The adult respiratory distress syndrome

Are bilateral tibial shaft fractures associated with an increased risk for adverse outcome?

INTRODUCTION

Long bone fractures are assumed to be an independent risk factor for systemic complications and death after trauma. Multiple studies have identified an increased risk for mortality and morbidity in patients with bilateral femoral fractures. Data about bilateral tibial shaft fractures is rare. The aim of our study was to analyze if patients with bilateral tibial shaft fractures are at higher risk for systemic complications.

METHODS

We performed a retrospective analysis of the TraumaRegister DGU® from 1993 to 2008. Inclusion criteria were unilateral or bilateral tibial shaft fractures and an age ≥16. Additionally to the overall collective we analyzed different subgroups (divided into different injury severities and treatment periods).

RESULTS

1899 patients with unilateral and 175 patients with bilateral tibial shaft fractures were included. Age, gender and mean ISS (25.8 vs. 26.2, p = 0.51) in the two groups were comparable. Regarding the entire study population, patients with bilateral tibial shaft fractures showed no significant higher incidence of respiratory organ failure (29.5% vs. 23.1%, p = 0.076) or mortality (20.0% vs. 16.3%, p = 0.203). However, subgroup analysis showed a significant higher rate of pulmonary organ failure for bilateral tibial shaft fractures as compared to unilateral tibial shaft fractures in the group ISS < 25 (20.7% vs. 11.7%, p = 0.023). Multivariate regression analysis identified the additional tibial shaft fracture as an independent risk factor for pulmonary organ failure (OR = 1.56) but not for mortality.

DISCUSSION

The additional tibial shaft fracture is an independent risk factor for pulmonary organ failure but not for multiple organ failure or mortality. The impact of the additional tibial shaft fracture is especially pronounced in less severely injured patients (ISS < 25). These findings are comparable to results of bilateral femoral fracture studies and we therefore suggest to treat patients with bilateral tibial shaft fractures with the same caution as those with bilateral femoral fractures.

Increased morbidity and mortality after bilateral femoral shaft fractures: myth or reality in the era of damage control?

INTRODUCTION

Bilateral femoral shaft fractures have been reported to be an independent risk factor for morbidity and mortality; however, the value of these studies is limited due to small sample sizes and the timing of these studies before the establishment of damage control orthopaedics. The objective of this study was to compare the incidence of morbidity and mortality in patients with bilateral vs. unilateral femoral shaft fractures in the era of damage control orthopaedics.

METHODS

Retrospective analysis of the TraumaRegister DGU from 2002 to 2005. Inclusion criteria were uni- or bilateral femoral shaft fractures and complete demographic data documentation. Univariate data analysis and logistic regression analysis were performed with SPSS.

RESULTS

Between 2002 and 2005, 776 patients with unilateral and 118 patients with bilateral femoral shaft fractures were identified. Patients with bilateral femoral shaft fractures had a significantly higher Injury Severity Score (ISS) (29.5 vs. 25.7 points), a significantly higher incidence of pulmonary (34.7% vs. 20.6%) and multiple organ failure (25.0% vs. 14.6%) as well as a significantly higher mortality rate (16.9% vs. 9.4%). In the overall patient population, early total care (ETC) was significantly more often performed in patients with unilateral femoral shaft fractures (50.9% vs. 33.6%). Logistic regression analysis revealed no significant association between bilateral femoral shaft fractures and multiple organ failure or mortality; however, bilateral femoral shaft fractures are an independent risk factor for pulmonary failure. Subgroup analysis revealed that the impact of the bilateral femoral shaft fracture was especially pronounced in patients with an ISS<25 points.

DISCUSSION

Bilateral femoral shaft fractures are an independent risk factor for pulmonary failure but not for multiple organ failure or mortality. The impact of the additional femoral shaft fracture for pulmonary failure appears to be especially pronounced in the less severely injured patients, whose injuries are often underestimated when stratified with the ISS. Patients with bilateral femoral shaft fractures have significantly more often severe abdominal injuries as well as severe blood loss which may account for the increased mortality rate. Therefore, the presence of bilateral femoral shaft fractures should be recognised as an increased risk for systemic complications.

