Muscle force and fatigue in patients with sepsis and multiorgan failure

Early detection and assessment of intensive care unit-acquired weakness: a comprehensive review

Intensive care unit-acquired weakness (ICU-AW) is a serious complication in critically ill patients. Therefore, timely and accurate diagnosis and monitoring of ICU-AW are crucial for effectively preventing its associated morbidity and mortality. This article provides a comprehensive review of ICU-AW, focusing on the different methods used for its diagnosis and monitoring. Additionally, it highlights the role of bedside ultrasound in muscle assessment and early detection of ICU-AW. Furthermore, the article explores potential strategies for preventing ICU-AW. Healthcare providers who manage critically ill patients utilize diagnostic approaches such as physical exams, imaging, and assessment tools to identify ICU-AW. However, each method has its own limitations. The diagnosis of ICU-AW needs improvement due to the lack of a consensus on the appropriate approach for its detection. Nevertheless, bedside ultrasound has proven to be the most reliable and cost-effective tool for muscle assessment in the ICU. Combining the Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) II score assessment, and ultrasound can be a convenient approach for the early detection of ICU-AW. This approach can facilitate timely intervention and prevent catastrophic consequences. However, further studies are needed to strengthen the evidence.

Ultrasonographic findings in long COVID: A cross-sectional study of 312 patients

Background

Fatigue and muscle weakness are common complaints in COVID-19 survivors. However, little is still known about the skeletal muscle qualitative and quantitative characteristics after hospitalization due to moderate and severe COVID-19.

Objectives

To assess rectus femoris and vastus intermedius muscle thickness (MT) and rectus femoris echo intensity (EI) and to establish its association with demographic, clinical, functional, and inflammatory parameters in long COVID patients after hospital discharge.

Methods

Cross-sectional study with 312 COVID-19 patients (53.53% male; age: 54.59 ± 13.50 years), with a laboratory-confirmed diagnosis of COVID-19. Patients were assessed 3-11 months after hospital discharge. We evaluated MT of the right rectus femoris and vastus intermedius and EI of the right rectus femoris using a portable ultrasound system, 6-13 MHz, broadband linear transducer. We corrected EI using the subcutaneous fat thickness. Ultrasonographic parameters were tested in association with demographic (sex and age); functional (Handgrip strength measurement, Timed Up and Go, 1 min Sit-to-Stand test, EuroQoL-5 Dimensions-5 Levels, World Health Organization Disability Assessment Schedule (WHODAS 2.0), Post-COVID-19 Functional Status, Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT), Medical Research Council (MRC) sum score, Borg Dyspnea Scale, MRC Dyspnea score, Visual Analogue Scale (VAS), Epworth Sleepiness Scale, Insomnia Severity Index, Functional Independence Measurement (FIM), and Functional Oral Intake Scale); clinical (length of hospital stay, intubation, and presence of comorbidities such as systemic hypertension, diabetes, obesity, chronic obstructive pulmonary disease, asthma), and inflammatory data assessed by the C-reactive protein and D-dimer serum concentrations.

Results

Rectus femoris MT was associated with age, handgrip strength, Epworth Sleepiness Scale, and subcutaneous fat thickness (r² = 27.51%; p < 0.0001). Vastus intermedius MT was associated with age, pain intensity, handgrip strength, Epworth Sleepiness scale, FIM, and time since hospital discharge (r² = 21.12%; p < 0.0001). Rectus femoris EI was significantly associated with the male sex, TUG, Epworth Sleepiness Scale, and C-Reactive Protein levels (r² = 44.39%; p < 0.0001). Mean MT of rectus femoris and vastus intermedius are significantly different (p < 0.001).

Conclusion

After hospital discharge, long COVID patients present qualitative and quantitative skeletal muscle characteristics associated with a combination of demographic, clinical, and functional parameters.

The rate and assessment of muscle wasting during critical illness: a systematic review and meta-analysis

BACKGROUND

Patients with critical illness can lose more than 15% of muscle mass in one week, and this can have long-term detrimental effects. However, there is currently no synthesis of the data of intensive care unit (ICU) muscle wasting studies, so the true mean rate of muscle loss across all studies is unknown. The aim of this project was therefore to systematically synthetise data on the rate of muscle loss and to identify the methods used to measure muscle size and to synthetise data on the prevalence of ICU-acquired weakness in critically ill patients.

METHODS

We conducted a systematic literature search of MEDLINE, PubMed, AMED, BNI, CINAHL, and EMCARE until January 2022 (International Prospective Register of Systematic Reviews [PROSPERO] registration: CRD420222989540. We included studies with at least 20 adult critically ill patients where the investigators measured a muscle mass-related variable at two time points during the ICU stay. We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and assessed the study quality using the Newcastle-Ottawa Scale.

RESULTS

Fifty-two studies that included 3251 patients fulfilled the selection criteria. These studies investigated the rate of muscle wasting in 1773 (55%) patients and assessed ICU-acquired muscle weakness in 1478 (45%) patients. The methods used to assess muscle mass were ultrasound in 85% (n = 28/33) of the studies and computed tomography in the rest 15% (n = 5/33). During the first week of critical illness, patients lost every day -1.75% (95% CI -2.05, -1.45) of their rectus femoris thickness or -2.10% (95% CI -3.17, -1.02) of rectus femoris cross-sectional area. The overall prevalence of ICU-acquired weakness was 48% (95% CI 39%, 56%).

CONCLUSION

On average, critically ill patients lose nearly 2% of skeletal muscle per day during the first week of ICU admission.

Sepsis-Induced Myopathy and Gut Microbiome Dysbiosis: Mechanistic Links and Therapeutic Targets

ABSTRACT

Sepsis is currently defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. The skeletal muscle system is among the host organ systems compromised by sepsis. The resulting neuromuscular dysfunction and impaired regenerative capacity defines sepsis-induced myopathy and manifests as atrophy, loss of strength, and hindered regeneration after injury. These outcomes delay recovery from critical illness and confer increased vulnerability to morbidity and mortality. The mechanisms underlying sepsis-induced myopathy, including the potential contribution of peripheral organs, remain largely unexplored. The gut microbiome is an immunological and homeostatic entity that interacts with and controls end-organ function, including the skeletal muscle system. Sepsis induces alterations in the gut microbiota composition, which is globally termed a state of "dysbiosis" for the host compared to baseline microbiota composition. In this review, we critically evaluate existing evidence and potential mechanisms linking sepsis-induced myopathy with gut microbiota dysbiosis.

High-dose intravenous immunoglobulins as a therapeutic option in critical illness polyneuropathy accompanying SARS-CoV-2 infection: A case-based review of the literature (Review)

The still ongoing COVID-19 pandemic has exposed the medical community to a number of major challenges. A significant number of patients require admission to intensive care unit (ICU) services due to severe respiratory, thrombotic and septic complications and require long-term hospitalization. Neuromuscular weakness is a common complication in critically ill patients who are treated in ICUs and are mechanically ventilated. This complication is frequently caused by critical illness myopathy (CIM) or critical illness polyneuropathy (CIP) and leads to difficulty in weaning from the ventilator. It is thought to represent an important neurologic manifestation of the systemic inflammatory response syndrome (SIRS). COVID-19 infection is known to trigger strong immune dysregulation, with an intense cytokine storm, as a result, the frequency of CIP is expected to be higher in this setting. The mainstay in the diagnosis of this entity beside the high level of clinical awareness is the electrophysiological examination that provides evidence of axonal motor and sensory polyneuropathy. The present article presents the case of a 54-year-old woman with severe COVID 19 infection who developed neuromuscular weakness, which turned out to be secondary to CIP and was treated successfully with a high dose of human intravenous immunoglobulins. Related to this case, we reviewed the relevant literature data regarding the epidemiology, pathophysiology and clinical features of this important complication and discussed also the treatment options and prognosis.

Bedside voluntary and evoked forces evaluation in intensive care unit patients: a narrative review

Around one third of intensive care unit (ICU) patients will develop severe neuromuscular alterations, known as intensive care unit-acquired weakness (ICUAW), during their stay. The diagnosis of ICUAW is difficult and often delayed as a result of sedation or delirium. Indeed, the clinical evaluation of both Medical Research Council score and maximal voluntary force (e.g., using handgrip and/or handheld dynamometers), two independent predictors of mortality, can be performed only in awake and cooperative patients. Transcutaneous electrical/magnetic stimulation applied over motor nerves combined with the development of dedicated ergometer have recently been introduced in ICU patients in order to propose an early and non-invasive measurement of evoked force. The aim of this narrative review is to summarize the different tools allowing bedside force evaluation in ICU patients and the related experimental protocols. We suggest that non-invasive electrical and/or magnetic evoked force measurements could be a relevant strategy to characterize muscle weakness in the early phase of ICU and diagnose ICUAW.

