Mannitol causes compensatory cerebral vasoconstriction and vasodilation in response to blood viscosity changes

Cerebrovascular Pressure Reactivity Measures: Index Comparison and Clinical Outcome in Patients With Traumatic Brain Injury Treated According to an Intracranial Pressure-Focused Management: Rejection of the Null Hypothesis

The aim was to investigate whether the pressure reactivity indices PRx, long-PRx (L-PRx), and pressure reactivity (PR) are interchangeable as measures of vascular reactivity, and whether they correlate with clinical outcome when an intracranial pressure (ICP)-targeted treatment regimen is applied in patients with traumatic brain injury (TBI). Patients with TBI (n = 29) that arrived at the hospital within 24 h of injury were included. PRx and L-PRx were derived from Pearson correlations between mean arterial pressure (MAP) and ICP over a short- and long-time interval. PR was the regression coefficient between the hourly mean values of ICP and MAP. Indices were compared to each other, parameters at admission, and outcome assessed by the extended Glasgow Outcome Scale-Extended (GOSE) at 6 and 12 months. PRx and L-PRx had the strongest correlation with each other (R = 0.536, p < 0.01). A correlation was also noted between L-PRx and PR (R = 0.475, p < 0.01), but not between PRx and PR. A correlation was found between age and PRx (R = 0.482, p = 0.01). No association with outcome for any of the indices was found. PRx/L-PRx and L-PRx/PR were moderately correlated with each other. Age was associated with PRx. None of the indices correlated with outcome when our ICP treatment regime was applied. Part of our null hypothesis, that the three indices are associated with outcome, must be rejected. There was, however, an association between some of the indices. To further understand the relation of treatment regimes and pressure reactivity indices, a larger, randomized study is warranted.

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.

Medical management of cerebral edema in large hemispheric infarcts

Acute ischemic stroke confers a high burden of morbidity and mortality globally. Occlusion of large vessels of the anterior circulation, namely the intracranial carotid artery and middle cerebral artery, can result in large hemispheric stroke in ~8% of these patients. Edema from stroke can result in a cascade effect leading to local compression of capillary perfusion, increased stroke burden, elevated intracranial pressure, herniation and death. Mortality from large hemispheric stroke is generally high and surgical intervention may reduce mortality and improve good outcomes in select patients. For those patients who are not eligible candidates for surgical decompression either due timing, medical co-morbidities, or patient and family preferences, the mainstay of medical management for cerebral edema is hyperosmolar therapy. Other neuroprotectants for cerebral edema such as glibenclamide are under investigation. This review will discuss current guidelines and evidence for medical management of cerebral edema in large hemispheric stroke as well as discuss important neuromonitoring and critical care management targeted at reducing morbidity and mortality for these patients.

Risk Factors Associated With Inadequate Brain Relaxation in Craniotomy for Surgery of Supratentorial Tumors

Introduction: Cerebral swelling often occurs during craniotomy for cerebral tumors. Poor brain relaxation can increase the risk of cerebral ischemia, possibly worsening the outcome. The surgical team should identify any risk factors that could cause perioperative brain swelling and decide which therapies are indicated for improving it. The present investigation aimed to elucidate the risk factors associated with brain swelling during elective craniotomy for supratentorial brain tumors.

Methods: This prospective, nonrandomized, observational study included 52 patients scheduled for elective supratentorial tumor surgery. The degree of brain relaxation was classified upon the opening of the dura according to a four-point scale (brain relaxation score: 1, perfectly relaxed; 2, satisfactorily relaxed; 3, firm brain; and 4, bulging brain). Moreover, hemodynamic and respiratory parameters, arterial blood gas, and plasma osmolality were recorded after the removal of the bone flap.

Results: This study showed that the use of preoperative dexamethasone was associated with a brain relaxation score of ≤2 (p = 0.005). The median midline shift of 6 (3-0) mm and median hemoglobin level of >13 g/dL were associated with a brain relaxation score of ≥3 (p = 0.02 and p = 0.01, respectively). The dosage of mannitol (0.25 g/kg versus 0.5 g/kg), physical status, intraoperative position, tumor diameter and volume, peritumoral edema and mass effect, World Health Organization (WHO) grading, mean arterial pressure, PaCO₂, osmolality, and core temperature were not identified as risk factors associated with poor relaxation.

Conclusion: The use of preoperative dexamethasone was associated with improved brain relaxation, whereas the presence of a preoperative midline shift and a higher level of hemoglobin were associated with poor brain relaxation.

Traumatic Brain Injury-A Review of Intravenous Fluid Therapy

This manuscript will review intravenous fluid therapy in traumatic brain injury. Both human and animal literature will be included. Basic treatment recommendations will also be discussed.

An Audit and Comparison of pH, Measured Concentration, and Particulate Matter in Mannitol and Hypertonic Saline Solutions

Background: The preferred hyperosmolar therapy remains controversial. Differences in physical properties such as pH and osmolality may be important considerations in hyperosmolar agent selection. We aimed to characterize important physical properties of commercially available hyperosmolar solutions.

Methods: We measured pH and concentration in 37 commonly-used hyperosmolar solutions, including 20 and 25% mannitol and 3, 5, 14.6, and 23.4% hypertonic saline. pH was determined digitally and with litmus paper. Concentration was determined by freezing point and vapor pressure osmometry. Salinity/specific gravity was measured with portable refractometry. Particulate matter was analyzed with filtration and light microscopy and with dynamic light scattering nephelometry.

Results: pH of all solutions was below physiological range (measured range 4.13–6.80); there was no correlation between pH and solution concentration (R² = 0.005, p = 0.60). Mannitol (mean 5.65, sd 0.94) was less acidic than hypertonic saline (5.16, 0.60). 14/59 (24%) pH measurements and 85/111 concentration measurements were outside manufacturer standards. All 36/36 mannitol concentration measurements were outside standards vs. 48/72 (67%) hypertonic saline (p < 0.0001). All solutions examined on light microscopy contained crystalline and/or non-crystalline particulate matter up to several hundred microns in diameter. From nephelometry, particulate matter was detected in 20/22 (91%) solutions.

Conclusion: We present a novel characterization of mannitol and hypertonic saline. Further research should be undertaken, including research examining development of acidosis following hyperosmolar therapy, the relevance of our findings for dose-response, and the clinical relevance of particulate matter in solution.

