Sepsis and catecholamine support are the major risk factors for critical illness polyneuropathy after open heart surgery'

Anabolic Strategies for ICU-Acquired Weakness. What Can We Learn from Bodybuilders?

The study aimed to show the potential clinical application of supplements used among sportsmen for patients suffering from Intensive Care Unit-acquired Weakness (ICUAW) treatment. ICUAW is a common complication affecting approximately 40% of critically ill patients, often leading to long-term functional disability. ICUAW comprises critical illness polyneuropathy, critical illness myopathy, or a combination of both, such as critical illness polyneuromyopathy. Muscle degeneration begins shortly after the initiation of mechanical ventilation and persists post-ICU discharge until proteolysis and autophagy processes normalize. Several factors, including prolonged bedrest and muscle electrical silencing, contribute to muscle weakness, resulting from an imbalance between protein degradation and synthesis. ICUAW is associated with tissue hypoxia, oxidative stress, insulin resistance, reduced glucose uptake, lower adenosine triphosphate (ATP) formation, mitochondrial dysfunction, and increased free-radical production. Several well-studied dietary supplements and pharmaceuticals commonly used by athletes are proven to prevent the aforementioned mechanisms or aid in muscle building, regeneration, and maintenance. While there is no standardized treatment to prevent the occurrence of ICUAW, nutritional interventions have demonstrated the potential for its mitigation. The use of ergogenic substances, popular among muscle-building sociates, may offer potential benefits in preventing muscle loss and aiding recovery based on their work mechanisms.

Impact of Vasoactive Medications on ICU-Acquired Weakness in Mechanically Ventilated Patients

BACKGROUND

Vasoactive medications are commonly used in the treatment of critically ill patients, but their impact on the development of ICU-acquired weakness is not well described. The objective of this study is to evaluate the relationship between vasoactive medication use and the outcome of ICU-acquired weakness.

METHODS

This is a secondary analysis of mechanically ventilated patients (N = 172) enrolled in a randomized clinical trial of early occupational and physical therapy vs conventional therapy, which evaluated the end point of ICU-acquired weakness on hospital discharge. Patients underwent bedside muscle strength testing by a therapist blinded to study allocation to evaluate for ICU-acquired weakness. The effects of vasoactive medication use on the incidence of ICU-acquired weakness in this population were assessed.

RESULTS

On logistic regression analysis, the use of vasoactive medications increased the odds of developing ICU-acquired weakness (odds ratio [OR], 3.2; P = .01) independent of all other established risk factors for weakness. Duration of vasoactive medication use (in days) (OR, 1.35; P = .004) and cumulative norepinephrine dose (μg/kg/d) (OR, 1.01; P = .02) (but not vasopressin or phenylephrine) were also independently associated with the outcome of ICU-acquired weakness.

CONCLUSIONS

In mechanically ventilated patients enrolled in a randomized clinical trial of early mobilization, the use of vasoactive medications was independently associated with the development of ICU-acquired weakness. Prospective trials to further evaluate this relationship are merited.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01777035; URL: www.clinicaltrials.gov.

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.

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

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

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.

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.

Intensive care unit-acquired neuromyopathy and corticosteroids in survivors of persistent ARDS

OBJECTIVES

To determine the incidence and outcomes of intensive care unit-acquired neuromyopathy and to investigate the role of methylprednisolone in survivors of persistent acute lung injury.

DESIGN

Secondary analysis of completed randomized placebo-controlled trial.

SETTING

Twenty-five hospitals in the NHLBI ARDS Network.

PATIENTS AND PARTICIPANTS

Patients enrolled in the ARDS Network study of methylprednisolone versus placebo for persistent ARDS who survived 60 days or to hospital discharge.

MEASUREMENTS AND RESULTS

One hundred and twenty-eight study patients survived 60 days. Forty-three (34%) of these patients had evidence by chart review of ICU-acquired neuromyopathy, which was associated with prolonged mechanical ventilation, return to mechanical ventilation, and delayed return to home after critical illness. Treatment with methylprednisolone was not significantly associated with an increase in risk of neuromyopathy (OR 1.5; 95% CI 0.7-3.2).

