Hydrostatic mechanisms may contribute to the pathogenesis of human re-expansion pulmonary edema

Unusual severe hypoxemia due to unilateral pulmonary edema after conventional cardiopulmonary bypass salvaged by veno-venous extracorporeal membrane oxygenation: a case report

BACKGROUND

We report a case in which veno-venous extracorporeal membrane oxygenation (V-V ECMO) saved the life of a patient who developed severe hypoxemia due to unusual unilateral pulmonary edema (UPE) after cardiopulmonary bypass (CPB).

CASE PRESENTATION

A 69-year-old man underwent aortic valve replacement and coronary artery bypass grafting. Following uneventful weaning off CPB, he developed severe hypoxemia. The ratio of arterial oxygen tension to inspired oxygen fraction (PaO2/FiO2) decreased from 301 mmHg 5 min after CPB to 42 mmHg 90 min after CPB. A chest X-ray revealed right-sided UPE. Immediately established V-V ECMO increased PaO2/FiO2 to 170 mmHg. Re-expansion pulmonary edema (REPE) was likely, as the right lung remained collapsed during CPB following the accidental opening of the right chest cavity during graft harvesting.

CONCLUSIONS

V-V ECMO was effective in improving oxygenation and saving the life of a patient who had fallen into unilateral REPE unusually developing after conventional CPB.

Noncardiogenic pulmonary edema in small animals

OBJECTIVE

To review various types of noncardiogenic pulmonary edema (NCPE) in cats and dogs.

ETIOLOGY

NCPE is an abnormal fluid accumulation in the lung interstitium or alveoli that is not caused by cardiogenic causes or fluid overload. It can be due to changes in vascular permeability, hydrostatic pressure in the pulmonary vasculature, or a combination thereof. Possible causes include inflammatory states within the lung or in remote tissues (acute respiratory distress syndrome [ARDS]), airway obstruction (post-obstructive pulmonary edema), neurologic disease such as head trauma or seizures (neurogenic pulmonary edema), electrocution, after re-expansion of a collapsed lung or after drowning.

DIAGNOSIS

Diagnosis of NCPE is generally based on history, physical examination, and diagnostic imaging. Radiographic findings suggestive of NCPE are interstitial to alveolar pulmonary opacities in the absence of signs of left-sided congestive heart failure or fluid overload such as cardiomegaly or congested pulmonary veins. Computed tomography and edema fluid analysis may aid in the diagnosis, while some forms of NCPE require additional findings to reach a diagnosis.

THERAPY

The goal of therapy for all types of NCPE is to preserve tissue oxygenation and reduce the work of breathing. This may be achieved by removing the inciting cause (eg, airway obstruction) and cage rest in mild cases and supplemental oxygen in moderate cases and may require mechanical ventilation in severe cases.

PROGNOSIS

Prognosis is generally good for most causes of veterinary NCPE except for ARDS, although data are scarce for some etiologies of NCPE.

Research Progress on the Mechanism of Right Heart-Related Pulmonary Edema

Objective. To investigate the mechanisms underlying the development of right heart-associated PE. Background. Right heart-related pulmonary edema (PE) refers to PE resulting from impaired right heart function caused by primary or secondary factors, which is common in critically ill patients. Although the clinical manifestations of different types of right heart-related PE are similar, the pathophysiological changes and treatment methods are significantly different. According to the hemodynamic mechanism, right heart-related PE is primarily classified into two types. One is the increase of right heart flow, including extravascular compression, intravascular compression, cardiac compression, and cardiac decompression. The other type is the abnormal distribution of pulmonary circulation, including obstruction, resistance, pleural decompression, or negative pressure. With the development of hemodynamic monitoring, hemodynamic data not only help us understand the specific pathogenesis of right heart-related PE but also assist us in determining the direction of therapy and enabling individualized treatment. Summary. This article presents a review on right heart-associated PE, with a perspective of hemodynamic analysis, and emphasizes the importance of right heart function in the management of circulation. Understanding the mechanism of right heart-associated PE will not only aid in better monitoring right heart function but also help intensivists make a more accurate identification of various types of PE in the clinic.

