Hyperosmolar therapy for intracranial hypertension

Cardiac Injury After Traumatic Brain Injury: Clinical Consequences and Management

Traumatic brain injury (TBI) is a significant public health issue because of its increasing incidence and the substantial short-term and long-term burden it imposes. This burden includes high mortality rates, morbidity, and a significant impact on productivity and quality of life for survivors. During the management of TBI, extracranial complications commonly arise during the patient's stay in the intensive care unit. These complications can have an impact on both mortality and the neurological outcome of patients with TBI. Among these extracranial complications, cardiac injury is a relatively frequent occurrence, affecting approximately 25-35% of patients with TBI. The pathophysiology underlying cardiac injury in TBI involves the intricate interplay between the brain and the heart. Acute brain injury triggers a systemic inflammatory response and a surge of catecholamines, leading to the release of neurotransmitters and cytokines. These substances have detrimental effects on the brain and peripheral organs, creating a vicious cycle that exacerbates brain damage and cellular dysfunction. The most common manifestation of cardiac injury in TBI is corrected QT (QTc) prolongation and supraventricular arrhythmias, with a prevalence up to 5 to 10 times higher than in the general adult population. Other forms of cardiac injury, such as regional wall motion alteration, troponin elevation, myocardial stunning, or Takotsubo cardiomyopathy, have also been described. In this context, the use of β-blockers has shown potential benefits by intervening in this maladaptive process. β-blockers can limit the pathological effects on cardiac rhythm, blood circulation, and cerebral metabolism. They may also mitigate metabolic acidosis and potentially contribute to improved cerebral perfusion. However, further clinical studies are needed to elucidate the role of new therapeutic strategies in limiting cardiac dysfunction in patients with severe TBI.

Safety and Effect on Intracranial Pressure of 3% Hypertonic Saline Bolus Via Peripheral Intravenous Catheter for Neurological Emergencies

BACKGROUND

Elevated intracranial pressure (ICP) is a neurological emergency in patients with acute brain injuries. Such a state requires immediate and effective interventions to prevent potential neurological deterioration. Current clinical guidelines recommend hypertonic saline (HTS) and mannitol as first-line therapeutic agents. Notably, HTS is conventionally administered through central venous catheters (CVCs), which may introduce delays in treatment due to the complexities associated with CVC placement. These delays can critically affect patient outcomes, necessitating the exploration of more rapid therapeutic avenues. This study aimed to investigate the safety and effect on ICP of administering rapid boluses of 3% HTS via peripheral intravenous (PIV) catheters.

METHODS

A retrospective cohort study was performed on patients admitted to Sisters of Saint Mary Health Saint Louis University Hospital from March 2019 to September 2022 who received at least one 3% HTS bolus via PIV at a rate of 999 mL/hour for neurological emergencies. Outcomes assessed included complications related to 3% HTS bolus and its effect on ICP.

RESULTS

Of 216 3% HTS boluses administered in 124 patients, complications occurred in 8 administrations (3.7%). Pain at the injection site (4 administrations; 1.9%) and thrombophlebitis (3 administrations; 1.4%) were most common. The median ICP reduced by 6 mm Hg after 3% HTS bolus administration (p < 0.001).

CONCLUSIONS

Rapid bolus administration of 3% HTS via PIV catheters presents itself as a relatively safe approach to treat neurological emergencies. Its implementation could provide an invaluable alternative to the traditional CVC-based administration, potentially minimizing CVC-associated complications and expediting life-saving interventions for patients with neurological emergencies, especially in the field and emergency department settings.

Anaesthetic management in a cat undergoing emergency craniotomy for meningioma excision

Case summary

A 15-year-old female spayed domestic shorthair cat underwent an emergency craniotomy to remove an intracranial meningioma causing marked midline shift, caudal transtentorial and foramen magnum herniation. Because intracranial structures are enclosed in the cranium, any volume-occupying lesions might raise intracranial pressure (ICP), compromising cerebral perfusion.

Relevance and novel information

This case report discusses the anaesthetic management of a cat that presented with marked bradycardia and concomitant hypotension. Cushing's reflex (CR) is a well-recognised cardiovascular reflex following sudden ICP increase, and it features an irregular breathing pattern and increased arterial blood pressure with reflex bradycardia. However, CR is reported to have a low sensitivity for the detection of raised ICP in humans with traumatic brain injury. In a previous study reporting seven cats undergoing surgical removal of intracranial meningioma, ICP was measured in four cases and, in these patients, CR was not observed during surgery. Because bradycardia was not secondary to hypertension, in this case, it might have been the result of direct compression of the nucleus of the vagus nerve. Based on the literature search, there is paucity of reports of cardiovascular changes in cats with increased ICP and their perianaesthetic management.

Optimizing Mannitol Use in Managing Increased Intracranial Pressure: A Comprehensive Review of Recent Research and Clinical Experiences

Mannitol, derived from mannose sugar, is crucial in treating patients with elevated intracranial pressure (ICP). Its dehydrating properties at the cellular and tissue levels increase plasma osmotic pressure, which is studied for its potential to reduce ICP through osmotic diuresis. While clinical guidelines support mannitol use in these cases, the best approach for its application continues to be debated. Important aspects needing further investigation include: 1) bolus administration versus continuous infusion, 2) ICP-based dosing versus scheduled bolus, 3) identifying the optimal infusion rate, 4) determining the appropriate dosage, 5) establishing fluid replacement plans for urinary loss, and 6) selecting monitoring techniques and thresholds to assess effectiveness and ensure safety. Due to the lack of adequate high-quality prospective research data, a comprehensive review of recent studies and clinical trials is crucial. This assessment aims to bridge the knowledge gap, improve understanding of effective mannitol use in elevated ICP patients, and provide insights for future research. In conclusion, this review aspires to contribute to the ongoing discourse on mannitol application. By integrating the latest findings, this review will offer valuable insights into the function of mannitol in decreasing ICP, thereby informing better therapeutic approaches and enhancing patient outcomes.

Label-Free Assessment of Mannitol Accumulation Following Osmotic Blood-Brain Barrier Opening Using Chemical Exchange Saturation Transfer Magnetic Resonance Imaging

PURPOSE

Mannitol is a hyperosmolar agent for reducing intracranial pressure and inducing osmotic blood-brain barrier opening (OBBBO). There is a great clinical need for a non-invasive method to optimize the safety of mannitol dosing. The aim of this study was to develop a label-free Chemical Exchange Saturation Transfer (CEST)-based MRI approach for detecting intracranial accumulation of mannitol following OBBBO.

