Transcranial color-coded duplex sonography allows to assess cerebral perfusion pressure noninvasively following severe traumatic brain injury

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.

A pilot clinical study to estimate intracranial pressure utilising cerebral photoplethysmograms in traumatic brain injury patients

PURPOSE

In this research, a non-invasive intracranial pressure (nICP) optical sensor was developed and evaluated in a clinical pilot study. The technology relied on infrared light to probe brain tissue, using photodetectors to capture backscattered light modulated by vascular pulsations within the brain's vascular tissue. The underlying hypothesis was that changes in extramural arterial pressure could affect the morphology of recorded optical signals (photoplethysmograms, or PPGs), and analysing these signals with a custom algorithm could enable the non-invasive calculation of intracranial pressure (nICP).

METHODS

This pilot study was the first to evaluate the nICP probe alongside invasive ICP monitoring as a gold standard. nICP monitoring occurred in 40 patients undergoing invasive ICP monitoring, with data randomly split for machine learning. Quality PPG signals were extracted and analysed for time-based features. The study employed Bland-Altman analysis and ROC curve calculations to assess nICP accuracy compared to invasive ICP data.

RESULTS

Successful acquisition of cerebral PPG signals from traumatic brain injury (TBI) patients allowed for the development of a bagging tree model to estimate nICP non-invasively. The nICP estimation exhibited 95% limits of agreement of 3.8 mmHg with minimal bias and a correlation of 0.8254 with invasive ICP monitoring. ROC curve analysis showed strong diagnostic capability with 80% sensitivity and 89% specificity.

CONCLUSION

The clinical evaluation of this innovative optical nICP sensor revealed its ability to estimate ICP non-invasively with acceptable and clinically useful accuracy. This breakthrough opens the door to further technological refinement and larger-scale clinical studies in the future.

TRIAL REGISTRATION

NCT05632302, 11th November 2022, retrospectively registered.

Estimation of Physiologic Pressures: Invasive and Non-Invasive Techniques, AI Models, and Future Perspectives

The measurement of physiologic pressure helps diagnose and prevent associated health complications. From typical conventional methods to more complicated modalities, such as the estimation of intracranial pressures, numerous invasive and noninvasive tools that provide us with insight into daily physiology and aid in understanding pathology are within our grasp. Currently, our standards for estimating vital pressures, including continuous BP measurements, pulmonary capillary wedge pressures, and hepatic portal gradients, involve the use of invasive modalities. As an emerging field in medical technology, artificial intelligence (AI) has been incorporated into analyzing and predicting patterns of physiologic pressures. AI has been used to construct models that have clinical applicability both in hospital settings and at-home settings for ease of use for patients. Studies applying AI to each of these compartmental pressures were searched and shortlisted for thorough assessment and review. There are several AI-based innovations in noninvasive blood pressure estimation based on imaging, auscultation, oscillometry and wearable technology employing biosignals. The purpose of this review is to provide an in-depth assessment of the involved physiologies, prevailing methodologies and emerging technologies incorporating AI in clinical practice for each type of compartmental pressure measurement. We also bring to the forefront AI-based noninvasive estimation techniques for physiologic pressure based on microwave systems that have promising potential for clinical practice.

The mechanism of white flower formation in Brassica rapa is distinct from that in other Brassica species

KEY MESSAGE

A single nucleotide (G) deletion in the third exon of BraA02.PES2-2 (Bra032957) leads to the conversion of flower color from yellow to white in B. rapa, and knockout mutants of its orthologous genes in B. napus showed white or pale yellow flowers. Brassica rapa (2n = 20, AA) is grown worldwide as an important crop for edible oil and vegetables. The bright yellow flower color and long-lasting flowering period give it aesthetic qualities appealing to countryside tourists. However, the mechanism controlling the accumulation of yellow pigments in B. rapa has not yet been completely revealed. In this study, we characterized the mechanism of white flower formation using a white-flowered natural B. rapa mutant W01. Compared to the petals of yellow-flowered P3246, the petals of W01 have significantly reduced content of yellowish carotenoids. Furthermore, the chromoplasts in white petals of W01 are abnormal with irregularly structured plastoglobules. Genetic analysis indicated that the white flower was controlled by a single recessive gene. By combining BSA-seq with fine mapping, we identified the target gene BraA02.PES2-2 (Bra032957) homologous to AtPES2, which has a single nucleotide (G) deletion in the third exon. Seven homologous PES2 genes including BnaA02.PES2-2 (BnaA02g28340D) and BnaC02.PES2-2 (BnaC02g36410D) were identified in B. napus (2n = 38, AACC), an allotetraploid derived from B. rapa and B. oleracea (2n = 18, CC). Knockout mutants of either one or two of BnaA02.PES2-2 and BnaC02.PES2-2 in the yellow-flowered B. napus cv. Westar by the CRISPR/Cas9 system showed pale-yellow or white flowers. The knock-out mutants of BnaA02.PES2-2 and BnaC02.PES2-2 had fewer esterified carotenoids. These results demonstrated that BraA02.PES2-2 in B. rapa, and BnaA02.PES2-2 and BnaC02.PES2-2 in B. napus play important roles in carotenoids esterification in chromoplasts that contributes to the accumulation of carotenoids in flower petals.

Multimodal and autoregulation monitoring in the neurointensive care unit

Given the complexity of cerebral pathology in patients with acute brain injury, various neuromonitoring strategies have been developed to better appreciate physiologic relationships and potentially harmful derangements. There is ample evidence that bundling several neuromonitoring devices, termed "multimodal monitoring," is more beneficial compared to monitoring individual parameters as each may capture different and complementary aspects of cerebral physiology to provide a comprehensive picture that can help guide management. Furthermore, each modality has specific strengths and limitations that depend largely on spatiotemporal characteristics and complexity of the signal acquired. In this review we focus on the common clinical neuromonitoring techniques including intracranial pressure, brain tissue oxygenation, transcranial doppler and near-infrared spectroscopy with a focus on how each modality can also provide useful information about cerebral autoregulation capacity. Finally, we discuss the current evidence in using these modalities to support clinical decision making as well as potential insights into the future of advanced cerebral homeostatic assessments including neurovascular coupling.

