Nonexcitable muscle membrane predicts intensive care unit-acquired paresis in mechanically ventilated, sedated patients

Temporary and highly variable recovery of neuromuscular dysfunction by electrical stimulation in the follow-up of acute critical illness neuromyopathy: a pilot study

BACKGROUND

In sepsis-associated critical illness neuromyopathy (CIPNM) serial electrical stimulation of motor nerves induces a short-lived temporary recovery of compound muscle action potentials (CMAPs) termed facilitation phenomenon (FP). This technique is different from other stimulation techniques published. The identification of FP suggests a major functional component in acute CIPNM.

METHODS

From our previous study cohort of 18 intensive care unit patients with sepsis associated CIPNM showing profound muscle weakness and low or missing CMAPs on nerve conduction studies, six patients with different severity could be followed. In a pilot sub-study we analyzed the variability of FP during follow up. Over up to 6 weeks we performed 2-6 nerve conduction studies with our novel stimulation paradigm. Motor nerves were stimulated at 0.2-0.5 Hz with 60-100 mA at 0.2-0.5 ms duration, and CMAP responses were recorded. Standard motor nerve conduction velocities (NCV) could be done when utilizing facilitated CMAPs. Needle electromyography was checked once for spontaneous activity to discover potential denervation and muscle fiber degeneration. Serum electrolytes were checked before any examination and corrected if abnormal.

RESULTS

In all six patients a striking variability in the magnitude and pattern of FP could be observed at each examination in the same and in different motor nerves over time. With the first stimulus most CMAPs were below 0.1 mV or absent. With slow serial pulses CMAPs could gradually recover with normal shape and near normal amplitudes. With facilitated CMAPs NCV measurements revealed low normal values. With improvement of muscle weakness subsequent tests revealed larger first CMAP amplitudes and smaller magnitudes of FP. Needle EMG showed occasional spontaneous activity in the tibialis anterior muscle.

CONCLUSION

In this pilot study striking variability and magnitude of FP during follow-up was a reproducible feature indicating major fluctuations of neuromuscular excitability that may improve during follow-up. FP can be assessed by generally available electrophysiological techniques, even before patients could be tested for muscle strength. Large scale prospective studies of the facilitation phenomenon in CIPNM with or without sepsis are needed to define diagnostic specificity and to better understand the still enigmatic pathophysiology.

TRIAL REGISTRATION

This trial was registered at the Leipzig University Medical Center in 2021 after approval by the Ethics Committee.

Early shoulder-girdle MRI findings in severe COVID-19-related intensive care unit-acquired weakness: a prospective cohort study

OBJECTIVE

To describe clinical and early shoulder-girdle MR imaging findings in severe COVID-19-related intensive care unit-acquired weakness (ICU-AW) after ICU discharge.

METHODS

A single-center prospective cohort study of all consecutive patients with COVID-19-related ICU-AW from November 2020 to June 2021. All patients underwent similar clinical evaluations and shoulder-girdle MRI within the first month and then 3 months (± 1 month) after ICU discharge.

RESULTS

We included 25 patients (14 males; mean [SD] age 62.4 [12.5]). Within the first month after ICU discharge, all patients showed severe proximal predominant bilateral muscular weakness (mean Medical Research Council total score = 46.5/60 [10.1]) associated with bilateral, peripheral muscular edema-like MRI signals of the shoulder girdle in 23/25 (92%) patients. At 3 months, 21/25 (84%) patients showed complete or quasi-complete resolution of proximal muscular weakness (mean Medical Research Council total score > 48/60) and 23/25 (92%) complete resolution of MRI signals of the shoulder girdle, but 12/20 (60%) patients experienced shoulder pain and/or shoulder dysfunction.

CONCLUSIONS

Early shoulder-girdle MRI findings in COVID-19-related ICU-AW included muscular edema-like peripheral signal intensities, without fatty muscle involution or muscle necrosis, with favorable evolution at 3 months. Precocious MRI can help clinicians distinguish critical illness myopathy from alternative, more severe diagnoses and can be useful in the care of patients discharged from intensive care with ICU-AW.

KEY POINTS

• We describe the clinical and shoulder-girdle MRI findings of COVID-19-related severe intensive care unit-acquired weakness. • This information can be used by clinicians to achieve a nearly specific diagnosis, distinguish alternative diagnoses, assess functional prognosis, and select the more appropriate health care rehabilitation and shoulder impairment treatment.

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.

Development and validation of an intensive care unit acquired weakness prediction model: A cohort study

Background

At present, intensive care unit acquired weakness (ICU-AW) has become an important health care issue. The aim of this study was to develop and validate an ICU-AW prediction model for adult patients in intensive care unit (ICU) to provide a practical tool for early clinical diagnosis.

Methods

An observational cohort study was conducted including 400 adult patients admitted from September 2021 to June 2022 at an ICU with four ward at a medical university affiliated hospital in China. The Medical Research Council (MRC) scale was used to assess bedside muscle strength in ICU patients as a diagnostic basis for ICUAW. Patients were divided into the ICU-AW group and the no ICU-AW group and the clinical data of the two groups were statistically analyzed. A risk prediction model was then developed using binary logistic regression. Sensitivity, specificity, and the area under the curve (AUC) were used to evaluate the predictive ability of the model. The Hosmer-Lemeshow test was used to assess the model fit. The bootstrap method was used for internal verification of the model. In addition, the data of 120 patients in the validation group were selected for external validation of the model.

Results

The prediction model contained five risk factors: gender (OR: 4.31, 95% CI: 1.682-11.042), shock (OR: 3.473, 95% CI: 1.191-10.122), mechanical ventilation time (OR: 1.592, 95% CI: 1.317-1.925), length of ICU stay (OR: 1.085, 95% CI: 1.018-1.156) and age (OR: 1.075, 95% CI: 1.036-1.115). The AUC of this model was 0.904 (95% CI: 0.847-0.961), with sensitivity of 87.5%, specificity of 85.8%, and Youden index of 0.733. The AUC of the model after resampling is 0.889. The model verification results showed that the sensitivity, specificity and accuracy were 71.4, 92.9, and 92.9%, respectively.

Conclusion

An accurate, and readily implementable, risk prediction model for ICU-AW has been developed. This model uses readily obtained variables to predict patient ICU-AW risk. This model provides a tool for early clinical screening for ICU-AW.

A systematic review and meta-analysis of risk factors for intensive care unit acquired weakness

BACKGROUND

The aim of this meta-analysis is to systematically evaluate and summarize the risk factors of intensive care unit acquired weakness (ICU-AW), to provide evidence-based evidence for the formulation of prevention strategies for ICU-AW.

METHODS

PubMed, EMBASE, Web of Science, CBM (China Biology Medicine, China), Chinese National Knowledge Infrastructure, Chinese WANFANG, and VIP will be searched to define relevant risk factors for ICU-AW. The databases search period is from January 1, 2005 to August 13, 2021. The Newcastle Ottawa Scale (NOS) is used to evaluate the quality of the included studies. RevMan 5.3 analysis software will be used for meta-analysis.

RESULTS

This systematic review and meta-analysis included a total of 12 cohort studies, including 9 international journals and 3 Chinese journals, with a total of 1950 patients, of which 856 had ICU-AW. The results showed that the significant risk factors for ICU-AW included female (odds ratio [OR] = 1.34, 95% confidence interval [CI]: 1.06-1.71; P = .02), mechanical ventilation days (OR = 3.04, 95% CI: 1.82-4.26; P < .00001), age (OR = 6.33, 95% CI: 5.05-7.61; P < .00001), length of intensive care unit (ICU) stay (OR = 3.78, 95% CI: 2.06-5.51; P < .0001), infectious disease (OR = 1.67, 95% CI: 1.20-2.33; P = .002), renal replacement therapy (OR = 1.59, 95% CI: 1.11-2.28; P = .01), use of aminoglucoside drugs (OR = 2.51, 95% CI: 1.54-4.08; P = .0002), sepsis related organ failure assessment (SOFA) score (OR = 1.07, 95% CI: 0.24-1.90; P = .01), hyperglycemia (OR = 2.95, 95% CI: 1.70-5.11; P = .0001).