Lessons from fatal re-expansion pulmonary oedema: case series

The goal of this study was to investigate the extent of the alveolar-capillary membrane porosity in patients with severe re-expansion pulmonary oedema. The biochemistry of airway fluid of two patients who died of re-expansion oedema was compared to their blood biochemistry. The airway fluid was comparable to plasma, while no blood cells were observed across the alveolar-capillary membrane. The membrane was linked to a fishnet that traps cells on one side, while plasma sieved through.

Positive pressure–assisted pleural aspiration: A case report of a novel procedure and a review of literature

Drainage of a pleural effusion is done either by inserting an intercostal tube or by aspirating pleural fluid using a syringe. The latter is a time-consuming and labour-intensive procedure. The serious complications of pleural aspiration are the development of a pneumothorax and re-expansion pulmonary oedema. We describe an observation made during a pleural aspiration in a patient who was on positive pressure ventilation. We explain the physiological basis for the observation, the safety of the procedure and its potential to reduce complications by reviewing the literature. A 56-year-old Sri Lankan female patient with end-stage kidney disease presented with fluid overload and bilateral pleural effusions. She was found to have concurrent COVID pneumonia. The patient was on bilevel positive airway pressure, non-invasive ventilation when pleural aspiration was done. The pleural fluid drained completely without the need for aspiration, once the cannula was inserted into the pleural space. One litre of fluid drained in 15 min without the patient developing symptoms or complications. Positive pressure ventilation leads to a supra-atmospheric (positive) pressure in the pleural cavity. This leads to a persistent positive pressure gradient throughout the procedure, leading to complete drainage of pleural fluid. Pleural fluid drainage in mechanically ventilated patients has been proven to be safe, implying the safety of positive pressure ventilation in pleural fluid aspiration and drainage. It further has the potential to reduce the incidence of post-aspiration pneumothorax by reducing the pressure fluctuations at the visceral pleura. Re-expansion pulmonary oedema is associated with a higher negative pleural pressure during aspiration, and the use of positive pressure ventilation can theoretically prevent re-expansion pulmonary oedema. Positive pressure ventilation can reduce the re-accumulation of the effusion as well. We suggest utilizing positive pressure ventilation to assist pleural aspiration in suitable patients.

Perioperative Pulmonary Atelectasis: Part I. Biology and Mechanisms

Pulmonary atelectasis is common in the perioperative period. Physiologically, it is produced when collapsing forces derived from positive pleural pressure and surface tension overcome expanding forces from alveolar pressure and parenchymal tethering. Atelectasis impairs blood oxygenation and reduces lung compliance. It is increasingly recognized that it can also induce local tissue biologic responses, such as inflammation, local immune dysfunction, and damage of the alveolar-capillary barrier, with potential loss of lung fluid clearance, increased lung protein permeability, and susceptibility to infection, factors that can initiate or exaggerate lung injury. Mechanical ventilation of a heterogeneously aerated lung (e.g., in the presence of atelectatic lung tissue) involves biomechanical processes that may precipitate further lung damage: concentration of mechanical forces, propagation of gas-liquid interfaces, and remote overdistension. Knowledge of such pathophysiologic mechanisms of atelectasis and their consequences in the healthy and diseased lung should guide optimal clinical management.

Unilateral pulmonary oedema after minimally invasive and robotically assisted mitral valve surgery

OBJECTIVES

Unilateral pulmonary oedema (UPO) is a severe complication of minimally invasive cardiac surgery. UPO rates and UPO-related mortality vary considerably between different studies. Due to lack of consistent diagnostic criteria for UPO, the aim of this study was to create a reproducible radiological classification for UPO. Also, risk factors for UPO after robotic and minimally invasive mitral valve operations were evaluated.

METHODS

Two hundred and thirty-one patients who underwent elective minimally invasive mitral valve surgery between January 2009 and March 2017 were evaluated. Chest radiographs of the first postoperative morning were categorized into 3 UPO grades based on the severity of radiological signs of pulmonary oedema described in this study. The radiographs were analysed by 2 independent radiologists and interobserver agreement was evaluated. The clinical significance of the classification was evaluated by comparing postoperative PaO2/FiO2 values and total ventilation times between the different UPO grades. Also, multivariable logistic regression analysis was employed to identify risk factors for UPO.

