Neuromuscular blocking agents decrease inflammatory response in patients presenting with acute respiratory distress syndrome*

Mechanical Ventilation during Extracorporeal Membrane Oxygenation in Patients with Acute Severe Respiratory Failure

Conventionally, a substantial number of patients with acute respiratory failure require mechanical ventilation (MV) to avert catastrophe of hypoxemia and hypercapnia. However, mechanical ventilation per se can cause lung injury, accelerating the disease progression. Extracorporeal membrane oxygenation (ECMO) provides an alternative to rescue patients with severe respiratory failure that conventional mechanical ventilation fails to maintain adequate gas exchange. The physiology behind ECMO and its interaction with MV were reviewed. Next, we discussed the timing of ECMO initiation based on the risks and benefits of ECMO. During the running of ECMO, the protective ventilation strategy can be employed without worrying about catastrophic hypoxemia and carbon dioxide retention. There is a large body of evidence showing that protective ventilation with low tidal volume, high positive end-expiratory pressure, and prone positioning can provide benefits on mortality outcome. More recently, there is an increasing popularity on the use of awake and spontaneous breathing for patients undergoing ECMO, which is thought to be beneficial in terms of rehabilitation.

Perceived safety and efficacy of neuromuscular blockers for acute respiratory distress syndrome among medical intensive care unit practitioners: A multicenter survey

PURPOSE

Neuromuscular blocking agents (NMBAs) are frequently used in patients with acute respiratory distress syndrome (ARDS). The purpose of this survey is to describe providers' knowledge and perceived efficacy and safety of NMBAs in patients with ARDS.

MATERIALS AND METHODS

We performed a prospective, multicenter survey of medical intensive care unit intensivists, fellows, nurse practitioners (NPs), physician's assistants (PAs), and pharmacists at 5 tertiary care centers between July 2012 and May 2013.

RESULTS

A total of 335 surveys were sent to providers, with a 47% response rate. Ninety-eight percent of providers correctly identified that NMBAs lack anxiolytic and analgesic properties. The effect of end-organ damage on NMBA clearance was less commonly identified by NPs/PAs for both hepatic (P=.0077) and renal (P=.0272) dysfunction compared with physicians. More NP/PAs identified the association of consciousness with the use of NMBAs than physicians (P=.047). Forty-two percent of prescribers reported always or frequently using continuous-infusion NMBAs in patients with severe ARDS, with 89% initiating NMBAs because of ventilator dyssynchrony. Prescribers perceived continuous NMBAs to be more effective than inhaled prostaglandins (74% vs 56%) in severe ARDS but less safe (45% vs 84%). Train of 4 was identified by 54% of prescribers as their primary method for titration.

CONCLUSION

Providers are knowledgeable about NMBAs, but educational opportunities exist. Perceptions about the efficacy and safety of NMBAs varied among prescribers, and inconsistencies existed in the prioritization of management strategies for ARDS.

Neuromuscular Blockade in the 21st Century Management of the Critically Ill Patient

Neuromuscular blockings agents (NMBAs) have a controversial role in the ventilatory and medical management of critical illness. The clinical concern surrounding NMBA-induced complications stems from evidence presented in the 2002 clinical practice guidelines, but new evidence from subsequent randomized trials and studies provides a more optimistic outlook about the application of NMBAs in the ICU. Furthermore, changes in the delivery of critical care, such as protocolized care pathways, minimizing or interrupting sedation, increased monitoring techniques, and overall improvements in reducing immobility, have created a modern, 21st century ICU environment whereby NMBAs may be administered safely. In this article we start with a review of the mechanism of action, side effects, and pharmacology of commonly used NMBAs. We then address the rationale for NMBA use for an expanding number of indications (endotracheal intubation, acute respiratory distress syndrome, status asthmaticus, increased intracranial and intra-abdominal pressure, and therapeutic hypothermia after cardiac arrest), with an emphasis on NMBA use in facilitating lung-protective ventilation for respiratory failure. We end with an appraisal over the importance of monitoring depth of paralysis and the concerns of complications, such as prolonged skeletal muscle weakness. In the context of adequate sedation and analgesia, monitored NMBA use (continuous or bolus administration) can be considered for the small number of clinical indications in critically ill patients for which evidence currently exists.

Short-term effects of neuromuscular blockade on global and regional lung mechanics, oxygenation and ventilation in pediatric acute hypoxemic respiratory failure

Background

Neuromuscular blockade (NMB) has been shown to improve outcome in acute respiratory distress syndrome (ARDS) in adults, challenging maintaining spontaneous breathing when there is severe lung injury. We tested in a prospective physiological study the hypothesis that continuous administration of NMB agents in mechanically ventilated children with severe acute hypoxemic respiratory failure (AHRF) improves the oxygenation index without a redistribution of tidal volume V_T toward non-dependent lung zones.

Methods

Oxygenation index, PaO₂/FiO₂ ratio, lung mechanics (plateau pressure, mean airway pressure, respiratory system compliance and resistance), hemodynamics (heart rate, central venous and arterial blood pressures), oxygenation [oxygenation index (OI), PaO₂/FiO₂ and SpO₂/FiO₂], ventilation (physiological dead space-to-V_T ratio) and electrical impedance tomography measured changes in end-expiratory lung volume (EELV), and V_T distribution was measured before and 15 min after the start of continuous infusion of rocuronium 1 mg/kg. Patients were ventilated in a time-cycled, pressure-limited mode with pre-set V_T. All ventilator settings were not changed during the study.