METHODS

In vitro MRI was conducted to measure the CEST properties of D-mannitol of different concentrations and pH. In vivo MRI and MRS measurements were conducted on Sprague-Dawley rats using a Biospec 11.7T horizontal MRI scanner. Rats were catheterized at the internal carotid artery (ICA) and randomly grouped to receive either 1 mL or 3 mL D-mannitol. CEST MR images were acquired before and at 20 min after the infusion.

RESULTS

In vitro MRI showed that mannitol has a strong, broad CEST contrast at around 0.8 ppm with a mM CEST MRI detectability. In vivo studies showed that CEST MRI could effectively detect mannitol in the brain. The low dose mannitol treatment led to OBBBO but no significant mannitol accumulation, whereas the high dose regimen resulted in both OBBBO and mannitol accumulation. The CEST MRI findings were consistent with ¹H-MRS and Gd-enhanced MRI assessments.

CONCLUSION

We demonstrated that CEST MRI can be used for non-invasive, label-free detection of mannitol accumulation in the brain following BBBO treatment. This method may be useful as a rapid imaging tool to optimize the dosing of mannitol-based OBBBO and improve its safety and efficacy.

Cerebral edema after ischemic stroke: Pathophysiology and underlying mechanisms

Ischemic stroke is associated with increasing morbidity and has become the main cause of death and disability worldwide. Cerebral edema is a serious complication arising from ischemic stroke. It causes an increase in intracranial pressure, rapid deterioration of neurological symptoms, and formation of cerebral hernia, and is an important risk factor for adverse outcomes after stroke. To date, the detailed mechanism of cerebral edema after stroke remains unclear. This limits advances in prevention and treatment strategies as well as drug development. This review discusses the classification and pathological characteristics of cerebral edema, the possible relationship of the development of cerebral edema after ischemic stroke with aquaporin 4, the SUR1-TRPM4 channel, matrix metalloproteinase 9, microRNA, cerebral venous reflux, inflammatory reactions, and cerebral ischemia/reperfusion injury. It also summarizes research on new therapeutic drugs for post-stroke cerebral edema. Thus, this review provides a reference for further studies and for clinical treatment of cerebral edema after ischemic stroke.

A teaspoon of sugar and a pinch of salt: Reviewing hyperosmolar therapy

ABSTRACT

The traditional hyperosmolar agents used to treat patients with elevated intracranial pressure are mannitol and hypertonic sodium chloride solution. This article focuses on some of the pros and cons of these treatments for managing cerebral edema.

The Utility of a Point-of-Care Transcranial Doppler Ultrasound Management Algorithm on Outcomes in Pediatric Asphyxial Out-of-Hospital Cardiac Arrest – An Exploratory Investigation

Background

Transcranial Doppler ultrasound is a sensitive, real time tool used for monitoring cerebral blood flow; it could provide additional information for cerebral perfusion in cerebral resuscitation during post cardiac arrest care. The aim of the current study was to evaluate the utility of a point-of-care transcranial Doppler ultrasound management algorithm on outcomes in pediatric asphyxial out-of-hospital cardiac arrest.

Methods

This retrospective cohort study was conducted in two tertiary pediatric intensive care units between January 2013 and June 2018. All children between 1 month and 18 years of age with asphyxial out-of-hospital cardiac arrest and a history of at least 3 min of chest compressions, who were treated with therapeutic hypothermia and survived for 12 h or more after the return of circulation were eligible for inclusion.

Results

Twenty-one patients met the eligibility criteria for the study. Sixteen (76.2%) of the 21 children were male, and the mean age was 2.8 ± 4.1 years. Seven (33.3%) of the children had underlying disorders. The overall 1-month survival rate was 52.4%. Twelve (57.1%) of the children received point-of-care transcranial Doppler ultrasound. The 1-month survival rate was significantly higher (p = 0.03) in the point-of-care transcranial Doppler ultrasound group (9/12, 75%) than in the non-point-of-care transcranial Doppler ultrasound group (2/9, 22.2%).

Conclusions

Point-of-care transcranial Doppler ultrasound group was associated with a significantly better 1-month survival rate compared with no point-of-care transcranial Doppler ultrasound group in pediatric asphyxial out-of-hospital cardiac arrest.

Verticalization for Refractory Intracranial Hypertension: A Case Series

BACKGROUND

Severe intracranial hypertension is strongly associated with mortality. Guidelines recommend medical management involving sedation, hyperosmotic agents, barbiturates, hypothermia, and surgical intervention. When these interventions are maximized or are contraindicated, refractory intracranial hypertension poses risk for herniation and death. We describe a novel intervention of verticalization for treating intracranial hypertension refractory to aggressive medical treatment.

METHODS

This study was a single-center retrospective review of six cases of refractory intracranial hypertension in a tertiary care center. All patients were treated with a standard-of-care algorithm for lowering intracranial pressure (ICP) yet maintained an ICP greater than 20 mmHg. They were then treated with verticalization for at least 24 h. We compared the median ICP, the number of ICP spikes greater than 20 mmHg, and the percentage of ICP values greater than 20 mmHg in the 24 h before verticalization vs. after verticalization. We assessed the use of hyperosmotic therapies and any changes in the mean arterial pressure and cerebral perfusion pressure related with the intervention.

RESULTS

Five patients were admitted with subarachnoid hemorrhage and one with intracerebral hemorrhage. All patients had ICP monitoring by external ventricular drain. The median opening pressure was 30 mmHg (25th-75th interquartile range 22.5-30 mmHg). All patients demonstrated a reduction in ICP after verticalization, with a significant decrease in the median ICP (12 vs. 8 mmHg; p < 0.001), the number of ICP spikes (12 vs. 2; p < 0.01), and the percentage of ICP values greater than 20 mmHg (50% vs. 8.3%; p < 0.01). There was a decrease in total medical interventions after verticalization (79 vs. 41; p = 0.05) and a lower total therapy intensity level score after verticalization. The most common adverse effects included asymptomatic bradycardia (n = 3) and pressure wounds (n = 4).

CONCLUSIONS

Verticalization is an effective noninvasive intervention for lowering ICP in intracranial hypertension that is refractory to aggressive standard management and warrants further study.

Comparison of 1.0 g/kg of 20% mannitol initiated at different time points and effects on brain relaxation in patients with midline shift undergoing supratentorial tumor resection: a randomized controlled trial

OBJECTIVE

Previous studies have suggested the use of 1.0 g/kg of 20% mannitol at the time of skin incision during neurosurgery in order to improve brain relaxation. However, the incidence of brain swelling upon dural opening is still high with this dose. In the present study, the authors sought to determine a better timing for mannitol infusion.