RESULTS

Interobserver agreement was substantial (Kappa = 0.780). Median total ventilation times were significantly longer with increasing severity of UPO, 15 (interquartile range 12-18) h for no UPO, 18 (interquartile range 15-24) h for grade I UPO and 25 (interquartile range 21-31) h for grade II UPO. Pulmonary hypertension [adjusted odds ratios (AOR) 2.51, 95% confidence intervals (CI) 1.43-4.40; P = 0.001], moderate or severe heart failure (AOR 2.88, 95% CI 1.27-6.53; P = 0.011), body mass index (AOR 1.14, 95% CI 1.02-1.28; P = 0.017) and cardiopulmonary bypass time (AOR 1.02, 95% CI 1.01-1.03; P < 0.001) were identified as independent risk factors for UPO and robotic approach (AOR 0.27, 95% CI 0.12-0.62; P = 0.002) as protective against UPO.

CONCLUSIONS

Due to the variability of the diagnostic criteria for UPO in previous studies, a radiological classification for UPO is required to reliably assess the rates and risk factors for UPO. The radiological classification described in this study demonstrated high interobserver agreement and correlated with total ventilation times and postoperative PaO2/FiO2 values.

Outcome of Unilateral Pulmonary Edema after Minimal-Invasive Mitral Valve Surgery: 10-Year Follow-Up

The study was approved by the institutional review board (IRB) at the University Medical Center Campus Kiel, Kiel, Germany (reference number: AZ D 559/18) and registered at the German Clinical Trials Register (reference number: DRKS00022222).

OBJECTIVE

Unilateral pulmonary edema (UPE) is a complication after minimally invasive mitral valve surgery (MIMVS). We analyzed the impact of this complication on the short- and long-term outcome over a 10-year period.

METHODS

We retrospectively observed 393 MIMVS patients between 01/2009 and 12/2019. The primary endpoint was a radiographically and clinically defined UPE within the first postoperative 24 h, secondary endpoints were 30-day and long-term mortality and the percentage of patients requiring ECLS. Risk factors for UPE incidence were evaluated by logistic regression, and risk factors for mortality in the follow-up period were assessed by Cox regression.

RESULTS

Median EuroSCORE II reached 0.98% in the complete MIMVS group. Combined 30-day and in-hospital mortality after MIMVS was 2.0% with a 95, 93 and 77% survival rate after 1, 3 and 10 years. Seventy-two (18.3%) of 393 patients developed a UPE 24 h after surgery. Six patients (8.3%) with UPE required an extracorporeal life-support system. Logistic regression analysis identified a higher creatinine level, a worse LV function, pulmonary hypertension, intraoperative transfusion and a longer aortic clamp time as predictors for UPE. Combined in hospital mortality and 30-day mortality was slightly but not significantly higher in the UPE group (4.2 vs. 1.6%; p = 0.17). Predictors for mortality during follow-up were age ≥ 70 years, impaired RVF, COPD, drainage loss ≥ 800 mL and length of ventilation ≥ 48 h. During a median follow-up of 4.6 years, comparable survival between UPE and non-UPE patients was seen in our analysis after 5 years (89 vs. 88%; p = 0.98).

CONCLUSIONS

In-hospital outcome with UPE after MIMVS was not significantly worse compared to non-UPE patients, and no differences were observed in the long-term follow-up. However, prolonged aortic clamp time, worse renal and left ventricular function, pulmonary hypertension and transfusion are associated with UPE.

Phenotypes and personalized medicine in the acute respiratory distress syndrome

Although the acute respiratory distress syndrome (ARDS) is well defined by the development of acute hypoxemia, bilateral infiltrates and non-cardiogenic pulmonary edema, ARDS is heterogeneous in terms of clinical risk factors, physiology of lung injury, microbiology, and biology, potentially explaining why pharmacologic therapies have been mostly unsuccessful in treating ARDS. Identifying phenotypes of ARDS and integrating this information into patient selection for clinical trials may increase the chance for efficacy with new treatments. In this review, we focus on classifying ARDS by the associated clinical disorders, physiological data, and radiographic imaging. We consider biologic phenotypes, including plasma protein biomarkers, gene expression, and common causative microbiologic pathogens. We will also discuss the issue of focusing clinical trials on the patient's phase of lung injury, including prevention, administration of therapy during early acute lung injury, and treatment of established ARDS. A more in depth understanding of the interplay of these variables in ARDS should provide more success in designing and conducting clinical trials and achieving the goal of personalized medicine.

