Noninvasive screening for intracranial hypertension in children with acute, severe traumatic brain injury

Neuromonitoring in the ICU: noninvasive and invasive modalities for critically ill children and neonates

PURPOSE OF REVIEW

Critically ill children are at risk of neurologic dysfunction and acquiring primary and secondary brain injury. Close monitoring of cerebral function is crucial to prevent, detect, and treat these complications.

RECENT FINDINGS

A variety of neuromonitoring modalities are currently used in pediatric and neonatal ICUs. These include noninvasive modalities, such as electroencephalography, transcranial Doppler, and near-infrared spectroscopy, as well as invasive methods including intracranial pressure monitoring, brain tissue oxygen measurement, and cerebral microdialysis. Each modality offers unique insights into neurologic function, cerebral circulation, or metabolism to support individualized neurologic care based on a patient's own physiology. Utilization of these modalities in ICUs results in reduced neurologic injury and mortality and improved neurodevelopmental outcomes.

SUMMARY

Monitoring of neurologic function can significantly improve care of critically ill children. Additional research is needed to establish normative values in pediatric patients and to standardize the use of these modalities.

Noninvasive Intracranial Pressure Monitoring: Are We There Yet?

There is an urgent unmet need for a reliable noninvasive tool to detect elevations in intracranial pressure (ICP) above guideline-recommended thresholds for treatment. Gold standard invasive ICP monitoring is unavailable in many settings, including resource-limited environments, and in situations such as liver failure in which coagulopathy increases the risk of invasive monitoring. Although a large number of noninvasive techniques have been evaluated, this article reviews the potential clinical role, if any, of the techniques that have undergone the most extensive evaluation and are already in clinical use. Elevations in ICP transmitted through the subarachnoid space result in distension of the optic nerve sheath. The optic nerve sheath diameter (ONSD) can be measured with ultrasound, and an ONSD threshold can be used to detect elevated ICP. Although many studies suggest this technique accurately detects elevated ICP, there is concern for risk of bias and variations in ONSD thresholds across studies that preclude routine use of this technique in clinical practice. Multiple transcranial Doppler techniques have been used to assess ICP, but the best studied are the pulsatility index and the Czosnyka method to estimate cerebral perfusion pressure and ICP. Although there is inconsistency in the literature, recent prospective studies, including an international multicenter study, suggest the estimated ICP technique has a high negative predictive value (> 95%) but a poor positive predictive value (≤ 30%). Quantitative pupillometry is a sensitive and objective method to assess pupillary size and reactivity. Proprietary indices have been developed to quantify the pupillary light response. Limited data suggest these quantitative measurements may be useful for the early detection of ICP elevation. No current noninvasive technology can replace invasive ICP monitoring. Where ICP monitoring is unavailable, multimodal noninvasive assessment may be useful. Further innovation and research are required to develop a reliable, continuous technique of noninvasive ICP assessment.

Update in Pediatric Neurocritical Care: What a Neurologist Caring for Critically Ill Children Needs to Know

Currently nearly one-quarter of admissions to pediatric intensive care units (PICUs) worldwide are for neurocritical care diagnoses that are associated with significant morbidity and mortality. Pediatric neurocritical care is a rapidly evolving field with unique challenges due to not only age-related responses to primary neurologic insults and their treatments but also the rarity of pediatric neurocritical care conditions at any given institution. The structure of pediatric neurocritical care services therefore is most commonly a collaborative model where critical care medicine physicians coordinate care and are supported by a multidisciplinary team of pediatric subspecialists, including neurologists. While pediatric neurocritical care lies at the intersection between critical care and the neurosciences, this narrative review focuses on the most common clinical scenarios encountered by pediatric neurologists as consultants in the PICU and synthesizes the recent evidence, best practices, and ongoing research in these cases. We provide an in-depth review of (1) the evaluation and management of abnormal movements (seizures/status epilepticus and status dystonicus); (2) acute weakness and paralysis (focusing on pediatric stroke and select pediatric neuroimmune conditions); (3) neuromonitoring modalities using a pathophysiology-driven approach; (4) neuroprotective strategies for which there is evidence (e.g., pediatric severe traumatic brain injury, post-cardiac arrest care, and ischemic stroke and hemorrhagic stroke); and (5) best practices for neuroprognostication in pediatric traumatic brain injury, cardiac arrest, and disorders of consciousness, with highlights of the 2023 updates on Brain Death/Death by Neurological Criteria. Our review of the current state of pediatric neurocritical care from the viewpoint of what a pediatric neurologist in the PICU needs to know is intended to improve knowledge for providers at the bedside with the goal of better patient care and outcomes.

Intracranial Pressure and Cerebral Hemodynamics in Infants Before and After Glenn Procedure

OBJECTIVES

This prospective cohort study aimed to investigate changes in intracranial pressure (ICP) and cerebral hemodynamics in infants with congenital heart disease undergoing the Glenn procedure, focusing on the relationship between superior vena cava pressure and estimated ICP.

DESIGN

A single-center prospective cohort study.

SETTING

The study was conducted in a cardiac center over 4 years (2019-2022).

PATIENTS

Twenty-seven infants with congenital heart disease scheduled for the Glenn procedure were included in the study, and detailed patient demographics and primary diagnoses were recorded.

INTERVENTIONS

Transcranial Doppler (TCD) ultrasound examinations were performed at three time points: baseline (preoperatively), postoperative while ventilated (within 24-48 hr), and at discharge. TCD parameters, blood pressure, and pulmonary artery pressure were measured.

MEASUREMENTS AND MAIN RESULTS

TCD parameters included systolic flow velocity, diastolic flow velocity (dFV), mean flow velocity (mFV), pulsatility index (PI), and resistance index. Estimated ICP and cerebral perfusion pressure (CPP) were calculated using established formulas. There was a significant postoperative increase in estimated ICP from 11 mm Hg (interquartile range [IQR], 10-16 mm Hg) to 15 mm Hg (IQR, 12-21 mm Hg) postoperatively (p = 0.002) with a trend toward higher CPP from 22 mm Hg (IQR, 14-30 mm Hg) to 28 mm Hg (IQR, 22-38 mm Hg) postoperatively (p = 0.1). TCD indices reflected alterations in cerebral hemodynamics, including decreased dFV and mFV and increased PI. Intracranial hemodynamics while on positive airway pressure and after extubation were similar.