CONCLUSION

This meta-analysis provides comprehensive evidence-based on the assessment of the risk factors for ICU-AW, their multifactorial etiology was confirmed. This study indicated that female, mechanical ventilation days, age, length of ICU stay, infectious disease, renal replacement therapy, use of aminoglucoside drugs, SOFA score, and hyperglycemia are independent risk factors for ICU-AW. We have not found consistent evidence that corticosteroids, neuromuscular blockers, sepsis have any effect on ICU-AW risk.

Development and early diagnosis of critical illness myopathy in COVID-19 associated acute respiratory distress syndrome

BACKGROUND

The COVID-19 pandemic has greatly increased the incidence and clinical importance of critical illness myopathy (CIM), because it is one of the most common complications of modern intensive care medicine. Current diagnostic criteria only allow diagnosis of CIM at an advanced stage, so that patients are at risk of being overlooked, especially in early stages. To determine the frequency of CIM and to assess a recently proposed tool for early diagnosis, we have followed a cohort of COVID-19 patients with acute respiratory distress syndrome and compared the time course of muscle excitability measurements with the definite diagnosis of CIM.

METHODS

Adult COVID-19 patients admitted to the Intensive Care Unit of the University Hospital Bern, Switzerland requiring mechanical ventilation were recruited and examined on Days 1, 2, 5, and 10 post-intubation. Clinical examination, muscle excitability measurements, medication record, and laboratory analyses were performed on all study visits, and additionally nerve conduction studies, electromyography and muscle biopsy on Day 10. Muscle excitability data were compared with a cohort of 31 age-matched healthy subjects. Diagnosis of definite CIM was made according to the current guidelines and was based on patient history, results of clinical and electrophysiological examinations as well as muscle biopsy.

RESULTS

Complete data were available in 31 out of 44 recruited patients (mean [SD] age, 62.4 [9.8] years). Of these, 17 (55%) developed CIM. Muscle excitability measurements on Day 10 discriminated between patients who developed CIM and those who did not, with a diagnostic precision of 90% (AUC 0.908; 95% CI 0.799-1.000; sensitivity 1.000; specificity 0.714). On Days 1 and 2, muscle excitability parameters also discriminated between the two groups with 73% (AUC 0.734; 95% CI 0.550-0.919; sensitivity 0.562; specificity 0.857) and 82% (AUC 0.820; CI 0.652-0.903; sensitivity 0.750; specificity 0.923) diagnostic precision, respectively. All critically ill COVID-19 patients showed signs of muscle membrane depolarization compared with healthy subjects, but in patients who developed CIM muscle membrane depolarization on Days 1, 2 and 10 was more pronounced than in patients who did not develop CIM.

CONCLUSIONS

This study reports a 55% prevalence of definite CIM in critically ill COVID-19 patients. Furthermore, the results confirm that muscle excitability measurements may serve as an alternative method for CIM diagnosis and support its use as a tool for early diagnosis and monitoring the development of CIM.

Hidden Agenda - The Involvement of Endoplasmic Reticulum Stress and Unfolded Protein Response in Inflammation-Induced Muscle Wasting

Critically ill patients at the intensive care unit (ICU) often develop a generalized weakness, called ICU-acquired weakness (ICUAW). A major contributor to ICUAW is muscle atrophy, a loss of skeletal muscle mass and function. Skeletal muscle assures almost all of the vital functions of our body. It adapts rapidly in response to physiological as well as pathological stress, such as inactivity, immobilization, and inflammation. In response to a reduced workload or inflammation muscle atrophy develops. Recent work suggests that adaptive or maladaptive processes in the endoplasmic reticulum (ER), also known as sarcoplasmic reticulum, contributes to this process. In muscle cells, the ER is a highly specialized cellular organelle that assures calcium homeostasis and therefore muscle contraction. The ER also assures correct folding of proteins that are secreted or localized to the cell membrane. Protein folding is a highly error prone process and accumulation of misfolded or unfolded proteins can cause ER stress, which is counteracted by the activation of a signaling network known as the unfolded protein response (UPR). Three ER membrane residing molecules, protein kinase R-like endoplasmic reticulum kinase (PERK), inositol requiring protein 1a (IRE1a), and activating transcription factor 6 (ATF6) initiate the UPR. The UPR aims to restore ER homeostasis by reducing overall protein synthesis and increasing gene expression of various ER chaperone proteins. If ER stress persists or cannot be resolved cell death pathways are activated. Although, ER stress-induced UPR pathways are known to be important for regulation of skeletal muscle mass and function as well as for inflammation and immune response its function in ICUAW is still elusive. Given recent advances in the development of ER stress modifying molecules for neurodegenerative diseases and cancer, it is important to know whether or not therapeutic interventions in ER stress pathways have favorable effects and these compounds can be used to prevent or treat ICUAW. In this review, we focus on the role of ER stress-induced UPR in skeletal muscle during critical illness and in response to predisposing risk factors such as immobilization, starvation and inflammation as well as ICUAW treatment to foster research for this devastating clinical problem.

Critical Illness Myopathy: Diagnostic Approach and Resulting Therapeutic Implications

Purpose of review

Critical illness myopathy (CIM) is a common neuro-muscular complication of intensive care treatment associated with increased morbidity and mortality. The current guidelines for diagnosis include clinical and electrophysiological criteria as well as a muscle biopsy, and allow diagnosis only at an advanced stage of the disease. To date, there is no treatment for CIM available, apart from symptomatic and rehabilitative interventions. In this review, we discuss different diagnostic approaches and describe new treatment possibilities for CIM.

Recent findings

Of the diagnostic approaches evaluated, a new electrophysiological technique for measuring muscle excitability has the greatest potential to allow earlier diagnosis of CIM than the current guidelines do and thereby may facilitate the conduction of future pathophysiological and therapeutic studies. Although clinical trials are still lacking, in animal models, BGP-15, vamorolone, and ruxolitinib have been shown to have anti-inflammatory effects, to reduce muscle wasting and to improve muscle function and survival.

Summary

In recent years, promising methods for early and confirmatory diagnosis of CIM have been developed, but still need validation. Experimental studies on novel pharmacological interventions show promising results in terms of preventive CIM treatments, but future clinical studies will be needed to study the effectiveness and safety of these drugs.

Sex-Specific Aspects of Skeletal Muscle Metabolism in the Clinical Context of Intensive Care Unit-Acquired Weakness

(1) Background: Female sex is considered a risk factor for Intensive Care Unit-Acquired Weakness (ICUAW). The aim is to investigate sex-specific aspects of skeletal muscle metabolism in the context of ICUAW. (2) Methods: This is a sex-specific sub-analysis from two prospectively conducted trials examining skeletal muscle metabolism and advanced muscle activating measures in critical illness. Muscle strength was assessed by Medical Research Council Score. The insulin sensitivity index was analyzed by hyperinsulinemic-euglycemic (HE) clamp. Muscular metabolites were studied by microdialysis. M. vastus lateralis biopsies were taken. The molecular analysis included protein degradation pathways. Morphology was assessed by myocyte cross-sectional area (MCSA). Multivariable linear regression models for the effect of sex on outcome parameters were performed. (3) Results: n = 83 (♂n = 57, 68.7%; ♀n = 26, 31.3%) ICU patients were included. ICUAW was present in 81.1%♂ and in 82.4%♀ at first awakening (p = 0.911) and in 59.5%♂ and in 70.6%♀ at ICU discharge (p = 0.432). Insulin sensitivity index was reduced more in women than in men (p = 0.026). Sex was significantly associated with insulin sensitivity index and MCSA of Type IIa fibers in the adjusted regression models. (4) Conclusion: This hypothesis-generating analysis suggests that more pronounced impairments in insulin sensitivity and lower MCSA of Type IIa fibers in critically ill women may be relevant for sex differences in ICUAW.