Preventive Strategy for Reexpansion Pulmonary Edema After Minimally Invasive Cardiac Surgery

Reexpansion pulmonary edema is a serious complication of minimally invasive cardiac surgery through the right minithoracotomy. As reexpansion mechanical injury and ischemia reperfusion injury to the collapsed lung are possible mechanisms, we introduced a preventive protocol that consists of intermittent ventilation of the right lung, restoration of bilateral ventilation, administration of mannitol before unclamping the aorta, and institution of mild hypothermia. Among 469 patients who underwent minimally invasive cardiac surgery, we used this protocol in 379 patients. Reexpansion pulmonary edema incidence decreased significantly from 7.8% to 2.1% (P = .006). Although further evaluation is required, our protocol may be effective in preventing reexpansion pulmonary edema.

Re-expansion pulmonary edema in a patient with anorexia nervosa and delayed drainage of traumatic pneumothorax

A 21-year-old patient with anorexia developed re-expansion pulmonary edema after delayed drainage of traumatic pneumothorax. The patient was treated with non-invasive respiratory support [helmet continuous positive airway pressure (CPAP) and nasal high flow] until the resolution of the edema. Risk factors associated with re-expansion pulmonary edema are anorexia nervosa, prolonged lung collapse, age in the 20-39 range and re-expansion by high suctioning pressure.

A common gesture with a rare but potentially severe complication: Re-expansion pulmonary edema following chest tube drainage

Background

Primary Spontaneous Pneumothorax (PSP) is usually considered as a benign pathology occurring in young people. In about half of cases, observation only is purposed. In case of intervention, chest tube drainage remains the preponderant strategy even if no studies conclude about superiority of drainage or aspiration. Re-expansion pulmonary edema (REPE) is a rare but potentially severe complication of chest tube drainage. Risk factors are not well identified, but REPE is more frequent for patients with diabetes, younger than 40 years, with large pneumothorax, lung collapse more than one week and fast re-expansion.

Case report

We report a case of a 19-year old male presenting to the Emergency Department with a first episode of PSP. He was treated by chest tube drainage with immediate suction. He developed a REPE 3 hours after chest tube drainage with suction. Conservative management and oxygen therapy led to withdrawing the chest tube 9 days later.

Conclusion

For the initial management of PSP, prevention of this complication is essential. In case of risk factors, prevention consist of absence of immediate suction after chest tube drainage and suction should be reserved in case of failure of initial treatment after 24 hours. Even if chest tube drainage is a common gesture, clinical presentation of REPE must alert physicians taking care of these patients.

Liver Transplant and Reexpansion Pulmonary Edema: A Case Report

Hydrothorax occurs frequently in patients with endstage liver disease and usually requires drainage of pulmonary effusion during the hepatectomy phase of liver transplant. Reexpansion pulmonary edema is a rare but potentially fatal complication seen after rapid reexpansion of the collapsed lung following thoracentesis of pleural fluid or tube drainage of pneumothorax. This condition, which manifests with various degrees of clinical severity, is rarely reported following liver transplantation. Herein, we present a 62-year-old male patient who developed reexpansion pulmonary edema after drainage of massive pleural effusion, which caused a total collapse in the right hemithorax during liver transplant. Six hours after pleural fluid drainage, the patient developed a nonproductive cough, mild tachypnea, shortness of breath, and low oxygen saturation (88%). His chest radiograph showed diffuse heterogeneous opacities in the right hemithorax. Computed tomography of the thorax revealed consolidations containing air bronchograms and ground glass opacities in the parenchyma of the right lung; these findings did not extend to the periphery and were observed less frequently in the inferoposterior left lung. These symptoms and radiologic findings were diagnosed as reexpansion pulmonary edema. Complete clinical and radiologic improvements were achieved within 72 hours of mechanical ventilatory support.

Reexpansion Pulmonary Edema in Pediatrics

Reexpansion pulmonary edema is a rare complication that may occur after drainage of pneumothorax or pleural effusion. A number of factors have been identified that increase the risk of developing reexpansion pulmonary edema, and pathophysiologic mechanisms have been postulated. Patients may present with radiographic findings alone or may have signs or symptoms that prompt evaluation and diagnosis. Clinical presentations range from mild cough to respiratory failure and hemodynamic compromise. Treatment strategies are supportive, and should be tailored to match the severity of the condition.