CONCLUSIONS

Glenn procedure substantially increases estimated ICP while showing a trend toward higher CPP. These findings underscore the intricate interaction between venous pressure and cerebral hemodynamics in infants undergoing the Glenn procedure. They also highlight the remarkable complexity of cerebrovascular autoregulation in maintaining stable brain perfusion under these circumstances.

Neuromonitoring in Children with Traumatic Brain Injury

Traumatic brain injury remains a major cause of mortality and morbidity in children across the world. Current management based on international guidelines focuses on a fixed therapeutic target of less than 20 mm Hg for managing intracranial pressure and 40-50 mm Hg for cerebral perfusion pressure across the pediatric age group. To improve outcome from this complex disease, it is essential to understand the pathophysiological mechanisms responsible for disease evolution by using different monitoring tools. In this narrative review, we discuss the neuromonitoring tools available for use to help guide management of severe traumatic brain injury in children and some of the techniques that can in future help with individualizing treatment targets based on advanced cerebral physiology monitoring.

Neuromonitoring after Pediatric Cardiac Arrest: Cerebral Physiology and Injury Stratification

BACKGROUND

Significant long-term neurologic disability occurs in survivors of pediatric cardiac arrest, primarily due to hypoxic-ischemic brain injury. Postresuscitation care focuses on preventing secondary injury and the pathophysiologic cascade that leads to neuronal cell death. These injury processes include reperfusion injury, perturbations in cerebral blood flow, disturbed oxygen metabolism, impaired autoregulation, cerebral edema, and hyperthermia. Postresuscitation care also focuses on early injury stratification to allow clinicians to identify patients who could benefit from neuroprotective interventions in clinical trials and enable targeted therapeutics.

METHODS

In this review, we provide an overview of postcardiac arrest pathophysiology, explore the role of neuromonitoring in understanding postcardiac arrest cerebral physiology, and summarize the evidence supporting the use of neuromonitoring devices to guide pediatric postcardiac arrest care. We provide an in-depth review of the neuromonitoring modalities that measure cerebral perfusion, oxygenation, and function, as well as neuroimaging, serum biomarkers, and the implications of targeted temperature management.

RESULTS

For each modality, we provide an in-depth review of its impact on treatment, its ability to stratify hypoxic-ischemic brain injury severity, and its role in neuroprognostication.

CONCLUSION

Potential therapeutic targets and future directions are discussed, with the hope that multimodality monitoring can shift postarrest care from a one-size-fits-all model to an individualized model that uses cerebrovascular physiology to reduce secondary brain injury, increase accuracy of neuroprognostication, and improve outcomes.

Variability of the optic nerve sheath diameter on brain computed tomography in Turkish children based on sex and age

BACKGROUND

Optic nerve sheath diameter (ONSD) measurement is a noninvasive method that can be used for intracranial pressure monitoring. Several studies have investigated normal ONSD values in children, but no general consensus has been reached yet.

OBJECTIVES

The aim of our study was to reveal normal ONSD, eyeball transverse diameter (ETD), and ONSD/ETD values on brain computed tomography (CT) in healthy children aged 1 month to 18 years.

METHODS

Children admitted to the emergency department with minor head trauma and had normal brain CT were included in the study. The demographic characteristics of the patients (age and sex) were recorded, and the patients were divided into four age groups: 1 month to 2 years, 2 to 4 years, 4 to 10 years, and 10 to 18 years.

RESULTS

The images of 332 patients were analyzed. When the median values of all measurement parameters (right and left ONSD, ETD, and ONSD/ETD) were compared between the right and left eyes, no statistically significant differences were found. When the same parameters were compared according to age group, the ONSD and ETD values differed significantly (values of males were found to be higher), but the ONSD proximal/ETD and ONSD middle/ETD values did not differ significantly.

CONCLUSION

In our study, normal ONSD, ETD, and ONSD/ETD values were determined according to age and sex in healthy children. As the ONSD/ETD index did not statistically significantly differ according to age and sex, diagnostic studies for traumatic brain injuries can be performed using the index.

Hyper-acute effects of sub-concussive soccer headers on brain function and hemodynamics

Introduction

Sub-concussive head impacts in soccer are drawing increasing research attention regarding their acute and long-term effects as players may experience thousands of headers in a single season. During these impacts, the head experiences rapid acceleration similar to what occurs during a concussion, but without the clinical implications. The physical mechanism and response to repetitive impacts are not completely understood. The objective of this work was to examine the immediate functional outcomes of sub-concussive level impacts from soccer heading in a natural, non-laboratory environment.

Methods

Twenty university level soccer athletes were instrumented with sensor-mounted bite bars to record impacts from 10 consecutive soccer headers. Pre- and post-header measurements were collected to determine hyper-acute changes, i.e., within minutes after exposure. This included measuring blood flow velocity using transcranial Doppler (TCD) ultrasound, oxyhemoglobin concentration using functional near infrared spectroscopy imaging (fNIRS), and upper extremity dual-task (UEF) neurocognitive testing.

Results

On average, the athletes experienced 30.7 ± 8.9 g peak linear acceleration and 7.2 ± 3.1 rad/s peak angular velocity, respectively. Results from fNIRS measurements showed an increase in the brain oxygenation for the left prefrontal cortex (PC) (p = 0.002), and the left motor cortex (MC) (p = 0.007) following the soccer headers. Additional analysis of the fNIRS time series demonstrates increased sample entropy of the signal after the headers in the right PC (p = 0.02), right MC (p = 0.004), and left MC (p = 0.04).

Discussion

These combined results reveal some variations in brain oxygenation immediately detected after repetitive headers. Significant changes in balance and neurocognitive function were not observed in this study, indicating a mild level of head impacts. This is the first study to observe hemodynamic changes immediately after sub-concussive impacts using non-invasive portable imaging technology. In combination with head kinematic measurements, this information can give new insights and a framework for immediate monitoring of sub-concussive impacts on the head.