Inflammatory, synaptic, motor, and behavioral alterations induced by gestational sepsis on the offspring at different stages of life

BACKGROUND

The term sepsis is used to designate a systemic condition of infection and inflammation associated with hemodynamic changes that result in organic dysfunction. Gestational sepsis can impair the development of the central nervous system and may promote permanent behavior alterations in the offspring. The aim of our work was to evaluate the effects of maternal sepsis on inflammatory cytokine levels and synaptic proteins in the hippocampus, neocortex, frontal cortex, and cerebellum of neonatal, young, and adult mice. Additionally, we analyzed the motor development, behavioral features, and cognitive impairments in neonatal, young and adult offspring.

METHODS

Pregnant mice at the 14th embryonic day (E14) were intratracheally instilled with saline 0.9% solution (control group) or Klebsiella spp. (3 × 108 CFU) (sepsis group) and started on meropenem after 5 h. The offspring was sacrificed at postnatal day (P) 2, P8, P30, and P60 and samples of liver, lung, and brain were collected for TNF-α, IL-1β, and IL-6 measurements by ELISA. Synaptophysin, PSD95, and β-tubulin levels were analyzed by Western blot. Motor tests were performed at all analyzed ages and behavioral assessments were performed in offspring at P30 and P60.

RESULTS

Gestational sepsis induces a systemic pro-inflammatory response in neonates at P2 and P8 characterized by an increase in cytokine levels. Maternal sepsis induced systemic downregulation of pro-inflammatory cytokines, while in the hippocampus, neocortex, frontal cortex, and cerebellum an inflammatory response was detected. These changes in the brain immunity were accompanied by a reduction of synaptophysin and PSD95 levels in the hippocampus, neocortex, frontal cortex, and cerebellum, in all ages. Behavioral tests demonstrated motor impairment in neonates, and depressive-like behavior, fear-conditioned memory, and learning impairments in animals at P30 and P60, while spatial memory abilities were affected only at P60, indicating that gestational sepsis not only induces an inflammatory response in neonatal mouse brains, but also affects neurodevelopment, and leads to a plethora of behavioral alterations and cognitive impairments in the offspring.

CONCLUSION

These data suggest that maternal sepsis may be causatively related to the development of depression, learning, and memory impairments in the litter.

Relationship between intensive care unit-acquired weakness, fatigability and fatigue: What role for the central nervous system?

PURPOSE

To provide a comprehensive review of studies that have investigated fatigue in intensive care unit (ICU) survivors and questions the potential link between intensive care unit-acquired weakness (ICUAW), fatigability and fatigue. We also question whether the central nervous system (CNS) may be the link between these entities.

MATERIAL AND METHODS

A narrative review of the literature that investigated fatigue in ICU survivors and review of clinical trials enabling understanding of CNS alterations in response to ICU stays.

RESULTS

Fatigue is a pervasive and debilitating symptom in ICU survivors that can interfere with rehabilitation. Due to the complex pathophysiology of fatigue, more work is required to understand the roles of ICUAW and/or fatigability in fatigue to provide a more holistic understanding of this symptom. While muscle alterations have been well documented in ICU survivors, we believe that CNS alterations developing early during the ICU stay may play a role in fatigue.

CONCLUSIONS

Fatigue should be considered and treated in ICU survivors. The causes of fatigue are likely to be specific to the individual. Understanding the role that ICUAW and fatigability may have in fatigue would allow to tailor individual treatment to prevent this persistent symptom and improve quality of life.

Evaluation on the effect of acupuncture on patients with sepsis-induced myopathy (ACU-SIM pilot study): A single center, propensity-score stratified, assessor-blinded, prospective pragmatic controlled trial

BACKGROUND

Sepsis-induced myopathy (SIM) is a disease that causes motor dysfunction in patients with sepsis. There is currently no targeted treatment for this disease. Acupuncture has shown considerable efficacy in the treatment of sepsis and muscle weakness. Therefore, our research aims to explore the effects of acupuncture on the improvement of muscle structure and function in SIM patients and on activities of daily living.

METHODS

The ACU-SIM pilot study is a single-center, propensity-score stratified, assessor-blinded, prospective pragmatic controlled trial (pCT) with a 1-year follow-up period. This study will be deployed in a multi-professional critical care department at a tertiary teaching hospital in Guangzhou, China. Ninety-eight intensive care unit subjects will be recruited and assigned to either the control group or the acupuncture group. Both groups will receive basic treatment for sepsis, and the acupuncture group will additionally receive acupuncture treatment. The primary outcomes will be the rectus femoris cross-sectional area, the Medical Research Council sum-score and time-to-event (defined as all-cause mortality or unplanned readmission to the intensive care unit due to invasive ventilation). The activities of daily living will be accessed by the motor item of the Functional Independence Measure. Recruitment will last for 2 years, and each patient will have a 1-year follow-up after the intervention.

DISCUSSION

There is currently no research on the therapeutic effects of acupuncture on SIM. The results of this study may contribute to new knowledge regarding early muscle atrophy and the treatment effect of acupuncture in SIM patients, and the results may also direct new approaches and interventions in these patients. This trial will serve as a pilot study for an upcoming multicenter real-world study.

TRIAL REGISTRATION

Chinese Clinical Trials Registry: ChiCTR-1900026308, registered on September 29th, 2019.

Expression of MuRF1 or MuRF2 is essential for the induction of skeletal muscle atrophy and dysfunction in a murine pulmonary hypertension model

BACKGROUND

Pulmonary hypertension leads to right ventricular heart failure and ultimately to cardiac cachexia. Cardiac cachexia induces skeletal muscles atrophy and contractile dysfunction. MAFbx and MuRF1 are two key proteins that have been implicated in chronic muscle atrophy of several wasting states.

METHODS

Monocrotaline (MCT) was injected over eight weeks into mice to establish pulmonary hypertension as a murine model for cardiac cachexia. The effects on skeletal muscle atrophy, myofiber force, and selected muscle proteins were evaluated in wild-type (WT), MuRF1, and MuRF2-KO mice by determining muscle weights, in vitro muscle force and enzyme activities in soleus and tibialis anterior (TA) muscle.

RESULTS

In WT, MCT treatment induced wasting of soleus and TA mass, loss of myofiber force, and depletion of citrate synthase (CS), creatine kinase (CK), and malate dehydrogenase (MDH) (all key metabolic enzymes). This suggests that the murine MCT model is useful to mimic peripheral myopathies as found in human cardiac cachexia. In MuRF1 and MuRF2-KO mice, soleus and TA muscles were protected from atrophy, contractile dysfunction, while metabolic enzymes were not lowered in MuRF1 or MuRF2-KO mice. Furthermore, MuRF2 expression was lower in MuRF1KO mice when compared to C57BL/6 mice.

CONCLUSIONS

In addition to MuRF1, inactivation of MuRF2 also provides a potent protection from peripheral myopathy in cardiac cachexia. The protection of metabolic enzymes in both MuRF1KO and MuRF2KO mice as well as the dependence of MuRF2 expression on MuRF1 suggests intimate relationships between MuRF1 and MuRF2 during muscle atrophy signaling.

Chronic muscle weakness and mitochondrial dysfunction in the absence of sustained atrophy in a preclinical sepsis model

Chronic critical illness is a global clinical issue affecting millions of sepsis survivors annually. Survivors report chronic skeletal muscle weakness and development of new functional limitations that persist for years. To delineate mechanisms of sepsis-induced chronic weakness, we first surpassed a critical barrier by establishing a murine model of sepsis with ICU-like interventions that allows for the study of survivors. We show that sepsis survivors have profound weakness for at least 1 month, even after recovery of muscle mass. Abnormal mitochondrial ultrastructure, impaired respiration and electron transport chain activities, and persistent protein oxidative damage were evident in the muscle of survivors. Our data suggest that sustained mitochondrial dysfunction, rather than atrophy alone, underlies chronic sepsis-induced muscle weakness. This study emphasizes that conventional efforts that aim to recover muscle quantity will likely remain ineffective for regaining strength and improving quality of life after sepsis until deficiencies in muscle quality are addressed.

