Guidelines for the management of severe traumatic brain injury. VII. Intracranial pressure monitoring technology

Human neuronal changes in brain edema and increased intracranial pressure

Functional and molecular changes associated with pathophysiological conditions are relatively easily detected based on tissue samples collected from patients. Population specific cellular responses to disease might remain undiscovered in samples taken from organs formed by a multitude of cell types. This is particularly apparent in the human cerebral cortex composed of a yet undefined number of neuron types with a potentially different involvement in disease processes. We combined cellular electrophysiology, anatomy and single cell digital PCR in human neurons identified in situ for the first time to assess mRNA expression and corresponding functional changes in response to edema and increased intracranial pressure. In single pyramidal cells, mRNA copy numbers of AQP1, AQP3, HMOX1, KCNN4, SCN3B and SOD2 increased, while CACNA1B, CRH decreased in edema. In addition, single pyramidal cells increased the copy number of AQP1, HTR5A and KCNS1 mRNAs in response to increased intracranial pressure. In contrast to pyramidal cells, AQP1, HMOX1and KCNN4 remained unchanged in single cell digital PCR performed on fast spiking cells in edema. Corroborating single cell digital PCR results, pharmacological and immunohistochemical results also suggested the presence of KCNN4 encoding the α-subunit of KCa3.1 channels in edema on pyramidal cells, but not on interneurons. We measured the frequency of spontaneous EPSPs on pyramidal cells in both pathophysiological conditions and on fast spiking interneurons in edema and found a significant decrease in each case, which was accompanied by an increase in input resistances on both cell types and by a drop in dendritic spine density on pyramidal cells consistent with a loss of excitatory synapses. Our results identify anatomical and/or physiological changes in human pyramidal and fast spiking cells in edema and increased intracranial pressure revealing cell type specific quantitative changes in gene expression. Some of the edema/increased intracranial pressure modulated and single human pyramidal cell verified gene products identified here might be considered as novel pharmacological targets in cell type specific neuroprotection.

Management of Intracranial Pressure

PURPOSE OF REVIEW

Intracranial pressure (ICP) can be elevated in traumatic brain injury, large artery acute ischemic stroke, intracranial hemorrhage, intracranial neoplasms, and diffuse cerebral disorders such as meningitis, encephalitis, and acute hepatic failure. Raised ICP is also known as intracranial hypertension and is defined as a sustained ICP of greater than 20 mm Hg.

RECENT FINDINGS

ICP must be measured through an invasive brain catheter, typically an external ventricular catheter that can drain CSF and measure ICP, or through an intraparenchymal ICP probe. Proper recognition of the clinical signs of elevated ICP is essential for timely diagnosis and treatment to prevent cerebral hypoperfusion and possible brain death. Clinical signs of elevated ICP include headache, papilledema, nausea, and vomiting in the early phases, followed by stupor and coma, pupillary changes, hemiparesis or quadriparesis, posturing and respiratory abnormalities, and eventually cardiopulmonary arrest.

SUMMARY

Management of elevated ICP is, in part, dependent on the underlying cause. Medical options for treating elevated ICP include head of bed elevation, IV mannitol, hypertonic saline, transient hyperventilation, barbiturates, and, if ICP remains refractory, sedation, endotracheal intubation, mechanical ventilation, and neuromuscular paralysis. Surgical options include CSF drainage if hydrocephalus is present and decompression of a surgical lesion, such as an intracranial hematoma/large infarct or tumor, if the patient's condition is deemed salvageable. Future research should continue investigating medical and surgical options for the treatment of raised ICP, such as hypothermia, drugs that reduce cerebral edema, and operations aimed at reducing intracranial mass effect.

Intraventricular intracranial pressure monitoring improves the outcome of older adults with severe traumatic brain injury: an observational, prospective study

BACKGROUND

Intracranial pressure (ICP) monitoring is widely used in the management of patients with severe traumatic brain injury (TBI). However, there is limited evidence about the efficacy of ICP monitoring in older subjects (aged ≥65 years). This study evaluated the effect of intraventricular ICP monitoring on the outcome of older adults suffering from a severe TBI.

METHODS

This prospective, observational study included 166 older TBI patients (aged ≥65 years) with Glasgow Coma scale (GCS) scores lower than 9 at admission. The study cohort was divided into two groups, intraventricular ICP monitoring and non-ICP monitoring. The primary outcome was in-hospital mortality. The secondary outcomes included the Glasgow Outcome Scale (GOS) score 6 months after injury, the ICU and total hospital lengths of stay, and mechanical ventilation days.

RESULTS

There were 80 patients in the intraventricular ICP monitoring group and 86 patients in non-ICP monitoring group. There was no statistical difference between groups in demographics and severity of head injury. Patients treated with intraventricular ICP monitoring had lower in-hospital mortality (33.8 % vs 51.2 %, P < 0.05), a higher 6-month GOS score (3.0 ± 1.4 vs 2.5 ± 1.2 P < 0.05), and a lower dosage (514 ± 246 g vs 840 ± 323 g, P < 0.0001) and shorter duration (7.2 ± 3.6 days vs 8.4 ± 4.3 days, P < 0.01) of mannitol use. However, the ICU length of stay (14.3 ± 6.4 days vs 11.6 ± 5.8 days, P < 0.01) and mechanical ventilation days (6.7 ± 3.5 days vs 5.6 ± 2.4 days, P < 0.05) were longer in the ICP monitoring group. The total length of hospital stay did not differ between the two groups (28.5 ± 12.1 days vs 26.1 ± 13.5 days, P = 0.23).

