Noninvasive evaluation of intracranial pressure in patients with traumatic brain injury by transcranial Doppler ultrasound

The Brussels consensus for non-invasive ICP monitoring when invasive systems are not available in the care of TBI patients (the B-ICONIC consensus, recommendations, and management algorithm)

BACKGROUND

Invasive systems are commonly used for monitoring intracranial pressure (ICP) in traumatic brain injury (TBI) and are considered the gold standard. The availability of invasive ICP monitoring is heterogeneous, and in low- and middle-income settings, these systems are not routinely employed due to high cost or limited accessibility. The aim of this consensus was to develop recommendations to guide monitoring and ICP-driven therapies in TBI using non-invasive ICP (nICP) systems.

METHODS

A panel of 41 experts, that regularly use nICP systems for guiding TBI care, was established. Three scoping and four systematic reviews with meta-analysis were performed summarizing the current global-literature evidence. A modified Delphi method was applied for the development of recommendations. An in-person meeting with group discussions and voting was conducted. Strong recommendations were defined for an agreement of at least 85%. Weak recommendations were defined for an agreement of 75-85%.

RESULTS

A total of 34 recommendations were provided (32 Strong, 2 Weak) divided into three domains: general consideration for nICP use, management of ICP using nICP methods and thresholds of nICP tools for escalating/de-escalating treatment. We developed four clinical algorithms for escalating treatment and heatmaps for de-escalating treatment.

CONCLUSIONS

Using a mixed-method approach involving literature review and an in-person consensus by experts, a set of recommendations designed to assist clinicians managing TBI patients using nICP systems plus clinical assessment, in the presence or absence of brain imaging, were built. Further clinical studies are required to validate the potential use of these recommendations in the daily clinical practice.

Diagnostic Accuracy of Optic Nerve Sheath Diameter Measurement by Ultrasonography for Noninvasive Estimation of Intracranial Hypertension in Traumatic Brain Injury: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Intracranial hypertension (IH) is associated with an unfavorable outcome in traumatic brain injury (TBI), and management strategies guided by intracranial pressure monitoring improve prognosis. Owing to the limitations of using invasive devices, measurement of optic nerve sheath diameter (ONSD) by ultrasonography is an alternative noninvasive method. However, its accuracy has not been validated in patients with TBI, so we aim to determine the diagnostic accuracy of measuring ONSD by ultrasonography in patients with TBI to estimate IH, compared with invasive monitoring.

METHODS

Systematic review of electronic databases and manual literature review from inception to June 2023. The analysis included diagnostic accuracy studies of ultrasonographic measurement of ONSD compared with invasive monitoring published in any language and with patients of any age. A qualitative synthesis was performed describing the clinical and methodological characteristics, strengths, limitations, and quality of evidence. In addition, a bivariate random effects model meta-analysis and a hierarchical summary receiver operating characteristics model were performed for the pediatric and adult population separately.

RESULTS

Five hundred and forty eight patients of 688 in 16 eligible studies were adults and 120 were children. Pooled sensitivity and specificity of ONSD measurement by ultrasonography were 84% (95% CI, 76%-89%) and 83% (95% CI, 73%-90%), respectively. During the sensitivity analysis, these parameters exhibited consistent values. Pooled area under the curve was 0.91 for adults and 0.76 for children. Optimal threshold for estimating IH was 5.76 mm for adults and 5.78 mm for children.

CONCLUSION

Measurement of ONSD by ultrasonography is a reliable, low-cost, and safe alternative for the estimation of IH with TBI in adults. More robust studies are needed to overcome the high risk of bias and heterogeneity for this analysis.

