

In AMS+, we found evidence of cerebral edema, elevated cerebral perfusion, and elevated ICP. The observed changes were small but consistent with the reversible nature of AMS.

Evaluation of traumatic brain injury by optical technique

Background

Traumatic brain injury (TBI), usually due to brain shaking or impact, affects the normal brain function and may lead to severe disability or even death. However, there is paucity of information regarding changes in the physiologic state of humans or animals after brain shaking.

Methods

In this study, near-infrared spectroscopy (NIRS) was used to continuously monitor the concentration change of oxy-hemoglobin (HbO2) and deoxy-hemoglobin (HbR) to understand changes in the physiological state during and after brain shaking. Laser Doppler flowmetry was also used to monitor changes in cerebral blood flow under TBI to supplement the investigation. Triphenyltetrazolium chloride (TTC) staining was used to monitor changes of infarction volume corresponding to different impact strengths.

Result

The experimental results indicated that concentration changes of HbO2 and total-hemoglobin (HbT) were significantly related to the impact strength. The infarction volume was also significantly related to the impact strength.

Conclusion

Therefore, the non-invasive monitoring of concentration changes in HbO₂, HbR, and HbT using NIRS may have a clinical application for the evaluation of TBI.

NIR light propagation in a digital head model for traumatic brain injury (TBI)

Near infrared spectroscopy (NIRS) is capable of detecting and monitoring acute changes in cerebral blood volume and oxygenation associated with traumatic brain injury (TBI). Wavelength selection, source-detector separation, optode density, and detector sensitivity are key design parameters that determine the imaging depth, chromophore separability, and, ultimately, clinical usefulness of a NIRS instrument. We present simulation results of NIR light propagation in a digital head model as it relates to the ability to detect intracranial hematomas and monitor the peri-hematomal tissue viability. These results inform NIRS instrument design specific to TBI diagnosis and monitoring.

Near-infrared spectroscopy system for determining brain hemoglobin level

Traumatic brain injury (TBI) usually results from brain shaking or impact. It can affect the normal function of the brain and even cause people become disabled and death. However, there is lack of studies for the physiological changes of humans or animals under brain injury. In order to obtain the information of physiological state change, we designed and enforced a non-invasive, wireless multi-channel near-infrared spectroscopy (NIRS) for monitoring the concentration change of oxy-hemoglobin (HbO2), deoxy-hemoglobin (HbR) and total-hemoglobin (HbT) continuously during and after TBI. The experimental results indicated that the concentration change of HbO2 and HbT is significantly related to the impact strength and infarction volume. Thus, this system is easily used and stable for TBI study.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

The use of handheld near-infrared device (Infrascanner)for detecting intracranial haemorrhages in children with minor head injury

OBJECTIVE

A handheld device using near-infrared technology(Infrascanner) has shown good accuracy for detection of traumatic intracranial haemorrhages in adults. This study aims to determine the feasibility of use of Infrascanner in children with minor head injury (MHI) in the Emergency Department(ED). Secondary aim was to assess its potential usefulness to reduce CT scan rate.

METHODS

Prospective pilot study conducted in two paediatric EDs, including children at high or intermediate risk for clinically important traumatic brain injury (ciTBI) according to the adapted PECARN rule in use. Completion of Infrascanner measurements and time to completion were recorded. Decision on CT scan and CT scan reporting were performed independently and blinded to Infrascanner results.

RESULTS

Completion of the Infrascanner measurement was successfully achieved in 103 (94 %) of 110 patients enrolled,after a mean of 4.4±2.9 min. A CT scan was performed in 18(17.5 %) children. Only one had an intracranial haemorrhage that was correctly identified by the Infrascanner. The exploratory analysis showed a specificity of 93 % (95 % CI, 86.5–96.6) and a negative predictive value of 100 % (95 % CI,81.6–100) for ciTBI. The use of Infrascanner would have led to avoid ten CT scan, reducing the CT scan rate by 58.8 %.

CONCLUSIONS

Infrascanner seems an easy-to-use tool for children presenting to the ED following a MHI, given the high completion rate and short time to completion. Our preliminary results suggest that Infrascanner is worthy of further investigation as a potential tool to decrease the CT scan rate in children with MHI.

The use of handheld near-infrared device (Infrascanner) for detecting intracranial haemorrhages in children with minor head injury

OBJECTIVE

A handheld device using near-infrared technology (Infrascanner) has shown good accuracy for detection of traumatic intracranial haemorrhages in adults. This study aims to determine the feasibility of use of Infrascanner in children with minor head injury (MHI) in the Emergency Department (ED). Secondary aim was to assess its potential usefulness to reduce CT scan rate.