CONCLUSIONS

Intraventricular ICP monitoring may have beneficial effects on the decreased in-hospital mortality and improved 6-month outcome of older patients with severe TBI. However, given that this was an observational study conducted in a single institution, further well-designed randomized control trials are needed to evaluate the effect of intraventricular ICP monitoring on the outcome of older severe TBI patients.

Colistin and tigecycline for management of external ventricular device-related ventriculitis due to multidrug-resistant Acinetobacter baumannii

Acinetobacter baumannii is an important cause of nosocomial ventriculitis associated with external ventricular device (EVD). It is frequently multidrug resistant (MDR), carries a poor outcome, and is difficult to treat. We report a case of MDR Acinetobacter ventriculitis treated with intravenous and intraventricular colistin together with intravenous tigecycline. The patient developed nephrotoxicity and poor neurological outcome despite microbiological cure. Careful implementation of bundle of measures to minimize EVD-associated ventriculitis is valuable.

Early Experience of Automated Intraventricular Type Intracranial Pressure Monitoring (LiquoGuard®) for Severe Traumatic Brain Injury Patients

Objective

The LiquoGuard® system is a new ventricular-type monitoring device that facilitates intracranial pressure (ICP)-controlled or volume-controlled drainage of cerebrospinal fluid (CSF). The purpose of this study is to report the authors' experience with the LiquoGuard® ICP monitoring system, as well as the clinical safety, usefulness, and limitations of this device in the management of patients with traumatic brain injury (TBI).

Methods

Intraventricular ICP monitoring was performed on 10 patients with TBI using the LiquoGuard® monitoring system. ICP measurements, volume of drained CSF, and clinical outcomes were analyzed and discussed.

Results

ICP monitoring was performed on 10 patients for a mean duration of 6.9 days. With a mean 82,718 records per patient, the mean initial ICP was 16.4 mm Hg and the average ICP across the total duration of monitoring was 15.5 mm Hg. The mean volume of drained CSF was 29.2 cc/day, with no CSF drained in 4 patients. Seven of 10 patients showed 1 or 2 episodes of abnormal ICP measurements. No patient exhibited complications associated with ICP monitoring.

Conclusion

The LiquoGuard® system is a versatile tool in the management of TBI patients. Its use is both reliable and feasible for ICP monitoring and therapeutic drainage of CSF. However, episodes of abnormal ICP measurements were frequently observed in patients with slit ventricles, and further study may be needed to overcome this issue.

23.4% Saline Decreases Brain Tissue Volume in Severe Hepatic Encephalopathy as Assessed by a Quantitative CT Marker

OBJECTIVE

Cerebral edema is common in severe hepatic encephalopathy and may be life threatening. Bolus 23.4% hypertonic saline improves surveillance neuromonitoring scores, although its mechanism of action is not clearly established. We investigated the hypothesis that bolus hypertonic saline decreases cerebral edema in severe hepatic encephalopathy utilizing a quantitative technique to measure brain and cerebrospinal fluid volume changes.

DESIGN

Retrospective analysis of serial CT scans, and clinical data for a case-control series were performed.

SETTING

ICUs of a tertiary care hospital.

PATIENTS

Patients with severe hepatic encephalopathy treated with 23.4% hypertonic saline and control patients who did not receive 23.4% hypertonic saline.

INTERVENTIONS

23.4% hypertonic saline bolus administration.

MEASUREMENTS AND MAIN RESULTS

We used clinically obtained CT scans to measure volumes of the ventricles, intracranial cerebrospinal fluid, and brain using a previously validated semiautomated technique (Analyze Direct, Overland Park, KS). Volumes before and after 23.4% hypertonic saline were compared with Wilcoxon signed rank test. Associations among total cerebrospinal fluid volume, ventricular volume, serum sodium, and Glasgow Coma Scale scores were assessed using Spearman rank correlation test. Eleven patients with 18 administrations of 23.4% hypertonic saline met inclusion criteria. Total cerebrospinal fluid (median, 47.6 mL [35.1-69.4 mL] to 61.9 mL [47.7-87.0 mL]; p < 0.001) and ventricular volumes (median, 8.0 mL [6.9-9.5 mL] to 9.2 mL [7.8-11.9 mL]; p = 0.002) increased and Glasgow Coma Scale scores improved (median, 4 [3-6] to 7 [6-9]; p = 0.008) after 23.4% hypertonic saline. In contrast, total cerebrospinal fluid and ventricular volumes decreased in untreated control patients. Serum sodium increase was associated with increase in total cerebrospinal fluid volume (r = 0.83, p < 0.001), and change in total cerebrospinal fluid volume was associated with ventricular volume change (r = 0.86; p < 0.001).

CONCLUSIONS

Total cerebrospinal fluid and ventricular volumes increased after 23.4% hypertonic saline, consistent with a reduction in brain tissue volume. Total cerebrospinal fluid and ventricular volume change may be useful quantitative measures to assess cerebral edema in severe hepatic encephalopathy.

