Muscle wasting and early mobilization in acute respiratory distress syndrome

Impaired muscle stem cell function and abnormal myogenesis in acquired myopathies

Skeletal muscle possesses a high plasticity and a remarkable regenerative capacity that relies mainly on muscle stem cells (MuSCs). Molecular and cellular components of the MuSC niche, such as immune cells, play key roles to coordinate MuSC function and to orchestrate muscle regeneration. An abnormal infiltration of immune cells and/or imbalance of pro- and anti-inflammatory cytokines could lead to MuSC dysfunctions that could have long lasting effects on muscle function. Different genetic variants were shown to cause muscular dystrophies that intrinsically compromise MuSC function and/or disturb their microenvironment leading to impaired muscle regeneration that contributes to disease progression. Alternatively, many acquired myopathies caused by comorbidities (e.g., cardiopulmonary or kidney diseases), chronic inflammation/infection, or side effects of different drugs can also perturb MuSC function and their microenvironment. The goal of this review is to comprehensively summarize the current knowledge on acquired myopathies and their impact on MuSC function. We further describe potential therapeutic strategies to restore MuSC regenerative capacity.

Nonrespiratory sites of influenza-associated disease: mechanisms and experimental systems for continued study

The productive replication of human influenza viruses is almost exclusively restricted to cells in the respiratory tract. However, a key aspect of the host response to viral infection is the production of inflammatory cytokines and chemokines that are not similarly tissue restricted. As such, circulating inflammatory mediators, as well as the resulting activated immune cells, can induce damage throughout the body, particularly in individuals with underlying conditions. As a result, more holistic experimental approaches are required to fully understand the pathogenesis and scope of influenza virus-induced disease. This review summarizes what is known about some of the most well-appreciated nonrespiratory tract sites of influenza virus-induced disease, including neurological, cardiovascular, gastrointestinal, muscular and fetal developmental phenotypes. In the context of this discussion, we describe the in vivo experimental systems currently being used to study nonrespiratory symptoms. Finally, we highlight important future questions and potential models that can be used for a more complete understanding of influenza virus-induced disease.

Study protocol for a two-center test of a nurse-implemented chronotherapeutic restoring bundle in critically ill children: RESTORE Resilience (R2)

Often, pediatric intensive care environments are not conducive to healing the sick. Critically ill children experience disruptions in their circadian rhythms, which can contribute to delayed recovery and poor outcomes. We aim to test the hypothesis that children managed via RESTORE Resilience (R2), a nurse-implemented chronotherapeutic bundle, will experience restorative circadian rhythms compared to children receiving usual care. In this two-phased, prospective cohort study, two separate pediatric intensive care units in the United Sates will enroll a total of 20 baseline subjects followed by 40 intervention subjects, 6 months to less than 18 years of age, requiring invasive mechanical ventilation. During the intervention phase, we will implement the R2 bundle, which includes: (1) a focused effort to replicate the child's pre-hospitalization daily routine, (2) cycled day-night lighting and sound modulation, (3) minimal yet effective sedation (RESTORE), (4) nighttime fasting with bolus enteral daytime feedings, (5) early progressive mobility (PICU Up!), (6) continuity in nursing care, and (7) parent diaries. Our primary outcome is circadian activity ratio post-extubation. We hypothesize that children receiving R2 will experience restored circadian rhythms as evidenced by decreased nighttime activity while in the PICU. Our exploratory outcomes include salivary melatonin levels; electroencephalogram (EEG) slow-wave activity; R2 feasibility, adherence, and system barriers; levels of patient comfort; exposure to sedative medications; time to physiological stability; and parent perception of being well cared for. This paper describes the design, rationale, and implementation of R2.

CLINICALTRIALSGOV IDENTIFIER

NCT04695392.

A randomized, controlled, multicenter clinical study of the "improved sitting Wuqinxi" intervention for mechanically ventilated patients in the intensive care unit

INTRODUCTION

Mechanical ventilation is a powerful tool for the treatment of various critical emergencies. However, surviving critically ill patients often have poor psychological and physiological outcomes. Prevention of various complications and adverse outcomes of mechanical ventilation is a priority and a challenge in the intensive care unit (ICU). Early intervention is the key to reducing complications and improving outcomes of mechanical ventilation in the ICU. As an auxiliary rehabilitation treatment, the improved sitting Wuqinxi intervention has recognized unique advantages. It has achieved beneficial therapeutic effects during early intervention in clinical practice. It can reduce the incidence of delirium, shorten the duration of mechanical ventilation, and prevent complications and secondary damages related to mechanical ventilation in the ICU. Therefore, the purpose of this study will be to explore the effect of improved sitting Wuqinxi on the clinical outcomes of mechanically ventilated ICU patients.