Transcranial Color-Coded Sonography With Angle Correction As a Screening Tool for Raised Intracranial Pressure

OBJECTIVES

Transcranial Doppler (TCD) has been evaluated as a noninvasive intracranial pressure (ICP) assessment tool. Correction for insonation angle, a potential source of error, with transcranial color-coded sonography (TCCS) has not previously been reported while evaluating ICP with TCD. Our objective was to study the accuracy of TCCS for detection of ICP elevation, with and without the use of angle correction.

DESIGN

Prospective study of diagnostic accuracy.

SETTING

Academic neurocritical care unit.

PATIENTS

Consecutive adults with invasive ICP monitors.

INTERVENTIONS

Ultrasound assessment with TCCS.

MEASUREMENTS AND MAIN RESULTS

End-diastolic velocity (EDV), time-averaged peak velocity (TAPV), and pulsatility index (PI) were measured in the bilateral middle cerebral arteries with and without angle correction. Concomitant mean arterial pressure (MAP) and ICP were recorded. Estimated cerebral perfusion pressure (CPP) was calculated as estimated CPP (CPPe) = MAP × (EDV/TAPV) + 14, and estimated ICP (ICPe) = MAP-CPPe. Sixty patients were enrolled and 55 underwent TCCS. Receiver operating characteristic curve analysis of ICPe for detection of invasive ICP greater than 22 mm Hg revealed area under the curve (AUC) 0.51 (0.37-0.64) without angle correction and 0.73 (0.58-0.84) with angle correction. The optimal threshold without angle correction was ICPe greater than 18 mm Hg with sensitivity 71% (29-96%) and specificity 28% (16-43%). With angle correction, the optimal threshold was ICPe greater than 21 mm Hg with sensitivity 100% (54-100%) and specificity 30% (17-46%). The AUC for PI was 0.61 (0.47-0.74) without angle correction and 0.70 (0.55-0.92) with angle correction.

CONCLUSIONS

Angle correction improved the accuracy of TCCS for detection of elevated ICP. Sensitivity was high, as appropriate for a screening tool, but specificity remained low.

[Clinical value of bedside transcranial doppler ultrasound in assessing intracranial pressure in critically ill pediatric patients with nervous system disease]

OBJECTIVES

To study the value of bedside transcranial doppler (TCD) in evaluating the level of intracranial pressure (ICP) in critically ill pediatric patients with nervous system disease in the pediatric intensive care unit (PICU).

METHODS

A prospective analysis was performed on the critically ill pediatric patients with nervous system disease who were admitted to the PICU of Shengjing Hospital, China Medical University, from November 2020 to November 2021. Bedside TCD was performed on all patients, and pulsatility index (PI) was calculated. Bedside lumbar puncture was performed to measure ICP. A Pearson correlation analysis was used to assess the correlation between PI and ICP. The receiver operating characteristic (ROC) curve was used to assess the value of PI in the diagnosis of elevated ICP (≥20 mm Hg).

RESULTS

A total of 56 children were included in the study. The top three primary diseases were intracranial infection (24 children, 43%), traumatic brain injury (TBI) (11 children, 20%), and cerebrovascular disease (5 children, 9%). The Pearson correlation analysis showed that PI was positively correlated with ICP (r=0.536, P<0.001). The subgroup analysis based on primary disease showed that in the TBI group, PI was positively correlated with ICP (r=0.655, P=0.029), while no significant correlation between PI and ICP was observed in the intracranial infection group (r=0.324, P=0.122). The ROC curve analysis showed that PI had an area under the curve of 0.828 (95%CI: 0.677-0.979) in predicting ICP≥20 mm Hg, with a sensitivity of 83.3% and a specificity of 79.5% at the optimal cut-off value of 1.255.

CONCLUSIONS

TCD technology for ICP monitoring can predict the change in ICP in critically ill pediatric patients with nervous system disease, suggesting it is useful for treatment options and prognosis evaluation.

Intracranial Pressure and Cerebral Hemodynamic Monitoring After Cardiac Arrest in Pediatric Pigs Using Contrast Ultrasound-Derived Parameters

OBJECTIVES

We explore the correlation of contrast-enhanced ultrasound (CEUS) parameters to intracranial pressure (ICP) in a porcine experimental model of pediatric cardiac arrest.

METHODS

Eleven pediatric pigs underwent electrically induced cardiac arrest followed by cardiopulmonary resuscitation. ICP was measured using intracranial bolt monitor and CEUS was monitored through a cranial window. Various CEUS parameters were monitored at baseline, immediately post return of spontaneous circulation (ROSC), 1 hour-post ROSC, and 3 hours post-ROSC.

RESULTS

There was significant ICP correlation with wash-out slope assessed by CEUS time intensity curve analysis at immediate post-ROSC. At 3 hours post-ROSC there was also significant negative correlation between ICP and peak enhancement which may be due to the evolution of anoxic injury.

CONCLUSION

The use of CEUS in assessing disruption of cerebral hemodynamics and ICP post cardiac arrest will need future validation and comparison to other imaging modalities. The correlation between CEUS parameters and ICP may be due to the alterations in cerebral autoregulation that result from anoxic brain injury.

ASNM and ASN joint guidelines for transcranial Doppler ultrasonic monitoring: An update

Today, it seems prudent to reconsider how ultrasound technology can be used for providing intraoperative neurophysiologic monitoring that will result in better patient outcomes and decreased length and cost of hospitalization. An extensive and rapidly growing literature suggests that the essential hemodynamic information provided by transcranial Doppler (TCD) ultrasonography neuromonitoring (TCDNM) would provide effective monitoring modality for improving outcomes after different types of vascular, neurosurgical, orthopedic, cardiovascular, and cardiothoracic surgeries and some endovascular interventional or diagnostic procedures, like cardiac catheterization or cerebral angiography. Understanding, avoiding, and preventing peri- or postoperative complications, including neurological deficits following abovementioned surgeries, endovascular intervention, or diagnostic procedures, represents an area of great public and economic benefit for society, especially considering the aging population. The American Society of Neurophysiologic Monitoring and American Society of Neuroimaging Guidelines Committees formed a joint task force and developed updated guidelines to assist in the use of TCDNM in the surgical and intensive care settings. Specifically, these guidelines define (1) the objectives of TCD monitoring; (2) the responsibilities and behaviors of the neurosonographer during monitoring; (3) instrumentation and acquisition parameters; (4) safety considerations; (5) contemporary rationale for TCDNM; (6) TCDNM perspectives; and (7) major recommendations.