Noninvasive intracranial pressure monitoring in central nervous system infections

Intracranial pressure (ICP) monitoring constitutes an important part of the management of traumatic brain injury. However, its application in other brain pathologies such as neuroinfections like acute bacterial meningitis is unclear. Despite focus on aggressive, prompt treatment, morbidity and mortality from acute bacterial meningitis remain high. Increased ICP is well-known to occur in severe neuroinfections. The increased ICP compromise cerebral perfusion pressure and may ultimately lead to brain stem herniation. Therefore, controlling the ICP could also be important in acute bacterial meningitis. However, risk factors for complications due to invasive monitoring among these patients may be significantly increased due to higher age and levels of comorbidity compared to the traumatic brain injury patient from which the ICP treatment algorithms are developed. This narrative review evaluates the different modalities of ICP monitoring with the aim to elucidate current status of non-invasive alternatives to invasive monitoring as a decision tool and eventually monitoring. Non-invasive screening using ultrasound of the optical nerve sheath, transcranial doppler, magnetic resonance imaging or preferably a combination of these modalities, provides measurements that can be used as a decision guidance for invasive ICP measurement. The available data do not support the replacement of invasive techniques for continuous ICP measurement in patients with increased ICP. Non-invasive modalities should be taken into consideration in patients with neuroinfections at low risk of increased ICP.

Prediction of intracranial lesions in patients with consciousness disturbance by ultrasonography in the intensive care unit

Objective

This study was performed to evaluate the correlation between parameters measured by bedside ultrasonography and detection of intracranial organic lesions in patients with impaired consciousness in an intensive care unit (ICU) setting.

Methods

We retrospectively reviewed the medical records of patients who were admitted to our ICU from April 2017 to July 2019. Patients who underwent computed tomography or magnetic resonance imaging examination and measurement of the flow velocity of the carotid and intracranial arteries and the optic nerve sheath diameter by ultrasonography were selected for analysis.

Results

In total, 64 patients were analyzed in this study. Of these, intracranial lesions were detected by computed tomography or magnetic resonance imaging in 17 (27%) patients. The left:right ratio of the end-diastolic velocity of the bilateral common carotid artery (CCA-ED ratio) and the pulsatility index of the middle cerebral artery (MCA-PI) were significantly higher in patients with than in those without intracranial lesions. The cut-off value of the CCA-ED ratio was 1.55 (sensitivity, 66.7%; specificity, 81.6%), and that of the MCA-PI was 1.21 (sensitivity, 57.1%; specificity, 76.7%).

Conclusion

Bedside ultrasonography is useful for predicting intracranial lesions requiring therapeutic intervention in ICU patients with impaired consciousness.

[Clinical efficacy of restrictive fluid management in patients with severe traumatic brain injury]

OBJECTIVE

To investigate the effects of restrictive fluid management in patients with severe traumatic brain injury (sTBI).

METHODS

Between January, 2019 and June, 2020, we randomly assigned 51 postoperative patients (stay in the ICU of no less than 7 days) with sTBI into treatment group (n=25) with restrictive fluid management and the control group (n=26) with conventional fluid management. The data of optic nerve sheath diameter (ONSD), middle cerebral artery pulsatility index (MAC- PI), neuron-specific enolase (NSE) level, inferior vena cava (IVC) diameter, Glascow Coma Scale (GCS) score, mean arterial blood pressure, heart rate, and fluid balance of the patients were collected at ICU admission and at 1, 3 and 7 days after ICU admission, and the duration of mechanical ventilation, ICU stay, and 28-day mortality were recorded.

RESULTS

The cumulative fluid balance of the two groups were positive on day 1 and negative on days 3 and 7 after ICU admission; at the same time points, the patients in the treatment group had significantly greater negative fluid balance than those in the control group (P < 0.05). In both of the groups, the ONSD and MCA-PI values were significantly higher on day 1 than the baseline (P < 0.05), reached the peak levels on day 3, and decreased on day 7; at the same time point, these values were significantly lower in the treatment group than in the control group (P < 0.05). No significant difference was found in NSE level on day 1 between the two groups (P>0.05); on day 3, NSE level reached the peak level and was significantly higher in the control group (P < 0.05); on day 7, NSE level was lowered the level of day 1 in the treatment group but remained higher than day 1 level in the control group. The 28-day mortality rate did not differ significantly between the two groups (16.00% vs 23.08%, P>0.05); the duration of mechanical ventilation, length of ICU stay, and the number of tracheotomy were all significantly shorter or lower in the treatment group than in the control group (P < 0.05).

CONCLUSIONS

Restrictive fluid management can reduce cerebral edema and improve the prognosis but does not affect the 28-day mortality of patients with sTBI.

Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage

BACKGROUND

Increased intracranial pressure (ICP) causes secondary damage in traumatic brain injury (TBI), and intracranial hemorrhage (ICH). Current methods of ICP monitoring require surgery and carry risks of complications.

OBJECTIVE

To validate a new instrument for noninvasive ICP measurement by comparing values obtained from noninvasive measurements to those from commercial implantable devices through this pilot study.

METHODS

The ophthalmic artery (OA) served as a natural ICP sensor. ICP measurements obtained using noninvasive, self-calibrating device utilizing Doppler ultrasound to evaluate OA flow were compared to standard implantable ICP measurement probes.

RESULTS

A total of 78 simultaneous, paired, invasive, and noninvasive ICP measurements were obtained in 11 ICU patients over a 17-mo period with the diagnosis of TBI, SAH, or ICH. A total of 24 paired data points were initially excluded because of questions about data independence. Analysis of variance was performed first on the 54 remaining data points and then on the entire set of 78 data points. There was no difference between the 2 groups nor was there any correlation between type of sensor and the patient (F[10, 43] = 1.516, P = .167), or the accuracy and precision of noninvasive ICP measurements (F[1, 43] = 0.511, P = .479). Accuracy was [-1.130; 0.539] mm Hg (CL = 95%). Patient-specific calibration was not needed. Standard deviation (precision) was [1.632; 2.396] mm Hg (CL = 95%). No adverse events were encountered.

CONCLUSION

This pilot study revealed no significant differences between invasive and noninvasive ICP measurements (P < .05), suggesting that noninvasive ICP measurements obtained by this method are comparable and reliable.

Review: pathophysiology of intracranial hypertension and noninvasive intracranial pressure monitoring

Measurement of intracranial pressure (ICP) is crucial in the management of many neurological conditions. However, due to the invasiveness, high cost, and required expertise of available ICP monitoring techniques, many patients who could benefit from ICP monitoring do not receive it. As a result, there has been a substantial effort to explore and develop novel noninvasive ICP monitoring techniques to improve the overall clinical care of patients who may be suffering from ICP disorders. This review attempts to summarize the general pathophysiology of ICP, discuss the importance and current state of ICP monitoring, and describe the many methods that have been proposed for noninvasive ICP monitoring. These noninvasive methods can be broken down into four major categories: fluid dynamic, otic, ophthalmic, and electrophysiologic. Each category is discussed in detail along with its associated techniques and their advantages, disadvantages, and reported accuracy. A particular emphasis in this review will be dedicated to methods based on the use of transcranial Doppler ultrasound. At present, it appears that the available noninvasive methods are either not sufficiently accurate, reliable, or robust enough for widespread clinical adoption or require additional independent validation. However, several methods appear promising and through additional study and clinical validation, could eventually make their way into clinical practice.