Risk prediction models for intensive care unit-acquired weakness in intensive care unit patients: A systematic review

Background and objectives

Intensive care unit-acquired weakness (ICU-AW) commonly occurs among intensive care unit (ICU) patients and seriously affects the survival rate and long-term quality of life for patients. In this systematic review, we synthesized the findings of previous studies in order to analyze predictors of ICU-AW and evaluate the discrimination and validity of ICU-AW risk prediction models for ICU patients.

Methods

We searched seven databases published in English and Chinese language to identify studies regarding ICU-AW risk prediction models. Two reviewers independently screened the literature, evaluated the quality of the included literature, extracted data, and performed a systematic review.

Results

Ultimately, 11 studies were considered for this review. For the verification of prediction models, internal verification methods had been used in three studies, and a combination of internal and external verification had been used in one study. The value for the area under the ROC curve for eight models was 0.7–0.923. The predictor most commonly included in the models were age and the administration of corticosteroids. All the models have good applicability, but most of the models are biased due to the lack of blindness, lack of reporting, insufficient sample size, missing data, and lack of performance evaluation and calibration of the models.

Conclusions

The efficacy of most models for the risk prediction of ICU-AW among high-risk groups is good, but there was a certain bias in the development and verification of the models. Thus, ICU medical staff should select existing models based on actual clinical conditions and verify them before applying them in clinical practice. In order to provide a reliable basis for the risk prediction of ICU-AW, it is necessary that large-sample, multi-center studies be conducted in the future, in which ICU-AW risk prediction models are verified.

Critical illness myopathy precedes hyperglycaemia and high glucose variability

BACKGROUND

Critical Illness Myopathy (CIM) is a serious ICU complication, and dysglycaemia is widely regarded as a risk factor. Although glucose variability (GV) has been independently linked to ICU mortality, an association with CIM has not been investigated. This study examines the relationship between CIM and GV.

METHODS

Retrospective investigation including ICU patients with SOFA ≥8, mechanical ventilation, and CIM diagnostics. Glucose readings were collected every 6 h throughout the first week of treatment, when CIM is thought to develop. GV was measured using standard deviation (SD), coefficient of variability (CV), mean absolute glucose (MAG), mean amplitude of glycaemic excursions (MAGE), and mean of daily difference (MODD).

RESULTS

74 patients were included, and 50 (67.6%) developed CIM. Time on glycaemic target (70-179 mg/dL), caloric and insulin intakes, mean, maximum and minimum blood glucose values were similar for all patients until the 5th day, after which CIM patients exhibited higher mean and maximum glucose levels. Significantly higher GV in CIM patients were observed on day 5 (SD, CV, MAG, MAGE), day 6 (MODD), and day 7 (SD, CV, MAG).

CONCLUSIONS

CIM patients developed transient increases in GV and hyperglycaemia only late in the first week, suggesting that myopathy precedes dysglycaemia.

Muscle wasting in the critically ill patient: how to minimise subsequent disability

Muscle wasting in critically ill patients is the most common complication associated with critical care. It has significant effects on physical and psychological health, mortality and quality of life. It is most severe in the first few days of illness and in the most critically unwell patients, with muscle loss estimated to occur at 2-3% per day. This muscle loss is likely a result of a reduction in protein synthesis relative to muscle breakdown, resulting in altered protein homeostasis. The associated weakness is associated with in an increase in both short- and long-term mortality and morbidity, with these detrimental effects demonstrated up to 5 years post discharge. This article highlights the significant impact that muscle wasting has on critically ill patients' outcomes, how this can be reduced, and how this might change in the future.

Impact of Very Early Physical Therapy During Septic Shock on Skeletal Muscle: A Randomized Controlled Trial

Supplemental Digital Content is available in the text.

Objectives:

As the catabolic state induced by septic shock together with the physical inactivity of patients lead to the rapid loss of muscle mass and impaired function, the purpose of this study was to test whether an early physical therapy during the onset of septic shock regulates catabolic signals and preserves skeletal muscle mass.

Design:

Randomized controlled trial.

Setting:

Tertiary mixed ICU.

Patients:

Adult patients admitted for septic shock within the first 72 hours.

Interventions:

Patients were assigned randomly into two groups. The control group benefited from manual mobilization once a day. The intervention group had twice daily sessions of both manual mobilization and 30-minute passive/active cycling therapy.

Measurements and Main Results:

Skeletal muscle biopsies and electrophysiology testing were performed at day 1 and day 7. Muscle biopsies were analyzed for histology and molecular components of signaling pathways regulating protein synthesis and degradation as well as inflammation markers. Hemodynamic values and patient perception were collected during each session. Twenty-one patients were included. Three died before the second muscle biopsy. Ten patients in the control and eight in the intervention group were analyzed. Markers of the catabolic ubiquitin-proteasome pathway, muscle atrophy F-box and muscle ring finger-1 messenger RNA, were reduced at day 7 only in the intervention group, but without difference between groups (muscle atrophy F-box: –7.3% ± 138.4% in control vs –56.4% ± 37.4% in intervention group; p = 0.23 and muscle ring finger-1: –30.8% ± 66.9% in control vs –62.7% ± 45.5% in intervention group; p = 0.15). Muscle fiber cross-sectional area (µm²) was preserved by exercise (–25.8% ± 21.6% in control vs 12.4% ± 22.5% in intervention group; p = 0.005). Molecular regulations suggest that the excessive activation of autophagy due to septic shock was lower in the intervention group, without being suppressed. Markers of anabolism and inflammation were not modified by the intervention, which was well tolerated by the patients.

Conclusions:

Early physical therapy during the first week of septic shock is safe and preserves muscle fiber cross-sectional area.

Differential contractile response of critically ill patients to neuromuscular electrical stimulation

Background

Neuromuscular electrical stimulation (NMES) has been investigated as a preventative measure for intensive care unit-acquired weakness. Trial results remain contradictory and therefore inconclusive. As it has been shown that NMES does not necessarily lead to a contractile response, our aim was to characterise the response of critically ill patients to NMES and investigate potential outcome benefits of an adequate contractile response.

Methods

This is a sub-analysis of a randomised controlled trial investigating early muscle activating measures together with protocol-based physiotherapy in patients with a SOFA score ≥ 9 within the first 72 h after admission. Included patients received protocol-based physiotherapy twice daily for 20 min and NMES once daily for 20 min, bilaterally on eight muscle groups. Electrical current was increased up to 70 mA or until a contraction was detected visually or on palpation. Muscle strength was measured by a blinded assessor at the first adequate awakening and ICU discharge.

Results

One thousand eight hundred twenty-four neuromuscular electrical stimulations in 21 patients starting on day 3.0 (2.0/6.0) after ICU admission were included in this sub-analysis. Contractile response decreased from 64.4% on day 1 to 25.0% on day 7 with a significantly lower response rate in the lower extremities and proximal muscle groups. The electrical current required to elicit a contraction did not change over time (day 1, 50.2 [31.3/58.8] mA; day 7, 45.3 [38.0/57.5] mA). The electrical current necessary for a contractile response was higher in the lower extremities. At the first awakening, patients presented with significant weakness (3.2 [2.5/3.8] MRC score). When dividing the cohort into responders and non-responders (> 50% vs. ≤ 50% contractile response), we observed a significantly higher SOFA score in non-responders. The electrical current necessary for a muscle contraction in responders was significantly lower (38.0 [32.8/42.9] vs. 54.7 [51.3/56.0] mA, p < 0.001). Muscle strength showed higher values in the upper extremities of responders at ICU discharge (4.4 [4.1/4.6] vs. 3.3 [2.8/3.8] MRC score, p = 0.036).

Conclusion

Patients show a differential contractile response to NMES, which appears to be dependent on the severity of illness and also relevant for potential outcome benefits.

Trial registration

ISRCTN ISRCTN19392591, registered 17 February 2011

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2540-4) contains supplementary material, which is available to authorized users.