Appraisal of the Quality of Neurosurgery Clinical Practice Guidelines

OBJECTIVE

The rate of neurosurgery guidelines publications was compared over time with all other specialties. Neurosurgical guidelines and quality of supporting evidence were then analyzed and compared by subspecialty.

METHODS

The authors first performed a PubMed search for "Neurosurgery" and "Guidelines." This was then compared against searches performed for each specialty of the American Board of Medical Specialties. The second analysis was an inventory of all neurosurgery guidelines published by the Agency for Healthcare Research and Quality Guidelines clearinghouse. All Class I evidence and Level 1 recommendations were compared for different subspecialty topics.

RESULTS

When examined from 1970-2010, the rate of increase in publication of neurosurgery guidelines was about one third of all specialties combined (P < 0.0001). However, when only looking at the past 5 years the publication rate of neurosurgery guidelines has converged upon that for all specialties. The second analysis identified 49 published guidelines for assessment. There were 2733 studies cited as supporting evidence, with only 243 of these papers considered the highest class of evidence (8.9%). These papers were used to generate 697 recommendations, of which 170 (24.4%) were considered "Level 1" recommendations.

CONCLUSION

Although initially lagging, the publication of neurosurgical guidelines has recently increased at a rate comparable with that of other specialties. However, the quality of the evidence cited consists of a relatively low number of high-quality studies from which guidelines are created. Wider implications of this must be considered when defining and measuring quality of clinical performance in neurosurgery.

Normobaric hyperoxia is associated with increased cerebral excitotoxicity after severe traumatic brain injury

BACKGROUND

Normobaric oxygen therapy is frequently applied in neurocritical care, however, whether supplemental FiO2 has beneficial cerebral effects is still controversial. We examined in patients with severe traumatic brain injury (TBI) the effect of incremental FiO2 on cerebral excitotoxicity, quantified by cerebral microdialysis (CMD) glutamate.

METHODS

This was a retrospective analysis of a database of severe TBI patients monitored with CMD and brain tissue oxygen (PbtO2). The relationship of FiO2--categorized into four separate ranges (<40, 41-60, 61-80, and >80 %)--with CMD glutamate was examined using ANOVA with Tukey's post hoc test.

RESULTS

A total of 1,130 CMD samples from 36 patients--monitored for a median of 4 days--were examined. After adjusting for brain (PbtO2, intracranial pressure, cerebral perfusion pressure, lactate/pyruvate ratio, Marshall CT score) and systemic (PaCO2, PaO2, hemoglobin, APACHE score) covariates, high FiO2 was associated with a progressive increase in CMD glutamate [8.8 (95 % confidence interval 7.4-10.2) µmol/L at FiO2 < 40 % vs. 12.8 (10.9-14.7) µmol/L at 41-60 % FiO2, 19.3 (15.6-23) µmol/L at 61-80 % FiO2, and 22.6 (16.7-28.5) µmol/L at FiO2 > 80 %; multivariate-adjusted p < 0.05]. The threshold of FiO2-related increase in CMD glutamate was lower for samples with normal versus low PbtO2 < 20 mmHg (FiO2 > 40 % vs. FiO2 > 60 %). Hyperoxia (PaO2 > 150 mmHg) was also associated with increased CMD glutamate (adjusted p < 0.001).

CONCLUSIONS

Incremental normobaric FiO2 levels were associated with increased cerebral excitotoxicity in patients with severe TBI, independent from PbtO2 and other important cerebral and systemic determinants. These data suggest that supra-normal oxygen may aggravate secondary brain damage after severe TBI.

Accuracy of intracranial pressure monitoring: systematic review and meta-analysis

Introduction

Intracranial pressure (ICP) measurement is used to tailor interventions and to assist in formulating the prognosis for traumatic brain injury patients. Accurate data are therefore essential. The aim of this study was to verify the accuracy of ICP monitoring systems on the basis of a literature review.

Methods

A PubMed search was conducted from 1982 to 2014, plus additional references from the selected papers. Accuracy was defined as the degree of correspondence between the pressure read by the catheter and a reference “real” ICP measurement. Studies comparing simultaneous readings from at least two catheters were included. Drift was defined as the loss of accuracy over the monitoring period. Meta-analyses of data from the studies were used to estimate the overall mean difference between simultaneous ICP measurements and their variability. Individual studies were weighted using both a fixed and a random effects model.

Results

Of 163 articles screened, 83 compared two intracranial catheters: 64 reported accuracy and 37 drift (some reported both). Of these, 10 and 17, respectively, fulfilled the inclusion criteria for accuracy and zero drift analysis. The combined mean differences between probes were 1.5 mmHg (95 % confidence interval (CI) 0.7–2.3) with the random effects model and 1.6 mmHg (95 % CI 1.3–1.9) with the fixed effects model. The reported mean drift over a long observation period was 0.75 mmHg. No relation was found with the duration of monitoring or differences between various probes.

Conclusions

This study confirms that the average error between ICP measures is clinically negligible. The random effects model, however, indicates that a high percentage of readings may vary over a wide range, with clinical implications both for future comparison studies and for daily care.