Obstructive Hydrocephalus Due to Unruptured Brain Arteriovenous Malformation: Demonstrating Transcranial Color Duplex Confirmation of Cerebral Venous Hemodynamic Alterations and Color Duplex Ultrasound Confirmation of Shunt Patency

Given the rarity of arteriovenous malformations of the brain (bAVMs) with concomitant obstructive hydrocephalus, few papers have commented on the resultant hydrodynamic perturbations. To date, no study has specifically investigated the effect of ventricular shunting on intracranial venous parameters as measured by transcranial color duplex ultrasound (TCCD). This study investigates whether TCCD and color duplex ultrasound are useful modalities to elucidate the physiological and hemodynamic changes in a patient with bAVM following ventricular shunting.

Using TCCD, this study demonstrates that preoperatively, there is a decrease in cerebral capacitance, manifesting in a decrease in cerebral inflow and reduced venous outflow. Following shunt insertion, intracranial compliance is increased, resulting in the dilatation of previously compressed capacitance vessels and restoration of venous compliance. Color duplex ultrasound (CDU) was a useful determinant of shunt patency in the neck.

We report the first TCCD assessment of hemodynamic changes of the intracranial circulation in a patient with bAVM following ventricular-peritoneal shunting. The results lend conceptual support of a pressure gradient change with high pressure that occurs in the veins as compared to the subarachnoid space.

Identification of Pulse Onset on Cerebral Blood Flow Velocity Waveforms: A Comparative Study

The low cost, simple, noninvasive, and continuous measurement of cerebral blood flow velocity (CBFV) by transcranial Doppler is becoming a common clinical tool for the assessment of cerebral hemodynamics. CBFV monitoring can also help with noninvasive estimation of intracranial pressure and evaluation of mild traumatic brain injury. Reliable CBFV waveform analysis depends heavily on its accurate beat-to-beat delineation. However, CBFV is inherently contaminated with various types of noise/artifacts and has a wide range of possible pathological waveform morphologies. Thus, pulse onset detection is in general a challenging task for CBFV signal. In this paper, we conducted a comprehensive comparative analysis of three popular pulse onset detection methods using a large annotated dataset of 92,794 CBFV pulses—collected from 108 subarachnoid hemorrhage patients admitted to UCLA Medical Center. We compared these methods not only in terms of their accuracy and computational complexity, but also for their sensitivity to the selection of their parameters' values. The results of this comprehensive study revealed that using optimal values of the parameters obtained from sensitivity analysis, one method can achieve the highest accuracy for CBFV pulse onset detection with true positive rate (TPR) of 97.06% and positive predictivity value (PPV) of 96.48%, when error threshold is set to just less than 10 ms. We conclude that the high accuracy and low computational complexity of this method (average running time of 4ms/pulse) makes it a reliable algorithm for CBFV pulse onset detection.

Data-Augmented Modeling of Intracranial Pressure

Precise management of patients with cerebral diseases often requires intracranial pressure (ICP) monitoring, which is highly invasive and requires a specialized ICU setting. The ability to noninvasively estimate ICP is highly compelling as an alternative to, or screening for, invasive ICP measurement. Most existing approaches for noninvasive ICP estimation aim to build a regression function that maps noninvasive measurements to an ICP estimate using statistical learning techniques. These data-based approaches have met limited success, likely because the amount of training data needed is onerous for this complex applications. In this work, we discuss an alternative strategy that aims to better utilize noninvasive measurement data by leveraging mechanistic understanding of physiology. Specifically, we developed a Bayesian framework that combines a multiscale model of intracranial physiology with noninvasive measurements of cerebral blood flow using transcranial Doppler. Virtual experiments with synthetic data are conducted to verify and analyze the proposed framework. A preliminary clinical application study on two patients is also performed in which we demonstrate the ability of this method to improve ICP prediction.

Intensive Care in Traumatic Brain Injury Including Multi-Modal Monitoring and Neuroprotection

Moderate to severe traumatic brain injuries (TBI) require treatment in an intensive care unit (ICU) in close collaboration of a multidisciplinary team consisting of different medical specialists such as intensivists, neurosurgeons, neurologists, as well as ICU nurses, physiotherapists, and ergo-/logotherapists. Major goals include all measurements to prevent secondary brain injury due to secondary brain insults and to optimize frame conditions for recovery and early rehabilitation. The distinction between moderate and severe is frequently done based on the Glascow Coma Scale and therefore often is just a snapshot at the early time of assessment. Due to its pathophysiological pathways, an initially as moderate classified TBI may need the same sophisticated surveillance, monitoring, and treatment as a severe form or might even progress to a severe and difficult to treat affection. As traumatic brain injury is rather a syndrome comprising a range of different affections to the brain and as, e.g., age-related comorbidities and treatments additionally may have a great impact, individual and tailored treatment approaches based on monitoring and findings in imaging and respecting pre-injury comorbidities and their therapies are warranted.

Effects of pneumoperitoneum and Trendelenburg position on intracranial pressure assessed using different non-invasive methods

BACKGROUND

The laparoscopic approach is becoming increasingly frequent for many different surgical procedures. However, the combination of pneumoperitoneum and Trendelenburg positioning associated with this approach may increase the patient's risk for elevated intracranial pressure (ICP). Given that the gold standard for the measurement of ICP is invasive, little is known about the effect of these common procedures on ICP.

METHODS

We prospectively studied 40 patients without any history of cerebral disease who were undergoing laparoscopic procedures. Three different methods were used for non-invasive estimation of ICP: ultrasonography of the optic nerve sheath diameter (ONSD); transcranial Doppler-based (TCD) pulsatility index (ICP_PI); and a method based on the diastolic component of the TCD cerebral blood flow velocity (ICP_FVd). The ONSD and TCD were measured immediately after induction of general anaesthesia, after pneumoperitoneum insufflation, after Trendelenburg positioning, and again at the end of the procedure.

RESULTS

The ONSD, ICP_FVd, and ICP_PI increased significantly after the combination of pneumoperitoneum insufflation and Trendelenburg positioning. The ICP_FVd showed an area under the curve of 0.80 [95% confidence interval (CI) 0.70-0.90] to distinguish the stage associated with the application of pneumoperitoneum and Trendelenburg position; ONSD and ICP_PI showed an area under the curve of 0.75 (95% CI 0.65-0.86) and 0.70 (95% CI 0.58-0.81), respectively.

CONCLUSIONS

The concomitance of pneumoperitoneum and the Trendelenburg position can increase ICP as estimated with non-invasive methods. In high-risk patients undergoing laparoscopic procedures, non-invasive ICP monitoring through a combination of ONSD ultrasonography and TCD-derived ICP_FVd could be a valid option to assess the risk of increased ICP.