From skeletal muscle weakness to functional outcomes following critical illness: a translational biology perspective

Intensive care unit acquired weakness (ICUAW) is now a well-known entity complicating critical illness. It increases mortality and in the critical illness survivor it is associated with physical disability, substantially increased health resource utilisation and healthcare costs. Skeletal muscle wasting is a key driver of ICUAW and physical functional outcomes in both the short and long term. To date, there is no intervention that can universally and consistently prevent muscle loss during critical illness, or enhance its recovery following intensive care unit discharge, to improve physical function. Clinical trials of early mobilisation or exercise training, or enhanced nutritional support have generated inconsistent results and we have no effective pharmacological interventions. This review will delineate our current understanding of the mechanisms underpinning the development and persistence of skeletal muscle loss and dysfunction in the critically ill individual, highlighting recent discoveries and clinical observations, and utilisation of this knowledge in the development of novel therapeutics.

Muscular Ultrasound, Syndecan-1 and Procalcitonin Serum Levels to Assess Intensive Care Unit-Acquired Weakness

BACKGROUND

Intensive care unit-acquired weakness (ICU-AW) is associated with poorer outcome of critically ill patients. Microcirculatory changes and altered vascular permeability of skeletal muscles might contribute to the pathogenesis of ICU-AW. Muscular ultrasound (MUS) displays increased muscle echogenicity, although its pathogenesis is uncertain.

OBJECTIVE

We investigated the combined measurement of serum and ultrasound markers to assess ICU-AW and clinical patient outcome.

METHODS

Fifteen patients and five healthy controls were longitudinally assessed for signs of ICU-AW at study days 3 and 10 using a muscle strength sum score. The definition of ICU-AW was based on decreased muscle strength assessed by the muscular research council-sum score. Ultrasound echogenicity of extremity muscles was assessed using a standardized protocol. Serum markers of inflammation and endothelial damage were measured. The 3-month outcome was assessed on the modified Rankin scale.

RESULTS

ICU-AW was present in eight patients, and seven patients and the control subjects did not develop ICU-AW. The global muscle echogenicity score (GME) differed significantly between controls and patients (mean GME, 1.1 ± 0.06 vs. 2.3 ± 0.41; p = 0.001). Mean GME values significantly decreased in patients without ICU-AW from assessment 1 (2.30 ± 0.48) to assessment 2 (2.06 ± 0.45; p = 0.027), which was not observed in patients with ICU-AW. Serum levels of syndecan-1 at day 3 significantly correlated with higher GME values at day 10 (r = 0.63, p = 0.012). Furthermore, the patients' GME significantly correlated with mRS at day 100 (r = 0.67, p = 0.013).

CONCLUSION

The combined use of muscular ultrasound and inflammatory biomarkers might be helpful to diagnose ICU-AW and to predict long-term outcome in critical illness.

Corticosteroid use and intensive care unit-acquired weakness: a systematic review and meta-analysis

Background

The association between corticosteroid use and intensive care unit (ICU)-acquired weakness remains unclear. We evaluated the relationship between corticosteroid use and ICU-acquired weakness in critically ill adult patients.

Methods

The PubMed, Embase, Web of Science, Cochrane Central Register of Controlled Trials, and Cumulative Index of Nursing and Allied Health Literature databases were searched from database inception until October 10, 2017. Two authors independently screened the titles/abstracts and reviewed full-text articles. Randomized controlled trials and prospective cohort studies evaluating the association between corticosteroids and ICU-acquired weakness in adult ICU patients were selected. Data extraction from the included studies was accomplished by two independent reviewers. Meta-analysis was performed using Stata version 12.0. The results were analyzed using odds ratios (ORs) and 95% confidence intervals (CIs). Data were pooled using a random effects model, and heterogeneity was evaluated using the χ² and I² statistics. Publication bias was qualitatively analyzed with funnel plots, and quantitatively analyzed with Begg’s test and Egger’s test.

Results

One randomized controlled trial and 17 prospective cohort studies were included in this review. After a meta-analysis, the effect sizes of the included studies indicated a statistically significant association between corticosteroid use and ICU-acquired weakness (OR 1.84; 95% CI 1.26–2.67; I² = 67.2%). Subgroup analyses suggested a significant association between corticosteroid use and studies limited to patients with clinical weakness (OR 2.06; 95% CI 1.27–3.33; I² = 60.6%), patients with mechanical ventilation (OR 2.00; 95% CI 1.23–3.27; I² = 66.0%), and a large sample size (OR 1.61; 95% CI 1.02–2.53; I² = 74.9%), and not studies limited to patients with abnormal electrophysiology (OR 1.65; 95% CI 0.92–2.95; I² = 70.6%) or patients with sepsis (OR 1.96; 95% CI 0.61–6.30; I² = 80.8%); however, statistical heterogeneity was obvious. No significant publication biases were found in the review. The overall quality of the evidence was high for the randomized controlled trial and very low for the included prospective cohort studies.

Conclusions

The review suggested a significant association between corticosteroid use and ICU-acquired weakness. Thus, exposure to corticosteroids should be limited, or the administration time should be shortened in clinical practice to reduce the risk of ICU-acquired weakness.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2111-0) contains supplementary material, which is available to authorized users.

Intensive Care Unit-Acquired Weakness

Intensive care unit-acquired weakness (ICUAW) is a substantial contributor to long-term disability in survivors of critical illness. Critical illness polyneuropathy, critical illness myopathy, and muscle atrophy from disuse contribute in various proportions to ICUAW. ICUAW is a clinical diagnosis supported by electrophysiology and newer diagnostic tests, such as muscle ultrasound. Risk factor reduction, including the aggressive treatment of sepsis and early mobilization, improves outcome. Although some patients with ICUAW experience a full recovery, for others improvement is slow and incomplete and quality of life is adversely affected. This article examines aspects of ICUAW and identifies potential areas of further study.

Tetraparetic critically ill patients show electrophysiological signs of myopathy

INTRODUCTION

Critically ill patients often develop tetraparesis. It has been debated whether this is caused by neuropathy, myopathy, or both. The aim was to determine the incidence of myopathy and neuropathy in weak patients in the intensive care unit by performing several electrophysiological examinations, including quantitative electromyography (qEMG).

METHODS

Forty-nine patients referred for electrophysiological examination because of suspected critical illness-related weakness underwent qEMG, nerve conduction studies, and direct muscle stimulation.

RESULTS

The qEMG showed signs of myopathy in 33 of 35 patients. Direct muscle stimulation was consistent with myopathy in 31 of 34 patients. Amplitudes of compound muscle action potentials were decreased in all patients. Four patients also had signs of sensory neuropathy, which could not be explained by preexisting medical conditions.

CONCLUSIONS

When combined, the results are compatible with muscle dysfunction in all patients. This will help to direct future studies of the pathophysiology of this serious condition. Muscle Nerve 56: 433-440, 2017.

Intensive care unit-acquired weakness

When critically ill, a severe weakness of the limbs and respiratory muscles often develops with a prolonged stay in the intensive care unit (ICU), a condition vaguely termed intensive care unit-acquired weakness (ICUAW). Many of these patients have serious nerve and muscle injury. This syndrome is most often seen in surviving critically ill patients with sepsis or extensive inflammatory response which results in increased duration of mechanical ventilation and hospital length of stay. Patients with ICUAW often do not fully recover and the disability will seriously impact on their quality of life. In this chapter we discuss the current knowledge on the pathophysiology and risk factors of ICUAW. Tools to diagnose ICUAW, how to separate ICUAW from other disorders, and which possible treatment strategies can be employed are also described. ICUAW is finally receiving the attention it deserves and the expectation is that it can be better understood and prevented.

Critical illness polyneuropathy in ICU patients is related to reduced motor nerve excitability caused by reduced sodium permeability

Background

Reduced motor and sensory nerve amplitudes in critical illness polyneuropathy (CIP) are characteristic features described in electrophysiological studies and due to dysfunction of voltage-gated sodium channels. Yet, faulty membrane depolarization as reported in various tissues of critically ill patients may cause reduced membrane excitability as well. The aim of this study was to compare the pathophysiological differences in motor nerve membrane polarization and voltage-gated sodium channel function between CIP patients and critically ill patients not developing CIP during their ICU stay (ICU controls).