Transcranial Doppler Ultrasound, a Review for the Pediatric Intensivist

The use of transcranial Doppler ultrasound (TCD) is increasing in frequency in the pediatric intensive care unit. This review highlights some of the pertinent TCD applications for the pediatric intensivist, including evaluation of cerebral hemodynamics, autoregulation, non-invasive cerebral perfusion pressure/intracranial pressure estimation, vasospasm screening, and cerebral emboli detection.

Multimodal Neurologic Monitoring in Children With Acute Brain Injury

Children with acute neurologic illness are at high risk of mortality and long-term neurologic disability. Severe traumatic brain injury, cardiac arrest, stroke, and central nervous system infection are often complicated by cerebral hypoxia, hypoperfusion, and edema, leading to secondary neurologic injury and worse outcome. Owing to the paucity of targeted neuroprotective therapies for these conditions, management emphasizes close physiologic monitoring and supportive care. In this review, we will discuss advanced neurologic monitoring strategies in pediatric acute neurologic illness, emphasizing the physiologic concepts underlying each tool. We will also highlight recent innovations including novel monitoring modalities, and the application of neurologic monitoring in critically ill patients at risk of developing neurologic sequelae.

Evaluation of cerebral hemodynamics by transcranial Doppler ultrasonography and its correlation with intracranial pressure in an animal model of intracranial hypertension

BACKGROUND

Transcranial Doppler has been tested in the evaluation of cerebral hemodynamics as a non-invasive assessment of intracranial pressure (ICP), but there is controversy in the literature about its actual benefit and usefulness in this situation.

OBJECTIVE

To investigate cerebral blood flow assessed by Doppler technique and correlate with the variations of the ICP in the acute phase of intracranial hypertension in an animal model.

METHODS

An experimental animal model of intracranial hypertension was used. The experiment consisted of two groups of animals in which intracranial balloons were implanted and inflated with 4 mL (A) and 7 mL (B) for controlled simulation of different volumes of hematoma. The values of ICP and Doppler parameters (systolic [FVs], diastolic [FVd], and mean [FVm] cerebral blood flow velocities and pulsatility index [PI]) were collected during the entire procedure (before and during hematoma simulations and venous hypertonic saline infusion intervention). Comparisons between Doppler parameters and ICP monitoring were performed.

RESULTS

Twenty pigs were studied, 10 in group A and 10 in group B. A significant correlation between PI and ICP was obtained, especially shortly after abrupt elevation of ICP. There was no correlation between ICP and FVs, FVd or FVm separately. There was also no significant change in ICP after intravenous infusion of hypertonic saline solution.

CONCLUSIONS

These results demonstrate the potential of PI as a parameter for the evaluation of patients with suspected ICP elevation.

Practice Recommendations for Transcranial Doppler Ultrasonography in Critically Ill Children in the Pediatric Intensive Care Unit: A Multidisciplinary Expert Consensus Statement

Transcranial Doppler ultrasonography (TCD) is being used in many pediatric intensive care units (PICUs) to aid in the diagnosis and monitoring of children with known or suspected pathophysiological changes to cerebral hemodynamics. Standardized approaches to scanning protocols, interpretation, and documentation of TCD examinations in this setting are lacking. A panel of multidisciplinary clinicians with expertise in the use of TCD in the PICU undertook a three-round modified Delphi process to reach unanimous agreement on 34 statements and then create practice recommendations for TCD use in the PICU. Use of these recommendations will help to ensure that high quality TCD images are captured, interpreted, and reported using standard nomenclature. Furthermore, use will aid in ensuring reproducible and meaningful study results between TCD practitioners and across PICUs.

Optic nerve sheath diameter does not correlate with intracranial pressure in pediatric neurocritical care patients

PURPOSE

Intracranial pressure (ICP) > 20 mmHg is associated with worse outcomes in children. The gold standard for monitoring ICP is invasive, has complications such as bleeding and infection, and may not be available in resource limited areas. Ultrasound of the optic nerve sheath diameter (ONSD) has been studied as a noninvasive way to evaluate for elevated ICP in adults. Its utility in pediatrics remains unclear.

METHODS

A prospective study was performed in a pediatric intensive care unit in children ≤ 18 years old. ONSD ultrasound was performed using a 13-6 MHz linear probe with the patient's invasively measured ICP simultaneously recorded. Linear mixed effects models were used to evaluate the association between ONSD and ICP.

RESULTS

One hundred thirty-six measurements were obtained from 16 patients. ONSD was not significantly associated with ICP (p = 0.51). A ROC curve assessing ONSD to determine elevated ICP > 20 mmHg had an area under the curve of 0.52 (95%CI = 0.32-0.72). There was no difference in measurements obtained between the left and right ONSD at the same time (p = 0.82).

CONCLUSIONS

In conclusion, this study demonstrated no association between ONSD measurement and invasively monitored ICP in critically ill children.

Correlation Between Invasive and Noninvasive Technique of Intracranial Pressure Measurement in Children With Traumatic Brain Injury: An Observational Study

BACKGROUND

Direct measurement of intracranial pressure (ICP) is an invasive technique with potential complications, which has prompted the development of alternative, noninvasive, methods of ICP assessment. The aim of this study was to determine the relationship between noninvasive ultrasound-based measurement of optic nerve sheath diameter (ONSD), transcranial Doppler-derived pulsatility index (PI), and invasive ICP measurements in children with traumatic brain injury (TBI).