Hypoxemia after pneumothorax exsufflation: a case report

We describe a 36-year-old patient who was admitted to the emergency ward for acute dyspnea due to a spontaneous pneumothorax. He was successfully drained but shortly after presented a severe hypoxemia due to pulmonary oedema secondary to pulmonary re-expansion. The physiopathology behind this complication is still unknown. We will try to describe this complication and its predictive factors.

Hepatic hydrothorax: An update and review of the literature

This review considers the modern concepts of pathogenesis, diagnostic methods, and treatment principles of hepatic hydrothorax (HH). HH is the excessive (> 500 mL) accumulation of transudate in the pleural cavity in patients with decompensated liver cirrhosis but without cardiopulmonary and pleural diseases. It causes respiratory failure which aggravates the clinical course of liver cirrhosis, and the emergence of spontaneous bacterial pleural empyema may be the cause of death. The information was collected from the PubMed database, the Google Scholar retrieval system, the Cochrane reviews, and the reference lists from relevant publications for 1994-2016 using the keywords: “liver cirrhosis”, “portal hypertension”, “hepatic hydrothorax”, “pathogenesis”, “diagnostics”, and “treatment”. To limit the scope of this review, only articles dealing with uncomplicated hydrothorax in patients with liver cirrhosis were included. The analysis of the data showed that despite the progress of modern hepatology, the presence of HH is associated with poor prognosis and high mortality. Most patients suffering from it are candidates for orthotopic liver transplantation. In routine clinical practice, stratification of the risk for an adverse outcome and the subsequent determination of individual therapeutic strategies may be the keys to the successful management of the patient’s condition. The development of pathogenetic pharmacotherapy and optimization of minimally invasive treatment will improve the quality of life and increase the survival rate among patients with HH.

Safe and Effective Bedside Thoracentesis: A Review of the Evidence for Practicing Clinicians

BACKGROUND

Physicians often care for patients with pleural effusion, a condition that requires thoracentesis for evaluation and treatment. We aim to identify the most recent advances related to safe and effective performance of thoracentesis.

METHODS

We performed a narrative review with a systematic search of the literature. Two authors independently reviewed search results and selected studies based on relevance to thoracentesis; disagreements were resolved by consensus. Articles were categorized as those related to the pre-, intra- and postprocedural aspects of thoracentesis.

RESULTS

Sixty relevant studies were identified and included. Pre-procedural topics included methods for physician training and maintenance of skills, such as simulation with direct observation. Additionally, pre-procedural topics included the finding that moderate coagulopathies (international normalized ratio less than 3 or a platelet count greater than 25,000/μL) and mechanical ventilation did not increase risk of postprocedural complications. Intraprocedurally, ultrasound use was associated with lower risk of pneumothorax, while pleural manometry can identify a nonexpanding lung and may help reduce risk of re-expansion pulmonary edema. Postprocedurally, studies indicate that routine chest X-ray is unwarranted, because bedside ultrasound can identify pneumothorax.

CONCLUSIONS

While the performance of thoracentesis is not without risk, clinicians can incorporate recent advances into practice to mitigate patient harm and improve effectiveness. Journal of Hospital Medicine 2017;12:266-276.

An uncommon complication of a common clinical scenario: exploring reexpansion pulmonary edema with a case report and literature review

Reexpansion pulmonary edema (RPE) is a rare complication that can occur after rapid reinflation of the lung following thoracentesis of a pleural effusion or chest tube drainage of pneumothorax. The severity in clinical presentation can be widely varied from radiographic changes only to rapidly progressive respiratory failure requiring mechanical ventilation. The quick nature of onset and potential for serious decline in a previously stable patient makes it important to prepare, recognize, diagnose, and appropriately manage patients who develop RPE. The standard treatment for RPE consists of supportive care, and there are certain measures that may be taken to reduce the risk, including limiting the amount drained and avoiding excessive negative pleural pressure. Exactly how to prevent RPE remains unclear, however, and varying recommendations exist. This is a case report of RPE after thoracentesis for a pleural effusion and a brief review of literature to date, including potential preventative strategies.

Complications of thoracentesis: incidence, risk factors, and strategies for prevention

PURPOSE OF REVIEW

Although thoracentesis is generally considered safe, procedural complications are associated with increased morbidity, mortality, and healthcare costs. In this article, we review the risk factors and prevention of the most common complications of thoracentesis including pneumothorax, bleeding (chest wall hematoma and hemothorax), and re-expansion pulmonary edema.

