Elevated intraspinal pressure in traumatic spinal cord injury is a promising therapeutic target

The currently recommended management for acute traumatic spinal cord injury aims to reduce the incidence of secondary injury and promote functional recovery. Elevated intraspinal pressure (ISP) likely plays an important role in the processes involved in secondary spinal cord injury, and should not be overlooked. However, the factors and detailed time course contributing to elevated ISP and its impact on pathophysiology after traumatic spinal cord injury have not been reviewed in the literature. Here, we review the etiology and progression of elevated ISP, as well as potential therapeutic measures that target elevated ISP. Elevated ISP is a time-dependent process that is mainly caused by hemorrhage, edema, and blood-spinal cord barrier destruction and peaks at 3 days after traumatic spinal cord injury. Duraplasty and hypertonic saline may be promising treatments for reducing ISP within this time window. Other potential treatments such as decompression, spinal cord incision, hemostasis, and methylprednisolone treatment require further validation.

Effectiveness of Continuous Hypertonic Saline in Acute Ischemic Infarcts: A Radiographic and Clinical Evaluation

OBJECTIVE

The role of continuous hypertonic saline (HS) infusion in the management of malignant cerebral edema is controversial. We evaluated patients presenting with large anterior circulation territory infarcts and compared radiographic and clinical outcomes to evaluate the effects of continuous HS.

METHODS

This was a retrospective review of patients with malignant ischemic strokes who were initially managed with continuous HS versus routine medical management. Radiographic parameters of cerebral edema and clinical parameters were collected at different time intervals after admission. Rates and timing of surgery, mortality, and complications were also collected.

RESULTS

The study included 43 patients: 26 in group 1 (HS) and 17 in group 2 (no HS). Both cohorts had comparable baseline clinical and radiographic parameters. There was no difference between rates and timing of surgery, complications, and mortality. Mean midline shift was significantly greater in the HS group at interval 1 (12-36 hours, P = 0.003) and interval 2 (36-60 hours, P = 0.030), and mean change in midline shift from initial interval to interval 1 was significantly greater in the HS group (P = 0.019).

CONCLUSIONS

Despite the widespread use of continuous HS in acute ischemic infarcts, only a limited number of studies have evaluated its efficacy, and virtually no studies have studied its effect on radiographic progression and rates of decompressive surgery. Results of this study indicate that there is no benefit of continuous HS. In fact, there may be worsening of cerebral edema with administration of continuous HS. In addition, there are no differences in prevention or delay of decompressive surgery or in overall mortality.

Emergency Neuropharmacology

Management of acute neurologic disorders in the emergency department is multimodal and may require the use of medications to decrease morbidity and mortality secondary to neurologic injury. Clinicians should form an individualized treatment approach with regard to various patient specific factors. This review article focuses on the pharmacotherapy for common neurologic emergencies that present to the emergency department, including traumatic brain injury, central nervous system infections, status epilepticus, hypertensive emergencies, spinal cord injury, and neurogenic shock.

Assessment of Acute Kidney Injury in Neurologically Injured Patients Receiving Hypertonic Sodium Chloride: Does Chloride Load Matter?

Background: Increasing evidence suggests that large-volume infusions of 0.9% sodium chloride (NaCl) for resuscitation are associated with hyperchloremic metabolic acidosis, renal vasoconstriction, and increased risk of acute kidney injury (AKI). Patients with neurological injury may require hypertonic NaCl for therapeutic hypernatremia, treatment of cerebral salt wasting, hyponatremia, or elevated intracranial pressure. Consequently, this increased exposure to chloride may result in an increased risk for development of AKI. Objective: The primary aim of this study was to describe the risk for development of AKI in neurologically injured patients receiving large volumes of intravenous hypertonic NaCl. Methods: This single-center, retrospective study looked at neurologically injured patients who received hypertonic NaCl and sodium acetate. Data were collected to assess renal function, hyperchloremia, and acidemia. Receiver operating characteristic (ROC) curve analysis was used to determine the predictive association between the amount of daily and overall chloride exposure and development of AKI. Results: A total of 301 patients were screened, and of those, 142 were included. Of the 142 patients included, 13% developed AKI, and 38% developed hyperchloremia. Additionally, 32% of patients were switched from NaCl to sodium acetate after an average of 3.4 ± 1.5 days of NaCl therapy. The ROC curve demonstrated that if patients received greater than 2055 mEq of chloride over 7 days, they were more likely to develop AKI (sensitivity 72%, specificity 70%; P = 0.002; area under the curve = 0.7). Conclusion and Relevance: Neurologically injured patients receiving hypertonic sodium therapy with a high chloride load are at risk of developing hyperchloremia and AKI.