What is the Role of Hyperosmolar Therapy in Hemispheric Stroke Patients?

The role of hyperosmolar therapy (HT) in large hemispheric ischemic or hemorrhagic strokes remains a controversial issue. Past and current stroke guidelines state that it represents a reasonable therapeutic measure for patients with either neurological deterioration or intracranial pressure (ICP) elevations documented by ICP monitoring. However, the lack of evidence for a clear effect of this therapy on radiological tissue shifts and clinical outcomes produces uncertainty with respect to the appropriateness of its implementation and duration in the context of radiological mass effect without clinical correlates of neurological decline or documented elevated ICP. In addition, limited data suggest a theoretical potential for harm from the prophylactic and protracted use of HT in the setting of large hemispheric lesions. HT exerts effects on parenchymal volume, cerebral blood volume and cerebral perfusion pressure which may ameliorate global ICP elevation and cerebral blood flow; nevertheless, it also holds theoretical potential for aggravating tissue shifts promoted by significant interhemispheric ICP gradients that may arise in the setting of a large unilateral supratentorial mass lesion. The purpose of this article is to review the literature in order to shed light on the effects of HT on brain tissue shifts and clinical outcome in the context of large hemispheric strokes, as well as elucidate when HT should be initiated and when it should be avoided.

Evidence for Mannitol as an Effective Agent Against Intracranial Hypertension: An Individual Patient Data Meta-analysis

Mannitol is currently used to reduce intracranial pressure (ICP), but the evidence supporting its usefulness has been questioned. We aim to meta-analyze the effectiveness of mannitol in reducing ICP in adult patients with cerebral injuries and its dependency on baseline ICP values, comparing findings from individual patient data (IPD) and aggregated data (AD) meta-analysis performed on the same studies. We searched the Medline database, with no time limitation, through March 1, 2019. We selected studies for which IPD were available, with a before-after design, concerning adult patients with traumatic cerebral hemorrhages, subarachnoid hemorrhages, or hemorrhagic and ischemic stroke, treated with mannitol for increased intracranial hypertension. We extracted ICP values at baseline and at different time-points, and mannitol doses. We used a multilevel approach to account for multiple measurements on the same patient and for center variability. The AD meta-analysis and meta-regression were conducted using random-effects models. Three studies published IPD, and four authors shared their datasets. Two authors did not own their datasets anymore. Eight authors were unreachable, while 14 did not answer to our request. Overall, 7 studies provided IPD for 98 patients. The linear mixed-effects model showed that ICP decreased significantly after mannitol administration from an average baseline value of 22.1 mmHg to 16.8, 12.8, and 9.7 mmHg at 60, 120, and 180 min after mannitol administration. ICP reduction was proportional to baseline values with a 0.64 mmHg decrease for each unitary increment of the initial ICP value. Dose did not influence ICP reduction. The AD meta-analysis, based on data collected between 30 and 60 min from mannitol administration not accounting for multiple time-point measurements, overestimated ICP reduction (10 mmHg), while meta-regression provided similar results (0.66 mmHg decrease for each unitary increase of initial ICP). Mannitol is effective in reducing pathological ICP, proportionally to the degree of intracranial hypertension. IPD meta-analysis provided a more precise quantification of ICP variation than the AD approach.

Prehospital fluid administration in patients with severe traumatic brain injury: A systematic review and meta-analysis

BACKGROUND

Prehospital management of severe traumatic brain injury (TBI) focuses on preventing secondary brain injury. Therefore, hypotension should be prevented, or if present, should be promptly treated in order to maintain optimal cerebral perfusion pressure. Fluid resuscitation is a traditional mainstay in the prehospital treatment of hypotension, however, the choice of fluid type that is to be administered in the prehospital setting is the subject of an on-going debate. This systematic review and meta-analysis was therefore performed to assess the effect of different fluid types on outcome in patients with severe TBI.

METHODS

PubMed, Embase and Web of Science were searched for articles up to March 2020. Studies comparing two or more prehospital administered fluid types with suspected or confirmed severe TBI were deemed eligible for inclusion. Studied outcomes were mortality and (extended) Glasgow Outcome Scale (GOS). The meta-analysis tested for differences in survival between hypertonic saline (HTS) and normotonic crystalloids (i.e. normal saline or Lactated Ringer's) and between hypertonic saline with dextran (HSD) and normotonic crystalloids. The systematic review is registered in the PROSPERO register with number CRD42020140423.

RESULTS

This literature search yielded a total of 519 articles, of which 12 were included in the systematic review and 6 were included in the meta-analysis. Eleven studies found no statistically significant difference in survival between patients treated with different fluid types (e.g. normal saline and hypertonic saline). All studies assessing neurological outcome, measured through (extended) GOS, found no statistically significant difference between different fluid types. Meta-analysis showed no better survival for patients treated with HSD, when compared to normotonic crystalloids (overall RR 0.99, 95% CI 0.93-1.06). Moreover, HTS compared to normotonic crystalloids does not result in a better survival (overall RR 1.04, 95% CI 0.97-1.12).

CONCLUSIONS

This systematic review and meta-analysis did not demonstrate a survival or neurological benefit for one specific fluid type administered in the prehospital setting.

Correlation of Initial Computed Tomography Findings with Outcomes of Patients with Acute Subdural Hematoma: A Prospective Study

Introduction In modern emergency service systems, patients are often treated with sedation, intubation, and ventilation at the accident site. But neurosurgical assessment before all these emergency services is important. Thus, this study was designed to investigate the relationships between various parameters of initial CT scan findings and the outcomes of the patients.

Methodology A total of 56 adult patients of traumatic acute subdural hematoma (SDH) whose computed tomography (CT) scan was performed within 8 hours of injury were recruited. The patients with prolonged hypotension, open head injury or depressed skull fracture, bilateral side acute SDH, or contusions/hematoma/extradural hematoma on the contralateral side were excluded. Six separate CT findings were analyzed and recorded, including hematoma, midline shift, subarachnoid hemorrhage (SAH), presence of basal cistern obliteration (BCO), intraparenchymal hematoma/contusion in the same hemisphere, and presence of effacement of the sulcal spaces, and were followed up for three months for outcome analysis.

Results The overall mortality and functional recovery rate were 27 and 50%, respectively. The patients with obliterated basal cisterns and the presence of underlying SAH in patients with acute SDH had statistically significant poorer outcomes as compared with others. However, the extent of midline shift, SDH thickness, and the presence of underlying contusions and sulcal effacement on initial CT scan showed no statistically significant correlation with patients’ outcomes.