METHODS

This prospective, multicenter, randomized, single-blinded, parallel controlled clinical study will involve 160 patients who met the inclusion criteria. The patients will be randomly divided into the experimental and control groups. Both groups will be given standardized comprehensive western medicine treatment (including mechanical ventilation) and routine care in the ICU. Management of the experimental group will also include "improved sitting Wuqinxi," with the treatment objective to observe the effect of the improved sitting Wuqinxi intervention on the clinical outcomes in mechanically ventilated ICU patients. The outcome measures will include the incidence of complications, duration of mechanical ventilation, length of ICU stay, and cost of hospitalization. In addition, the effect of the improved sitting Wuqinxi intervention on the safety indexes of mechanically ventilated ICU patients will be assessed and the clinical effects of the improved sitting Wuqinxi intervention will be comprehensively evaluated.

DISCUSSION

The purpose of this study will be to evaluate the effect of the improved sitting Wuqinxi intervention on the incidence of complications, duration of mechanical ventilation, length of ICU stay, cost of hospitalization, and safety indicators. If successful, it will provide a reliable, simple, and feasible auxiliary rehabilitation treatment scheme for mechanically ventilated ICU patients.

Physical rehabilitation in Intensive Care Unit in acute respiratory distress syndrome patients with COVID-19

BACKGROUND

The risk of muscle weakness is high in the survivors of acute respiratory distress syndrome with COVID-19 following discharge from intensive care unit.

AIM

To evaluate the effects of early rehabilitation program in intensive care unit in patients with acute respiratory distress syndrome secondary to COVID-19.

DESIGN

The design of the study is observational.

SETTING

The setting of the study is inpatient.

POPULATION

Thirty-five patients with acute respiratory distress syndrome secondary to COVID-19 were enrolled.

METHODS

This study was performed in an intensive care unit of a university hospital. Early rehabilitation program consisting of passive or active range of motion exercises and neuromuscular electrical stimulation in addition to standard intensive care (N.=18) compared to standard intensive care (N.=17). Primary outcome was hand grip strength following discharge.

RESULTS

Rehab group had higher prevalence of chronic pulmonary diseases and neurologic diseases. There was no difference in hand grip or manual muscle strength following discharge between rehab and non-rehab groups. No adverse event was noted.

CONCLUSIONS

The results did not support the beneficial effects of early rehabilitation in intensive care unit on improving muscle strength. More patients with pulmonary and neurologic diseases in rehab group might impede the impact of rehabilitation on outcomes. On the other hand, these comorbidities underline the role and need of rehabilitation. It is safe both for the patients and the health care workers when necessary precautions are taken.

CLINICAL REHABILITATION IMPACT

This study guide how to rehabilitate patients with acute respiratory distress syndrome with COVID-19 during intensive care unit in a safe way.

Impaired phagocytic function in CX3CR1+ tissue-resident skeletal muscle macrophages prevents muscle recovery after influenza A virus-induced pneumonia in old mice

Skeletal muscle dysfunction in survivors of pneumonia disproportionately affects older individuals in whom it causes substantial morbidity. We found that skeletal muscle recovery was impaired in old compared with young mice after influenza A virus-induced pneumonia. In young mice, recovery of muscle loss was associated with expansion of tissue-resident skeletal muscle macrophages and downregulation of MHC II expression, followed by a proliferation of muscle satellite cells. These findings were absent in old mice and in mice deficient in Cx3cr1. Transcriptomic profiling of tissue-resident skeletal muscle macrophages from old compared with young mice showed downregulation of pathways associated with phagocytosis and proteostasis, and persistent upregulation of inflammatory pathways. Consistently, skeletal muscle macrophages from old mice failed to downregulate MHCII expression during recovery from influenza A virus-induced pneumonia and showed impaired phagocytic function in vitro. Like old animals, mice deficient in the phagocytic receptor Mertk showed no macrophage expansion, MHCII downregulation, or satellite cell proliferation and failed to recover skeletal muscle function after influenza A pneumonia. Our data suggest that a loss of phagocytic function in a CX3CR1+ tissue-resident skeletal muscle macrophage population in old mice precludes satellite cell proliferation and recovery of skeletal muscle function after influenza A pneumonia.