Sepsis-Induced Channelopathy in Skeletal Muscles is Associated with Expression of Non-Selective Channels

Skeletal muscles (∼50% of the body weight) are affected during acute and late sepsis and represent one sepsis associate organ dysfunction. Cell membrane changes have been proposed to result from a channelopathy of yet unknown cause associated with mitochondrial dysfunction and muscle atrophy. We hypothesize that the channelopathy might be explained at least in part by the expression of non-selective channels. Here, this possibility was studied in a characterized mice model of late sepsis with evident skeletal muscle atrophy induced by cecal ligation and puncture (CLP). At day seven after CLP, skeletal myofibers were found to present de novo expression (immunofluorescence) of connexins 39, 43, and 45 and P2X7 receptor whereas pannexin1 did not show significant changes. These changes were associated with increased sarcolemma permeability (∼4 fold higher dye uptake assay), ∼25% elevated in intracellular free-Ca concentration (FURA-2), activation of protein degradation via ubiquitin proteasome pathway (Murf and Atrogin 1 reactivity), moderate reduction in oxygen consumption not explained by changes in levels of relevant respiratory proteins, ∼3 fold decreased mitochondrial membrane potential (MitoTracker Red CMXRos) and ∼4 fold increased mitochondrial superoxide production (MitoSox). Since connexin hemichannels and P2X7 receptors are permeable to ions and small molecules, it is likely that they are main protagonists in the channelopathy by reducing the electrochemical gradient across the cell membrane resulting in detrimental metabolic changes and muscular atrophy.

Nutrient pattern analysis in critically ill patients using Omics technology (NAChO) - Study protocol for a prospective observational study

INTRODUCTION

Intensive care unit-acquired weakness (ICU-AW) is often observed in critically ill patients with prolonged intensive care unit (ICU) stay. We hypothesized that evolving metabolic abnormalities during prolonged ICU stay are reflected by changing nutrient patterns in blood, urine and skeletal muscle, and that these patterns differ in patients with/without ICU-AW and between patients with/without sepsis.

METHODS

In a prospective single-center observational trial, we aim to recruit 100 critically ill patients (ICU length of stay ≥ 5 days) with severe sepsis/septic shock ("sepsis group", n = 50) or severe head trauma/intracerebral hemorrhage ("CNS group", n = 50). Patients will be sub-grouped for presence or absence of ICU-AW as determined by the Medical Research Council sum score. Blood and urine samples will be collected and subjected to comprehensive nutrient analysis at different time points by targeted quantitative mass spectrometric methods. In addition, changes in muscular tissue (biopsy, when available), muscular architecture (ultrasound), electrophysiology, body composition analyses (bioimpedance, cerebral magnetic resonance imaging), along with clinical status will be assessed. Patients will be followed-up for 180 and 360 days including assessment of quality of life.

DISCUSSION

Key objective of this trial is to assess changes in nutrient pattern in blood and urine over time in critically ill patients with/without ICU-AW by using quantitative nutrient analysis techniques. Peer-reviewed published NAChO data will allow for a better understanding of metabolic changes in critically ill patients on standard liquid enteral nutrition and will likely open up new avenues for future therapeutic and nutritional interventions.

Pulmonary and muscle profile in pneumosepsis: A temporal analysis of inflammatory markers

In sepsis, greater understanding of the inflammatory mechanism involved would provide insights into the condition and into its extension to the muscular apparatus in critically ill patients. Therefore, this study evaluates the inflammatory profile of pneumosepsis induced by Klebsiella pneumoniae (K.p.) in lungs and skeletal muscles during the first 72 h. Male BALB/c mice were divided into 4 groups, submitted to intratracheal inoculation of K.p. at a concentration of 2 × 10⁸ (PS) or PBS, and assessed after 24 (PS24), 48 (PS48) and 72 (PS72) hours. The Maximum Physical Capacity Test (MPCT) was performed before and after induction. Pulmonary inflammation was assessed by total cell number, nitric oxide levels (NOx), IL-1β and TNF-α levels in bronchoalveolar lavage fluid (BALF); inflammation and muscle trophism were evaluated by the levels of TNF-α, IL-6, TGF-β and BDNF by ELISA and NF-κB by western blotting in muscle tissue. Cells and colony forming units (CFU) were also analyzed in blood samples. The PS groups showed an increase in total cells in the BALF (p < 0.05), as well in the number of granulocytes in the blood (p < 0.05) and a decrease in performance in the MPCT (p < 0.05). NOx levels showed significant increase in PS72, when compared to Control group (p = 0.03). The PS24 showed a significant increase lung in TNF-α levels (p < 0.001) and in CFU (p = 0.013). We observed an increase in muscular IL-6 and nuclear NF-κB levels in PS24 group, when compared to PS48 and Control groups (p < 0.05). Nevertheless, mild signs of injury in the skeletal muscle tissue does not support the idea of an early muscular injury in this experimental model, suggesting that the low performance of the animals during the MPCT may be related to lung inflammation.

Quantitative peripheral muscle ultrasound in sepsis: Muscle area superior to thickness

PURPOSE

The objective of this study is to describe the relationship between two quantitative muscle ultrasound measures, the rectus femoris cross-sectional area (RF-CSA) and quadriceps muscle thickness, with volitional measures of strength and function in critically ill patients with sepsis.

MATERIALS AND METHODS

We performed a prospective study of patients admitted to a medical ICU with sepsis and shock or respiratory failure. We examined the association of two ultrasound measurements - the RF-CSA and quadriceps muscle thickness - with strength and function at day 7. Strength was determined using the Medical Research Council Score and function using Physical Function in the ICU Test, scored.

RESULTS

Twenty-nine patients were enrolled; 19 patients had outcome testing performed. Over 7days, RF-CSA and thickness decreased by an average of 23.2% and 17.9%, respectively. The rate of change per day of RF-CSA displayed a moderate correlation with strength (ρ 0.51, p-value 0.03) on day 7. Baseline and day 7 RF-CSA did not show a significant correlation with either outcome. Quadriceps muscle thickness did not significantly correlate with either outcome.

CONCLUSIONS

Muscle atrophy as detected by the rate of change in RF-CSA moderately correlated with strength one week after sepsis admission.

Risk factors for intensive care unit-acquired weakness: A systematic review and meta-analysis

Intensive care unit-acquired weakness (ICUAW) occurs frequently in the context of critical illness without alternative plausible cause and specific treatment options, and it is important to identify and summarize the independent risk factors for ICUAW. PubMed, Embase, Central, China Biological Medicine, China National Knowledge Infrastructure, VIP and Wanfang databases were searched from database inception until 10 July 2017. Prospective cohort studies on adult ICU patients who were diagnosed with ICUAW using either clinical or electrophysiological criteria were selected. Meta-analysis was performed using Stata version 12.0. The results were analysed using odds ratios (OR) and 95% confidence intervals (CI). Data were pooled using a random-effects model, and heterogeneity was assessed using the I² statistic. Qualitative analysis and systematic review were used for risk factors that were deemed inappropriate to combine. Fourteen prospective cohort studies were included in this review. The meta-analysis showed that Acute Physiology and Chronic Health Evaluation II score (OR, 1.05; 95%CI, 1.01-1.10), neuromuscular blocking agents (OR, 2.03; 95%CI, 1.22-3.40) and aminoglycosides (OR, 2.27; 95%CI, 1.07-4.81) were found to be significantly associated with ICUAW. Other risk factors, including female, multiple organ failure, systemic inflammatory response syndrome, sepsis, electrolyte disturbances, hyperglycaemia, hyperosmolarity, high lactate level, duration of mechanical ventilation, parenteral nutrition and use of norepinephrine, were statistically significant on multivariable analysis in each single studies. This review provides a number of independent risk factors for ICUAW, which should be guided for early prediction and prevention of the disorder.

Electrophysiologic alterations in the excitability of the sciatic and vagus nerves during early stages of sepsis

Background

Nonspecific and delayed diagnosis of neurologic damage contributes to the development of neuropathies in patients with severe sepsis. The present study assessed the electrophysiologic parameters related to the excitability and conductibility of sciatic and vagus nerves during early stages of sepsis.

Materials and methods

Twenty-four hours after sepsis induced by cecal ligation and puncture (CLP) model, sciatic and vagus nerves of septic (CLP group) and control (sham group) rats were removed, and selected electric stimulations were applied to measure the parameters of the first and second components of the compound action potential. The first component originated from fibers with motor and sensory functions (Types Aα and Aβ fibers) with a large conduction velocity (70-120 m/s), and the second component originated from fibers (Type Aγ) with sensorial function. To evaluate the presence of sensorial alterations, the sensitivity to non-noxious mechanical stimuli was measured by using the von Frey test. Hematoxylin and eosin staining of the nerves was performed.

Results

We observed an increase of rheobase followed by a decrease in the first component amplitude and a higher paw withdrawal threshold in response to the application of von Frey filaments in sciatic nerves from the CLP group compared to the sham group. Differently, a decrease in rheobase and an increase in the first component amplitude of vagal C fibers from CLP group were registered. No significant morphologic alteration was observed.

Conclusion

Our data showed that the electrophysiologic alterations in peripheral nerves vary with the fiber type and might be identified in the first 24 h of sepsis, before clinical signs of neuromuscular disorders.

Nonvolitional assessment of tibialis anterior force and architecture during critical illness

INTRODUCTION

Contemporaneous measures of muscle architecture and force have not previously been conducted during critical illness to examine their relationship with intensive care unit (ICU)-acquired weakness.