Conclusions BCO and presence of subarchnoid hemorrhage underlying acute SDH on the earliest scan in head injury patients signify the severity of brain parenchymal injury. Along with the initial Glasgow Coma Scale score after resuscitation, these two factors should be considered as the most significant ones for predicting the outcomes in traumatic acute SDH patients.

Hypertonic Saline is Superior to Mannitol for the Combined Effect on Intracranial Pressure and Cerebral Perfusion Pressure Burdens in Patients With Severe Traumatic Brain Injury

BACKGROUND

Hypertonic saline (HTS) and mannitol are effective in reducing intracranial pressure (ICP) after severe traumatic brain injury (TBI). However, their simultaneous effect on the cerebral perfusion pressure (CPP) and ICP has not been studied rigorously.

OBJECTIVE

To determine the difference in effects of HTS and mannitol on the combined burden of high ICP and low CPP in patients with severe TBI.

METHODS

We performed a case-control study using prospectively collected data from the New York State TBI-trac® database (Brain Trauma Foundation, New York, New York). Patients who received only 1 hyperosmotic agent, either mannitol or HTS for raised ICP, were included. Patients in the 2 groups were matched (1:1 and 1:2) for factors associated with 2-wk mortality: age, Glasgow Coma Scale score, pupillary reactivity, hypotension, abnormal computed tomography scans, and craniotomy. Primary endpoint was the combined burden of ICPhigh (> 25 mm Hg) and CPPlow (< 60 mm Hg).

RESULTS

There were 25 matched pairs for 1:1 comparison and 24 HTS patients matched to 48 mannitol patients in 1:2 comparisons. Cumulative median osmolar doses in the 2 groups were similar. In patients treated with HTS compared to mannitol, total number of days (0.6 ± 0.8 vs 2.4 ± 2.3 d, P < .01), percentage of days with (8.8 ± 10.6 vs 28.1 ± 26.9%, P < .01), and the total duration of ICPhigh + CPPlow (11.12 ± 14.11 vs 30.56 ± 31.89 h, P = .01) were significantly lower. These results were replicated in the 1:2 match comparisons.

CONCLUSION

HTS bolus therapy appears to be superior to mannitol in reduction of the combined burden of intracranial hypertension and associated hypoperfusion in severe TBI patients.

Dynamic cerebral perfusion parameters and magnetic nanoparticle accumulation assessed by AC biosusceptometry

Cerebral blood flow (CBF) assessment is mainly performed by scintigraphy, computed tomography (CT) and magnetic resonance imaging (MRI). New approaches to assess the CBF through the passage of magnetic nanoparticles (MNPs) to blood-brain barrier (BBB) are convenient to help decrease the use of ionizing radiation and unleash the required MRI schedule in clinics. The development of nanomedicine and new biomedical devices, such as the magnetic particle imaging (MPI), enabled new approaches to study dynamic brain blood flow. In this paper, we employed MNPs and the alternating current biosusceptometry (ACB) to study the brain perfusion. We utilized the mannitol, before the MNPs, injection to modulate the BBB permeability and study its effects on the circulation time of the MNPs in the brain of rats. Also, we characterized a new ACB sensor to increase the systems' applicability to study the MNPs' accumulation, especially in the animals' brain. Our data showed that the injection of mannitol increased the circulation time of MNPs in the brain. Also, the mannitol increased the accumulation of MNPs in the brain. This paper suggests the use of the ACB as a tool to study brain perfusion and accumulation of MNPs in studies of new nano agents focused on the brain diagnostics and treatment.

The Medical Management of Cerebral Edema: Past, Present, and Future Therapies

Cerebral edema is commonly associated with cerebral pathology, and the clinical manifestation is largely related to the underlying lesioned tissue. Brain edema usually amplifies the dysfunction of the lesioned tissue and the burden of cerebral edema correlates with increased morbidity and mortality across diseases. Our modern-day approach to the medical management of cerebral edema has largely revolved around, an increasingly artificial distinction between cytotoxic and vasogenic cerebral edema. These nontargeted interventions such as hyperosmolar agents and sedation have been the mainstay in clinical practice and offer noneloquent solutions to a dire problem. Our current understanding of the underlying molecular mechanisms driving cerebral edema is becoming much more advanced, with differences being identified across diseases and populations. As our understanding of the underlying molecular mechanisms in neuronal injury continues to expand, so too is the list of targeted therapies in the pipeline. Here we present a brief review of the molecular mechanisms driving cerebral edema and a current overview of our understanding of the molecular targets being investigated.

Treatments and rehabilitation in the acute and chronic state of traumatic brain injury

Traumatic brain injury (TBI) is a major cause of acquired disability globally, and effective treatment methods are scarce. Lately, there has been increasing recognition of the devastating impact of TBI resulting from sports and other recreational activities, ranging from primarily sport-related concussions (SRC) but also more severe brain injuries requiring hospitalization. There are currently no established treatments for the underlying pathophysiology in TBI and while neuro-rehabilitation efforts are promising, there are currently is a lack of consensus regarding rehabilitation following TBI of any severity. In this narrative review, we highlight short- and long-term consequences of SRCs, and how the sideline management of these patients should be performed. We also cover the basic concepts of neuro-critical care management for more severely brain-injured patients with a focus on brain oedema and the necessity of improving intracranial conditions in terms of substrate delivery in order to facilitate recovery and improve outcome. Further, following the acute phase, promising new approaches to rehabilitation are covered for both patients with severe TBI and athletes suffering from SRC. These highlight the need for co-ordinated interdisciplinary rehabilitation, with a special focus on cognition, in order to promote recovery after TBI.