CONCLUSIONS

ICU-acquired-neuromyopathy is common among survivors of persistent ARDS and is associated with poorer clinical outcomes. We did not find a significant association between methylprednisolone treatment and neuromyopathy. Limitations of this study preclude definitive conclusions about the causal relationship between corticosteroids and ICU-acquired neuromuscular dysfunction.

Phrenic nerve stimulation

Weakness of the limbs and respiratory muscles has increasingly been found to be a frequent event that complicates the medical history of patients in Intensive Care. The problem normally affects more serious cases and presents as muscular weakness leading to flaccid paralysis and difficulty in weaning patients off mechanical ventilation. This latter sign leads the intensivist to suspect possible involvement of the neuromuscular respiratory system. Unfortunately, in-depth clinical assessment of the neuromuscular respiratory system is difficult with critically ill patients, and electrophysiological studies have been used instead to overcome this problem. Of these latter, electric and electromagnetic stimulation of the phrenic nerve have been successful (along with needle electromyography of the diaphragm) in identifying the causes of neuromuscular respiratory insufficiency, especially in Intensive Care. In this brief chapter, we will be discussing the technique of electric stimulation of the phrenic nerve and neuromuscular respiratory insufficiency within the field of critical illness polyneuropathy.

Predisposing factors for critical illness polyneuromyopathy in a multidisciplinary intensive care unit

OBJECTIVE

To investigate risk factors of critical illness polyneuromyopathy (CIPM) in a general multidisciplinary intensive care unit (ICU).

PATIENTS AND METHODS

Prospective observational study in a 28-bed university multidisciplinary ICU. Four hundred and seventy-four (323 M/151 F, age 55 +/- 19) consecutive patients were prospectively evaluated. All patients were assigned admission Acute Physiology and Chronic Health Evaluation (APACHE II; 15 +/- 7) and Sequential Organ Failure Assessment (SOFA; 6 +/- 3) scores and were subsequently evaluated for newly developed neuromuscular weakness. Other potential causes of new-onset weakness after ICU admission were excluded before CIPM was diagnosed.

RESULTS

Forty-four (23.8%) of 185 patients developed generalized weakness that met the criteria for CIPM. Patients with CIPM had higher APACHE II (18.9 +/- 6.6 vs 15.6 +/- 6.4, P = 0.004) and SOFA scores (8.4 +/- 2.9 vs 7.1 +/- 2.9, P = 0.013). According to multivariate logistic regression analysis, the following risk factors were independently associated with the development of CIPM: severity of illness at the time of ICU admission, administration of aminoglycoside antibiotics and high blood glucose levels. Analysis according to severity of illness stratification revealed the emergence of Gram (-) bacteremia as the most important independent predisposing factor for CIPM development in less severely ill patients.

CONCLUSIONS

CIPM has a high incidence in the ICU setting. Our study revealed the association of aminoglycosides, hyperglycemia and illness severity with CIPM development, as well as the association between Gram (-) bacteremia and development of CIPM in less severely ill patient population.

Mechanisms of neurologic failure in critical illness

Critical illness frequently is associated with neurologic failure that may involve the central and peripheral nervous systems. Central nervous system failure is associated with a spectrum of neurobehavioral changes including delirium, coma, and long-term cognitive dysfunction. Peripheral neurologic failure, or critical illness neuromuscular abnormalities, is suggested by diffuse arreflexic weakness and protracted respiratory insufficiency, and may also persist long after the acute hospitalization. While the burden of neurological disease complicating critical illness is considerable, preventive or therapeutic options are limited. This article provides an overview of research evaluating the relationship between critical illness and neurologic function, with a special emphasis on underlying mechanisms.

Neuromuscular dysfunction acquired in critical illness: a systematic review

OBJECTIVE

To determine the prevalence, risk factors, and outcomes of critical illness neuromuscular abnormalities (CINMA).

DESIGN

Systematic review.