Use of intraosseous hypertonic saline in critically ill patients

BACKGROUND

Rapid administration of hypertonic saline 23.4% is crucial in treatment of herniation syndromes. Hypertonic 23.4% saline must be administered via a central line. In cases where central line access is difficult to obtain and leads to delay in therapy, placement of intraosseous access can be lifesaving.

MAIN BODY

The purpose of this case series is to describe the use of intraosseous administration of 23.4% saline in critically ill patients and to assess feasibility.

CONCLUSION

Intraosseous administration of 23.4% saline in 6 adult patients with neurological emergencies was feasible and should be considered in cases where obtaining intravenous access is time consuming.

Variable saline resuscitation in a murine model of combined traumatic brain injury and haemorrhage

BACKGROUND

Resuscitation strategies for combined traumatic brain injury (TBI) with haemorrhage in austere environments are not fully established. Our aim was to establish the effects of various saline concentrations in a murine model of combined TBI and haemorrhage, and identify an effective resuscitative strategy for the far-forward environment.

METHODS

Male C57BL/6 mice underwent closed head injury and subjected to controlled haemorrhage to a systolic blood pressure of 25 mmHg via femoral artery cannulation for 60 min. Mice were resuscitated with a fixed volume bolus or variable volumes of fluid to achieve a systolic blood pressure goal of 80 mmHg with 0.9% saline, 3% saline, 0.1-mL bolus of 23.4% saline, or a 0.1-mL bolus of 23.4% saline followed by 0.9% saline (23.4+).

RESULTS

23.4% saline and 23.4+ resulted in higher mortality at 6 h compared to 0.9% saline. Use of 3% saline required less volume to achieve targeted resuscitation, did not affect survival, and did not exacerbate post-traumatic inflammation. While 23.4+ resuscitation utilized lower volume, it resulted in hypernatremia, azotemia, and elevated systemic pro-inflammatory cytokines. All groups except 3% saline demonstrated progression of neuron damage, with cerebral oedema highest with 0.9% saline.

CONCLUSIONS

3% saline demonstrated favourable balance of survival, blood pressure restoration, minimization of inflammation, and prevention of ongoing neurologic injury without contributing to significant physiologic derangements. 23.4% saline administration may not be appropriate in the setting of concomitant hypotension.

Pharmacotherapy Pearls for Emergency Neurological Life Support

The appropriate use of medications during Emergency Neurological Life Support (ENLS) is essential to optimize patient care. Important considerations when choosing the appropriate agent include the patient's organ function and medication allergies, potential adverse drug effects, drug interactions and critical illness and aging pathophysiologic changes. Critical medications used during ENLS include hyperosmolar therapy, anticonvulsants, antithrombotics, anticoagulant reversal and hemostatic agents, anti-shivering agents, neuromuscular blockers, antihypertensive agents, sedatives, vasopressors and inotropes, and antimicrobials. This article focuses on the important pharmacokinetic and pharmacodynamics characteristics, advantages and disadvantages and clinical pearls of these therapies, providing practitioners with essential drug information to optimize pharmacotherapy in acutely ill neurocritical care patients.