METHODS

Children aged 1 to 18 years undergoing invasive ICP monitoring following TBI were included in the study. Noninvasive ONSD and PI measurements were compared with simultaneous invasive ICP.

RESULTS

In all, 406 measurements of ONSD and PI were obtained in 18 patients. ONSD and PI correlated with ICP (r=0.76 and 0.79, respectively), combining ONSD and PI resulted in an even stronger correlation with ICP (r=0.99). Formulas were derived from mixed-effect models that best fitted the data for noninvasive ICP estimation. A combination of ONSD and PI had the highest ability to detect ICP >20 mm Hg (area under the receiver operating characteristic curve=0.99, 95% confidence interval: 0.99-1.00). Optimal cutoff values for the prediction of intracranial hypertension were 5.95 mm for ONSD (sensitivity, 92%; specificity, 76%) and 1.065 for PI (sensitivity, 92%; specificity, 87%).

CONCLUSIONS

In children with TBI, a combination of ONSD and PI strongly correlates with invasive ICP and has potential to screen for intracranial hypertension noninvasively. ONSD and PI may be useful tools for assessing ICP where invasive monitoring is unavailable or contraindicated.

Prehospital Detection of Life-Threatening Intracranial Pathology: An Unmet Need for Severe TBI in Austere, Rural, and Remote Areas

Severe traumatic brain injury (TBI) is a leading cause of death and disability worldwide, especially in low- and middle-income countries, and in austere, rural, and remote settings. The purpose of this Perspective is to challenge the notion that accurate and actionable diagnosis of the most severe brain injuries should be limited to physicians and other highly-trained specialists located at hospitals. Further, we aim to demonstrate that the great opportunity to improve severe TBI care is in the prehospital setting. Here, we discuss potential applications of prehospital diagnostics, including ultrasound and near-infrared spectroscopy (NIRS) for detection of life-threatening subdural and epidural hemorrhage, as well as monitoring of cerebral hemodynamics following severe TBI. Ultrasound-based methods for assessment of cerebrovascular hemodynamics, vasospasm, and intracranial pressure have substantial promise, but have been mainly used in hospital settings; substantial development will be required for prehospital optimization. Compared to ultrasound, NIRS is better suited to assess certain aspects of intracranial pathology and has a smaller form factor. Thus, NIRS is potentially closer to becoming a reliable method for non-invasive intracranial assessment and cerebral monitoring in the prehospital setting. While one current continuous wave NIRS-based device has been FDA-approved for detection of subdural and epidural hemorrhage, NIRS methods using frequency domain technology have greater potential to improve diagnosis and monitoring in the prehospital setting. In addition to better technology, advances in large animal models, provider training, and implementation science represent opportunities to accelerate progress in prehospital care for severe TBI in austere, rural, and remote areas.

Normative and pathological values of hemodynamic and Doppler ultrasound arterial findings in children

Doppler ultrasound is an effective, useful and remarkably powerful tool in pediatric imaging. If possible, its use is always favored to avoid exposure to radiation or sedatives. By waveform spectrum analysis, Doppler ultrasound reveals information on blood flow and details on normal physiology and pathological processes undiscernible from gray-scale imaging alone. However, Doppler ultrasound remains underused, largely due to the difficult interpretation of changes in Doppler waveforms during childhood. This article provides a narrative review of the literature regarding the normative values and the physiological arterial changes through childhood according to age, weight or height, as well as frequent pathological arterial findings in children, classified by arterial territory.

Perioperative near-infrared spectroscopy cerebral oxygen saturation in symptomatic pediatric hydrocephalus patients at risk for intracranial hypertension

OBJECTIVE

The lack of a continuous, noninvasive modality for monitoring intracranial pressure (ICP) is a major obstacle in the care of pediatric patients with hydrocephalus who are at risk for intracranial hypertension. Intracranial hypertension can lead to cerebral ischemia and brain tissue hypoxia. In this study, the authors evaluated the use of near-infrared spectroscopy (NIRS) to measure regional cerebral oxygen saturation (rSO2) in symptomatic pediatric patients with hydrocephalus concerning for elevated ICP.

METHODS

The authors evaluated the NIRS rSO2 trends in pediatric patients presenting with acute hydrocephalus and clinical symptoms of intracranial hypertension. NIRS rSO2 values were recorded hourly before and after neurosurgical intervention. To test for significance between preoperative and postoperative values, the authors constructed a linear regression model with the rSO2 values as the outcome and pre- and postsurgery cohorts as the independent variable, adjusted for age and sex, and used the generalized estimating equation method to account for within-subject correlation.

RESULTS

Twenty-two pediatric patients underwent NIRS rSO2 monitoring before and after CSF diversion surgery. The mean durations of NIRS rSO2 recording pre- and postoperatively were 13.95 and 26.82 hours, respectively. The mean pre- and postoperative rSO2 values were 73.84% and 80.65%, respectively, and the adjusted mean difference estimated from the regression model was 5.98% (adjusted p < 0.0001), suggestive of improved cerebral oxygenation after definitive neurosurgical CSF diversion treatment. Postoperatively, all patients returned to baseline neurological status with no clinical symptoms of elevated ICP.

CONCLUSIONS

Cerebral oxygenation trends measured by NIRS in symptomatic pediatric hydrocephalus patients with intracranial hypertension generally improve after CSF diversion surgery.

Transcranial Doppler Ultrasound During Critical Illness in Children: Survey of Practices in Pediatric Neurocritical Care Centers

OBJECTIVES

The scope of transcranial Doppler ultrasound in the practice of pediatric neurocritical care is unknown. We have surveyed pediatric neurocritical care centers on their use of transcranial Doppler and analyzed clinical management practices.

DESIGN

Electronic-mail recruitment with survey of expert centers using web-based questionnaire.

SETTING

Survey of 43 hospitals (31 United States, 12 international) belonging to the Pediatric Neurocritical Care Research Group.