Methods

ICU patients underwent electrophysiological nerve conduction studies and were categorized as either ICU controls or CIP patients. Subsequently, excitability parameters were recorded as current-threshold relationship, stimulus-response behavior, threshold electrotonus, and recovery of excitability from the abductor pollicis brevis following median nerve stimulation.

Results

Twenty-six critically ill patients were enrolled and categorized as 12 ICU controls and 14 CIP patients. When compared to 31 healthy subjects, the ICU controls exhibited signs of membrane depolarization as shown by reduced superexcitability (p = 0.003), depolarized threshold electrotonus (p = 0.007), increased current-threshold relationship (p = 0.03), and slightly prolonged strength-duration time constant. In contrast, the CIP patients displayed a significantly reduced strength-duration time constant (p < 0.0001), which indicates an increased inactivation of voltage-gated sodium channels.

Conclusions

Abnormal motor nerve membrane depolarization is a general finding in critically ill patients whereas voltage-gated sodium channel dysfunction is a characteristic of CIP patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-016-0083-4) contains supplementary material, which is available to authorized users.

Feasibility and diagnostic accuracy of early electrophysiological recordings for ICU-acquired weakness: an observational cohort study

BACKGROUND

An early diagnosis of ICU-acquired weakness (ICU-AW) is difficult because disorders of consciousness frequently preclude muscle strength assessment. In this study, we investigated feasibility and accuracy of electrophysiological recordings to diagnose ICU-AW early in non-awake critically ill patients.

METHODS

Newly admitted patients, mechanically ventilated ≥2 days and unreactive to verbal stimuli, were included in this study. Electrophysiological recordings comprised nerve conduction studies (NCS) of three nerves and, if coagulation was normal, myography in three muscles. Upon awakening, strength was assessed (ICU-AW: average Medical Research Council score <4), blinded for electrophysiological recordings. Feasibility was expressed as the percentage of recordings that were both possible and had sufficient technical quality. Diagnostic accuracy of feasible (i.e., feasibility >75 %) recordings was analyzed based on cut-off values from healthy controls and from critically ill patients with and without ICU-AW.

RESULTS

Thirty-five patients were included (17 with ICU-AW). Recordings were obtained on day 4 (IQR: 3-6). Feasibility was acceptable for ulnar and peroneal nerve recordings, and low for sural recordings and myography. Diagnostic accuracy based on cut-off values from healthy controls was low. When using cut-off values from critically ill patients with and without ICU-AW, the peroneal compound muscle action potential amplitude and ulnar sensory nerve action potential amplitude had good diagnostic accuracy.

CONCLUSION

Nerve conduction studies of the ulnar and peroneal nerve are feasible in critically ill patients. The diagnostic accuracy is low using cut-off values from healthy controls. Cut-off values validated specifically for discrimination between critically ill patients with and without ICU-AW may improve diagnostic accuracy.

Qualitative Ultrasound in Acute Critical Illness Muscle Wasting

OBJECTIVES

A rapid and early loss of skeletal muscle mass underlies the physical disability common amongst survivors of critical illness. However, skeletal muscle function depends not only on its quantity but its quality, which may be adversely affected. We set out to characterise the changes in macroscopic muscle echogenicity and fascial characteristics that occur early in critical illness, and to relate these to microscopic histologically defined myofibre necrosis and fascial pathology.

DESIGN AND SETTING

Prospective two center observational study.

PATIENTS

Thirty subjects comprising a subgroup of patients recruited to the Musculoskeletal Ultrasound in Critical Illness: Longitudinal Evaluation (MUSCLE) study.

MEASUREMENTS AND MAIN RESULTS

Comparisons were made between sequential Vastus Lateralis histological specimens and ultrasound assessment of Rectus Femoris echogenicity. Change in muscle echogenicity was greater in patients who developed muscle necrosis (n = 15) than in those who did not (8.2% [95% CI, -5.3 to 21.7] vs -15.0% [95% CI, -28.9 to -1.09]; p = 0.016). The area under receiver operator curve for ultrasound echogenicity's prediction of myofiber necrosis was 0.74 (95% CI, 0.565 to 0.919; p = 0.024) increasing to 0.85 (95% CI, 0.703 to -0.995; p = 0.003) with the removal of those with potential iatrogenic muscle damage. Fasciitis was observed in 18 of 30 biopsies (60%).

CONCLUSIONS

Myofiber necrosis and fascial inflammation can be detected noninvasively using ultrasound in the critically ill. Fasciitis precedes and frequently accompanies muscle necrosis. These findings may have functional implications for survivors of critical illness.

Predictive value for weakness and 1-year mortality of screening electrophysiology tests in the ICU

PURPOSE

Muscle weakness in long-stay ICU patients contributes to 1-year mortality. Whether electrophysiological screening is an alternative diagnostic tool in unconscious/uncooperative patients remains unknown. We aimed to determine the diagnostic properties of abnormal compound muscle action potential (CMAP), sensory nerve action potential (SNAP), and spontaneous electrical activity (SEA) for Medical Research Council (MRC)-defined weakness and their predictive value for 1-year mortality.

METHODS

Data were prospectively collected during the EPaNIC trial (ClinicalTrials.gov: NCT00512122). First, sensitivity, specificity, positive (PPV) and negative predictive values (NPV) of abnormal CMAP, SNAP, and SEA for weakness were determined. Subsequently, association between 1-year mortality and abnormal findings on electrophysiological screening was assessed by univariate and multivariate analyses correcting for weakness and other risk factors and the prediction model involved only a development phase.

RESULTS

A total of 730 patients were electrophysiologically screened of whom 432 were tested for weakness. On day 8, normal CMAP excluded weakness with a high NPV (80.5 %). By day 15, abnormal SNAP and the presence of SEA had a high PPV (91.7 and 80.0 %, respectively). Only a reduced CMAP on day 8 was associated with higher 1-year mortality [35.6 vs 15.2 % (p < 0.001)]. This association remained significant after correction for weakness and other risk factors [OR 2.463 (95 % CI 1.113-5.452), p = 0.026]. Also among conscious/cooperative patients without weakness, reduced CMAP was independently associated with a higher likelihood of death occurring during 1 year [HR 2.818 (95 % CI 1.074-7.391), p = 0.035].

CONCLUSIONS

The diagnostic properties of electrophysiological screening vary over time. Abnormal CMAP documented early during critical illness carries information about longer-term outcome, which should be further investigated mechanistically.

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.

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.

The incidence of intensive care unit-acquired weakness syndromes: A systematic review

We conducted a literature review of the intensive care unit-acquired weakness syndromes (critical illness polyneuropathy, critical illness myopathy and critical illness neuromyopathy) with the primary objective of determining their incidence as a combined group. Studies were identified through MEDLINE, Embase, Cochrane Database and article reference list searches and were included if they evaluated the incidence of one or more of these conditions in an adult intensive care unit population. The incidence of an intensive care unit-acquired weakness syndrome in the included studies was 40% (1080/2686 patients, 95% confidence interval 38-42%). The intensive care unit populations included were heterogeneous though largely included patients receiving mechanical ventilation for seven or more days. Additional prespecified outcomes identified that the incidence of intensive care unit-acquired weakness varied with the diagnostic technique used, being lower with clinical (413/1276, 32%, 95% CI 30-35%) compared to electrophysiological techniques (749/1591, 47%, 95% CI 45-50%). Approximately a quarter of patients were not able to comply with clinical evaluation and this may be responsible for potential underreporting of this condition.

Early prediction of intensive care unit-acquired weakness using easily available parameters: a prospective observational study

INTRODUCTION

An early diagnosis of Intensive Care Unit-acquired weakness (ICU-AW) using muscle strength assessment is not possible in most critically ill patients. We hypothesized that development of ICU-AW can be predicted reliably two days after ICU admission, using patient characteristics, early available clinical parameters, laboratory results and use of medication as parameters.

METHODS

Newly admitted ICU patients mechanically ventilated ≥2 days were included in this prospective observational cohort study. Manual muscle strength was measured according to the Medical Research Council (MRC) scale, when patients were awake and attentive. ICU-AW was defined as an average MRC score <4. A prediction model was developed by selecting predictors from an a-priori defined set of candidate predictors, based on known risk factors. Discriminative performance of the prediction model was evaluated, validated internally and compared to the APACHE IV and SOFA score.