Ultrasound measurement of optic nerve diameter and optic nerve sheath diameter in healthy Chinese adults

BACKGROUND

Measurement of optic nerve sheath diameter (ONSD) is a fast and non-invasive method in detecting elevated intracranial pressure. However, the reported normal range of ONSD was inconsistent. The objective of the study was to determine the normal range of ONSD in healthy Chinese adults.

METHODS

Eyeball transverse diameter (ETD), optic nerve diameter (OND), and ONSD were measured by ultrasound examination in healthy adult volunteers. The OND and ONSD were assessed 3 mm behind the globe. The section showing maximal transverse diameter of the eyeball was frozen and the diameter was measured. Each ETD, OND and ONSD was examined twice and the mean value was calculated.

RESULTS

A total of 519 healthy volunteers were included in the study. The median (interquartile range) of ETD, OND and ONSD were 22.3 (21.6 to 23.1) mm, 3.2 (2.9 to 3.4) mm, and 5.1 (4.7 to 5.4) mm, respectively. The 95% percentile of ONSD was 5.9 mm. There was no significant difference in ETD, OND or ONSD between male and female, or between left and right eye. ONSD was significantly correlated with OND (r = 0.62, P < 0.001), and the median OND/ONSD ratio (interquartile range) was 0.63 (0.59 to 0.67).

CONCLUSIONS

The median and the 95% percentile of sonographic measurement of ONSD are 5.1 mm and 5.9 mm in healthy Chinese adults. The ONSD is correlated with OND, while independent of gender, age, height, weight and ETD. The median OND/ONSD ratio is 0.63 and this parameter warrants further investigation in patients with brain injury.

Study protocol for the PHANTOM study: prehospital assessment of noninvasive tissue oximetry monitoring

BACKGROUND

Traumatic brain injury is a major cause of mortality and morbidity worldwide. It can be worsened by secondary injury particularly with hypoxia or hypotension. Current prehospital guidelines emphasise regular measurement of peripheral oxygen saturation and blood pressure but there is no monitor in use to provide direct information relating to blood flow or oxygen delivery to the brain tissue. This prospective cohort study will assess the utility of near-infrared spectroscopy monitoring in prehospital medicine in demonstrating injury, pathophysiology and associations with long-term functional outcomes.

METHODS/DESIGN

A prospective cohort study will be conducted in prehospital services where physician/paramedic teams respond rapidly to patients suffering significant traumatic injuries. A study observer accompanying the clinical team will apply non-invasive near-infrared spectroscopy tissue oximetry using a Nonin EQUANOX 7610 Regional Oximetry monitor (TM Nonin Medical, Inc.). This will be applied to patients with traumatic injuries less than 30 minutes old requiring transport. Measurements will be taken at two sites on the forehead and one on the forearm. Clinical teams will be blinded to all monitoring values. Near-infrared spectroscopy tissue oximetry parameters of oxyhaemoglobin%, deoxyhaemoglobin%, total tissue haemoglobin index and regional oxygen saturation will be recorded. Separate statistical analysis relating to time spent with cerebral regional oxygen saturation values < 45% and time series analysis will be performed to demonstrate associations with acute phase outcomes including injuries seen on cerebral imaging, and long-term functional outcomes measured by Glasgow Outcome Score and Extended Glasgow Outcome Score will then be undertaken.

DISCUSSION

This prospective cohort study will demonstrate associations evident from the earliest stages of prehospital treatment between near-infrared spectroscopy tissue oximetry values and both acute and long-term outcomes of patients suffering traumatic injuries. This may provide the basis for future interventional studies utilising near-infrared spectroscopy tissue oximetry to guide prehospital trauma care.

TRIAL REGISTRATION

This trial is registered with the Australian and New Zealand Clinical Trials Registry. The registration number is ACTRN12611001124921 .

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.

Brain perfusion and oxygenation

Maintenance of brain perfusion and oxygenation is of paramount importance to patient outcome with various types of brain injuries (traumatic, ischemic, and hemorrhagic). Historically, monitoring of intracranial pressure and cerebral perfusion pressure has been the mainstay of neuromonitoring techniques used at the critical care bedside to monitor brain perfusion and oxygenation. This article describes the bedside neuromonitoring techniques that have emerged for use with these patients in the critical care area. To give the reader an understanding of the functionality of these neuromonitoring techniques, the article first summarizes the physiology of brain perfusion and oxygenation.

Hemorrhagic complications of ventriculostomy: incidence and predictors in patients with intracerebral hemorrhage

Object

Ventriculostomy—the placement of an external ventricular drain (EVD)—is a common procedure performed in patients with acute neurological injury. Although generally considered a low-risk intervention, recent studies have cited higher rates of hemorrhagic complications than those previously reported. The authors sought to determine the rate of postventriculostomy hemorrhage in a cohort of patients with intracerebral hemorrhage (ICH) and to identify predictors of hemorrhagic complications of EVD placement.

Methods

Patients with ICH who underwent EVD placement and had both pre- and postprocedural imaging available for analysis were included in this study. Relevant data were prospectively collected for each patient who satisfied inclusion criteria. Variables with a p < 0.20 on univariate analyses were included in a stepwise logistic regression model to identify predictors of postventriculostomy hemorrhage.