METHODS

Prospective pilot study conducted in two paediatric EDs, including children at high or intermediate risk for clinically important traumatic brain injury (ciTBI) according to the adapted PECARN rule in use. Completion of Infrascanner measurements and time to completion were recorded. Decision on CT scan and CT scan reporting were performed independently and blinded to Infrascanner results.

RESULTS

Completion of the Infrascanner measurement was successfully achieved in 103 (94 %) of 110 patients enrolled, after a mean of 4.4 ± 2.9 min. A CT scan was performed in 18 (17.5 %) children. Only one had an intracranial haemorrhage that was correctly identified by the Infrascanner. The exploratory analysis showed a specificity of 93 % (95 % CI, 86.5-96.6) and a negative predictive value of 100 % (95 % CI, 81.6-100) for ciTBI. The use of Infrascanner would have led to avoid ten CT scan, reducing the CT scan rate by 58.8 %.

CONCLUSIONS

Infrascanner seems an easy-to-use tool for children presenting to the ED following a MHI, given the high completion rate and short time to completion. Our preliminary results suggest that Infrascanner is worthy of further investigation as a potential tool to decrease the CT scan rate in children with MHI.

Wireless near-infrared spectroscopy system for determining brain hemoglobin levels in laboratory animals

Traumatic brain injury (TBI) is usually caused by brain shaking or impact. It can affect normal brain function and may even lead to disability or death. However, there are very few studies on the associated physiologic changes in humans or animals. In this study, a non-invasive, wireless multi-channel near-infrared spectroscopy (NIRS) was developed to continuously monitor the concentration change of oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), and total hemoglobin (HbT) to elucidate changes in the physiological state of the brain during and after different strength impaction. The triphenyltetrazolium chloride (TTC) staining was also used to monitor changes of infarction volume after different strength impaction. The results indicated that the concentration changes of HbO2 and HbT, and the changes of infarction volumes were significantly related to the impact strength. In conclusion, the status of TBI can be clinically evaluated by detecting HbO2 and HbT changes. The system proposed here is stable, accurate, non-invasive, and mostly important wireless which can easily be used for TBI study.

Progressive epidural hematoma in patients with head trauma: incidence, outcome, and risk factors

Progressive epidural hematoma (PEDH) after head injury is often observed on serial computerized tomography (CT) scans. Recent advances in imaging modalities and treatment might affect its incidence and outcome. In this study, PEDH was observed in 9.2% of 412 head trauma patients in whom two CT scans were obtained within 24 hours of injury, and in a majority of cases, it developed within 3 days after injury. In multivariate logistic regression, patient gender, age, Glasgow Coma Scale (GCS) score at admission, and skull fracture were not associated with PEDH, whereas hypotension (odds ratio (OR) 0.38, 95% confidence interval (CI) 0.17-0.84), time interval of the first CT scanning (OR 0.42, 95% CI 0.19-0.83), coagulopathy (OR 0.36, 95% CI 0.15-0.85), or decompressive craniectomy (DC) (OR 0.46, 95% CI 0.21-0.97) was independently associated with an increased risk of PEDH. The 3-month postinjury outcome was similar in patients with PEDH and patients without PEDH (χ(2) = 0.07, P = 0.86). In conclusion, epidural hematoma has a greater tendency to progress early after injury, often in dramatic and rapid fashion. Recognition of this important treatable cause of secondary brain injury and the associated risk factors may help identify the group at risk and tailor management of patients with TBI.

Near-Infrared Laser Spectroscopy as a Screening Tool for Detecting Hematoma in Patients with Head Trauma

Introduction:

Among imaging techniques, computed tomography (CT) is a reliable method for detecting intracranial hematomas in patients with head trauma, but it is not generally available in special circumstances like prehospital situations and harsh conditions such as those following an earthquake.

Objective:

The objective of this study is to determine if near-infrared spectroscopy (NIRS) is useful for performing CT scans on patients with closed head trauma that present to medical centers that do not have the ability to perform a CT scan or in prehospital or harsh situations. Near-infrared spectroscopy and CT scan were compared according to sensitivity and specificity.

Methods:

This was an observational, prospective study. One hundred forty-eight patients admitted to Rasool Akram General Hospital in Tehran, Iran with head injuries during a one-month period were studied using NIRS and CT. The observational, prospective study was conducted and sensitivity, specificity, positive and negative predictive values of NIRS were calculated. Chi-square and Kappa analysis was performed, and a p-value <0.05 was considered significant.