DATA SOURCES AND STUDY SELECTION

MEDLINE, EMBASE, CINAHL, and the Cochrane Library were searched for reports on adult ICU patients who were evaluated for CINMA clinically and electrophysiologically. Studies were included if they contained sufficient data to quantify the association between CINMA and relevant exposures and/or outcome variables.

MEASUREMENTS AND RESULTS

CINMA was diagnosed in 655 of 1421 [46% (95% confidence interval 43-49%)] adult ICU patients enrolled in 24 studies, all with inclusion criteria of sepsis, multi-organ failure, or prolonged mechanical ventilation. Diagnostic criteria for CINMA were not uniform, and few reports unequivocally differentiated between polyneuropathy, myopathy, and mixed types of CINMA. The risk of CINMA was associated with hyperglycemia (and inversely associated with tight glycemic control), the systemic inflammatory response syndrome, sepsis, multiple organ dysfunction, renal replacement therapy, and catecholamine administration. Across studies, there was no consistent relationship between CINMA and patient age, gender, severity of illness, or use of glucocorticoids, neuromuscular blockers, aminoglycosides, or midazolam. Unadjusted mortality was not increased in the majority of patients with CINMA, but mechanical ventilation and ICU and hospital stay were prolonged.

CONCLUSIONS

The risk of CINMA is nearly 50% in ICU patients with sepsis, multi-organ failure, or protracted mechanical ventilation. The association of CINMA with frequently cited CINMA risk factors (glucocorticoids, neuromuscular blockers) and with short-term survival is uncertain. Available data indicate glycemic control as a potential strategy to decrease CINMA risk.

Critical illness neuromuscular syndromes

Critical illness neuromyopathy (CINM) is the most common peripheral neuromuscular disorder encountered in the ICU. Bilateral diffuse weakness predominant in the proximal part of the limbs after improvement of the acute phase of the critical illness is highly suggestive of CINM. Although muscle and peripheral nerve are often involved in combination, muscle involvement alone is increasingly identified on electrophysiologic investigation, including direct muscle stimulation. Respiratory weakness results in delayed weaning and prolonged mechanical ventilation. Besides muscle immobilization and prolonged sepsis-induced multiorgan failure, which are risk factors for CINM, hyperglycemia and use of corticosteroids might have a deleterious effect on the neuromuscular system in critically ill patients.

Critical Illness Neuromuscular Syndromes

Critical illness neuromyopathy (CINM) is the most common peripheral neuromuscular disorder encountered in the ICU. Bilateral diffuse weakness predominant in the proximal part of the limbs after improvement of the acute phase of the critical illness is highly suggestive of CINM. Although muscle and peripheral nerve often are involved in combination, muscle involvement alone increasingly is identified on electrophysiological investigation, including direct muscle stimulation. Respiratory muscles also are involved, and CINM may cause delayed weaning and prolonged MV. Besides muscle immobilization and prolonged sepsis-induced multiple organ failure, which are both strong contributors to CINM, hyperglycemia and use of corticosteroids also might have a deleterious effect on the neuromuscular system in critically ill patients.

Impact of intensive insulin therapy on neuromuscular complications and ventilator dependency in the medical intensive care unit

RATIONALE

Critical illness polyneuropathy/myopathy causes limb and respiratory muscle weakness, prolongs mechanical ventilation, and extends hospitalization of intensive care patients. Besides controlling risk factors, no specific prevention or treatment exists. Recently, intensive insulin therapy prevented critical illness polyneuropathy in a surgical intensive care unit.

OBJECTIVES

To investigate the impact of intensive insulin therapy on polyneuropathy/myopathy and treatment with prolonged mechanical ventilation in medical patients in the intensive care unit for at least 7 days.

METHODS

This was a prospectively planned subanalysis of a randomized controlled trial evaluating the effect of intensive insulin versus conventional therapy on morbidity and mortality in critically ill medical patients. All patients who were still in intensive care on Day 7 were screened weekly by electroneuromyography. The effect of intensive insulin therapy on critical illness polyneuropathy/myopathy and the relationship with duration of mechanical ventilation were assessed.