PATIENTS

None.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A 67% (29/43) hospital-response rate. Of these centers, 27 reported using transcranial Doppler in the PICU; two hospitals opted out due to lack of transcranial Doppler availability/use. The most common diagnoses for using transcranial Doppler in clinical care were intracranial/subarachnoid hemorrhage (20 hospitals), arterial ischemic stroke (14 hospitals), and traumatic brain injury (10 hospitals). Clinical studies were carried out and interpreted by credentialed individuals in 93% (25/27) and 78% (21/27) of the centers, respectively. A written protocol for performance of transcranial Doppler in the PICU was available in 30% (8/27 hospitals); of these, two of eight hospitals routinely performed correlation studies to validate results. In 74% of the centers (20/27), transcranial Doppler results were used to guide clinical care: that is, when to obtain a neuroimaging study (18 hospitals); how to manipulate cerebral perfusion pressure with fluids/vasopressors (13 hospitals); and whether to perform a surgical intervention (six hospitals). Research studies were also commonly performed for a range of diagnoses.

CONCLUSIONS

At least 27 pediatric neurocritical care centers use transcranial Doppler during clinical care. In the majority of centers, studies are performed and interpreted by credentialed personnel, and findings are used to guide clinical management. Further studies are needed to standardize these practices.

Use of a Doppler-Based Pulsatility Index to Evaluate Cerebral Hemodynamics in Neurocritical Patients After Hemicraniectomy

OBJECTIVES

As a noninvasive method for evaluation of cerebral hemodynamics, the correct interpretation of transcranial Doppler or transcranial imaging (TCI) data remains a major challenge. We explored how to interpret the pulsatility index (PI) derived via TCI during evaluations of cerebral hemodynamics in posthemicraniectomy patients.

METHODS

We included patients who underwent invasive arterial pressure and intracranial pressure (ICP) monitoring and simultaneous TCI examinations after hemicraniectomy. We classified the PI of the middle cerebral artery (MCA) into ipsilateral (craniectomy side) and contralateral (opposite side) and analyzed both data sets. The statistical analysis was performed by the Bland-Altman approach, by calculating intraclass correlation coefficients and Spearman correlations, and by drawing receiver operating characteristic curves. Pulsatility index probability charts were created for ICPs exceeding 20, 25, and 30 mm Hg and cerebral perfusion pressures (CPPs) lower than 70, 60, and 50 mm Hg; we thus explored defined ICP and CPP values.

RESULTS

The ipsilateral and contralateral MCA PI data differed. Only the ipsilateral MCA PI showed a weak correlation with ICP (r = 0.378; P < .001). The receiver operating characteristic curve analysis revealed limited diagnostic utility of bilateral MCA PIs for ICP and CPP assessments. An extremely elevated MCA PI indicated that patients were at high risk of a dangerous ICP elevation or CPP reduction. However, MCA PI values within the normal range did not effectively rule out an ICP of 20 mm Hg or higher but effectively eliminated a CPP lower than 50 mm Hg.

CONCLUSIONS

In posthemicraniectomy patients, the Doppler-based MCA PI value was ineffectively for quantitative ICP and CPP evaluations but a useful index for assessment of cerebral hemodynamics in terms of the probability of an ICP elevation or a CPP reduction.

Children With Severe Traumatic Brain Injury, Intracranial Pressure, Cerebral Perfusion Pressure, What Does it Mean? A Review of the Literature

Severe traumatic brain injury is a leading cause of morbidity and mortality in children. In 2003 the Brain Trauma Foundation released guidelines that have since been updated (2010) and have helped standardize and improve care. One area of care that remains controversial is whether the placement of an intracranial pressure monitor is advantageous in the management of traumatic brain injury. Another aspect of care that is widely debated is whether management after traumatic brain injury should be based on intracranial pressure-directed therapy, cerebral perfusion pressure-directed therapy, or a combination of the two. The aim of this article was to provide an overview and review the current evidence regarding these questions.

The Role of Transcranial Doppler in Traumatic Brain Injury: A Systemic Review and Meta-Analysis

To evaluate whether transcranial Doppler (TCD) monitoring plays a role as a prognostic indicator, by being both a diagnostic as well as a monitoring tool for increased intracranial pressure and cerebral vasospasm (VSP), in traumatic brain injury (TBI). Electronic databases and gray literature (unpublished articles) were searched under different MeSH terms from 1990 to the present. Randomized control trials, case–control studies, and prospective cohort studies on TCD in TBI (>18 years old). Clinical outcome measures included Glasgow Coma Outcome Scale (GCOS) and Extended GCOS and mortality. Data were extracted to Review Manager Software. Twenty-five articles that met the inclusion criteria were retrieved and analyzed. Ultimately, five studies were included in our meta-analysis, which revealed that patients with TBI with abnormal TCD (mean flow velocity [MFV] >120 cm/sec or MFV <35 cm/sec and Pulsatility Index >1.2) have a >3-fold higher likelihood of having poor clinical outcome in comparison to patients with TBI and normal TCD monitoring (odds ratio [OR]: 3.87; 95% confidence interval [CI]: 2.97–5.04; P < 0.00001). Subgroup analysis revealed that abnormal TCD has a 9-fold higher likelihood of mortality (OR: 9.96; 95% CI: 4.41–22.47; P < 0.00001). Further, subgroup analysis based on TCD findings revealed that the presence of hypoperfusion on TCD (middle cerebral artery [MCA] <35 cm/s) is associated with a three-fold higher likelihood of having poor functional outcome (OR: 3.72; 95% CI: 1.97–7.0; P < 0.0001). The presence of VSP (MCA >120 cm/s) is associated with three-fold higher likelihood of poor functional outcome (OR: 3.64; 95% CI: 1.55–8.52; P = 0.003). TCD is an evolving diagnostic tool that might play a role in determining the prognosis of patients with TBI. Further prospective study is needed to prove the role of TCD in TBI.

