Electrophysiologic studies in critical illness associated weakness: myopathy or neuropathy--a reappraisal

Electrophysiological Screening to Assess Foot Drop Syndrome in Severe Acquired Brain Injury in Rehabilitative Settings

BACKGROUND

Foot drop syndrome (FDS), characterized by severe weakness and atrophy of the dorsiflexion muscles of the feet, is commonly found in patients with severe acquired brain injury (ABI). If the syndrome is unilateral, the cause is often a peroneal neuropathy (PN), due to compression of the nervous trunk on the neck of the fibula at the knee level; less frequently, the cause is a previous or concomitant lumbar radiculopathy. Bilateral syndromes are caused by polyneuropathies and myopathies. Central causes, due to brain or spinal injury, mimic this syndrome but are usually accompanied by other symptoms, such as spasticity. Critical illness polyneuropathy (CIP) and myopathy (CIM), isolated or in combination (critical illness polyneuromyopathy, CIPNM), have been shown to constitute an important cause of FDS in patients with ABI. Assessing the causes of FDS in the intensive rehabilitation unit (IRU) has several limitations, which include the complexity of the electrophysiological tests, limited availability of neurophysiology consultants, and the severe disturbance in consciousness and lack of cooperation from patients.

OBJECTIVES

We sought to propose a simplified electrophysiological screening that identifies FDS causes, particularly PN and CIPNM, to help clinicians to recognize the significant clinical predictors of poor outcomes in severe ABI at admission to IRU.

METHODS

This prospective, single-center study included 20 severe ABI patients with FDS (11 females/9 males, mean age 55.10 + 16.26; CRS-R= 11.90 + 6.32; LCF: 3.30 + 1.30; DRS: 21.45 + 3.33), with prolonged rehabilitation treatment (≥2 months). We applied direct tibialis anterior muscle stimulation (DMS) associated with peroneal nerve motor conduction evaluation, across the fibular head (NCS), to identify CIP and/or CIM and to exclude demyelinating or compressive unilateral PN.

RESULTS

At admission to IRU, simplified electrophysiological screening reported four unilateral PN, four CIP and six CIM with a CIPNM overall prevalence estimate of about 50%. After 2 months, the CIPNM group showed significantly poorer outcomes compared to other ABI patients without CIPNM, as demonstrated by the lower probability of achieving endotracheal-tube weaning (20% versus 90%) and lower CRS-R and DRS scores. Due to the subacute rehabilitation setting of our study, it was not possible to evaluate the motor results of recovery of the standing position, functional walking and balance, impaired by the presence of unilateral PN.

CONCLUSIONS

The implementation of the proposed simplified electrophysiological screening may enable the early identification of unilateral PN or CIPNM in severe ABI patients, thereby contributing to better functional prognosis in rehabilitative settings.

Muscle fiber conduction velocity in situ revisited: A new approach to an ancient technique

The aim of this study was to measure the muscle fiber conduction velocity (MFCV) in situ in the tibialis anterior muscle in healthy subjects. A total of 36 subjects matched for age and sex were studied. The MFCV was measured with a concentric needle by intramuscular monopolar needle electrical activation at a distance of 50 mm. The mean consecutive difference (MCD) of <5 μs was obtained after a median of 62 muscle fiber action potentials (MFAPs), confirming a direct muscle fiber activation. The measuring latency was at the median point of ascending depolarizing line of the MFAP. The calculated MFCV from 784 MFAPs was 4.10 ± 0.66 m/s, 3.99 ± 0.57 for female subjects (95%, 2.85 to 5.13), and 4.20 ± 0.73 for male subjects (95%, 2.74 to 5.67). The MFCV was 5.22% faster in male subjects. The calculated fast-to-slow MFCV ratio (F/S ratio) was 1.47 for female subjects (95%, 1.27 to 2.54) and 1.67 for male subjects (95%, 1.31 to 3.74). Aging significantly increased the F/S ratio. As the MFCVs mainly depend on the muscle diameter, their assessment is a quick and helpful tool for estimating it. Its variability by the F/S ratio is also a powerful tool in the follow-up of some neuromuscular disorders.

Critical illness-associated weakness and related motor disorders

Weakness of limb and respiratory muscles that occurs in the course of critical illness has become an increasingly common and serious complication of adult and pediatric intensive care unit patients and a cause of prolonged ventilatory support, morbidity, and prolonged hospitalization. Two motor disorders that occur singly or together, namely critical illness polyneuropathy and critical illness myopathy, cause weakness of limb and of breathing muscles, making it difficult to be weaned from ventilatory support, commencing rehabilitation, and extending the length of stay in the intensive care unit, with higher rates of morbidity and mortality. Recovery can take weeks or months and in severe cases, and may be incomplete or absent. Recent findings suggest an improved prognosis of critical illness myopathy compared to polyneuropathy. Prevention and treatment are therefore very important. Its management requires an integrated team approach commencing with neurologic consultation, creatine kinase (CK) measurement, detailed electrodiagnostic, respiratory and neuroimaging studies, and potentially muscle biopsy to elucidate the etiopathogenesis of the weakness in the peripheral and/or central nervous system, for which there may be a variety of causes. These tenets of care are being applied to new cases and survivors of the coronavirus-2 disease pandemic of 2019. This chapter provides an update to the understanding and approach to critical illness motor disorders.