METHODS

One hundred patients with midline shift who were undergoing elective supratentorial tumor resection were randomly assigned to receive early (immediately after anesthesia induction) or routine (at the time of skin incision) administration of 1.0 g/kg body weight of 20% mannitol. The primary outcome was the 4-point brain relaxation score (BRS) immediately after dural opening (1, perfectly relaxed; 2, satisfactorily relaxed; 3, firm brain; and 4, bulging brain). The secondary outcomes included subdural intracranial pressure (ICP) measured immediately before dural opening; serum osmolality and osmole gap (OG) measured immediately before mannitol infusion (T0) and at the time of dural opening (TD); changes in serum electrolytes, lactate, and hemodynamic parameters at T0 and 30, 60, 90, and 120 minutes thereafter; and fluid balance at TD.

RESULTS

The time from the start of mannitol administration to dural opening was significantly longer in the early administration group than in the routine administration group (median 66 [IQR 55-75] vs 40 [IQR 38-45] minutes, p < 0.001). The BRS (score 1/2/3/4, n = 14/26/9/1 vs 3/25/18/4, p = 0.001) was better and the subdural ICP (median 5 [IQR 3-6] vs 7 [IQR 5-10] mm Hg, p < 0.001) was significantly lower in the early administration group than in the routine administration group. Serum osmolality and OG increased significantly at TD compared to levels at T0 in both groups (all p < 0.001). Intergroup comparison showed that serum osmolality and OG at TD were significantly higher in the routine administration group (p < 0.001 and = 0.002, respectively). Patients who had received early administration of mannitol had more urine output (p = 0.001) and less positive fluid balance (p < 0.001) at TD. Hemodynamic parameters, serum lactate concentrations, and incidences of electrolyte disturbances were comparable between the two groups.

CONCLUSIONS

Prolonging the time interval between the start of mannitol infusion and dural incision from approximately 40 to 66 minutes can improve brain relaxation and decrease subdural ICP in elective supratentorial tumor resection.

The Association of Early Electrocardiographic Abnormalities With Brain Injury Severity and Outcome in Severe Traumatic Brain Injury

The aim of this study was to evaluate the frequency of electrocardiographic (ECG) abnormalities in the acute phase of severe traumatic brain injury (TBI) and the association with brain injury severity and outcome. In contrast to neurovascular diseases, sparse information is available on this issue. Data of adult patients with severe TBI admitted to the Intensive Care Unit (ICU) for intracranial pressure monitoring of a level-1 trauma center from 2002 till 2018 were analyzed. Patients with a cardiac history were excluded. An ECG recording was obtained within 24 h after ICU admission. Admission brain computerized tomography (CT)-scans were categorized by Marshall-criteria (diffuse vs. mass lesions) and for location of traumatic lesions. CT-characteristics and maximum Therapy Intensity Level (TILmax) were used as indicators for brain injury severity. We analyzed data of 198 patients, mean (SD) age of 40 ± 19 years, median GCS score 3 [interquartile range (IQR) 3–6], and 105 patients (53%) had thoracic injury. In-hospital mortality was 30%, with sudden death by cardiac arrest in four patients. The incidence of ECG abnormalities was 88% comprising ventricular repolarization disorders (57%) mostly with ST-segment abnormalities, conduction disorders (45%) mostly with QTc-prolongation, and arrhythmias (38%) mostly of supraventricular origin. More cardiac arrhythmias were observed with increased grading of diffuse brain injury (p = 0.042) or in patients treated with hyperosmolar therapy (TILmax) (65%, p = 0.022). No association was found between ECG abnormalities and location of brain lesions nor with thoracic injury. Multivariate analysis with baseline outcome predictors showed that cardiac arrhythmias were not independently associated with in-hospital mortality (p = 0.097). Only hypotension (p = 0.029) and diffuse brain injury (p = 0.017) were associated with in-hospital mortality. In conclusion, a high incidence of ECG abnormalities was observed in patients with severe TBI in the acute phase after injury. No association between ECG abnormalities and location of brain lesions or presence of thoracic injury was present. Cardiac arrhythmias were indicative for brain injury severity but not independently associated with in-hospital mortality. Therefore, our findings likely suggest that ECG abnormalities should be considered as cardiac mimicry representing the secondary effect of traumatic brain injury allowing for a more rationale use of neuroprotective measures.

An overview of management of intracranial hypertension in the intensive care unit

Intracranial hypertension (IH) is a clinical condition commonly encountered in the intensive care unit, which requires immediate treatment. The maintenance of normal intracranial pressure (ICP) and cerebral perfusion pressure in order to prevent secondary brain injury (SBI) is the central focus of management. SBI can be detected through clinical examination and invasive and non-invasive ICP monitoring. Progress in monitoring and understanding the pathophysiological mechanisms of IH allows the implementation of targeted interventions in order to improve the outcome of these patients. Initially, general prophylactic measures such as patient's head elevation, fever control, adequate analgesia and sedation depth should be applied immediately to all patients with suspected IH. Based on specific indications and conditions, surgical resection of mass lesions and cerebrospinal fluid drainage should be considered as an initial treatment for lowering ICP. Hyperosmolar therapy (mannitol or hypertonic saline) represents the cornerstone of medical treatment of acute IH while hyperventilation should be limited to emergency management of life-threatening raised ICP. Therapeutic hypothermia could have a possible benefit on outcome. To control elevated ICP refractory to maximum standard medical and surgical treatment, at first, high-dose barbiturate administration and then decompressive craniectomy as a last step are recommended with unclear and probable benefit on outcomes, respectively. The therapeutic strategy should be based on a staircase approach and be individualized for each patient. Since most therapeutic interventions have an uncertain effect on neurological outcome and mortality, future research should focus on both studying the long-term benefits of current strategies and developing new ones.

Targeting Aquaporin-4 Subcellular Localization to Treat Central Nervous System Edema

Swelling of the brain or spinal cord (CNS edema) affects millions of people every year. All potential pharmacological interventions have failed in clinical trials, meaning that symptom management is the only treatment option. The water channel protein aquaporin-4 (AQP4) is expressed in astrocytes and mediates water flux across the blood-brain and blood-spinal cord barriers. Here we show that AQP4 cell-surface abundance increases in response to hypoxia-induced cell swelling in a calmodulin-dependent manner. Calmodulin directly binds the AQP4 carboxyl terminus, causing a specific conformational change and driving AQP4 cell-surface localization. Inhibition of calmodulin in a rat spinal cord injury model with the licensed drug trifluoperazine inhibited AQP4 localization to the blood-spinal cord barrier, ablated CNS edema, and led to accelerated functional recovery compared with untreated animals. We propose that targeting the mechanism of calmodulin-mediated cell-surface localization of AQP4 is a viable strategy for development of CNS edema therapies.