Results

Twenty-two patients were studied (N = 18 met the criteria for pediatric ARDS). Median age (25–75 interquartile range) was 15 (7.8–77.5) weeks. Pulmonary pathology was present in 77.3%. The median lung injury score was 9 (8–10). The overall median CoV and regional lung filling characteristics were not affected by NMB, indicating no ventilation shift toward the non-dependent lung zones. Regional analysis showed a homogeneous time course of lung inflation during inspiration, indicating no tendency to atelectasis after the introduction of NMB. NMB decreased the mean airway pressure (p = 0.039) and OI (p = 0.039) in all patients. There were no significant changes in lung mechanics, hemodynamics and EELV. Subgroup analysis showed that OI decreased (p = 0.01) and PaO₂/FiO₂ increased (p = 0.02) in patients with moderate or severe PARDS.

Conclusions

NMB resulted in an improved oxygenation index in pediatric patients with AHRF. Distribution of V_T and regional lung filling characteristics were not affected.

Acute respiratory distress syndrome following cardiovascular surgery: current concepts and novel therapeutic approaches

PURPOSE OF REVIEW

This review gives an update on current treatment options and novel concepts on the prevention and treatment of the acute respiratory distress syndrome (ARDS) in cardiovascular surgery patients.

RECENT FINDINGS

The only proven beneficial therapeutic options in ARDS are those that help to prevent further ventilator-induced lung injury, such as prone position, use of lung-protective ventilation strategies, and extracorporeal membrane oxygenation. In the future also new approaches like mesenchymal cell therapy, activation of hypoxia-elicited transcription factors or targeting of purinergic signaling may be successful outside the experimental setting. Owing to the so far limited treatment options, it is of great importance to determine patients at risk for developing ARDS already perioperatively. In this context, serum biomarkers and lung injury prediction scores could be useful.

SUMMARY

Preventing ARDS as a severe complication in the cardiovascular surgery setting may help to reduce morbidity and mortality. As cardiovascular surgery patients are of greater risk to develop ARDS, preventive interventions should be implemented early on. Especially, use of low tidal volumes, avoiding of fluid overload and restrictive blood transfusion regimes may help to prevent ARDS.

Clinical Practice Guideline of Acute Respiratory Distress Syndrome

There is no well-stated practical guideline for mechanically ventilated patients with or without acute respiratory distress syndrome (ARDS). We generate strong (1) and weak (2) grade of recommendations based on high (A), moderate (B) and low (C) grade in the quality of evidence. In patients with ARDS, we recommend low tidal volume ventilation (1A) and prone position if it is not contraindicated (1B) to reduce their mortality. However, we did not support high-frequency oscillatory ventilation (1B) and inhaled nitric oxide (1A) as a standard treatment. We also suggest high positive end-expiratory pressure (2B), extracorporeal membrane oxygenation as a rescue therapy (2C), and neuromuscular blockage for 48 hours after starting mechanical ventilation (2B). The application of recruitment maneuver may reduce mortality (2B), however, the use of systemic steroids cannot reduce mortality (2B). In mechanically ventilated patients, we recommend light sedation (1B) and low tidal volume even without ARDS (1B) and suggest lung protective ventilation strategy during the operation to lower the incidence of lung complications including ARDS (2B). Early tracheostomy in mechanically ventilated patients can be performed only in limited patients (2A). In conclusion, of 12 recommendations, nine were in the management of ARDS, and three for mechanically ventilated patients.

Corticosteroids and neuromuscular blockers in development of critical illness neuromuscular abnormalities: A historical review

Weakness is common in critically ill patients, associated with prolonged mechanical ventilation and increased mortality. Corticosteroids and neuromuscular blockade (NMB) administration have been implicated as etiologies of acquired weakness in the intensive care unit. Medical literature since the 1970s is replete with case reports and small case series of patients with weakness after receiving high-dose corticosteroids, prolonged NMB, or both. Several risk factors for weakness appear in the early literature, including large doses of steroids, the dose and duration of NMB, hyperglycemia, and the duration of mechanical ventilation. With improved quality of data, however, the association between weakness and steroids or NMB wanes. This may reflect changes in clinical practice, such as a reduction in steroid dosing, use of cisatracurium besylate instead of aminosteroid NMBs, improved glycemic control, or trends in minimizing mechanical ventilatory support. Thus, based on the most recent and high-quality literature, neither corticosteroids in commonly used doses nor NMB is associated with increased duration of mechanical ventilation, the greatest morbidity of weakness. Minimizing ventilator support as soon as the patient's condition allows may be associated with a reduction in weakness-related morbidity.

Association Between Train-of-Four Values and Gas Exchange Indices in Moderate to Severe Acute Respiratory Distress Syndrome

BACKGROUND

Acute respiratory distress syndrome (ARDS) is associated with a mortality rate of approximately 40%. Neuromuscular blockade is associated with an improvement in oxygenation and a reduction in mortality in ARDS.

OBJECTIVE

The goal of this evaluation was to determine if the depth of paralysis, determined by train-of-four (TOF) monitoring, correlates with gas exchange in moderate to severe ARDS.

METHODS

This was a retrospective review of moderate to severe ARDS patients who were prescribed >12 hours of continuous infusion cisatracurium between January 1, 2013, and December 31, 2014, with a PaO₂:FiO₂ ratio <150 and documented TOF and arterial blood gases. Patients were evaluated for inclusion at 12, 24, and 48 hours after initiation of neuromuscular blockade.

RESULTS

A total of 378 patients were screened for inclusion, with 107 evaluable patients meeting criteria at baseline. Poor correlation existed between TOF and oxygenation index (OI) at 12 (τ = 0.03), 24 (τ = 0.15) and 48 hours (τ = 0.08). When controlling for proning and baseline OI, the depth of paralysis did not have a significant effect on OI at 12, 24, or 48 hours.