Results

Sixty-nine patients were eligible for this analysis. Postventriculostomy hemorrhage occurred in 31.9% of patients. Among all patients with intraparenchymal hemorrhage, the mean hemorrhage volume was 0.66 ± 1.06 cm3. Stratified according to ventricular catheter diameter, patients treated with smaller-diameter catheters had a significantly greater mean hemorrhage volume than patients treated with larger-diameter catheters (0.84 ± 1.2 cm3 vs 0.14 ± 0.12 cm3, p = 0.049). Postventriculostomy hemorrhage was clinically significant in only 1 patient (1.4%). Overall, postventriculostomy hemorrhage was not associated with functional outcome or mortality at either discharge or 90 days. In the multivariate model, an age > 75 years was the only independent predictor of EVD-associated hemorrhage.

Conclusions

Advanced age is predictive of EVD-related hemorrhage in patients with ICH. While postventriculostomy hemorrhage is common, it appears to be of minor clinical significance in the majority of patients.

Traumatic Brain Injury pathophysiology and treatments: early, intermediate, and late phases post-injury

Traumatic Brain Injury (TBI) affects a large proportion and extensive array of individuals in the population. While precise pathological mechanisms are lacking, the growing base of knowledge concerning TBI has put increased emphasis on its understanding and treatment. Most treatments of TBI are aimed at ameliorating secondary insults arising from the injury; these insults can be characterized with respect to time post-injury, including early, intermediate, and late pathological changes. Early pathological responses are due to energy depletion and cell death secondary to excitotoxicity, the intermediate phase is characterized by neuroinflammation and the late stage by increased susceptibility to seizures and epilepsy. Current treatments of TBI have been tailored to these distinct pathological stages with some overlap. Many prophylactic, pharmacologic, and surgical treatments are used post-TBI to halt the progression of these pathologic reactions. In the present review, we discuss the mechanisms of the pathological hallmarks of TBI and both current and novel treatments which target the respective pathways.

The complications and the position of the Codman MicroSensor™ ICP device: an analysis of 549 patients and 650 Sensors

BACKGROUND

Complications of and insertion depth of the Codman MicroSensor ICP monitoring device (CMS) is not well studied.

OBJECTIVE

To study complications and the insertion depth of the CMS in a clinical setting.

METHODS

We identified all patients who had their intracranial pressure (ICP) monitored using a CMS device between 2002 and 2010. The medical records and post implantation computed tomography (CT) scans were analyzed for occurrence of infection, hemorrhage and insertion depth.

RESULTS

In all, 549 patients were monitored using 650 CMS. Mean monitoring time was 7.0 ± 4.9 days. The mean implantation depth was 21.3 ± 11.1 mm (0-88 mm). In 27 of the patients, a haematoma was identified; 26 of these were less than 1 ml, and one was 8 ml. No clinically significant bleeding was found. There was no statistically significant increase in the number of hemorrhages in presumed coagulopathic patients. The infection rate was 0.6 % and the calculated infection rate per 1,000 catheter days was 0.8.

CONCLUSION

The risk for hemorrhagic and infectious complications when using the CMS for ICP monitoring is low. The depth of insertion varies considerably and should be taken into account if patients are treated with head elevation, since the pressure is measured at the tip of the sensor. To meet the need for ICP monitoring, an intraparenchymal ICP monitoring device should be preferred to the use of an external ventricular drainage (EVD).

Microelectromechanical systems and nephrology: the next frontier in renal replacement technology

Microelectromechanical systems (MEMS) are playing a prominent role in the development of many new and innovative biomedical devices, but they remain a relatively underused technology in nephrology. The future landscape of clinical medicine and research will only see further expansion of MEMS-based technologies in device designs and applications. This enthusiasm stems from the ability to create small-scale device features with high precision in a cost-effective manner. MEMS also offers the possibility to integrate multiple components into a single device. The adoption of MEMS has the potential to revolutionize how nephrologists manage kidney disease by improving the delivery of renal replacement therapies and enhancing the monitoring of physiologic parameters. To introduce nephrologists to MEMS, this review will first define relevant terms and describe the basic processes used to fabricate devices. Next, a survey of MEMS devices being developed for various biomedical applications will be illustrated with current examples. Finally, MEMS technology specific to nephrology will be highlighted and future applications will be examined. The adoption of MEMS offers novel avenues to improve the care of kidney disease patients and assist nephrologists in clinical practice. This review will serve as an introduction for nephrologists to the exciting world of MEMS.

Perioperative management of traumatic brain injury

Traumatic brain injury (TBI) is a major public health problem and the leading cause of death and disability worldwide. Despite the modern diagnosis and treatment, the prognosis for patients with TBI remains poor. While severity of primary injury is the major factor determining the outcomes, the secondary injury caused by physiological insults such as hypotension, hypoxemia, hypercarbia, hypocarbia, hyperglycemia and hypoglycemia, etc. that develop over time after the onset of the initial injury, causes further damage to brain tissue, worsening the outcome in TBI. Perioperative period may be particularly important in the course of TBI management. While surgery and anesthesia may predispose the patients to new onset secondary injuries which may contribute adversely to outcomes, the perioperative period is also an opportunity to detect and correct the undiagnosed pre-existing secondary insults, to prevent against new secondary insults and is a potential window to initiate interventions that may improve outcome of TBI. For this review, extensive Pubmed and Medline search on various aspects of perioperative management of TBI was performed, followed by review of research focusing on intraoperative and perioperative period. While the research focusing specifically on the intraoperative and immediate perioperative TBI management is limited, clinical management continues to be based largely on physiological optimization and recommendations of Brain Trauma Foundation guidelines. This review is focused on the perioperative management of TBI, with particular emphasis on recent developments.