Sequelae of Acute Respiratory Distress Syndrome: Interest of Rehabilitation

Case Presentation

This clinical case presents the history of a woman hospitalized for acute respiratory distress syndrome (ARDS). A 62-year-old woman, with regular physical activity and no history of respiratory disease or smoking, was hospitalized for moderate ARDS with bilateral pneumonitis. Fourteen days later, she was discharged from the intensive care unit and received respiratory physical therapy. One month later, she experienced exertional dyspnea. A regression of alveolar condensation with persistent sequelae at the pulmonary bases was noted. Three months later, the patient continued daily physical activity with satisfactory tolerance. A reduction in alveolar-capillary transfer, inappropriate hyperventilation upon exercise, and impairment of gas exchanges at maximal effort, suggestive of pulmonary shunt, were demonstrated. At the 6-month evaluation, the patient displayed exertional dyspnea with residual bilateral basal consolidations. Six months later, the dyspnea had ceased. The persistence of bilateral basal interstitial syndrome associated with bronchial dilatation and pleural-based consolidations was noted, as well as a stable impaired alveolar-capillary diffusing capacity.

Discussion

Upon discharge from intensive care, pulmonary follow-up should be proposed to ARDS survivors. Moreover, pulmonary function testing at rest and exercise is advised as soon as possible to evaluate the respiratory sequelae. This will help to limit the severity of complications through adapted exercise rehabilitation and then regular physical activity.

Influenza A Virus Infection Induces Muscle Wasting via IL-6 Regulation of the E3 Ubiquitin Ligase Atrogin-1

Muscle dysfunction is common in patients with adult respiratory distress syndrome and is associated with morbidity that can persist for years after discharge. In a mouse model of severe influenza A pneumonia, we found the proinflammatory cytokine IL-6 was necessary for the development of muscle dysfunction. Treatment with a Food and Drug Administration-approved Ab antagonist to the IL-6R (tocilizumab) attenuated the severity of influenza A-induced muscle dysfunction. In cultured myotubes, IL-6 promoted muscle degradation via JAK/STAT, FOXO3a, and atrogin-1 upregulation. Consistent with these findings, atrogin-1+/- and atrogin-1-/- mice had attenuated muscle dysfunction following influenza infection. Our data suggest that inflammatory endocrine signals originating from the injured lung activate signaling pathways in the muscle that induce dysfunction. Inhibiting these pathways may limit morbidity in patients with influenza A pneumonia and adult respiratory distress syndrome.

Aerobic Exercise Protects from Pseudomonas aeruginosa-Induced Pneumonia in Elderly Mice

BACKGROUND

Pseudomonas aeruginosa (PS) infection results in severe morbidity and mortality, especially in immune-deficient populations. Aerobic exercise (AE) modulates the immune system, but its effects on the outcomes of pulmonary PS infection in elderly mice are unknown.

METHODS

BALB/c mice (24 weeks old) were randomized to sedentary, exercise (EX), PS, and PS + EX groups for the acute experimental setting, and PS and PS + EX groups for the chronic setting. Low-intensity AE was performed for 5 weeks, 60 min/day; 24 h after the final AE session, mice were inoculated with 5 × 104 colony-forming units (CFU) of PS, and 24 h and 14 days after PS inoculation, mice were studied.

RESULTS

AE inhibited PS colonization (p < 0.001) and lung inflammation (total cells, neutrophils, lymphocytes [p < 0.01] in bronchoalveolar lavage [BAL]), with significant differences in BAL levels of IL-1β (p < 0.001), IL-6 (p < 0.01), CXCL1 (p < 0.001), and TNF-α (p < 0.001), as well as parenchymal neutrophils (p < 0.001). AE increased BAL levels of IL-10 and parenchymal (p < 0.001) and epithelial (p < 0.001) IL-10 expression, while epithelial (p < 0.001) and parenchymal (p < 0.001) NF-κB expression was decreased. AE diminished pulmonary lipid peroxidation (p < 0.001) and increased glutathione peroxidase (p < 0.01). Pre-incubation of BEAS-2B with IL-10 inhibited PS-induced epithelial cell expression of TNF-α (p < 0.05), CD40 (p < 0.01), and dichlorodihydrofluorescein diacetate (p < 0.05).