RESULTS

Of 212 included patients, 103 developed ICU-AW. Highest lactate levels, treatment with any aminoglycoside in the first two days after admission and age were selected as predictors. The area under the receiver operating characteristic curve of the prediction model was 0.71 after internal validation. The new prediction model improved discrimination compared to the APACHE IV and the SOFA score.

CONCLUSION

The new early prediction model for ICU-AW using a set of 3 easily available parameters has fair discriminative performance. This model needs external validation.

Long-term recovery In critical illness myopathy is complete, contrary to polyneuropathy

INTRODUCTION

Muscle weakness in critically ill patients after discharge varies. It is not known whether the electrophysiological distinction between critical illness myopathy (CIM) and critical illness polyneuropathy (CIP) during the early part of a patient's stay in the intensive care unit (ICU) predicts long-term prognosis.

METHODS

This was a prospective cohort study of mechanically ventilated ICU patients undergoing conventional nerve conduction studies and direct muscle stimulation in addition to neurological examination during their ICU stay and 1 year after ICU discharge.

RESULTS

Twenty-six patients (7 ICU controls, 8 CIM patients, and 11 CIM/CIP patients) were evaluated 1 year after discharge from the ICU. Eighty-eight percent (n = 7) of CIM patients recovered within 1 year compared with 55% (n = 6) of CIM/CIP patients. Thirty-six percent (n = 4) of CIM/CIP patients still needed assistance during their daily routine (P = 0.005).

CONCLUSIONS

Early electrophysiological testing predicts long-term outcome in ICU survivors. CIM has a significantly better prognosis than CIM/CIP.

Feasibility of neuromuscular electrical stimulation in critically ill patients

OBJECTIVE

Critically ill patients often develop intensive care unit-acquired weakness. Reduction in muscle mass and muscle strength occurs early after admission to the intensive care unit (ICU). Although early active muscle training could attenuate this intensive care unit-acquired weakness, in the early phase of critical illness, a large proportion of patients are unable to participate in any active mobilization. Neuromuscular electrical stimulation (NMES) could be an alternative strategy for muscle training. The aim of this study was to investigate the safety and feasibility of NMES in critically ill patients.

DESIGN

This is an observational study.

SETTING

The setting is in the medical and surgical ICUs of a tertiary referral university hospital.

PATIENTS

Fifty patients with a prognosticated prolonged stay of at least 6 days were included on day 3 to 5 of their ICU stay. Patients with preexisting neuromuscular disorders and patients with musculoskeletal conditions limiting quadriceps contraction were excluded.

INTERVENTION

Twenty-five minutes of simultaneous bilateral NMES of the quadriceps femoris muscle. This intervention was performed 5 days per week (Monday-Friday). Effective muscle stimulation was defined as a palpable and visible contraction (partial or full muscle bulk).

MEASUREMENTS

The following parameters, potentially affecting contraction upon NMES, were assessed: functional status before admission to the ICU (Barthel index), type and severity of illness (Acute Physiology And Chronic Health Evaluation II score and sepsis), treatments possibly influencing the muscle contraction (corticosteroids, vasopressors, inotropes, aminoglycosides, and neuromuscular blocking agents), level of consciousness (Glasgow Coma Scale, score on 5 standardized questions evaluating awakening, and sedation agitation scale), characteristics of stimulation (intensity of the NMES, number of sessions per patient, and edema), and neuromuscular electrophysiologic characteristics. Changes in heart rate, blood pressure, oxygen saturation, respiratory rate, and skin reactions were registered to assess the safety of the technique.

RESULTS

In 50% of the patients, an adequate quadriceps contraction was obtained in at least 75% of the NMES sessions. Univariate analysis showed that lower limb edema (P<.001), sepsis (P=.008), admission to the medical ICU (P=.041), and treatment with vasopressors (P=.011) were associated with impaired quadriceps contraction. A backward multivariate analysis identified presence of sepsis, lower limb edema, and use of vasopressors as independent predictors of impaired quadriceps contraction (R2=59.5%). Patients responded better to NMES in the beginning of their ICU stay in comparison with after 1 week of ICU stay. There was no change in any of the safety end points with NMES.

CONCLUSIONS

Critically ill patients having sepsis, edema, or receiving vasopressors were less likely to respond to NMES with an adequate quadriceps contraction. Neuromuscular electrical stimulation is a safe intervention to be administered in the ICU.

Validation of the peroneal nerve test to diagnose critical illness polyneuropathy and myopathy in the intensive care unit: the multicentre Italian CRIMYNE-2 diagnostic accuracy study

OBJECTIVES

To evaluate the accuracy of the peroneal nerve test (PENT) in the diagnosis of critical illness polyneuropathy (CIP) and myopathy (CIM) in the intensive care unit (ICU). We hypothesised that abnormal reduction of peroneal compound muscle action potential (CMAP) amplitude predicts CIP/CIM diagnosed using a complete nerve conduction study and electromyography (NCS-EMG) as a reference diagnostic standard.

DESIGN

prospective observational study.

SETTING

Nine Italian ICUs.

PATIENTS

One-hundred and twenty-one adult (≥18 years) neurologic (106) and non-neurologic (15) critically ill patients with an ICU stay of at least 3 days.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

PATIENTS underwent PENT and NCS-EMG testing on the same day conducted by two independent clinicians who were blind to the results of the other test. Cases were considered as true negative if both NCS-EMG and PENT measurements were normal. Cases were considered as true positive if the PENT result was abnormal and NCS-EMG showed symmetric abnormal findings, independently from the specific diagnosis by NCS-EMG (CIP, CIM, or combined CIP and CIM). All data were centrally reviewed and diagnoses were evaluated for consistency with predefined electrophysiological diagnostic criteria for CIP/CIM. During the study period, 342 patients were evaluated, 124 (36.3%) were enrolled and 121 individuals with no protocol violation were studied. Sensitivity and specificity of PENT were 100% (95% CI 96.1-100.0) and 85.2% (95% CI 66.3-95.8). Of 23 patients with normal results, all presented normal values on both tests with no false negative results. Of 97 patients with abnormal results, 93 had abnormal values on both tests (true positive), whereas four with abnormal findings with PENT had only single peroneal nerve neuropathy at complete NCS-EMG (false positive).

CONCLUSIONS

PENT has 100% sensitivity and high specificity, and can be used to diagnose CIP/CIM in the ICU.

Validation of the peroneal nerve test to diagnose critical illness polyneuropathy and myopathy in the intensive care unit: the multicentre Italian CRIMYNE-2 diagnostic accuracy study

OBJECTIVES

To evaluate the accuracy of the peroneal nerve test (PENT) in the diagnosis of critical illness polyneuropathy (CIP) and myopathy (CIM) in the intensive care unit (ICU). We hypothesised that abnormal reduction of peroneal compound muscle action potential (CMAP) amplitude predicts CIP/CIM diagnosed using a complete nerve conduction study and electromyography (NCS-EMG) as a reference diagnostic standard.

DESIGN

prospective observational study.

SETTING

Nine Italian ICUs.

PATIENTS

One-hundred and twenty-one adult (≥18 years) neurologic (106) and non-neurologic (15) critically ill patients with an ICU stay of at least 3 days.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

PATIENTS underwent PENT and NCS-EMG testing on the same day conducted by two independent clinicians who were blind to the results of the other test. Cases were considered as true negative if both NCS-EMG and PENT measurements were normal. Cases were considered as true positive if the PENT result was abnormal and NCS-EMG showed symmetric abnormal findings, independently from the specific diagnosis by NCS-EMG (CIP, CIM, or combined CIP and CIM). All data were centrally reviewed and diagnoses were evaluated for consistency with predefined electrophysiological diagnostic criteria for CIP/CIM. During the study period, 342 patients were evaluated, 124 (36.3%) were enrolled and 121 individuals with no protocol violation were studied. Sensitivity and specificity of PENT were 100% (95% CI 96.1-100.0) and 85.2% (95% CI 66.3-95.8). Of 23 patients with normal results, all presented normal values on both tests with no false negative results. Of 97 patients with abnormal results, 93 had abnormal values on both tests (true positive), whereas four with abnormal findings with PENT had only single peroneal nerve neuropathy at complete NCS-EMG (false positive).