Pressure and volume limited ventilation for the ventilatory management of patients with acute lung injury: a systematic review and meta-analysis

BACKGROUND

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life threatening clinical conditions seen in critically ill patients with diverse underlying illnesses. Lung injury may be perpetuated by ventilation strategies that do not limit lung volumes and airway pressures. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing pressure and volume-limited (PVL) ventilation strategies with more traditional mechanical ventilation in adults with ALI and ARDS.

METHODS AND FINDINGS

We searched Medline, EMBASE, HEALTHSTAR and CENTRAL, related articles on PubMed™, conference proceedings and bibliographies of identified articles for randomized trials comparing PVL ventilation with traditional approaches to ventilation in critically ill adults with ALI and ARDS. Two reviewers independently selected trials, assessed trial quality, and abstracted data. We identified ten trials (n = 1,749) meeting study inclusion criteria. Tidal volumes achieved in control groups were at the lower end of the traditional range of 10-15 mL/kg. We found a clinically important but borderline statistically significant reduction in hospital mortality with PVL [relative risk (RR) 0.84; 95% CI 0.70, 1.00; p = 0.05]. This reduction in risk was attenuated (RR 0.90; 95% CI 0.74, 1.09, p = 0.27) in a sensitivity analysis which excluded 2 trials that combined PVL with open-lung strategies and stopped early for benefit. We found no effect of PVL on barotrauma; however, use of paralytic agents increased significantly with PVL (RR 1.37; 95% CI, 1.04, 1.82; p = 0.03).

CONCLUSIONS

This systematic review suggests that PVL strategies for mechanical ventilation in ALI and ARDS reduce mortality and are associated with increased use of paralytic agents.

Pulmonary pathology of acute respiratory distress syndrome

Lung morphology in ARDS reflects the rapid evolution from interstitial and alveolar edema to end-stage fibrosis consequent to injury of the alveolocapillary unit. This morphologic progression, termed diffuse alveolar damage, has been subdivided into sequentially occurring exudative, proliferative, and fibrotic phases. Pulmonary lesions correlate with the phase of alveolar damage rather than its specific cause. The pathologic features are consistent with the effects of a host of injurious stimuli and the complex interaction of inflammatory mediators on alveolar epithelial and capillary endothelial cells. Although ARDS frequently culminates in "interstitial" fibrosis, the organization of intraluminal exudate dominates the histologic picture in the proliferative phase and establishes the framework for subsequent fibrous remodeling of the lung. Involvement of the pulmonary vasculature is an important aspect of ARDS, from the initial phase of edema to the terminal stage of intractable pulmonary hypertension. Vascular lesions include thrombotic, fibroproliferative, and obliterative changes that, like the parenchymal lesions, correlate with the temporal phase of DAD. Although ARDS is characterized by extensive bilateral lung involvement, alveolar damage can also affect the lung in a localized fashion. RAD is associated with the same clinical risk factors as DAD, suggesting that there is a spectrum in the extent of lung involvement and disease severity in patients at risk for ARDS. The factors that govern which patients will develop the fulminant syndrome are poorly understood. It must be re-emphasized that the lung is stereotyped in its response to injury and, consequently, descriptive, or even quantitative, studies of lung morphology can only provide clues regarding the initiating factors and pathogenetic mechanisms of ARDS. Progress in understanding the pathogenesis of ARDS and development of rational approaches to therapy will ultimately depend on careful clinical and experimental studies and the application of immunohistochemical and molecular biology techniques to unravel basic mechanisms of cellular injury and response.

Mortality in patients with bilateral femoral fractures

OBJECTIVES

To determine and compare the mortality rates of patients with bilateral versus unilateral femoral fractures and to determine the contribution of the femoral fracture to, and identify risk factors for, such mortality.

STUDY DESIGN

Retrospective analysis using trauma registry data on consecutive blunt trauma patients with unilateral (800 patients, group I) or bilateral (eighty-five patients, group II) femoral fractures.

