Electrophysiology of neuromuscular disorders in critical illness

Assessing Intensive Care Unit Acquired Weakness: An Observational Study Using Quantitative Ultrasound Shear Wave Elastography of the Rectus Femoris and Vastus Intermedius

INTRODUCTION

Intensive care unit-acquired weakness (ICUAW) is associated with unfavorable outcomes. The current diagnostic tools for ICUAW are invasive, yield delayed results, and lack precision. This study explored the potential of shear wave elastography (SWE), an innovative ultrasound technique, to evaluate the quality changes in the lower extremity muscles of ICU patients, potentially aiding the early detection of ICUAW.

MATERIALS AND METHODS

We included adult patients diagnosed with ICUAW (average Medical Research Council score < 48) from December 2020 to October 2021. ICU patients were continuously monitored twice daily. Using ultrasonography, we measured the thickness (TH), cross-sectional area (CSA), pennation angle (PA), and SWE (SWE-values) modulus of the bilateral rectus femoris (RF) and vastus intermedius (VI). The diagnostic performance of each parameter was evaluated using sensitivity, specificity, and area under the receiver operating characteristic curve.

RESULTS

Ultrasound quantification assessments were performed in 47 patients, 24 with ICUAW and 23 without ICUAW. Notably, PA decreased (RF: 11.33%, VI: 10.51%), while muscle rigidity increased (RF: 22.39%, VI: 22.50%) in ICUAW patients compared with non-ICUAW patients. The sensitivity and specificity for PA in the RF were 79.17% and 91.30%, respectively, and those for PA in VI were 79.17% and 78.26%, respectively. The use of both combinations yielded 91.67% and 73.91% sensitivity and specificity, respectively. Employing the PA of RF and SWE-values of RF together, we observed a diagnostic prediction sensitivity of 91.67% and a specificity of 60.87%.

CONCLUSIONS

ICUAW patients exhibited increased rigidity of the lower extremity muscles during their hospital stay. Ultrasonic SWE emerged as a reliable and objective tool, offering significant diagnostic value for ICUAW.

Compound Muscle Action Potential and Myosin-Loss Pathology in Patients With Critical Illness Myopathy: Correlation and Prognostication

BACKGROUND AND OBJECTIVES

Prolonged compound muscle action potential (CMAP) duration and preferential loss of myosin are considered the diagnostic hallmarks of critical illness myopathy (CIM); however, their correlation and prognostic values have not been studied. We aimed to investigate the correlation between CMAP duration and myosin loss and their effect on mortality by comparing between patients with CIM with and without myosin loss.

METHODS

We searched the Mayo Clinic Electromyography Laboratory databases (1986-2021) for patients diagnosed with CIM on the basis of prolonged distal CMAP durations (>15 msec in fibular motor nerve studies recording over the tibialis anterior or >8 msec in other motor nerves) and needle EMG findings compatible with myopathy. Electrodiagnostic studies were generally performed within 24 hours after weakness became noticeable. We included only patients who underwent muscle biopsy. Clinical, electrophysiologic, and myopathologic data were reviewed. We conducted myosin/actin ratio analysis when muscle tissue was available. We used the Fisher exact test for categorical data comparisons and the Mann-Whitney 2-tailed test for continuous data. We applied the Kaplan-Meier technique to analyze survival rates.

RESULTS

Twenty patients (13 female patients) were identified [median age at diagnosis of 62.5 years (range: 19-80 years)]. The median onset of weakness was 24 days (range: 1-128) from the first day of intensive care unit admission. Muscle biopsy showed myosin loss in 14 patients, 9 of whom had >50% of myofibers affected (high grade). Type 2 fiber atrophy was observed in 19 patients, 13 of whom also had myosin loss. Patients with myosin loss had higher frequency of steroid exposure (14 vs 3; p = 0.004); higher median number of necrotic fibers per low-power field (2.5 vs 1, p = 0.04); and longer median CMAP duration (msec) of fibular (13.4 vs 8.75, p = 0.02), tibial (10 vs 7.8, p = 0.01), and ulnar (11.1 vs 7.95, p = 0.002) nerves compared with those without. Only patients with high-grade myosin loss had reduced myosin/actin ratios (<1.7). Ten patients died during median follow-up of 3 months. The mortality rate was similar between patients with and without myosin loss. Patients with high-grade myosin loss had a lower overall survival rate than those with low-grade or no myosin loss, but this was not statistically significant (p = 0.05).

DISCUSSION

Myosin loss occurred in 70% of the patients with CIM with prolonged CMAP duration. Longer CMAP duration predicts myosin-loss pathology. The extent of myosin loss marginally correlates with the mortality rate. Our findings highlight the potential prognostic values of CMAP duration and myosin loss severity in predicting disease outcome.

Safety and feasibility of a functional electrical stimulation cycling-based muscular dysfunction diagnostic method in mechanically ventilated patients

BACKGROUND

A nonvolitional diagnostic method based on FES-Cycling technology has recently been demonstrated for mechanically ventilated patients. This method presents good sensitivity and specificity for detecting muscle dysfunction and survival prognosis, even in unconscious patients. As the clinical relevance of this method has already been reported, we aimed to evaluate its safety and feasibility.

METHODS

An observational prospective study was carried out with 20 critically ill, mechanically ventilated patients. The FES-cycling equipment was set in a specific diagnostic mode. For safety determination, hemodynamic parameters and peripheral oxygen saturation were measured before and immediately after the diagnostic protocol, as well as venous oxygen saturation and blood lactate. The creatine phosphokinase level (CPK) was measured before and 24, 48, and 72 h after the test. The time taken to carry out the entire diagnostic protocol and the number of patients with visible muscle contraction (capacity of perceptive muscular recruitment) were recorded to assess feasibility.

RESULTS

Heart rate [91 ± 23 vs. 94 ± 23 bpm (p = 0.0837)], systolic [122 ± 19 vs. 124 ± 19 mm Hg (p = 0.4261)] and diastolic blood pressure [68 ± 13 vs. 70 ± 15 mm Hg (p = 0.3462)], and peripheral [98 (96-99) vs. 98 (95-99) % (p = 0.6353)] and venous oxygen saturation [71 ± 14 vs. 69 ± 14% (p = 0.1317)] did not change after the diagnostic protocol. Moreover, blood lactate [1.48 ± 0.65 vs. 1.53 ± 0.71 mmol/L (p = 0.2320)] did not change. CPK did not change up to 72 h after the test [99 (59-422) vs. 125 (66-674) (p = 0.2799) vs. 161 (66-352) (p > 0.999) vs. 100 (33-409) (p = 0.5901)]. The time taken to perform the diagnostic assessment was 11.3 ± 1.1 min. In addition, 75% of the patients presented very visible muscle contractions, and 25% of them presented barely visible muscle contractions.

CONCLUSIONS

The FES cycling-based muscular dysfunction diagnostic method is safe and feasible. Hemodynamic parameters, peripheral oxygen saturation, venous oxygen saturation, and blood lactate did not change after the diagnostic protocol. The muscle damage marker (CPK) did not increase up to 72 h after the diagnostic protocol.

Outcome, predictors and longitudinal trajectories of subjects with critical illness polyneuropathy and myopathy (CINAMOPS): study protocol of an observational cohort study in a clinical and post-clinical setting

INTRODUCTION

Critical illness polyneuropathy and myopathy (CIP/CIM) are frequent complications in the intensive care unit (ICU) with major consequences for the progress and outcome of subjects. CIP/CIM delays the weaning process, prolongs the hospital stay and increases the mortality rate. Additionally, it may have long-term consequences beyond the hospitalisation phase with prolonged disability. Even though there is growing interest in CIP/CIM, research about the clinical and post-clinical course as well as the middle-term and long-term outcomes of subjects with CIP/CIM is scarce. A large prospective study of critically ill subjects is needed with accurate diagnosis during the acute stage and comprehensive assessment during long-term follow-up.