Intensive Care Unit-acquired Neuromuscular Weakness: A Prospective Study on Incidence, Clinical Course, and Outcomes

Background

Neuromuscular weakness may manifest subsequent to critical illness in intensive care unit (ICU) patients. This weakness termed as “ICU-acquired weakness” (ICUAW) has a significant bearing on the length of mechanical ventilation, duration of ICU stays, long-term disability, and survival rate. Early identification of ICUAW helps in planning appropriate strategies, as well as in predicting the prognosis and long-term outcomes of these patients.

Aims and objectives

To identify the incidence of new-onset neuromuscular weakness developing among patients admitted in the ICU (ICUAW) and study its clinical course and impact on the duration of ICU stay.

Methods

This prospective observational study evaluated patients admitted to the ICU over a period of 1 year and 3 months (November 1, 2015, to January 31, 2017). All patients fulfilling the inclusion and exclusion criteria were evaluated with the Medical Research Council (MRC) score for muscle strength. Patients with an average score <4 were diagnosed with ICUAW. Included patients were examined on alternate days to study the clinical progression of the weakness till ICU discharge or death of the patient. The duration of ICU stay was noted.

Results and conclusion

The study revealed a significant association of ICUAW with age, Acute Physiology And Chronic Health Evaluation (APACHE II) Score, duration of mechanical ventilation, and ICU mortality. The incidence of the weakness was found to be 7.83% among the patients who survived and 50% among those patients who did not survive critical illness.

How to cite this article

Baby S, George C, Osahan NM. Intensive Care Unit-acquired Neuromuscular Weakness: A Prospective Study on Incidence, Clinical Course, and Outcomes. Indian J Crit Care Med 2021;25(9):1006–1012.

Critical illness neuropathy in severe COVID-19: a case series

INTRODUCTION

Neurological complications of SARS-CoV-2 disease have received growing attention, but only few studies have described to date clinical and neurophysiological findings in COVID patients during their stay in intensive care units (ICUs). Here, we neurophysiologically assessed the presence of either critical illness neuropathy (CIP) or myopathy (CIM) in ICU patients.

MATERIALS AND METHODS

Patients underwent a neurophysiological assessment, including bilateral examination of the median, ulnar, deep peroneal and tibial motor nerves and of the median, ulnar, radial and sural sensory nerves. Needle electromyography (EMG) was performed for both distal and proximal muscles of the lower and upper limbs. In order to differentiate CIP from CIM, Direct Muscle Stimulation (DMS) was applied either to the deltoid or tibialis anterior muscles. Peak to peak amplitudes and onset latencies of the responses evoked by DMS (DMS_amp, DMS_lat) or by motor nerve stimulation (MNS_amp, MNS_lat) were compared. The ratio MNS_amp to DMS_amp (NMR) and the MNS_lat to DMS_lat difference (NMD: MNS_lat - DMS_lat) were also evaluated.

RESULTS

Nerve conduction studies showed a sensory-motor polyneuropathy with axonal neurogenic pattern, as confirmed by needle EMG. Both MNS_amp and NMR were significantly reduced when compared to controls (p < 0.0001), whereas MNS_lat and NMD were markedly increased (p = 0.0049).

CONCLUSIONS

We have described COVID patients in the ICU with critical illness neuropathy (CIP). COVID-related CIP could have implications for the functional recovery and rehabilitation strategies.

Early detection of evolving critical illness myopathy with muscle velocity recovery cycles

OBJECTIVE

To investigate the sensitivity of muscle velocity recovery cycles (MVRCs) for detecting altered membrane properties in critically ill patients, and to compare this to conventional nerve conduction studies (NCS) and quantitative electromyography (qEMG).

METHODS

Twenty-four patients with intensive care unit acquired weakness (ICUAW) and 34 healthy subjects were prospectively recruited. In addition to NCS (median, ulnar, peroneal, tibial and sural nerves) and qEMG (biceps brachii, vastus medialis and anterior tibial muscles), MVRCs with frequency ramp were recorded from anterior tibial muscle.

RESULTS

MVRC and frequency ramp parameters showed abnormal muscle fiber membrane properties with up to 100% sensitivity and specificity. qEMG showed myopathy in 15 patients (63%) while polyneuropathy was seen in 3 (13%). Decreased compound muscle action potential (CMAP) amplitude (up to 58%) and absent F-waves (up to 75%) were frequent, but long duration CMAPs were only seen in one patient with severe myopathy.

CONCLUSIONS

Altered muscle fiber membrane properties can be detected in patients with ICUAW not yet fulfilling diagnostic criteria for critical illness myopathy (CIM). MVRCs may therefore serve as a tool for early detection of evolving CIM.

SIGNIFICANCE

CIM is often under-recognized by intensivists, and large-scale longitudinal studies are needed to determine its incidence and pathogenesis.

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.

Focal brain ischemia in mice does not cause electrophysiological signs of critical illness neuropathy

OBJECTIVE

Critical illness polyneuropathy (CIP) is a common complication of severe systemic illness treated in intensive care medicine. Ischemic stroke leads to an acute critical injury of the brain with hemiparesis, immunosuppression and subsequent infections, all of which require extended medical treatment. Stroke-induced sarcopenia further contributes to poor rehabilitation and is characterized by muscle wasting and denervation in the paralytic, but also the unaffected limbs. Therefore, we asked whether stroke leads to an additional CIP-like neurodegeneration.