CONCLUSIONS

AE inhibits PS-induced lung inflammation and bacterial colonization in elderly mice, involving IL-10/NF-κB, and redox signaling.

An attenuated rate of leg muscle protein depletion and leg free amino acid efflux over time is seen in ICU long-stayers

BACKGROUND

There is extensive documentation on skeletal muscle protein depletion during the initial phase of critical illness. However, for intensive care unit (ICU) long-stayers, objective data are very limited. In this study, we examined skeletal muscle protein and amino acid turnover in patients with a prolonged ICU stay.

METHODS

Patients (n = 20) were studied serially every 8-12 days between days 10 and 40 of their ICU stay as long as patients stayed in the ICU. Leg muscle protein turnover was assessed by measurements of phenylalanine kinetics, for which we employed a stable isotope-labeled phenylalanine together with two-pool and three-pool models for calculations, and results were expressed per 100 ml of leg volume. In addition, leg muscle amino acid flux was studied.

RESULTS

The negative leg muscle protein net balance seen on days 10-20 of the ICU stay disappeared by days 30-40 (p = 0.012). This was attributable mainly to an increase in the de novo protein synthesis rate (p = 0.007). It was accompanied by an attenuated efflux of free amino acids from the leg. Leg muscle protein breakdown rates stayed unaltered (p = 0.48), as did the efflux of 3-methylhistidine. The arterial plasma concentrations of free amino acids did not change over the course of the study.

CONCLUSIONS

In critically ill patients with sustained organ failure and in need of a prolonged ICU stay, the initial high rate of skeletal muscle protein depletion was attenuated over time. The distinction between the acute phase and a more prolonged and more stable phase concerning skeletal muscle protein turnover must be considered in study protocols as well as in clinical practice.

TRIAL REGISTRATION

Australian New Zealand Trial Registry, ACTRN12616001012460 . Retrospectively registered on 1 August 2016.

The response of muscle progenitor cells to cutaneous thermal injury

BACKGROUND

Severe burn results in a systemic response that leads to significant muscle wasting. It is believed that this rapid loss in muscle mass occurs due to increased protein degradation combined with reduced protein synthesis. Alterations in the microenvironment of muscle progenitor cells may partially account for this pathology. The aim of this study was to ascertain the response of muscle progenitor cells following thermal injury in mice and to enlighten the cellular cascades that contribute to the muscle wasting.

METHODS

C57BL/6 mice received a 20% total body surface area (TBSA) thermal injury. Gastrocnemius muscle was harvested at days 2, 7, and 14 following injury for protein and histological analysis.

RESULTS

We observed a decrease in myofiber cross-sectional area at 2 days post-burn. This muscle atrophy was compensated for by an increase in myofiber cross-sectional area at 7 and 14 days post-burn. Myeloperoxidase (MPO)-positive cells (neutrophils) increased significantly at 2 days. Moreover, through Western blot analysis of two key mediators of the proteolytic pathway, we show there is an increase in Murf1 and NF-κB 2 days post-burn. MPO-positive cells were also positive for NF-κB, suggesting that neutrophils attain NF-κB activity in the muscle. Unlike inflammatory and proteolytic pathways, the number of Pax7-positive muscle progenitor cells decreased significantly 2 days post-burn. This was followed by a recovery in the number of Pax7-positive cells at 7 and 14 days, suggesting proliferation of muscle progenitors that accompanied regrowth.

CONCLUSION

Our data show a biphasic response in the muscles of mice exposed to burn injury, with phenotypic characteristics of muscle atrophy at 2 days while compensation was observed later with a change in Pax7-positive muscle progenitor cells. Targeting muscle progenitors may be of therapeutic benefit in muscle wasting observed after burn injury.

Current Concepts Burn Rehabilitation, Part I: Care During Hospitalization

This article summarizes current interventions for several of the most common challenges faced by patients during their rehabilitation from burn injury. These include preservation of range of motion through scar contracture management, and achieving maximal independence through exercise, and training in activities of daily living.

Mechanisms of Chronic Muscle Wasting and Dysfunction after an Intensive Care Unit Stay. A Pilot Study

RATIONALE

Critical illness survivors often experience permanent functional disability due to intensive care unit (ICU)-acquired weakness. The mechanisms responsible for long-term weakness persistence versus resolution are unknown.

OBJECTIVES

To delineate cellular mechanisms underlying long-term weakness persistence in ICU survivors.