Ultrasound Imaging for Traumatic Brain Injury

Traumatic brain injury (TBI) is challenging to assess even with recent advancements in computed tomography and magnetic resonance imaging. Ultrasound (US) imaging has previously been less utilized in TBI compared to conventional imaging because of limited resolution in the intracranial space. However, there have been substantial improvements in contrast-enhanced US and development of novel techniques such as intravascular US. Also, continued research provides further insight into cerebrovascular parameters from transcranial Doppler imaging. These advancements in US imaging provides the community of TBI imaging researchers and clinicians new opportunities in clinically monitoring and understanding the pathologic mechanisms of TBI.

Noninvasive Neuromonitoring: Current Utility in Subarachnoid Hemorrhage, Traumatic Brain Injury, and Stroke

Noninvasive neuromonitoring is increasingly being used to monitor the course of primary brain injury and limit secondary brain damage of patients in the neurocritical care unit. Proposed advantages over invasive neuromonitoring methods include a lower risk of infection and bleeding, no need for surgical installation, mobility and portability of some devices, and safety. The question, however, is whether noninvasive neuromonitoring is practical and trustworthy enough already. We searched the recent literature and reviewed English-language studies on noninvasive neuromonitoring in subarachnoid hemorrhage, traumatic brain injury, and ischemic and hemorrhagic stroke between the years 2010 and 2015. We found 88 studies that were eligible for review including the methods transcranial ultrasound, electroencephalography, evoked potentials, near-infrared spectroscopy, bispectral index, and pupillometry. Noninvasive neuromonitoring cannot yet completely replace invasive methods in most situations, but has great potential being complementarily integrated into multimodality monitoring, for guiding management, and for limiting the use of invasive devices and in-hospital transports for imaging.

Invasive and noninvasive means of measuring intracranial pressure: a review

Measurement of intracranial pressure (ICP) can be invaluable in the management of critically ill patients. Cerebrospinal fluid is produced by the choroid plexus in the brain ventricles (a set of communicating chambers), after which it circulates through the different ventricles and exits into the subarachnoid space around the brain, where it is reabsorbed into the venous system. If the fluid does not drain out of the brain or get reabsorbed, the ICP increases, which may lead to brain damage or death. ICP elevation accompanied by dilatation of the cerebral ventricles is termed hydrocephalus, whereas ICP elevation accompanied by normal or small ventricles is termed idiopathic intracranial hypertension.

OBJECTIVE

We performed a comprehensive literature review on how to measure ICP invasively and noninvasively.

APPROACH

This review discusses the advantages and disadvantages of current invasive and noninvasive approaches.

MAIN RESULTS

Invasive methods remain the most accurate at measuring ICP, but they are prone to a variety of complications including infection, hemorrhage and neurological deficits. Ventricular catheters remain the gold standard but also carry the highest risk of complications, including difficult or incorrect placement. Direct telemetric intraparenchymal ICP monitoring devices are a good alternative. Noninvasive methods for measuring and evaluating ICP have been developed and classified in five broad categories, but have not been reliable enough to use on a routine basis. These methods include the fluid dynamic, ophthalmic, otic, and electrophysiologic methods, as well as magnetic resonance imaging, transcranial Doppler ultrasonography (TCD), cerebral blood flow velocity, near-infrared spectroscopy, transcranial time-of-flight, spontaneous venous pulsations, venous ophthalmodynamometry, optical coherence tomography of retina, optic nerve sheath diameter (ONSD) assessment, pupillometry constriction, sensing tympanic membrane displacement, analyzing otoacoustic emissions/acoustic measure, transcranial acoustic signals, visual-evoked potentials, electroencephalography, skull vibrations, brain tissue resonance and the jugular vein.

SIGNIFICANCE

This review provides a current perspective of invasive and noninvasive ICP measurements, along with a sense of their relative strengths, drawbacks and areas for further improvement. At present, none of the noninvasive methods demonstrates sufficient accuracy and ease of use while allowing continuous monitoring in routine clinical use. However, they provide a realizable ICP measurement in specific patients especially when invasive monitoring is contraindicated or unavailable. Among all noninvasive ICP measurement methods, ONSD and TCD are attractive and may be useful in selected settings though they cannot be used as invasive ICP measurement substitutes. For a sufficiently accurate and universal continuous ICP monitoring method/device, future research and developments are needed to integrate further refinements of the existing methods, combine telemetric sensors and/or technologies, and validate large numbers of clinical studies on relevant patient populations.

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.

Estimating the accuracy of optic nerve sheath diameter measurement using a pocket-sized, handheld ultrasound on a simulation model

BACKGROUND

Ultrasound measurement of optic nerve sheath diameter (ONSD) appears to be a promising, rapid, non-invasive bedside tool for identification of elevated intra-cranial pressure. With improvements in ultrasound technology, machines are becoming smaller; however, it is unclear if these ultra-portable handheld units have the resolution to make these measurements precisely. In this study, we estimate the accuracy of ONSD measurement in a pocket-sized ultrasound unit.

METHODS

Utilizing a locally developed, previously validated model of the eye, ONSD was measured by two expert observers, three times with two machines and on five models with different optic nerve sheath sizes. A pocket ultrasound (Vscan, GE Healthcare) and a standard portable ultrasound (M-Turbo, SonoSite) were used to measure the models. Data was analyzed by Bland-Altman plot and intra-class correlation coefficient (ICC).

RESULTS

The ICC between raters for the SonoSite was 0.878, and for the Vscan was 0.826. The between-machine agreement ICC was 0.752. Bland-Altman agreement analysis between the two ultrasound methods showed an even spread across the range of sheath sizes, and that the Vscan tended to read on average 0.33 mm higher than the SonoSite for each measurement, with a standard deviation of 0.65 mm.

CONCLUSIONS

Accurate ONSD measurement may be possible utilizing pocket-sized, handheld ultrasound devices despite their small screen size, lower resolution, and lower probe frequencies. Further study in human subjects is warranted for all newer handheld ultrasound models as they become available on the market.

Doppler Non-invasive Monitoring of ICP in an Animal Model of Acute Intracranial Hypertension

BACKGROUND

In many neurological diseases, intracranial pressure (ICP) is elevated and needs to be actively managed. ICP is typically measured with an invasive transducer, which carries risks. Non-invasive techniques for monitoring ICP (nICP) have been developed. The aim of this study was to compare three different methods of transcranial Doppler (TCD) assessment of nICP in an animal model of acute intracranial hypertension.

METHODS

In 28 rabbits, ICP was increased to 70-80 mmHg by infusion of Hartmann's solution into the lumbar subarachnoid space. Doppler flow velocity in the basilar artery was recorded. nICP was assessed through three different methods: Gosling's pulsatility index PI (gPI), Aaslid's method (AaICP), and a method based on diastolic blood flow velocity (FVdICP).