CONCLUSIONS

PENT has 100% sensitivity and high specificity, and can be used as a screening test to diagnose CIP/CIM in the ICU.

Electrical Muscle Stimulation in the Intensive Care Unit: An Integrative Review

Following a period of critical illness, physical function and health-related quality of life are slow to recover, both in the short and long term. Muscle wasting and weakness during the intensive care unit (ICU) admission is a recognised contributory factor. Enhanced rehabilitation programmes are advocated to improve outcomes, and electrical muscle stimulation (EMS) has been recommended during the early critical illness trajectory. This technique is fairly new to the ICU, and limited efficacy data exists for its use in this setting. This integrative review will examine published and on-going ICU studies with the purpose of reporting on the characteristics of EMS study participants; content of EMS treatment protocols; safety of EMS in the ICU setting; effects on EMS on muscle wasting; effects of EMS on muscle strength; and future research.

Functional electrical stimulation with cycling in the critically ill: a pilot case-matched control study

PURPOSE

The purpose was to determine (a) safety and feasibility of functional electrical stimulation (FES)-cycling and (b) compare FES-cycling to case-matched controls in terms of functional recovery and delirium outcomes.

MATERIALS AND METHODS

Sixteen adult intensive care unit patients with sepsis ventilated for more than 48 hours and in the intensive care unit for at least 4 days were included. Eight subjects underwent FES-cycling in addition to usual care and were compared to 8 case-matched control individuals. Primary outcomes were safety and feasibility of FES-cycling. Secondary outcomes were Physical Function in Intensive Care Test scored on awakening, time to reach functional milestones, and incidence and duration of delirium.

RESULTS

One minor adverse event was recorded. Sixty-nine out of total possible 95 FES sessions (73%) were completed. A visible or palpable contraction was present 80% of the time. There was an improvement in Physical Function in Intensive Care Test score of 3.9/10 points in the intervention cohort with faster recovery of functional milestones. There was also a shorter duration of delirium in the intervention cohort.

CONCLUSIONS

The delivery of FES-cycling is both safe and feasible. The preliminary findings suggest that FES-cycling may improve function and reduce delirium. Further research is required to confirm the findings of this study and evaluate the efficacy of FES-cycling.

Inflammation-induced acute phase response in skeletal muscle and critical illness myopathy

Objectives

Systemic inflammation is a major risk factor for critical-illness myopathy (CIM) but its pathogenic role in muscle is uncertain. We observed that interleukin 6 (IL-6) and serum amyloid A1 (SAA1) expression was upregulated in muscle of critically ill patients. To test the relevance of these responses we assessed inflammation and acute-phase response at early and late time points in muscle of patients at risk for CIM.

Design

Prospective observational clinical study and prospective animal trial.

Setting

Two intensive care units (ICU) and research laboratory.

Patients/Subjects

33 patients with Sequential Organ Failure Assessment scores ≥8 on 3 consecutive days within 5 days in ICU were investigated. A subgroup analysis of 12 patients with, and 18 patients without CIM (non-CIM) was performed. Two consecutive biopsies from vastus lateralis were obtained at median days 5 and 15, early and late time points. Controls were 5 healthy subjects undergoing elective orthopedic surgery. A septic mouse model and cultured myoblasts were used for mechanistic analyses.

Measurements and Main Results

Early SAA1 expression was significantly higher in skeletal muscle of CIM compared to non-CIM patients. Immunohistochemistry showed SAA1 accumulations in muscle of CIM patients at the early time point, which resolved later. SAA1 expression was induced by IL-6 and tumor necrosis factor-alpha in human and mouse myocytes in vitro. Inflammation-induced muscular SAA1 accumulation was reproduced in a sepsis mouse model.

Conclusions

Skeletal muscle contributes to general inflammation and acute-phase response in CIM patients. Muscular SAA1 could be important for CIM pathogenesis.

Trial Registration

ISRCTN77569430.

Screening for critical illness polyneuromyopathy with single nerve conduction studies

PURPOSE

The ability to diagnose patients with critical illness polyneuromyopathy (CIPNM) is hampered by impaired patient sensorium, technical limitations, and the time-intensive nature of performing electrophysiological testing. Therefore, we sought to determine whether single nerve conduction studies (NCS) could accurately screen for CIPNM.

METHODS

Critically ill patients at increased risk for developing CIPNM were identified. Bilateral NCS of six nerves, and concentric needle electromyography were performed within 24 h of meeting inclusion criteria, and subsequently on a weekly basis until CIPNM was diagnosed or the patient was discharged from the intensive care unit (ICU).

RESULTS

A total of 75 patients were enrolled into the study. Patients who developed CIPNM had a higher hospital mortality (50 vs. 13%, p = 0.002), and fewer ICU-free days (0 vs. 11, p = 0.04). There were no differences between the right and left amplitudes (p = 0.59, 0.91, and 0.21) for nerves that could be simultaneously tested bilaterally (sural, peroneal, and tibial). The amplitudes for each of the six individual nerves were significantly diminished in patients with CIPNM when compared to patients without CIPNM. The nerves with the best diagnostic accuracy were the peroneal nerve [AUC = 0.8856; sensitivity = 94% (95% CI = 88-100%); specificity = 74% (95% CI = 63-85%)], and the sural nerve [AUC = 0.8611; sensitivity = 94% (95 % CI = 88-100%); specificity = 70% (95 % CI = 59-81%)]. The combined diagnostic accuracy for the amplitudes of the peroneal and sural nerves increased significantly [AUC = 0.9336; sensitivity = 100% (95% CI = 100-100%) and specificity = 81% (95% CI = 71-91%)].

CONCLUSIONS

Unilateral peroneal and sural NCS can accurately screen for CIPNM in ICU patients and detect a limited number of patients that would need concentric needle electromyography to confirm a diagnosis of CIPNM. These results identify a more streamlined method to diagnose CIPNM that may facilitate routine diagnostic testing and monitoring of weakness in critically ill patients.

Dynamics of myosin degradation in intensive care unit-acquired weakness during severe critical illness

IMPORTANCE

Intensive care unit (ICU)-acquired muscle wasting is a devastating complication leading to persistent weakness and functional disability. The mechanisms of this myopathy are unclear, but a disturbed balance of myosin heavy chain (MyHC) is implicated.

OBJECTIVE

To investigate pathways of myosin turnover in severe critically ill patients at high risk of ICU-acquired weakness.

DESIGN

Prospective, mechanistic, observational study.

SETTING

Interdisciplinary ICUs of a university hospital.

PARTICIPANTS

Twenty-nine patients with Sequential Organ Failure Assessment (SOFA) scores of at least 8 on three consecutive days within the first 5 days in ICU underwent two consecutive open skeletal muscle biopsies from the vastus lateralis at median days 5 and 15. Control biopsy specimens were from healthy subjects undergoing hip-replacement surgery.

INTERVENTIONS

None.

MAIN OUTCOME(S) AND MEASURE(S)

Time-dependent changes in myofiber architecture, MyHC synthesis, and degradation were determined and correlated with clinical data.

RESULTS

ICU-acquired muscle wasting was characterized by early, disrupted myofiber ultrastructure followed by atrophy of slow- and fast-twitch myofibers at later time points. A rapid decrease in MyHC mRNA and protein expression occurred by day 5 and persisted at day 15 (P < 0.05). Expression of the atrophy genes MuRF-1 and Atrogin1 was increased at day 5 (P < 0.05). Early MuRF-1 protein content was closely associated with late myofiber atrophy and the severity of weakness.

CONCLUSIONS AND RELEVANCE

Decreased synthesis and increased degradation of MyHCs contribute to ICU-acquired muscle wasting. The rates and time frames suggest that pathogenesis of muscle failure is initiated very early during critical illness. The persisting reduction of MyHC suggests that sustained treatment is required.

