Surfactant therapy for acute lung injury and acute respiratory distress syndrome

This article examines exogenous lung surfactant replacement therapy and its usefulness in mitigating clinical acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Surfactant therapy is beneficial in term infants with pneumonia and meconium aspiration lung injury, and in children up to age 21 years with direct pulmonary forms of ALI/ARDS. However, extension of exogenous surfactant therapy to adults with respiratory failure and clinical ALI/ARDS remains a challenge. This article reviews clinical studies of surfactant therapy in pediatric and adult patients with ALI/ARDS, focusing on its potential advantages in patients with direct pulmonary forms of these syndromes.     

Surfactant therapy for acute lung injury/acute respiratory distress syndrome

PURPOSE OF REVIEW: Currently, three phase III surfactant replacement trials for acute lung injury (ALI)/acute respiratory distress syndromes (ARDS) patients are underway. Although the efficacy of surfactant replacement therapy will first have to be proved in these phase III trials, recent reports indicate some enticing possibilities for the future of surfactant therapy. RECENT FINDINGS: Patients requiring mechanical ventilation show alterations in their endogenous surfactant composition. Depending on the type of lung injury or the elapsed time, modifications to surfactant preparations could enhance the efficacy of these preparations. Surfactants that closely resemble natural surfactant, especially those containing surfactant proteins (SP-B/C) and nonphospholipids (cholesterol), are able to restore normal surfactant physiology. Furthermore, lipids that are able to withstand degradation by lipases could further enhance surfactant therapy. SUMMARY: If surfactant therapy fulfills the promises expected from the ongoing phase III trials, future surfactant preparations may even enhance therapy efficacy and restore the altered endogenous surfactant pool as soon as possible.     

Surfactant replacement therapy in acute respiratory distress syndrome from viral pneumonia

A modified natural surfactant was administered to a patient with life-threatening adult respiratory distress sydrome caused by viral pneumonia. Subsequently, there was a marked improvement in gas exchange. In order to assess the mechanism for improved oxygenation, computed tomography of the lungs was done. Quantitative analysis of the scans taken before and after surfactant administration indicates that improvement in gas exchange was largely due to the expansion of underinflated and collapsed lung areas. Although this is a single case report, it provides insight into the possible beneficial effect of instilled surfactant in severe respiratory distress from viral pneumonia.     

Surfactant therapy in adults with acute lung injury/acute respiratory distress syndrome

PURPOSE OF REVIEW: Several phase II and phase III studies have been performed to investigate safety, efficacy and the improvement of survival due to exogenous surfactant instillation in patients with acute lung injury or acute respiratory distress syndrome. In this review we will discuss the most recent of these studies, paying particular attention to differences in the composition of the exogenous surfactant used, the diverse modes of delivery and dose of therapy and the influence of mechanical ventilation. RECENT FINDINGS: Several phase II studies performed on patients with acute lung injury or acute respiratory distress syndrome and a phase III study performed on a pediatric population have shown beneficial effects of surfactant on oxygenation and survival. No effect of exogenous surfactant has been shown on survival in phase III studies in adult patients. SUMMARY: The changes in the surfactant system of patients with acute lung injury and acute respiratory distress syndrome form the rationale for the instillation of exogenous surfactant. There is enough evidence to use surfactant instillation for pediatric patients with acute lung injury. Due to the results of the randomized controlled trials performed so far, however, exogenous surfactant is not recommended for routine use in patients with acute lung injury or acute respiratory distress syndrome. In the future, other surfactants with different compositions may show beneficial effects.     

Pediatric acute respiratory distress syndrome

The data available to guide clinical management of acute lung injury and acute respiratory distress syndrome are much more limited for infants and children than for adult patients. This paper reviews the available medical data and the pertinent physiology on the management of pediatric patients with acute lung injury. With the collaboration of multicenter investigation networks, definitive pediatric data may be on the horizon to better guide our clinical practice.     

The acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) is an important cause of acute respiratory failure that is often associated with multiple organ failure. Several clinical disorders can precipitate ARDS, including pneumonia, sepsis, aspiration of gastric contents, and major trauma. Physiologically, ARDS is characterized by increased permeability pulmonary edema, severe arterial hypoxemia, and impaired carbon dioxide excretion. Based on both experimental and clinical studies, progress has been made in understanding the mechanisms responsible for the pathogenesis and the resolution of lung injury, including the contribution of environmental and genetic factors. Improved survival has been achieved with the use of lung-protective ventilation. Future progress will depend on developing novel therapeutics that can facilitate and enhance lung repair.     

Imaging in acute respiratory distress syndrome

Purpose

Imaging has become increasingly important across medical specialties for diagnostic, monitoring, and investigative purposes in acute respiratory distress syndrome (ARDS).

Methods

This review addresses the use of imaging techniques for the diagnosis and management of ARDS as well as gaining knowledge about its pathogenesis and pathophysiology. The techniques described in this article are computed tomography, positron emission tomography, and two easily accessible imaging techniques available at the bedside—ultrasound and electrical impedance tomography (EIT).

Results

The use of computed tomography has provided new insights into ARDS pathophysiology, demonstrating that ARDS does not homogeneously affect the lung parenchyma and that lung injury severity is widely distributed in the ARDS population. Positron emission tomography is a functional imaging technique whose value resides in adding incremental insights to morphological imaging. It can quantify regional perfusion, ventilation, aeration, lung vascular permeability, edema, and inflammation. Lung ultrasound and EIT are radiation-free, noninvasive tools available at the bedside. Lung ultrasound can provide useful information on ARDS diagnosis when x-rays or CT scan are not available. EIT is a useful tool to monitor lung ventilation and to assess the regional distribution of perfusion.

Conclusions

The future of imaging in critical care will probably develop in two main directions: easily accessible imaging techniques that can be used at the bedside and sophisticated imaging methods that will be used to aid in difficult diagnostic cases or to advance our understanding of the pathogenesis and pathophysiology of an array of critical illnesses.

     

Imaging of acute respiratory distress syndrome

Chest radiography and computed tomography (CT) have a crucial role to play in the diagnosis and management of acute respiratory distress syndrome (ARDS). The identification of pulmonary opacification is a requirement for the definition of ARDS on the chest radiograph, while CT has a role to play, not only in the diagnosis of ARDS, but also in the identification of complications. This paper reviews the radiological appearances of ARDS that have been documented for some time, and also more recent research that has identified a role for CT in directing ventilation and in prognostication.     

机械通气与急性呼吸窘迫综合征

经过多年来对机械通气认识水平的提高与操作技能的发展,机械通气已经成为临床常用的治疗方法,尤其是在对急性肺损伤/急性呼吸窘迫综舍征(ALI/ARDS)的治疗过程中,已经得到了较为广泛的共识和普遍的应用.ALI与ARDS在重症患者中仍然具有非常高的发病率和相关病死率,也因在最近一些公共医疗卫生重大事件中作为影响预后的主要因素,而被广为关注.     

An evidence-based approach to acute respiratory distress syndrome.

We provide an evidence-based approach to managing patients with acute lung injury and acute respiratory distress syndrome (ARDS). We searched MEDLINE and the Cumulative Index to Nursing and Allied Health for randomized trials evaluating lung-protective ventilation strategies, inhaled nitric oxide, prone positioning, and late-phase corticosteroids for managing these patients, and for additional literature related to long-term follow-up of ARDS survivors. The results of our review suggest that pressure- and volume-limited ventilation, according to the ARDS Network protocol, can reduce mortality for patients with acute lung injury, and so may an "open lung" approach to mechanical ventilation. Those 2 strategies are currently being compared in 2 multicenter randomized trials. Although both inhaled nitric oxide therapy and prone positioning can produce dramatic acute improvements in oxygenation for some patients, there is no evidence that these interventions can benefit patients with respect to patient-important outcomes. Therefore it is unreasonable to be dogmatic about the role of inhaled nitric oxide and prone positioning in ARDS. The role of corticosteroids in the late phase of ARDS is unclear and remains a very important unanswered question. With respect to long-term follow-up, we found that pulmonary dysfunction is probably not a major source of morbidity for ARDS survivors, whereas neuropsychological dysfunction is prominent. Ongoing research may suggest interventions to improve the outcome of ARDS and of critical illness in general.     