RESULTS

We found a significant correlation between nICP and ICP when all infusion experiments were combined (FVdICP: r = 0.77, AaICP: r = 0.53, gPI: r = 0.54). The ability to distinguish between raised and 'normal' values of ICP was greatest for FVdICP (AUC 0.90 at ICP >40 mmHg). When infusion experiments were considered independently, FVdICP demonstrated again the strongest correlation between changes in ICP and changes in nICP (mean r = 0.85).

CONCLUSIONS

TCD-based methods of nICP monitoring are better at detecting changes of ICP occurring in time, rather than absolute prediction of ICP as a number. Of the studied methods of nICP, the method based on FVd is best to discriminate between raised and 'normal' ICP and to monitor relative changes of ICP.

The diagnostic performance of ultrasonographic optic nerve sheath diameter and color Doppler indices of the ophthalmic arteries in detecting elevated intracranial pressure

OBJECTIVES

To assess the diagnostic accuracy of ultrasonographic optic nerve sheath diameter (ONSD) measurement and color Doppler indices of the ophthalmic arteries in detecting elevated intracranial pressure (ICP).

PATIENTS AND METHODS

A total 60 patients with (cases, n=30) and without (controls, n=30) acute clinical and computed tomographic findings of elevated ICP due to intracranial mass/hemorrhage were recruited from a teaching hospital. The mean binocular and maximum ultrasonographic ONSDs, as well as the mean binocular Doppler ultrasound waveform indices of the ophthalmic arteries including pulsatility index (PI), resistive index (RI), end-systolic velocity (ESV), peak systolic velocity (PSV) and end-diastolic velocity (EDV) were compared between the two groups.

RESULTS

Compared to controls, the case group had significantly higher mean binocular ONSD (5.48 ± 0.52 mm vs. 4.09 ± 0.22 mm, p<0.001), maximum ONSD (5.63 ± 0.55 mm vs. 4.16 ± 0.23 mm, p<0.001), mean PI (1.53 ± 0.16 vs. 1.45 ± 0.20, p=0.01), and mean RI (0.76 ± 0.07 vs. 0.73 ± 0.04, p=0.01). The mean EDV, in contrast, was significantly higher in controls (8.55 ± 3.09 m/s vs. 7.17 ± 2.61 m/s, p=0.01). The two groups were comparable for the mean PSV (30.73 ± 7.93 m/s in cases vs. 32.27 ± 10.39 m/s in controls, p=0.36). Among the mentioned variables, the mean binocular ONSD was the most accurate parameter in detecting elevated ICP (sensitivity and specificity of 100%, cut-off point=4.53 mm). The Doppler indices were only moderately accurate (sensitivity: 56.7-60%, specificity: 63.3-76.7%).

CONCLUSION

While the ultrasonographic mean binocular ONSD (>4.53 mm) was completely accurate in detecting elevated ICP, color Doppler indices of the ophthalmic arteries were of limited value.

Transcranial Doppler Sonography in Pediatric Neurocritical Care: A Review of Clinical Applications and Case Illustrations in the Pediatric Intensive Care Unit

Transcranial Doppler sonography is a noninvasive, real-time physiologic monitor that can detect altered cerebral hemodynamics during catastrophic brain injury. Recent data suggest that transcranial Doppler sonography may provide important information about cerebrovascular hemodynamics in children with traumatic brain injury, intracranial hypertension, vasospasm, stroke, cerebrovascular disorders, central nervous system infections, and brain death. Information derived from transcranial Doppler sonography in these disorders may elucidate underlying pathophysiologic characteristics, predict outcomes, monitor responses to treatment, and prompt a change in management. We review emerging applications for transcranial Doppler sonography in the pediatric intensive care unit with case illustrations from our own experience.

Transocular Doppler and optic nerve sheath diameter monitoring to detect intracranial hypertension

Background:

Increases in intracranial pressure (ICP) require a rapid recognition to allow for adequate treatments. The aim of this study was to determine whether transocular Doppler and optic nerve sheath diameter (ONSD) monitoring could reliably identify increases in ICP.

Materials and Methods:

This is a cross-sectional case-control study, which was carried out on 2013. Subjects were chosen from patients who admitted to the neurology and neurosurgery departments and the intensive care unit of Alzahra Hospital (Isfahan, Iran). To measure the ICP, the authors used ultrasound to measure the diameter of the optic nerve sheath and transocular Doppler (TOD) to measure blood flew velocity in ophthalmic artery (OA) and ophthalmic vein (OV) in both groups.

Results:

The mean of ONSD was 4.8 mm (SD 0.77) in patients with raised ICP and 3.2 mm (SD 0.3) in healthy volunteers which was significant (P < 0.001). The mean (SD) of TOD parameters were also significantly more in OA and OV of patients with raised ICP.

Conclusion:

Ultrasound methods has been proposed as an alternative safe technique for invasive ICP measuring methods.

Intraoperative non invasive intracranial pressure monitoring during pneumoperitoneum: a case report and a review of the published cases and case report series

Non-invasive measurement of ICP (nICP) can be warranted in patients at risk for developing increased ICP during pneumoperitoneum (PP). Our aim was to assess available data on the application of nICP monitoring during these procedures and to present a patient assessed with an innovative combination of noninvasive tools. Literature review of nICP assessment during PP did not find any studies comparing different methods intraprocedurally and only few studies of any nICP monitoring were available: transcranial Doppler (TCD) studies used the pulsatility index (PI) as an estimator of ICP and failed to detect a significant ICP increase during PP, whereas two out of three optic nerve sheath diameter (ONSD) studies detected a statistically significant ICP increase. In the case study, we describe a 52 year old man with a high grade thalamic glioma who underwent urgent laparoscopic cholecystectomy. Considering the high intraoperative risk of developing intracranial hypertension, he was monitored through parallel ONSD ultrasound measurement and TCD derived formulae (flow velocity diastolic formula, FVdnICP, and PI). ONSD and FVdnICP methods indicated a significant ICP increase during PP, whereas PI was not significantly increased. Our experience, combined with the literature review, seems to suggest that PI might not detect ICP changes in this context, however we indicate a possible interest of nICP monitoring during PP by means of ONSD and of TCD derived FVdNICP, especially for patients at risk for increased ICP.

Advances in neuro-monitoring

Neuromonitoring aims to detect harmful physiologic events, early enough to guide the treatment instituted. Evidences encourage us to implement multimodal monitoring, as no single monitor is capable of providing a complete picture of dynamic cerebral state. This review highlights the role of intracranial pressure monitoring, cerebral oxygenation (jugular venous oximetry, brain tissue oxygenation, near infrared oximetry, cerebral microdialysis) and cerebral blood flow monitoring (direct and indirect methods) in the management of neurologically injured patients. In this context, the recent developments of these monitors along with the relevant clinical implications have been discussed. Nevertheless, the diverse range of data obtained from these monitors needs to be integrated and simplified for the clinician. Hence, the future research should focus on identification of a most useful monitor for integration into multimodal system.

