Modulation of Peroxynitrite Reduces Norepinephrine Requirements in Ovine MRSA Septic Shock

The efficacy of dexmedetomidine for septic shock: A meta-analysis of randomized controlled trials

INTRODUCTION

The efficacy of dexmedetomidine was elusive for septic shock. This meta-analysis aimed to explore the efficacy of dexmedetomidine for septic shock.

METHODS

PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases have been searched through October 2022 and we included randomized controlled trials reporting the effect of dexmedetomidine in patients with septic shock.

RESULTS

Five randomized controlled trials were included in the meta-analysis. Compared with control group for septic shock, dexmedetomidine treatment was able to substantially decrease Sequential Organ Failure Assessment score (mean difference [MD] = -0.99; 95% confidence interval [CI] = -1.14 to -0.84; P < .00001) and duration of mechanical ventilation (MD = -0.90; 95% CI = -1.27 to -0.54; P < .00001), but showed no obvious influence on morality at 28 days (odds ratio = 0.79; 95% CI = 0.38 to 1.66; P = 054), hospital mortality (odds ratio = 0.66; 95% CI = 0.35 to 1.24; P = .20) or intensive care unit length of stay (MD = -1.47; 95% CI = -4.60 to 1.66; P = .36).

CONCLUSIONS

Dexmedetomidine administration may help treat patients with septic shock.

GENDER-RELATED VARIATIONS IN PATHOPHYSIOLOGICAL RESPONSES TO METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS PNEUMONIA AND SEPSIS

ABSTRACT

In preclinical studies, the protective effects of female sex hormones and the immunosuppressive effects of male sex hormones were demonstrated. However, gender-related differences in multiorgan failure and mortality in clinical trials have not been consistently explained. This study aims to investigate gender-related differences in the development and progression of sepsis using a clinically relevant ovine model of sepsis. Adult Merino male (n=7) and female (n=7) sheep were surgically prepared with multiple catheters before the study. To induce sepsis, bronchoscopy instilled methicillin-resistant Staphylococcus aureus into sheep's lungs. The time from the bacterial inoculation until the modified Quick Sequential Organ Failure Assessment (q-SOFA) score became positive was measured and analyzed primarily. We also compared the SOFA score between these male and female sheep over time. Survival, hemodynamic changes, the severity of pulmonary dysfunction, and microvascular hyperpermeability were also compared. The time from the onset of bacterial inoculation to the positive q-SOFA in male sheep was significantly shorter than in female sheep. Mortality was not different between these sheep (14% vs. 14%). There were no significant differences in hemodynamic changes and pulmonary function between the two groups at any time point. Similar changes in hematocrit, urine output, and fluid balance were observed between females and males. The present data indicate that the onset of multiple organ failure and progression of sepsis is faster in male sheep than in female sheep, even though the severity of cardiopulmonary function is comparable over time. Further studies are warranted to validate the above results.

Mesenchymal stem cell-derived exosomes for treatment of sepsis

Introduction

The pathogenesis of sepsis is an imbalance between pro-inflammatory and anti-inflammatory responses. At the onset of sepsis, the lungs are severely affected, and the injury progresses to acute respiratory distress syndrome (ARDS), with a mortality rate of up to 40%. Currently, there is no effective treatment for sepsis. Cellular therapies using mesenchymal stem cells (MSCs) have been initiated in clinical trials for both ARDS and sepsis based on a wealth of pre-clinical data. However, there remains concern that MSCs may pose a tumor risk when administered to patients. Recent pre-clinical studies have demonstrated the beneficial effects of MSC-derived extracellular vesicles (EVs) for the treatment of acute lung injury (ALI) and sepsis.

Methods

After recovery of initial surgical preparation, pneumonia/sepsis was induced in 14 adult female sheep by the instillation of Pseudomonas aeruginosa (~1.0×1011 CFU) into the lungs by bronchoscope under anesthesia and analgesia. After the injury, sheep were mechanically ventilated and continuously monitored for 24 h in a conscious state in an ICU setting. After the injury, sheep were randomly allocated into two groups: Control, septic sheep treated with vehicle, n=7; and Treatment, septic sheep treated with MSC-EVs, n=7. MSC-EVs infusions (4ml) were given intravenously one hour after the injury.

Results

The infusion of MSCs-EVs was well tolerated without adverse events. PaO2/FiO2 ratio in the treatment group tended to be higher than the control from 6 to 21 h after the lung injury, with no significant differences between the groups. No significant differences were found between the two groups in other pulmonary functions. Although vasopressor requirement in the treatment group tended to be lower than in the control, the net fluid balance was similarly increased in both groups as the severity of sepsis progressed. The variables reflecting microvascular hyperpermeability were comparable in both groups.