Cerebral Edema in Traumatic Brain Injury: a Historical Framework for Current Therapy

PURPOSE OF REVIEW

The purposes of this narrative review are to (1) summarize a contemporary view of cerebral edema pathophysiology, (2) present a synopsis of current management strategies in the context of their historical roots (many of which date back multiple centuries), and (3) discuss contributions of key molecular pathways to overlapping edema endophenotypes. This may facilitate identification of important therapeutic targets.

RECENT FINDINGS

Cerebral edema and resultant intracranial hypertension are major contributors to morbidity and mortality following traumatic brain injury. Although Starling forces are physical drivers of edema based on differences in intravascular vs extracellular hydrostatic and oncotic pressures, the molecular pathophysiology underlying cerebral edema is complex and remains incompletely understood. Current management protocols are guided by intracranial pressure measurements, an imperfect proxy for cerebral edema. These include decompressive craniectomy, external ventricular drainage, hyperosmolar therapy, hypothermia, and sedation. Results of contemporary clinical trials assessing these treatments are summarized, with an emphasis on the gap between intermediate measures of edema and meaningful clinical outcomes. This is followed by a brief statement summarizing the most recent guidelines from the Brain Trauma Foundation (4th edition). While many molecular mechanisms and networks contributing to cerebral edema after TBI are still being elucidated, we highlight some promising molecular mechanism-based targets based on recent research including SUR1-TRPM4, NKCC1, AQP4, and AVP1.

SUMMARY

This review outlines the origins of our understanding of cerebral edema, chronicles the history behind many current treatment approaches, and discusses promising molecular mechanism-based targeted treatments.

Mannitol and Hypertonic Saline Reduce Swelling and Modulate Inflammatory Markers in a Rat Model of Intracerebral Hemorrhage

BACKGROUND

Spontaneous intracerebral hemorrhage (ICH) leaves most survivors dependent at follow-up. The importance of promoting M2-like microglial responses is increasingly recognized as a key element to ameliorate brain injury following ICH. The osmotherapeutic agents, mannitol and hypertonic saline (HTS), which are routinely used to reduce intracranial pressure, have been shown to reduce neuroinflammation in experimental ischemic and traumatic brain injury, but anti-inflammatory effects of osmotherapies have not been investigated in ICH.

METHODS

We studied the effects of iso-osmotic mannitol and HTS in rat models of ICH utilizing high-dose and moderate-dose collagenase injections into the basal ganglia, associated with high and low mortality, respectively. We studied the effects of osmotherapies, first given 5 h after ICH induction, and then administered every 12 h thereafter (4 doses total). Immunohistochemistry was used to quantify microglial activation and polarization.

RESULTS

Compared to controls, mannitol and HTS increased plasma osmolarity 1 h after infusion (301 ± 1.5, 315 ± 4.2 and 310 ± 2.0 mOsm/kg, respectively), reduced mortality at 48 h (82, 36 and 53%, respectively), and reduced hemispheric swelling at 48 h (32, 21, and 17%, respectively). In both perihematomal and contralateral tissues, mannitol and HTS reduced activation of microglia/macrophages (abundance and morphology of Iba1 + cells), and in perihematomal tissues, they reduced markers of the microglia/macrophage M1-like phenotype (nuclear p65, TNF, and NOS2), increased markers of the microglia/macrophage M2-like phenotype (arginase, YM1, and pSTAT3), and reduced infiltration of CD45 + cells.

CONCLUSIONS

Repeated dosing of osmotherapeutics at regular intervals may be a useful adjunct to reduce neuroinflammation following ICH.

Acute intracranial hypertension management in metastatic brain tumor: A French national survey

BACKGROUND

Brain metastases occur in 15-30% of cancer patients and their frequency has increased over time. They can cause intracranial hypertension, even in the absence of hydrocephalus. Emergency surgical management of brain metastasis-related intracranial hypertension is not guided by specific recommendations.

OBJECTIVE

We aimed to make a French national survey of emergency management of intracranial hypertension without hydrocephalus in the context of cerebral metastasis.

METHODS

A national online survey of French neurosurgeons from 16 centers was conducted, consisting of three clinical files, with multiple-choice questions on diagnostic and therapeutic management in different emergency situations.

RESULTS

In young patients without any previously known primary cancer, acute intracranial hypertension due to a seemingly metastatic single brain tumor indicated emergency surgery for all those interviewed; 61% aimed at complete resection; brain MRI was mandatory for 74%. When a primary cancer was known, 74% of respondents were more likely to propose surgery if an oncologist confirmed the possibility of adjuvant treatment; 27% were more likely to operate on an emergency basis when resection was scheduled after multi-disciplinary discussion, prior to acute degradation.

CONCLUSION

Currently, there is no consensus on the emergency management of intracranial hypertension in metastatic brain tumor patients. In case of previously known primary cancer, a discussion with the oncology team seems necessary, even in emergency. Decision criteria emerge from our literature review, but require analysis in further studies.

Comparison of electrical impedance tomography and intracranial pressure during dehydration treatment of cerebral edema

Cerebral edema after brain injury can lead to brain damage and death if diagnosis and treatment are delayed. This study investigates the feasibility of employing electrical impedance tomography (EIT) as a non-invasive imaging tool for monitoring the development of cerebral edema, in which impedance imaging of the brain related to brain water content is compared with intracranial pressure (ICP). We enrolled forty patients with cerebral hemorrhage who underwent lateral external ventricular drain with intraventricular ICP and EIT monitoring for 3 h after initiation of dehydration treatment. The average reconstructed impedance value (ARV) calculated from EIT images was compared with ICP. Dehydration effects induced changes in ARV and ICP showed a close negative correlation in all patients, and the mean correlation reached R² = 0.78 ± 0.16 (p < .001). A regression equation (R² = 0.62, p < .001) was formulated from the total of measurement data. The 95% limits of agreement were − 6.13 to 6.13 mmHg. Adaptive clustering and variance analysis of normalized changes in ARV and ICP showed 92.5% similarity and no statistically significant differences (p > .05). Moreover, the sensitivity, specificity and area under the curve of changes in ICP >10 mmHg were 0.65, 0.73 and 0.70 respectively. The findings show that EIT can monitor changes in brain water content associated with cerebral edema, which could provide a real-time and non-invasive imaging tool for early identification of cerebral edema and the evaluation of mannitol dehydration.

•

Changes in brain water content due to cerebral edema alter EIT and ICP simultaneously.

•

EIT has a close negative correlation with ICP during changes in brain water content.

•

Cerebral edema can be early identified by EIT for initiating timely therapy.

•

The efficacy of dehydration can be evaluation by EIT for guiding personalized therapy.

•

The results suggest EIT can monitor cerebral edema real-timely and non-invasively.