METHODS AND ANALYSIS

This prospective observational cohort study aims to compare the clinical and post-clinical course of chronically critically ill subjects with and without the diagnosis of CIP/CIM and to determine predictors for the middle-term and long-term outcomes of subjects with CIP/CIM. In addition, the influence of the preclinical health status and the preclinical frailty on the long-term outcome of subjects with CIP/CIM will be investigated.This single-centre study will include 250 critically ill patients who were invasively ventilated for at least 5 days at the ICU and show reduced motor strength. At five study visits at admission and discharge to neurological rehabilitation, and 12, 18 and 24 months after disease onset, a comprehensive test battery will be applied including assessments of functioning and impairment, independence, health-related quality of life, activity and participation, cognition, gait and balance, fatigue, mental health and frailty.Secondary objectives are the documentation of therapy goals, therapy content and achieved milestones during the rehabilitation, to evaluate the clinimetric properties of the Mini-BESTest in critically ill patients, and to evaluate the time course and outcome of subjects with CIP/CIM after SARS-CoV-2 infection.

ETHICS AND DISSEMINATION

The study was approved by the ethical committee of the Ludwig-Maximilians University Munich. Participants will be included in the study after having signed informed consent.Results will be published in scientific, peer-reviewed journals and at national and international conferences.

TRIAL REGISTRATION NUMBER

German Clinical Trial Register (DRKS00021753).

Physical and Cognitive Impairment in Acute Respiratory Failure

Recent research has brought renewed attention to the multifaceted physical and cognitive dysfunction that accompanies acute respiratory failure (ARF). This state-of-the-art review provides an overview of the evidence landscape encompassing ARF-associated neuromuscular and neurocognitive impairments. Risk factors, mechanisms, assessment tools, rehabilitation strategies, approaches to ventilator liberation, and interventions to minimize post-intensive care syndrome are emphasized. The complex interrelationship between physical disability, cognitive dysfunction, and long-term patient-centered outcomes is explored. This review highlights the need for comprehensive, multidisciplinary approaches to mitigate morbidity and accelerate recovery.

Functional electrical stimulation cycling-based muscular evaluation method in mechanically ventilated patients

BACKGROUND

Intensive care acquired muscle weakness is a common feature in critically ill patients. Beyond the therapeutic uses, FES-cycling could represent a promising nonvolitional evaluation method for detecting acquired muscle weakness.

OBJECTIVES

To assess whether FES-cycling is able to identify muscle dysfunctions, and to evaluate the survival rate in patients with detected muscle dysfunction.

METHODS

A prospective observational study was carried out, with 29 critically ill patients and 20 healthy subjects. Maximum torque and power achieved were recorded, in addition to the stimulation cost, and patients were followed up for six months.

RESULTS

Torque (2.64 [1.53 to 4.81] vs 6.03 [4.56 to 6.73] Nm) and power (3.31 [2.33 to 6.37] vs 6.35 [5.22 to 10.70] watts) were lower and stimulation cost (22 915 [5069 to 37 750] vs 3411 [2080 to 4024] μC/W) was higher in patients compared to healthy people (p < 0.05). Surviving patients showed a nonsignificant difference in power and torque in relation to nonsurvivors (p > 0.05), but they had a lower stimulation cost (4462 [3598 to 11 788] vs 23 538 [10 164 to 39 836] μC/W) (p < 0.05). In total, 34% of all patients survived during the six months of follow-up. Furthermore, 62% of patients with a stimulation cost below 15 371 μC/W and 7% of patients with a stimulation cost above 15 371 μC/W survived.

CONCLUSIONS

FES-cycling has good sensitivity and specificity for detecting muscle disorders. Critical patients have low torque and power and a high stimulation cost. Stimulation cost is related to survival. A low stimulation cost was related to a 3 times greater chance of survival.

Myasthenia Gravis Mimicking Status Asthmaticus: The Hidden Crisis

Status asthmaticus is a severe form of aggravation of asthma, whereas myasthenia gravis (MG) is a rare neuromuscular condition characterised by exhaustion and muscle weakness. Myasthenic crisis can occasionally manifest with symptoms that resemble status asthmaticus, which can result in an incorrect diagnosis and ineffective therapy. In addition to discussing the therapeutic implications, this abstract attempts to draw attention to the difficulties in distinguishing between status asthmaticus and myasthenia crisis and the importance of diagnosing subtle signs of MG. In this case, we present a 55-year-old female, with a misdiagnosed case of bronchial asthma, who presented with shortness of breath at rest for two to three days and was suspected to have an acute exacerbating episode of asthma. She was later evaluated for non-respiratory causes of dyspnea on noticing subtle signs of ptosis and was found to have an active myasthenic crisis. Although this case presented typically as status asthmaticus, it did not respond to conventional treatment of it, and on the contrary, it worsened. Hence, it is necessary to look for subtle signs of MG and promptly differentiate it from other similar emergency events to help administer accurate treatment which can prove life-saving.

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.

A predictive model for the classification of emergency intensive care unit patients with systemic inflammatory response syndrome based on a similarity network fusion algorithm

BACKGROUND

Intensive care unit-acquired weakness (ICU-AW) is a prevalent and severe neuromuscular complication in critically ill patients. It is a consequence of critical illness and is characterized by systemic inflammatory response syndrome (SIRS)-induced metabolic stress and multiple organ dysfunctions. Moreover, ICU-AW is one of the most important factors affecting the prognosis of patients with SIRS, Electrophysiological examination is an effective method for early identification and monitoring of the course of the disease and is essential for accurate diagnosis of critical illness neuromyopathy (CINM). The data-intensive ICU environment is ideal for implementing the similarity network fusion (SNF) method. The objective of this study was to establish and validate a ICU-AW predictive model in SIRS patients, providing a practical tool for early clinical prediction.

METHODS

Clinical characteristics, demographic data, longitudinal neurophysiological data, and disease severity indicators of the enrolled patients were recorded. The patient data included nerve conduction, F-wave, and direct muscle stimulation (DMS) data from 94 follow-up visits as well as various scores, including Medical Research Council (MRC), sequential organ failure assessment (SOFA), acute physiology and chronic health evaluation II (APACHE II) scores and C-reactive protein (CRP). This algorithm was used to analyze electrophysiological data of emergency intensive care unit (EICU) patients with SIRS and fully exploit their similarities in age, sex, body mass index, and electrophysiological data by fusing the similarity networks of these patients with different sets of attributes. Existing patients was performed a clustering analysis and predicted the classification of new patients using spectral clustering and label propagation algorithms on the fusion network, respectively.

RESULTS

Classification prediction model categorical of ICUAW in Patients with SIRS was highly consistent with the clinical diagnosis and had high accuracy and discriminative ability. The model captures the importance of advanced age and lung infections as risk factors for ICU-AW and also demonstrates the significant prognostic value of DMS in EICU patients with SIRS and its ability to predict the development of clinical muscle weakness.

CONCLUSIONS

Electrophysiological abnormalities are a critical feature of both ICU-AW and non-ICU-AW. Modeling the prediction of SIRS patients progressing to ICUAW which is conducive to early intervention, mechanism studies, and patient rehabilitation.

Can the electrically stimulated manual muscle test differentiate upper from lower motor neuron injury in persons with acute SCI?

OBJECTIVE

To determine if the motor response on the stimulated manual muscle test (SMMT) in muscles with a grade 0 motor score on the manual muscle test (MMT) can differentiate lower motor neuron (LMN) from upper motor neuron (UMN) injury based on the presence of spontaneous activity (SA) with needle EMG.

DESIGN

Prospective Study.

PARTICIPANTS/METHODS

Twenty-one subjects with acute traumatic cervical SCI.