A non-invasive method to assess cerebral perfusion pressure in geriatric patients with suspected cerebrovascular disease

Background

Cerebral perfusion pressure (CPP) can adversely impact cerebrovascular hemodynamics but cannot be practically measured in most clinical settings. Here, we aimed to establish a representative mathematical model for CPP in geriatric patients with suspected cerebrovascular disease.

Methods

A total of 100 patients (54 males and 46 females between 60–80 years of age) with suspected cerebrovascular disease and no obvious cerebrovascular stenosis were selected for invasive CPP monitoring via catheterization of the middle segment of the common carotid arteries and openings of the vertebral arteries bilaterally. Curves were function-fitted using MATLAB 7.0, and data was statistically processed by SPSS 20.0.

Results

MATLAB 7.0 constructed eighth-order Fourier functions that fit all recorded CPP curves. Since the coefficients of the 100 functions were significantly different, all functions were standardized to derive one representative function. By manipulating the heart rate and maximum/minimum CPP of the representative function, estimated CPP curves can be constructed for patients with differing heart rates, intracranial pressures (ICPs) and blood pressures.

Conclusions

CPP can be well-modeled through an eighth-order Fourier function that can be constructed from a patient’s brachial artery blood pressure (BABP), ICP and heart rate. This function is representative of geriatric patients with cerebrovascular disease and can be used in the future study of cerebral hemodynamics.

Update in intracranial pressure evaluation methods and translaminar pressure gradient role in glaucoma

Glaucoma is one of the leading causes of blindness worldwide. Historically, it has been considered an ocular disease primary caused by pathological intraocular pressure (IOP). Recently, researchers have emphasized intracranial pressure (ICP), as translaminar counter pressure against IOP may play a role in glaucoma development and progression. It remains controversial what is the best way to measure ICP in glaucoma. Currently, the 'gold standard' for ICP measurement is invasive measurement of the pressure in the cerebrospinal fluid via lumbar puncture or via implantation of the pressure sensor into the brains ventricle. However, the direct measurements of ICP are not without risk due to its invasiveness and potential risk of intracranial haemorrhage and infection. Therefore, invasive ICP measurements are prohibitive due to safety needs, especially in glaucoma patients. Several approaches have been proposed to estimate ICP non-invasively, including transcranial Doppler ultrasonography, tympanic membrane displacement, ophthalmodynamometry, measurement of optic nerve sheath diameter and two-depth transcranial Doppler technology. Special emphasis is put on the two-depth transcranial Doppler technology, which uses an ophthalmic artery as a natural ICP sensor. It is the only method which accurately and precisely measures absolute ICP values and may provide valuable information in glaucoma.

Body temperature affects cerebral hemodynamics in acutely brain injured patients: an observational transcranial color-coded duplex sonography study

Introduction

Temperature changes are common in patients in a neurosurgical intensive care unit (NICU): fever is frequent among severe cases and hypothermia is used after cardiac arrest and is currently being tested in clinical trials to lower intracranial pressure (ICP). This study investigated cerebral hemodynamics when body temperature varies in acute brain injured patients.

Methods

We enrolled 26 patients, 14 with acute brain injury who developed fever and were given antipyretic therapy (defervescence group) and 12 who underwent an intracranial neurosurgical procedure and developed hypothermia in the operating room; once admitted to the NICU, still under anesthesia, they were re-warmed before waking (re-warming group). We measured cerebral blood flow velocity (CBF-V) and pulsatility index (PI) at the middle cerebral artery using transcranial color-coded duplex sonography (TCCDS).

Results

In the defervescence group mean CBF-V decreased from 75 ± 26 (95% CI 65 to 85) to 70 ± 22 cm/s (95% CI 61 to 79) (P = 0.04); the PI also fell, from 1.36 ± 0.33 (95% CI 1.23 to 1.50) to 1.16 ± 0.26 (95% CI 1.05 to 1.26) (P = 0.0005). In the subset of patients with ICP monitoring, ICP dropped from 16 ± 8 to 12 ± 6 mmHg (P = 0.003). In the re-warming group mean CBF-V increased from 36 ± 10 (95% CI 31 to 41) to 39 ± 13 (95% CI 33 to 45) cm/s (P = 0.04); the PI rose from 0.98 ± 0.14 (95% CI 0.91 to 1.04) to 1.09 ± 0.22 (95% CI 0.98 to 1.19) (P = 0.02).

Conclusions

Body temperature affects cerebral hemodynamics as evaluated by TCCDS; when temperature rises, CBF-V increases in parallel, and viceversa when temperature decreases. When cerebral compliance is reduced and compensation mechanisms are exhausted, even modest temperature changes can greatly affect ICP.

Monitoring of intracranial pressure in patients with traumatic brain injury

Since Monro published his observations on the nature of the contents of the intracranial space in 1783, there has been investigation of the unique relationship between the contents of the skull and the intracranial pressure (ICP). This is particularly true following traumatic brain injury (TBI), where it is clear that elevated ICP due to the underlying pathological processes is associated with a poorer clinical outcome. Consequently, there is considerable interest in monitoring and manipulating ICP in patients with TBI. The two techniques most commonly used in clinical practice to monitor ICP are via an intraventricular or intraparenchymal catheter with a microtransducer system. Both of these techniques are invasive and are thus associated with complications such as hemorrhage and infection. For this reason, significant research effort has been directed toward development of a non-invasive method to measure ICP. The principle aims of ICP monitoring in TBI are to allow early detection of secondary hemorrhage and to guide therapies that limit intracranial hypertension (ICH) and optimize cerebral perfusion. However, information from the ICP value and the ICP waveform can also be used to assess the intracranial volume-pressure relationship, estimate cerebrovascular pressure reactivity, and attempt to forecast future episodes of ICH.

Prolonged continuous intravenous infusion of the dipeptide L-alanine- L-glutamine significantly increases plasma glutamine and alanine without elevating brain glutamate in patients with severe traumatic brain injury

INTRODUCTION

Low plasma glutamine levels are associated with worse clinical outcome. Intravenous glutamine infusion dose- dependently increases plasma glutamine levels, thereby correcting hypoglutaminemia. Glutamine may be transformed to glutamate which might limit its application at a higher dose in patients with severe traumatic brain injury (TBI). To date, the optimal glutamine dose required to normalize plasma glutamine levels without increasing plasma and cerebral glutamate has not yet been defined.