A New Vision for Therapeutic Hypothermia in the Era of Targeted Temperature Management: A Speculative Synthesis

Three decades of animal studies have reproducibly shown that hypothermia is profoundly cerebroprotective during or after a central nervous system (CNS) insult. The success of hypothermia in preclinical acute brain injury has not only fostered continued interest in research on the classic secondary injury mechanisms that are prevented or blunted by hypothermia but has also sparked a surge of new interest in elucidating beneficial signaling molecules that are increased by cooling. Ironically, while research into cold-induced neuroprotection is enjoying newfound interest in chronic neurodegenerative disease, conversely, the scope of the utility of therapeutic hypothermia (TH) across the field of acute brain injury is somewhat controversial and remains to be fully defined. This has led to the era of Targeted Temperature Management, which emphasizes a wider range of temperatures (33–36°C) showing benefit in acute brain injury. In this comprehensive review, we focus on our current understandings of the novel neuroprotective mechanisms activated by TH, and discuss the critical importance of developmental age germane to its clinical efficacy. We review emerging data on four cold stress hormones and three cold shock proteins that have generated new interest in hypothermia in the field of CNS injury, to create a framework for new frontiers in TH research. We make the case that further elucidation of novel cold responsive pathways might lead to major breakthroughs in the treatment of acute brain injury, chronic neurological diseases, and have broad potential implications for medicines of the distant future, including scenarios such as the prevention of adverse effects of long-duration spaceflight, among others. Finally, we introduce several new phrases that readily summarize the essence of the major concepts outlined by this review—namely, Ultramild Hypothermia, the “Responsivity of Cold Stress Pathways,” and “Hypothermia in a Syringe.”

Cardiac output changes after osmotic therapy in neurosurgical and neurocritical care patients: a systematic review of the clinical literature

AIM

Osmotherapy constitutes a first-line intervention for intracranial hypertension management. However, hyperosmolar solutes exert various systematic effects, among which their impact on systemic haemodynamics is poorly clarified. This review aims to appraise the clinical evidence of the effect of mannitol and hypertonic saline (HTS) on cardiac performance in neurosurgical and neurocritical care patients.

METHOD

A database search was conducted to identify randomized clinical trials and observational studies reporting HTS or mannitol use in acute brain injury setting. The primary end-points were alterations of cardiac output (CO) and other haemodynamic variables, while the impact of osmotic agents on intracranial pressure, brain relaxation, plasma osmolality, electrolyte levels and urinary output constituted secondary outcomes.

RESULTS

Eight studies, enrolling 182 patients in total, were included. HTS exerted a more profound cardiac output augmentation than mannitol, but no distinct difference between groups occurred. Central venous pressure, stroke volume and stroke volume variation were favourably affected by both osmotic agents, whilst the reported changes in blood pressure were inconclusive. HTS infusion yielded a larger intracranial pressure reduction than mannitol but had an equivalent effect on brain relaxation. Mannitol presented a more potent diuretic effect than HTS. Effect on serum osmolality was alike in both osmotic agents, but contrary to HTS-promoted hypernatraemia, mannitol use induced transient hyponatraemia.

CONCLUSIONS

Mannitol or HTS administration seems to induce an enhancement of cardiac performance; being more prominent after HTS infusion. This effect combined with mannitol-induced enhancement of diuresis and HTS-promoted increase of plasma sodium concentration could partially explain the effects of osmotherapy on cerebral haemodynamics.

Transcranial Doppler Ultrasound Examination in Dogs with Suspected Intracranial Hypertension Caused by Neurologic Diseases

Background

Transcranial Doppler ultrasound examination (TCD) is a rapid, noninvasive technique used to evaluate cerebral blood flow and is useful for the detection of intracranial hypertension in humans. However, the clinical usefulness of TCD in diagnosing intracranial hypertension has not been demonstrated for intracranial diseases in dogs.

Objectives

To determine the association between the TCD variables and intracranial hypertension in dogs with intracranial diseases.

Animals

Fifty client‐owned dogs with neurologic signs.

Methods

Cross‐sectional study. All dogs underwent TCD of the basilar artery under isoflurane anesthesia after magnetic resonance imaging (MRI). Dogs were classified into 3 groups based on MRI findings: no structural diseases (group I), structural disease without MRI evidence of intracranial hypertension (group II), and structural disease with MRI evidence of intracranial hypertension (group III). The TCD vascular resistance variables (resistive index [RI], pulsatility index [PI], and the ratio of systolic to diastolic mean velocity [Sm/Dm]) were measured.

Results

Fifteen, 22, and 13 dogs were classified into groups I, II, and III, respectively. Dogs in group III had significantly higher Sm/Dm (median, 1.78; range, 1.44–2.58) than those in group I (median, 1.63; range, 1.43–1.75) and group II (median, 1.62; range, 1.27–2.10). No significant differences in RI and PI were identified among groups.

Conclusions and Clinical Importance

Our findings suggest that increased Sm/Dm is associated with MRI findings of suspected intracranial hypertension in dogs with intracranial diseases and that TCD could be a useful tool to help to diagnose intracranial hypertension.

Medical Management of the Severe Traumatic Brain Injury Patient

Severe traumatic brain injury (sTBI) is a major contributor to long-term disability and a leading cause of death worldwide. Medical management of the sTBI patient, beginning with prehospital triage, is aimed at preventing secondary brain injury. This review discusses prehospital and emergency department management of sTBI, as well as aspects of TBI management in the intensive care unit where advances have been made in the past decade. Areas of emphasis include intracranial pressure management, neuromonitoring, management of paroxysmal sympathetic hyperactivity, neuroprotective strategies, prognostication, and communication with families about goals of care. Where appropriate, differences between the third and fourth editions of the Brain Trauma Foundation guidelines for the management of severe traumatic brain injury are highlighted.

Increased Intracranial Pressure during Hemodialysis in a Patient with Anoxic Brain Injury

Dialysis disequilibrium syndrome (DDS) is a serious neurological complication of hemodialysis, and patients with acute brain injury are at increased risk. We report a case of DDS leading to intracranial hypertension in a patient with anoxic brain injury and discuss the subsequent dialysis strategy. A 13-year-old girl was admitted after prolonged resuscitation from cardiac arrest. Computed tomography (CT) revealed an inferior vena cava aneurysm and multiple pulmonary emboli as the likely cause. An intracranial pressure (ICP) monitor was inserted, and, on day 3, continuous renal replacement therapy (CRRT) was initiated due to acute kidney injury, during which the patient developed severe intracranial hypertension. CT of the brain showed diffuse cerebral edema. CRRT was discontinued, sedation was increased, and hypertonic saline was administered, upon which ICP normalized. Due to persistent hyperkalemia and overhydration, ultrafiltration and intermittent hemodialysis were performed separately on day 4 with a small dialyzer, low blood and dialysate flow, and high dialysate sodium content. During subsequent treatments, isolated ultrafiltration was well tolerated, whereas hemodialysis was associated with increased ICP necessitating frequent pauses or early cessation of dialysis. In patients at risk of DDS, hemodialysis should be performed with utmost care and continuous monitoring of ICP should be considered.