急性呼吸窘迫综合征发病中的细胞因子和炎性介质

研究表明 ,引起急性呼吸窘迫综合征 ( ARDS)的各种情况 ,均能触发由多种效应细胞〔包括巨噬细胞、中性粒细胞( PMN)、肺泡毛细血管内皮细胞与血小板等〕、炎症介质和细胞因子参与的反应 〔1〕。全身炎症反应综合征 ( SIRS)是导致多器官功能障碍综合征 ( MODS)的根本原因 ,ARDS是 SIRS的肺部表现〔2〕。目前已注意到 ,在许多致病因素作用下肺泡单核巨噬细胞和中性粒细胞最早产生补体 C5 a、肿瘤坏死因子α( TNFα)、白介素 1β( IL 1β)起动了炎症的级联反应 ( cascade) ,它们再刺激肺内多种细胞因子 ,介导外周循环的炎症细胞迁…     

Nonventilatory interventions in the acute respiratory distress syndrome

Acute respiratory distress syndrome was first described in 1967. Acute respiratory distress syndrome and acute lung injury are diseases the busy intensivist treats almost daily. The etiologies of acute respiratory distress syndrome are many. A significant distinction is based on whether the insult to the lung was direct, such as in pneumonia, or indirect, such as trauma or sepsis. Strategies for managing patients with acute respiratory distress syndrome/acute lung injury can be subdivided into 2 large groups, those based in manipulation of mechanical ventilation and those based in nonventilatory modalities. This review focuses on the nonventlilatory strategies and includes fluid restriction, exogenous surfactant, inhaled nitric oxide, manipulation of production, or administration of eicosanoids, neuromuscular blocking agents, prone position ventilation, glucocorticoids, extracorporeal membrane oxygenation, and administration of beta-agonists. Most of these therapies either have not been studied in large trials or have failed to show a benefit in terms of long-term patient mortality. Many of these therapies have shown promise in terms of improved oxygenation and may therefore be beneficial as rescue therapy for severely hypoxic patients. Recommendations regarding the use of each of these strategies are made, and an algorithm for implementing these strategies is suggested.     

Kinetic therapy for acute respiratory distress syndrome

The authors evaluated the clinical and physiological effects of kinetic therapy (KT) in the treatment of acute respiratory distress syndrome (ARDS). Forty-six patients with ARDS underwent successive postural positioning in accordance with two regimens: 1) lateral, prone, contralateral, supine positions; 2) prone, lateral, contralateral, supine positions. The criterion for changing each position was the change in monitoring indices: SpO2, PaO2, and thoracopulmonary compliance (C). KT was performed until a respirator was withdrawn from the patient. In 25 patients, each maneuver of positioning was made during 30-minute propofol sedation. The control group included 24 patients with ARDS who received neither KT nor propofol sedation. KT caused a decrease in Vd/Vt, Qs/Qt and an increase in PaO2/FiO2 and C was more intensive, as compared with the control group. The duration of the patient's prone position was 3.2-0.7 hours and that of the supine position was 3.4-0.8 hours. The right and left lateral positions lasted 1.1-0.2 and 1.3-0.2 hours, respectively. KT regimen 1 was found to be more effective than KT regimen 2. Propofol sedation enhanced the efficiency of KT. The latter reduced death rates in patients with ARDS.