Superior effect of hypertonic saline over mannitol to attenuate cerebral edema in a rabbit bacterial meningitis model*:

Comparison of 4.54% hypertonic saline and 20% mannitol for brain relaxation during auditory brainstem implantation in pediatric patients: a single-center retrospective observational cohort study

BACKGROUND

Mannitol is frequently utilized to achieve intracranial brain relaxation during the retrosigmoid approach for auditory brainstem implantation (ABI). Hypertonic saline (HS) is an alternative for reducing intracranial pressure; however, its application during ABI surgery remains under-investigated. We aimed to compare the efficacy and safety between HS and mannitol for maintaining brain relaxation.

METHODS

This single-center retrospective cohort study included pediatric patients undergoing ABI surgery from September 2020 to January 2022 who received only 4.54% HS or 20% mannitol for brain relaxation. The analysis involved initial doses, subsequent doses, and dosing intervals of the two hyperosmolar solutions, as well as the time elapsed from meningeal opening to the first ABI electrode placement attempt. Additionally, the analysis encompassed electrolyte testing, hemodynamic variables, urine output, blood transfusion, second surgeries, adverse events, intensive care unit length of stay, and 30-day mortality.

RESULTS

We analyzed 68 consecutive pediatric patients; 26 and 42 in the HS and mannitol groups, respectively. The HS group exhibited a reduced rate of supplementary use (7.7% vs. 31%) and lower total urine volume. Perioperative outcomes, mortality, and length of intensive care unit stay did not exhibit significant between-group differences, despite transient increases in blood sodium and chloride observed within 2 h after HS infusion.

CONCLUSIONS

In pediatric ABI surgery, as an osmotherapy for cerebral relaxation, 4.54% HS demonstrated a lower likelihood of necessitating additional supplementation than 20% mannitol. Furthermore, the diuretic effect of HS was weak and the increase in electrolyte levels during surgery was temporary and slight.

CDC Guidelines for the Prevention and Treatment of Anthrax, 2023

This report updates previous CDC guidelines and recommendations on preferred prevention and treatment regimens regarding naturally occurring anthrax. Also provided are a wide range of alternative regimens to first-line antimicrobial drugs for use if patients have contraindications or intolerances or after a wide-area aerosol release of

Bacillus anthracis spores if resources become limited or a multidrug-resistant B. anthracis strain is used (Hendricks KA, Wright ME, Shadomy SV, et al.; Workgroup on Anthrax Clinical Guidelines. Centers for Disease Control and Prevention expert panel meetings on prevention and treatment of anthrax in adults. Emerg Infect Dis 2014;20:e130687; Meaney-Delman D, Rasmussen SA, Beigi RH, et al. Prophylaxis and treatment of anthrax in pregnant women. Obstet Gynecol 2013;122:885-900; Bradley JS, Peacock G, Krug SE, et al. Pediatric anthrax clinical management. Pediatrics 2014;133:e1411-36). Specifically, this report updates antimicrobial drug and antitoxin use for both postexposure prophylaxis (PEP) and treatment from these previous guidelines best practices and is based on systematic reviews of the literature regarding 1) in vitro antimicrobial drug activity against B. anthracis; 2) in vivo antimicrobial drug efficacy for PEP and treatment; 3) in vivo and human antitoxin efficacy for PEP, treatment, or both; and 4) human survival after antimicrobial drug PEP and treatment of localized anthrax, systemic anthrax, and anthrax meningitis.

Changes from previous CDC guidelines and recommendations include an expanded list of alternative antimicrobial drugs to use when first-line antimicrobial drugs are contraindicated or not tolerated or after a bioterrorism event when first-line antimicrobial drugs are depleted or ineffective against a genetically engineered resistant

B. anthracis strain. In addition, these updated guidelines include new recommendations regarding special considerations for the diagnosis and treatment of anthrax meningitis, including comorbid, social, and clinical predictors of anthrax meningitis. The previously published CDC guidelines and recommendations described potentially beneficial critical care measures and clinical assessment tools and procedures for persons with anthrax, which have not changed and are not addressed in this update. In addition, no changes were made to the Advisory Committee on Immunization Practices recommendations for use of anthrax vaccine (Bower WA, Schiffer J, Atmar RL, et al. Use of anthrax vaccine in the United States: recommendations of the Advisory Committee on Immunization Practices, 2019. MMWR Recomm Rep 2019;68[No. RR-4]:1-14). The updated guidelines in this report can be used by health care providers to prevent and treat anthrax and guide emergency preparedness officials and planners as they develop and update plans for a wide-area aerosol release of B. anthracis.