RECENT FINDINGS

Recent data support the importance of operator expertise and the use of ultrasound in reducing the risk of iatrogenic pneumothorax. Although coagulopathy or thrombocytopenia and the use of anticoagulant or antiplatelet medications have traditionally been viewed as contraindications to thoracentesis, new evidence suggests that patients may be able to safely undergo thoracentesis without treating their bleeding risk. Re-expansion pulmonary edema, a rare complication of thoracentesis, is felt to result in part from the generation of excessively negative pleural pressure. When and how to monitor changes in pleural pressure during thoracentesis remains a focus of ongoing study.

SUMMARY

Major complications of thoracentesis are uncommon. Clinician awareness of risk factors for procedural complications and familiarity with strategies that improve outcomes are essential components for safely performing thoracentesis.

Reexpansion pulmonary edema after chest drainage for pneumothorax: A case report and literature overview

Background

Reexpansion pulmonary edema (RPE) is a rare complication that may occur after treatment of lung collapse caused by pneumothorax, atelectasis or pleural effusion and can be fatal in 20% of cases. The pathogenesis of RPE is probably related to histological changes of the lung parenchyma and reperfusion-damage by free radicals leading to an increased vascular permeability. RPE is often self-limiting and treatment is supportive.

Case report

A 76-year-old patient was treated by intercostal drainage for a traumatic pneumothorax. Shortly afterwards he developed reexpansion pulmonary edema and was transferred to the intensive care unit for ventilatory support. Gradually, the edema and dyspnea diminished and the patient could be discharged in good clinical condition.

Conclusion

RPE is characterized by rapidly progressive respiratory failure and tachycardia after intercostal chest drainage. Early recognition of signs and symptoms of RPE is important to initiate early management and allow for a favorable outcome.

Determining the aetiology of pulmonary oedema by the oedema fluid-to-plasma protein ratio

We hypothesised that the oedema fluid-to-plasma protein (EF/PL) ratio, a noninvasive measure of alveolar capillary membrane permeability, can accurately determine the aetiology of acute pulmonary oedema. 390 mechanically ventilated patients with acute pulmonary oedema were enrolled. A clinical diagnosis of acute lung injury (ALI), cardiogenic pulmonary oedema or a mixed aetiology was based on expert medical record review at the end of hospitalisation. The EF/PL ratio was measured from pulmonary oedema fluid and plasma samples collected at intubation. 209 patients had a clinical diagnosis of ALI, 147 had a diagnosis of cardiogenic pulmonary oedema and 34 had a mixed aetiology. The EF/PL ratio had an area under the receiver-operating curve of 0.84 for differentiating ALI from cardiogenic pulmonary oedema. Using a predefined cut-off of 0.65, the EF/PL ratio had a sensitivity of 81% and a specificity of 81% for the diagnosis of ALI. An EF/PL ratio >/=0.65 was also associated with significantly higher mortality and fewer ventilator-free days. Noninvasive measurement of the EF/PL ratio is a safe and reliable bedside method for rapidly determining the aetiology of acute pulmonary oedema that can be used at the bedside in both developed and developing countries.

Delayed onset of contralateral pulmonary edema following reexpansion pulmonary edema of a collapsed lung after video-assisted thoracoscopic surgery

This case report describes a 61-year-old man who developed reexpansion pulmonary edema (RPE) of the collapsed left lung after video-assisted thoracoscopic surgery because of left thoracic empyema, complicated with secondary contralateral pulmonary edema later. The left lung was gently reexpanded after surgery under one-lung ventilation anesthesia for 2.5 hours. The patient developed RPE of the left lung immediately after surgery, and required mechanical ventilation with positive end-expiratory pressure support. RPE was resolved within 24 hours. Nevertheless, delayed onset of contralateral pulmonary edema manifested on chest radiography 4 days later without clinical symptoms such as tachypnea or dyspnea. There was no evidence of pulmonary infection, fluid overload, postoperative renal insufficiency or cardiogenic onslaught. Late manifestation of contralateral pulmonary edema in the wake of previous left-sided RPE was suspected from exclusion of possible culprits. Response to steroid therapy made inflammation-related pulmonary edema a likely diagnosis. This case demonstrates that delayed contralateral pulmonary edema with only radiographic evidence can emerge 4 days after resolution of RPE of a collapsed lung. Methods to prevent RPE and management of one-lung ventilation are described.