METHODS

An upper extremity International Standards for Neurological Classification of Spinal Cord Injury (ISNCSCI) evaluation was completed on all subjects. A needle EMG and an electrically stimulated manual muscle test (SMMT) were completed on all key upper extremity muscles with a MMT motor score of zero.

RESULTS

The MMT, SMMT and Needle EMG were done on 77 muscles. The SMMT motor score was 0 on 10 muscles and >1 on 67 muscles. The needle EMG identified spontaneous activity (SA) in 55/77 muscles. Seventy percent (7/10) of the muscles with MMT and SMMT motor score of zero demonstrated SA on EMG. Seventy-two percent (48/67) of the muscles with MMT motor score = 0 and SMMT motor score ≥1 demonstrated SA on EMG.

CONCLUSION

In our study, 70% of the muscles with a SMMT motor response of zero and 72% of the muscles with a SMMT motor response greater than or equal to one demonstrated SA on EMG. The use of the SMMT as a clinical measure to differentiate LMN from UMN integrity may be limited when applied.

Facial nerve neurographies in intensive care unit-acquired weakness

BACKGROUND

Patients with an intensive care unit-acquired weakness (ICU-AW) often present clinically with severe paresis of the limb and trunk muscles while facial muscles appear less affected. To investigate whether the facial nerves are partially spared from this condition, we performed both peripheral and cranial nerve conduction studies in critically ill patients.

METHODS

In patients requiring prolonged ICU therapy, the motor and sensory nerve conduction velocities of the peroneal, ulnar and facial nerves and the muscle action potentials of the associated muscles, as well as the orbicularis oculi reflexes were assessed shortly after admission, and on ICU days 7 and 14.

RESULTS

Eighteen patients were included in the final data analysis (average age 54.2 ± 16.8 years, 8 females). The amplitudes of the peroneal nerve compound muscle action potentials (CMAPs) were reduced in all patients at ICU days 7 and 14 (F(1.39; 23.63) = 13.85; p < 0.001). There was no similar decrease in the CMAP amplitudes of the ulnar or facial nerve. Other parameters of nerve function (latencies, sensory and motor nerve conduction velocities, sensory nerve action potentials) remained unchanged. The reproducibility of the orbicularis oculi reflex was reduced during the disease course, while its latencies did not change significantly during the disease course.

CONCLUSIONS

There is a relative preservation of CMAPs in facial and hand as opposed to foot muscles. This is compatible with the clinical observation that the facial muscles in patients with ICU-AW are less severely affected. This may be primarily a function of the nerve length, and consequently more robust trophic factors in shorter nerves. Trial registration This study was prospectively registered in the German Clinical Trial Register on April 20th 2020 (DRKS00021467).

Neuromuscular disorders in women and men with spinal cord injury are associated with changes in muscle and tendon architecture

OBJECTIVE

The present study aimed to determine the association between neuromuscular function, motor function impairment, and muscle and tendon structures in individuals with spinal cord injury (SCI) compared to a control (non-disabled) population.

DESIGN

A cross-sectional study with a control group.

SETTING

Center of Adapted Sports Training and Special Physical Education.

PARTICIPANTS

Fifteen individuals with SCI and motor function impairments participated in the study. A paired non-disabled group was recruited for comparison.

INTERVENTIONS

Not applicable.

OUTCOME MEASURES

Muscle (biceps brachii, rectus femoris, vastus lateralis, vastus medialis, and tibialis anterior) and tendon (quadriceps and patellar tendons) structures were assessed by ultrasound imaging (thickness, pennation angle, fascicle length, and echogenicity). Neuromuscular electrophysiological disorders were also assessed using electrodiagnosis techniques (stimulus non-responsivity and chronaxie) in the same muscles.

RESULTS

Except for the biceps brachii muscle, muscle thickness, pennation angle, and fascicle length were lower (p < 0.01) while echogenicity and chronaxie were greater (p < 0.01) in SCI participants. The SCI participants had a higher prevalence of neuromuscular electrophysiological disorders for all muscles, except the biceps brachii.

CONCLUSION

Neuromuscular disorders occur in association with muscle and tendon maladaptation in individuals with chronic SCI. A higher prevalence of electrophysiological disorders suggests an acquired polyneuromyopathy for muscles with motor function impairment even though the muscle was innerved, in addition to widespread muscle atrophy.

Assessment of neuromuscular electrical stimulation in critically ill patients: physical therapists’ knowledge and barriers to its use

ABSTRACT Transcutaneous neuromuscular electrical stimulation (NMES) is considered an important tool to prevent muscle mass and strength loss in patients admitted to intensive care units (ICU). This study aimed to evaluate physical therapists’ profile and knowledge of NMES and identify the main barriers to its use in ICUs. This observational cross-sectional study was conducted via a structured questionnaire created by the authors. It consisted of 12 objective questions to analyze physical therapists’ knowledge of NMES use in critically ill patients. Physical therapists were invited to participate in this study during an international symposium on NMES. In total, 56 physical therapists, with a mean age of 33.5±7.2 years and working an average of 9.7±7 years after graduation, completed the survey. Overall, 34 respondents worked in ICUs, of which only four (12%) reported regular NMES use in their ICUs. We found a low average of correct answers to our questionnaire (25%; 3/12). The main barriers reported to using NMES in ICUs were lack of knowledge (28; 50%) and equipment (24; 43%). The number of correct answers expert and non-expert physical therapists was not statistically significant (p=0.68). Thus, we observed participants’ poor knowledge of NMES use in critically ill patients. Respondents showed that NMES has been underused in their ICUs. Lack of knowledge and equipment seems to be the main barriers for the use of NMES in ICUs.

What Is in the Myopathy Literature?

ABSTRACT

We cover intensive care unit-acquired neuromuscular disorders associated with coronavirus disease 2019. Outcomes may be worse than expected in these patients, and there is some evidence that coronavirus disease 2019 causes myopathy directly. Corticosteroid regimens in Duchenne muscular dystrophy are addressed including outcomes in pulmonary and cardiac function. A recent article notes a continued diagnostic delay in Duchenne muscular dystrophy. An interesting report of a Canary Islands cohort of patients with oculopharyngeal muscular dystrophy is discussed. Features and clinical pearls related to a series of patients with limb-girdle muscle dystrophy R12 (anoctaminopathy) and a misdiagnosis of idiopathic inflammatory myopathy are provided. The last section on autoimmune myopathy includes articles on clinical and pathologic features associated with myositis-specific antibodies and dermatomyositis, the epidemiology of immune-mediated necrotizing myopathies (IMNMs) in Olmsted County, Minnesota, and features of a German cohort of hydroxy-3-methylglutaryl coenzyme A reductase-associated IMNM. A recent article proposes the benefit of early intravenous immunoglobulin use for adults with IMNM. We also highlight a report of 2 unusual cases of antisignal recognition particle myopathy presenting with asymmetric distal weakness.

Perceived utility of electrodiagnostic testing in critical illness myopathy and polyneuropathy: A survey of intensive care unit providers

INTRODUCTION/AIMS

Critical illness myopathy (CIM) and critical illness polyneuropathy (CIP) are common disorders associated with substantial morbidity. Electrodiagnostic studies (EDx) are effective in diagnosing CIM/CIP and identifying mimicking conditions. We surveyed intensive care unit (ICU) providers to better understand their approach to ICU-acquired weakness (ICU-AW) and the perceived utility of EDx.

METHODS

This was a single health system, Web-based survey of ICU providers.

RESULTS

Survey responses were received from 52 providers with a response rate of 22.1%. Most providers were somewhat familiar with CIM/CIP and median perceived prevalence was 30-49%. The majority (92.3%) of providers had no standard evaluation approach for ICU-AW. Electrodiagnostic testing was commonly considered, but many providers obtained it infrequently in presumed CIM/CIP cases. Electrodiagnostic studies were used to rule out other causes of weakness or to confirm the diagnosis of CIM/CIP. Many providers ordered EDx within 1 wk of identifying weakness. Finally, EDx were overshadowed by personal experience as the most helpful management tool for ICU-AW.