METHODS

Ankle dorsiflexor muscle force (ADMF) with high-frequency electrical peroneal nerve stimulation and skeletal muscle architecture via ultrasound were measured in 21 adult, critically ill patients, 16 at ICU admission.

RESULTS

Thirteen patients were measured on 2 occasions. Among these, 10 who were measured at ICU admission demonstrated muscle weakness. Despite significant reductions in tibialis anterior (Δ = -88.5 ± 78.8 mm² , P = 0.002) and rectus femoris (Δ = -126.1 ± 129.1 mm² , P = 0.006) cross-sectional areas between occasions, ADMF did not change (100-HZ ankle dorsiflexor force 9.8 [IQR, 8.0-14.4] kg vs. 8.6 (IQR, 6.7-19.2) kg, P = 0.9).

DISCUSSION

Muscle weakness was evident at ICU admission. No additional decrements were observed 7 days later despite significant reductions in muscle size. These data suggest that not all ICU weakness is truly "acquired" and questions our understanding of muscle function during critical illness. Muscle Nerve 57: 964-972, 2018.

New device for nonvolitional evaluation of quadriceps force in ventilated patients

INTRODUCTION

In mechanically ventilated patients, nonvolitional assessment of quadriceps weakness using femoral-nerve stimulation (twitch force) while the leg rests on a right-angle trapezoid or dangles from the bed edge is impractical. Accordingly, we developed a knee-support apparatus for use in ventilated patients.

METHODS

Ninety subjects (12 ventilated patients, 28 ambulatory patients, and 50 healthy subjects) were enrolled. Twitches with leg-dangling, trapezoid, and knee-support setups were compared.

RESULTS

Knee-support twitches were similar to trapezoid twitches but smaller than leg-dangling twitches (P < 0.0001). Inter- and intraoperator agreement was high for knee-support twitches at 1 week and 1 month. In ventilated patients, knee-support twitches were smaller than in healthy subjects and ambulatory patients (P < 0.004).

DISCUSSION

The new knee-support apparatus allows accurate recording of quadriceps twitches. The ease of use in ventilated patients and excellent inter- and intraoperator agreement suggest that this technique is suitable for cross-sectional and longitudinal studies in critically ill patients. Muscle Nerve 57: 784-791, 2018.

Neuromuscular Recovery Is Prolonged After Immobilization or Superimposition of Inflammation With Immobilization Compared to Inflammation Alone: Data From a Preclinical Model

OBJECTIVES

Recovery from ICU-acquired muscle weakness extends beyond hospital stay. We hypothesized that immobilization, more than inflammation, plays a prominent role in the delayed recovery from critical illness.

DESIGN

Prospective, randomized, controlled, experimental study.

SETTING

Animal laboratory, university hospital.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Animals were divided to have one hind limb immobilized (n = 129) or sham-immobilized (n = 129) on day -12. After surgery, rats were further assigned to two subgroups. To induce inflammation, rats received three IV injections of Corynebacterium parvum on days -12, -8, and -4. Controls received saline at the respective time-points. At day 0, the limbs were remobilized and recovery from inflammation and/or immobilization was followed for 36 days.

MEASUREMENTS AND MAIN RESULTS

At day 0 and after 4, 12, or 36 days of recovery, maximum tetanic tension and tetanic fade (functional parameters = primary outcome variables) as well as nicotinic acetylcholine receptor expression, muscle mass, and histologic changes (structural parameters = secondary outcome variables) were measured. Impaired maximum tetanic tension, decreased tibialis muscle mass, and fiber diameter due to inflammation alone recovered by day 4. Tetanic fade was not affected by inflammation. Immobilization-induced loss of tibialis muscle mass, decreased fiber diameter, and tetanic fade did not return to normal until day 36, while maximum tetanic tension had recovered at that time. In the presence of inflammation and immobilization, the decrease in tibialis muscle mass, fiber diameter, and maximum tetanic tension, as well as decreased tetanic fade persisted until day 36. Up-regulation of nicotinic acetylcholine receptors normalized before day 4 following inflammation, but persisted until day 4 following immobilization.

CONCLUSIONS

In our model, muscle function and structure recovered from inflammation within 4-12 days. Immobilization-induced neuromuscular changes, however, persisted even at day 36, especially if inflammation was concomitant.

Critical illness myopathy in a cervical spine-injured patient

Neuromuscular weakness acquired in the intensive care unit (ICU) causes significant impairment in critically ill patients. The spectrum of critical illness neuromuscular disease includes critical illness myopathy, critical illness polyneuropathy or both, and occurs in approximately one-third of patients admitted to the ICU and those who are ventilated for at least 7 days. Recognized risk factors include sepsis, systemic inflammatory response syndrome, multi-organ failure, neuromuscular blocking agents and corticosteroids, however the absence of predisposing factors should not preclude critical illness neuromuscular disease. A 23-year-old male suffered a cervical spine injury and was admitted to the ICU. Two weeks post admission, he lost all power in his upper limbs, neck and face. Nerve conduction studies and needle electromyography were performed 4 weeks and 3 months after the injury, suggesting that myopathy was the likely cause of weakness. The definitive diagnosis of critical illness myopathy was based on muscle biopsy demonstrating myosin filament loss. Evaluation of new-onset weakness in ICU patients is essential to distinguish neurological causes from complications of critical illness. Signs and symptoms of critical illness neuromuscular disease must be identified early to encourage recovery, promote rehabilitation, and reduce morbidity and mortality.

Acquired Muscle Weakness in the Surgical Intensive Care Unit

Muscle weakness is common in the surgical intensive care unit (ICU). Low muscle mass at ICU admission is a significant predictor of adverse outcomes. The consequences of ICU-acquired muscle weakness depend on the underlying mechanism. Temporary drug-induced weakness when properly managed may not affect outcome. Severe perioperative acquired weakness that is associated with adverse outcomes (prolonged mechanical ventilation, increases in ICU length of stay, and mortality) occurs with persistent (time frame: days) activation of protein degradation pathways, decreases in the drive to the skeletal muscle, and impaired muscular homeostasis. ICU-acquired muscle weakness can be prevented by early treatment of the underlying disease, goal-directed therapy, restrictive use of immobilizing medications, optimal nutrition, activating ventilatory modes, early rehabilitation, and preventive drug therapy. In this article, the authors review the nosology, epidemiology, diagnosis, and prevention of ICU-acquired weakness in surgical ICU patients.

Systemic symptoms predict presence or development of severe sepsis and septic shock

BACKGROUND

Severe sepsis is a major cause of mortality and morbidity globally. As the time to adequate treatment is directly linked to outcome, early recognition is of critical importance. Early, accessible markers for severe sepsis are desirable. The systemic inflammatory response in sepsis leads to changes in vital signs and biomarkers and to symptoms unrelated to the focus of infection. This study investigated whether the occurrence of any of six systemic symptoms could predict severe sepsis in a cohort of patients admitted to hospital for suspected bacterial infections.

METHODS

A retrospective, consecutive study was conducted. All adult patients admitted during 1 month to a 550-bed secondary care hospital in western Sweden and given intravenous antibiotics for suspected community-acquired infection were included (n = 289). Symptoms (fever/chills, muscle weakness, localised pain, dyspnea, altered mental status and gastrointestinal symptoms) were registered along with age, sex, vital signs and laboratory values. Patients who fulfilled criteria of severe sepsis within 48 h were compared with patients who did not. Odds ratios for severe sepsis were calculated, adjusted for age, sex and comorbidities.

RESULTS

Criteria for severe sepsis were fulfilled by 90/289 patients (31.1%). Altered mental status (OR = 4.29, 95% CI = 2.03-9.08), dyspnea (OR = 2.92, 95% CI = 1.69-5.02), gastrointestinal symptoms (OR = 2.31, 95% CI = 1.14-4.69) and muscle weakness (OR = 2.24, 95% CI = 1.06-4.75) were more common in patients who had or later developed severe sepsis.

CONCLUSIONS

Systemic symptoms in combination with other signs of infection should be considered warning signs of severe sepsis.