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 Effects of Clinically Relevant Hypertonic Saline and Conivaptan Administration on Ischemic Stroke

Cerebral edema after stroke is associated with poor neurological outcomes. Current therapies are limited to osmotic agents, such as hypertonic saline (HS), which reduce intracranial pressure. Although studies have demonstrated edema reductions following HS, tissue survival has not been thoroughly examined. Additionally, the efficacy of promising pharmacological agents has not been evaluated for synergy with osmotic agents. Conivaptan is an FDA-approved vasopressin receptor antagonist that may exert both osmotic and anti-inflammatory effects. In this study, rats were subjected to middle cerebral artery occlusion prior to treatment with 5 % HS bolus +5 % HS maintenance (HS), conivaptan alone (Con), conivaptan +5 % HS maintenance (Con + HS), or conivaptan +5 % HS bolus +5 % maintenance (Con + HSb). Treatments were initiated at six (Early) or 24 h (Late) following stroke and rats were euthanized at 48 h to evaluate infarct volume, brain edema, and microglia/macrophage activation. Infarct volume and brain edema in the Early HS, Early Con, and Late HS groups were significantly reduced compared with controls. Interestingly, only the Early Con group demonstrated reduced microglia/macrophage activation. These data suggest an anti-inflammatory mechanism for conivaptan and provide support for a multipronged approach combining osmotic agents with compounds that inhibit the neuroinflammatory response to stroke.

The Use of Mannitol and Hypertonic Saline Therapies in Patients with Elevated Intracranial Pressure: A Review of the Evidence

Patients with increased intracranial pressure generally require pharmacologic therapies and often more definitive treatments, such as surgical intervention. The overall goal of these interventions is to maintain or re-establish adequate cerebral blood flow and prevent herniation. Regardless of the cause of increased intracranial pressure, osmotherapy is considered the mainstay of medical therapy, and should be administered as soon as possible. This article reviews the history of hyperosmolar and hypertonic therapies, the Monro-Kellie hypothesis, and types of cerebral edema. Pharmacologic properties, clinical applications, complications, recommended monitoring during therapy, and risks versus benefits are also discussed.

Method of Hypertonic Saline Administration: Effects on Osmolality in Traumatic Brain Injury Patients

Hypertonic saline (HTS) is an effective therapy for reducing intracranial pressure (ICP). The ideal method of administration is unknown. The purpose of this study was to evaluate the method of HTS infusion and time to goal osmolality. A retrospective cohort analysis was conducted in severe TBI patients with ICP monitoring in place who received 2 doses of HTS. Patients were divided into bolus versus continuous infusion HTS cohorts. The primary outcome was median time to goal osmolality. Secondary outcomes included percentage of patients reaching goal osmolality, percent time at goal osmolality, mean cerebral perfusion pressure (CPP) and ICP, ICU length of stay, and mortality. Safety outcomes included rates of hyperchloremia, hypernatremia, and acute kidney injury (AKI). 162 patients were included with similar baseline characteristics. Time to goal osmolality was similar between cohorts (bolus 9.78h vs. continuous 11.4h, p=0.817). A significant difference in the percentage of patients reaching goal osmolality favoring the continuous group was found (93.9% vs 73.3%, p=0.003). The continuous group was maintained at goal osmolality for a higher percentage of osmolality values after reaching goal (80% vs. 50%, p=0.032). No difference was seen in CPP, ICP, length of stay and mortality. Rates of hypernatremia were similar, but significant higher rates of hyperchloremia (0.77vs 1.58 events per HTS days, p<0.001) and AKI (0% vs 12.9%, p=0.025) were observed in the continuous cohort. Although no difference in time to goal osmolality was observed, continuous HTS was associated with a higher percentage of patients achieving goal osmolality.

Longitudinal enlargement of the lesion after spinal cord injury in the rat: a consequence of malignant edema?

STUDY DESIGN

Experimental animal study.

OBJECTIVES

Quantitative analysis of secondary changes in lesion size after experimental spinal cord injury (SCI) in the rat, with special emphasis to the formation of dorsal column lesions.

SETTING

Slovakia.

METHODS

After SCI in the rat, animals survived for different periods ranging from 5 min to 7 days. Their whole spinal cords were cut transversally into 1 mm thick slabs. On each slab, the lesion profile was outlined. The overall shape of the lesion was reconstructed from a series of consecutive profiles and its length was measured.