Postobstructive pulmonary edema: a case for hydrostatic mechanisms

BACKGROUND

Postobstructive pulmonary edema is a well-recognized complication of upper airway obstruction. The mechanisms of edema formation are unclear and may be due to increased hydrostatic forces generated by high negative inspiratory pressure or by increased permeability of the alveolar capillary membrane. Measurement of the edema fluid/plasma protein ratio and the rate of net alveolar fluid clearance are two well-validated methods for classifying the underlying mechanism of edema formation. The goal of the current study was to investigate the mechanisms of pulmonary edema formation in patients with postobstructive pulmonary edema by serial sampling of undiluted pulmonary edema fluid.

METHODS

A retrospective review of 341 patients who had pulmonary edema fluid collected prospectively after the acute onset of pulmonary edema. All patients had serial samples of edema fluid and plasma collected over the first 8 h after intubation.

RESULTS

Ten of the 341 patients with acute pulmonary edema were identified as having postobstructive pulmonary edema. The mean (+/- SD) edema fluid/plasma protein ratio in these patients was 0.54 +/- 0.15. The mean rate of alveolar fluid clearance over 8 h was 14.0 +/- 17.4% per hour. Nine of the 10 patients survived the hospitalization.

CONCLUSION

Measurement of the edema fluid/plasma protein ratio and the presence of net alveolar fluid clearance in 10 patients with postobstructive pulmonary edema supports a hydrostatic mechanism for edema fluid formation. The predominantly fast rates of alveolar fluid clearance may explain the rapid resolution of clinical postobstructive pulmonary edema that is typically described.

Conceptos actuales en la fisiopatología, monitorización y resolución del edema pulmonar

Pulmonary edema, both in its lesional as well as hydrostatic version, is a frequent cause of acute respiratory failure. From the pathophysiological point of view, the most important advance is undoubtedly the knowledge that the reabsorption process of pulmonary edema is an active process with energy consumption. This concept has revolutionized this field due to the possibility of finding substances or factors that stimulate or inhibit this reabsorption. Furthermore, in the monitoring field, significant advances have also been experimented due to the possibility of quantifying the edema in a simple and reliable way with transpulmonary thermodilution.

Effects of budesonide and N-acetylcysteine on acute lung hyperinflation, inflammation and injury in rats

Leukocyte activation and production of inflammatory mediators and reactive oxygen species are important in the pathogenesis of lipopolysaccharide (LPS)-induced acute lung injury. The present study investigated acute lung hyperinflation, edema, and lung inflammation 4 h after an intratracheal instillation of LPS (0.5, 2.5, 5, 10, 50, 100, 500, 1000, and 5000 microg/ml/kg). Effects of budesonide, an inhaled anti-inflammatory corticosteroids, and N-acetylcysteine (NAC), an antioxidant, were evaluated in Wistar rats receiving either low (2.5 microg/ml/kg) or high (50 microg/ml/kg) concentrations of LPS. This study demonstrates that LPS in a concentration-dependent pattern induces acute lung hyperinflation measured by excised lung gas volume (25-45% above control), lung injury indicated by increased lung weight (10-60%), and lung inflammation characterized by the infiltration of leukocytes (40-14000%) and neutrophils (80-17000%) and the production of cytokines (up to 2700%) and chemokines (up to 350%) in bronchoalveolar lavage fluid (BALF). Pretreatment with NAC partially prevented tumor necrosis factor alpha (TNFalpha) production induced by the low concentration of LPS, while pretreatment with budesonide totally prevented the increased production of TNFalpha, interleukin (IL)-1beta, IL-6, and monocyte chemoattractive protein (MCP)-1 after LPS challenge at both low and high concentrations. Budesonide failed to prevent BALF levels of macrophage inflammatory protein (MIP)-2 and cytokine-induced neutrophil chemoattractant 1 (GRO/CINC-1) as well as lung hyperinflation induced by both low and high concentrations of LPS. Pretreatment with budesonide totally prevented the formation of lung edema at the low concentration of LPS and had partial effects on acute lung injury and leukocyte influx at the high concentrations. Thus, our data indicate that therapeutic effects of budesonide and NAC are dependent upon the severity of the disease.