METHODS

We conducted a nested, prospective study of critically ill patients mechanically ventilated for 7 days or longer. The patients were recruited from the RECOVER program and serially assessed over 6 months after ICU discharge. Twenty-seven of 82 patients consented to participate; 15 and 11 patients were assessed at 7 days and 6 months after ICU discharge, respectively.

MEASUREMENTS AND MAIN RESULTS

We assessed motor functional capacity, quadriceps size, strength, and voluntary contractile capacity and performed electromyography, nerve conduction studies, and vastus lateralis biopsies for histologic, cellular, and molecular analyses. Strength and quadriceps cross-sectional areas were decreased 7 days after ICU discharge. Weakness persisted to 6 months and correlated with decreased function. Quadriceps atrophy resolved in 27% patients at 6 months. Muscle mass reconstitution did not correlate with resolution of weakness, owing to persistent impaired voluntary contractile capacity. Compared with Day 7, increased ubiquitin-proteasome system-mediated muscle proteolysis, inflammation, and decreased mitochondrial content all normalized at 6 months. Autophagy markers were normal at 6 months. Patients with sustained atrophy had decreased muscle progenitor (satellite) cell content.

CONCLUSIONS

Long-term weakness in ICU survivors results from heterogeneous muscle pathophysiology with variable combinations of muscle atrophy and impaired contractile capacity. These findings are not explained by ongoing muscle proteolysis, inflammation, or diminished mitochondrial content. Sustained muscle atrophy is associated with decreased satellite cell content and compromised muscle regrowth, suggesting impaired regenerative capacity.

Transcriptomic analysis reveals abnormal muscle repair and remodeling in survivors of critical illness with sustained weakness

ICU acquired weakness (ICUAW) is a common complication of critical illness characterized by structural and functional impairment of skeletal muscle. The resulting physical impairment may persist for years after ICU discharge, with few patients regaining functional independence. Elucidating molecular mechanisms underscoring sustained ICUAW is crucial to understanding outcomes linked to different morbidity trajectories as well as for the development of novel therapies. Quadriceps muscle biopsies and functional measures of muscle strength and mass were obtained at 7 days and 6 months post-ICU discharge from a cohort of ICUAW patients. Unsupervised co-expression network analysis of transcriptomic profiles identified discrete modules of co-expressed genes associated with the degree of muscle weakness and atrophy in early and sustained ICUAW. Modules were enriched for genes involved in skeletal muscle regeneration and extracellular matrix deposition. Collagen deposition in persistent ICUAW was confirmed by histochemical stain. Modules were further validated in an independent cohort of critically ill patients with sepsis-induced multi-organ failure and a porcine model of ICUAW, demonstrating disease-associated conservation across species and peripheral muscle type. Our findings provide a pathomolecular basis for sustained ICUAW, implicating aberrant expression of distinct skeletal muscle structural and regenerative genes in early and persistent ICUAW.

[Variation of muscle mass and weight in critical patient]

OBJECTIVES

Quantify the muscle mass and body weight variation in critically ill patients and to identify associated factors.

METHOD

A descriptive follow-up study. Data for demographic variables, body weight, fluid balance, daily kilocalories, the amount of sedation and muscle relaxants received and motor physiotherapy applied were collected. Three consecutive measurements were performed in the brachial biceps and quadriceps rectus by using ultrasound, upon admission and every 5 days until discharge.

RESULTS

68 patients were included. Average age was of 73.5 [57-78,5] years. The median length of stay was 9.5 [5.5 -15] days. The median 16 (SD=5.7) daily kilocalories per kg/weight, 91.2% received sedation, 44.1% received muscle relaxants and 20% received physiotherapy. The patients presented a muscle wasting of 4.9 (SD=3.9)mm, p <.001 in the brachial biceps and 5.6 (SD=4.8)mm, p <.001 in the quadriceps rectus. Regression analysis selected the length of stay and the muscle relaxants are the most influential variables in the brachial biceps muscle wasting (R2=0.4), and length of stay as the most influential in the quadriceps rectus muscle wasting (R2=0.3). Patient's mean body weight on admission was of 81.1 (SD=15)kg and 81.2 (SD=14.2)kg on discharge, p=.95.

CONCLUSIONS

The critically ill patient presents a significant muscle waste related with the length of stay and the treatment received with muscle relaxants. Patients are being discharged with a similar body weight to which they were admitted but with a significant reduction of muscle mass.