RESULTS

Focal brain ischemia was induced in adult mice by 60-min middle cerebral artery occlusion (MCAo) following reperfusion and led to functional deficits and marked hemispheric brain atrophy. Nerve conduction function and muscle potentials were measured in the ipsilateral sciatic nerve and gastrocnemius and quadriceps muscle with electroneurography/-myography on days 10, 22, 44 after stroke. An additional crush-injury to the sciatic nerve was included in two sham mice as positive control (sham +). We found no differences in nerve conduction function nor spontaneous electromyographic activity between MCAo and sham animals. Sham + mice developed marked reduction of the motor action potential amplitudes and conduction velocities with pathologic spontaneous activity. In conclusion, we found no peripheral nerve dysfunction/degeneration as signs of a CIP-like phenotype after MCAo.

Critical illness myopathy after COVID-19

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Muscle weakness after COVID-19 can be caused by critical illness myopathy.

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Critical illness myopathy should be suspected in patients with long ICU stay.

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Health systems must plan access to rehabilitative facilities after COVID-19.

This paper describes a patient who developed diffuse and symmetrical muscle weakness after a long stay in the intensive care unit (ICU) due to coronavirus disease 2019 (COVID-19). The patient underwent a neurophysiological protocol, including nerve conduction studies, concentric needle electromyography (EMG) of the proximal and distal muscles, and direct muscle stimulation (DMS). Nerve conduction studies showed normal sensory conduction and low-amplitude compound muscle action potentials (CMAPs). EMG revealed signs of myopathy, which were more pronounced in the lower limbs. The post-DMS CMAP was absent in the quadriceps and of reduced amplitude in the tibialis anterior muscle. Based on these clinical and neurophysiological findings, a diagnosis of critical illness myopathy was made according to the current diagnostic criteria. Given the large number of patients with COVID-19 who require long ICU stays, many are very likely to develop ICU-acquired weakness, as did the patient described here. Health systems must plan to provide adequate access to rehabilitative facilities for both pulmonary and motor rehabilitative treatment after COVID-19.

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.

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

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

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.

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.

[Critical illness polyneuropathy and myopathy as neurological complications of sepsis]

Intensive care unit acquired weakness (ICUAW) is a frequent and severe complication of intensive care management. Within ICUAW critical illness polyneuropathy (CIP) and myopathy (CIM) can be differentiated. The major symptom of ICUAW is progressive quadriparesis, which makes weaning from the respirator more difficult, can appear early after admission to an ICU and can often be detected several months after discharge from the ICU. The pathophysiology of ICUAW is multifactorial and complex. Potential therapeutic approaches are the early and sufficient therapy of mulitorgan dysfunction, optimal control of glucose levels as well as early and intensive physiotherapy. This review article discusses the data on incidence, pathophysiology, diagnostic approaches and prognosis of ICUAW.

Functional Status in ICU Survivors and Out of Hospital Outcomes: A Cohort Study

OBJECTIVES

Functional status at hospital discharge may be a risk factor for adverse events among survivors of critical illness. We sought to examine the association between functional status at hospital discharge in survivors of critical care and risk of 90-day all-cause mortality after hospital discharge.

DESIGN

Single-center retrospective cohort study.

SETTING

Academic Medical Center.

PATIENTS

Ten thousand three hundred forty-three adults who received critical care from 1997 to 2011 and survived hospitalization.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The exposure of interest was functional status determined at hospital discharge by a licensed physical therapist and rated based on qualitative categories adapted from the Functional Independence Measure. The main outcome was 90-day post hospital discharge all-cause mortality. A categorical risk-prediction score was derived and validated based on a logistic regression model of the function grades for each assessment. In an adjusted logistic regression model, the lowest quartile of functional status at hospital discharge was associated with an increased odds of 90-day postdischarge mortality compared with patients with independent functional status (odds ratio, 7.63 [95% CI, 3.83-15.22; p < 0.001]). In patients who had at least 7 days of physical therapy treatment prior to hospital discharge (n = 2,293), the adjusted odds of 90-day postdischarge mortality in patients with marked improvement in functional status at discharge was 64% less than patients with no change in functional status (odds ratio, 0.36 [95% CI, 0.24-0.53]; p < 0.001).

CONCLUSIONS

Lower functional status at hospital discharge in survivors of critical illness is associated with increased postdischarge mortality. Furthermore, patients whose functional status improves before discharge have decreased odds of postdischarge mortality.

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.

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.

Critical Illness Neuromyopathy Complicating Akinetic Crisis in Parkinsonism: Report of 3 Cases

Akinetic crisis (AC) is a life-threatening complication of parkinsonism characterized by an acute severe akinetic-hypertonic state, consciousness disturbance, hyperthermia, and muscle enzymes elevation. Injectable dopaminomimetic drugs, high-dose methylprednisolone, and dantrolene are advocated as putative specific treatments. The course of the illness is frequently complicated by infections, pulmonary embolism, renal failure, disseminated intravascular coagulation, and cardiac arrhythmias. Critical illness neuromyopathy (CINM) is an acquired neuromuscular disorder characterized by flaccid quadriparesis and muscle enzyme elevation, often occurring in intensive care units and primarily associated with inactivity, sepsis, multiorgan failure, neuromuscular blocking agents, and steroid treatment. In 3 parkinsonian patients, during the course of AC we observed disappearance of rigidity but persistent hypoactivity. In all, neurological examination showed quadriparesis with loss of tendon reflexes and laboratory investigation disclosed a second peak of muscle enzymes elevation, following the first increment due to AC. Electrophysiological studies showed absent or reduced sensory nerve action potentials and compound muscular action potentials, myopathic changes, and fibrillation potentials at electromyography recordings, and reduced excitability or inexcitability of tibialis anterior at direct muscle stimulation, leading to a diagnosis of CINM in all 3 patients. In 1 patient, the diagnosis was also confirmed by muscle biopsy. Outcome was fatal in 2 of the 3 patients. Although AC is associated with most of the known risk factors for CINM, the cooccurrence of the 2 disorders may be difficult to recognize and has never been reported. We found that CINM can occur as a severe complication of AC, and should be suspected when hypertonia-rigidity subsides despite persistent akinesia. Strict monitoring of muscle enzyme levels may help diagnosis. This finding addresses possible caveats in the use of putative treatments for AC.