Dexmedetomidine for Refractory Intracranial Hypertension

Dexmedetomidine (DEX) is a selective α₂ adrenergic agonist that is commonly used for sedation in the intensive care unit (ICU). The role of DEX for adjunctive treatment of refractory intracranial hypertension is poorly defined. The primary objective of this study was to determine the effect of DEX on the need for rescue therapy (ie, hyperosmolar boluses, extraventricular drain [EVD] drainages) for refractory intracranial hypertension. Secondary objectives included the number of intracranial pressure (ICP) excursions, bradycardic, hypotensive, and compromised cerebral perfusion pressure episodes. This retrospective cohort study evaluated patients admitted to the neurosurgical ICU from August 1, 2009, to July 29, 2015, and who received DEX for refractory intracranial hypertension. The objectives were compared between the 2 time periods-before (pre-DEX) and during therapy (DEX). Twenty-three patients with 26 episodes of refractory intracranial hypertension met the inclusion criteria. The number of hyperosmolar boluses was decreased after DEX therapy was initiated. Mannitol boluses required were statistically reduced (1 vs 0.5, P = .03); however, reduction in hypertonic boluses was not statistically significant (1.3 vs 0.9, P = .2). The mean number of EVD drainages per 24 hours was not significantly different between the time periods (15.7 vs 14.0, P = .35). The rate of ICP excursions did not differ between the 2 groups (24.3 vs 22.5, P = .62). When compared to pre-DEX data, there was no difference in the median number of hypotensive (0 vs 0), bradycardic (0 vs 0), or compromised cerebral perfusion pressure episodes (0.5 vs 1.0). Dexmedetomidine may avoid increases in the need for rescue therapy when used as an adjunctive treatment of refractory intracranial hypertension without compromising hemodynamics.

Microdialysis Monitoring in Clinical Traumatic Brain Injury and Its Role in Neuroprotective Drug Development

Injuries to the central nervous system continue to be vast contributors to morbidity and mortality; specifically, traumatic brain injury (TBI) is the most common cause of death during the first four decades of life. Several modalities are used to monitor patients suffering from TBI in order to prevent detrimental secondary injuries. The microdialysis (MD) technique, introduced during the 1990s, presents the treating physician with a robust monitoring tool for brain chemistry in addition to conventional intracranial pressure monitoring. Nevertheless, some limitations remain, such as limited spatial resolution. Moreover, while there have been several attempts to develop new potential pharmacological therapies in TBI, there are currently no available drugs which have shown clinical efficacy that targets the underlying pathophysiology, despite various trials investigating a plethora of pharmaceuticals. Specifically in the brain, MD is able to demonstrate penetration of the drug through the blood-brain barrier into the brain extracellular space at potential site of action. In addition, the downstream effects of drug action can be monitored directly. In the future, clinical MD, together with other monitoring modalities, can identify specific pathological substrates which require tailored treatment strategies for patients suffering from TBI.

A prospective randomized trial of the optimal dose of mannitol for intraoperative brain relaxation in patients undergoing craniotomy for supratentorial brain tumor resection

OBJECTIVE

Mannitol is used intraoperatively to induce brain relaxation in patients undergoing supratentorial brain tumor resection. The authors sought to determine the dose of mannitol that provides adequate brain relaxation with the fewest adverse effects.

METHODS

A total of 124 patients were randomized to receive mannitol at 0.25 g/kg (Group A), 0.5 g/kg (Group B), 1.0 g/kg (Group C), and 1.5 g/kg (Group D). The degree of brain relaxation was classified according to a 4-point scale (1, bulging; 2, firm; 3, adequate; and 4, perfectly relaxed) by neurosurgeons; Classes 3 and 4 were considered to indicate satisfactory brain relaxation. The osmolality gap (OG) and serum electrolytes were measured before and after mannitol administration.

RESULTS

The brain relaxation score showed an increasing trend in patients receiving higher doses of mannitol (p = 0.005). The incidence of satisfactory brain relaxation was higher in Groups C and D than in Group A (67.7% and 64.5% vs 32.2%, p = 0.011 and 0.022, respectively). The incidence of OG greater than 10 mOsm/kg was also higher in Groups C and D than in Group A (100.0% in both groups vs 77.4%, p = 0.011 for both). The incidence of moderate hyponatremia (125 mmol/L ≤ Na+ < 130 mmol/L) was significantly higher in Group D than in other groups (38.7% vs 0.0%, 9.7%, and 12.9% in Groups A, B, and C; p < 0.001, p = 0.008, and p = 0.020, respectively). Hyperkalemia (K+ > 5.0 mmol/L) was observed in 12.9% of patients in Group D only.

CONCLUSIONS

The higher doses of mannitol provided better brain relaxation but were associated with more adverse effects. Considering the balance between the benefits and risks of mannitol, the authors suggest the use of 1.0 g/kg of intraoperative mannitol for satisfactory brain relaxation with the fewest adverse effects.

Clinical trial registration no.: NCT02168075 (clinicaltrials.gov)

The effect of continuous hypertonic saline infusion and hypernatremia on mortality in patients with severe traumatic brain injury: a retrospective cohort study

PURPOSE

Hypertonic saline (HTS) is used to control intracranial pressure (ICP) in patients with traumatic brain injury (TBI); however, in prior studies, the resultant hypernatremia has been associated with increased mortality. We aimed to study the effect of HTS on ICP and mortality in patients with severe TBI.

METHODS

We performed a retrospective cohort study of 231 patients with severe TBI (Glasgow Coma Scale [GCS] ≤ 8) admitted to two neurotrauma units from 2006-2012. We recorded daily HTS, ICP, and serum sodium (Na) concentration. We used Cox proportional regression modelling for hospital mortality and incorporated the following time-dependent variables: use of HTS, hypernatremia, and desmopressin administration.

