Progression and variability of physiologic deterioration in an ovine model of lung infection sepsis

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.

Modeling sepsis, with a special focus on large animal models of porcine peritonitis and bacteremia

Infectious diseases, which often result in deadly sepsis or septic shock, represent a major global health problem. For understanding the pathophysiology of sepsis and developing new treatment strategies, reliable and clinically relevant animal models of the disease are necessary. In this review, two large animal (porcine) models of sepsis induced by either peritonitis or bacteremia are introduced and their strong and weak points are discussed in the context of clinical relevance and other animal models of sepsis, with a special focus on cardiovascular and immune systems, experimental design, and monitoring. Especially for testing new therapeutic strategies, the large animal (porcine) models represent a more clinically relevant alternative to small animal models, and the findings obtained in small animal (transgenic) models should be verified in these clinically relevant large animal models before translation to the clinical level.

A framework to characterize the performance of early warning index alarm systems for patient monitoring

In [Scully, C.G., and Daluwatte, C., Evaluating performance of early warning indices to predict physiological instabilities. J Biomed Inform. 75 (2017) 14–21], a framework was presented to characterize the performance of warning indices to provide information on the 1) probability a critical health event will occur when a warning is given (analogous to positive predictive value) and 2) proportion of warned events to all events (analogous to sensitivity). This framework also provides information about the timeliness of the warnings with respect to event occurrence and the warning burden of the system.

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In the current work, we provide information on how this framework can be used when cases without events are present in a dataset to examine the proportion of warned non-events to all non-events (analogous to false positive rate).

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Information on steps to apply the method, software, data and results for the case study are also provided to enable implementation of the framework.

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Application and extension of the framework is demonstrated and discussed by adding non-event records to our previous case study comparing two warning strategies to predict physiologic instabilities.

Preclinical septic shock research: why we need an animal ICU

Animal experiments are widely used in preclinical medical research with the goal of disease modeling and exploration of novel therapeutic approaches. In the context of sepsis and septic shock, the translation into clinical practice has been disappointing. Classical animal models of septic shock usually involve one-sex-one-age animal models, mostly in mice or rats, contrasting with the heterogeneous population of septic shock patients. Many other factors limit the reliability of preclinical models and may contribute to preclinical research failure in critical care, including the host specificity of several pathogens, the fact that laboratory animals are raised in pathogen-free facilities and that organ support techniques are either absent or minimal. Advanced animal models have been developed with the aim of improving the clinical translatability of experimental findings. So-called animal ICUs refer to the preclinical investigation of adult or even aged animals of either sex, using—in case of rats and mice—miniaturized equipment allowing for reproducing an ICU environment at a small animal scale and integrating chronic comorbidities to more closely reflect the clinical conditions studied. Strength and limitations of preclinical animal models designed to decipher the mechanisms involved in septic cardiomyopathy are discussed. This article reviews the current status and the challenges of setting up an animal ICU.