RESULTS

Immediately after injury, a spindle-shaped hemorrhagic contusive lesion was observed, with the length of ~15 mm. After a quiescent phase lasting for at least 1 h, there was a dramatic secondary enlargement of the lesion and its length increased up to 40 mm between 1 and 48 h. The fully developed lesion consisted of the spindle-shaped epicenter and long cranial and caudal protrusions located in the midline between dorsal columns.

CONCLUSION

We propose that secondary enlargement of the lesion can be explained by posttraumatic swelling. The expanding tissues are pushed out in longitudinal axis along the mechanically weakest parts of the spinal cord. Additional data that support this hypothesis are presented. Our findings indicate that malignant posttraumatic edema might have an important role in pathomechanisms of secondary injury after SCI.

Emergency Neurological Life Support: Pharmacotherapy

The appropriate use of medications during Emergency Neurological Life Support (ENLS) is essential to optimize patient care. Important considerations when choosing the appropriate agent include the patient's organ function and medication allergies, potential adverse drug effects, drug interactions, and critical illness and aging pathophysiologic changes. Critical medications used during ENLS include hyperosmolar therapy, anticonvulsants, antithrombotics, anticoagulant reversal and hemostatic agents, anti-shivering agents, neuromuscular blockers, antihypertensive agents, sedatives, vasopressors and inotropes, and antimicrobials. This article focuses on the important pharmacokinetic and pharmacodynamics characteristics, advantages and disadvantages, and clinical pearls of these therapies, providing practitioners with essential drug information to optimize pharmacotherapy in acutely ill neurocritical care patients.

Minimally invasive surgery of the anterior skull base: transorbital approaches

Minimally invasive approaches are becoming increasingly popular to access the anterior skull base. With interdisciplinary cooperation, in particular endonasal endoscopic approaches have seen an impressive expansion of indications over the past decades. The more recently described transorbital approaches represent minimally invasive alternatives with a differing spectrum of access corridors. The purpose of the present paper is to discuss transorbital approaches to the anterior skull base in the light of the current literature. The transorbital approaches allow excellent exposure of areas that are difficult to reach like the anterior and posterior wall of the frontal sinus; working angles may be more favorable and the paranasal sinus system can be preserved while exposing the skull base. Because of their minimal morbidity and the cosmetically excellent results, the transorbital approaches represent an important addition to established endonasal endoscopic and open approaches to the anterior skull base. Their execution requires an interdisciplinary team approach.

Infarct volume after hyperacute infusion of hypertonic saline in a rat model of acute embolic stroke

INTRODUCTION

Hypertonic saline (HS) can treat cerebral edema arising from a number of pathologic conditions. However, physicians are reluctant to use it during the first 24 h after stroke because of experimental evidence that it increases infarct volume when administered early after reperfusion. Here, we determined the effect of HS on infarct size in an embolic clot model without planned reperfusion.

METHODS

A clot was injected into the internal carotid artery of male Wistar rats to reduce perfusion in the middle cerebral artery territory to less than 40 % of baseline, as monitored by laser-Doppler flowmetry. After 25 min, rats were randomized to receive 10 mL/kg of 7.5 % HS (50:50 chloride:acetate) or normal saline (NS) followed by a 0.5 mL/h infusion of the same solution for 22 h.

RESULTS

Infarct volume was similar between NS and HS groups (in mm(3): cortex 102 ± 65 mm(3) vs. 93 ± 49 mm(3), p = 0.72; caudoputamenal complex 15 ± 9 mm(3) vs. 21 ± 14, p = 0.22; total hemisphere 119 ± 76 mm(3) vs. 114 ± 62, p = 0.88, respectively). Percent water content was unchanged in the infarcted hemisphere (NS 81.6 ± 1.5 %; HS 80.7 ± 1.3 %, p = 0.16), whereas the HS-treated contralateral hemisphere was significantly dehydrated (NS 79.4 ± 0.8 %; HS 77.5 ± 0.8 %, p < 0.01).

CONCLUSIONS

HS reduced contralateral hemispheric water content but did not affect ipsilateral brain water content when compared to NS. Infarct volume was unaffected by HS administration at all evaluated locations.