METHODS

Univariate data analysis was performed to compare the groups' ages, Injury Severity Scores, Glasgow Coma Scale values, mortality, and the presence of adult respiratory distress syndrome (ARDS). Logistic regression analysis was performed to determine variables statistically associated with mortality.

RESULTS

Group II patients had a significantly higher Injury Severity Score (30.2 versus 24.5, p < 0.001), lower Glasgow Coma Scale value (12.3 versus 13.1, p = 0.05), higher mortality rate (25.9 vs 11.7%, p < 0.001), and higher incidence of ARDS (15.7 versus 7.27%, p = 0.014) than group I patients. Group II patients also had significantly more closed head injuries, open skull fractures, intraabdominal injuries requiring surgical intervention, and pelvic fractures; the rates of thoracic injury were similar. Regression analysis of variables evident on admission revealed a significant correlation between bilateral femoral fractures and death; however, other factors (shock, closed head injury, and thoracic injury) had much stronger correlations with mortality.

CONCLUSIONS

Patients with bilateral femoral fractures have a significantly higher risk of death, ARDS, and associated injuries than patients with unilateral femoral fractures. This increase in mortality is more closely related to associated injuries and physiologic parameters than to the presence of bilateral femoral fractures. The presence of bilateral femoral fractures should alert the clinician to the likelihood of associated injuries, a higher Injury Severity Score, and the potential for a more serious prognosis.

High-level positive end expiratory pressure management in the surgical patient with acute respiratory distress syndrome

Although the exact incidence of ARDS is not know, it is frequently reported that there are 150,000 cases in the United States each year. Despite major advances in medical and respiratory intensive care, the mortality for patients with ARDS remains exceedingly high and has not changed appreciably from the 50% to 75% reported during the last 25 years. Currently there is no widespread, acceptable, specific therapeutic approach or agent available for the prevention or treatment of ARDS. Clinical management remains entirely supportive in nature. Although most practitioners agree that patients with severe ARDS require mechanical ventilation to maintain adequate gas exchange, controversies center on the amount of supplemental oxygen, level of positive end expiratory pressure (PEEP), and mode of ventilation needed to increase patient survival but reduce ventilator-associated complications. This review provides supportive evidence for the use of high-level PEEP (more than 15 cm H20) in the care of the surgical patient with severe ARDS.

The adult respiratory distress syndrome: a review

The adult respiratory distress syndrome, characterized by hypoxemia, reduced pulmonary expansion, and noncardiogenic pulmonary edema, is a clinical entity with a high mortality rate that has been recognized only relatively recently. We present the newest aspects of the subject.

Medical complications of head injury

There are many common and significant medical complications of head injury. These include (1) cardiovascular problems such as hyperdynamic state, myocardial injury, and dysrhythmias; (2) respiratory changes such as neurogenic pulmonary edema, hypoxia, abnormal ventilatory patterns, pulmonary infections, and pulmonary emboli secondary to deep vein thrombosis; (3) consumption coagulopathy; (4) water and electrolyte derangements--hypo- and hypernatremia; (5) hypothalamic/pituitary dysfunction--syndrome of inappropriate secretion of antidiuretic hormone and diabetes insipidus; (6) increased general metabolism with loss of immunocompetence, respiratory compromise, and complications of decreased activity; (7) gastrointestinal difficulties, particularly stress gastritis; and (8) infectious problems including those related to contamination from open wounds and foreign bodies such as monitors.

An early test of survival in patients with the adult respiratory distress syndrome. The PaO2/FIo2 ratio and its differential response to conventional therapy. Prostaglandin E1 Study Group

Patients with established adult respiratory distress syndrome (ARDS) have a mortality rate that exceeds 50 percent. We analyzed the magnitude of hypoxemia as manifest by the PaO2/FIO2 ratio and its early response to conventional therapy including positive end-expiratory pressure (PEEP) in the placebo group of a large multicenter study. The PaO2/FIO2 ratio was not different at the time of diagnosis of ARDS in those patients who lived compared to those who subsequently died. After one day of conventional therapy including PEEP, those patients who survived increased their PaO2/FIO2 ratio. The nonsurvivors did not improve over a seven-day course. The difference in the PaO2/FIO2 ratio was significant throughout the seven-day observation period. We conclude that the early response to conventional therapy picks a patient population with a good prognosis and can be used as a test of likely survival from ARDS.