Multimodality Monitoring in Neurocritical Care: Decision-Making Utilizing Direct And Indirect Surrogate Markers

Substantial progress has been made to create innovative technology that can monitor the different physiological characteristics that precede the onset of secondary brain injury, with the ultimate goal of intervening prior to the onset of irreversible neurological damage. One of the goals of neurocritical care is to recognize and preemptively manage secondary neurological injury by analyzing physiologic markers of ischemia and brain injury prior to the development of irreversible damage. This is helpful in a multitude of neurological conditions, whereby secondary neurological injury could present including but not limited to traumatic intracranial hemorrhage and, specifically, subarachnoid hemorrhage, which has the potential of progressing to delayed cerebral ischemia and monitoring postneurosurgical interventions. In this study, we examine the utilization of direct and indirect surrogate physiologic markers of ongoing neurologic injury, including intracranial pressure, cerebral blood flow, and brain metabolism.

Transcranial Doppler in pediatric emergency and intensive care unit: a case series and literature review

PURPOSE

Transcranial Doppler (TCD) has been used for more than 30 years in clinical practice. Although adult intensive care is relatively well covered, pediatric cases are still underrepresented. We intend to review a series of pediatric cases where TCD was determinant in clinical decisions and a literature review on this topic.

METHODS

We describe cases with different pathologies where TCD had an important role in clinical management of the patients. We discuss TCD utility and potential role both in the emergency department and the intensive care unit.

RESULTS

Five patients with different neurologic insults are presented. TCD was useful in the identification of intracranial hypertension in traumatic brain injury, hydrocephalus and central nervous system infection; identification of decreased cerebral perfusion pressure in hypovolemic shock and the diagnosis of impending cerebral circulatory arrest in a child with meningococcal septicemia. We discuss how TCD can be used in emergency and intensive care settings, reviewing relevant literature and our own experience.

CONCLUSIONS

Non-invasive testing using TCD can aid clinical decisions. More widespread use of this technique will allow for better care of children with neurologic insults.

Novel minimally invasive multi-modality monitoring modalities in neurocritical care

Elevated intracranial pressure (ICP) following brain injury contributes to poor outcomes for patients, primarily by reducing the caliber of cerebral vasculature, and thereby reducing cerebral blood flow. Careful monitoring of ICP is critical in these patients in order to determine prognosis, implement treatment when ICP becomes elevated, and to judge responsiveness to treatment. Currently, the gold standard for monitoring is invasive pressure transducers, usually an intraventricular monitor, which presents significant risk of infection and hemorrhage. These risks made discovering non-invasive methods for monitoring ICP and cerebral perfusion a priority for researchers. Herein we sought to review recent publications on novel minimally invasive multi-modality monitoring techniques that provide surrogate data on ICP, cerebral oxygenation, metabolism and blood flow. While limitations in various forms preclude them from supplanting the use of invasive monitors, these modalities represent useful screening tools within our armamentarium that may be invaluable when the risks of invasive monitoring outweigh the associated benefits.

Noninvasive Intracranial Pressure Monitoring for Severe Traumatic Brain Injury in Children: A Concise Update on Current Methods

BACKGROUND

Traumatic brain injury (TBI) is a leading cause of pediatric morbidity and mortality worldwide and intracranial pressure (ICP) monitoring plays a crucial role in its management. Based on existing literature, we review the current practicing noninvasive ICP monitoring devices and their accuracy in predicting increased ICP in pediatric TBI.

METHODS

A thorough literature search was conducted on PubMed, Medline, and the Cochrane database, articles were selected systematically and reviewed completely, and relevant data were summarized and discussed.

RESULTS

A total of 27 articles pertaining to pediatric TBI were included and reviewed. We found various modalities of noninvasive ICP monitoring devices used over the last few years. The noninvasive modalities so far attempted in pediatric TBI and so reviewed here are transcranial Doppler, optic nerve sheath diameter, otoacoustic emission, near-infrared spectroscopy, contrast-enhanced ultrasonography, and quantitative pupillometry.

CONCLUSIONS

Invasive monitoring methods are the current gold standard for monitoring ICP; however, complications caused by their invasive nature are of concern. Of all the noninvasive methods based on the literature, we found transcranial Doppler and optic nerve sheath diameter assessment to be the best tools to monitor ICP in pediatric TBI. The promising results and developments of noninvasive ICP monitoring modalities with its ideal features of high sensitivity, diagnostic accuracy, and simple acquisition technique may make it the future of neurointensive monitoring in pediatric TBI.

Radiological Correlates of Raised Intracranial Pressure in Children: A Review

Radiological assessment of the head is a routine part of the management of traumatic brain injury. This assessment can help to determine the requirement for invasive intracranial pressure (ICP) monitoring. The radiological correlates of elevated ICP have been widely studied in adults but far fewer specific pediatric studies have been conducted. There is, however, growing evidence that there are important differences in the radiological presentations of elevated ICP between children and adults; a reflection of the anatomical and physiological differences, as well as a difference in the pathophysiology of brain injury in children. Here in, we review the radiological parameters that correspond with increased ICP in children that have been described in the literature. We then describe the future directions of this work and our recommendations in order to develop non-invasive and radiological markers of raised ICP in children.

Intracranial Pressure Monitoring-Review and Avenues for Development

Intracranial pressure (ICP) monitoring is a staple of neurocritical care. The most commonly used current methods of monitoring in the acute setting include fluid-based systems, implantable transducers and Doppler ultrasonography. It is well established that management of elevated ICP is critical for clinical outcomes. However, numerous studies show that current methods of ICP monitoring cannot reliably define the limit of the brain's intrinsic compensatory capacity to manage increases in pressure, which would allow for proactive ICP management. Current work in the field hopes to address this gap by harnessing live-streaming ICP pressure-wave data and a multimodal integration with other physiologic measures. Additionally, there is continued development of non-invasive ICP monitoring methods for use in specific clinical scenarios.