Hypertonic saline in elevated intracranial pressure: past, present, and future

Hypertonic Saline (HS) has been a proven and effective therapy and a safe alternative to mannitol in patients with increase intracranial pressure (ICP). We hereby present a case of 25-year-old women with intracranial bleed secondary to right parietal arteriovenous malformation. Patient underwent surgery for evacuation of hematoma and resection of arteriovenous malformation. Post- operative course was complicated by recurrent episodes of elevated ICP. She received total of 17 doses of 23.4% HS and 30 doses of mannitol with good outcome. Despite reluctance from some clinicians to use HS, hypertonic saline seems to be a safe and effective therapy.

Intravenous hypertonic saline use in the pediatric emergency department

OBJECTIVES

The objective of this study was to describe the use, dosing, and administration of intravenous hypertonic saline (IHS) use in a pediatric emergency department.

METHODS

This was a retrospective chart review of patients 0 to 18 years receiving IHS as part of their management in a pediatric ED with an annual volume of more than 50,000 visits.

RESULTS

Over 4 years, 56 patients received IHS as part of their management in the emergency department. Clinical scenarios for IHS administration included traumatic brain injury with concern for increased intracranial pressure in 19 patients (34%), diabetic ketoacidosis with altered mental status in 18 (32%), hyponatremia without seizure activity in 6 (10.7%), hyponatremic seizure in 3 (5.4%), and altered mental status secondary to a nontraumatic, non-diabetic ketoacidosis cause in 10 (17.9%). The median age of the patients was 11.3 years (interquartile range, 6-13.9 years) receiving a median dose of 4.1 mL/kg (interquartile range, 3.08-5 mL/kg) of IHS. The median time for administration of the IHS was 17 minutes, with 87% of doses given via peripheral intravenous catheters. Approximately one fourth (26.8%) of patients received their dose in 10 minutes or less, with 7.2% of patients receiving a bolus of IHS in 3 minutes or less. We found no evidence of adverse effects.

CONCLUSIONS

Intravenous hypertonic saline use is increasing within the pediatric emergency department. Within this institution, it is most frequently used at a dosing range of 3 to 5 mL/kg and does not require central venous access for rapid infusion.

Hypertonic saline reduces lipopolysaccharide-induced mouse brain edema through inhibiting aquaporin 4 expression

INTRODUCTION

Three percent sodium chloride (NaCl) treatment has been shown to reduce brain edema and inhibited brain aquaporin 4 (AQP4) expression in bacterial meningitis induced by Escherichia coli. Lipopolysaccharide (LPS) is the main pathogenic component of E. coli. We aimed to explore the effect of 3% NaCl in mouse brain edema induced by LPS, as well as to elucidate the potential mechanisms of action.

METHODS

Three percent NaCl was used to treat cerebral edema induced by LPS in mice in vivo. Brain water content, IL-1β, TNFα, immunoglobulin G (IgG), AQP4 mRNA and protein were measured in brain tissues. IL-1β, 3% NaCl and calphostin C (a specific inhibitor of protein kinase C) were used to treat the primary astrocytes in vitro. AQP4 mRNA and protein were measured in astrocytes. Differences in various groups were determined by one-way analysis of variance.

RESULTS

Three percent NaCl attenuated the increase of brain water content, IL-1β, TNFα, IgG, AQP4 mRNA and protein in brain tissues induced by LPS. Three percent NaCl inhibited the increase of AQP4 mRNA and protein in astrocytes induced by IL-1β in vitro. Calphostin C blocked the decrease of AQP4 mRNA and protein in astrocytes induced by 3% NaCl in vitro.

CONCLUSIONS

Osmotherapy with 3% NaCl ameliorated LPS-induced cerebral edema in vivo. In addition to its osmotic force, 3% NaCl exerted anti-edema effects possibly through down-regulating the expression of proinflammatory cytokines (IL-1β and TNFα) and inhibiting the expression of AQP4 induced by proinflammatory cytokines. Three percent NaCl attenuated the expression of AQP4 through activation of protein kinase C in astrocytes.