DISCUSSION

Overall, ICU providers perceive that CIM/CIP are commonly encountered, but they may not have a standard approach to evaluation. Clinical experience increased familiarity of ICU-AW and is central to management. EDx results are usually thought to be helpful, albeit not often ordered, and more study is needed to determine when implementation is of most assistance. Increasing education and developing institutional standards may lead to increased awareness and improved evaluation of CIM/CIP, but more study is needed to determine if algorithmic approaches would change patient outcomes.

The challenge of diagnosing Guillain–Barre syndrome in patients with COVID-19 in the intensive care unit

Various neurological complications have been described in COVID-19 patients, especially Guillain–Barre syndrome (GBS). The underlying mechanisms on the association between SARS-CoV-2 infection and GBS remain unclear, but several hypotheses have been proposed. It seems that post-SARS-CoV-2 GBS shares many characteristics with classic post-infectious GBS; however, it may occur in sedated and intubated patients hospitalized in the intensive care unit for SARS-CoV-2 acute respiratory distress syndrome, which presents challenges in the diagnosis and treatment of GBS. In this study, we describe three cases of post-SARS-CoV-2 GBS that were hospitalized in the intensive care unit.

Intensive Care Unit-Acquired Weakness and the COVID-19 Pandemic: A Clinical Review

Patients with severe cases of coronavirus disease 2019 (COVID-19) often become critically ill requiring intensive care unit (ICU) management. These individuals are at risk for developing ICU-acquired weakness (ICUAW), a multifactorial condition in which polyneuropathy, myopathy, and/or disuse muscle atrophy result in motor weakness. This weakness is thought to contribute to the long-term functional disability frequently observed in survivors of critical illness. This review discusses the current evidence regarding the epidemiology, pathophysiology, evaluation, risk factors, and rehabilitation-specific management of ICUAW in patients with COVID-19. Due to the novelty of COVID-19, the exact prevalence of ICUAW is not well delineated among COVID-19 patients. However, ICUAW has been reported in this population with retrospective studies showing weakness occurring in up to 45.5% of patients with severe COVID-19. There are multiple risk factors for developing ICUAW among COVID-19 patients which include premorbid health status, sepsis, multiple organ failure, mechanical ventilation, immobilization, neuromuscular blockade, corticosteroid use, and glycemic control. ICUAW is more likely to occur after prolonged mechanical ventilation and long hospital stays and can be diagnosed with manual muscle and electrodiagnostic testing. While the long-term sequela of COVID-19 after ICU stays is not fully studied, increasing evidence indicates significant risk for this population developing long-term functional impairments. Establishing post-acute rehabilitation programs for COVID-19 survivors will be important for recovery of endurance, mobility, and function. This article is protected by copyright. All rights reserved.

Intensive care unit-acquired weakness: Questions the clinician should ask

Intensive care unit (ICU)-acquired weakness (ICU-AW) is defined as clinically detected weakness in critically ill patients in whom there is no plausible etiology other than critical illness. Using electrophysiological methods, patients with ICU-AW are classified in three subcategories: critical illness polyneuropathy, critical illness myopathy and critical illness neuromyopathy. ICU-AW is a frequent complication occurring in critical ill patients. Risk factors include illness severity and organ failure, age, hyperglycemia, parenteral nutrition, drugs and immobility. Due to short- and long-term complications, ICU-AW results in longer hospital stay and increased mortality. Its management is essentially preventive avoiding modifiable risk factors, especially duration of sedation and immobilization that should be as short as possible. Pharmacological approaches have been studied but none have proven efficacy. In the present review, we propose practical questions that the clinician should ask in case of acquired weakness during ICU stay: when to suspect ICU-AW, what risk factors should be identified, how to diagnose ICU-AW, what is the prognosis and how can recovery be improved?

Electrodiagnostic Assessment of Myopathy

Electrodiagnostic testing is a useful tool in the evaluation of suspected myopathy and helps to confirm the presence of a myopathy and exclude disease mimickers. The electrodiagnostic pattern of findings during testing guides subsequent laboratory evaluation, genetic testing, and in identifying potential muscle biopsy targets. It also provides a baseline for subsequent assessment of disease progression or response to therapy. This article summarizes the approach to electrodiagnostic assessment in various myopathic disorders.

Neuromuscular Disorders in the Intensive Care Unit

PURPOSE OF REVIEW

This article discusses the pathophysiology, presentation, diagnosis, treatment, and prognosis of common neuromuscular disorders seen in the intensive care unit, including Guillain-Barré syndrome, myasthenia gravis, and intensive care unit-acquired weakness.

RECENT FINDINGS

Guillain-Barré syndrome can have an excellent prognosis if patients are diagnosed early, appropriately treated, and monitored for complications, including respiratory failure and dysautonomia. Intensive care unit-acquired weakness increases overall mortality in patients who are critically ill, and distinguishing between critical illness myopathy and critical illness polyneuropathy may have important prognostic implications.

SUMMARY

Neuromuscular disorders are not rare in the intensive care unit setting, and precise identification and treatment of these conditions can greatly impact long-term outcomes.

Systemic lupus erythematosus and critical illness polyneuropathy

Systemic lupus erythematosus (SLE) is a chronic disease of connective tissue with multi-organ involvement. Manifestation in the nervous system is one of the most difficult symptoms to assess and interpret. The aim of the study is to indicate diagnostic problems in patients with SLE in whom neurological symptoms are present at the time of diagnosis of SLE but also with complications that occurred after diagnosis.

In the presented case, the appearance of flaccid tetraparesis with areflexia suggested peripheral damage to the nervous system. In the electromyography performed in this patient, acute axonal polyneuropathy was mainly suspected. Further differential diagnosis should consider other acute and subacute developing polyneuropathies. Guillain-Barré polyneuropathy deserves special attention.

To our knowledge, this is the first case documented in the literature of the coexistence of critical illness polyneuropathy and SLE.

Severe acute myopathy following SARS-CoV-2 infection: a case report and review of recent literature

Background

SARS-CoV2 virus could be potentially myopathic. Serum creatinine phosphokinase (CPK) is frequently found elevated in severe SARS-CoV2 infection, which indicates skeletal muscle damage precipitating limb weakness or even ventilatory failure.

Case presentation

We addressed such a patient in his forties presented with features of severe SARS-CoV2 pneumonia and high serum CPK. He developed severe sepsis and acute respiratory distress syndrome (ARDS) and received intravenous high dose corticosteroid and tocilizumab to counter SARS-CoV2 associated cytokine surge. After 10 days of mechanical ventilation (MV), weaning was unsuccessful albeit apparently clear lung fields, having additionally severe and symmetric limb muscle weakness. Ancillary investigations in addition with serum CPK, including electromyogram, muscle biopsy, and muscle magnetic resonance imaging (MRI) suggested acute myopathy possibly due to skeletal myositis.

Conclusion

We wish to stress that myopathogenic medication in SARS-CoV2 pneumonia should be used with caution. Additionally, serum CPK could be a potential marker to predict respiratory failure in SARS-CoV2 pneumonia as skeletal myopathy affecting chest muscles may contribute ventilatory failure on top of oxygenation failure due to SARS-CoV2 pneumonia.

Clinical and neurophysiological characterization of muscular weakness in severe COVID-19

Objective

To report clinical and electroneuromyographic (ENMG) characteristics of patients affected by severe COVID-19 infection, evaluated for muscular weakness.