Point-of-care ultrasound in pediatric anesthesiology and critical care medicine

Ultrasound has increasingly become a clinical asset in the hands of the anesthesiologist and intensivist who cares for children. Though many applications for ultrasound parallel adult modalities, children as always are not simply small adults and benefit from the application of ultrasound to their management in various ways. Body composition and size are important factors that affect ultrasound performance in the child, as are the pathologies that may uniquely afflict children and aspects of procedures unique to this patient population. Ultrasound simplifies vascular access and other procedures by visualizing structures smaller than those in adults. Maturation of the thoracic cage presents challenges for the clinician performing pulmonary ultrasound though a greater proportion of the thorax can be seen. Moreover, ultrasound may provide unique solutions to sizing the airway and assessing it for cricothyroidotomy. Though cardiac ultrasound and neurosonology have historically been performed by well-developed diagnostic imaging services, emerging literature stresses the utility of clinician ultrasound in screening for pathology and providing serial observations for monitoring clinical status. Use of ultrasound is growing in clinical areas where time and diagnostic accuracy are crucial. Implementation of ultrasound at the bedside will require institutional support of education and credentialing. It is only natural that the pediatric anesthesiologist and intensivist will lead the incorporation of ultrasound in the future practice of these specialties.

Point-of-care transcranial Doppler by intensivists

In the unconscious patient, there is a diagnostic void between the neurologic physical exam, and more invasive, costly and potentially harmful investigations. Transcranial color-coded sonography and two-dimensional transcranial Doppler imaging of the brain have the potential to be a middle ground to bridge this gap for certain diagnoses. With the increasing availability of point-of-care ultrasound devices, coupled with the need for rapid diagnosis of deteriorating neurologic patients, intensivists may be trained to perform point-of-care transcranial Doppler at the bedside. The feasibility and value of this technique in the intensive care unit to help rule-in specific intra-cranial pathologies will form the focus of this article. The proposed scope for point-of-care transcranial Doppler for the intensivist will be put forth and illustrated using four representative cases: presence of midline shift, vasospasm, raised intra-cranial pressure, and progression of cerebral circulatory arrest. We will review the technical details, including methods of image acquisition and interpretation. Common pitfalls and limitations of point-of-care transcranial Doppler will also be reviewed, as they must be understood for accurate diagnoses during interpretation, as well as the drawbacks and inadequacies of the modality in general.

An update on idiopathic intracranial hypertension

BACKGROUND

Idiopathic intracranial hypertension (IIH) is still a grey area in the knowledge of the aetiology, diagnosis and management of neurosurgical diseases. The definition of IIH has been reviewed over time and many hypotheses have been expressed as cause of the disease. The literature supplies very little evidence-based information to guide our decision-making process when it comes to treat the disease. In this review we sum up the latest information regarding the aetiology and therapy of IIH. Additionally, we make an attempt to unify the diagnostic criteria of Dandy, Friedman and Wall established from 1937 to date.

METHOD

In this narrative review, we attempt to update the current standpoint to IIH, evaluate the input until now and consider future directions for research. The vast majority of the literature consisted of cohort studies, case control studies, systematic reviews and other narrative reviews.

RESULTS

Pathophysiology: The incidence of IIH is steadily increasing. Several pathophysiological theories have been proposed in the literature based on the flow of cerebrospinal fluid.

DIAGNOSIS

We attempt to fuse all the three diagnostic approaches published in the literature that detect IIH, while preserving the individual characteristics of each approach.

TREATMENT

Based on evidence-based trials, the current use of acetazolamide in comparison with placebo or with topiramate has been evaluated. In the interventions' field, there seems to be a consonance about the alarming symptoms and what the most suitable operation is in each case. There is some disagreement about the indications for venous sinus transversus stenting and its risk/benefit ratio.

CONCLUSIONS

Until now there is no class I guideline to which our decision-making can be based on for the management of IIH. A lack of systematic reviews and randomised control trials has been noted. If we focused our research on that, we could develop a standardised treatment protocol.

Transcranial Doppler Ultrasound Use in Pediatric Traumatic Brain Injury

Transcranial Doppler ultrasound (TCD) is an inexpensive portable diagnostic tool commonly available within most healthcare systems. A team of trained individuals perform and interpret the test to inform patient care management. The benefit of TCD is well established in adult patients with traumatic brain injury. However, in children with TBI, it is still considered exploratory and its use is not a part of the standard of care. This article describes what TCD is, its use in children, and how TCD measurements apply to children and adolescents in an effort to establish criteria for the use of TCD for children with TBI. The benefit of TCD in pediatric TBI is illustrated by 2 cases of children who participated in a TBI research study. Early indications are that the use of TCD in pediatric cases of TBI may produce unexpected real-time data about the cerebral vasculature and circulation characteristics in children with TBI. Transcranial Doppler ultrasound has the potential for playing an informative diagnostic role in future pediatric TBI management. Ultimately the goal to promote best outcomes after a TBI requires insights into the multi-dynamic nature of the injury and TCD has the ability to support these efforts.

Non-invasive Monitoring of Intracranial Pressure Using Transcranial Doppler Ultrasonography: Is It Possible?

Although intracranial pressure (ICP) is essential to guide management of patients suffering from acute brain diseases, this signal is often neglected outside the neurocritical care environment. This is mainly attributed to the intrinsic risks of the available invasive techniques, which have prevented ICP monitoring in many conditions affecting the intracranial homeostasis, from mild traumatic brain injury to liver encephalopathy. In such scenario, methods for non-invasive monitoring of ICP (nICP) could improve clinical management of these conditions. A review of the literature was performed on PUBMED using the search keywords 'Transcranial Doppler non-invasive intracranial pressure.' Transcranial Doppler (TCD) is a technique primarily aimed at assessing the cerebrovascular dynamics through the cerebral blood flow velocity (FV). Its applicability for nICP assessment emerged from observation that some TCD-derived parameters change during increase of ICP, such as the shape of FV pulse waveform or pulsatility index. Methods were grouped as: based on TCD pulsatility index; aimed at non-invasive estimation of cerebral perfusion pressure and model-based methods. Published studies present with different accuracies, with prediction abilities (AUCs) for detection of ICP ≥20 mmHg ranging from 0.62 to 0.92. This discrepancy could result from inconsistent assessment measures and application in different conditions, from traumatic brain injury to hydrocephalus and stroke. Most of the reports stress a potential advantage of TCD as it provides the possibility to monitor changes of ICP in time. Overall accuracy for TCD-based methods ranges around ±12 mmHg, with a great potential of tracing dynamical changes of ICP in time, particularly those of vasogenic nature.