MEASUREMENTS AND MAIN RESULTS

Independent of risk factors, intensive insulin therapy reduced incidence of critical illness polyneuropathy/myopathy (107/212 [50.5%] to 81/208 [38.9%], p = 0.02). Treatment with prolonged (> or = 14 d) mechanical ventilation was reduced from 99 of 212 (46.7%) to 72 of 208 (34.6%) (p = 0.01). This was statistically only partially explained by prevention of critical illness polyneuropathy/myopathy.

CONCLUSION

In a subset of medical patients in the intensive care unit for at least 7 days, enrolled in a randomized controlled trial of intensive insulin therapy, those assigned to intensive insulin therapy had a reduced incidence of critical illness polyneuropathy/myopathy and were treated with prolonged mechanical ventilation less frequently.

Critical illness polyneuropathy and myopathy: clinical features, risk factors and prognosis

Acquired neuromuscular weakness due to critical illness polyneuropathy and myopathy (CIPNM) frequently develops in patients hospitalized in the intensive care unit for more than 1 week. CIPNM may present with muscle weakness and failure to wean from mechanical ventilation, but is discovered more often and earlier by electrophysiological examination. In this review, the incidence, clinical and electrophysiological features, differential diagnosis and prognosis of CIPNM will be described. Risk factors for CIPNM are sepsis or systemic inflammatory response syndrome and the severity of multi-organ failure. Presence of CIPNM is associated with higher mortality rate, prolonged duration of mechanical ventilation and prolonged rehabilitation. The majority of survivors with CIPNM have persistent functional disabilities and a reduced quality of life. There is need for new therapeutic strategies to prevent or minimize CIPNM in critically ill patients.

Neuromuscular disorders in critical illness

Neuromuscular disorders in the background of critical illness are under diagnosed. Standardized screening for weakness in the intensive care unit (ICU) setting is uncommon and persistent weakness as a sequel of critical illness is usually not recognized by physicians in the ICU for whom survival from acute illness is the primary outcome. The spectrum of illness ranges from isolated nerve entrapment with focal pain or weakness, to disuse muscle atrophy with mild weakness, and to severe myopathy or neuropathy with associated severe, prolonged weakness. This update focuses on neuromuscular disorders occurring in the critical care set up associated with diffuse and severe weakness.

Effect of critical illness polyneuropathy on the withdrawal from mechanical ventilation and the length of stay in septic patients*

OBJECTIVES

No previous study has demonstrated whether critical illness polyneuropathy itself lengthens mechanical ventilation or whether this prolonged duration of ventilatory support is explained by concomitant risk factors for weaning failure. Our objectives were to evaluate the impact of critical illness polyneuropathy on the length of mechanical ventilation after controlling for coexisting risk factors for weaning failure and to assess the impact of critical illness polyneuropathy on the length of the stay in a cohort of septic patients.

DESIGN

Prospective cohort study.

SETTING

Intensive care unit of a tertiary hospital.

PATIENTS

All patients with severe sepsis or septic shock who required mechanical ventilation for > or =7 days who were considered ready to discontinue mechanical ventilation.

INTERVENTIONS

Patients underwent a neurophysiologic evaluation at onset of weaning from mechanical ventilation.

MEASUREMENTS AND MAIN RESULTS

Sixty-four critically ill septic patients were enrolled, and 34 developed critical illness polyneuropathy (53.1%; 95% confidence interval, 40.2-65.7%). Length of mechanical ventilation was significantly higher in patients who had developed critical illness polyneuropathy (median 34 days vs. 14 days, p < .001). The duration of the weaning period was also significantly greater in patients with critical illness polyneuropathy (median 15 days vs. 2 days, p < .001) even though factors suspected to influence the weaning process did not differ between these two groups. Multiple logistic regression analysis indicated that critical illness polyneuropathy was the only risk factor independently associated with weaning failure (odds ratio, 15.4; 95% confidence interval, 4.55, 52.3; p < .001). Lengths of intensive care unit and hospital stays were significantly higher in patients with critical illness polyneuropathy.