Hypertonic saline: a change of practice

BACKGROUND

This practice development review describes how the introduction of hypertonic saline in the treatment of raised intracranial pressure was brought about in one critical care unit. It considers the need for staff education and patient safety as an integral part of the change process.

AIM

The aim was to review making a practice change, using Lewin's three step change model and describes possible pitfalls in the process and ways of overcoming or avoiding them.

METHODS

The inclusion criterion for critiqued literature was: Worldwide, English language studies from the last 26 years. Exclusion was articles from non-academically recognized sources. The search was limited to primary and empirical sources.

DISCUSSION

This article uses Lewin's change model to describe driving and restraining forces, highlighting potential problems and suggesting ways in which they can be overcome when implementing a change in practice. Critical to the success of any change is the importance of evaluation, and suitable methods of evaluating the change are also suggested.

RELEVANCE TO CLINICAL PRACTICE

Critical care and neurosurgical nurses need to be aware of the potentially serious side effects, actions and correct methods of administration of hypertonic saline to ensure its safe use and ensure patient safety. Effects and side effects of hypertonic saline are described, highlighting the need for care in introducing such agents into a clinical area. The methodology used was an electronic search. The change in practice relates to the introduction of hypertonic saline, but could be adapted for any change in clinical nursing practice.

Hypertonic saline for treating raised intracranial pressure: literature review with meta-analysis

Object

Currently, mannitol is the recommended first choice for a hyperosmolar agent for use in patients with elevated intracranial pressure (ICP). Some authors have argued that hypertonic saline (HTS) might be a more effective agent; however, there is no consensus as to appropriate indications for use, the best concentration, and the best method of delivery. To answer these questions better, the authors performed a review of the literature regarding the use of HTS for ICP reduction.

Methods

A PubMed search was performed to locate all papers pertaining to HTS use. This search was then narrowed to locate only those clinical studies relating to the use of HTS for ICP reduction.

Results

A total of 36 articles were selected for review. Ten were prospective randomized controlled trials (RCTs), 1 was prospective and nonrandomized, 15 were prospective observational trials, and 10 were retrospective trials. The authors did not distinguish between retrospective observational studies and retrospective comparison trials. Prospective studies were considered observational if the effects of a treatment were evaluated over time but not compared with another treatment.

Conclusions

The available data are limited by low patient numbers, limited RCTs, and inconsistent methods between studies. However, a greater part of the data suggest that HTS given as either a bolus or continuous infusion can be more effective than mannitol in reducing episodes of elevated ICP. A meta-analysis of 8 prospective RCTs showed a higher rate of treatment failure or insufficiency with mannitol or normal saline versus HTS.

Effect of osmotic agents on regional cerebral blood flow in traumatic brain injury

PURPOSE

Cerebral blood flow (CBF) is reduced after severe traumatic brain injury (TBI) with considerable regional variation. Osmotic agents are used to reduce elevated intracranial pressure (ICP), improve cerebral perfusion pressure, and presumably improve CBF. Yet, osmotic agents have other physiologic effects that can influence CBF. We sought to determine the regional effect of osmotic agents on CBF when administered to treat intracranial hypertension.

MATERIALS AND METHODS

In 8 patients with acute TBI, we measured regional CBF with positron emission tomography before and 1 hour after administration of equi-osmolar 20% mannitol (1 g/kg) or 23.4% hypertonic saline (0.686 mL/kg) in regions with focal injury and baseline hypoperfusion (CBF <25 mL per 100 g/min).

RESULTS

The ICP fell (22.4 ± 5.1 to 15.7 ± 7.2 mm Hg, P = .007), and cerebral perfusion pressure rose (75.7 ± 5.9 to 81.9 ± 10.3 mm Hg, P = .03). Global CBF tended to rise (30.9 ± 3.7 to 33.1 ± 4.2 mL per 100 g/min, P = .07). In regions with focal injury, baseline flow was 25.7 ± 9.1 mL per 100 g/min and was unchanged; in hypoperfused regions (15% of regions), flow rose from 18.6 ± 5.0 to 22.4 ± 6.4 mL per 100 g/min (P < .001). Osmotic therapy reduced the number of hypoperfused brain regions by 40% (P < .001).