Modulation of the muscle and nerve compound muscle action potential by evoked pain

Background and aims To our knowledge there are no studies that have examined the effects of the experimental pain on muscle fibre excitability as measured by the amplitudes of the potentials evoked by direct muscle stimulation (DMS) in a muscle at rest. We hypothesized that evoked pain can modulate the muscle compound action potential (CMAP) obtained by DMS possibly due to changes in muscle fibre excitability. Methods Pain was evoked by intramuscular infusion of hypertonic saline in 50 men. Ten control subjects were infused with isotonic saline. The infusions were given distal to the motor end plate region of the dominant brachial biceps muscle (BBM) in a double-blind manner. The nerve CMAP was obtained by stimulating the musculocutaneous nerve and recording from the BBM using surface-electrodes. Muscle CMAPs were obtained by direct muscle stimulation with subdermal electrodes placed subcutaneously in the distal third of the muscle. A stimuli-response curve of the amplitudes from muscle CMAP was obtained by stimulating from 10 to 90 mA. Results There was a decrease of the nerve CMAP amplitudes after infusion of isotonic saline (from 13.78mV to 12.16 mV), p-value 0.0007 and of hypertonic saline (from 13.35 mV to 10.85 mV), p-value 0.0000. The percent decrease from before to after infusion was larger in the hypertonic saline group (19.37%) compared to the isotonic saline group (12.18%), p-value 0.025. There was a decrease of the amplitudes of the muscle CMAP after infusion of both isotonic (at 90 mA from 13.84mV to 10.32 mV, p value 0.001) and of hypertonic saline (at 90 mA from 14.01 mV to 8.19 mV, p value 0.000). The percent decrease was larger in the hypertonic saline group compared to the isotonic saline group for all the stimulations intensities. At 90 mA we saw a 42% decrease in the hypertonic saline group and 24.5% in the isotonic saline group, p value 0.005. There were no changes in conduction velocity. Conclusion We found a larger amplitude decrease of the muscle and nerve potentials following hypertonic saline infusion compared with that of isotonic saline. We suggest that this deferential outcome of hypertonic saline on muscle CMAP may be linked to the nociceptive effect on muscle fibre membrane excitability. Implications The study supplies with some evidence of the peripheral effect of muscle pain. However, further trials with other nociceptive substances such as capsaicin should be performed.

[Intensive care unit acquired weakness. Pathogenesis, treatment, rehabilitation and outcome]

The diagnosis of intensive care unit acquired weakness (ICUAW) in the setting of neurological rehabilitation is steadily increasing. This is due to the fact that the intensive care of patients with sepsis or after cardiac or abdominal surgery is improving. A longer duration of respiratory weaning and comorbidities frequently complicate rehabilitation. Clinically, patients present with a flaccid (tetra) paresis and electrophysiological studies have shown axonal damage. Besides involvement of peripheral nerves, muscle can also be affected (critical illness myopathy) leading to ICUAW with inconstant myopathic damage patterns found by electrophysiological testing. Mixed forms can also be found. A specific therapy for ICUAW is not available. Early mobilization to be initiated on the intensive care unit and commencing neurological rehabilitation improve the outcome of ICUAW. This review highlights the current literature regarding the etiology and diagnosis of ICUAW. Furthermore, studies about rehabilitation and outcome of ICUAW are discussed.

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.

Neuromuscular complications of critical illness

Patients admitted to intensive care units (ICUs) suffer from a wide range of neurological disorders. Some develop within the ICU rendering weakness and difficulty in weaning patients from ventilator support. ICUAW, or ICU acquired weakness, is a broad term that includes several more specific neuromuscular problems. After exclusion of other causes of weakness, ICUAW includes critical illness polyneuropathy (CIP), first described by Charles Bolton, critical illness myopathy (CIM), and disorders of neuromuscular junction transmission. This chapter reviews the clinical, electrophysiological, and pathological features of these conditions and provides clinicians with approaches toward diagnosing and investigating ICUAW.

Neuromuscular complications in intensive care patients

Increased survival of critically ill patients has focused the attention on secondary complications of intensive care unit (ICU) stay, mainly ICU-acquired weakness (ICUAW). ICUAW is relatively common with significant impact on recovery. Prolonging mechanical ventilation and overall hospitalization time, increased mortality, and persistent disability are the main problems associated with ICUAW. The chapter deals mainly with the differential diagnosis of neuromuscular generalized weakness that develops in the ICU, but focal ICUAW is reviewed too. The approach to the diagnosis and the yield of various techniques (mainly electrophysiological and histological) is discussed. Possible therapeutic interventions of this condition that modify the course of this deleterious situation and lead to better rehabilitation are discussed. The current postulated mechanisms associated with ICUAW (mainly the more frequent critical illness neuropathy and myopathy) are reviewed.