METHODS

Changes in plasma and cerebral glutamine, alanine, and glutamate as well as indirect signs of metabolic impairment reflected by increased intracranial pressure (ICP), lactate, lactate-to-pyruvate ratio, electroencephalogram (EEG) activity were determined before, during, and after continuous intravenous infusion of 0.75 g L-alanine-L-glutamine which was given either for 24 hours (group 1, n = 6) or 5 days (group 2, n = 6) in addition to regular enteral nutrition. Lab values including nitrogen balance, urea and ammonia were determined daily.

RESULTS

Continuous L-alanine-L-glutamine infusion significantly increased plasma and cerebral glutamine as well as alanine levels, being mostly sustained during the 5 day infusion phase (plasma glutamine: from 295 ± 62 to 500 ± 145 μmol/ l; brain glutamine: from 183 ± 188 to 549 ± 120 μmol/ l; plasma alanine: from 327 ± 91 to 622 ± 182 μmol/ l; brain alanine: from 48 ± 55 to 89 ± 129 μmol/ l; p < 0.05, ANOVA, post hoc Dunn's test).

CONCLUSIONS

High dose L-alanine-L-glutamine infusion (0.75 g/ kg/ d up to 5 days) increased plasma and brain glutamine and alanine levels. This was not associated with elevated glutamate or signs of potential glutamate-mediated cerebral injury. The increased nitrogen load should be considered in patients with renal and hepatic dysfunction.

TRIAL REGISTRATION

Clinicaltrials.gov NCT02130674. Registered 5 April 2014.

Usefulness of transcranial Doppler-derived cerebral hemodynamic parameters in the noninvasive assessment of intracranial pressure

BACKGROUND

Transcranial Doppler (TCD) ultrasonography is a noninvasive bedside tool that can evaluate cerebral blood flow hemodynamics in major intracranial arteries. TCD-derived pulsatility index (PI) is believed to be influenced by intracranial pressure (ICP).

OBJECTIVE

To correlate TCD-PI with cerebrospinal fluid (CSF) pressure (representing ICP), measured by standard lumbar puncture (LP) manometry.

METHODS

CSF pressures (CSF-P) were measured in 78 patients by LP manometry. Stable TCD spectra were obtained 5 minutes before LP from either middle cerebral arteries using Spencer's head frame and 2-MHz transducer. PI values were calculated from the TCD spectra by an independent neurosonologist.

RESULTS

Factors displaying a significant relationship with CSF-P included age (R = -.426, P < .0005); EDV (R = -.328, P = .002;) and PI (R = .650, P < .0005). On analyzing dichotomized data (CSF-P < 20 vs. ≥ 20 cm H2 0) TCD-PI was an independent determinant (OR per .1 increase in PI = 2.437; 95% CI, 1.573-3.777; P < .0005). PI ≥ 1.26 could reliably predict CSF-P ≥ 20 cm H2 0 (sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy were 81.1%, 96.3%, 93.8%, 88.1%, and 90.1% respectively).

CONCLUSION

TCD-derived PI could be used to identify patients with CSF-P ≥ 20 cm H2 0 and may play an important role as a monitoring tool.

Monitoring of acute traumatic brain injury in adults to prevent secondary brain damage

ABSTRACT: Traumatic brain injury is typically characterized by the primary injury initiating a cascade of pathologic changes that then lead to secondary brain injury. Secondary brain injury is amenable to different therapeutic options. Monitoring of otherwise occult pathologic changes involving oxygenation and metabolism is crucial for treatment decisions. Currently, decision-making is mainly based on measuring intracranial pressure and cerebral perfusion pressure. Importantly, extending neuromonitoring by including parameters reflecting cerebral perfusion, oxygenation and metabolism may improve treatment of traumatic brain injury patients by detecting neuronal damage despite optimal intracranial pressure or cerebral perfusion pressure and preventing unnecessarily aggressive treatment potentially causing local and systemic harm. In this review, the authors describe the advantages and disadvantages of contemporary, extended neuromonitoring methods in traumatic brain injury patients aimed at unmasking secondary brain damage as early as possible.

Management of intracerebral pressure in the neurosciences critical care unit

Management of intracranial pressure in neurocritical care remains a potentially valuable target for improvements in therapy and patient outcomes. Surrogate markers of increased intracranial pressure, invasive monitors, and standard therapy, as well as promising new approaches to improve cerebral compliance are discussed, and a current review of the literature addressing this metric in neuroscience critical care is provided.

Monitoring cerebral autoregulation after head injury. Which component of transcranial Doppler flow velocity is optimal?

BACKGROUND

Cerebral autoregulation assessed using transcranial Doppler (TCD) mean flow velocity (FV) in response to various physiological challenges is predictive of outcome after traumatic brain injury (TBI). Systolic and diastolic FV have been explored in other diseases. This study aims to evaluate the systolic, mean and diastolic FV for monitoring autoregulation and predicting outcome after TBI.

METHODS

300 head-injured patients with blood pressure (ABP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), and FV recordings were studied. Autoregulation was calculated as a correlation of slow changes in diastolic, mean and systolic components of FV with CPP (Dx, Mx, Sx, respectively) and ABP (Dxa, Mxa, Sxa, respectively) from 30 consecutive 10 s averaged values. The relationship with age, severity of injury, and dichotomized 6 months outcome was examined.

RESULTS

Association with outcome was significant for Mx and Sx. For favorable/unfavorable and death/survival outcomes Sx showed the strongest association (F = 20.11; P = 0.00001 and F = 13.10; P = 0.0003, respectively). Similarly, indices derived from ABP demonstrated the highest discriminatory value when systolic FV was used (F = 12.49; P = 0.0005 and F = 5.32; P = 0.02, respectively). Indices derived from diastolic FV demonstrated significant differences (when calculated using CPP) only when comparing between fatal and non-fatal outcome.

CONCLUSIONS

Systolic flow indices (Sx and Sxa) demonstrated a stronger association with outcome than the mean flow indices (Mx and Mxa), irrespective of whether CPP or ABP was used for calculation.

Preliminary Experience of Assessment of Intracranial Lesions by Ultrasound in Multiple Trauma Patients Undergoing Craniectomy

Objective

To explore the feasibility and reliability of B-mode ultrasound for assessment of intracranial lesions in multiple trauma patients who had undergone craniectomy.

Design

ingle-centre study.

Setting

A 16-bed emergency intensive care unit (ICU) in the emergency department of 2nd Affiliated Hospital of Zhejiang University School of Medicine from July 2006 to June 2010.

Methods

We retrospectively analysed 13 multiple trauma patients with severe head injury admitted to the emergency department of 2nd Affiliated Hospital of Zhejiang University School of Medicine. All 13 patients were admitted to the ICU after craniectomy and received mechanical ventilation. Computed tomography (CT) were conducted when patients' consciousness, pupillary size, light reflex changed apparently, or if the bone window tension and the intracranial pressure increased unexpectedly. Head ultrasonography was performed within 2 hours of CT scanning.