Mannitol decreases neocortical epileptiform activity during early brain development via cotransport of chloride and water

Seizures and brain injury lead to water and Cl^- accumulation in neurons. The increase in intraneuronal Cl^- concentration ([Cl^-]_i) depolarizes the GABA_A reversal potential (E_GABA) and worsens seizure activity. Neocortical neuronal membranes have a low water permeability due to the lack of aquaporins necessary to move free water. Instead, neurons use cotransport of ions including Cl^- to move water. Thus, increasing the extracellular osmolarity during seizures should result in an outward movement of water and salt, reducing [Cl^-]_i and improving GABA_A receptor-mediated inhibition. We tested the effects of hyperosmotic therapy with a clinically relevant dose of mannitol (20 mM) on epileptiform activity, spontaneous multiunit activity, spontaneous inhibitory post-synaptic currents (sIPSCs), [Cl^-]_i, and neuronal volume in layer IV/V of the developing neocortex of C57BL/6 and Clomeleon mice. Using electrophysiological techniques and multiphoton imaging in acute brain slices (post-natal day 7-12) and organotypic neocortical slice cultures (post-natal day 14), we observed that mannitol: 1) decreased epileptiform activity, 2) decreased neuronal volume and [Cl^-]_i through CCCs, 3) decreased spontaneous multi-unit activity frequency but not amplitude, and 4) restored the anticonvulsant efficacy of the GABA_A receptor modulator diazepam. Increasing extracellular osmolarity by 20 mOsm with hypertonic saline did not decrease epileptiform activity. We conclude that an increase in extracellular osmolarity by mannitol mediates the efflux of [Cl^-]_i and water through CCCs, which results in a decrease in epileptiform activity and enhances benzodiazepine actions in the developing neocortex in vitro. Novel treatments aimed to decrease neuronal volume may concomitantly decrease [Cl^-]_i and improve seizure control.

Hypertonic Solutions in Traumatic Brain Injury: A Systematic Review and Meta-Analysis

This study aims to evaluate the efficacy of hypertonic saline versus crystalloids (normal Saline/lactated Ringers) in improving clinical outcome in patients with traumatic brain injury (TBI). Electronic databases and grey literature (unpublished articles) were searched under different MeSH terms from 1990 to present. Randomized control trials, case–control studies and prospective cohort studies on decompressive craniectomy in TBI (>18-year-old). Clinical outcome measures included Glasgow Coma Outcome Scale (GCOS), Extended GCOS, and mortality. Data were extracted to Review Manager Software. A total of 115 articles that met the inclusion criteria were retrieved and analyzed. Ultimately, five studies were included in our meta-analysis, which revealed that patients with TBI who had hypertonic saline had no statistically significant likelihood of having a good outcome at discharge or 6 months than those who had crystalloid (odds ratio [OR]: 0.01; 95% confidence interval (CI): 0.03–0.05; P = 0.65). The relative risk (RR) of mortality in hypertonic saline versus the crystalloid at discharge or 6-month is RR: 0.80; 95% CI: 0.64–0.99; P = 0.04. The subgroup analysis showed that the group who had hypertonic solution significantly decreases the number of interventions versus the crystalloid group OR: 0.53; 95% CI: 0.48–0.59; P < 0.00001 and also reduces the length of intensive care unit stay (OR: 0.46; 95% CI: 0.21–1.01; P = 0.05). Hypertonic saline decreases the financial burden, but neither impacts the clinical outcome nor reduces the mortality. However, further clinical trials are required to prove if hypertonic saline has any role in improving the clinical and neurological status of patients with TBI versus the normal saline/lactated Ringers.

Overview of Monitoring of Cerebral Blood Flow and Metabolism after Severe Head Injury

The relationships between cerebral blood flow (CBF), cerebral metabolism (cerebral metabolic rate of oxygen, CMRO2) and cerebral oxygen extraction (arteriovenous difference of oxygen, AVDO2) are discussed, using the formula CMRO2 = CBF × AVDO2. Metabolic autoregulation, pressure autoregulation and viscosity autoregulation can all be explained by the strong tendency of the brain to keep AVDO2 constant. Monitoring of CBF, CMRO2 or AVDO2 very early after injury is impractical, but the available data indicate that cerebral ischemia plays a considerable role at this stage. It can best be avoided by not "treating" arterial hypertension and not using too much hyperventilation, while generous use of mannitol is probably beneficial. Once in the ICU, treatment can most practically be guided by monitoring of jugular bulb venous oxygen saturation. If saturation drops below 50%, the reason for this must be found (high intracranial pressure, blood pressure not high enough, too vigorous hyperventilation, arterial hypoxia, anemia) and must be treated accordingly.

Effects of Hypertonic Saline and Sodium Lactate on Cortical Cerebral Microcirculation and Brain Tissue Oxygenation

BACKGROUND

Hyperosmolar solutions have been used in neurosurgery to modify brain bulk. The aim of this animal study was to compare the short-term effects of equivolemic, equiosmolar solutions of hypertonic saline (HTS) and sodium lactate (HTL) on cerebral cortical microcirculation and brain tissue oxygenation in a rabbit craniotomy model.

METHODS

Rabbits (weight, 1.5 to 2.0 kg) were anesthetized, ventilated mechanically, and subjected to a craniotomy. The animals were allocated randomly to receive a 3.75 mL/kg intravenous infusion of either 3.2% HTS (group HTS, n=9), half-molar sodium lactate (group HTL, n=10), or normal saline (group C, n=9). Brain tissue partial pressure of oxygen (PbtO2) and microcirculation in the cerebral cortex using sidestream dark-field imaging were evaluated before, 20 and 40 minutes after 15 minutes of hyperosmolar solution infusion. Global hemodynamic data were recorded, and blood samples for laboratory analysis were obtained at the time of sidestream dark-field image recording.

RESULTS

No differences in the microcirculatory parameters were observed between the groups before and after the use of osmotherapy. Brain tissue oxygen deteriorated over time in groups C and HTL, this deterioration was not significant in the group HTS.

CONCLUSIONS

Our findings suggest that equivolemic, equiosmolar HTS and HTL solutions equally preserve perfusion of cortical brain microcirculation in a rabbit craniotomy model. The use of HTS was better in preventing the worsening of brain tissue oxygen tension.

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.

The Combined Use of Cardiac Output and Intracranial Pressure Monitoring to Maintain Optimal Cerebral Perfusion Pressure and Minimize Complications for Severe Traumatic Brain Injury

Objective

To show the effect of dual monitoring including cardiac output (CO) and intracranial pressure (ICP) monitoring for severe traumatic brain injury (TBI) patiens. We hypothesized that meticulous treatment using dual monitoring is effective to sustain maintain minimal intensive care unit (ICU) complications and maintain optimal ICP and cerebral perfusion pressure (CPP) for severe TBI patiens.