CONCLUSIONS

In critically ill septic patients, critical illness polyneuropathy significantly increases the duration of mechanical ventilation and prolongs the lengths of intensive care unit and hospital stays.

Combination of histopathological and electromyographic patterns can help to evaluate functional outcome of critical ill patients with neuromuscular weakness syndromes

Introduction

The aim of the study was to describe patterns of neuromuscular weakness using a combination of electromyography and histology, and to evaluate functional outcome in patients following complicated cardiovascular surgery.

Methods

Fifteen adults requiring long-term mechanical ventilation (>15 days) following cardiovascular surgery associated with postoperative complications were prospectively included. Electrophysiological and histological analyses (muscle and nerve) were performed when failure to wean from mechanical ventilation associated with peripheral neuromuscular weakness was noticed. Functional disability was evaluated 12 months after surgery.

Results

Six patients had a predominantly axonal neuropathy, six presented with myopathy, and three patients had a combination of axonal neuropathy and myopathy. All of them presented with acute tetraparesis and failure to wean from mechanical ventilation. All of the study patients who received corticosteroids exhibited a myopathic pattern (with or without axonopathic changes) but never an axonopathic pattern only. Only two of the eight survivors at 12 months were not ambulatory. These two patients had no detectable compound muscle action potential on electrophysiological examination.

Conclusion

The combination of electromyographic evaluation and neuromuscular histological abnormalities could help to identify the type and severity of neuromuscular weakness, in turn helping to evaluate the patient's potential functional prognosis.

Critical illness polyneuropathy

Critical illness polyneuropathy (CIP) is a syndrome that was first extensively described in the early 1980s, mainly in patients with failure to wean from mechanical ventilation. The syndrome is further characterized by limb muscle weakness, usually more pronounced distally than proximally, and is often accompanied by atrophy. The facial musculature is often strikingly spared. Reduced or absent deep-tendon reflexes and loss of peripheral sensation to light touch and pin prick often accompany the syndrome. Involvement of the phrenic nerve has been shown to further contribute to delayed weaning from the ventilator in many patients. The electrophysiologic studies are consistent with a predominantly motor and, often to a lesser extent, sensory axonal polyneuropathy. The incidence of CIP is high, with often more than 50% of patients in major medical and surgical critical care units suffering from the syndrome. The systemic inflammatory response syndrome (SIRS) is strongly associated with CIP and, among the multiorgan failure often seen in SIRS, CIP is thought to represent a neurologic manifestation of SIRS. The neurologic effects of SIRS are thought to be mediated by released mediators like cytokines and free radicals, affecting the microcirculation of the central and peripheral nervous system. Examination of the peripheral nervous system is often unreliable, and the only way to establish a definitive diagnosis is by performing electrophysiologic studies. Morbidity and mortality rates are high. If the underlying problem causing sepsis and/or SIRS can be treated successfully, full recovery from CIP can occur. This recovery often occurs in a matter of weeks in milder cases and in months in more severe cases. Knowledge of CIP is essential for intensivists and other specialists who care for critically ill patients. This review summarizes the current available literature on this topic.

Critical illness neuromuscular abnormalities

CINMAs occur commonly in acutely critically ill inflamed patients, and can prolong respiratory failure, lead to ventilator dependency, and contribute to the development of chronic critical illness. The etiology of NMDs are diverse and overlap, and distinguishing different disease entities by clinical exam and electrophysiologic studies can be difficult. CIP, which has been the most widely studied CINMA, represents the peripheral nervous system manifestation of the MODS. Patients with CIP, particularly those with severely reduced nerve function, have a prolonged rehabilitation and a high mortality rate. Although there are no definitive treatments, diagnosing a CINMA may provide helpful prognostic information. Future preventative measures may include immunoglobulin, nerve growth factors, or strict glycemic control, although in the CCI phase general supportive care is given, including prevention of iatrogenic complications, nutritional support, psychosocial support, and physical therapy. The early recognition of CINMAs and prevention of associated complications are important to enabling CCI patients with CINMAs to recover and return home with an acceptable functional level and quality of life.