Future of neurocritical care: Integrating neurophysics, multimodal monitoring, and machine learning

Multimodal monitoring (MMM) in the intensive care unit (ICU) has become increasingly sophisticated with the integration of neurophysical principles. However, the challenge remains to select and interpret the most appropriate combination of neuromonitoring modalities to optimize patient outcomes. This manuscript reviewed current neuromonitoring tools, focusing on intracranial pressure, cerebral electrical activity, metabolism, and invasive and noninvasive autoregulation monitoring. In addition, the integration of advanced machine learning and data science tools within the ICU were discussed. Invasive monitoring includes analysis of intracranial pressure waveforms, jugular venous oximetry, monitoring of brain tissue oxygenation, thermal diffusion flowmetry, electrocorticography, depth electroencephalography, and cerebral microdialysis. Noninvasive measures include transcranial Doppler, tympanic membrane displacement, near-infrared spectroscopy, optic nerve sheath diameter, positron emission tomography, and systemic hemodynamic monitoring including heart rate variability analysis. The neurophysical basis and clinical relevance of each method within the ICU setting were examined. Machine learning algorithms have shown promise by helping to analyze and interpret data in real time from continuous MMM tools, helping clinicians make more accurate and timely decisions. These algorithms can integrate diverse data streams to generate predictive models for patient outcomes and optimize treatment strategies. MMM, grounded in neurophysics, offers a more nuanced understanding of cerebral physiology and disease in the ICU. Although each modality has its strengths and limitations, its integrated use, especially in combination with machine learning algorithms, can offer invaluable information for individualized patient care.

Preventable trauma deaths in the Western Cape of South Africa: A consensus-based panel review

Injury causes 4.4 million deaths worldwide annually. 90% of all injury-related deaths occur in low-and-middle income countries. Findings from expert-led trauma death reviews can inform strategies to reduce trauma deaths. A cohort of trauma decedents was identified from an on-going study in the Western Cape Province of South Africa. For each case, demographics, injury characteristics, time and location of death and postmortem findings were collected. An expert multidisciplinary panel of reviewed each case, determined preventability and made recommendations for improvement. Analysis of preventable and non-preventable cases was performed using Chi-square, Fisher's exact, and Wilcoxon signed rank tests. A rapid qualitative analysis of recommendations was conducted and descriptively summarized. 138 deaths (48 deceased-on-scene and 90 pre- or in-hospital deaths) were presented to 23 panelists. Overall, 46 (33%) of deaths reviewed were considered preventable or potentially preventable. Of all pre- and in-hospital deaths, late deaths (>24 hours) were more frequently preventable (22, 56%) and due to multi-organ failure and sepsis, compared to early deaths (≤24 hours) with 32 (63%) that were non-preventable and due to central nervous system injury and haemorrhage. 45% of pre and in-hospital deaths were preventable or potentially preventable. The expert panel recommended strengthening community based primary prevention strategies for reducing interpersonal violence alongside health system improvements to facilitate high quality care. For the health system the panel's key recommendations included improving team-based care, adherence to trauma protocols, timely access to radiology, trauma specialists, operative and critical care.

Optic Nerve Sheath Diameter Sonography for the Diagnosis of Intracranial Hypertension in Traumatic Brain Injury: A Systematic Review and Meta-Analysis

OBJECTIVES

Timely diagnosis and management of elevated intracranial pressure (ICP) in patients with traumatic brain injury (TBI) can significantly reduce mortality rates. Ultrasound examination of the optic nerve sheath diameter (ONSD) is considered a potential, noninvasive, and effective method for assessing ICP. We conducted a systematic review and meta-analysis of ONSD ultrasound detection and invasive ICP monitoring methods to compare and evaluate the diagnostic accuracy of ONSD ultrasound detection methods for intracranial hypertension (IH) in patients with TBI.

METHODS

We searched the Web of Science, PubMed, and Embase databases to assess the diagnostic accuracy of ONSD sonography for predicting increased ICP. The 2 authors independently extracted the collected data. Simultaneously, the QUADAS-2 tool was used to evaluate the bias risk of each study and conducted random-effects meta-analyses for the accuracy and specificity of diagnosis, and calculated pooled estimates.

RESULTS

Ten studies with 512 patients were included. The diagnostic accuracy of ONSD sonography for IH was revealed as a pooled sensitivity of 0.85 (95% confidence interval [CI], 0.79-0.89) and specificity of 0.88 (95% CI, 0.80-0.93), compared with the invasive ICP monitoring standard for patients with TBI.

CONCLUSIONS

ONSD sonography may be a useful method for predicting increased ICP in adult patients with TBI. Further clinical studies are required to confirm the diagnostic value of ONSD sonography.