Methods

We included severe TBI, below Glasgow Coma Scale (GCS) 8 and head abbreviation injury scale (AIS) >4 and performed decompressive craniectomy at trauma ICU of our hospital. We collected the demographic data, head AIS, injury severity score (ISS), initial GCS, ICU stay, sedation duration, fluid therapy related complications, Glasgow Outcome Scale (GOS) at 3 months and variable parameters of ICP and CO monitor.

Results

Thirty patients with severe TBI were initially selected. Thirteen patients were excluded because 10 patients had fixed pupillary reflexes and 3 patients had uncontrolled ICP due to severe brain edema. Overall 17 patients had head AIS 5 except 2 patients and 10 patients (58.8%) had multiple traumas as mean ISS 29.1. Overall complication rate of the patients was 64.7%. Among the parameters of CO monitoring, high stroke volume variation is associated with fluid therapy related complications (p=0.043) and low cardiac contractibility is associated with these complications (p=0.009) statistically.

Conclusion

Combined use of CO and ICP monitors in severe TBI patients who could be necessary to decompressive craniectomy and postoperative sedation is good alternative methods to maintain an adequate ICP and CPP and reduce fluid therapy related complications during postoperative ICU care.

Aggressive medical management of acute traumatic subdural hematomas before emergency craniotomy in patients presenting with bilateral unreactive pupils. A cohort study

BACKGROUND

The outcome of patients with severe traumatic brain injury (TBI) and acute traumatic subdural hematoma (aSDH) admitted to the emergency room with bilaterally dilated, unreactive pupils (bilateral mydriasis) is notoriously poor.

METHODS

Of 2074 TBI patients consecutively admitted to our facility between 1997 and 2012, 115 had a first CT scan with aSDH, unreactive bilateral mydriasis, and a Glasgow Coma Score of 3 or 4. Sixty-two patients were unoperated and died within hours or a few days. The remaining 53 patients (2.5% of the 2074 consecutive patients) were scheduled for emergent evacuation of the aSDH. We compared three different dosages of mannitol to landmark different comprehensive levels of treatment: (1) a "basic" level of treatment characterized by a single conventional dose (18 to 36 g), (2) "reinforced" treatment landmarked by a single high dose (54 to 72 g), and (3) "aggressive" treatment landmarked by a single high dose (90 to 106 g). Doses above 36 g were administered intravenously over a period of 5 min.

RESULTS

Of the 53 selected patients, 7 were aggressively managed (13.2%) and 24 (45.3%) received reinforced treatment. Rates of hyperventilation and barbiturate bolus administration were appropriately associated with increasing doses of mannitol. After adjustment for age, aggressive management was significantly associated with a lower risk of death and persistent vegetative state [adjusted OR 0.016 (95% 0.001-0.405)]. Patients surviving after aggressive management suffered more severe disability at 1 year.

CONCLUSION

The study shows an association between reduced mortality and persistent vegetative state, albeit at the cost of increased long-term severe disability in survivors, and aggressive medical preoperative management of mydriatic patients with aSDH following TBI.

Acute Management of Moderate-Severe Traumatic Brain Injury

Traumatic brain injury (TBI) continues to be a major public health problem. Proposed treatments have not withstood testing in clinical trials because of failure to account for different types of TBI and other weaknesses in trial design. Management goals continue to be prevention and prompt treatment of secondary insults (hypotension, hypoxia, and other physiologic derangements). This goal is best accomplished by careful attention to airway, breathing, circulation, and basic principles of intensive care unit management. Attempts to intervene prophylactically to prevent intracranial hypertension or other complications have not been beneficial and may even have deleterious effects.

D-mannitol sensor based on molecularly imprinted polymer on electrode modified with reduced graphene oxide decorated with gold nanoparticles

An electrochemical sensor for D-mannitol based on molecularly imprinted polymer on electrode modified with reduced graphene oxide decorated with gold nanoparticles was developed in this present work. The sensor was constructed for the first time via the electropolymerization of o-phenylenediamine (o-PD) over a surface containing reduced graphene oxide (RGO) and gold nanoparticles (AuNP) in the presence of D-mannitol molecules. The surface modification with AuNP/RGO-GCE facilitated the charge transfer processes of [Fe(CN)₆]^3-/4-, which was used as an electrochemical probe. It also contributed meaningfully towards the increase in the surface/volume ratio, creating more locations for imprinting, and providing greater sensitivity to the sensor. The MIP/AuNP/RGO-GCE sensor was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), atomic force microscope (AFM) and X-ray Photoelectron Spectroscopy (XPS). Important parameters that exert control over the performance of the molecularly imprinted sensor (such as number of cycles, pH, monomer and template concentration and extraction and rebinding conditions) were investigated and optimized. The imprinting factor was 4.9, showing greater response to the D-mannitol molecule compared to the interfering molecules. The limit of detection, limit of quantification and amperometric sensitivity were 7.7×10^-13molL^-1, 2.6×10^-12molL^-1 and 3.9×10¹⁰µALmol^-1 (n=3) respectively. The MIP/AuNP/RGO-GCE sensor was successfully applied towards the selective determination of D-mannitol in sugarcane vinasse, thus making it, in essence, a valuable tool for the accurate and reliable determination of this molecule.

Management of Brain Edema Complicating Stroke

Ischemic brain edema, the accumulation of fluid within the brain parenchyma following stroke, is a predictable consequence of both ischemic and hemorrhagic strokes. Its development is the result of injury to both brain parenchyma and the blood vessels supplying the parenchyma. Ischemic stroke produces both cytotoxic (intracellular) edema, which develops when cells are damaged, and vasogenic (extracellular) edema, which arises from injury to structures essential to blood-brain barrier integrity. An understanding of the distinction between cytotoxic and vasogenic edema is essential in preventing secondary brain injury, since the treatments for the two entities differ. The development of new brain imaging technologies has advanced our understanding of brain edema. Both computed tomography (CT) and magnetic resonance imaging (MRI) can detect edema. Specific MRI sequences such as diffusion-weighted imaging can distinguish cytotoxic and vasogenic subtypes, and thereby detect ischemic cell injury within minutes of the onset of symptoms.