RESULTS

The mean [standard deviation (SD)] age of patients was 34 (17) and the median (interquartile range [IQR]) GCS was 6 [3-8]. Hypertonic saline was administered as a continuous infusion in 124 of 231 (54%) patients over 788 of 2,968 (27%) patient-days. Hypernatremia (Na > 145 mmol·L(-1)) developed in 151 of 231 (65%) patients over 717 of 2,968 (24%) patients-days. In patients who developed hypernatremia, the median [IQR] Na was 146 [142-147] mmol·L(-1). Overall hospital mortality was 26% (59 of 231 patients). After adjusting for baseline covariates, neither HTS (hazard ratio [HR], 1.07; 95% confidence interval [CI], 0.56 to 2.05; P = 0.84) nor hypernatremia (HR, 1.31; 95% CI, 0.68 to 2.55; P = 0.42) was associated with hospital mortality. There was no effect modification by either HTS or hypernatremia on each another. Patients who received HTS observed a significant decrease in ICP during their ICU stay compared with those who did not receive HTS (4 mmHg; 95% CI, 2 to 6; P < 0.001 vs 2 mmHg; 95% CI, -1 to 5; P = 0.14).

CONCLUSIONS

Hypertonic saline and hypernatremia are not associated with hospital mortality in patients with severe TBI.

Hypernatremia is a significant risk factor for acute kidney injury after subarachnoid hemorrhage: a retrospective analysis

BACKGROUND

Hypertonic saline therapy is often used in critically ill subarachnoid hemorrhage (SAH) patients for indications ranging from control of intracranial hypertension to managing symptomatic hyponatremia. The risk factors for developing acute kidney injury (AKI) in this patient population are not well defined.

SPECIFIC AIM

To study the role of serum sodium in developing AKI (based on the AKIN definition) in the SAH population admitted to a large academic neurocritical care unit.

METHODS

This is an IRB-approved, retrospective cohort study of patients admitted to a tertiary neuro intensive care unit. We included adult (age ≥ 18 years) SAH patients admitted to the neuro intensive care unit for at least 72 h. Development of AKI after admission to the ICU was defined using the AKIN serum creatinine criteria between 72 h and 14 days following admission. A Cox proportional hazards survival model with multiple time varying covariates was developed to evaluate the effect of maximum sodium exposure on the risk of AKI. Sodium exposure was captured as the running maximum of daily maximum serum sodium concentration (mEq/L). Sodium exposure was used as a surrogate for hypertonic saline therapy.

RESULTS

The final cohort of patients included 736 patients admitted to the neuro intensive care unit between 2006 and 2012. The number of patients who developed AKI was 64 (9 %). These patients had an increased length of stay (15.6 ± 9.4 vs. 12.5 ± 8.7 days). The odds of death were more than two fold greater among patients who developed AKI (odds ratio 2.33 95 % CI 1.27, 4.3). Sodium exposure was significantly associated with the hazard of developing AKI, adjusting for age, sex, preexisting renal disease, diabetes mellitus, radiocontrast exposure, number of days on mechanical ventilation, and admission Glasgow Coma Scale score. For each 1 mEq/L increase in the running maximum daily serum sodium, the hazard of developing AKI was increased by 5.4 % (95 % CI 1.4, 9.7).

CONCLUSION

The maximum daily sodium is a significant risk factor for developing AKI in patients with SAH.

Therapeutic Hypothermia Reduces Intracranial Pressure and Partial Brain Oxygen Tension in Patients with Severe Traumatic Brain Injury: Preliminary Data from the Eurotherm3235 Trial

Traumatic brain injury (TBI) is a significant cause of disability and death and a huge economic burden throughout the world. Much of the morbidity associated with TBI is attributed to secondary brain injuries resulting in hypoxia and ischemia after the initial trauma. Intracranial hypertension and decreased partial brain oxygen tension (PbtO2) are targeted as potentially avoidable causes of morbidity. Therapeutic hypothermia (TH) may be an effective intervention to reduce intracranial pressure (ICP), but could also affect cerebral blood flow (CBF). This is a retrospective analysis of prospectively collected data from 17 patients admitted to the Western General Hospital, Edinburgh. Patients with an ICP >20 mmHg refractory to initial therapy were randomized to standard care or standard care and TH (intervention group) titrated between 32°C and 35°C to reduce ICP. ICP and PbtO2 were measured using the Licox system and core temperature was recorded through rectal thermometer. Data were analyzed at the hour before cooling, the first hour at target temperature, 2 consecutive hours at target temperature, and after 6 hours of hypothermia. There was a mean decrease in ICP of 4.3±1.6 mmHg (p<0.04) from 15.7 to 11.4 mmHg, from precooling to the first epoch of hypothermia in the intervention group (n=9) that was not seen in the control group (n=8). A decrease in ICP was maintained throughout all time periods. There was a mean decrease in PbtO2 of 7.8±3.1 mmHg (p<0.05) from 30.2 to 22.4 mmHg, from precooling to stable hypothermia, which was not seen in the control group. This research supports others in demonstrating a decrease in ICP with temperature, which could facilitate a reduction in the use of hyperosmolar agents or other stage II interventions. The decrease in PbtO2 is not below the suggested treatment threshold of 20 mmHg, but might indicate a decrease in CBF.

What's new in the management of traumatic brain injury on neuro ICU?

PURPOSE OF REVIEW

In recent years, we have begun to better understand how to monitor the injured brain, look for less common complications and importantly, reduce unnecessary and potentially harmful intervention. However, the lack of consensus regarding triggers for intervention, best neuromonitoring techniques and standardization of therapeutic approach is in need of more careful study. This review covers the most recent evidence within this exciting and dynamic field.

RECENT FINDINGS

The role of intracranial pressure monitoring has been challenged; however, it still remains a cornerstone in the management of the severely brain-injured patient and should be used to compliment other techniques, such as clinical examination and serial imaging.The use of multimodal monitoring continues to be refined and it may be possible to use them to guide novel brain resuscitation techniques, such as the use of exogenous lactate supplementation in the future.

SUMMARY

Neurocritical care management of traumatic brain injury continues to evolve. However, it is important not to use a 'one-treatment-fits-all' approach, and perhaps look to use targeted therapies to individualize treatment.

Critical care for patients with massive ischemic stroke

Malignant cerebral edema following ischemic stroke is life threatening, as it can cause inadequate blood flow and perfusion leading to irreversible tissue hypoxia and metabolic crisis. Increased intracranial pressure and brain shift can cause herniation syndrome and finally brain death. Multiple randomized clinical trials have shown that preemptive decompressive hemicraniectomy effectively reduces mortality and morbidity in patients with malignant middle cerebral artery infarction. Another life-saving decompressive surgery is suboccipital craniectomy for patients with brainstem compression by edematous cerebellar infarction. In addition to decompressive surgery, cerebrospinal fluid drainage by ventriculostomy should be considered for patients with acute hydrocephalus following stroke. Medical treatment begins with sedation, analgesia, and general measures including ventilatory support, head elevation, maintaining a neutral neck position, and avoiding conditions associated with intracranial hypertension. Optimization of cerebral perfusion pressure and reduction of intracranial pressure should always be pursued simultaneously. Osmotherapy with mannitol is the standard treatment for intracranial hypertension, but hypertonic saline is also an effective alternative. Therapeutic hypothermia may also be considered for treatment of brain edema and intracranial hypertension, but its neuroprotective effects have not been demonstrated in stroke. Barbiturate coma therapy has been used to reduce metabolic demand, but has become less popular because of its systemic adverse effects. Furthermore, general medical care is critical because of the complex interactions between the brain and other organ systems. Some challenging aspects of critical care, including ventilator support, sedation and analgesia, and performing neurological examinations in the setting of a minimal stimulation protocol, are addressed in this review.