Results

Ultrasonography revealed 18 pathological changes in the 13 patients. CT and a second operation helped to identify 23 pathological changes. The results of B-mode ultrasound were compared with those of CT and the coincidence rate was 78.3%, with no significant difference in the diagnosis of delayed haematoma or midline shift (Kappa=0.898, p<0.05).

Conclusions

Transcranial ultrasonography may be a useful tool for monitoring post-operation intracranial lesions in multiple trauma patients with severe head injury. It is an effective supplement to CT.

Rapid detection of recurrent intraventricular hemorrhage by ultrasound in a multiple trauma patient who had undergone craniectomy

Ultrasound may be a useful tool to evaluate intracranial abnormalities in critically ill patients undergoing decompressive craniectomy. We present a multiple trauma patient who had undergone craniectomy and in whom recurrent intraventricular hemorrhage and patterns of cerebral blood flow were rapidly detected by ultrasound.

Reliability of the Blood Flow Velocity Pulsatility Index for Assessment of Intracranial and Cerebral Perfusion Pressures in Head-Injured Patients

BACKGROUND:

It has been postulated that the Gosling pulsatility index (PI) assessed with transcranial Doppler (TCD) has a diagnostic value for noninvasive estimation of intracranial pressure (ICP) and cerebral perfusion pressure (CPP).

OBJECTIVE:

To revisit this hypothesis with the use of a database of digitally stored signals from a cohort of head-injured patients.

METHODS:

We analyzed prospectively collected data of patients admitted to the Cambridge Neuroscience critical care unit who had continuous recordings of arterial blood pressure, ICP, and cerebral blood flow velocities (FVs) using TCD. PI was calculated (FVsys − FVdia)/FVmean over each recording session. Statistical analysis was performed using Spearman rank correlation, receiver-operator-characteristics methods, and modeling of a nonlinear PI-ICP/CPP graph.

RESULTS:

Seven hundred sixty-two recorded daily sessions from 290 patients were analyzed with a total recording time of 499.9 hours. The correlation between PI and ICP was 0.31 (P &lt; .001) and for PI and CPP -0.41 (P &lt; .001). The 95% prediction interval of ICP values for a given PI was more than ±15 mm Hg and for CPP more than ±25 mm Hg. The diagnostic value of PI to assess ICP area under the curve ranged from 0.62 (ICP &gt;15 mm Hg) to 0.74 (ICP &gt;35 mm Hg). For CPP, the area under the curve ranged from 0.68 (CPP &lt;70 mm Hg) to 0.81 (CPP &lt;50 mm Hg). Probability charts for elevated ICP/lowered CPP depending on PI were created.

CONCLUSION:

Overall, the value of TCD-PI to assess ICP and CPP noninvasively is very limited. However, extreme values of PI can still potentially be used in support of a decision for invasive ICP monitoring.

Intracranial Pressure Monitoring: Invasive versus Non-Invasive Methods-A Review

Monitoring of intracranial pressure (ICP) has been used for decades in the fields of neurosurgery and neurology. There are multiple techniques: invasive as well as noninvasive. This paper aims to provide an overview of the advantages and disadvantages of the most common and well-known methods as well as assess whether noninvasive techniques (transcranial Doppler, tympanic membrane displacement, optic nerve sheath diameter, CT scan/MRI and fundoscopy) can be used as reliable alternatives to the invasive techniques (ventriculostomy and microtransducers). Ventriculostomy is considered the gold standard in terms of accurate measurement of pressure, although microtransducers generally are just as accurate. Both invasive techniques are associated with a minor risk of complications such as hemorrhage and infection. Furthermore, zero drift is a problem with selected microtransducers. The non-invasive techniques are without the invasive methods' risk of complication, but fail to measure ICP accurately enough to be used as routine alternatives to invasive measurement. We conclude that invasive measurement is currently the only option for accurate measurement of ICP.

Contemporary view on neuromonitoring following severe traumatic brain injury

Evolving brain damage following traumatic brain injury (TBI) is strongly influenced by complex pathophysiologic cascades including local as well as systemic influences. To successfully prevent secondary progression of the primary damage we must actively search and identify secondary insults e.g. hypoxia, hypotension, uncontrolled hyperventilation, anemia, and hypoglycemia, which are known to aggravate existing brain damage. For this, we must rely on specific cerebral monitoring. Only then can we unmask changes which otherwise would remain hidden, and prevent adequate intensive care treatment. Apart from intracranial pressure (ICP) and calculated cerebral perfusion pressure (CPP), extended neuromonitoring (SjvO₂, ptiO₂, microdialysis, transcranial Doppler sonography, electrocorticography) also allows us to define individual pathologic ICP and CPP levels. This, in turn, will support our therapeutic decision-making and also allow a more individualized and flexible treatment concept for each patient. For this, however, we need to learn to integrate several dimensions with their own possible treatment options into a complete picture. The present review summarizes the current understanding of extended neuromonitoring to guide therapeutic interventions with the aim of improving intensive care treatment following severe TBI, which is the basis for ameliorated outcome.

Intracranial pressure: why we monitor it, how to monitor it, what to do with the number and what's the future?

PURPOSE OF REVIEW

The review touches upon the current physiopathological concepts relating to the field of intracranial pressure (ICP) monitoring and offers an up-to-date overview of the ICP monitoring technologies and of the signal-analysis techniques relevant to clinical practice.

RECENT FINDINGS

Improved ICP probes, antibiotic-impregnated ventricular catheters and multimodality, computerized systems allow ICP monitoring and individualized optimization of brain physiology. Noninvasive technologies for ICP and cerebral perfusion pressure assessment are being tested in the clinical arena. Computerized morphological analysis of the ICP pulse-waveform can provide an indicator of global cerebral perfusion.

SUMMARY

Current recommendations for the management of traumatic brain injury indicate ICP monitoring in patients who remain comatose after resuscitation if the admission computed tomography scan reveals intracranial abnormalities such as haematomas, contusions and cerebral oedema. The most reliable methods of ICP monitoring are ventricular catheters and intraparenchymal systems. A growing number of these devices are being safely placed by neurointensivists. The consensus is to treat ICP exceeding the 20 mmHg threshold, and to target cerebral perfusion pressure between 50 and 70 mmHg. Recent evidence suggests that such thresholds should be optimized based on multimodality monitoring and individual brain physiology. Noninvasive ICP estimation using transcranial Doppler can have a role as a screening tool in patients with low to intermediate risk of developing intracranial hypertension. However, the technology remains insufficiently accurate and too cumbersome for continuous ICP monitoring.