Brain edema causes neurologic deterioration predominantly through its mass effect, which leads to distortion of the intracranial contents and impairment of both regional and global cerebral blood flow (CBF). Edema may also cause local tissue dysfunction. Management of the intracranial hypertension and tissue shifts caused by ischemic brain swelling is based on the fundamental relationship between pressure, flow, and resistance. Interventions are directed at preserving CBF and preventing secondary brain injury. Strategies include reducing intracranial blood volume with hypocapnia, reducing brain volume with osmotic agents, reducing cerebral metabolism with hypothermia and barbiturates, reducing resistance with rheologic agents, increasing blood pressure with vasoconstrictors, and expanding the cranial vault with decompressive surgery. All individual therapies must be used as part of a structured approach that involves frequent serial neurologic assessments, quantitative measures of pressure, flow, and resistance, and prespecified protocols for intervention.

Hyperosmolar therapy in pediatric traumatic brain injury: a retrospective study

OBJECTIVES

The objectives of the study are to describe the use of hyperosmolar therapy in pediatric traumatic brain injury (TBI) and examine its effect on intracranial pressure (ICP) and cerebral perfusion pressure (CPP).

DESIGN

A retrospective review of patients with severe TBI admitted to the pediatric intensive care unit (PICU) was conducted. Inclusion criteria were ICP monitoring and administration of a hyperosmolar agent (20 % mannitol or 3 % hypertonic saline) within 48 h of PICU admission; for which dose and timing were recorded. For the first two boluses received for increased ICP (>20 mmHg), the impact on ICP and CPP was assessed during the following 4 h, using repeated measures ANOVA. Co-interventions to control ICP (additional hyperosmolar agent, propofol, or barbiturate bolus) and serum sodium were also documented.

SETTING

A tertiary care pediatric hospital center.

PATIENTS

Children aged 1 month to 18 years, with severe traumatic brain injury (Glasgow Coma Score ≤ 8) and intracranial pressure (ICP) monitor.

RESULTS

Sixty-four patients were eligible, of which 16 met inclusion criteria. Average age was 11 years (SD ± 4) and median Glasgow Coma Score was 6 (range 4-7). Seventy percent of boluses were 3 % hypertonic saline, with no identified baseline difference associated with this initial choice. Both mannitol and hypertonic saline were followed by a non-significant decrease in ICP (mannitol, p = 0.055 and hypertonic saline, p = 0.096). There was no significant change in CPP post bolus. A co-intervention occurred in 69 % of patients within the 4 h post hyperosmolar agent, and eight patients received continuous 3 % saline.

CONCLUSION

In pediatric TBI with intracranial hypertension, mannitol and 3 % hypertonic saline are commonly used, but dose and therapeutic threshold for use vary without clear indications for one versus another. Controlled trials are warranted, but several barriers were identified, including high exclusion rate, multiple co-interventions, and care variability.

Management of Elevated Intracranial Pressure

Elevated intracranial pressure (ICP) is a primary cause of morbidity and mortality for many neurologic disorders. The relationship between ICP and brain volume is influenced by autoregulatory processes that can become dysfunctional. As a result, neurologic damage can occur by systemic and intracranial insults such as ischemia and excitatory amino acids. Therefore, survival is dependent on optimizing ICP and cerebral perfusion pressure. Treatment of intracranial hypertension requires intensive monitoring and aggressive therapy. Intracranial pressure monitoring techniques such as intraventricular catheters are useful for determining ICP elevations before changes in vital signs and neurologic status. Therapeutic modalities, generally aimed at reducing cerebral blood volume, brain tissue, and cerebrospinal fluid (CSF) volume, include nonpharmacologic (CSF removal, controlled hyperventilation, and elevating the patient’s head) and pharmacologic management. Mannitol and sedation are first-line agents used to lower ICP. Barbiturate coma may be beneficial in patients with elevated ICP refractory to conventional treatment. The use of prophylactic antiseizure therapy and optimal nutrition prevents significant complication. Currently, investigations are directed at discovering useful neuroprotective agents that prevent secondary neurologic injury.

Analytic Reviews : Fluid Resuscitation in Head Injury

Head injury, either alone or in combination with hy povolemic shock, is the leading cause of traumatic death in this country. Factors contributing to mortality in clude the primary impact injury as well as subsequent ischemia and hypoperfusion. Intravenous fluid therapy is required in all of these patients. However, fluid ther apy may increase brain swelling and cerebral edema formation which could lead to an increase in intracra nial pressure and a reduction in cerebral perfusion pres sure. The use of standard fluid therapy has been ques tioned, and novel therapies involving hyperosmolar and hypertonic solutions are now being investigated. This review covers recent advances in the understanding of the effects of fluid resuscitation on the brain. It also includes a brief summary of the determinants of trans- capillary fluid exchange and a review of relevant cere bral circulatory physiology and the physiological aberra tions produced by brain injury.

Definition, evaluation, and management of brain relaxation during craniotomy

The term 'brain relaxation' is routinely used to describe the size and firmness of the brain tissue during craniotomy. The status of brain relaxation is an important aspect of neuroanaesthesia practice and is relevant to the operating conditions, retraction injury, and likely patient outcomes. Brain relaxation is determined by the relationship between the volume of the intracranial contents and the capacity of the intracranial space (i.e. a content-space relationship). It is a concept related to, but distinct from, intracranial pressure. The evaluation of brain relaxation should be standardized to facilitate clinical communication and research collaboration. Both advantageous and disadvantageous effects of the various interventions for brain relaxation should be taken into account in patient care. The outcomes that matter the most to patients should be emphasized in defining, evaluating, and managing brain relaxation. To date, brain relaxation has not been reviewed specifically, and the aim of this manuscript is to discuss the current approaches to the definition, evaluation, and management of brain relaxation, knowledge gaps, and targets for future research.

Mannitol Improves Brain Tissue Oxygenation in a Model of Diffuse Traumatic Brain Injury

OBJECTIVES

Based on evidence supporting a potential relation between posttraumatic brain hypoxia and microcirculatory derangements with cell edema, we investigated the effects of the antiedematous agent mannitol on brain tissue oxygenation in a model of diffuse traumatic brain injury.

DESIGN

Experimental study.

SETTING

Neurosciences and physiology laboratories.

SUBJECTS

Adult male Wistar rats.

INTERVENTIONS

Thirty minutes after diffuse traumatic brain injury (impact-acceleration model), rats were IV administered with either a saline solution (traumatic brain injury-saline group) or 20% mannitol (1 g/kg) (traumatic brain injury-mannitol group). Sham-saline and sham-mannitol groups received no insult.