Roles of the neutrophil and other mediators in adult respiratory distress syndrome

The adult respiratory distress syndrome (ARDS) and transfusion-related acute lung injury (TRALI) are characterized by diffuse, acute lung injury. Most likely, TRALI is a type of ARDS although it is associated with a much lower morbidity and mortality than found with classic ARDS. For years, the pathogenesis of ARDS has been explained by the complement hypothesis in which pulmonary neutrophilic sequestration and degranulation follow complement-mediated neutrophil chemotaxis. A definitive role for the neutrophil in diffuse, acute lung injury, however, has not been established. Although numerous chemoattractants for neutrophils are generated in the lungs and, through degranulation and formation of toxic oxygen free radicals, the neutrophil is fully capable of causing tissue injury, substantial evidence refutes the requirement for neutrophils in diffuse, acute lung injury. Other potential factors in the pathogenesis of ARDS include primary endothelial cell injury, alveolar macrophage activity, and hemostatic disorders.

Randomized double-blind, multicenter study of prostaglandin E1 in patients with the adult respiratory distress syndrome. Prostaglandin E1 Study Group

Prostaglandin E1 (PGE1) was compared to placebo in a 100-patient (50 PGE1, 50 placebo) randomized, double-blind, clinical trial to determine whether PGE1 therapy enhances survival of patients with adult respiratory distress syndrome (ARDS) when infused through a central line at 30 ng/kg/min continuously for seven days. At 30 days postinfusion, 30 PGE1 and 24 placebo patients had died. Total deaths judged to be related to the syndrome were 32 and 28 in the PGE1 and placebo groups respectively at six months. We conclude that PGE1 did not enhance survival in patients with established ARDS. PGE1 augmented the hyperdynamic circulation of these patients by reducing systemic and pulmonary vascular resistance, which resulted in a reduction of blood pressures and increased stroke volume, cardiac output, and heart rate. An improvement in oxygen availability and oxygen consumption was observed with PGE1 therapy. PGE1 was associated with an increased incidence of diarrhea (six patients in the PGE1 group vs one in the placebo group, p less than 0.05). Other adverse effects included hypotension (ten patients in the PGE1 group vs seven in the placebo group), fever (six patients in the PGE1 group vs three in the placebo group), and non-fatal dysrhythmias (ten in the PGE1 group vs five in the placebo group).

Hypotension in severe tricyclic antidepressant overdose

Sixty four patients who presented to the emergency department following severe acute tricyclic antidepressant (TCA) overdose (defined as an antidepressant ingestion associated with a QRS interval greater than or equal to 0.10 seconds, TCA level greater than or equal to 500 ng/mL, or grade IV coma) were prospectively evaluated to determine the incidence of hypotension and the factors associated with its development. Among these patients, the mean antidepressant level was 1,094 ng/mL. The overall frequency of admission hypotension (systolic BP less than 95 mmHg) was 34% (22 of 64 patients). Using regression analysis, systolic BP showed poor correlation with TCA level (r = -.37) and maximal QRS interval (r = -.17) following severe TCA overdose. Using multivariate analysis with a logistic regression model, the influence of BP (as well as TCA level, QRS interval, and coingestion of another drug) was evaluated on four clinical outcomes: seizures, arrhythmias, aspiration pneumonia, and pulmonary edema. The occurrence of arrhythmias and pulmonary edema was significantly associated (inversely) with hypotension (P less than .01). Seizures and aspiration pneumonia were unrelated to admission BP. These results suggest that hypotension is common after severe TCA overdose and occurs independently of TCA level and prolongation of the QRS interval. Hypotension is strongly associated with the development of arrhythmias and pulmonary edema. Seizures and aspiration pneumonia may occur regardless of initial BP.