The beneficial effects of levetiracetam on polyneuropathy in the early stage of sepsis in rats: electrophysiological and biochemical evidence

ABSTRACT Critical illness polyneuropathy (CIP) is a common complication in long (≥1 week) critical/intensive care hospitalizations. Rapidly progressing atrophy and weakness of the limb, trunk and, particularly, respiratory muscles may lead to severe morbidity or mortality. The aim of the present study was to investigate the protective effects of levetiracetam (LEV) on CIP in the early stage of sepsis in rats. We simulated CIP by a surgically induced sepsis model and verified it by lower-limb electromyography (EMG) (amplitude and duration of CMAP, and distal latency). We evaluated the effects of various doses of LEV treatment (300, 600, and 1200 mg/kg i.p.) on CIP by performing electrophysiology, and determining plasma tumor necrosis factor (TNF)-α, lipid peroxides (malondialdehyde, MDA) levels, and total antioxidant capacity (TAC). Our data showed: (1) significant suppression of CMAP amplitude and prolongation of distal latency in the saline-treated sepsis group, and distal latency as well as CMAP amplitudes benefiting best from the 600 mg/kg LEV treatment; (2) significant rise in plasma TNF-α and MDA levels in the saline-treated sepsis group, but significant ameliorations by the 600 and 1200 mg/kg LEV treatment; (3) highly significant suppression of TAC in the saline-treated group, but profound reversals in all LEV-treated groups. We conclude that 300, 600, and 1200 mg/kg i.p. doses of post-septic treatment by LEV has possibly acted in a dose-dependent manner to both protect and restore the affected peripheral nerves' axon and myelin following surgical disturbance of the cecum to induce sepsis and consequent polyneuropathy.

[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.

Electrophysiology of neuromuscular disorders in critical illness

INTRODUCTION

Neuromuscular disorders, predominantly critical illness myopathy (CIM) and critical illness polyneuropathy (CIP) occur in approximately one-third of patients in intensive care units. The aim of this study was to review the important role of electrophysiology in this setting.

RESULTS

In CIM, sarcolemmal inexcitability causes low amplitude compound muscle action potentials (CMAPs) that may have prolonged durations. Needle electrode examination usually reveals early recruitment of short duration motor unit potentials, often with fibrillation potentials. In CIP, the findings are usually those of a generalized axonal sensorimotor polyneuropathy. Direct muscle stimulation aids in differentiating CIP and CIM and in identifying mixed disorders along with other electrodiagnostic and histopathologic studies. Identifying evolving reductions in fibular CMAP amplitudes in intensive care unit (ICU) patients predicts development of neuromuscular weakness.

CONCLUSIONS

Knowledge of the various neuromuscular disorders in critically ill patients, their risk factors, and associated electrodiagnostic findings can lead to development of a rational approach to diagnosis of the cause of neuromuscular weakness in ICU patients.

Interval neurophysiological changes in non septic critically ill mechanically ventilated patients

Peripheral nerve changes in critically ill patients are common, sepsis being the most important risk factor. The aim of our study is to investigate interval neurophysiological changes in non septic mechanically ventilated critically ill patients, a group who has not been the focus of previous studies. Consecutive non septic mechanically ventilated critically ill patients were included. Baseline nerve conduction studies (NCS) were done within 3 days of intensive care unit admission, and 48 hours after the initiation of mechanical ventilation, and were followed up 7-8 days later. Sural and ulnar sensory, and median and peroneal motor nerves were tested. Nine patients were studied, five (56%) showed significant changes in their NCS compared to baseline. The peroneal and sural nerve amplitudes significantly dropped in all of the five affected patients, with drop of those of the median motor nerves in two, and ulnar sensory nerves in three patients. In conclusion, interval changes in peripheral nerves can exist in critically ill mechanically ventilated non septic patients. The pattern is similar to critically ill patients with sepsis. Theories of possible pathophysiology of critical illness neuropathy should not merely depend on the presence of sepsis as a trigger and other mechanisms should be investigated.

Neurophysiological approach to disorders of peripheral nerve

Disorders of the peripheral nerve system (PNS) are heterogeneous and may involve motor fibers, sensory fibers, small myelinated and unmyelinated fibers and autonomic nerve fibers, with variable anatomical distribution (single nerves, several different nerves, symmetrical affection of all nerves, plexus, or root lesions). Furthermore pathological processes may result in either demyelination, axonal degeneration or both. In order to reach an exact diagnosis of any neuropathy electrophysiological studies are crucial to obtain information about these variables. Conventional electrophysiological methods including nerve conduction studies and electromyography used in the study of patients suspected of having a neuropathy and the significance of the findings are discussed in detail and more novel and experimental methods are mentioned. Diagnostic considerations are based on a flow chart classifying neuropathies into eight categories based on mode of onset, distribution, and electrophysiological findings, and the electrophysiological characteristics in each type of neuropathy are discussed.

Early type II fiber atrophy in intensive care unit patients with nonexcitable muscle membrane

OBJECTIVE

Intensive care unit-acquired weakness indicates increased morbidity and mortality. Nonexcitable muscle membrane after direct muscle stimulation develops early and predicts intensive care unit-acquired weakness in sedated, mechanically ventilated patients. A comparison of muscle histology at an early stage in intensive care unit-acquired weakness has not been done. We investigated whether nonexcitable muscle membrane indicates fast-twitch myofiber atrophy during the early course of critical illness.