Anthrax Meningoencephalitis and Intracranial Hemorrhage

The neurological sequelae of Bacillus anthracis infection include a rapidly progressive fulminant meningoencephalitis frequently associated with intracranial hemorrhage, including subarachnoid and intracerebral hemorrhage. Higher mortality than other forms of bacterial meningitis suggests that antimicrobials and cardiopulmonary support alone may be insufficient and that strategies targeting the hemorrhage might improve outcomes. In this review, we describe the toxic role of intracranial hemorrhage in anthrax meningoencephalitis. We first examine the high incidence of intracranial hemorrhage in patients with anthrax meningoencephalitis. We then review common diseases that present with intracranial hemorrhage, including aneurysmal subarachnoid hemorrhage and spontaneous intracerebral hemorrhage, postulating applicability of established and potential neurointensive treatments to the multimodal management of hemorrhagic anthrax meningoencephalitis. Finally, we examine the therapeutic potential of minocycline, an antimicrobial that is effective against B. anthracis and that has been shown in preclinical studies to have neuroprotective properties, which thus might be repurposed for this historically fatal disease.

Hypertonic Saline Alleviates Brain Edema After Traumatic Brain Injury via Downregulation of Aquaporin 4 in Rats

Background

Hypertonic saline (HS) has been successfully used for treatment of various forms of brain edema. Decreased expression of aquaporin (AQP)4 and pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β have been linked to edema pathogenesis. This study examined the effect of 3% HS on brain edema in a rat model of traumatic brain injury (TBI).

Material/Methods

Sprague-Dawley rats were subjected to TBI induced by a controlled cortical impactor. The HS group was injected with 3% NaCl until the end of the study period. AQP4, TNF-α, IL-1β, and caspase-3 levels were measured by Western blotting, immunohistochemistry, enzyme-linked immunosorbent assay, and quantitative real-time PCR. Brain water content was also measured. Apoptotic cells in brain tissue were detected with terminal deoxynucleotidyl transferase dUTP nick-end labeling. Brain water content decreased following treatment with 3% HS relative to the TBI group.

Results

This was accompanied by decreases in AQP4, TNF-α, and IL-1β mRNA and protein levels. TBI resulted in increases in caspase-3 mRNA expression and the number of apoptotic cells; treatment with 3% HS suppressed apoptosis as compared to the TBI group.

Conclusions

Treatment with 3% HS ameliorated TBI-induced brain edema, possibly by suppressing brain edema, pro-inflammatory cytokine expression, and apoptosis.

Hypertonic saline infusion suppresses apoptosis of hippocampal cells in a rat model of cardiopulmonary resuscitation

Hypertonic saline (HS) attenuates cerebral edema, improves microcirculation perfusion and alleviates inflammation. However, whether the beneficial effect of HS on neurological function after cardiopulmonary resuscitation (CPR) in rat model of asphyxial cardiac arrest (CA) is mediated via attenuating apoptosis of neurons is not known. We studied the neuroprotective effect of HS in rats after CA and CPR, and explored the likely underlying mechanisms. Animals were randomly assigned to 4 equal groups (n = 15 each) according to the different infusions administered during resuscitation: control (C), normal saline (NS), hypertonic saline (HS), and hydroxyethyl starch (HES) groups. NDS at 12, 24, 48 and 72 h post-ROSC in the HS group were significantly higher than those in the NS and HES groups. Western blot analysis demonstrated a significant increase in Bcl-2 expression in HS, as compared to that in the NS and HES groups. However, Bax and Caspase-3 expressions in HS were significantly lower than that in the NS and HES groups. The apoptosis rate in HS was significantly lower than that in the NS and HES groups, suggesting HS treatment during resuscitation could effectively suppress neuronal cell apoptosis in hippocampal CA1 post-ROSC and improve neuronal function.