Clinical review: neuromonitoring - an update

Critically ill patients are frequently at risk of neurological dysfunction as a result of primary neurological conditions or secondary insults. Determining which aspects of brain function are affected and how best to manage the neurological dysfunction can often be difficult and is complicated by the limited information that can be gained from clinical examination in such patients and the effects of therapies, notably sedation, on neurological function. Methods to measure and monitor brain function have evolved considerably in recent years and now play an important role in the evaluation and management of patients with brain injury. Importantly, no single technique is ideal for all patients and different variables will need to be monitored in different patients; in many patients, a combination of monitoring techniques will be needed. Although clinical studies support the physiologic feasibility and biologic plausibility of management based on information from various monitors, data supporting this concept from randomized trials are still required.

Perioperative management of adult traumatic brain injury

This article presents an overview of the management of traumatic brain injury (TBI) as relevant to the practicing anesthesiologist. Key concepts surrounding the pathophysiology and anesthetic principles are used to describe potential ways to reduce secondary insults and improve outcomes after TBI.

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.

Brain injury biomarkers may improve the predictive power of the IMPACT outcome calculator

Outcome prediction following severe traumatic brain injury (sTBI) is a widely investigated field of research. A major breakthrough is represented by the IMPACT prognostic calculator based on admission data of more than 8500 patients. A growing body of scientific evidence has shown that clinically meaningful biomarkers, including glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase-L1 (UCH-L1), and αII-spectrin breakdown product (SBDP145), could also contribute to outcome prediction. The present study was initiated to assess whether the addition of biomarkers to the IMPACT prognostic calculator could improve its predictive power. Forty-five sTBI patients (GCS score≤8) from four different sites were investigated. We utilized the core model of the IMPACT calculator (age, GCS motor score, and reaction of pupils), and measured the level of GFAP, UCH-L1, and SBDP145 in serum and cerebrospinal fluid (CSF). The forecast and actual 6-month outcomes were compared by logistic regression analysis. The results of the core model itself, as well as serum values of GFAP and CSF levels of SBDP145, showed a significant correlation with the 6-month mortality using a univariate analysis. In the core model, the Nagelkerke R(2) value was 0.214. With multivariate analysis we were able to increase this predictive power with one additional biomarker (GFAP in CSF) to R(2)=0.476, while the application of three biomarker levels (GFAP in CSF, GFAP in serum, and SBDP145 in CSF) increased the Nagelkerke R(2) to 0.700. Our preliminary results underline the importance of biomarkers in outcome prediction, and encourage further investigation to expand the predictive power of contemporary outcome calculators and prognostic models in TBI.

Is aggressive treatment of traumatic brain injury cost-effective?

OBJECT

The object of this study was to determine whether aggressive treatment of severe traumatic brain injury (TBI), including invasive intracranial monitoring and decompressive craniectomy, is cost-effective.

METHODS

A decision-analytical model was created to compare costs, outcomes, and cost-effectiveness of 3 strategies for treating a patient with severe TBI. The aggressive-care approach is compared with "routine care," in which Brain Trauma Foundation guidelines are not followed. A "comfort care" category, in which a single day in the ICU is followed by routine floor care, is included for comparison only. Probabilities of each treatment resulting in various Glasgow Outcome Scale (GOS) scores were obtained from the literature. The GOS scores were converted to quality-adjusted life years (QALYs), based on expected longevity and calculated quality of life associated with each GOS category. Estimated direct (acute and long-term medical care) and indirect (loss of productivity) costs were calculated from the perspective of society. Sensitivity analyses employed a 2D Monte Carlo simulation of 1000 trials, each with 1000 patients. The model was also used to estimate these values for patients 40, 60, and 80 years of age.

RESULTS

For the average 20-year-old, aggressive care yields 11.7 (± 1.6 [SD]) QALYs, compared with routine care (10.0 ± 1.5 QALYs). This difference is highly significant (p < 0.0001). Although the differences in effectiveness between the 2 strategies diminish with advancing age, aggressive care remains significantly better at all ages. When all costs are considered, aggressive care is also significantly less costly than routine care ($1,264,000 ± $118,000 vs $1,361,000 ± $107,000) for the average 20-year-old. Aggressive care remains significantly less costly until age 80, at which age it costs more than routine care. However, even in the 80-year-old, aggressive care is likely the more cost-effective approach. Comfort care is associated with poorer outcomes at all ages and with higher costs for all groups except 80-year-olds.

CONCLUSIONS

When all the costs of severe TBI are considered, aggressive treatment is a cost-effective option, even for older patients. Comfort care for severe TBI is associated with poor outcomes and high costs, and should be reserved for situations in which aggressive approaches have failed or testing suggests such treatment is futile.