CONCLUSIONS

This evaluation demonstrates that the use of TOF monitoring for neuromuscular blockade does not correlate with gas exchange markers in moderate to severe ARDS.

Scandinavian clinical practice guideline on fluid and drug therapy in adults with acute respiratory distress syndrome

BACKGROUND

The objective of the Scandinavian Society of Anaesthesiology and Intensive Care Medicine (SSAI) task force on fluid and drug therapy in adults with acute respiratory distress syndrome (ARDS) was to provide clinically relevant, evidence-based treatment recommendations according to standards for trustworthy guidelines.

METHODS

The guideline was developed according to standards for trustworthy guidelines, including a systematic review of the literature and use of the GRADE methodology for assessment of the quality of evidence and for moving from evidence to recommendations.

RESULTS

A total of seven ARDS interventions were assessed. We suggest fluid restriction in patients with ARDS (weak recommendation, moderate quality evidence). Also, we suggest early use of neuromuscular blocking agents (NMBAs) in patients with severe ARDS (weak recommendation, moderate quality evidence). We recommend against the routine use of other drugs, including corticosteroids, beta2 agonists, statins, and inhaled nitric oxide (iNO) or prostanoids in adults with ARDS (strong recommendations: low- to high-quality evidence). These recommendations do not preclude the use of any drug or combination of drugs targeting underlying or co-existing disorders.

CONCLUSION

This guideline emphasizes the paucity of evidence of benefit - and potential for harm - of common interventions in adults with ARDS and highlights the need for prudence when considering use of non-licensed interventions in this patient population.

Severe hypoxemia: which strategy to choose

BACKGROUND

Acute respiratory distress syndrome (ARDS) is characterized by a noncardiogenic pulmonary edema with bilateral chest X-ray opacities and reduction in lung compliance, and the hallmark of the syndrome is hypoxemia refractory to oxygen therapy. Severe hypoxemia (PaO2/FiO2 < 100 mmHg), which defines severe ARDS, can be found in 20-30 % of the patients and is associated with the highest mortality rate. Although the standard supportive treatment remains mechanical ventilation (noninvasive and invasive), possible adjuvant therapies can be considered. We performed an up-to-date clinical review of the possible available strategies for ARDS patients with severe hypoxemia.

MAIN RESULTS

In summary, in moderate-to-severe ARDS or in the presence of other organ failure, noninvasive ventilatory support presents a high risk of failure: in those cases the risk/benefit of delayed mechanical ventilation should be evaluated carefully. Tailoring mechanical ventilation to the individual patient is fundamental to reduce the risk of ventilation-induced lung injury (VILI): it is mandatory to apply a low tidal volume, while the optimal level of positive end-expiratory pressure should be selected after a stratification of the severity of the disease, also taking into account lung recruitability; monitoring transpulmonary pressure or airway driving pressure can help to avoid lung overstress. Targeting oxygenation of 88-92 % and tolerating a moderate level of hypercapnia are a safe choice. Neuromuscular blocking agents (NMBAs) are useful to maintain patient-ventilation synchrony in the first hours; prone positioning improves oxygenation in most cases and promotes a more homogeneous distribution of ventilation, reducing the risk of VILI; both treatments, also in combination, are associated with an improvement in outcome if applied in the acute phase in the most severe cases. The use of extracorporeal membrane oxygenation (ECMO) in severe ARDS is increasing worldwide, but because of a lack of randomized trials is still considered a rescue therapy.

CONCLUSION

Severe ARDS patients should receive a holistic framework of respiratory and hemodynamic support aimed to ensure adequate gas exchange while minimizing the risk of VILI, by promoting lung recruitment and setting protective mechanical ventilation. In the most severe cases, NMBAs, prone positioning, and ECMO should be considered.

Recent advances in understanding and treating ARDS

Acute respiratory distress syndrome represents a complex syndrome with considerable morbidity and mortality, for which there exist no targeted treatment strategies. However, recent advances in clinical care have improved outcomes, and we will review a number of these approaches here, as well as explore the mechanisms underlying the benefit of intervention that might point us in the direction toward future treatment and preventive strategies for this devastating syndrome.

The standard of care of patients with ARDS: ventilatory settings and rescue therapies for refractory hypoxemia

Purpose

Severe ARDS is often associated with refractory hypoxemia, and early identification and treatment of hypoxemia is mandatory. For the management of severe ARDS ventilator settings, positioning therapy, infection control, and supportive measures are essential to improve survival.

Methods and results

A precise definition of life-threating hypoxemia is not identified. Typical clinical determinations are: arterial partial pressure of oxygen < 60 mmHg and/or arterial oxygenation < 88 % and/or the ratio of PaO₂/FIO₂ < 100. For mechanical ventilation specific settings are recommended: limitation of tidal volume (6 ml/kg predicted body weight), adequate high PEEP (>12 cmH₂O), a recruitment manoeuvre in special situations, and a ‘balanced’ respiratory rate (20-30/min). Individual bedside methods to guide PEEP/recruitment (e.g., transpulmonary pressure) are not (yet) available. Prone positioning [early (≤ 48 hrs after onset of severe ARDS) and prolonged (repetition of 16-hr-sessions)] improves survival. An advanced infection management/control includes early diagnosis of bacterial, atypical, viral and fungal specimen (blood culture, bronchoalveolar lavage), and of infection sources by CT scan, followed by administration of broad-spectrum anti-infectives. Neuromuscular blockage (Cisatracurium ≤ 48 hrs after onset of ARDS), as well as an adequate sedation strategy (score guided) is an important supportive therapy. A negative fluid balance is associated with improved lung function and the use of hemofiltration might be indicated for specific indications.

Conclusions

A specific standard of care is required for the management of severe ARDS with refractory hypoxemia.