Clinical review: intensive care unit acquired weakness

A substantial number of patients admitted to the ICU because of an acute illness, complicated surgery, severe trauma, or burn injury will develop a de novo form of muscle weakness during the ICU stay that is referred to as “intensive care unit acquired weakness” (ICUAW). This ICUAW evoked by critical illness can be due to axonal neuropathy, primary myopathy, or both. Underlying pathophysiological mechanisms comprise microvascular, electrical, metabolic, and bioenergetic alterations, interacting in a complex way and culminating in loss of muscle strength and/or muscle atrophy. ICUAW is typically symmetrical and affects predominantly proximal limb muscles and respiratory muscles, whereas facial and ocular muscles are often spared. The main risk factors for ICUAW include high severity of illness upon admission, sepsis, multiple organ failure, prolonged immobilization, and hyperglycemia, and also older patients have a higher risk. The role of corticosteroids and neuromuscular blocking agents remains unclear. ICUAW is diagnosed in awake and cooperative patients by bedside manual testing of muscle strength and the severity is scored by the Medical Research Council sum score. In cases of atypical clinical presentation or evolution, additional electrophysiological testing may be required for differential diagnosis. The cornerstones of prevention are aggressive treatment of sepsis, early mobilization, preventing hyperglycemia with insulin, and avoiding the use parenteral nutrition during the first week of critical illness. Weak patients clearly have worse acute outcomes and consume more healthcare resources. Recovery usually occurs within weeks or months, although it may be incomplete with weakness persisting up to 2 years after ICU discharge. Prognosis appears compromised when the cause of ICUAW involves critical illness polyneuropathy, whereas isolated critical illness myopathy may have a better prognosis. In addition, ICUAW has shown to contribute to the risk of 1-year mortality. Future research should focus on new preventive and/or therapeutic strategies for this detrimental complication of critical illness and on clarifying how ICUAW contributes to poor longer-term prognosis.

A Novel Noninvasive Method for Measuring Fatigability of the Quadriceps Muscle in Noncooperating Healthy Subjects

Background. Critical illness is associated with muscle weakness leading to long-term functional limitations. Objectives. To assess the reliability of a novel method for evaluating fatigability of the quadriceps muscle in noncooperating healthy subjects. Methods. On two occasions, separated by seven days, nonvoluntary isometric contractions (twitch and tetanic) of the quadriceps femoris muscle evoked by transcutaneous electrical muscle stimulation were recorded in twelve healthy adults. For tetanic contractions, the Fatigue Index (ratio of peak torque values) and the slope of the regression line of peak torque values were primary outcome measures. For twitch contractions, maximum peak torque and rise time were calculated. Relative (intraclass correlation, ICC_3.1) and absolute (standard error of measurement, SEM) reliability were assessed and minimum detectable change was calculated using a 95% confidence interval (MDC_95%). Results. The Fatigue Index (ICC_3.1, 0.84; MDC_95%, 0.12) and the slope of the regression line (ICC_3.1, 0.99; MDC_95%, 0.03) showed substantial relative and absolute reliability during the first 15 and 30 contractions, respectively. Conclusion. This method for assessing fatigability of the quadriceps muscle produces reliable results in healthy subjects and may provide valuable data on quantitative changes in muscle working capacity and treatment effects in patients who are incapable of producing voluntary muscle contractions.

The Sick and the Weak: Neuropathies/Myopathies in the Critically Ill

Critical illness polyneuropathies (CIP) and myopathies (CIM) are common complications of critical illness. Several weakness syndromes are summarized under the term intensive care unit-acquired weakness (ICUAW). We propose a classification of different ICUAW forms (CIM, CIP, sepsis-induced, steroid-denervation myopathy) and pathophysiological mechanisms from clinical and animal model data. Triggers include sepsis, mechanical ventilation, muscle unloading, steroid treatment, or denervation. Some ICUAW forms require stringent diagnostic features; CIM is marked by membrane hypoexcitability, severe atrophy, preferential myosin loss, ultrastructural alterations, and inadequate autophagy activation while myopathies in pure sepsis do not reproduce marked myosin loss. Reduced membrane excitability results from depolarization and ion channel dysfunction. Mitochondrial dysfunction contributes to energy-dependent processes. Ubiquitin proteasome and calpain activation trigger muscle proteolysis and atrophy while protein synthesis is impaired. Myosin loss is more pronounced than actin loss in CIM. Protein quality control is altered by inadequate autophagy. Ca(2+) dysregulation is present through altered Ca(2+) homeostasis. We highlight clinical hallmarks, trigger factors, and potential mechanisms from human studies and animal models that allow separation of risk factors that may trigger distinct mechanisms contributing to weakness. During critical illness, altered inflammatory (cytokines) and metabolic pathways deteriorate muscle function. ICUAW prevention/treatment is limited, e.g., tight glycemic control, delaying nutrition, and early mobilization. Future challenges include identification of primary/secondary events during the time course of critical illness, the interplay between membrane excitability, bioenergetic failure and differential proteolysis, and finding new therapeutic targets by help of tailored animal models.

Physical activity, muscle strength, and exercise capacity 3 months after severe sepsis and septic shock

PURPOSE

To quantify the physical activity in daily life (PADL), muscle strength, and exercise capacity in the short and medium term in survivors of severe sepsis and septic shock.

METHODS

Prospective cohort study with a follow-up from hospital admission to 3 months after hospital discharge. Seventy-two patients admitted to the ICU for severe sepsis or septic shock and a control group of healthy sedentary subjects (n = 50) were enrolled. All patients had their PADL quantified by an accelerometer during their hospital stay and 3 months after. Exercise capacity and handgrip and quadriceps muscle strength were also evaluated.

RESULTS

During hospitalization, patients spent the majority of their time inactive in a lying or sitting position (90 ± 34% of daily time). Physical inactivity was partially reduced 3 months after (58 ± 20% of daily time). However, the time patients spent walking was only 63% of the time reported for healthy subjects. Patients also showed lower movement intensity when compared with controls (2.1 ± 0.3 vs 2.5 ± 0.4 m/s(2)). At hospital discharge, muscle strength and exercise capacity were approximately 54% of the predicted value, and these parameters showed significant increase in patients 3 months after (70% of predicted value). Multivariable analysis demonstrated that the use of systemic corticosteroids and hospitalization time negatively influenced quadriceps strength and exercise capacity at the time of hospital discharge.

CONCLUSION

Our results suggest that survivors of sepsis admitted to the ICU have a substantial reduction in physical activity, exercise capacity, and muscle strength compared to healthy subjects that persist even 3 months after hospital discharge.

Exercise rehabilitation following intensive care unit discharge for recovery from critical illness

BACKGROUND

Skeletal muscle wasting and weakness are significant complications of critical illness, associated with degree of illness severity and periods of reduced mobility during mechanical ventilation. They contribute to the profound physical and functional deficits observed in survivors. These impairments may persist for many years following discharge from the intensive care unit (ICU) and can markedly influence health-related quality of life. Rehabilitation is a key strategy in the recovery of patients after critical illness. Exercise-based interventions are aimed at targeting this muscle wasting and weakness. Physical rehabilitation delivered during ICU admission has been systematically evaluated and shown to be beneficial. However, its effectiveness when initiated after ICU discharge has yet to be established.

OBJECTIVES

To assess the effectiveness of exercise rehabilitation programmes, initiated after ICU discharge, for functional exercise capacity and health-related quality of life in adult ICU survivors who have been mechanically ventilated longer than 24 hours.

SEARCH METHODS

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL), Ovid SP MEDLINE, Ovid SP EMBASE and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) via EBSCO host to 15 May 2014. We used a specific search strategy for each database. This included synonyms for ICU and critical illness, exercise training and rehabilitation. We searched the reference lists of included studies and contacted primary authors to obtain further information regarding potentially eligible studies. We also searched major clinical trials registries (Clinical Trials and Current Controlled Trials) and the personal libraries of the review authors. We applied no language or publication restriction. We reran the search in February 2015 and will deal with the three studies of interest when we update the review.

SELECTION CRITERIA

We included randomized controlled trials (RCTs), quasi-RCTs and controlled clinical trials (CCTs) that compared an exercise intervention initiated after ICU discharge versus any other intervention or a control or 'usual care' programme in adult (≥ 18 years) survivors of critical illness.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by the Cochrane Collaboration.