Materials and methods

ENMGs performed for evaluation of diffuse weakness in patients who could not be discharged from semi-intensive care COVID unit because of difficulties in ventilation weaning were reviewed. Patients with severe COVID-19 infection who had undergone endotracheal intubation and able to co-operate were considered. ENMG protocol was focused on neurophysiological items that excluded or confirmed critical illness polyneuropathy (CIP), myopathy (CIM), or polyneuromyopathy (CIPM). Standardized clinical evaluation was performed using Medical Research Council (MRC) sum score.

Results

Eight patients were included in the study. All presented known risk factors for intensive care unit-acquired weakness (ICU-AW), and none of them had history of underlying neuromuscular disorders. ENMG findings were normal in two patients, while only two patients had an altered MRC sum score (< 48). Neuromuscular involvement was diagnosed in 6/8 patients (75%): 2 had CIP, 1 had possible CIM, 1 had CIPM, while 1 patient, with clinically evident weakness but equivocal ENMG findings, was classified as ICU-AW. Finally, 1 patient was diagnosed with acute demyelinating neuropathy. Patients with neuromuscular involvement were those with longer intubation duration and higher levels of IL-6 at admission.

Conclusion

Neuromuscular complications are frequent in severe COVID-19 and cannot be excluded by MRC sum scores above 48. Standardized ENMG is helpful in guiding diagnosis when clinical evaluation is not reliable or possible. Elevated IL-6 at admission may be a predictor biomarker of ICU-AW in COVID-19.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10072-021-05110-8.

Stiff-person syndrome coexisting with critical illness polyneuropathy: A case report

RATIONALE

Stiff-person syndrome (SPS) is an uncommon neurological disorder with autoimmune features. Here, we report a 60-year-old man with SPS associated with critical illness polyneuropathy (CIP). CIP was diagnosed during an episode of acute respiratory failure secondary to muscular rigidity and spasms, which has rarely been reported in this condition. The overlapping of CIP and SPS complicated the case.

PATIENT CONCERNS

A 60-year-old man presented with gradual onset of cramps, stiffness, and rigidity in his lower limbs 1 year before admission, which eventually led to inability to stand and walk. The persistent nature of his symptoms progressed to frequent acute episodes of dyspnea and he was admitted to intensive care unit (ICU).

DIAGNOSIS

SPS had been diagnosed after 2 tests of electromyography (EMG) and the detection of an elevated anti-GAD65 antibody titer. During the first EMG, low or absent compound muscle action potentials (CMAP), and sensory nerve action potentials (SNAP) were shown. Therefore, the diagnosis of SPS coexisting with CIP was made.

INTERVENTIONS

Symptomatic treatment was initiated with oral clonazepam (0.5 mg Bid) and baclofen (5 mg Bid). Intravenous immunoglobulin (IVIG) (0.4 g/kg/d) was administered for the patient for 5 days after admission. We observed a significant clinical improvement during the administration period, and the patient became ambulatory.

OUTCOMES

On follow-up, the patient reported complete relief of his pain and rigidity.

LESSONS

We report this special case to address the varied clinical features of SPS. Electrophysiological testing is an important diagnostic approach. Accurate recognition of the disease ensures that the patients can be given appropriate treatment without delay.

Neurogenic vs. Myogenic Origin of Acquired Muscle Paralysis in Intensive Care Unit (ICU) Patients: Evaluation of Different Diagnostic Methods

Introduction. The acquired muscle paralysis associated with modern critical care can be of neurogenic or myogenic origin, yet the distinction between these origins is hampered by the precision of current diagnostic methods. This has resulted in the pooling of all acquired muscle paralyses, independent of their origin, into the term Intensive Care Unit Acquired Muscle Weakness (ICUAW). This is unfortunate since the acquired neuropathy (critical illness polyneuropathy, CIP) has a slower recovery than the myopathy (critical illness myopathy, CIM); therapies need to target underlying mechanisms and every patient deserves as accurate a diagnosis as possible. This study aims at evaluating different diagnostic methods in the diagnosis of CIP and CIM in critically ill, immobilized and mechanically ventilated intensive care unit (ICU) patients. Methods. ICU patients with acquired quadriplegia in response to critical care were included in the study. A total of 142 patients were examined with routine electrophysiological methods, together with biochemical analyses of myosin:actin (M:A) ratios of muscle biopsies. In addition, comparisons of evoked electromyographic (EMG) responses in direct vs. indirect muscle stimulation and histopathological analyses of muscle biopsies were performed in a subset of the patients. Results. ICU patients with quadriplegia were stratified into five groups based on the hallmark of CIM, i.e., preferential myosin loss (myosin:actin ratio, M:A) and classified as severe (M:A < 0.5; n = 12), moderate (0.5 ≤ M:A < 1; n = 40), mildly moderate (1 ≤ M:A < 1.5; n = 49), mild (1.5 ≤ M:A < 1.7; n = 24) and normal (1.7 ≤ M:A; n = 19). Identical M:A ratios were obtained in the small (4–15 mg) muscle samples, using a disposable semiautomatic microbiopsy needle instrument, and the larger (>80 mg) samples, obtained with a conchotome instrument. Compound muscle action potential (CMAP) duration was increased and amplitude decreased in patients with preferential myosin loss, but deviations from this relationship were observed in numerous patients, resulting in only weak correlations between CMAP properties and M:A. Advanced electrophysiological methods measuring refractoriness and comparing CMAP amplitude after indirect nerve vs. direct muscle stimulation are time consuming and did not increase precision compared with conventional electrophysiological measurements in the diagnosis of CIM. Low CMAP amplitude upon indirect vs. direct stimulation strongly suggest a neurogenic lesion, i.e., CIP, but this was rarely observed among the patients in this study. Histopathological diagnosis of CIM/CIP based on enzyme histochemical mATPase stainings were hampered by poor quantitative precision of myosin loss and the impact of pathological findings unrelated to acute quadriplegia. Conclusion. Conventional electrophysiological methods are valuable in identifying the peripheral origin of quadriplegia in ICU patients, but do not reliably separate between neurogenic vs. myogenic origins of paralysis. The hallmark of CIM, preferential myosin loss, can be reliably evaluated in the small samples obtained with the microbiopsy instrument. The major advantage of this method is that it is less invasive than conventional muscle biopsies, reducing the risk of bleeding in ICU patients, who are frequently receiving anticoagulant treatment, and it can be repeated multiple times during follow up for monitoring purposes.

Toxic Myopathies

PURPOSE OF REVIEW

This article reviews the pathogenesis, clinical features, and management of toxic myopathy related to common medications, critical illness, and illicit substances.

RECENT FINDINGS

Muscle symptoms are common among statin users and are usually reversible after discontinuation of the statin; rarely, however, statins trigger an immune-mediated necrotizing myopathy that persists and requires immunomodulatory therapy. Autoantibodies targeting 3-hydroxy-3-methylglutaryl coenzyme A reductase can distinguish the toxic and immune-mediated forms. Immune checkpoint inhibitors, increasingly used in the treatment of advanced cancer, have recently been associated with the development of inflammatory myositis. A reversible mitochondrial myopathy has long been associated with zidovudine, but recent reports elucidate the risk of myopathy with newer antivirals, such as telbivudine and raltegravir.

SUMMARY

The medications most commonly associated with myopathy include statins, amiodarone, chloroquine, hydroxychloroquine, colchicine, certain antivirals, and corticosteroids, and myopathy can occur with chronic alcoholism. Certain clinical, electrodiagnostic, and histologic features can aid in early recognition. Stopping the use of the offending agent reverses symptoms in most cases, but specific and timely treatment may be required in cases related to agents that trigger immune-mediated muscle injury.