Principles of neuroanesthesia in aneurysmal subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage is associated with high mortality. Understanding of the underlying pathophysiology is important as early intervention can improve outcome. Increasing age, altered sensorium and poor Hunt and Hess grade are independent predictors of adverse outcome. Early operative interventions imposes an onus on anesthesiologists to provide brain relaxation. Coiling and clipping are the two treatment options with increasing trends toward coiling. Intraoperatively, tight control of blood pressure and adequate brain relaxation is desirable, so that accidental aneurysm rupture can be averted. Patients with poor grades tolerate higher blood pressures, but are prone to ischemia whereas patients with lower grades tolerate lower blood pressure, but are prone to aneurysm rupture if blood pressure increases. Patients with Hunt and Hess Grade I or II with uneventful intraoperative course are extubated in operation theater, whereas, higher grades are kept electively ventilated. Postoperative management includes attention toward fluid status and early management of vasospasm.

Hyperosmolar and methotrexate therapy avoiding surgery in the acute presentation of primary central nervous system lymphoma

Background:

Primary central nervous system lymphoma (PCNSL) is an aggressive type of extra-nodal non-Hodgkin lymphoma. Without treatment, PCNSL is associated with significant morbidity and mortality, including rapid neurological deterioration. In contrast to other high-grade intracranial neoplasms, PCNSL is considered to have a high response rate to conventional medical therapy, especially in younger patients, and therefore warrants particular attention in terms of nonsurgical treatment.

Case Description:

We report a case of the medical management of acute deterioration due to rapidly growing PCNSL with mass effect to highlight the efficacy of temporization with hyperosmolar therapy while awaiting the known rapid effects of dexamethasone and methotrexate (MTX) treatment. Surgical intervention was avoided, and tumor response was rapid. The patient had corresponding clinical resolution of symptoms of elevated intracranial pressure with return to neurologic baseline.

Conclusions:

Despite the evidence that PCNSL responds well to steroids and MTX, the rapidity of onset with which this occurs can vary. In patients presenting with mass effect and rapid neurologic decline, there is little evidence to support medical over surgical intervention. Herein we present an illustrative case of a large PCNSL lesion presenting with rapid decline. With clinical improvement in one day and a 50% reduction in tumor volume over less than seven days, the authors present the specific time frame with which PCNSL responds to medical therapy and a safe strategy for medical temporization.

The role of the microcirculation in delayed cerebral ischemia and chronic degenerative changes after subarachnoid hemorrhage

The mortality after aneurysmal subarachnoid hemorrhage (SAH) is 50%, and most survivors suffer severe functional and cognitive deficits. Half of SAH patients deteriorate 5 to 14 days after the initial bleeding, so-called delayed cerebral ischemia (DCI). Although often attributed to vasospasms, DCI may develop in the absence of angiographic vasospasms, and therapeutic reversal of angiographic vasospasms fails to improve patient outcome. The etiology of chronic neurodegenerative changes after SAH remains poorly understood. Brain oxygenation depends on both cerebral blood flow (CBF) and its microscopic distribution, the so-called capillary transit time heterogeneity (CTH). In theory, increased CTH can therefore lead to tissue hypoxia in the absence of severe CBF reductions, whereas reductions in CBF, paradoxically, improve brain oxygenation if CTH is critically elevated. We review potential sources of elevated CTH after SAH. Pericyte constrictions in relation to the initial ischemic episode and subsequent oxidative stress, nitric oxide depletion during the pericapillary clearance of oxyhemoglobin, vasogenic edema, leukocytosis, and astrocytic endfeet swelling are identified as potential sources of elevated CTH, and hence of metabolic derangement, after SAH. Irreversible changes in capillary morphology and function are predicted to contribute to long-term relative tissue hypoxia, inflammation, and neurodegeneration. We discuss diagnostic and therapeutic implications of these predictions.

Blocking neurogenic inflammation for the treatment of acute disorders of the central nervous system

Classical inflammation is a well-characterized secondary response to many acute disorders of the central nervous system. However, in recent years, the role of neurogenic inflammation in the pathogenesis of neurological diseases has gained increasing attention, with a particular focus on its effects on modulation of the blood-brain barrier BBB. The neuropeptide substance P has been shown to increase blood-brain barrier permeability following acute injury to the brain and is associated with marked cerebral edema. Its release has also been shown to modulate classical inflammation. Accordingly, blocking substance P NK1 receptors may provide a novel alternative treatment to ameliorate the deleterious effects of neurogenic inflammation in the central nervous system. The purpose of this paper is to provide an overview of the role of substance P and neurogenic inflammation in acute injury to the central nervous system following traumatic brain injury, spinal cord injury, stroke, and meningitis.

Hypertonic saline, not mannitol, should be considered gold-standard medical therapy for intracranial hypertension

Hyperosmolar therapy is the principal medical management strategy for elevated intracranial pressure. Mannitol has been the primary hyperosmolar agent for nearly a century and remains the de facto gold standard for medical management of intracranial hypertension. Over the past 25 years, however, hypertonic saline (HTS) has become a progressively more common alternative to mannitol, and several recent studies have suggested its relative superiority. These findings have prompted calls for large-scale comparator trials of mannitol and HTS, but such trials would only be necessary if the designation of mannitol as the gold standard is appropriate and if current evidence suggests its therapeutic equipoise with HTS. Mounting evidence supporting HTS suggests that neither of these conditions is necessarily true and, instead, mandates reassessment of the actual gold-standard agent for hyperosmolar therapy. In the present article I make the case that current evidence supports HTS, not mannitol, as the better choice for gold-standard therapy for medical management of intracranial hypertension. This is accomplished first by examining the evidence on which the apparent designation of mannitol as the presumed gold-standard is based, then by reviewing the recent comparative efficacy data for HTS versus mannitol, and finanally by discussing additional clinical considerations for appropriate designation of a gold-standard agent for hyperosmolar therapy. This assessment has important implications both for patient care and for clinical trial design.