MAIN RESULTS

We included six trials (483 adult ICU participants). Exercise-based interventions were delivered on the ward in two studies; both on the ward and in the community in one study; and in the community in three studies. The duration of the intervention varied according to length of hospital stay following ICU discharge (up to a fixed duration of 12 weeks).Risk of bias was variable for all domains across all trials. High risk of bias was evident in all studies for performance bias, although blinding of participants and personnel in therapeutic rehabilitation trials can be pragmatically challenging. For other domains, at least half of the studies were at low risk of bias. One study was at high risk of selection bias, attrition bias and other sources of bias. Risk of bias was unclear for the remaining studies across domains. We decided not to undertake a meta-analysis because of variation in study design, types of interventions and outcome measurements. We present a narrative description of individual studies for each outcome.All six studies assessed functional exercise capacity, although we noted wide variability in the nature of interventions, outcome measures and associated metrics and data reporting. Overall quality of the evidence was very low. Individually, three studies reported positive results in favour of the intervention. One study found a small short-term benefit in anaerobic threshold (mean difference (MD) 1.8 mL O2/kg/min, 95% confidence interval (CI) 0.4 to 3.2; P value = 0.02). In a second study, both incremental (MD 4.7, 95% CI 1.69 to 7.75 watts; P value = 0.003) and endurance (MD 4.12, 95% CI 0.68 to 7.56 minutes; P value = 0.021) exercise testing results were improved with intervention. Finally self reported physical function increased significantly following use of a rehabilitation manual (P value = 0.006). Remaining studies found no effect of the intervention.Similar variability was evident with regard to findings for the primary outcome of health-related quality of life. Only two studies evaluated this outcome. Individually, neither study reported differences between intervention and control groups for health-related quality of life due to the intervention. Overall quality of the evidence was very low.Four studies reported rates of withdrawal, which ranged from 0% to 26.5% in control groups, and from 8.2% to 27.6% in intervention groups. The quality of evidence for the effect of the intervention on withdrawal was low. Very low-quality evidence showed rates of adherence with the intervention. Mortality ranging from 0% to 18.8% was reported by all studies. The quality of evidence for the effect of the intervention on mortality was low. Loss to follow-up, as reported in all studies, ranged from 0% to 14% in control groups, and from 0% to 12.5% in intervention groups, with low quality of evidence. Only one non-mortality adverse event was reported across all participants in all studies (a minor musculoskeletal injury), and the quality of the evidence was low.

AUTHORS' CONCLUSIONS

At this time, we are unable to determine an overall effect on functional exercise capacity, or on health-related quality of life, of an exercise-based intervention initiated after ICU discharge for survivors of critical illness. Meta-analysis of findings was not appropriate because the number of studies and the quantity of data were insufficient. Individual study findings were inconsistent. Some studies reported a beneficial effect of the intervention on functional exercise capacity, and others did not. No effect on health-related quality of life was reported. Methodological rigour was lacking across several domains, influencing the quality of the evidence. Wide variability was noted in the characteristics of interventions, outcome measures and associated metrics and data reporting.If further trials are identified, we may be able to determine the effects of exercise-based intervention following ICU discharge on functional exercise capacity and health-related quality of life among survivors of critical illness.

TNF alpha inhibits myogenic differentiation of C2C12 cells through NF-κB activation and impairment of IGF-1 signaling pathway

Cachexia or muscle wasting is a common condition that occurs in many chronic diseases. The wasting conditions are characterized by increased levels of TNF-α which was also known as cachectin in the past. But how TNF-α exerts its cachetic effects remains controversial. To clarify this issue, we investigated the impact of TNF-α on C2C12 cell myogenic differentiation. Our results demonstrate that myotube formation was completely inhibited by TNF-α when added to differentiating C2C12 myoblasts. The inhibitory effect of TNF-α on differentiation was accompanied by activation of NF-κB and down regulation of myogenin and Akt. Importantly, TNF-α's effect on differentiation was abolished when IGF-1 was added to the culture. IGF-1 treatment also inhibited NF-κB reporter activity and restored Akt levels. Our data suggest that TNF-α inhibits myogenic differentiation through NF-κB activation and impairment of IGF-1 signaling pathway. The reversal of TNF-α induced inhibition of myogenesis by IGF-1 may have significant therapeutic potential.

Alterations in respiratory and limb muscle strength and size in patients with sepsis who are mechanically ventilated

BACKGROUND

Skeletal muscle wasting and weakness are common in patients with sepsis in the intensive care unit, although less is known about deficits in diaphragm and limb muscles when mechanical ventilation also is required.

OBJECTIVE

The objective of this study was to concurrently investigate relative differences in both thickness and strength of respiratory and peripheral muscles during routine care.

DESIGN

A prospective, cross-sectional study of 16 alert patients with sepsis and 16 people who were healthy (control group) was used.

METHODS

Assessment was made of the diaphragm, upper arm, forearm, and thigh muscle thicknesses with the use of ultrasound; respiratory muscle strength by means of maximal inspiratory pressure; and isometric handgrip, elbow flexion, and knee extension forces with the use of portable dynamometry. To describe relative changes, data also were normalized to fat-free body mass (FFM) measured by bioelectrical impedance spectroscopy.

RESULTS

Patients (9 men, 7 women; mean age=62 years, SD=17) were assessed after a median of 16 days (interquartile range=11-29) of intensive care unit admission. Patients' diaphragm thickness did not differ from that of the control group, even for a given FFM. When normalized to FFM, only the difference in patients' mid-thigh muscle size significantly deviated from that of the control group. Within the patient sample, all peripheral muscle groups were thinner compared with the diaphragm. Patients were significantly weaker than were the control group participants in all muscle groups, including for a given FFM. Within the critically ill group, limb weakness was greater than the already-significant respiratory muscle weakness.

LIMITATIONS

Volitional strength tests were applied such that successive measurements from earlier in the course of illness could not be reliably obtained.

CONCLUSIONS

When measured at bedside, survivors of sepsis and a period of mechanical ventilation may have respiratory muscle weakness without remarkable diaphragm wasting. Furthermore, deficits in peripheral muscle strength and size may exceed those in the diaphragm.

Exercise training prevents TNF-α induced loss of force in the diaphragm of mice

Rationale

Inflammatory cytokines like tumor necrosis factor alpha (TNF-α) are elevated in congestive heart failure and are known to induce the production of reactive oxygen species as well as to deteriorate respiratory muscle function.

Objectives

Given the antioxidative effects of exercise training, the aim of the present study was to investigate if exercise training is capable of preventing a TNF-α induced loss of diaphragmatic force in mice and, if so, to elucidate the potential underlying mechanisms.

Methods

Prior to intraperitoneal injection of TNF-α or saline, C57Bl6 mice were assigned to four weeks of exercise training or sedentary behavior. Diaphragmatic force and power generation were determined in vitro. Expression/activity of radical scavenger enzymes, enzymes producing reactive oxygen species and marker of oxidative stress were measured in the diaphragm.

Main Results

In sedentary animals, TNF-α reduced specific force development by 42% concomitant with a 2.6-fold increase in the amount of carbonylated α-actin and creatine kinase. Furthermore, TNF-α led to an increased NAD(P)H oxidase activity in both sedentary and exercised mice whereas xanthine oxidase activity and intramitochondrial ROS production was only enhanced in sedentary animals by TNF-α. Exercise training prevented the TNF-α induced force reduction and led to an enhanced mRNA expression and activity of glutathione peroxidase. Carbonylation of proteins, in particular of α-actin and creatine kinase, was diminished by exercise training.

Conclusion

TNF-α reduces the force development in the diaphragm of mice. This effect is almost abolished by exercise training. This may be a result of reduced carbonylation of proteins due to the antioxidative properties of exercise training.

Global muscle strength but not grip strength predicts mortality and length of stay in a general population in a surgical intensive care unit

BACKGROUND

Paresis acquired in the intensive care unit (ICU) is common in patients who are critically ill and independently predicts mortality and morbidity. Manual muscle testing (MMT) and handgrip dynamometry assessments have been used to evaluate muscle weakness in patients in a medical ICU, but similar data for patients in a surgical ICU (SICU) are limited.

OBJECTIVE

The purpose of this study was to evaluate the predictive value of strength measured by MMT and handgrip dynamometry at ICU admission for in-hospital mortality, SICU length of stay (LOS), hospital LOS, and duration of mechanical ventilation.

DESIGN

This investigation was a prospective, observational study.

METHODS

One hundred ten patients were screened for eligibility for testing in the SICU of a large, academic medical center. The Acute Physiology and Chronic Health Evaluation (APACHE) II score, diagnoses, and laboratory data were collected. Measurements were obtained by MMT quantified with the sum (total) score on the Medical Research Council Scale and by handgrip dynamometry. Outcome data, including in-hospital mortality, SICU LOS, hospital LOS, and duration of mechanical ventilation, were collected for all participants.

RESULTS

One hundred seven participants were eligible for testing; 89% were tested successfully at a median of 3 days (25th-75th percentiles=3-6 days) after admission. Sedation was the most frequent barrier to testing (70.6%). Manual muscle testing was identified as an independent predictor of mortality, SICU LOS, hospital LOS, and duration of mechanical ventilation. Grip strength was not independently associated with these outcomes.

LIMITATIONS

This study did not address whether muscle weakness translates to functional outcome impairment.

CONCLUSIONS

In contrast to handgrip strength, MMT reliably predicted in-hospital mortality, duration of mechanical ventilation, SICU LOS, and hospital LOS.

The surgical intensive care unit optimal mobility score predicts mortality and length of stay

OBJECTIVES

To test if the surgical intensive care unit optimal mobility score predicts mortality and intensive care unit and hospital length of stay.

DESIGN

Prospective single-center cohort study.

SETTING

Surgical intensive care unit of the Massachusetts General Hospital.