Neuromuscular electrical stimulation in critically ill traumatic brain injury patients attenuates muscle atrophy, neurophysiological disorders, and weakness: a randomized controlled trial

Background

Critically ill traumatic brain injury (TBI) patients experience extensive muscle damage during their stay in the intensive care unit. Neuromuscular electrical stimulation (NMES) has been considered a promising treatment to reduce the functional and clinical impacts of this. However, the time needed for NMES to produce effects over the muscles is still unclear. This study primarily aimed to assess the time needed and effects of an NMES protocol on muscle architecture, neuromuscular electrophysiological disorder (NED), and muscle strength, and secondarily, to evaluate the effects on plasma systemic inflammation, catabolic responses, and clinical outcomes.

Methods

We performed a randomized clinical trial in critically ill TBI patients. The control group received only conventional physiotherapy, while the NMES group additionally underwent daily NMES for 14 days in the lower limb muscles. Participants were assessed at baseline and on days 3, 7, and 14 of their stay in the intensive care unit. The primary outcomes were assessed with muscle ultrasound, neuromuscular electrophysiology, and evoked peak force, and the secondary outcomes with plasma cytokines, matrix metalloproteinases, and clinical outcomes.

Results

Sixty participants were randomized, and twenty completed the trial from each group. After 14 days, the control group presented a significant reduction in muscle thickness of tibialis anterior and rectus femoris, mean of - 0.33 mm (- 14%) and - 0.49 mm (- 21%), p < 0.0001, respectively, while muscle thickness was preserved in the NMES group. The control group presented a higher incidence of NED: 47% vs. 0% in the NMES group, p < 0.0001, risk ratio of 16, and the NMES group demonstrated an increase in the evoked peak force (2.34 kg/f, p < 0.0001), in contrast to the control group (- 1.55 kg/f, p < 0.0001). The time needed for the NMES protocol to prevent muscle architecture disorders and treat weakness was at least 7 days, and 14 days to treat NED. The secondary outcomes exhibited less precise results, with confidence intervals that spanned worthwhile or trivial effects.

Conclusions

NMES applied daily for fourteen consecutive days reduced muscle atrophy, the incidence of NED, and muscle weakness in critically ill TBI patients. At least 7 days of NMES were required to elicit the first significant results.

Trial registration

The trial was registered at ensaiosclinicos.gov.br under protocol RBR-8kdrbz on 17 January 2016.

Critical Care of Neuromuscular Disorders

PURPOSE OF REVIEW

Weakness is a common reason patients are seen in neurologic consultation. This article reviews the differential diagnosis of neuromuscular disorders in the intensive care unit (ICU), discusses the intensive care needs and evaluation of respiratory failure in patients with neuromuscular disorders, and provides a practical guide for management.

RECENT FINDINGS

Although primary neuromuscular disorders used to be the most common cause for weakness from peripheral nervous system disease in the ICU, a shift toward ICU-acquired weakness is observed in today's clinical practice. Therefore, determining the cause of weakness is important and may have significant prognostic implications. Guillain-Barré syndrome and myasthenia gravis remain the most common primary neuromuscular disorders in the ICU. In patients with myasthenia gravis, it is important to be vigilant with the airway and institute noninvasive ventilation early in the course of the disease to attempt to avoid the need for intubation. On the other hand, patients with Guillain-Barré syndrome should be intubated without delay if the airway is at risk to avoid further complications. In patients with ICU-acquired weakness, failure to wean from the ventilator is usually the challenge. Early mobility, glucose control, minimizing sedation, and avoiding neuromuscular blocking agents remain the only therapeutic regimen available for ICU-acquired weakness.

SUMMARY

Critical care management of neuromuscular disorders requires a multidisciplinary approach engaging members of the ICU and consultative teams. Developing an airway management protocol could have implications on outcome and length of stay for patients with neuromuscular disorders in the ICU. Tending to the appropriate nuances of each patient who is critically ill with a neuromuscular disorder through evidence-based medicine can also have implications on length of stay and outcome.

Muscle weakness: Understanding the principles of myopathy and neuropathy in the critically ill patient and the management options

Myo-neuropathy of the critically ill patient is a difficult nosological entity to understand and manage. It appears soon after injury, and it is estimated that 20-30% of patients admitted to Intensive Care Units will develop it in some degree. Although muscular and nervous involvement are related, the former has a better prognosis. Myo-neuropathy associates to more morbidity, longer stay in Intensive Care Unit and in hospital, and also to higher costs and mortality. It is considered part of the main determinants of the new entities: the Chronic Critical Patient and the Post Intensive Care Syndrome. This update focuses on aetiology, pathophysiology, diagnosis and strategies that can prevent, alleviate and/or improve muscle (or muscle-nerve) weakness.

Clinical review: peripheral muscular ultrasound in the ICU

Muscular weakness developing from critical illness neuropathy, myopathy and muscle atrophy has been characterized as intensive care unit-acquired weakness (ICUAW). This entity occurs commonly during and after critical care stay. Various causal factors for functional incapacity have been proposed. Among these, individual patient characteristics (such as age, comorbidities and nutritional status), acting in association with sustained bed rest and pharmacological interventions (included the metabolic support approach), seem influential in reducing muscular mass. Long-term outcomes in heterogeneous ICUAW populations include transient disability in 30% of patients and persistent disabilities that may occur even in patients with nearly complete functional recovery. Currently available tools for the assessment of skeletal muscle mass are imprecise and difficult to perform in the ICU setting. A valid alternative to these imaging modalities is muscular ultrasonography, which allows visualization and classification of muscle characteristics by cross-sectional area, muscle layer thickness, echointensity by grayscale and the pennation angle). The aim of this narrative review is to describe the current literature addressing muscular ultrasound for the detection of muscle weakness and its potential impact on treatment and prognosis of critically ill patients when combined with biomarkers of muscle catabolism/anabolism and bioenergetic state. In addition, we suggest a practical flowchart for establishing an early diagnosis.

RNA-sequencing reveals altered skeletal muscle contraction, E3 ligases, autophagy, apoptosis, and chaperone expression in patients with critical illness myopathy

Background

Critical illness myopathy (CIM) is associated with severe skeletal muscle wasting and impaired function in intensive care unit (ICU) patients. The mechanisms underlying CIM remain incompletely understood. To elucidate the biological activities occurring at the transcriptional level in the skeletal muscle of ICU patients with CIM, the gene expression profiles, potential upstream regulators, and enrichment pathways were characterized using RNA sequencing (RNA-seq). We also compared the skeletal muscle gene signatures in ICU patients with CIM and genes perturbed by mechanical loading in one leg of the ICU patients, with an aim of reducing the loss of muscle function.

Methods

RNA-seq was used to assess gene expression changes in tibialis anterior skeletal muscle samples from seven critically ill, immobilized, and mechanically ventilated ICU patients with CIM and matched control subjects. We also examined skeletal muscle gene expression for both legs of six ICU patients with CIM, where one leg was mechanically loaded for 10 h/day for an average of 9 days.

Results

In total, 6257 of 17,221 detected genes were differentially expressed (84% upregulated; p < 0.05 and fold change ≥ 1.5) in skeletal muscle from ICU patients with CIM when compared to control subjects. The differentially expressed genes were highly associated with gene changes identified in patients with myopathy, sepsis, long-term inactivity, polymyositis, tumor, and repeat exercise resistance. Upstream regulator analysis revealed that the CIM signature could be a result of the activation of MYOD1, p38 MAPK, or treatment with dexamethasone. Passive mechanical loading only reversed expression of 0.74% of the affected genes (46 of 6257 genes).

Conclusions

RNA-seq analysis revealed that the marked muscle atrophy and weakness observed in ICU patients with CIM were associated with the altered expression of genes involved in muscle contraction, newly identified E3 ligases, autophagy and calpain systems, apoptosis, and chaperone expression. In addition, MYOD1, p38 MAPK, and dexamethasone were identified as potential upstream regulators of skeletal muscle gene expression in ICU patients with CIM. Mechanical loading only marginally affected the skeletal muscle transcriptome profiling of ICU patients diagnosed with CIM.