DESIGN

Prospective observational study.

SETTING

Two intensive care units at Charité University Medicine, Berlin.

PATIENTS

Patients at increased risk for development of intensive care unit-acquired weakness, indicated by Sepsis-related Organ Failure Assessment scores ≥8 on 3 of 5 consecutive days within their first week in the intensive care unit.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Electrophysiological compound muscle action potentials after direct muscle stimulation and muscle biopsies were obtained at median days 7 and 5, respectively. Patients with nonexcitable muscle membranes (n = 15) showed smaller median type II cross-sectional areas (p < .05), whereas type I muscle fibers did not compared with patients with preserved muscle membrane excitability (compound muscle action potentials after direct muscle stimulation ≥3.0 mV; n = 9). We also observed decreased mRNA transcription levels of myosin heavy chain isoform IIa and a lower densitometric ratio of fast-to-slow myosin heavy chain protein content.

CONCLUSION

We suggest that electrophysiological nonexcitable muscle membrane predicts preferential type II fiber atrophy in intensive care unit patients during early critical illness.

[Intensive care unit-acquired weakness in the critically ill : critical illness polyneuropathy and critical illness myopathy]

Intensive care unit-acquired weakness (ICUAW) is a severe complication in critically ill patients which has been increasingly recognized over the last two decades. By definition ICUAW is caused by distinct neuromuscular disorders, namely critical illness polyneuropathy (CIP) and critical illness myopathy (CIM). Both CIP and CIM can affect limb and respiratory muscles and thus complicate weaning from a ventilator, increase the length of stay in the intensive care unit and delay mobilization and physical rehabilitation. It is controversially discussed whether CIP and CIM are distinct entities or whether they just represent different organ manifestations with common pathomechanisms. These basic pathomechanisms, however, are complex and still not completely understood but metabolic, inflammatory and bioenergetic alterations seem to play a crucial role. In this respect several risk factors have recently been revealed: in addition to the administration of glucocorticoids and non-depolarizing muscle relaxants, sepsis and multi-organ failure per se as well as elevated levels of blood glucose and muscular immobilization have been shown to have a profound impact on the occurrence of CIP and CIM. For the diagnosis, careful physical and neurological examinations, electrophysiological testing and in rare cases nerve and muscle biopsies are recommended. Nevertheless, it appears to be difficult to clearly distinguish between CIM and CIP in a clinical setting. At present no specific therapy for these neuromuscular disorders has been established but recent data suggest that in addition to avoidance of risk factors early active mobilization of critically ill patients may be beneficial.

Critical illness polyneuropathy and myopathy: a major cause of muscle weakness and paralysis

Critical illness polyneuropathy (CIP) and myopathy (CIM) are complications of critical illness that present with muscle weakness and failure to wean from the ventilator. In addition to prolonging mechanical ventilation and hospitalisation, CIP and CIM increase hospital mortality in patients who are critically ill and cause chronic disability in survivors of critical illness. Structural changes associated with CIP and CIM include axonal nerve degeneration, muscle myosin loss, and muscle necrosis. Functional changes can cause electrical inexcitability of nerves and muscles with reversible muscle weakness. Microvascular changes and cytopathic hypoxia might disrupt energy supply and use. An acquired sodium channelopathy causing reduced muscle membrane and nerve excitability is a possible unifying mechanism underlying CIP and CIM. The diagnosis of CIP, CIM, or combined CIP and CIM relies on clinical, electrophysiological, and muscle biopsy investigations. Control of hyperglycaemia might reduce the severity of these complications of critical illness, and early rehabilitation in the intensive care unit might improve the functional recovery and independence of patients.

The interobserver agreement of handheld dynamometry for muscle strength assessment in critically ill patients

OBJECTIVE

Muscle weakness often complicates critical illness and is associated with increased risk of morbidity, mortality, and limiting functional outcome even years later. To assess the presence of muscle weakness and to examine the effects of interventions, objective and reliable muscle strength measurements are required. The first objective of this study is to determine interobserver reliability of handheld dynamometry. Secondary objectives are to quantify muscle weakness, to evaluate distribution of muscle weakness, and to evaluate gender-related differences in muscle strength.

DESIGN

Cross-sectional observational study.

SETTING

The surgical and medical intensive care units of a large, tertiary referral, university hospital.

PATIENTS

A cross-sectional, randomly selected sample of awake and cooperative critically ill patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Handheld dynamometry was performed in critically ill patients who had at least a score of 3 (movement against gravity) on the Medical Research Council scale. Three upper limb and three lower limb muscle groups were tested at the right-hand side. Patients were tested twice daily by two independent raters. Fifty-one test-retests were performed in 39 critically ill patients. Handheld dynamometry demonstrated good interobserver agreement with intraclass correlation coefficients >0.90 in four of the muscle groups tested (range, 0.91-0.96) and somewhat less for hip flexion (intraclass correlation coefficient, 0.80) and ankle dorsiflexion (intraclass correlation coefficient, 0.76). Limb muscle strength was considerably reduced in all muscle groups as shown by the median z-score (range, -1.08 to -3.48 sd units). Elbow flexors, knee extensors, and ankle dorsiflexors were the most affected muscle groups. Loss of muscle strength was comparable between men and women.