Optic nerve sheath diameter and pulsatility index for the diagnosis and follow-up in pediatric traumatic brain injury: a prospective observational cohort study

PURPOSE

Invasive neuromonitoring could be difficult in children with traumatic brain injury (TBI). This study aimed to determine whether noninvasive intracranial pressure (nICP), calculated via pulsatility index (PI) and optic nerve sheath diameter (ONSD) had correlated with each other and patient outcome.

METHODS

All moderate-severe TBI patients were eligible. Patients with a diagnosis of intoxication that did not affect the mental status or cardiovascular system were enrolled as controls. The PI measurements were routinely performed bilaterally on the middle cerebral artery. A software (QLAB's Q-Apps) was used to calculate PI, which further placed the ICP equation of Bellner et al. Linear probe with a 10 MHz frequency transducer to measure ONSD, which further placed the ICP equation of Robba et al. All measurements were performed by a point-of-care ultrasound certified pediatric intensivist under the supervision of a neurocritical care specialist, before and 30 min after a hypertonic saline (HTS) infusion for every 6 h when the patient's mean arterial pressure, heart rate, body temperature, hemoglobin, and blood CO2 levels were within normal ranges. The secondary outcome was the effect of hypertonic saline (HTS) on nICP. Delta-sodium values of each HTS infusion were calculated as a difference between pre- and post-measurements.

RESULTS

Twenty-five TBI patients (200 measurements) and 19 controls (57 measurements) were included. Median nICP-PI and nICP-ONSD on admission were significantly higher in the TBI group (11.03 (9.98-12.63), p = 0.004, and 13.14 (12.27-14.64), p < 0.001, respectively). Median nICP-ONSD of severe TBI patients were higher than moderate TBI patients (13.58 (13.14-15.71) and 12.30 (9.83-13.14), respectively, p = 0.013). The median nICP-PI was the same across the type of injury (falls and motor vehicle accidents), while the median nICP-ONSD of the motor vehicle accident group was higher than falls. The first nICP-PI and nICP-ONSD measurements in PICU and admission pGCS were negatively correlated (r =  - 0.562, p = 0.003 and r =  - 0.582, p = 0.002, respectively). The mean nICP-ONSD during the study period and admission pGCS and GOS-E peds score significantly correlated. However, the Bland-Altman plots showed significant bias between the two methods of ICP except after 5th dose of HTS. All nICP values significantly decreased in time, and it was most obvious after the 5th dose of HTS. No significant correlations were found between delta sodium levels and nICP.

CONCLUSION

Noninvasive estimation of ICP is helpful for the management of pediatric severe TBI patients. nICP driven by ONSD is more consistent with clinical findings of increased ICP but not useful as a follow-up tool in acute management because of slow circulation of CSF around the optic sheath. The correlation between admission GCS scores and GOS-E peds score favors ONSD as a good candidate for determining disease severity and predicting long-term outcomes.

Associations between intracranial pressure thresholds and multimodal monitoring in acute traumatic neural injury: a scoping review

BACKGROUND

Current moderate/severe traumatic brain injury (TBI) guidelines suggest the use of an intracranial pressure (ICP) treatment threshold of 20 mmHg or 22 mmHg. Over the past decade, the use of various cerebral physiology monitoring devices has been incorporated into neurocritical care practice and termed "multimodal monitoring." Such modalities include those that monitor systemic hemodynamics, systemic and brain oxygenation, cerebral blood flow (CBF), cerebral autoregulation, electrophysiology, and cerebral metabolism. Given that the relationship between ICP and outcomes is not yet entirely understood, a comprehensive review of the literature on the associations between ICP thresholds and multimodal monitoring is still needed.

METHODS

We conducted a scoping review of the literature for studies that present an objective statistical association between ICP above/below threshold and any multimodal monitoring variable. MEDLINE, BIOSIS, Cochrane library, EMBASE, Global Health, and SCOPUS were searched from inception to July 2022 for relevant articles. Full-length, peer-reviewed, original works with a sample size of ≥50 moderate-severe TBI patients were included in this study.

RESULTS

A total of 13 articles were deemed eligible for final inclusion. The included articles were significantly heterogenous in terms of their designs, demographics, and results, making it difficult to draw any definitive conclusions. No literature describing the association between guideline-based ICP thresholds and measures of brain electrophysiology, cerebral metabolism, or direct metrics of CBF was found.