Electronic supplementary material

The online version of this article (10.1186/s13395-019-0194-1) contains supplementary material, which is available to authorized users.

Dry Beriberi Due to Thiamine Deficiency Associated with Peripheral Neuropathy and Wernicke's Encephalopathy Mimicking Guillain-Barré syndrome: A Case Report and Review of the Literature

BACKGROUND Beriberi due to thiamine (vitamin B1) deficiency has two clinical presentations. Patients with dry beriberi present with neuropathy, and patients with wet beriberi present with heart failure, with or without neuropathy. Dry beriberi can mimic the most common form of Guillain-Barre syndrome (GBS), an acute inflammatory demyelinating polyradiculoneuropathy (AIDP). Severe thiamine deficiency results in Wernicke's encephalopathy. This report of a case of dry beriberi and Wernicke's encephalopathy due to thiamine deficiency includes a review of the literature. CASE REPORT A 56-year old woman with a history of gallstone pancreatitis and protein-calorie malnutrition was treated six months previously with total parenteral nutrition (TPN). She initially presented at another hospital with paresthesia of the lower limbs, arms, and neck, and symptoms of encephalopathy. Initial diagnosis of GBS was made, based on magnetic resonance imaging (MRI) and cerebrospinal fluid (CSF) findings. Despite five days of intravenous immunoglobulin (IVIG) treatment, her encephalopathy worsened, requiring transfer to our hospital, where she required intubation and treatment with vasopressors. A repeat MRI of her brain showed changes consistent with Wernicke's encephalopathy. Following treatment with high-dose intravenous thiamine, her mental status improved within 48 hours, and by the third hospital day, she no longer required intubation. CONCLUSIONS Symptoms and signs of dry beriberi due to thiamine deficiency can mimic those of acute or chronic GBS. However, thiamine repletion leads to rapid clinical improvement and can prevent irreversible neurologic sequelae, including Korsakoff syndrome. Clinicians should consider thiamine deficiency in malnourished patients presenting with symptoms and signs of GBS.

Intra and inter-raters reliability and agreement of stimulus electrodiagnostic tests with two different electrodes in sedated critically-ill patients

Objective: The aim of the present study was to verify the intra- and inter-rater reliability and agreement of the stimulus electrodiagnostic test (SET) measurements obtained by pen and square electrodes in the vastus lateralis and tibialis anterior muscles. Design: An intra- and inter-rater reliability and agreement study was performed for the SET by two independent raters. Two different sizes of cathode electrodes (1 cm² and 25 cm²) and two muscles were assessed (tibialis anterior and vastus lateralis). Results: Chronaxie did not change according to the different electrodes. A high intra-rater reliability (0.72 ≤ r ≤ 0.88) was detected independently of the electrode and muscle assessed. Moreover, moderate and almost perfect agreements (0.51 ≤ Kappa ≤ 1.00) were detected on intra-rater assessment. Similar correlations (0.74 ≤ r ≤ 0.79) were found for intra-rater reliability. However, dissimilar inter-rater agreement was detected: Kappa ≤ 0.40 for tibialis anterior and Kappa = 1.00 for vastus lateralis. Conclusion: The SET presented high reliability and moderate agreement in intra-rater evaluations. A fair agreement was found in the inter-rater assessment of the tibialis anterior. Evaluations performed with different electrode sizes did not influence the results. Therefore, the SET should be performed by a unique rater in test retest situations.

Muscle weakness in a S. pneumoniae sepsis mouse model

Background

The pathophysiology of intensive care unit-acquired weakness (ICU-AW), which affects peripheral nerves, limb muscles and respiratory muscles, is complex and incompletely understood. This illustrates the need for an ICU-AW animal model. However, a translatable and easily applicable ICU-AW animal model does not exist. The objective of this study was to investigate whether induction of a S. pneumoniae sepsis could serve as a model for ICU-AW.

Methods

A total of 24 C57BL/6J mice were infected intranasally with viable S. pneumoniae. Control mice (n=8) received intranasal saline and mice of the blank group (n=4) were not inoculated. Ceftriaxone was administered at 24 h (n=8) or at 48h after inoculation (n=8), or as soon as mice lost 10% of their body weight (n=8). The primary endpoint, in vivo grip strength, was measured daily. At the end of the experiment, at 120 h after inoculation, electrophysiological recordings were performed and diaphragm muscle was excised to determine ex vivo muscle fiber strength and myosin/action ratio.

Results

Grip strength over time was similar between experimental and control groups and electrophysiological recordings did not show signs of ICU-AW. Diaphragm fiber contractility measurements showed reduced strength in the group that received ceftriaxone at 48 h after S. pneumoniae inoculation.

Conclusions

Ex vivo diaphragm weakness, but no in vivo limb weakness was found in the S. pneumoniae mouse model in which severe illness was induced. This does not reflect the full clinical picture of ICU-AW as seen in humans and as such this model did not fulfill our predefined requirements. However, this model may be used to study inflammation induced diaphragmatic weakness.

Intensive Care Management of the Neuromuscular Patient

Neuromuscular emergencies are a distinct group of acute neurological diseases with distinct characteristic presentations. Patients who suffer from this group of diseases are at immediate risk of losing protection of their native airway as well as aspirating orogastric contents. This is secondary to weakness of the muscles of the oropharynx and respiratory muscles. Although some neuromuscular emergencies such as myasthenia gravis or Guillain-Barré syndrome are well understood, others such as critical illness myopathy and neuropathy are less well characterized. In this chapter, we have discussed the pathophysiology, diagnostic evaluation, and management options in patients who are admitted to the intensive care unit. We have also emphasized the importance of a thorough understanding of the use of pharmacological anesthetic agents in this patient population.

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.

Electrodiagnostic studies in the intensive care unit: A comparison study 2 decades later

INTRODUCTION

Since the late 1980s, critical illness myopathy (CIM) and critical illness polyneuropathy (CIP) have been increasingly recognized in the intensive care unit (ICU). We explored whether these causes of ICU weakness were now more likely to lead to electrodiagnostic studies (EDX) at our institution than they were 19-20 years earlier.

METHODS

We reviewed 100 consecutive ICU patients who underwent EDX from 2009 to 2015 and compared them to a previously reported study population from 1990-1995.

RESULTS

Thirty-seven (39%) had CIM, CIP, or both versus 55% in the previous study (P = 0.04). Thirty-four (36%) were diagnosed with "traditional" pre-ICU causes of weakness, such as motor neuron disease or Guillain-Barre syndrome, versus 29% in the earlier study (P = 0.3).

DISCUSSION

CIM and CIP continue to be common disorders that lead to ICU EDX, but their proportion declined compared with 19-20 years earlier, possibly due to the perceived role and selective use of EDX in the ICU. Muscle Nerve 57: 772-776, 2018.

Neuromuscular electrophysiological disorders and muscle atrophy in mechanically-ventilated traumatic brain injury patients: New insights from a prospective observational study

PURPOSE

It is unclear whether the muscular changes in mechanically-ventilated traumatic brain injury patients (TBI) are only associated with disuse or additionally to neuromuscular electrophysiological disorders (NED). The correlation between muscle atrophy and NED may affect functional outcomes and rehabilitation programs significantly.

MATERIAL AND METHODS

An observational study was performed to investigate the presence of NED and muscle atrophy in TBI patients undergoing mechanical ventilation. NED was diagnosed by the stimulus electrodiagnosis test when chronaxie was ≥1000μs. The muscle structure (thickness and echogenicity) was assessed by B-mode ultrasound. Tibialis anterior (TA), rectus femoris (RF), and biceps brachialis (BB) muscles were analyzed. Patients were followed from the first day of admission in the intensive care unit (ICU) to the fourteenth day.

RESULTS

Twenty-two patients were analyzed. An increase of 48% in NED from day 1 to day 14 was detected in TA (p=0.004). All muscles presented a significant decrease in thickness (~18%, p<0.05), but echogenicity increased only in TA (19%), p<0.01 and RF (23%), p<0.01.