Neuromuscular Blocking Agent Cisatracurium Attenuates Lung Injury by Inhibition of Nicotinic Acetylcholine Receptor-α1

Background

Neuromuscular blocking agents (NMBAs) bind the nicotinic acetylcholine receptor α1 (nAChRα1) that also contributes to inflammatory signaling. Thus, the author hypothesized that the use of NMBA mitigates lung injury by improving ventilator synchrony and decreasing inflammatory responses.

Methods

Lung injury was induced by intratracheal instillation of hydrogen chloride in rats that were randomized to receive no NMBA with evidence of asynchronous ventilation (noNMBA/aSYNC, n = 10); no NMBA with synchronous ventilation (noNMBA/SYNC, n = 10); cisatracurium (CIS, n = 10); or pancuronium (PAN, n = 10). Mechanical ventilation was set at a tidal volume of 6 ml/kg and positive end-expiratory pressure 8 cm H2O for 3 h. Human lung epithelial, endothelial, and CD14+ cells were challenged with mechanical stretch, lipopolysaccharide, lung lavage fluids (bronchoalveolar lavage fluid), or plasma obtained from patients (n = 5) with acute respiratory distress syndrome, in the presence or absence of CIS or small-interfering RNA and small hairpin RNA to attenuate the cell expression of nAChRα1.

Results

The use of CIS and PAN improved respiratory compliance (7.2 ± 0.7 in noNMBA/aSYNC, 6.6 ± 0.5 in noNMBA/SYNC, 5.9 ± 0.3 in CIS, and 5.8 ± 0.4 cm H2O/l in PAN; P &lt; 0.05), increased Pao2 (140 ± 54, 209 ± 46, 269 ± 31, and 269 ± 54 mmHg, respectively, P &lt; 0.05), and decreased the plasma levels of tumor necrosis factor-α (509 ± 252 in noNMBA, 200 ± 74 in CIS, and 175 ± 84 pg/ml in PAN; P &lt; 0.05) and interleukin-6 (5789 ± 79, 1608 ± 534, and 2290 ± 315 pg/ml, respectively; P &lt; 0.05). The use of CIS and PAN or silencing the receptor nAChRα1 resulted in decreased cytokine release in the human cells in response to a variety of stimuli mentioned earlier.

Conclusions

The use of NMBA is lung protective through its antiinflammatory properties by blocking the nAChRα1.

Early Treatment of Severe Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is defined by acute diffuse inflammatory lung injury invoked by a variety of systemic or pulmonary insults. Despite medical progress in management, mortality remains 27% to 45%. Patients with ARDS should be managed with low tidal volume ventilation. Permissive hypercapnea is well tolerated. Conservative fluid strategy can reduce ventilator and hospital days in patients without shock. Prone positioning and neuromuscular blockers reduce mortality in some patients. Early management of ARDS is relevant to emergency medicine. Identifying ARDS patients who should be transferred to an extracorporeal membrane oxygenation center is an important task for emergency providers.

The role of spontaneous effort during mechanical ventilation: normal lung versus injured lung

The role of preserving spontaneous effort during mechanical ventilation and its interaction with mechanical ventilation have been actively investigated for several decades. Inspiratory muscle activities can lower the pleural components surrounding the lung, leading to an increase in transpulmonary pressure when spontaneous breathing effort is preserved during mechanical ventilation. Thus, increased transpulmonary pressure provides various benefits for gas exchange, ventilation pattern, and lung aeration. However, it is important to note that these beneficial effects of preserved spontaneous effort have been demonstrated only when spontaneous effort is modest and lung injury is less severe. Recent studies have revealed the ‘dark side’ of spontaneous effort during mechanical ventilation, especially in severe lung injury. The ‘dark side’ refers to uncontrollable transpulmonary pressure due to combined high inspiratory pressure with excessive spontaneous effort and the injurious lung inflation pattern of Pendelluft (i.e., the translocation of air from nondependent lung regions to dependent lung regions). Thus, during the early stages of severe ARDS, the strict control of transpulmonary pressure and prevention of Pendelluft should be achieved with the short-term use of muscle paralysis. When there is preserved spontaneous effort in ARDS, spontaneous effort should be maintained at a modest level, as the transpulmonary pressure and the effect size of Pendelluft depend on the intensity of the spontaneous effort.

Outcomes and prognostic factors in patients with prolonged acute mechanical ventilation: A single-center study in Korea

PURPOSE

The purpose of the study is to evaluate outcomes and objective parameters related to poor prognosis in patients who were defined as prolonged acute mechanical ventilation (PAMV; ventilator care ≥96 hours) in the medical intensive care unit of a university-affiliated tertiary care hospital in Korea.

MATERIAL AND METHODS

We analyzed retrospectively clinical data gathered from the medical records on day 4 of MV between 2008 and 2013. In total, 311 were categorized as PAMV.

RESULTS

Their median age was 67 years (range, 18-93 years), and 71.7% were male. The 28-day mortality rate after intensive care unit admission was 34.7%. Four variables on day 4 of mechanical ventilation (need for neuromuscular blockers [hazard ratio {HR}, 2.432; 95% confidence interval, 1.337-4.422], need for vasopressors [HR, 2.312; 95% confidence interval, 1.258-4.248], need for hemodialyses [HR, 1.913; 95% confidence interval, 1.018-3.595], and body mass index ≤21 kg/m(2) [HR, 1.827; 95% confidence interval, 1.015-3.288]) were independent factors associated with mortality based on a Cox proportional hazards model. As the number of these prognostic factors increased, the survival rate decreased.

CONCLUSIONS

Four clinical factors (body mass index ≤21, requirement for neuromuscular blockers, vasopressors, and hemodialysis) on day 4 of mechanical ventilation were associated with 28-day mortality in PAMV patients.