Toxic pneumonitis in an adolescent following exposure to Snow Storm tablets

Adolescence is often a time when experimentation with alcohol, cigarette smoking, and substance abuse occur. We report a rare complication of smoking, toxic pneumonitis, in an adolescent female who combined an over-the-counter novelty item, Snow Storm tablets, with cigarettes.

Pulmonary macrophage antimicrobial activity in canine endotoxin shock and lung injury

Bacterial sepsis and pneumonia are common complications of lung injury and predispose the host to a poor resolution. We studied the functional integrity of pulmonary macrophages derived from minced lung preparations in a canine model of endotoxin-induced shock with acute lung injury. Dogs given 2 mg/kg of Escherichia coli endotoxin 055:B5 developed classic shock symptoms with concomitant acute lung injury; control animals given saline showed no physiological or pathological abnormalities. Compared to previous work with this canine model, the lung injury in this extended time period (6 h) had progressed to include alveolar edema. Six hours after endotoxin infusion, the left lung was lavaged, perfused, and the resulting lung minced for isolation of pulmonary macrophages. The endotoxic-model pulmonary macrophages showed several significant functional differences from controls. Although they elicited greater production of H2O2 (p less than 0.05), both phagocytosis of radiolabeled Staphylococcus aureus and E. coli (p less than 0.05) and bactericidal activity (p less than 0.05) were diminished compared to controls. Compared to alterations previously described in alveolar macrophages, these cells produced less H2O2 and demonstrated abnormal bacterial killing at all time points. These observations suggest that the functional alterations of pulmonary macrophages that follow acute lung injury contribute to the ineffective cell-mediated antimicrobial response. These derangements may promote an increased risk of nosocomial pneumonia, the high mortality often observed subsequent to pneumonia, or the propagation of acute lung injury that facilitates respiratory failure.

Adult respiratory distress syndrome: current concepts

Adult Respiratory Distress Syndrome (ARDS) is a common diagnosis in today's intensive care units, representing a final common pathway of lung response to a variety of disease states. Mortality rates remain excessively high, despite comprehensive monitoring and intensive treatment. The incidence, etiology, clinical features, pathology and pathophysiology of ARDS are reviewed, with special emphasis on current research regarding potentially injurious mediators and possible etiopathogenetic mechanisms. Current therapy is summarized, and new therapeutic modalities are assessed. It is hoped that increased knowledge and awareness of the various aspects of ARDS will lead to further understanding and better clinical results in patients with this syndrome.

Acute respiratory failure induced by bleomycin and hyperoxia: pulmonary edema, cell kinetics, and morphology

The acute manifestations of experimental bleomycin- and hyperoxia-induced lung damage were examined. Hamsters were treated with 5 U/kg bleomycin intratracheally followed by exposure to 80% oxygen (O2). As little as 12 hr of O2 exposure potentiated the bleomycin injury; however, the onset of mortality was 72 hr after treatment. The onset of pulmonary edema, measured by radiolabeled tracers, also occurred 72 hr after treatment. Cell kinetics studies showed that 24 hr exposure to 80% O2 did not alter early alveolar cell proliferation. Treatment with bleomycin alone did result in an early increase in alveolar macrophage and type II pneumocyte labeling. Animals treated with both bleomycin and hyperoxia had an increase in macrophage labeling, but not in type II pneumocyte labeling. We conclude that increased macrophage numbers associated with suppressed type II pneumocyte proliferation may play key roles in the potentiation and development of lung damage caused by bleomycin and hyperoxia treatment.

Cardiogenic and hypovolemic shock

The symptoms, signs, and pathophysiology of two major forms of shock are discussed. Newer modalities of pharmacologic and supportive therapy for stabilization and reversal of these states are presented, including the use of the intra-aortic balloon pump and early surgical therapy for cardiogenic shock.

Acute respiratory failure following lithium intoxication. A report of two cases

Two patients suffering from severe lithium poisoning (blood level greater than 4 mmol/litre) were treated by haemodialysis. Both patients developed delayed respiratory failure, with the characteristics of adult respiratory distress syndrome, at a time when lithium levels had fallen below 2 mmol/litre. We recommend early respiratory support in the treatment of severe lithium intoxication.