CONCLUSIONS

Mechanically-ventilated patients with TBI developed NED in addition to changes in muscle structure during their stay in the ICU.

[Critical illness myopathy and polyneuropathy]

An average of 50-80% of patients treated in the intensive care unit is affected by disturbances of neuromuscular functions due to damage to the nerves and muscles, which has led to the terms critical illness polyneuropathy and myopathy. Both components occur in 30-50% of patients, while the others predominantly show a pure myopathy, while pure neuropathy is rare. Meanwhile, the descriptive term of the concept as intensive care unit-acquired weakness (ICUAW) is preferred. The most significant risk factors for the development of ICUAW are sepsis, multiorgan dysfunction and acute respiratory distress syndrome (ARDS). In at least one third of patients, persistent impairment by paralysis, sensory disturbances and balance problems persist when they leave the ICU. At approximately 10%, these leg-accentuated and highly everyday relevant disorders persist over the first year after ICU therapy. Pure myopathy rarely leads to residual disturbances, while the neuropathic component is responsible for long-term impairments.

Propofol as a Risk Factor for ICU-Acquired Weakness in Septic Patients with Acute Respiratory Failure

BACKGROUND

Critical illness polyneuropathy (CIN) and critical illness myopathy (CIM), together "ICU-Acquired weakness (ICUAW)," occur frequently in septic patients. One of the proposed mechanisms for ICUAW includes prolonged inactivation of sodium channels. Propofol, used commonly in patients with acute respiratory failure (ARF), primarily acts via enhancement of GABAergic transmission but may also increase sodium channel inactivation, suggesting a potential interaction.

METHODS

Electronic medical records and EMG reports of patients with ICUAW and a diagnosis of either sepsis, septicaemia, severe sepsis, or septic shock, concurrent with a diagnosis of acute respiratory failure (ARF), were retrospectively analyzed in a single center university hospital.

RESULTS

74 cases were identified (50.0% men, age 58±14 years), and compared to age- and sex-matched controls. Of these, 51 (69%) had CIN, 19 (26%) had CIM, and 4 (5%) had both. Propofol exposure was significantly higher in patients with ICUAW compared to controls (63.5% vs. 33.8%, p<0.001). The odds ratio of developing ICUAW with propofol exposure was 3.4 (95% CI:1.7-6.7, p<0.001). Patients with ICUAW had significantly more days in hospital (59±44 vs. 30±23) and ICU (38±26 vs. 17±13), days dependent on mechanical ventilation (27±21 vs. 13±16), and rates of tracheostomy (79.7% vs. 36.5%) and gastrostomy (75.7% vs. 25.7%) (all p<0.001). They also received a significantly higher number of distinct intravenous antibiotics, cumulative days of antibiotic therapy, and exposure to vasopressors and paralytics.

CONCLUSIONS

Propofol exposure may increase the risk of ICUAW in septic patients. An interaction through sodium channel inactivation is hypothesized.

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.

Review of Critical Illness Myopathy and Neuropathy

Critical illness myopathy (CIM) and neuropathy are underdiagnosed conditions within the intensive care setting and contribute to prolonged mechanical ventilation and ventilator wean failure and ultimately lead to significant morbidity and mortality. These conditions are often further subdivided into CIM, critical illness polyneuropathy (CIP), or the combination-critical illness polyneuromyopathy (CIPNM). In this review, we discuss the epidemiology and pathophysiology of CIM, CIP, and CIPNM, along with diagnostic considerations such as detailed clinical examination, electrophysiological studies, and histopathological review of muscle biopsy specimens. We also review current available treatments and prognosis. Increased awareness and early recognition of CIM, CIP, and CIPNM in the intensive care unit setting may lead to earlier treatments and rehabilitation, improving patient outcomes.

Safety and feasibility of a neuromuscular electrical stimulation chronaxie-based protocol in critical ill patients: A prospective observational study

PURPOSE

The aim of this study was to evaluate the safety and feasibility of a neuromuscular electrical stimulation (NMES) protocol based on neuromuscular excitability and applied in numerous muscle groups of critical ill patients.

MATERIALS AND METHODS

We performed a prospective observational study using an NMES applied daily and bilaterally into 5 muscle groups in lower limbs for 3 consecutive days. The characteristics of NMES were 90 contractions per muscle, pulse width equal to chronaxie, and a pulse frequency of 100 Hz. We assessed safety with central venous oxygen saturation, serum lactate, and creatine phosphokinase measurements. To evaluate feasibility, we recorded the time spent for the entire NMES protocol and the number of NMES sessions completed.

RESULTS

Eleven male patients finished the study. There were no significant changes observed in creatine phosphokinase from baseline up to 96 hours: 470(±270) IU/L and 455(±240) IU/L (P>.99). Central venous oxygen saturation and serum lactate had the same pattern with no significant variations (P=.23 and P=.8, respectively). The time spent during the whole procedure and the number of complete NMES sessions performed were 107±24 minutes and 84 sessions (85%), respectively.

CONCLUSIONS

We demonstrated that NMES chronaxie-based protocol is safe and feasible.

Acute Neuromuscular Respiratory Failure

PURPOSE OF REVIEW

Neurologists working in the hospital are often called to evaluate patients with severe muscle weakness. Some of these patients can develop ventilatory compromise and require admission to the intensive care unit (ICU). This article reviews the general evaluation of neuromuscular respiratory failure, discusses its differential diagnosis, and provides practical advice on the management of its most common causes.

RECENT FINDINGS

Determining the cause of acute neuromuscular respiratory failure is crucial because functional prognosis is poor in patients for whom the cause cannot be defined. The differential diagnosis is extensive, but the first step is to discriminate between cases related to a primary neurologic disease (primary neuromuscular respiratory failure) and those provoked by systemic disease, most often critical illness from sepsis and multiorgan failure (secondary neuromuscular respiratory failure). Guillain-Barré syndrome (GBS) and myasthenic crisis are the two most frequent causes of primary neuromuscular respiratory failure. Although they are both autoimmune conditions that benefit from the administration of plasma exchange or IV immunoglobulin (IVIg), they are otherwise very different disorders with unique features and distinct complications. Optimal strategies for mechanical ventilation also differ between these two conditions; while myasthenic crisis is ideally managed with noninvasive bilevel positive airway pressure (BiPAP) ventilation, GBS demands early intubation.

SUMMARY

Prompt recognition of neuromuscular respiratory failure can be lifesaving, and identification of its cause has substantial prognostic implications. Adequate management of these patients requires a multidisciplinary team with the neurologist at its center, not only to guide the diagnostic evaluation but often also to prescribe the optimal management.

ICU-Acquired Weakness: A Rehabilitation Perspective of Diagnosis, Treatment, and Functional Management

ICU-acquired weakness (ICUAW) occurs with reported incidence rates from 25% to 100%. Risk factors include immobility, sepsis, persistent systemic inflammation, multiorgan system failure, hyperglycemia, glucocorticoids, and neuromuscular blocking agents. The pathophysiology remains unknown. Clinical features may be neuropathic, myopathic, or a combination of both. Although manual muscle testing is more practical in diagnosing ICUAW, the "gold standard" for the diagnosis of ICUAW remains electromyography and nerve conduction studies. The only potential interventions known to date to prevent ICUAW include insulin therapy and early rehabilitation, but patients still may develop activity limitations in the acute care hospital. For these patients, rehabilitation may continue in long-term care hospitals, inpatient rehabilitation facilities, or skilled nursing facilities. ICUAW is a catastrophic and debilitating condition that potentially leaves patients with permanent residual activity limitations and participation restrictions. Further research on ICUAW needs to better understand its pathophysiology so that more definitive preventive and therapeutic interventions may be developed.