CONCLUSION

There is currently little literature that presents objective statistical associations between ICP thresholds and multimodal monitoring physiology. However, overall, the literature indicates that having ICP above guideline based thresholds is associated with increased blood pressure, increased cardiac decoupling, reduced parenchymal brain oxygen tension, and impaired cerebral autoregulation, with no association with CBF velocity within the therapeutic range of ICP. There was insufficient literature to comment on other multimodal monitoring measures.

Transcranial doppler in the non-invasive estimation of intracranial pressure in traumatic brain injury compared to other non-invasive methods in lower-middle income countries: Systematic review and meta-analysis

BACKGROUND

The prediction of raised Intracranial Pressure (ICP) with accuracy in Traumatic Brain Injury (TBI) patients is a clinically important decision and therapeutic tool. This study aimed to evaluate the existing methods used for non-invasive ICP monitoring in TBI patients in LMICs.

METHODS

Systematic searches of PubMed, Google Scholar, and ScienceDirect were performed from database inception to November 2021. Studies reporting the prediction of raised ICP in TBI patients by non-invasive means in LMICs were included. Pooled estimates of sensitivity, specificity, positive likelihood ratios, and negative likelihood ratios with 95 %CI were calculated for each index test consisting of the fifteen studies, using the MEDDECIDE module 0.0.2 for meta-analysis of diagnostic test accuracy, reliability, and decision studies in JAMOVI 2.2.5.

RESULTS

A total of 1032 studies were identified, of which, 15 included 3316 patients with male predominance (n = 2458, 74.13%). Patients' ages range from 15 to 96 years with 40-80 (n = 1205, 36.34%), the most represented population. The ICP measured by Transcranial Doppler (TCD) had a sensitivity of 92.3%, and a specificity of 70%. The positive predictive value was 66.67%, with a negative predictive value of 93.33%. Furthermore, the positive Likelihood Ratio (+LR) was 3.69; 2<+LR < 5 and the negative Likelihood Ratio (-LR) 0.103; 0.1 < -LR < 0.2. We carried out a "Medical Decision", "Plots", "Fagan Normogram" and the ROC curve to find the perfect discrimination point of all the five tests used for the non-invasive measurement of ICP in the TBI patients in LMICs.

CONCLUSION

The TCD had shown high performance in its sensitivity and specificity, placing it on top of the other four different tests used in LMICs for the management of patients with TBI.

Ultrasound-guided puncture into newborn rat brain

Since the brain structure of neonatal rats was not fully formed during the first 4 days, it cannot be detected using ultrasound. The objective of this study was to investigate the use of ultrasound to guide puncture in the normal coronal brain structure and determine the puncture depth of the location of the cortex, hippocampus, lateral ventricle, and striatum of newborn rats of 5-15 days. The animal was placed in a prone position. The specific positions of the cortex, hippocampus, lateral ventricle, and striatum were measured under ultrasound. Then, the rats were punctured with a stereotaxic instrument, and dye was injected. Finally, the brains of rats were taken to make frozen sections to observe the puncture results. By ultrasound, the image of the cortex, hippocampus, lateral ventricle, and striatum of the rat can be obtained and the puncture depth of the cortex (8 days: 1.02 ± 0.12, 10 days: 1.02 ± 0.08, 13 days: 1.43 ± 0.05), hippocampus (8 days: 2.63 ± 0.07, 10 days: 2.77 ± 0.14, 13 days: 2.82 ± 0.09), lateral ventricle (8 days: 2.08 ± 0.04, 10 days: 2.26 ± 0.03, 13 days: 2.40 ± 0.06), and corpus striatum (8 days: 4.57 ± 0.09, 10 days: 4.94 ± 0.31, 13 days: 5.13 ± 0.10) can be accurately measured. The rat brain structure and puncture depth changed with the age of the rats. Ultrasound technology can not only clarify the brain structure characteristics of 5-15-day-old rats but also guide the puncture and injection of the rat brain structure. The results of this study laid the foundation for the future use of ultrasound in experimental animal models of neurological diseases.