CONCLUSION

Osmotic agents, in addition to lowering ICP, improve CBF to hypoperfused brain regions in patients with intracranial hypertension after TBI.

Hypertonic saline and mannitol therapy in critical care neurology

Osmotic agents play a vital role in the reduction of elevated intracranial pressure and treatment of cerebral edema in Neurologic critical care. Both mannitol and hypertonic saline reduce cerebral edema in many clinical syndromes, yet there is controversy over agent selection, timing, and dosing regimens. Despite the lack of randomized, controlled trials, our knowledge base on the appropriate clinical use of osmotic agents continues to expand. This review will summarize the evidence for the use of mannitol and hypertonic saline in a variety of disease states causing cerebral edema, as well as outlining monitoring and safety considerations.

Contemporary pharmacologic issues in the management of traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability in the United States. While there are no pharmacotherapeutic options currently available for attenuating the neurologic injury cascade after TBI, numerous pharmacologic issues are encountered in these critically ill patients. Adequate fluid resuscitation, reversal of coagulopathy, maintenance of cerebral perfusion, and treatment of intracranial hypertension are common interventions early in the treatment of TBI. Other deleterious complications such as venous thromboembolism, extremes in glucose concentrations, and stress-related mucosal disease should be anticipated and avoided. Early provision of nutrition and prevention of drug or alcohol withdrawal are also cornerstones of routine care in TBI patients. Prevention of infections and seizures may also be helpful. Clinicians caring for TBI patients should be familiar with the pharmacologic issues typical of this vulnerable population in order to develop optimal strategies of care to anticipate and prevent common complications.

Hypertonic saline ameliorates cerebral edema through downregulation of aquaporin-4 expression in the astrocytes

Osmotherapy with 10% hypertonic saline (HS) alleviates cerebral edema through osmotic force. Aquaporin-4 (AQP4) has been reported to be implicated in the pathogenesis of cerebral edema resulting from a variety of brain injury. This study aimed to determine if 10% hypertonic saline ameliorates cerebral edema through downregulation of AQP4 expression in the perivascular astrocytes in the ischemic cerebral edema. Adult male Sprague-Dawley (SD) rats were subjected to permanent right-sided middle cerebral artery occlusion (MCAO) and treated with a continuous i.v. infusion of 10% HS. Brain water content (BWC) analyzed by wet-to-dry ratios in the ischemic hemisphere of SD rats was attenuated after 10% HS treatment. This was coupled with the reduction of neuronal apoptosis in the peri-ischemic brain tissue. Concomitantly, downregulated expression of AQP4 in the perivascular astrocytes after 10% HS treatment was observed. Our results suggest that in addition to its osmotic force, 10% HS exerts anti-edema effects possibly through downregulation of AQP4 expression in the perivascular astrocytes. The reduction of brain edema after 10% HS administration can prevent ischemic brain damage.

Current trends in resuscitation strategy for the multiply injured patient

The ideal resuscitation strategy for multiply injured patients remains a topic of ongoing debate. At present, no consensus has been reached on the ideal fluid for early resuscitation and on the threshold for blood product transfusions. The concept of "permissive hypotension" for bleeding trauma patients furthermore contributes to the controversy in the field, particularly as it relates to blunt trauma and to patients with associated head injuries. Finally, postinjury coagulopathy is a poorly defined entity, and current resuscitation strategies lack strong evidence-based scientific support. This review article provides a brief overview of the existing resuscitation protocols for multiply injured patients, including ATLS and "damage control", and will address developing controversies in the field.

Hypertonic saline attenuates cord swelling and edema in experimental spinal cord injury: a study utilizing magnetic resonance imaging

OBJECTIVE

To use magnetic resonance imaging (MRI) to characterize secondary injury immediately after spinal cord injury (SCI), and to show the effect of hypertonic saline on MRI indices of swelling, edema, and hemorrhage within the cord.