Assessment and Care of the Critically Ill Rabbit

Rabbits have the ability to hide their signs and often present in a state of decompensatory shock. Handling can increase susceptibility to stress-induced cardiomyopathy and specific hemodynamic changes. Careful monitoring with a specific reference range is important to detect early decompensation, change the therapeutic plan in a timely manner, and assess prognostic indicators. Fluid requirements are higher in rabbits than in other small domestic mammals and can be corrected both enterally and parenterally. Critical care in rabbits can be extrapolated to many hindgut fermenters, but a specific reference range and dosage regimen need to be determined.

Central Nervous System Infections

Central nervous system (CNS) infections—i.e., infections involving the brain (cerebrum and cerebellum), spinal cord, optic nerves, and their covering membranes—are medical emergencies that are associated with substantial morbidity, mortality, or long-term sequelae that may have catastrophic implications for the quality of life of affected individuals. Acute CNS infections that warrant neurointensive care (ICU) admission fall broadly into three categories—meningitis, encephalitis, and abscesses—and generally result from blood-borne spread of the respective microorganisms. Other causes of CNS infections include head trauma resulting in fractures at the base of the skull or the cribriform plate that can lead to an opening between the CNS and the sinuses, mastoid, the middle ear, or the nasopharynx. Extrinsic contamination of the CNS can occur intraoperatively during neurosurgical procedures. Also, implanted medical devices or adjunct hardware (e.g., shunts, ventriculostomies, or external drainage tubes) and congenital malformations (e.g., spina bifida or sinus tracts) can become colonized and serve as sources or foci of infection. Viruses, such as rabies, herpes simplex virus, or polioviruses, can spread to the CNS via intraneural pathways resulting in encephalitis. If infection occurs at sites (e.g., middle ear or mastoid) contiguous with the CNS, infection may spread directly into the CNS causing brain abscesses; alternatively, the organism may reach the CNS indirectly via venous drainage or the sheaths of cranial and spinal nerves. Abscesses also may become localized in the subdural or epidural spaces. Meningitis results if bacteria spread directly from an abscess to the subarachnoid space. CNS abscesses may be a result of pyogenic meningitis or from septic emboli associated with endocarditis, lung abscess, or other serious purulent infections. Breaches of the blood–brain barrier (BBB) can result in CNS infections. Causes of such breaches include damage (e.g., microhemorrhage or necrosis of surrounding tissue) to the BBB; mechanical obstruction of microvessels by parasitized red blood cells, leukocytes, or platelets; overproduction of cytokines that degrade tight junction proteins; or microbe-specific interactions with the BBB that facilitate transcellular passage of the microorganism. The microorganisms that cause CNS infections include a wide range of bacteria, mycobacteria, yeasts, fungi, viruses, spirochaetes (e.g., neurosyphilis), and parasites (e.g., cerebral malaria and strongyloidiasis). The clinical picture of the various infections can be nonspecific or characterized by distinct, recognizable clinical syndromes. At some juncture, individuals with severe acute CNS infections require critical care management that warrants neuro-ICU admission. The implications for CNS infections are serious and complex and include the increased human and material resources necessary to manage very sick patients, the difficulties in triaging patients with vague or mild symptoms, and ascertaining the precise cause and degree of CNS involvement at the time of admission to the neuro-ICU. This chapter addresses a wide range of severe CNS infections that are better managed in the neuro-ICU. Topics covered include the medical epidemiology of the respective CNS infection; discussions of the relevant neuroanatomy and blood supply (essential for understanding the pathogenesis of CNS infections) and pathophysiology; symptoms and signs; diagnostic procedures, including essential neuroimaging studies; therapeutic options, including empirical therapy where indicated; and the perennial issue of the utility and effectiveness of steroid therapy for certain CNS infections. Finally, therapeutic options and alternatives are discussed, including the choices of antimicrobial agents best able to cross the BBB, supportive therapy, and prognosis.

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.