Nonpulmonary treatments for pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference

OBJECTIVE

To describe the recommendations from the Pediatric Acute Lung Injury Consensus Conference on nonpulmonary treatments in pediatric acute respiratory distress syndrome.

DESIGN

Consensus conference of experts in pediatric acute lung injury.

METHODS

A panel of 27 experts met over the course of 2 years to develop a taxonomy to define pediatric acute respiratory distress syndrome and to make recommendations regarding treatment and research priorities. The nonpulmonary subgroup comprised three experts. When published data were lacking, a modified Delphi approach emphasizing strong professional agreement was utilized.

RESULTS

The Pediatric Acute Lung Injury Consensus Conference experts developed and voted on a total of 151 recommendations addressing the topics related to pediatric acute respiratory distress syndrome, 30 of which related to nonpulmonary treatment. All 30 recommendations had strong agreement. Patients with pediatric acute respiratory distress syndrome should receive 1) minimal yet effective targeted sedation to facilitate mechanical ventilation; 2) neuromuscular blockade, if sedation alone is inadequate to achieve effective mechanical ventilation; 3) a nutrition plan to facilitate their recovery, maintain their growth, and meet their metabolic needs; 4) goal-directed fluid management to maintain adequate intravascular volume, end-organ perfusion, and optimal delivery of oxygen; and 5) goal-directed RBC transfusion to maintain adequate oxygen delivery. Future clinical trials in pediatric acute respiratory distress syndrome should report sedation, neuromuscular blockade, nutrition, fluid management, and transfusion exposures to allow comparison across studies.

CONCLUSIONS

The Consensus Conference developed pediatric-specific definitions for pediatric acute respiratory distress syndrome and recommendations regarding treatment and future research priorities. These recommendations for nonpulmonary treatment in pediatric acute respiratory distress syndrome are intended to promote optimization and consistency of care for patients with pediatric acute respiratory distress syndrome and identify areas of uncertainty requiring further investigation.

Critical care of burn patients. New approaches to old problems

Recent publications on treatment options in critically ill patients change beliefs and clinical behaviors. Many dogmas, which the modern management of critical illness relies on, have been questioned. These publications (consensus articles, reviews, meta-analysis and original papers) concern some fundamental issues of critical care: interventions in acute respiratory distress syndrome (ARDS), hemodynamic monitoring, glucose control and nutritional support and revise our views on many key points of critical care of burn patients.

Recent advances in mechanical ventilation in patients with acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is characterised by different degrees of severity and different stages. Understanding these differences can help to better adapt the ventilatory settings to protect the lung from ventilator-induced lung injury by reducing hyperinflation or keeping the lung open when it is possible. The same therapies may be useful and beneficial in certain forms of ARDS, and risky or harmful at other stages: this includes high positive end-expiratory pressure, allowance of spontaneous breathing activity or use of noninvasive ventilation. The severity of the disease is the primary indicator to individualise treatment. Monitoring tools such as oesophageal pressure or lung volume measurements may also help to set the ventilator. At an earlier stage, an adequate lung protective strategy may also help to prevent the development of ARDS.

Acute respiratory distress syndrome on the intensive care unit

Acute respiratory distress syndrome is a life-threatening condition that is common in critically ill patients. Historically, diagnosis has been difficult and prognosis has been poor, but the Berlin definition and developments in medical therapies provide promise that we can improve outcomes for these patients in the future.

Pressure-controlled versus volume-controlled ventilation for acute respiratory failure due to acute lung injury (ALI) or acute respiratory distress syndrome (ARDS)

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) account for one-quarter of cases of acute respiratory failure in intensive care units (ICUs). A third to half of patients will die in the ICU, in hospital or during follow-up. Mechanical ventilation of people with ALI/ARDS allows time for the lungs to heal, but ventilation is invasive and can result in lung injury. It is uncertain whether ventilator-related injury would be reduced if pressure delivered by the ventilator with each breath is controlled, or whether the volume of air delivered by each breath is limited.

OBJECTIVES

To compare pressure-controlled ventilation (PCV) versus volume-controlled ventilation (VCV) in adults with ALI/ARDS to determine whether PCV reduces in-hospital mortality and morbidity in intubated and ventilated adults.

SEARCH METHODS

In October 2014, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Isssue 9), MEDLINE (1950 to 1 October 2014), EMBASE (1980 to 1 October 2014), the Latin American Caribbean Health Sciences Literature (LILACS) (1994 to 1 October 2014) and Science Citation Index-Expanded (SCI-EXPANDED) at the Institute for Scientific Information (ISI) Web of Science (1990 to 1 October 2014), as well as regional databases, clinical trials registries, conference proceedings and reference lists.

SELECTION CRITERIA

Randomized controlled trials (RCTs) and quasi-RCTs (irrespective of language or publication status) of adults with a diagnosis of acute respiratory failure or acute on chronic respiratory failure and fulfilling the criteria for ALI/ARDS as defined by the American-European Consensus Conference who were admitted to an ICU for invasive mechanical ventilation, comparing pressure-controlled or pressure-controlled inverse-ratio ventilation, or an equivalent pressure-controlled mode (PCV), versus volume-controlled ventilation, or an equivalent volume-controlled mode (VCV).

DATA COLLECTION AND ANALYSIS

Two review authors independently screened and selected trials, assessed risk of bias and extracted data. We sought clarification from trial authors when needed. We pooled risk ratios (RRs) for dichotomous data and mean differences (MDs) for continuous data with their 95% confidence intervals (CIs) using a random-effects model. We assessed overall evidence quality using the GRADE (Grades of Recommendation, Assessment, Development and Evaluation) approach.