CONCLUSIONS

Handheld dynamometry is a tool with a very good interobserver reliability to assess limb muscle strength in awake and cooperative critically ill patients. Future studies should focus on the sensitivity of handheld dynamometry in longitudinal studies to evaluate predictive values toward patients' functional outcome.

[Critical illness myopathy and neuropathy (CRIMYN). Electroneurographic classification]

BACKGROUND

Critical Illness Myopathy and Neuropathy (CRIMYN) frequently coexist with severe sepsis and is associated with prolonged weaning from mechanical ventilation and prolonged ICU length of stay. We aimed to classify different levels as well as patterns of impairment with regard to electrophysiological disturbances in CRIMYN patients by cluster analysis.

METHODS

A total of 30 patients with sepsis/SIRS were studied prospectively. Motor and sensory conduction studies were performed from six motor and four sensory nerves on a weekly basis from admission until discharge and finally after 6 months. A control group of 63 healthy persons was examined simultaneously using the same criteria. Different patterns of electrophysiological disturbances were classified by cluster analysis based on differences to reference values of 20 parameters, compound muscle action potential (CMAP), sensory nerve action potential (SNAP) and motor and sensor conduction velocity (NCV).

RESULTS

Four different clusters were identified: cluster 1 showing normal values for CMAP, SNAP and NCV in all nerves (3 patients and all test persons), cluster 2 showing pathological values for CMAP in the lower extremities and the other parameters were normal (5 patients), cluster 3 showing moderately pathological values for CMAP, SNAP and sensory NCV in upper and lower extremities and motor NCV in lower extremities (12 patients) and cluster 4 showing severe disturbances of CMAP, SNAP and NCV in upper and lower extremities (10 patients).

CONCLUSION

A total of four different clusters of electrophysiological impairment can be identified in patients with sepsis/SIRS, which enables further differentiation of the severity of neuromuscular disturbances in sepsis-associated organ failure. This might be useful as a prognostic parameter and can be correlated with additional clinical and paraclinical parameters related to sepsis.

Tumor necrosis factor-α downregulates sodium current in skeletal muscle by protein kinase C activation: involvement in critical illness polyneuromyopathy

Sepsis is involved in the decrease of membrane excitability of skeletal muscle, leading to polyneuromyopathy. This effect is mediated by alterations of the properties of voltage-gated sodium channels (Na(V)), but the exact mechanism is still unknown. The aim of the present study was to check whether tumor necrosis factor (TNF-α), a cytokine released during sepsis, exerts a rapid effect on Na(V). Sodium current (I(Na)) was recorded by macropatch clamp in skeletal muscle fibers isolated from rat peroneus longus muscle, in control conditions and after TNF-α addition. Analyses of dose-effect and time-effect relationships were carried out. Effect of chelerythrine, a PKC inhibitor, was also studied to determine the way of action of TNF-α. TNF-α induced a reversible dose- and time-dependent inhibition of I(Na). A maximum inhibition of 75% of the control current was observed. A shift toward more negative potentials of activation and inactivation curves of I(Na) was also noticed. These effects were prevented by chelerythrine pretreatment. TNF-α is a cytokine released in the early stages of sepsis. Besides a possible transcriptional role, i.e., modification of the channel type and/or number, we demonstrated the existence of a rapid, posttranscriptional inhibition of Na(V) by TNF-α. The downregulation of the sodium current could be mediated by a PKC-induced phosphorylation of the sodium channel, thus leading to a significant decrease in muscle excitability.

Facial nerve involvement in critical illness polyneuropathy

Although ICU-acquired neuromuscular weakness is a well-known problem, critical illness neuropathy is an under-diagnosed entity in critically ill patients. Facial musculature is typically not involved in critical illness neuropathy. This report highlights an unusual presentation of critical illness polyneuropathy in a patient with involvement of facial musculature.

Diagnosis and management of critical illness polyneuropathy and critical illness myopathy

Newly acquired neuromuscular weakness commonly develops in the setting of critical illness. This weakness delays recovery and often causes prolonged ventilator dependence. An axonal sensory-motor polyneuropathy, critical illness polyneuropathy (CIP), is seen in up to a third of critically ill patients with the systemic inflammatory response syndrome (usually due to sepsis). As frequently, or more so, an acute myopathy, critical illness myopathy (CIM), develops in a similar setting, often in association with the use of corticosteroids and/or nondepolarizing neuromuscular-blocking agents. This paper reviews the clinical features, diagnostic approach, and treatment of CIP and CIM. There are no specific pharmacologic treatments for CIP or CIM, but recognizing the presence of one of these disorders often improves management. Prevention of CIP and CIM is feasible in part by avoiding risk factors and by aggressive medical management of critically ill patients. Intensive insulin therapy in intensive care unit patients appears to reduce the likelihood of developing CIP and/or CIM. Future treatments of sepsis may further reduce the incidence of these neuromuscular consequences of critical illness.

Neuromuscular disorders in critically ill patients: review and update

Neuromuscular disorders that are diagnosed in the intensive care unit (ICU) usually cause substantial limb weakness and contribute to ventilatory dysfunction. Although some lead to ICU admission, ICU-acquired disorders, mainly critical illness myopathy (CIM) and critical illness polyneuropathy (CIP), are more frequent and are associated with considerable morbidity. Approximately 25% to 45% of patients admitted to the ICU develop CIM, CIP, or both. Their clinical features often overlap; therefore, nerve conduction studies and electromyography are particularly helpful diagnostically, and more sophisticated electrodiagnostic studies and histopathologic evaluation are required in some circumstances. A number of prospective studies have identified risk factors for CIP and CIM, but their limitations often include the inability to separate CIM from CIP. Animal models reveal evidence of a channelopathy in both CIM and CIP, and human studies also identified axonal degeneration in CIP and myosin loss in CIM. Outcomes are variable. They tend to be better with CIM, and some patients have longstanding disabilities. Future studies of well-characterized patients with CIP and CIM should refine our understanding of risk factors, outcomes, and pathogenic mechanisms, leading to better interventions.