PATIENTS

One hundred thirteen consecutive patients admitted to the surgical intensive care unit.

INVESTIGATIONS

We tested the hypotheses that the surgical intensive care unit optimal mobility score independent of comorbidity index, Acute Physiology and Chronic Health Evaluation II, creatinine, hypotension, hypernatremia, acidosis, hypoxia, and hypercarbia predicts hospital mortality, surgical intensive care unit and total hospital length of stay.

MEASUREMENTS AND MAIN RESULTS

Two nurses independently predicted the patients' mobilization capacity by using the surgical intensive care unit optimal mobility score the morning after admission, whereas a third nurse recorded the achieved mobilization levels of patients at the end of the day. A multidisciplinary expert team measured patients' grip strength and assessed their predicted mobilization capacity independently. Multivariate analysis revealed that the surgical intensive care unit optimal mobility score was the only independent predictor of mortality. Surgical intensive care unit optimal mobility score, hypotension, and hypernatremia (>144 mmol/L) independently predicted intensive care unit length of stay, whereas the surgical intensive care unit optimal mobility score and hypernatremia predicted total hospital length of stay. The Acute Physiology and Chronic Health Evaluation II score was not identified in the multivariate analysis. The surgical intensive care unit optimal mobility score was also a reliable and valid instrument in predicting achieved mobilization levels of patients.

CONCLUSIONS

In surgical critically ill patients presenting without preexisting impairment of functional mobility, the surgical intensive care unit optimal mobility score is a reliable and valid tool to predict mortality and intensive care unit and hospital length of stay.

Early rehabilitation in sepsis: a prospective randomised controlled trial investigating functional and physiological outcomes The i-PERFORM Trial (Protocol Article)

BACKGROUND

Patients with sepsis syndromes in comparison to general intensive care patients can have worse outcomes for physical function, quality of life and survival. Early intensive care rehabilitation can improve the outcome in general Intensive Care Unit (ICU) patients, however no investigations have specifically looked at patients with sepsis syndromes. The 'i-PERFORM Trial' will investigate if early targeted rehabilitation is both safe and effective in patients with sepsis syndromes admitted to ICU.

METHODS/DESIGN

A single-centred blinded randomized controlled trial will be conducted in Brisbane, Australia. Participants (n = 252) will include those ≥ 18 years, mechanically ventilated for ≥ 48 hours and diagnosed with a sepsis syndrome. Participants will be randomised to an intervention arm which will undergo an early targeted rehabilitation program according to the level of arousal, strength and cardiovascular stability and a control group which will receive normal care.The primary outcome measures will be physical function tests on discharge from ICU (The Acute Care Index of Function and The Physical Function ICU Test). Health-related quality of life will be measured using the Short Form-36 and the psychological component will be tested using The Hospital Anxiety and Depression Scale. Secondary measures will include inflammatory biomarkers; Interleukin-6, Interleukin-10 and Tumour Necrosis Factor-α, peripheral blood mitochondrial DNA content and lactate, fat free muscle mass, tissue oxygenation and microcirculatory flow.

DISCUSSION

The 'i-PERFORM Trial' will determine whether early rehabilitation for patients with sepsis is effective at improving patient outcomes with functional and physiological parameters reflecting long and short-term effects of early exercise and the safety in its application in critical illness.

TRIAL REGISTRATION

Australia and New Zealand Clinical Trials Register (ANZCTR): ACTRN12610000808044.

Tumor necrosis factor-α regulates distinct molecular pathways and gene networks in cultured skeletal muscle cells

Background

Skeletal muscle wasting is a debilitating consequence of large number of disease states and conditions. Tumor necrosis factor-α (TNF-α) is one of the most important muscle-wasting cytokine, elevated levels of which cause significant muscular abnormalities. However, the underpinning molecular mechanisms by which TNF-α causes skeletal muscle wasting are less well-understood.

Methodology/Principal Findings

We have used microarray, quantitative real-time PCR (QRT-PCR), Western blot, and bioinformatics tools to study the effects of TNF-α on various molecular pathways and gene networks in C2C12 cells (a mouse myoblastic cell line). Microarray analyses of C2C12 myotubes treated with TNF-α (10 ng/ml) for 18h showed differential expression of a number of genes involved in distinct molecular pathways. The genes involved in nuclear factor-kappa B (NF-kappaB) signaling, 26s proteasome pathway, Notch1 signaling, and chemokine networks are the most important ones affected by TNF-α. The expression of some of the genes in microarray dataset showed good correlation in independent QRT-PCR and Western blot assays. Analysis of TNF-treated myotubes showed that TNF-α augments the activity of both canonical and alternative NF-κB signaling pathways in myotubes. Bioinformatics analyses of microarray dataset revealed that TNF-α affects the activity of several important pathways including those involved in oxidative stress, hepatic fibrosis, mitochondrial dysfunction, cholesterol biosynthesis, and TGF-β signaling. Furthermore, TNF-α was found to affect the gene networks related to drug metabolism, cell cycle, cancer, neurological disease, organismal injury, and abnormalities in myotubes.

Conclusions

TNF-α regulates the expression of multiple genes involved in various toxic pathways which may be responsible for TNF-induced muscle loss in catabolic conditions. Our study suggests that TNF-α activates both canonical and alternative NF-κB signaling pathways in a time-dependent manner in skeletal muscle cells. The study provides novel insight into the mechanisms of action of TNF-α in skeletal muscle cells.

Inhibition of monocyte chemoattractant protein-1 prevents diaphragmatic inflammation and maintains contractile function during endotoxemia

Introduction

Respiratory muscle weakness is common in sepsis patients. Proinflammatory mediators produced during sepsis have been implicated in diaphragmatic contractile dysfunction, but the role of chemokines has not been explored. This study addressed the role of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), in the pathogenesis of diaphragmatic inflammation and weakness during endotoxemia.

Methods

Mice were treated as follows (n = 6 per group): (a) saline, (b) endotoxin (25 μg/g IP), (c) endotoxin + anti-MCP-1 antibody, and (d) endotoxin + isotype control antibody. Muscles were also exposed to recombinant MCP-1 in vivo and in vitro. Measurements were made of diaphragmatic force generation, leukocyte infiltration, and proinflammatory mediator (MCP-1, IL-1α, IL-1β, IL-6, NF-κB) expression/activity.

Results

In vivo, endotoxin-treated mice showed a large decrease in diaphragmatic force, together with upregulation of MCP-1 and other cytokines, but without an increase in intramuscular leukocytes. Antibody neutralization of MCP-1 prevented the endotoxin-induced force loss and reduced expression of MCP-1, IL-1α, IL-1β, and IL-6 in the diaphragm. MCP-1 treatment of nonseptic muscles also led to contractile weakness, and MCP-1 stimulated its own transcription independent of NF-κB activation in vitro.

Conclusions

These results suggest that MCP-1 plays an important role in the pathogenesis of diaphragmatic weakness during sepsis by both direct and indirect mechanisms. We speculate that its immunomodulatory properties and ability to modify skeletal muscle function make MCP-1 a potential therapeutic target in critically ill patients with sepsis and associated respiratory muscle weakness.

Surgical Intensive Care Unit Mobility is Increased after Institution of a Computerized Mobility Order Set and Intensive Care Unit Mobility Protocol: A Prospective Cohort Analysis

In some populations, intensive care unit (ICU) mobility has been shown to be safe and beneficial. We gathered data on 50 nonintubated surgical patients in a 10-bed surgical ICU (SICU) who met physiologic inclusion criteria beginning in May 2008 (A group). In January 2009, we began mandatory entry of computerized mobility orders as part of a standardized ICU order set. We also created a mobility protocol for nurses in this ICU. We then collected data on 50 patients in this postintervention cohort (B group). Both groups had similar baseline characteristics. A group patients had some form of mobility orders entered in 29 patients (58%) versus 47 patients (82%) in the B group, P < 0.05. In the A group, 11 patients (22%) were mobilized; in the B group, 40 patients (80%) were mobilized, P < 0.05. In our SICU patient population, mandatory entry of computerized mobility orders as part of a standard SICU order set and establishment of an ICU mobility nursing protocol was associated with an increase in number of mobility orders entered as well as an increase in SICU patient activity. Further studies should focus on measurement of the effect of mobility interventions on patient outcomes.

Critical illness polyneuropathy and myopathy in the intensive care unit

Critical illness polyneuropathy (CIP) and critical illness myopathy (CIM) are major complications that occur in severely ill patients who require intensive care treatment. CIP and CIM affect the limb and respiratory muscles, and, as a consequence, they characteristically complicate weaning from the ventilator, increase the length of stay on the intensive care unit, and prolong physical rehabilitation. The basic pathophysiology of both disorders is complex and involves metabolic, inflammatory and bioenergetic alterations. It is unclear at present whether CIP and CIM are distinct entities, or whether they just represent different 'organ' manifestations of a common pathophysiological mechanism. This article provides an overview of the clinical and diagnostic features of CIP and CIM and discusses current pathophysiological and therapeutic concepts relating to these neuromuscular disorders.