MAIN RESULTS

We included three RCTs that randomly assigned a total of 1089 participants recruited from 43 ICUs in Australia, Canada, Saudi Arabia, Spain and the USA. Risk of bias of the included studies was low. Only data for mortality and barotrauma could be combined in the meta-analysis. We downgraded the quality of evidence for the three mortality outcomes on the basis of serious imprecision around the effect estimates. For mortality in hospital, the RR with PCV compared with VCV was 0.83 (95% CI 0.67 to 1.02; three trials, 1089 participants; moderate-quality evidence), and for mortality in the ICU, the RR with PCV compared with VCV was 0.84 (95% CI 0.71 to 0.99; two trials, 1062 participants; moderate-quality evidence). One study provided no evidence of clear benefit with the ventilatory mode for mortality at 28 days (RR 0.88, 95% CI 0.73 to 1.06; 983 participants; moderate-quality evidence). The difference in effect on barotrauma between PCV and VCV was uncertain as the result of imprecision and different co-interventions used in the studies (RR 1.24, 95% CI 0.87 to 1.77; two trials, 1062 participants; low-quality evidence). Data from one trial with 983 participants for the mean duration of ventilation, and from another trial with 78 participants for the mean number of extrapulmonary organ failures that developed with PCV or VCV, were skewed. None of the trials reported on infection during ventilation or quality of life after discharge.

AUTHORS' CONCLUSIONS

Currently available data from RCTs are insufficient to confirm or refute whether pressure-controlled or volume-controlled ventilation offers any advantage for people with acute respiratory failure due to acute lung injury or acute respiratory distress syndrome. More studies including a larger number of people given PCV and VCV may provide reliable evidence on which more firm conclusions can be based.

The use of paralytics in patients with acute respiratory distress syndrome

Interest in the role of neuromuscular blocking agents (NMBAs) in the treatment of acute respiratory distress syndrome (ARDS) has been renewed since a recent randomized clinical trial showed a reduction in mortality associated with the use of NMBAs. However, the role of paralytics in a protective mechanical ventilation strategy should be detailed. This review summarizes data in the literature concerning the clinical effects of NMBAs on the outcome of patients with ARDS, in an attempt to explain some pathophysiologic hypotheses concerning their action and to integrate them into the overall management strategy for the mechanical ventilation of ARDS patients.

Veno-venous ECMO: a synopsis of nine key potential challenges, considerations, and controversies

Background

Following the 2009 H1N1 Influenza pandemic, extracorporeal membrane oxygenation (ECMO) emerged as a viable alternative in selected, severe cases of ARDS. Acute Respiratory Distress Syndrome (ARDS) is a major public health problem. Average medical costs for ARDS survivors on an annual basis are multiple times those dedicated to a healthy individual. Advances in medical and ventilatory management of severe lung injury and ARDS have improved outcomes in some patients, but these advances fail to consistently “rescue” a significant proportion of those affected.

Discussion

Here we present a synopsis of the challenges, considerations, and potential controversies regarding veno-venous ECMO that will be of benefit to anesthesiologists, surgeons, and intensivists, especially those newly confronted with care of the ECMO patient. We outline a number of points related to ECMO, particularly regarding cannulation, pump/oxygenator design, anticoagulation, and intravascular fluid management of patients. We then address these challenges/considerations/controversies in the context of their potential future implications on clinical approaches to ECMO patients, focusing on the development and advancement of standardized ECMO clinical practices.

Summary

Since the 2009 H1N1 pandemic ECMO has gained a wider acceptance. There are challenges that still must be overcome. Further investigations of the benefits and effects of ECMO need to be undertaken in order to facilitate the implementation of this technology on a larger scale.

Clinical year in review 2014: critical care medicine

Severe sepsis is the most common cause of death among critically ill patients in non-coronary intensive care units. In 2002, the guideline titled "Surviving Sepsis Campaign" was published by American and European Critical Care Medicine to decrease the mortality of severe sepsis and septic shock patients, which has been the basis of the treatment for those patients. After the first revised guidelines were published on 2008, the most current version was published in 2013 based on the updated literature of until fall 2012. Other important revised guidelines in critical care field such as 'Clinical Practice Guidelines for the Management of Pain, Agitation, and Delirium in Adult Patients in the Intensive Care Unit' were revised in 2013. This article will review the revised guidelines and several additional interesting published papers of until March 2014, including the part of ventilator-induced lung injury and the preventive strategies.

Bench-to-bedside: The use of local anesthetics to attenuate inflammation in acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) remains a world-wide treatment challenge, with high morbidity and mortality. The central pathophysiology of ARDS centers around inflammation in the lung and increased microvascular permeability. Local anesthetics have been shown to have anti-inflammatory effects at the basic science level and the advent of local anesthetics with improved cardiovascular safety profiles has made use of local anesthetics in attenuating the inflammation in ARDS a recent research interest. In this review, we will provide a brief summary of some of the basic science work in local anesthetics and lung inflammation and provide a case for the bench to bedside research in this potential therapy.

A practical approach to the use of prone therapy in acute respiratory distress syndrome

In this article we propose a practical approach to the use of prone therapy for acute respiratory distress syndrome (ARDS). We have attempted to provide information to improve the understanding and implementation of prone therapy based on the literature available and our own experience. We review the basic physiology behind ARDS and the theoretical mechanism by which prone therapy can be of benefit. The findings of the most significant studies regarding prone therapy in ARDS as they pertain to its implementation are summarized. Also provided is a discussion of the nuances of utilizing prone therapy, including potential pitfalls, complications, and contraindications. The specific considerations of prone therapy in open abdomens and traumatic brain injuries are discussed as well. Finally, we supply suggested protocols for the implementation of prone therapy discussing criteria for initiation and cessation of therapy as well as addressing issues such as the use of neuromuscular blockade and nutritional supplementation.