Effect of intracranial pressure on photoplethysmographic waveform in different cerebral perfusion territories: A computational study

Background: Intracranial photoplethysmography (PPG) signals can be measured from extracranial sites using wearable sensors and may enable long-term non-invasive monitoring of intracranial pressure (ICP). However, it is still unknown if ICP changes can lead to waveform changes in intracranial PPG signals.

Aim: To investigate the effect of ICP changes on the waveform of intracranial PPG signals of different cerebral perfusion territories.

Methods: Based on lump-parameter Windkessel models, we developed a computational model consisting three interactive parts: cardiocerebral artery network, ICP model, and PPG model. We simulated ICP and PPG signals of three perfusion territories [anterior, middle, and posterior cerebral arteries (ACA, MCA, and PCA), all left side] in three ages (20, 40, and 60 years) and four intracranial capacitance conditions (normal, 20% decrease, 50% decrease, and 75% decrease). We calculated following PPG waveform features: maximum, minimum, mean, amplitude, min-to-max time, pulsatility index (PI), resistive index (RI), and max-to-mean ratio (MMR).

Results: The simulated mean ICPs in normal condition were in the normal range (8.87–11.35 mm Hg), with larger PPG fluctuations in older subject and ACA/PCA territories. When intracranial capacitance decreased, the mean ICP increased above normal threshold (&gt;20 mm Hg), with significant decreases in maximum, minimum, and mean; a minor decrease in amplitude; and no consistent change in min-to-max time, PI, RI, or MMR (maximal relative difference less than 2%) for PPG signals of all perfusion territories. There were significant effects of age and territory on all waveform features except age on mean.

Conclusion: ICP values could significantly change the value-relevant (maximum, minimum, and amplitude) waveform features of PPG signals measured from different cerebral perfusion territories, with negligible effect on shape-relevant features (min-to-max time, PI, RI, and MMR). Age and measurement site could also significantly influence intracranial PPG waveform.

Noninvasive methods to monitor intracranial pressure

PURPOSE OF REVIEW

Intracranial pressure (ICP) is determined by the production of and outflow facility of cerebrospinal fluid. Since alterations in ICP are implicated in several vision-threatening and life-threatening diseases, measurement of ICP is necessary and common. All current clinical methods to measure ICP are invasive and carry the risk for significant side effects. Therefore, the development of accurate, reliable, objective, and portal noninvasive devices to measure ICP has the potential to change the practice of medicine. This review discusses recent advances and barriers to the clinical implementation of noninvasive devices to determine ICP.

RECENT FINDINGS

Many noninvasive methods to determine ICP have been developed. Although most have significant limitations limiting their clinical utility, several noninvasive methods have shown strong correlations with invasively obtained ICP and have excellent potential to be developed further to accurately quantify ICP and ICP changes.

SUMMARY

Although invasive methods remain the mainstay for ICP determination and monitoring, several noninvasive biomarkers have shown promise to quantitatively assess and monitor ICP. With further refinement and advancement of these techniques, it is highly possible that noninvasive methods will become more commonplace and may complement or even supplant invasively obtained methods to determine ICP in certain situations.

Ultrasound Detection of Intracranial Hypertension in Brain Injuries

In recent years, the measurement of optic nerve sheath diameter with ultrasound to detect the presence of increased intracranial pressure has widely spread. It can be qualitatively and effectively used to identify intracranial hypertension. Intracranial pressure can rise due to acute injury, cerebral bleeding, hydrocephalus, brain tumors and other space-occupying abnormalities, and it is linked to a high death rate. The purpose of this review is to give a general overview of the most relevant scientific publications on ultrasonographic evaluation of the optic nerve in case of brain injuries published in the last 30 years, as well as to analyze the limits of the most extensively used B-scan approach. Fifty-two papers chosen from the PubMed medical database were analyzed in this review. Our findings revealed that ocular ultrasound is an useful diagnostic tool in the management of intracranial hypertension when it exceeds a certain value or after head trauma. As a result, an ultrasound of the optic nerve can be extremely helpful in guiding diagnosis and treatment. The blooming effect is one of the most critical restrictions to consider when using B-scan ultrasonography. Since amplitude-scan ultrasound, also known as A-scan, does not have this limit, these two diagnostic techniques should always be used together for a more full, accurate, and trustworthy ultrasound examination, ensuring more data objectivity.