Results:

According to the CT scan findings, 54 (36.5%) of the patients developed intracranial hematoma. The NIRS examination showed that 69 patients (46.6%) might have intracranial hematoma. The number of true negatives was 73 and the number of false negatives was six patients. The sensitivity and specificity of NIRS examination was 88.9% and 77.7%, respectively.

Conclusions:

This study speculates that NIRS may be a useful screening tool to detect intracranial hematoma. This capability could be useful in special situations like in a deprived area, medical centers without CT scan capabilities, prehospital situations, and in harsh conditions like those after an earthquake or other disasters that causes increased numbers of victims with closed head trauma.

The utility of near infrared spectroscopy in detecting intracranial hemorrhage in children

A prospective case-control study was conducted in a tertiary care pediatric intensive care unit (PICU) to evaluate the use of near infrared spectroscopy (NIRS) for the detection of intracranial hemorrhage (ICH) in children. Subjects 0-14 years of age who had a computed tomography (CT) scan of the head performed as part of clinical care were eligible for enrollment. The children were stratified into two groups based on whether the CT was normal or abnormal. Children in the abnormal imaging cohort were further divided into those with ICH and those with other abnormalities of the brain parenchyma (contusions, diffuse axonal injury [DAI], or cerebral edema) or fractures. NIRS measurements were performed on all subjects within 24 h of head CT. The NIRS operator was blinded to the presence or absence of ICH. NIRS measurements were performed in eight different scalp locations (four bilaterally). A total of 103 measurements were made. The optical density (OD) was automatically calculated by comparing the reflected and diffused optical signal. A ΔOD>0.2 between hemispheres in any scalp location was considered abnormal. NIRS was performed in a total of 28 subjects: 7 had normal imaging and 21 had abnormal imaging. Of those with abnormal imaging, 12 had ICH. The sensitivity and specificity of NIRS at detecting ICH was 1.0 and 0.8, respectively. The positive and negative predictive values were 0.8 and 1.0, respectively. In conclusion, NIRS correctly identified all cases of ICH in this pilot study. Our preliminary results suggest that NIRS may be beneficial in the evaluation of a child with possible ICH.

Non-invasive optical imaging of stroke

The acute onset of a neurological deficit is the key clinical feature of stroke. In most cases, however, pathophysiological changes in the cerebral vasculature precede the event, often by many years. Persisting neurological deficits may also require long-term rehabilitation. Hence, stroke may be considered a chronic disease, and diagnostic and therapeutic efforts must include identification of specific risk factors, and the monitoring of and interventions in the acute and subacute stages, and should aim at a pathophysiologically based approach to optimize the rehabilitative effort. Non-invasive optical techniques have been experimentally used in all three stages of the disease and may complement the established diagnostic and monitoring tools. Here, we provide an overview of studies using the methodology in the context of stroke, and we sketch perspectives of how they may be integrated into the assessment of the highly dynamic pathophysiological processes during the acute and subacute stages of the disease and also during rehabilitation and (secondary) prevention of stroke.

Diffuse Optics for Tissue Monitoring and Tomography

This review describes the diffusion model for light transport in tissues and the medical applications of diffuse light. Diffuse optics is particularly useful for measurement of tissue hemodynamics, wherein quantitative assessment of oxy- and deoxy-hemoglobin concentrations and blood flow are desired. The theoretical basis for near-infrared or diffuse optical spectroscopy (NIRS or DOS, respectively) is developed, and the basic elements of diffuse optical tomography (DOT) are outlined. We also discuss diffuse correlation spectroscopy (DCS), a technique whereby temporal correlation functions of diffusing light are transported through tissue and are used to measure blood flow. Essential instrumentation is described, and representative brain and breast functional imaging and monitoring results illustrate the workings of these new tissue diagnostics.

Application of spectral derivative data in visible and near-infrared spectroscopy

The use of the spectral derivative method in visible and near-infrared optical spectroscopy is presented, whereby instead of using discrete measurements around several wavelengths, the difference between nearest neighbouring spectral measurements is utilized. The proposed technique is shown to be insensitive to the unknown tissue and fibre contact coupling coefficients providing substantially increased accuracy as compared to more conventional techniques. The self-calibrating nature of the spectral derivative techniques increases its robustness for both clinical and industrial applications, as is demonstrated based on simulated results as well as experimental data.

Early detection of life-threatening intracranial haemorrhage using a portable near-infrared spectroscopy device

OBJECTIVE

To determine whether infrared spectroscopy allows early recognition of epidural and subdural haematomas among trauma patients.