Serum activin A and B, and follistatin in critically ill patients with influenza A(H1N1) infection

Background

Activin A and its binding protein follistatin (FS) are increased in inflammatory disorders and sepsis. Overexpression of activin A in the lung causes similar histopathological changes as acute respiratory distress syndrome (ARDS). ARDS and severe respiratory failure are complications of influenza A(H1N1) infection. Interleukin 6 (IL-6), which in experimental studies increases after activin A release, is known to be related to the severity of H1N1 infection. Our aim was to evaluate the levels of activin A, activin B, FS, IL-6 and IL-10 and their association with the severity of respiratory failure in critically ill H1N1 patients.

Methods

A substudy of a prospective, observational cohort of H1N1 patients in Finnish intensive care units (ICU). Clinical information was recorded during ICU treatment, and serum activin A, activin B, FS, IL-6 and IL-10 were measured at admission to ICU and on days 2 and 7.

Results

Blood samples from 29 patients were analysed. At the time of admission to intensive care unit, elevated serum levels above the normal range for respective age group and sex were observed in 44% for activin A, 57% for activin B, and 39% for FS. In 13 of the 29 patients, serial samples at all time points were available and in these the highest activin A, activin B and FS were above the normal range in 85%, 100% and 46% of the patients, respectively. No difference in baseline or highest activin A or activin B was found in patients with or without acute lung injury (ALI) or ARDS (P > 0.05 for all). Peak levels of IL-6 were significantly elevated in ALI/ARDS patients. Peak activin A and activin A/FS were associated with ventilatory support free-days, severity of acute illness and length of ICU stay (P < 0.05 for all).

Conclusions

Higher than normal values of these proteins were common in patients with H1N1 infection but we found no association with the severity of their respiratory failure.

Reducing the burden of acute respiratory distress syndrome: the case for early intervention and the potential role of the emergency department

The mortality for acute respiratory distress syndrome (ARDS) remains unacceptably high. Success in clinical trials has been limited, resulting in a lack of effective therapies to treat the syndrome. The projected increase in mechanically ventilated patients and global need for critical care services suggests that the clinical and research landscape in ARDS can no longer be confined to the intensive care unit. A demonstrable minority of patients present to the emergency department (ED) with ARDS, and ARDS onset typically occurs shortly after intensive care unit admission. Furthermore, the ED is an entry point for many of the highest-risk patients for ARDS development and progression. These facts, combined with prolonged lengths of stay in the ED, suggest that the ED could represent a window of opportunity for treatment and preventive strategies, as well as clinical trial enrollment. This review aims to discuss some of the potential strategies that may prevent or alter the trajectory of ARDS, with a focus on the potential role the ED could play in reducing the burden of this syndrome.

Improved oxygenation 24 hours after transition to airway pressure release ventilation or high-frequency oscillatory ventilation accurately discriminates survival in immunocompromised pediatric patients with acute respiratory distress syndrome*

OBJECTIVES

Children with an immunocompromised condition and requiring invasive mechanical ventilation have high risk of death. Such patients are commonly transitioned to rescue modes of nonconventional ventilation, including airway pressure release ventilation and high-frequency oscillatory ventilation, for acute respiratory distress syndrome refractory to conventional ventilation. Our aim was to describe our experience with airway pressure release ventilation and high-frequency oscillatory ventilation in children with an immunocompromised condition and acute respiratory distress syndrome refractory to conventional ventilation and to identify factors associated with survival.

DESIGN

Retrospective cohort study.

SETTING

Tertiary care, university-affiliated PICU.

PATIENTS

Sixty pediatric patients with an immunocompromised condition and acute respiratory distress syndrome refractory to conventional ventilation transitioned to either airway pressure release ventilation or high-frequency oscillatory ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Demographic data, ventilator settings, arterial blood gases, oxygenation index, and PaO(2)/FIO(2) were recorded before transition to either mode of nonconventional ventilation and at predetermined intervals after transition for up to 5 days. Mortality in the entire cohort was 63% and did not differ between patients transitioned to airway pressure release ventilation and high-frequency oscillatory ventilation. For both airway pressure release ventilation and high-frequency oscillatory ventilation, improvements in oxygenation index and PaO(2)/FIO(2) at 24 hours expressed as a fraction of pretransition values (oxygenation index(24)/oxygenation index(pre) and PaO(2)/FIO(224)/PaO(2)/FIO(2pre)) reliably discriminated nonsurvivors from survivors, with receiver operating characteristic areas under the curves between 0.89 and 0.95 (p for all curves < 0.001). Sensitivity-specificity analysis suggested that less than 15% reduction in oxygenation index (90% sensitive, 75% specific) or less than 90% increase in PaO(2)/FIO(2) (80% sensitive, 94% specific) 24 hours after transition to airway pressure release ventilation were the optimal cutoffs to identify nonsurvivors. The comparable values 24 hours after transition to high-frequency oscillatory ventilation were less than 5% reduction in oxygenation index (100% sensitive, 83% specific) or less than 80% increase in PaO(2)/FIO(2) (91% sensitive, 89% specific) to identify nonsurvivors.

CONCLUSIONS

In this single-center retrospective study of pediatric patients with an immunocompromised condition and acute respiratory distress syndrome failing conventional ventilation transitioned to either airway pressure release ventilation or high-frequency oscillatory ventilation, improved oxygenation at 24 hours expressed as PaO(2)/FIO(224)/PaO(2)/FIO(2pre) or oxygenation index(24)/oxygenation indexpre reliably discriminates nonsurvivors from survivors. These findings should be prospectively verified.