Conclusion

We have previously demonstrated the beneficial effects of bone marrow-derived MSCs (10×106 cells/kg) in the same model of sepsis. However, despite some improvement in pulmonary gas exchange, the present study demonstrated that EVs isolated from the same amount of bone marrow-derived MSCs failed to attenuate the severity of multiorgan dysfunctions.

Effects of Collagen Antibacterial Functional Dressing plus Continuous Nursing on Lower Extremity Skin Injury Caused by Norepinephrine in Patients with Septic Shock

Background

This study was designed to explore the effects of collagen antibacterial functional dressing plus continuous care on norepinephrine-induced lower extremity skin injury in patients with septic shock.

Methods

In this prospective, randomized, controlled study, 120 patients with septic shock receiving norepinephrine in our hospital from February 2020 to February 2021 were recruited. All the enrollments were randomized into the experimental group (n = 60) and the control group (n = 60). The control group received continuous care, while the experimental group additionally received collagen antibacterial functional dressing. Outcome measures included skin sensation scores, incidence of lower extremity skin injuries, recovery time, inflammatory factor levels, and care satisfaction.

Results

Collagen antibacterial functional dressing plus continuous care resulted in significantly lower skin sensation scores and a lower incidence of skin injuries versus continuous care alone. Patients in the experimental group had faster recovery of lower extremity skin injury than those in the control group. Collagen antibacterial functional dressing plus continuous care was associated with significantly lower levels of inflammatory factors and a higher satisfaction rate than continuous care alone.

Conclusion

Collagen antibacterial functional dressing plus continuous care improves the local skin condition of patients with septic shock receiving norepinephrine, regulates the levels of inflammatory factors, reduces the risk of skin injuries, and enhances care satisfaction.

Advantages and Disadvantages of Using Small and Large Animals in Burn Research: Proceedings of the 2021 Research Special Interest Group

Multiple animal species and approaches have been used for modeling different aspects of burn care, with some strategies considered more appropriate or translatable than others. On April 15, 2021, the Research Special Interest Group of the American Burn Association held a virtual session as part of the agenda for the annual meeting. The session was set up as a pro/con debate on the use of small versus large animals for application to four important aspects of burn pathophysiology: burn healing/conversion; scarring; inhalation injury; and sepsis. For each of these topics, 2 experienced investigators (one each for small and large animal models) described the advantages and disadvantages of using these preclinical models. The use of swine as a large animal model was a common theme due to anatomic similarities with human skin. The exception to this was a well-defined ovine model of inhalation injury; both of these species have larger airways which allow for incorporation of clinical tools such as bronchoscopes. However, these models are expensive and demanding from labor and resource standpoints. Various strategies have been implemented to make the more inexpensive rodent models appropriate for answering specific questions of interest in burns. Moreover, modelling burn-sepsis in large animals has proven difficult. It was agreed that the use of both small and large animal models have merit for answering basic questions about the responses to burn injury. Expert opinion and the ensuing lively conversations are summarized herein, which we hope will help inform experimental design of future research.

Modulation of oxidative and nitrosative stress attenuates microvascular hyperpermeability in ovine model of Pseudomonas aeruginosa sepsis

In sepsis, microvascular hyperpermeability caused by oxidative/nitrosative stress (O&NS) plays an important role in tissue edema leading to multi-organ dysfunctions and increased mortality. We hypothesized that a novel compound R-107, a modulator of O&NS, effectively ameliorates the severity of microvascular hyperpermeability and preserves multi-organ function in ovine sepsis model. Sepsis was induced in twenty-two adult female Merino sheep by intravenous infusion of Pseudomonas aeruginosa (PA) (1 × 10¹⁰ CFUs). The animals were allocated into: 1) Control (n = 13): intramuscular injection (IM) of saline; and 2) Treatment (n = 9): IM of 50 mg/kg R-107. The treatment was given after the PA injection, and monitored for 24-h. R-107 treatment significantly reduced fluid requirement (15-24 h, P < 0.05), net fluid balance (9-24 h, P < 0.05), and water content in lung/heart/kidney (P = 0.02/0.04/0.01) compared to control. R-107 treatment significantly decreased lung injury score/modified sheep SOFA score at 24-h (P = 0.01/0.04), significantly lowered arterial lactate (21-24 h, P < 0.05), shed syndecan-1 (3-6 h, P < 0.05), interleukin-6 (6-12 h, P < 0.05) levels in plasma, and significantly attenuated lung tissue 3-nitrotyrosine and vascular endothelial growth factor-A expressions (P = 0.03/0.002) compared to control. There was no adverse effect in R-107 treatment. In conclusion, modulation of O&NS by R-107 reduced hyperpermeability markers and improved multi-organ function.