MEASUREMENTS AND MAIN RESULTS

Two series of experiments were conducted 2 hours after traumatic brain injury (or equivalent) to investigate 1) the effect of mannitol on brain edema and oxygenation, using a multiparametric magnetic resonance-based approach (n = 10 rats per group) to measure the apparent diffusion coefficient, tissue oxygen saturation, mean transit time, and blood volume fraction in the cortex and caudoputamen; 2) the effect of mannitol on brain tissue PO2 and on venous oxygen saturation of the superior sagittal sinus (n = 5 rats per group); and 3) the cortical ultrastructural changes after treatment (n = 1 per group, taken from the first experiment). Compared with the sham-saline group, the traumatic brain injury-saline group had significantly lower tissue oxygen saturation, brain tissue PO2, and venous oxygen saturation of the superior sagittal sinus values concomitant with diffuse brain edema. These effects were associated with microcirculatory collapse due to astrocyte swelling. Treatment with mannitol after traumatic brain injury reversed all these effects. In the absence of traumatic brain injury, mannitol had no effect on brain oxygenation. Mean transit time and blood volume fraction were comparable between the four groups of rats.

CONCLUSION

The development of posttraumatic brain edema can limit the oxygen utilization by brain tissue without evidence of brain ischemia. Our findings indicate that an antiedematous agent such as mannitol can improve brain tissue oxygenation, possibly by limiting astrocyte swelling and restoring capillary perfusion.

Hypertonic saline for the management of raised intracranial pressure after severe traumatic brain injury

Hyperosmolar agents are commonly used as an initial treatment for the management of raised intracranial pressure (ICP) after severe traumatic brain injury (TBI). They have an excellent adverse-effect profile compared to other therapies, such as hyperventilation and barbiturates, which carry the risk of reducing cerebral perfusion. The hyperosmolar agent mannitol has been used for several decades to reduce raised ICP, and there is accumulating evidence from pilot studies suggesting beneficial effects of hypertonic saline (HTS) for similar purposes. An ideal therapeutic agent for ICP reduction should reduce ICP while maintaining cerebral perfusion (pressure). While mannitol can cause dehydration over time, HTS helps maintain normovolemia and cerebral perfusion, a finding that has led to a large amount of pilot data being published on the benefits of HTS, albeit in small cohorts. Prophylactic therapy is not recommended with mannitol, although it may be beneficial with HTS. To date, no large clinical trial has been performed to directly compare the two agents. The best current evidence suggests that mannitol is effective in reducing ICP in the management of traumatic intracranial hypertension and carries mortality benefit compared to barbiturates. Current evidence regarding the use of HTS in severe TBI is limited to smaller studies, which illustrate a benefit in ICP reduction and perhaps mortality.

Management of raised intracranial pressure in children with traumatic brain injury

Increased intracranial pressure (ICP) is associated with worse outcome after traumatic brain injury (TBI). The current guidelines and management strategies are aimed at maintaining adequate cerebral perfusion pressure and treating elevated ICP. Despite controversies, ICP monitoring is important particularly after severe TBI to guide treatment and in developed countries is accepted as a standard of care. We provide a narrative review of the recent evidence for the use of ICP monitoring and management of ICP in pediatric TBI.

Hypertonic saline reduces cumulative and daily intracranial pressure burdens after severe traumatic brain injury

OBJECT

Increased intracranial pressure (ICP) in patients with traumatic brain injury (TBI) is associated with a higher mortality rate and poor outcome. Mannitol and hypertonic saline (HTS) have both been used to treat high ICP, but it is unclear which one is more effective. Here, the authors compare the effect of mannitol versus HTS on lowering the cumulative and daily ICP burdens after severe TBI.

METHODS

The Brain Trauma Foundation TBI-trac New York State database was used for this retrospective study. Patients with severe TBI and intracranial hypertension who received only 1 type of hyperosmotic agent, mannitol or HTS, were included. Patients in the 2 groups were individually matched for Glasgow Coma Scale score (GCS), pupillary reactivity, craniotomy, occurrence of hypotension on Day 1, and the day of ICP monitor insertion. Patients with missing or erroneous data were excluded. Cumulative and daily ICP burdens were used as primary outcome measures. The cumulative ICP burden was defined as the total number of days with an ICP of > 25 mm Hg, expressed as a percentage of the total number of days of ICP monitoring. The daily ICP burden was calculated as the mean daily duration of an ICP of > 25 mm Hg, expressed as the number of hours per day. The numbers of intensive care unit (ICU) days, numbers of days with ICP monitoring, and 2-week mortality rates were also compared between the groups. A 2-sample t-test or chi-square test was used to compare independent samples. The Wilcoxon signed-rank or Cochran-Mantel-Haenszel test was used for comparing matched samples.

RESULTS

A total of 35 patients who received only HTS and 477 who received only mannitol after severe TBI were identified. Eight patients in the HTS group were excluded because of erroneous or missing data, and 2 other patients did not have matches in the mannitol group. The remaining 25 patients were matched 1:1. Twenty-four patients received 3% HTS, and 1 received 23.4% HTS as bolus therapy. All 25 patients in the mannitol group received 20% mannitol. The mean cumulative ICP burden (15.52% [HTS] vs 36.5% [mannitol]; p = 0.003) and the mean (± SD) daily ICP burden (0.3 ± 0.6 hours/day [HTS] vs 1.3 ± 1.3 hours/day [mannitol]; p = 0.001) were significantly lower in the HTS group. The mean (± SD) number of ICU days was significantly lower in the HTS group than in the mannitol group (8.5 ± 2.1 vs 9.8 ± 0.6, respectively; p = 0.004), whereas there was no difference in the numbers of days of ICP monitoring (p = 0.09). There were no significant differences between the cumulative median doses of HTS and mannitol (p = 0.19). The 2-week mortality rate was lower in the HTS group, but the difference was not statistically significant (p = 0.56).

CONCLUSIONS

HTS given as bolus therapy was more effective than mannitol in lowering the cumulative and daily ICP burdens after severe TBI. Patients in the HTS group had significantly lower number of ICU days. The 2-week mortality rates were not statistically different between the 2 groups.