Long-term functional outcome and health status of patients with critical illness polyneuromyopathy

OBJECTIVE

The aim of this study was to investigate the long-term functional outcome and health status of patients with critical illness polyneuromyopathy (CIPNM).

METHOD AND SUBJECTS

One hundred and twenty-four consecutive survival intensive care unit patients admitted to a neuro-rehabilitation Unit from January 2003 to December 2007 were identified. Patients with proven CIPNM by the electromyography were prospectively followed. The Barthel and modified Rankin Scales (mRS) were administered to all patients at baseline, discharge and follow-up. The SF-36 questionnaire was administered to ascertain health status. Each patient underwent an individually tailored rehabilitation therapy.

RESULTS

Forty-two subjects (23M, 19F, mean age 58.4 ± 13.9) were enrolled. Of these, 30 patients were diagnosed electrophysiologically with CIP, six with critical illness myopathy (CIM) and six with a finding combination of CIP and CIM (CIP/CIM) subtype. The mean Barthel scores at baseline, discharge and follow-up were 16.7 ± 8.6, 81.7 ± 16.4 and 86.7 ± 15.9 (P < 0.001) and the median mRS scores were 5 (IQR: 5-5), 3 (IQR: 0-5) and 1 (IQR: 0-5). The mean length of neuro-rehabilitation stay was 76.2 ± 28.1 days. The SF-36 questionnaire administered at follow-up (mean 31.7 ± 15.8 months), showed significantly lower values compared to Italian normative.

CONCLUSION

ICU patients with CIPNM treated in a neuro-rehabilitation setting resulted in a good functional outcome. Despite complete recovery, patients with CIPNM experienced difficulties in health status.

Management of critical illness polyneuropathy and myopathy

A syndrome of generalized weakness, areflexia, and difficulty with weaning from a ventilator is a common clinical presentation in the critically ill patient, especially in the setting of sepsis, multiorgan failure, and hyperglycemia. At first believed to be a manifestation of nerve (critical illness neuropathy, CIN) or muscle (critical illness myopathy, CIM) dysfunction, our current conceptualization is as a spectrum (critical illness neuromuscular abnormalities, CINMA) that varies in extent and site(s) of involvement, but often a similar clinical presentation. Signs and symptoms of CINMA must be identified early to foster recovery and limit morbidity and mortality. The medical history is crucial in excluding preexisting neuromuscular conditions and electrodiagnostic testing helps to establish the diagnosis and prognostication. A stepwise approach to the management of a patient with CINMA is outlined, but avoiding potential medications, and ensuring supportive care are the primary interventions to consider. Recently intensive insulin therapy for hyperglycemia has been shown to lower the risk of CINMA and decrease the time of ventilatory support, but with a greater risk of hypoglycemia. Future therapeutic interventions will require a better understanding of disease pathogenesis, but may target proinflammatory cytokine and free-radical pathways, muscle gene expression, ion channel function, or proteolytic muscle protein mechanisms. Rehabilitation is an equally essential component in a patient's management. Although prognosis depends on the extent of the underlying muscle and nerve damage, mild persistent deficits are common and severe disability may be persistent.

Risk factors in critical illness myopathy during the early course of critical illness: a prospective observational study

INTRODUCTION

Non-excitable muscle membrane indicates critical illness myopathy (CIM) during early critical illness. We investigated predisposing risk factors for non-excitable muscle membrane at onset of critical illness.

METHODS

We performed sequential measurements of muscle membrane excitability after direct muscle stimulation (dmCMAP) in 40 intensive care unit (ICU) patients selected upon a simplified acute physiology (SAPS-II) score >OR= 20 on 3 successive days within 1 week after ICU admission. We then investigated predisposing risk factors, including the insulin-like growth factor (IGF)-system, inflammatory, metabolic and hemodynamic parameters, as well as suspected medical treatment prior to first occurrence of abnormal dmCMAP. Nonparametric analysis of two-factorial longitudinal data and multivariate analysis were used for statistical analysis.

RESULTS

22 patients showed abnormal muscle membrane excitability during direct muscle stimulation within 7 (5 to 9.25) days after ICU admission. Significant risk factors for the development of impaired muscle membrane excitability in univariate analysis included inflammation, disease severity, catecholamine and sedation requirements, as well as IGF binding protein-1 (IGFBP-I), but did not include either adjunctive hydrocortisone treatment in septic shock, nor administration of neuromuscular blocking agents or aminoglycosides. In multivariate Cox regression analysis, interleukin-6 remained the significant risk factor for the development of impaired muscle membrane excitability (HR 1.006, 95%-CI (1.002 to 1.011), P = 0.002).

CONCLUSIONS

Systemic inflammation during early critical illness was found to be the main risk factor for development of CIM during early critical illness. Inflammation-induced impairment of growth-factor mediated insulin sensitivity may be involved in the development of CIM.

Critical illness polyneuropathy and myopathy in the intensive care unit

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

Sepsis-induced myopathy

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