Pulmonary calcinosis after renal transplantation in pediatric patients

Pulmonary calcinosis is a recognized complication of renal failure. The resulting pulmonary compromise may be severe or even fatal. The potential contribution of hypercalcemia, hyperphosphatemia, and increased calcium-phosphorus product to the development of pulmonary calcinosis has been controversial. We describe four patients (ages 2 1/4 to 18 years) who had severe pulmonary calcinosis and respiratory failure within three to five days after renal transplantation. Initial clinical and roentgenographic findings suggested noncardiogenic pulmonary edema. Marked pulmonary hypertension was present in the two patients in whom pulmonary artery pressure data were available. Other clinical features in common included poor allograft function with persistent uremia requiring dialysis and evidence of moderate to severe secondary hyperparathyroidism. In three of the patients, the calcium-phosphorus product increased markedly after transplantation, to peak values of 122 to 147. This increase occurred at the same time as the onset of respiratory failure. Peak serum calcium levels were 10.0 to 11.0 mg/dL and peak serum phosphorus levels were 9.2 to 13.5 mg/dL. All patients died of respiratory failure five to 58 days after transplantation. The posttransplantation period may be a time of increased risk of potentially fatal pulmonary calcinosis in pediatric renal transplant recipients. The diagnosis should be considered in any patient with respiratory failure of unknown cause following renal transplantation.

Disseminated intravascular coagulation and hypopotassemia associated with blast lung injury

Forty six people were injured by a large explosive charge detonated in a Jerusalem bus. Four were killed instantaneously and 22 needed hospital care. We describe our experience in five patients with blast lung injury (BLI), all of whom survived in spite of severe respiratory failure requiring mechanical ventilation. Disseminated intravascular clotting (DIC) developed in three of the five patients and significant hypopotassemia ranging from 2.2 to 2.9 mEq/L in four. These two complications have not been previously described in association with BLI. Both DIC and hypopotassemia responded to replacement therapy. Vigorous treatment of respiratory failure, early recognition, and prompt correction of hemostatic and electrolyte abnormalities may have contributed to the avoidance of fatalities among the five patients with severe blast injury.

Morphometric changes of the lung induced by inhaled bacterial endotoxin

Due to the ubiquitous nature of airborne endotoxin, an understanding of pulmonary alterations which follow inhalation of environmentally realistic concentrations of purified bacteria derived lipopolysaccharide (LPS) is important. Using LPS derived from Enterobacter agglomerans, a bacterium found in cotton and cotton mill dust, aqueous aerosols (effective LPS concentration 4 micrograms/m3) were generated and used to expose either normal hamsters (N = 6) or those rendered endotoxin tolerant by pre-ip injection of 0.1 LD50 LPS. Control groups (normal--N = 6; tolerant--N = 6) received saline aerosol only. At 6 hr after 5-hr aerosol exposure, lungs of all animals were fixed, processed for light and transmission electron microscopy, and subject to qualitative and to multitiered morphometric analysis using standard point counting techniques. Qualitative evaluation of TEM micrographs from LPS aerosolized-nontolerant hamsters showed endothelial alteration (focal disruption, subendothelial space formation, and cytoplasmic blebbing) but volume and number of endothelial cells were not changed indicating only slight, focal endothelial damage. Quantitatively, septal capillary blood space in nontolerant, LPS aerosolized hamsters showed increased Vv of PMNs and platelets. These changes were not seen in tolerant induced-LPS aerosolized hamsters. Independent of tolerization treatment, LPS inhalation led to a decrease in fixed lung volume and an increase in numerical density of endothelial pinocytotic vesicles. It is concluded that the inhalation of realistic, environmental levels of bacterial endotoxin may induce significant changes in distal lung and may be important in the pathogenesis of byssinosis and adult respiratory distress syndrome.