The poorly conducted orchestra of steroid hormones, oxidative stress and inflammation in frailty needs a maestro: Regular physical exercise

This review outlines the various factors associated with unhealthy aging which includes becoming frail and dependent. With many people not engaging in recommended exercise, facilitators and barriers to engage with exercise must be investigated to promote exercise uptake and adherence over the lifespan for different demographics, including the old, less affluent, women, and those with different cultural-ethnic backgrounds. Governmental and locally funded public health messages and environmental facilitation (gyms, parks etc.) can play an important role. Studies have shown that exercise can act as a conductor to balance oxidative stress, immune and endocrine functions together to promote healthy aging and reduce the risk for age-related morbidities, such as cardiovascular disease and atherosclerosis, and promote cognition and mood over the lifespan. Like a classic symphony orchestra, consisting of four groups of related musical instruments - the woodwinds, brass, percussion, and strings - the aging process should also perform in harmony, with compassion, avoiding the aggrandizement of any of its individual parts during the presentation. This review discusses the wide variety of molecular, cellular and endocrine mechanisms (focusing on the steroid balance) underlying this process and their interrelationships.

Arginine vasopressin receptor 2 activation promotes microvascular permeability in sepsis

Methicillin-resistant Staphylococcus aureus (MRSA) sepsis is a severe condition associated with vascular leakage and poor prognosis. The hemodynamic management of sepsis targets hypotension, but there is no specific treatment available for vascular leakage. Arginine vasopressin (AVP) has been used in sepsis to promote vasoconstriction by activating AVP receptor 1 (V₁R). However, recent evidence suggests that increased fluid retention may be associated with the AVP receptor 2 (V₂R) activation worsening the outcome of sepsis. Hence, we hypothesized that the inhibition of V₂R activation ameliorates the severity of microvascular hyperpermeability during sepsis. The hypothesis was tested using a well-characterized and clinically relevant ovine model of MRSA pneumonia/sepsis and in vitro assays of human lung microvascular endothelial cells (HMVECs). in vivo experiments demonstrated that the treatment of septic sheep with tolvaptan (TLVP), an FDA-approved V₂R antagonist, significantly attenuated the sepsis-induced fluid retention and markedly reduced the lung water content. These pathological changes were not affected by the treatment with V₂R agonist, desmopressin (DDAVP). Additionally, the incubation of cultured HMVECs with DDAVP, and DDAVP along with MRSA significantly increased the paracellular permeability. Finally, both the DDAVP and MRSA-induced hyperpermeability was significantly attenuated by TLVP. Subsequent protein and gene expression assays determined that the V₂R-induced increase in permeability is mediated by phospholipase C beta (PLCβ) and the potent permeability factor angiopoietin-2. In conclusion, our results indicate that the activation of the AVP-V₂R axis is critical in the pathophysiology of severe microvascular hyperpermeability during Gram-positive sepsis. The use of the antagonist TLVP should be considered as adjuvant treatment for septic patients. The results from this clinically relevant animal study are highly translational to clinical practice.

Blood carboxyhemoglobin elimination curve, half-lifetime, and arterial-venous differences in acute phase of carbon monoxide poisoning in ovine smoke inhalation injury model

Smoke inhalation injury (SII) affects more than 50,000 people annually causing carbon monoxide (CO) poisoning. Although the increased blood level of carboxyhemoglobin (CO-Hb) is frequently used to confirm the diagnosis of SII, knowledge of its elimination in the acute phase is still limited. The aim of this study is to determine CO-Hb elimination rates and their differences in arterial (aCO-Hb) and mixed-venous (vCO-Hb) blood following severe SII in a clinically relevant ovine model. Forty-three chronically instrumented female sheep were subjected to SII (12 breaths, 4 sets) through tracheostomy tube under anesthesia and analgesia. After the SII, sheep were awakened and placed on a mechanical ventilator (FiO₂ = 1.0, tidal volume 12 mL/kg, and PEEP = 5cmH₂O) and monitored. Arterial and mixed-venous blood samples were withdrawn simultaneously for blood gas analysis at various time points to determine CO-HB half-lifetime and an elimination curve. The mean of highest aCO-Hb level during SII was 70.8 ± 13.9%. The aCO-Hb elimination curve showed an approximated exponential decay during the first 60 min. Per mixed linear regression model analysis, aCO-Hb significantly (p < 0.001) declined (4.3%/minute) with a decay constant lambda of 0.044. With this lambda, mean lifetime and half-lifetime of aCO-Hb were 22.7 and 15.7 min, respectively. The aCO-Hb was significantly lower compared to vCO-Hb at all-time points (0-180 min). To our knowledge, this is the first report describing CO-Hb elimination curve in the acute phase after severe SII in the clinically relevant ovine model. Our data shows that CO-Hb is decreasing in linear manner with supportive mechanical ventilation (0-60 min). The results may help to understand CO-Hb elimination curve in the acute phase and improvement of pre-hospital and initial clinical care in patients with CO poisoning.