Effects of interventions on survival in acute respiratory distress syndrome: an umbrella review of 159 published randomized trials and 29 meta-analyses

PURPOSE

Multiple interventions have been tested in acute respiratory distress syndrome (ARDS). We examined the entire agenda of published randomized controlled trials (RCTs) in ARDS that reported on mortality and of respective meta-analyses.

METHODS

We searched PubMed, the Cochrane Library, and Web of Knowledge until July 2013. We included RCTs in ARDS published in English. We excluded trials of newborns and children; and those on short-term interventions, ARDS prevention, or post-traumatic lung injury. We also reviewed all meta-analyses of RCTs in this field that addressed mortality. Treatment modalities were grouped in five categories: mechanical ventilation strategies and respiratory care, enteral or parenteral therapies, inhaled/intratracheal medications, nutritional support, and hemodynamic monitoring.

RESULTS

We identified 159 published RCTs of which 93 had overall mortality reported (n = 20,671 patients)--44 trials (14,426 patients) reported mortality as a primary outcome. A statistically significant survival benefit was observed in eight trials (seven interventions) and two trials reported an adverse effect on survival. Among RCTs with more than 50 deaths in at least one treatment arm (n = 21), two showed a statistically significant mortality benefit of the intervention (lower tidal volumes and prone positioning), one showed a statistically significant mortality benefit only in adjusted analyses (cisatracurium), and one (high-frequency oscillatory ventilation) showed a significant detrimental effect. Across 29 meta-analyses, the most consistent evidence was seen for low tidal volumes and prone positioning in severe ARDS.

CONCLUSIONS

There is limited supportive evidence that specific interventions can decrease mortality in ARDS. While low tidal volumes and prone positioning in severe ARDS seem effective, most sporadic findings of interventions suggesting reduced mortality are not corroborated consistently in large-scale evidence including meta-analyses.

Treatment with neuromuscular blocking agents and the risk of in-hospital mortality among mechanically ventilated patients with severe sepsis

OBJECTIVES

Recent trials suggest that treatment with neuromuscular blocking agents may improve survival in patients requiring mechanical ventilation for acute respiratory distress syndrome. We examined the association between receipt of a neuromuscular blocking agent and in-hospital mortality among mechanically ventilated patients with severe sepsis.

DESIGN

A pharmacoepidemiologic cohort study of patients with sepsis and a respiratory infection who had been admitted to intensive care and placed on mechanical ventilation within the first 2 days of hospitalization. We used propensity score matching and instrumental variable methods to compare the outcomes of patients treated with neuromuscular blocking agents within the first 2 hospital days to those who were not. Sensitivity analysis was used to model the effects of a hypothetical unmeasured confounder.

SETTING

Three hundred thirty-nine U.S. hospitals that participated in the Premier Perspective database between 2004 and 2006.

PATIENTS

Seven thousand eight hundred sixty-four patients met inclusion criteria, including 1,818 (23%) who were treated with a neuromuscular blocking agent by hospital day 2.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients who received neuromuscular blocking agents were younger (mean age, 62 vs 68), more likely to be treated with vasopressors (69% vs 65%) and had a lower in-hospital mortality rate (31.9% vs 38.3%, p < 0.001). In 3,518 patients matched on the propensity for treatment, receipt of a neuromuscular blocking agent was associated with a reduced risk of in-hospital mortality (risk ratio, 0.88; 95% CI, 0.80, 0.96). An analysis using the hospital neuromuscular blocking agent-prescribing rate as an instrumental variable found receipt of a neuromuscular blocking agent associated with a 4.3% (95% CI, -11.5%, 1.5%) reduction in in-hospital mortality.

CONCLUSIONS

Among mechanically ventilated patients with severe sepsis and respiratory infection, early treatment with a neuromuscular blocking agent is associated with lower in-hospital mortality.

Spontaneous effort causes occult pendelluft during mechanical ventilation

RATIONALE

In normal lungs, local changes in pleural pressure (P(pl)) are generalized over the whole pleural surface. However, in a patient with injured lungs, we observed (using electrical impedance tomography) a pendelluft phenomenon (movement of air within the lung from nondependent to dependent regions without change in tidal volume) that was caused by spontaneous breathing during mechanical ventilation.

OBJECTIVES

To test the hypotheses that in injured lungs negative P(pl) generated by diaphragm contraction has localized effects (in dependent regions) that are not uniformly transmitted, and that such localized changes in P(pl) cause pendelluft.

METHODS

We used electrical impedance tomography and dynamic computed tomography (CT) to analyze regional inflation in anesthetized pigs with lung injury. Changes in local P(pl) were measured in nondependent versus dependent regions using intrabronchial balloon catheters. The airway pressure needed to achieve comparable dependent lung inflation during paralysis versus spontaneous breathing was estimated.

MEASUREMENTS AND MAIN RESULTS

In all animals, spontaneous breathing caused pendelluft during early inflation, which was associated with more negative local P(pl) in dependent regions versus nondependent regions (-13.0 ± 4.0 vs. -6.4 ± 3.8 cm H2O; P < 0.05). Dynamic CT confirmed pendelluft, which occurred despite limitation of tidal volume to less than 6 ml/kg. Comparable inflation of dependent lung during paralysis required almost threefold greater driving pressure (and tidal volume) versus spontaneous breathing (28.0 ± 0.5 vs. 10.3 ± 0.6 cm H2O, P < 0.01; 14.8 ± 4.6 vs. 5.8 ± 1.6 ml/kg, P < 0.05).

CONCLUSIONS

Spontaneous breathing effort during mechanical ventilation causes unsuspected overstretch of dependent lung during early inflation (associated with reciprocal deflation of nondependent lung). Even when not increasing tidal volume, strong spontaneous effort may potentially enhance lung damage.