Bench-to-bedside and bedside back to the bench; coordinating clinical and experimental traumatic brain injury studies

Traumatic brain injury (TBI) is one of the leading cause of death and long-term disability in virtually every country. Advances in neurointensive care have resulted in steadily decreasing morbidity, but the number of individuals with severe long-term disability have not changed significantly and the number of moderate disability has shown steady increase over the last 3 decades. Despite years of intensive preclinical research – and millions spent – there are virtually no drugs specifically developed to mitigate the consequences of TBI. Here we discuss some of the existing gaps between clinical and experimental TBI studies that may have contributed to the current status. We do this hoping that clinical, basic, and translational scientists will design and coordinate studies in order to achieve maximum benefits for TBI patients. In conclusion, we suggest to: (1) Develop consensus-based guidelines for experimental TBI research, similar to “best practices” in the clinic; (2) Generate a consensus-based template for clinical data collection and deposition as well as for experimental TBI data collection and deposition; (3) Use a systems biology approach and create a database for integrating existing data from basic and clinical research.

US estimates of hospitalized children with severe traumatic brain injury: implications for clinical trials

OBJECTIVES

To estimate sample sizes available for clinical trials of severe traumatic brain injury (TBI) in children, we described the patient demographics and hospital characteristics associated with children hospitalized with severe TBI in the United States.

METHODS

We analyzed the 2006 Kids' Inpatient Database. Severe TBI hospitalizations were defined as children discharged with TBI who required mechanical ventilation or intubation. Types of high-volume severe TBI hospitals were categorized based on the numbers of discharged patients with severe TBI in 2006. National estimates of demographics and hospital characteristics were calculated for pediatric severe TBI. Simulation analyses were performed to assess the potential number of severe TBI cases from randomly selected hospitals for inclusion in future clinical trials.

RESULTS

The majority of children with severe TBI were discharged from either a children's unit in general hospitals (41%) or a nonchildren's hospital (34%). Less than 5% of all hospitals were high-volume TBI hospitals, which discharged >78% of severe TBI cases and were more likely to be a children's unit in a general hospital or a children's hospital. Simulation analyses indicate that there is a saturation point after which the benefit of adding additional recruitment sites decreases significantly.

CONCLUSIONS

Children with severe TBI are infrequent at any one hospital in the United States, and few hospitals treat large numbers of children with severe TBI. To effectively plan trials of therapies for severe TBI, much attention has to be paid to selecting the right types of centers to maximize enrollment efficiency.

Human umbilical cord blood mesenchymal stem cells protect mice brain after trauma

OBJECTIVE

To investigate whether human umbilical cord blood mesenchymal stem cells, a novel source of progenitors with multilineage potential: 1) decrease traumatic brain injury sequelae and restore brain function; 2) are able to survive and home to the lesioned region; and 3) induce relevant changes in the environment in which they are infused.

DESIGN

Prospective experimental study.

SETTING

Research laboratory.

SUBJECTS

Male C57Bl/6 mice.

INTERVENTIONS

Mice were subjected to controlled cortical impact/sham brain injury. At 24 hrs postinjury, human umbilical cord blood mesenchymal stem cells (150,000/5 μL) or phosphate-buffered saline (control group) were infused intracerebroventricularly contralateral to the injured side. Immunosuppression was achieved by cyclosporine A (10 mg/kg intraperitoneally).

MEASUREMENTS AND MAIN RESULTS

After controlled cortical impact, human umbilical cord blood mesenchymal stem cell transplantation induced an early and long-lasting improvement in sensorimotor functions assessed by neuroscore and beam walk tests. One month postinjury, human umbilical cord blood mesenchymal stem cell mice showed attenuated learning dysfunction at the Morris water maze and reduced contusion volume compared with controls. Hoechst positive human umbilical cord blood mesenchymal stem cells homed to lesioned tissue as early as 1 wk after injury in 67% of mice and survived in the injured brain up to 5 wks. By 3 days postinjury, cell infusion significantly increased brain-derived neurotrophic factor concentration into the lesioned tissue, restoring its expression close to the levels observed in sham operated mice. By 7 days postinjury, controlled cortical impact human umbilical cord blood mesenchymal stem cell mice showed a nonphagocytic activation of microglia/macrophages as shown by a selective rise (260%) in CD11b staining (a marker of microglia/macrophage activation/recruitment) associated with a decrease (58%) in CD68 (a marker of active phagocytosis). Thirty-five days postinjury, controlled cortical impact human umbilical cord blood mesenchymal stem cell mice showed a decrease of glial fibrillary acidic protein positivity in the scar region compared with control mice.

CONCLUSIONS

These findings indicate that human umbilical cord blood mesenchymal stem cells stimulate the injured brain and evoke trophic events, microglia/macrophage phenotypical switch, and glial scar inhibitory effects that remodel the brain and lead to significant improvement of neurologic outcome.