METHODS

Injured people admitted to two trauma units were enrolled in a prospective multicentre observational study, and infrared spectroscopy was performed before computed tomography of the head as a part of their initial evaluation. Subsequent CT findings suggestive of epidural or subdural haematoma served as controls.

RESULTS

Over 12 months, 110 patients were enrolled; 64 (58.1%) were men and 46 (41.9%) were women. Mean age was 56.2 years, and mean Glasgow Coma Scale on admission was 12.6. Infrared spectroscopy was 90.5% sensitive and 95.5% specific for epidural and subdural haematoma. Positive and negative predictive values were 82.6% and 97.7%, respectively.

CONCLUSIONS

Infrared spectroscopy allows early recognition of epidural and subdural haematomas in trauma cases. Further studies are needed to evaluate whether immediate confirmation or exclusion of epidural and subdural haematomas with portable near-infrared spectroscopy devices improves the decision-making process in the treatment of severely injured people.

Neuromonitoring in the intensive care unit. II. Cerebral oxygenation monitoring and microdialysis

BACKGROUND

Monitoring the injured brain is an integral part of the management of severely brain injured patients in intensive care. There is increasing interest in methods to monitor global and regional cerebral oxygenation. There have been significant advances in analysing tissue oxygenation and local metabolites in the injured brain over the past decade.

DISCUSSION

Cerebral oxygenation can be assessed on a global or regional basis by jugular venous oximetry and near infra-red spectroscopy respectively. Techniques of brain tissue oxygenation monitoring and microdialysis are also covered in this review.

CONCLUSIONS

Various modalities are available to monitor oxygenation and the local milieu in the injured brain in the intensive care unit. Use of these modalities helps to optimise brain oxygen delivery and metabolism in patients with acute brain injury.

Monitoring cerebral oxygenation in traumatic brain injury

Ischemia is a common problem after traumatic brain injury (TBI) that eludes detection with standard monitoring. In this review we will discuss four available techniques (SjVO2, PET, NIRS and PbrO2) to monitor cerebral oxygenation. We present technical data including strengths and weaknesses of these systems, information from clinical studies and formulate a vision for the future.

The Accuracy of Near-Infrared Spectroscopy in Detection of Subdural and Epidural Hematomas

BACKGROUND

We evaluated the safety range of near-infrared spectroscopy (NIRS) in the management of trauma patients who had subdural or epidural hematomas in the emergency room and intensive care unit.

METHODS

Thirty cases with the radiologic diagnosis of subdural and epidural hematomas were evaluated pre- and postoperatively by NIRS. The findings were analyzed by comparing the data of 30 minor head trauma patients without hematoma, which was proven by computed tomography imaging using Mann-Whitney U and McNemar tests.

RESULTS

The preoperative accuracy of NIRS in detecting the hematoma existence was same as the accuracy of the radiologic imaging but the postoperative findings were not reliable. The sensitivity of the device in detecting abnormality was found to be 0.87.

CONCLUSION

NIRS is a good device to predict intracranial subdural and epidural hematomas in the field and emergency units. However, it is not superior to computed tomography or magnetic resonance imaging. It is useful in emergency situations to diagnose an intracranial bleeding but NIRS is not reliable to detect either postoperative hematomas or intracranial status in patients with craniotomy.

Impaired Muscle Oxygen Metabolism in Uremic Children: Improved After Renal Transplantation

BACKGROUND

The purpose of this study is to clarify skeletal muscle oxidative metabolism in children with end-stage renal disease (ESRD) before and after renal transplantation.

METHODS

We examined muscle oxygenation and metabolism by using noninvasive near-infrared spectroscopy in 10 patients (age, 12.4 +/- 3.1 years) 1 week before and 4 weeks after renal transplantation and in 10 controls (age, 12.8 +/- 2.6 years) during submaximal hand-grip exercise using the flexor digitorum superficialis muscle. We used 2 indicators to evaluate muscle metabolism. The rate of initial decrease in hemoglobin/myoglobin deoxygenation during arterial occlusion after exercise relative to the value at rest (S2/S1) was used as an indicator of mitochondrial oxygen consumption, whereas recovery time (TR) after exercise was used as an indicator of oxygen delivery to the muscle and aerobic capacity.

RESULTS

S2/S1 and TR after exercise were significantly lower in patients before renal transplantation compared with the control group (P < 0.05). S2/S1 and TR after exercise improved significantly after renal transplantation (P < 0.01, P < 0.05) and were not significantly different from those of controls.

CONCLUSION

Oxidative metabolism in skeletal muscle during exercise is impaired in children with ESRD and recovers after renal transplantation.