DESIGN

A prospective, randomized, placebo-controlled study.

SETTING

Research laboratory.

SUBJECTS

Twelve adult Long-Evans female rats.

INTERVENTIONS

Rats underwent a unilateral 12.5 mm SCI at vertebral level C5. Animals were administered 0.9% NaCl (n = 6) or 5% NaCl (n = 6) at 1.4 mL/kg intravenously every hour starting 30 minutes after SCI. Immediately after SCI, rats were placed in a 4.7T Bruker MRI system and images were obtained continuously for 8 hours using a home-built transmitter/receiver 3 cm Helmholtz coil. Rats were killed 8 hours after SCI.

MEASUREMENTS AND MAIN RESULTS

Quantification of cord swelling and volumes of hypointense and hyperintense signal within the lesion were determined from MRI. At 36 minutes after SCI, significant swelling of the spinal cord at the lesion center and extending rostrally and caudally was demonstrated by MRI. Also, at this time point, a hypointense core was identified on T1, PD, and T2 weighted images. Over time this hypointense core reduced in size and in some animals was no longer visible by 8 hours after SCI, although histopathology demonstrated presence of red blood cells. A prominent ring of T2-weighted image hyperintensity, characteristic of edema, surrounded the hypointense core. At the lesion center, this rim of edema occupied the entire unilateral injured cord and in all animals extended to the contralateral side. Administration of HS resulted in increased serum [Na], attenuation of cord swelling, and decreased volume of hypointense core and edema at the last time points.

CONCLUSIONS

We were able to use MRI to detect rapid and acute changes in the evolution of tissue pathophysiology, and show potentially beneficial effects of hypertonic saline in acute cervical SCI.

The relation between the incidence of hypernatremia and mortality in patients with severe traumatic brain injury

Introduction

The study was aimed at verifying whether the occurrence of hypernatremia during the intensive care unit (ICU) stay increases the risk of death in patients with severe traumatic brain injury (TBI). We performed a retrospective study on a prospectively collected database including all patients consecutively admitted over a 3-year period with a diagnosis of TBI (post-resuscitation Glasgow Coma Score ≤ 8) to a general/neurotrauma ICU of a university hospital, providing critical care services in a catchment area of about 1,200,000 inhabitants.

Methods

Demographic, clinical, and ICU laboratory data were prospectively collected; serum sodium was assessed an average of three times per day. Hypernatremia was defined as two daily values of serum sodium above 145 mmol/l. The major outcome was death in the ICU after 14 days. Cox proportional-hazards regression models were used, with time-dependent variates designed to reflect exposure over time during the ICU stay: hypernatremia, desmopressin acetate (DDAVP) administration as a surrogate marker for the presence of central diabetes insipidus, and urinary output. The same models were adjusted for potential confounding factors.

Results

We included in the study 130 TBI patients (mean age 52 years (standard deviation 23); males 74%; median Glasgow Coma Score 3 (range 3 to 8); mean Simplified Acute Physiology Score II 50 (standard deviation 15)); all were mechanically ventilated; 35 (26.9%) died within 14 days after ICU admission. Hypernatremia was detected in 51.5% of the patients and in 15.9% of the 1,103 patient-day ICU follow-up. In most instances hypernatremia was mild (mean 150 mmol/l, interquartile range 148 to 152). The occurrence of hypernatremia was highest (P = 0.003) in patients with suspected central diabetes insipidus (25/130, 19.2%), a condition that was associated with increased severity of brain injury and ICU mortality. After adjustment for the baseline risk, the incidence of hypernatremia over the course of the ICU stay was significantly related with increased mortality (hazard ratio 3.00 (95% confidence interval: 1.34 to 6.51; P = 0.003)). However, DDAVP use modified this relation (P = 0.06), hypernatremia providing no additional prognostic information in the instances of suspected central diabetes insipidus.

Conclusions

Mild hypernatremia is associated with an increased risk of death in patients with severe TBI. In a proportion of the patients the association between hypernatremia and death is accounted for by the presence of central diabetes insipidus.