Combination of therapeutic hypothermia and other neuroprotective strategies after an ischemic cerebral insult

Abrupt deprivation of substrates to neuronal tissue triggers a number of pathological events (the “ischemic cascade”) that lead to cell death. As this is a process of delayed neuronal cell death and not an instantaneous event, several pharmacological and non-pharmacological strategies have been developed to attenuate or block this cascade. The most promising neuroprotectant so far is therapeutic hypothermia and its beneficial effects have inspired researchers to further improve its protective benefit by combining it with other neuroprotective agents. This review provides an overview of all neuroprotective strategies that have been combined with therapeutic hypothermia in rodent models of focal cerebral ischemia. A distinction is made between drugs interrupting only one event of the ischemic cascade from those mitigating different pathways and having multimodal effects. Also the combination of therapeutic hypothermia with hemicraniectomy, gene therapy and protein therapy is briefly discussed. Furthermore, those combinations that have been studied in a clinical setting are also reviewed.

Treatment of malignant brain edema and increased intracranial pressure after stroke

OPINION STATEMENT

The management of patients with large territory ischemic strokes and the subsequent development of malignant brain edema and increased intracranial pressure is a significant challenge in modern neurology and neurocritical care. These patients are at high risk of subsequent neurologic decline and are best cared for in an intensive care unit or a comprehensive stroke center with access to neurosurgical support. Risks include hemorrhagic conversion, herniation, poor functional outcome, and death. This review discusses recent advances in understanding the pathophysiology of edema formation, identifying patients at risk, current management strategies, and emerging therapies.

Capillary transit time heterogeneity and flow-metabolism coupling after traumatic brain injury

Most patients who die after traumatic brain injury (TBI) show evidence of ischemic brain damage. Nevertheless, it has proven difficult to demonstrate cerebral ischemia in TBI patients. After TBI, both global and localized changes in cerebral blood flow (CBF) are observed, depending on the extent of diffuse brain swelling and the size and location of contusions and hematoma. These changes vary considerably over time, with most TBI patients showing reduced CBF during the first 12 hours after injury, then hyperperfusion, and in some patients vasospasms before CBF eventually normalizes. This apparent neurovascular uncoupling has been ascribed to mitochondrial dysfunction, hindered oxygen diffusion into tissue, or microthrombosis. Capillary compression by astrocytic endfeet swelling is observed in biopsies acquired from TBI patients. In animal models, elevated intracranial pressure compresses capillaries, causing redistribution of capillary flows into patterns argued to cause functional shunting of oxygenated blood through the capillary bed. We used a biophysical model of oxygen transport in tissue to examine how capillary flow disturbances may contribute to the profound changes in CBF after TBI. The analysis suggests that elevated capillary transit time heterogeneity can cause critical reductions in oxygen availability in the absence of 'classic' ischemia. We discuss diagnostic and therapeutic consequences of these predictions.

Neurotrauma

Neurotrauma continues to be a significant cause of morbidity and mortality. Prevention of primary neurologic injury is a critical public health concern. Early and thorough assessment of the patient with neurotrauma with high index of suspicion of traumatic spinal cord injuries and traumatic vascular injuries requires a multidisciplinary approach involving prehospital providers, emergency physicians, neurosurgeons, and neurointensivists. Critical care management of the patient with neurotrauma is focused on the prevention of secondary injuries. Much research is still needed for potential neuroprotection therapies.

Effects of viscosity on cerebral blood flow after cardiac arrest

OBJECTIVES

To determine blood viscosity in adult comatose patients treated with mild therapeutic hypothermia after cardiac arrest and to assess the relation between blood viscosity, cerebral blood flow, and cerebral oxygen extraction.

DESIGN

Observational study.

SETTING

Tertiary care university hospital.

PATIENTS

Ten comatose patients with return of spontaneous circulation after out-of-hospital cardiac arrest.

INTERVENTION

Treatment with mild therapeutic hypothermia for 24 hours followed by passive rewarming to normothermia.

MEASUREMENTS AND MAIN RESULTS

Median viscosity at shear rate 50/s was 5.27 mPa · s (4.29-5.91 mPa · s) at admission; it remained relatively stable during the first 12 hours and decreased significantly to 3.00 mPa · s (2.72-3.58 mPa · s) at 72 hours (p < 0.001). Median mean flow velocity in the middle cerebral artery was low (27.0 cm/s [23.8-30.5 cm/s]) at admission and significantly increased to 63.0 cm/s (51.0-80.0 cm/s) at 72 hours. Median jugular bulb saturation at the start of the study was 61.5% (55.5-75.3%) and significantly increased to 73.0% (69.0-81.0%) at 72 hours. Median hematocrit was 0.41 L/L (0.36-0.44 L/L) at admission and subsequently decreased significantly to 0.32 L/L (0.27-0.35 L/L) at 72 hours. Median C-reactive protein concentration was low at admission (2.5 mg/L [2.5-6.5 mg/L]) and increased to 101 mg/L (65-113.3 mg/L) in the following hours. Median fibrinogen concentration was increased at admission 2,795 mg/L (2,503-3,565 mg/L) and subsequently further increased to 6,195 mg/L (5,843-7,368 mg/L) at 72 hours. There was a significant negative association between blood viscosity and the mean flow velocity in the middle cerebral artery (p = 0.0008).

CONCLUSIONS

Changes in blood viscosity in vivo are associated with changes in flow velocity in the middle cerebral artery. High viscosity early after cardiac arrest may reduce cerebral blood flow and may contribute to secondary brain injury. Further studies are needed to determine the optimal viscosity during the different stages of the postcardiac arrest syndrome.

Real-time hemodynamic response and mitochondrial function changes with intracarotid mannitol injection

Disruption of blood brain barrier (BBB) is used to enhance chemotherapeutic drug delivery. The purpose of this study was to understand the time course of hemodynamic and metabolic response to intraarterial (IA) mannitol infusions in order to optimize the delivery of drugs for treating brain tumors.

PRINCIPAL RESULTS

We compared hemodynamic response, EEG changes, and mitochondrial function as judged by relative changes in tissue NADH concentrations, after intracarotid (IC) infusion of equal volumes of normal saline and mannitol in our rabbit IC drug delivery model. We observed significantly greater, though transient, hyperemic response to IC infusion of mannitol compared to normal saline. Infusion of mannitol also resulted in a greater increase in tissue NADH concentrations relative to the baseline. These hemodynamic, and metabolic changes returned to baseline within 5min of mannitol injection.

CONCLUSION

Significant, though transient, changes in blood flow and brain metabolism occur with IA mannitol infusion. The observed transient hyperemia would suggest that intravenous (IV) chemotherapy should be administered either just before, or concurrent with IA mannitol injections. On the other hand, IA chemotherapy should be delayed until the peak hyperemic response has subsided.