Sepsis-induced myopathy

Sepsis is a major cause of morbidity and mortality in critically ill patients, and despite advances in management, mortality remains high. In survivors, sepsis increases the risk for the development of persistent acquired weakness syndromes affecting both the respiratory muscles and the limb muscles. This acquired weakness results in prolonged duration of mechanical ventilation, difficulty weaning, functional impairment, exercise limitation, and poor health-related quality of life. Abundant evidence indicates that sepsis induces a myopathy characterized by reductions in muscle force-generating capacity, atrophy (loss of muscle mass), and altered bioenergetics. Sepsis elicits derangements at multiple subcellular sites involved in excitation contraction coupling, such as decreasing membrane excitability, injuring sarcolemmal membranes, altering calcium homeostasis due to effects on the sarcoplasmic reticulum, and disrupting contractile protein interactions. Muscle wasting occurs later and results from increased proteolytic degradation as well as decreased protein synthesis. In addition, sepsis produces marked abnormalities in muscle mitochondrial functional capacity and when severe, these alterations correlate with increased death. The mechanisms leading to sepsis-induced changes in skeletal muscle are linked to excessive localized elaboration of proinflammatory cytokines, marked increases in free-radical generation, and activation of proteolytic pathways that are upstream of the proteasome including caspase and calpain. Emerging data suggest that targeted inhibition of these pathways may alter the evolution and progression of sepsis-induced myopathy and potentially reduce the occurrence of sepsis-mediated acquired weakness syndromes.

A framework for diagnosing and classifying intensive care unit-acquired weakness

Neuromuscular dysfunction is prevalent in critically ill patients, is associated with worse short-term outcomes, and is a determinant of long-term disability in intensive care unit survivors. Diagnosis is made with the help of clinical, electrophysiological, and morphological observations; however, the lack of a consistent nomenclature remains a barrier to research. We propose a simple framework for diagnosing and classifying neuromuscular disorders acquired in critical illness.

Skeletal muscle contractile properties and proinflammatory cytokine gene expression in human endotoxaemia

Background

Muscle dysfunction associated with sepsis contributes to morbidity and mortality but the underlying mechanisms are unclear. This study examined whether muscle weakness relates to an intrinsic defect in contraction, or to central mechanisms associated with acute illness, and whether systemic endotoxaemia induces changes in gene expression for proinflammatory cytokines within human muscle in vivo.

Methods

In this experimental study, 12 healthy men received intravenous Escherichia coli lipopolysaccharide (LPS, 4 ng/kg) or saline (control). Voluntary and electrically stimulated quadriceps contraction, and tumour necrosis factor (TNF) α mRNA expression in quadriceps muscle biopsies were studied before and after the infusion.

Results

Endotoxaemia induced transient weakness of voluntary quadriceps contraction, equivalent to a 7·8 (95 per cent confidence interval 2·1 to 13·5) per cent reduction in contractile force at 180 min (P = 0·027) and a 9·0 (5·2 to 12·8) per cent reduction at 300 min (P = 0·008). Electrically stimulated contraction was unaffected. LPS administration resulted in an apparent fibre-specific induction of TNF-α mRNA.

Conclusion

Endotoxaemia results in a reduction in voluntary muscle contractile force without an apparent defect in stimulated muscle contraction. Loss of volition may be a more important factor than intrinsic dysfunction in acute sepsis-associated human muscle weakness.

Electrical muscle stimulation preserves the muscle mass of critically ill patients: a randomized study

Introduction

Critically ill patients are characterized by increased loss of muscle mass, partially attributed to sepsis and multiple organ failure, as well as immobilization. Recent studies have shown that electrical muscle stimulation (EMS) may be an alternative to active exercise in chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) patients with myopathy. The aim of our study was to investigate the EMS effects on muscle mass preservation of critically ill patients with the use of ultrasonography (US).

Methods

Forty-nine critically ill patients (age: 59 ± 21 years) with an APACHE II admission score ≥13 were randomly assigned after stratification upon admission to receive daily EMS sessions of both lower extremities (EMS-group) or to the control group (control group). Muscle mass was evaluated with US, by measuring the cross sectional diameter (CSD) of the vastus intermedius and the rectus femoris of the quadriceps muscle.

Results

Twenty-six patients were finally evaluated. Right rectus femoris and right vastus intermedius CSD decreased in both groups (EMS group: from 1.42 ± 0.48 to 1.31 ± 0.45 cm, P = 0.001 control group: from 1.59 ± 0.53 to 1.37 ± 0.5 cm, P = 0.002; EMS group: from 0.91 ± 0.39 to 0.81 ± 0.38 cm, P = 0.001 control group: from 1.40 ± 0.64 to 1.11 ± 0.56 cm, P = 0.004, respectively). However, the CSD of the right rectus femoris decreased significantly less in the EMS group (-0.11 ± 0.06 cm, -8 ± 3.9%) as compared to the control group (-0.21 ± 0.10 cm, -13.9 ± 6.4%; P < 0.05) and the CSD of the right vastus intermedius decreased significantly less in the EMS group (-0.10 ± 0.05 cm, -12.5 ± 7.4%) as compared to the control group (-0.29 ± 0.28 cm, -21.5 ± 15.3%; P < 0.05).

Conclusions

EMS is well tolerated and seems to preserve the muscle mass of critically ill patients. The potential use of EMS as a preventive and rehabilitation tool in ICU patients with polyneuromyopathy needs to be further investigated.

Trial Registration

clinicaltrials.gov: NCT00882830

Short-term systemic effect of electrical muscle stimulation in critically ill patients

BACKGROUND

Our study assessed the short-term effect of electrical muscle stimulation (EMS) of the lower extremities on the thenar muscle microcirculation of patients who are critically ill.

METHODS

Twenty-nine hospital ICU patients (19 men; mean [+/- SD] age, 58 +/- 19 years; mean acute physiology and chronic health evaluation score, 17 +/- 5; mean sequential organ failure assessment score, 9 +/- 3) underwent a 45-min session of EMS of the lower extremities. BP and heart rate were measured, and blood samples were retrieved. Tissue oxygen saturation (Sto(2)) was assessed with near infrared spectroscopy at the thenar muscle with a vascular occlusion before and after EMS. A control group of six patients who were critically ill (4 men; mean age, 50 +/- 19 years) also were included in the study.

RESULTS

The mean Sto(2) did not differ significantly before and after the EMS session (81 +/- 16% vs 83 +/- 16%, respectively). The oxygen consumption rate during vascular occlusion differed significantly before the beginning and at the end of the session (20 +/- 9%/min vs 22 +/- 9%/min, respectively; p < 0.05). The reperfusion rate differed significantly before the beginning and at the end of the session (299 +/- 177%/min vs 375 +/- 182%/min, respectively; p < 0.05). Heart rate increased significantly at the end of the session (94 +/- 16 beats/min vs 99 +/- 16 beats/min, respectively; p < 0.05) as did systolic BP (127 +/- 21 mm Hg vs 133 +/- 23 mm Hg; p < 0.05, respectively). The Sto(2) value did not differ between the two measurements in control patients.

CONCLUSION

The data suggest that EMS has a systemic effect on microcirculation. These results suggest that further studies are needed to explore the potential use of EMS as a preventive and rehabilitation tool in critically ill patients.

A rational approach to nutritional assessment

BACKGROUND & AIMS

Consensus regarding definitions of malnutrition and methods to assess nutritional state is lacking. We propose a definition and its operationalization.

METHODS

A definition was formulated on the basis of the pathophysiology of malnutrition, while reviewing the metabolic and physiological characteristics of different populations, considered to be malnourished. The definition was operationalized to yield measures to perform nutritional assessment.

RESULTS

Malnutrition was defined as "a subacute or chronic state of nutrition in which a combination of varying degrees of over- or undernutrition and inflammatory activity has led to a change in body composition and diminished function". Its operationalization led to four elements that may serve as the basis of nutritional assessment: (1) measurement of nutrient balance, (2) measurement of body composition, (3) measurement of inflammatory activity, and (4) measurement of muscle, immune and cognitive function. Most elements measured should be validated with gold standards; normal values should be obtained in different populations. Values obtained in people considered to be at nutritional risk should be related to outcome.

CONCLUSION

A definition is proposed that reflects the pathophysiology of malnutrition and that, when operationalized, will lead to measures reflecting this pathophysiology. Such an approach may yield comparable and reproducible rates and degrees of malnutrition in populations as well as in individuals.