Ventilatory support in patients with ARDS

Adult respiratory distress syndrome remains one of the most lethal conditions treated in surgical and medical intensive care units. Mortality rates of 50 per cent are still reported in recent reviews. Many risk factors are linked with an increased incidence of ARDS, but sepsis and direct pulmonary injury from aspiration, pulmonary contusion, and other forms of trauma are the most commonly associated risk factors. Studies implicate various cellular and chemical mediators associated with acute lung injury. Many pharmacologic agents and various forms of high-frequency ventilation are being studied for their effectiveness in treating ARDS. We consider that the standard treatment continues to be PEEP and mechanical ventilation to reverse hypoxemia linked with the pathophysiologic changes of ARDS. There are no prospective randomized studies comparing the various end points of therapy used clinically at present. We believe, however, that early intervention, with institution of ventilatory support as soon as signs of acute respiratory failure develop, may eliminate some deaths due to progressive hypoxemia leading to the full adult respiratory distress syndrome. Therapy should be started at this time and maintained while the etiologic factors are identified and treated. Minimal ventilatory support should be continued until the primary diseases have resolved and the multisystem impact of the critical illness has lessened. Weaning from inspiratory (IMV) support, manipulation of expiratory pressures (PEEP), and airway control should then be more easily accomplished and more successful in practice.

Adult respiratory distress syndrome after allogeneic bone-marrow transplantation: evidence for a neutrophil-independent mechanism

5 patients in whom the adult respiratory distress syndrome (ARDS) developed after bone-marrow transplantation (BMT) for chronic myeloid leukaemia are described. Donors in all cases were siblings who were matched for all major-histocompatibility-complex determinants. All patients were neutropenic to varying degrees at the onset of respiratory symptoms. Histological evaluation in all patients at necropsy showed diffuse alveolar damage with no evidence of intrapulmonary neutrophil sequestration. No patient had detectable levels of plasma peroxidation products, which were measured as an index of neutrophil oxidant function. Significantly increased clearance of inhaled 99mTc-diethylene-triamine-pentacetate was a uniform finding, suggesting impaired alveolar-capillary barrier function in keeping with ARDS. An increase in an index of lung epithelial permeability leading to ARDS may develop in neutropenic patients who have evidence of neither intrapulmonary neutrophil sequestration not tissue oxidant injury. ARDS after BMT is probably multifactorial in aetiology, but neutrophil-derived oxidant products play no part in its genesis.

Reduced pulmonary capillary blood volume as a long-term sequel of ARDS

Lung function was evaluated in nine survivors of ARDS. All patients were asymptomatic at rest at the time of the study, ie, 5.5 to 19 months after extubation (mean 12.5). Six had mild to moderate exertional dyspnea. Chest x-ray films showed no gross parenchymal abnormalities. Spirometry and pulmonary mechanics were either normal or minimally altered, particularly in smokers. At submaximal exercise levels, effort was limited by tachycardia in eight patients; one subject showed ventilatory and cardiovascular limitations. It was concluded that spirometry and pulmonary mechanics are restored to normal within six months after extubation, and gas exchange abnormalities persist after ARDS and might be related to intrapulmonary shunts at rest, whereas during exercise a decreased pulmonary capillary blood volume might be the primary factor.

The adult respiratory distress syndrome

The adult respiratory distress syndrome (ARDS) is a common form of acute respiratory failure that has been increasingly reported as associated with a wide variety of medical conditions. Unlike other identifiable pathological events causing severe lung injury, it is now recognized that ARDS is not a single disease, but a complex interaction of pathophysiological events that result in diffuse injury to lung parenchyma. Only through a thorough understanding of ARDS pathophysiology, pathogenesis, and clinical course can medical intervention be instituted in a judicious and timely manner. This review article is intended to provide an overview of the suspected precipitating causes, discrete pathophysiologic changes, and monitorable clinical events associated with ARDS. With mortality from ARDS high, significant attention is being given to improving therapeutic intervention with such conventional measures as mechanical ventilation, positive end-expiratory pressure, and fluid management, along with corticosteroids and several new experimental pharmacologic approaches.