Neurofilaments as a plasma biomarker for ICU-acquired weakness: an observational pilot study

Introduction

Early diagnosis of intensive care unit – acquired weakness (ICU-AW) using the current reference standard, that is, assessment of muscle strength, is often hampered due to impaired consciousness. Biological markers could solve this problem but have been scarcely investigated. We hypothesized that plasma levels of neurofilaments are elevated in ICU-AW and can diagnose ICU-AW before muscle strength assessment is possible.

Methods

For this prospective observational cohort study, neurofilament levels were measured using ELISA (NfH^SMI35 antibody) in daily plasma samples (index test). When patients were awake and attentive, ICU-AW was diagnosed using the Medical Research Council scale (reference standard). Differences and discriminative power (using the area under the receiver operating characteristic curve; AUC) of highest and cumulative (calculated using the area under the neurofilament curve) neurofilament levels were investigated in relation to the moment of muscle strength assessment for each patient.

Results

Both the index test and reference standard were available for 77 ICU patients. A total of 18 patients (23%) fulfilled the clinical criteria for ICU-AW. Peak neurofilament levels were higher in patients with ICU-AW and had good discriminative power (AUC: 0.85; 95% CI: 0.72 to 0.97). However, neurofilament levels did not peak before muscle strength assessment was possible. Highest or cumulative neurofilament levels measured before muscle strength assessment could not diagnose ICU-AW (AUC 0.59; 95% CI 0.37 to 0.80 and AUC 0.57; 95% CI 0.32 to 0.81, respectively).

Conclusions

Plasma neurofilament levels are raised in ICU-AW and may serve as a biological marker for ICU-AW. However, our study suggests that an early diagnosis of ICU-AW, before muscle strength assessment, is not possible using neurofilament levels in plasma.

Electronic supplementary material

The online version of this article (doi:10.1186/cc13699) contains supplementary material, which is available to authorized users.

Early Physical Rehabilitation in the ICU: A Review for the Neurohospitalist

Advances in critical care have resulted in improved intensive care unit (ICU) mortality. However, improved ICU survival has resulted in a growing number of ICU survivors living with long-term sequelae of critical illness, such as impaired physical function and quality of life (QOL). In addition to critical illness, prolonged bed rest and immobility may lead to severe physical deconditioning and loss of muscle mass and muscle weakness. ICU-acquired weakness is associated with increased duration of mechanical ventilation and weaning, longer ICU and hospital stay, and increased mortality. These physical impairments may last for years after ICU discharge. Early Physical Medicine and Rehabilitation (PM&R) interventions in the ICU may attenuate or prevent the weakness and physical impairments occurring during critical illness. This article reviews the evidence regarding safety, feasibility, barriers, and benefits of early PM&R interventions in ICU patients and discusses the limited existing data on early PM&R in the neurological ICU and future directions for early PM&R in the ICU.

[ICU acquired neuromyopathy]

ICU acquired neuromyopathy (IANM) is the most frequent neurological pathology observed in ICU. Nerve and muscle defects are merged with neuromuscular junction abnormalities. Its physiopathology is complex. The aim is probably the redistribution of nutriments and metabolism towards defense against sepsis. The main risk factors are sepsis, its severity and its duration of evolution. IANM is usually diagnosed in view of difficulties in weaning from mechanical ventilation, but electrophysiology may allow an earlier diagnosis. There is no curative therapy, but early treatment of sepsis, glycemic control as well as early physiotherapy may decrease its incidence. The outcomes of IANM are an increase in morbi-mortality and possibly long-lasting neuromuscular abnormalities as far as tetraplegia.

A review of the efficacy of neuromuscular electrical stimulation in critically ill patients

BACKGROUND

Muscle wasting in critical illness has been identified as a major clinical concern which can lead to persistent muscle weakness, impede recovery and limit physical function and quality of life in survivors. Neuromuscular electrical stimulation (NMES) has been suggested as an alternative to active exercise in critically ill patients.

OBJECTIVES

To evaluate the efficacy of NMES in critically ill patients by evaluating the research literature.

METHODS

Structured database searches of the Cochrane Library, Ovid (Medline), CINHAL, Scopus and PEDro were completed.

RESULTS

Eight papers were retrieved and methodological quality evaluated using the Critical Appraisal and Skills Program tool. The NMES protocols, outcomes and findings were analysed and, given the methodological heterogeneity, the study findings were synthesised as a narrative. Analysis showed minimal adverse effects in the use of NMES and some potential benefits of NMES on preservation of muscle strength, decreased duration of mechanical ventilation and shorter Intensive Care Unit (ICU) length of stay.

CONCLUSIONS

Evidence of the clinical benefits of NMES in the ICU is inconclusive and provides minimal guidance for use in clinical practice. There is a need for further research in this area.

ICU-based rehabilitation and its appropriate metrics

PURPOSE OF REVIEW

Survival of critically ill patients is frequently associated with significant functional impairment and reduced health-related quality of life. Early rehabilitation of ICU patients has recently been identified as an important focus for interdisciplinary ICU teams. However, the amount of rehabilitation performed in ICUs is often inadequate. The scope of the review is to discuss recent developments in application of assessment tools and rehabilitation in critically ill patients within an interdisciplinary approach.

RECENT FINDINGS

ICU-based rehabilitation has become an important evidence-based component in the management of patients with critical illness. The assessment and evidence-based treatment of these patients should include a focus on prevention and treatment of deconditioning (muscle weakness, joint stiffness, impaired functional performance) and weaning failure (respiratory muscle weakness) to identify targets for rehabilitation. A variety of modalities for assessment and early ICU rehabilitation are supported by emerging clinical research and must be implemented according to the stage of critical illness, comorbidities, and consciousness and cooperation of the patient.

SUMMARY

Daily evaluation of every critically ill patient should include evaluation of the need for bedrest and immobility, and assessment of the potential for early rehabilitation interventions. Early ICU rehabilitation is an interdisciplinary team responsibility, involving physical therapists, occupational therapists, nurses and medical staff.

Critical illness myopathy and GLUT4: significance of insulin and muscle contraction

RATIONALE

Critical illness myopathy (CIM) has no known cause and no treatment. Immobilization and impaired glucose metabolism are implicated.

OBJECTIVES

We assessed signal transduction in skeletal muscle of patients at risk for CIM. We also investigated the effects of evoked muscle contraction.

METHODS

In a prospective observational and interventional pilot study, we screened 874 mechanically ventilated patients with a sepsis-related organ-failure assessment score greater than or equal to 8 for 3 consecutive days in the first 5 days of intensive care unit stay. Thirty patients at risk for CIM underwent euglycemic-hyperinsulinemic clamp, muscle microdialysis studies, and muscle biopsies. Control subjects were healthy. In five additional patients at risk for CIM, we performed corresponding analyses after 12-day, daily, unilateral electrical muscle stimulation with the contralateral leg as control.

MEASUREMENTS AND MAIN RESULTS

We performed successive muscle biopsies and assessed systemic insulin sensitivity and signal transduction pathways of glucose utilization at the mRNA and protein level and glucose transporter-4 (GLUT4) localization in skeletal muscle tissue. Skeletal muscle GLUT4 was trapped at perinuclear spaces, most pronounced in patients with CIM, but resided at the sarcolemma in control subjects. Glucose metabolism was not stimulated during euglycemic-hyperinsulinergic clamp. Insulin signal transduction was competent up to p-Akt activation; however, p-adenosine monophosphate-activated protein kinase (p-AMPK) was not detectable in CIM muscle. Electrical muscle stimulation increased p-AMPK, repositioned GLUT4, locally improved glucose metabolism, and prevented type-2 fiber atrophy.

CONCLUSIONS

Insufficient GLUT4 translocation results in decreased glucose supply in patients with CIM. Failed AMPK activation is involved. Evoked muscle contraction may prevent muscle-specific AMPK failure, restore GLUT4 disposition, and diminish protein breakdown. Clinical trial registered with http://www.controlled-trials.com (registration number ISRCTN77569430).