Brain oxygen tension monitoring following penetrating ballistic-like brain injury in rats

While brain oxygen tension (PbtO(2)) monitoring is an important parameter for evaluating injury severity and therapeutic efficiency in severe traumatic brain injury (TBI) patients, many factors affect the monitoring. The goal of this study was to identify the effects of FiO(2) (fraction of inspired oxygen) on PbtO(2) in uninjured anesthetized rats and measure the changes in PbtO(2) following penetrating ballistic-like brain injury (PBBI). Continuous PbtO(2) monitoring in uninjured anesthetized rats showed that PbtO(2) response was positively correlated with FiO(2) (0.21-0.35) but PbtO(2) remained stable when FiO(2) was maintained at ∼0.26. Importantly, although increasing FiO(2) from 0.21 to 0.35 improved P(a)O(2), it concomitantly reduced pH levels and elevated P(a)CO(2) values out of the normal range. However, when the FiO(2) was maintained between 0.26 and 0.30, the pH and P(a)O(2) levels remained within the normal or clinically acceptable range. In PBBI rats, PbtO(2) was significantly reduced by ∼40% (16.9 ± 1.2 mm Hg) in the peri-lesional region immediately following unilateral, frontal 10% PBBI compared to sham rats (28.6 ± 1.7 mm Hg; mean ± SEM, p<0.05) and the PBBI-induced reductions in PbtO(2) were sustained for at least 150 min post-PBBI. Collectively, these results demonstrate that FiO(2) affects PbtO(2) and that PBBI produces acute and sustained hypoxia in the peri-lesional region of the brain injury. This study provides important information for the management of PbtO(2) monitoring in this brain injury model and may offer insight for therapeutic strategies targeted to improve the hypoxia/ischemia state in the penetrating-type brain injury.

Managing malignant cerebral infarction

OPINION STATEMENT

Managing patients with malignant cerebral infarction remains one of the foremost challenges in medicine. These patients are at high risk for progressive neurologic deterioration and death due to malignant cerebral edema, and they are best cared for in the intensive care unit of a comprehensive stroke center. Careful initial assessment of neurologic function and of findings on MRI, coupled with frequent reassessment of clinical and radiologic findings using CT or MRI are mandatory to promote the prompt initiation of treatments that will ensure the best outcome in these patients. Significant deterioration in either neurologic function or radiologic findings or both demand timely treatment using the best medical management, which may include osmotherapy (mannitol or hypertonic saline), endotracheal intubation, and mechanical ventilation. Under appropriate circumstances, decompressive craniectomy may be warranted to improve outcome or to prevent death.

Intracranial monitoring in traumatic brain injury

PURPOSE OF REVIEW

This review focuses on the role of various intracranial monitoring technologies in the diagnosis and therapy of traumatic brain injury injury.

RECENT FINDINGS

There exist many controversial points as to the utility of different intracranial monitoring with regard to improvement of outcomes from severe traumatic brain injury. Most recent studies are confirming that the use of multiple modalities in the neurological ICU setting may offer promising results.

SUMMARY

Increased adherence to guideline-based and protocol-driven neurointensive care utilizing multimodality in monitoring technology for patients with severe traumatic brain injury is likely to give clinicians increased insight into the elusive mechanisms underlying the complex pathophysiology of this disease process and may further improve outcomes in this patient population.

In vivo accuracy of two intraparenchymal intracranial pressure monitors

PURPOSE

To evaluate the in vivo accuracy of the new Pressio(®) device for intraparenchymal monitoring of intracranial pressure (ICP) versus the Codman(®) device and intraventricular measurement external ventricular drainage (EVD).

METHODS

Data were collected retrospectively for 30 consecutive patients admitted into a 25-bed neurosurgical intensive care unit of a university hospital between January and December 2009. Patients received both intraventricular and intraparenchymal ICP monitoring with Pressio(®) (n = 15) or Codman(®) (n = 15).

RESULTS

We obtained 3,089 data points from the 30 patients. Mean difference between intraparenchymal and EVD pressure (bias) was -0.6 mmHg, and limits of agreement (1.96 SD of the bias) were -8.1 to 6.9 mmHg with Pressio(®) and 0.3 mmHg with limits of agreement of -6.7 to 7.1 mmHg with Codman(®) (NS). The temporal difference was -0.7 ± 1.6 mmHg/100 h of monitoring with Pressio(®) and 0.1 ± 1.6 mmHg/100 h of monitoring with Codman(®) over the study period (NS).

CONCLUSIONS

Intraparenchymal pressure measured with both transducers approximates intraventricular cerebrospinal fluid pressure with an accuracy of ±7 mmHg.

Neuromonitoring for Traumatic Brain Injury in Neurosurgical Intensive Care

The primary aim of neuromonitoring in patients with traumatic brain injury is early detection of secondary brain insults so that timely interventions can be instituted to prevent or treat secondary brain injury. Intracranial pressure monitoring has been a stalwart in neuromonitoring and is still very much the main parameter to guide therapy in brain injured patients in many centres. Cerebral oxygenation is also established as an important parameter for monitoring: global cerebral oxygenation is reliably measured using jugular venous oxygen saturation while brain tissue oxygen tension measurement allows focal brain oxygenation to be monitored. Near-infrared spectroscopy allows a non-invasive option for monitoring of regional cerebral oxygenation. Cerebral microdialysis makes focal measurements of markers of cellular metabolism and cellular injury and death possible, and it is in transition from being a research tool to being an important clinical tool in neuromonitoring. Multimodal monitoring allows different parameters of brain physiology and function to be monitored and can improve identification and prediction of secondary cerebral insults. Multimodal monitoring can potentially improve outcomes in patients with traumatic brain injury by promoting customised treatment strategies for individual patients in place of the commonplace practice of strict adherence to achieving the same standard physiological targets for every patient.