Increased survival of ARDS patients with severe hypoxemia (ECMO criteria)

Acute respiratory distress syndrome: diagnosis and management

This review will attempt to put together the voluminous studies and concepts that have been published during the past 25 years following the description of the acute respiratory distress syndrome (ARDS) regarding diagnosis and management. The initial discussion will focus on how to clinically diagnose ARDS based recommendations. This also gives the current definition of acute lung injury and when to call it ARDS. The radiographic and hemodynamic characteristics are discussed including oxygenation parameters. The management outlines the conventional as well as new therapies intended to improve survival of this devastating disease.

Liposomal prostaglandin E1 in acute respiratory distress syndrome: a placebo-controlled, randomized, double-blind, multicenter clinical trial

OBJECTIVE

To evaluate the safety and efficacy of liposomal prostaglandin E1 (TLC C-53) in the treatment of patients with the acute respiratory distress syndrome (ARDS).

DESIGN

Randomized, prospective, multicenter, double-blind, placebo-controlled, phase II clinical trial.

SETTING

Eight community and university-affiliated hospitals in the United States.

PATIENTS

Twenty-five patients with ARDS.

INTERVENTIONS

Patients were prospectively randomized in an unbalanced ratio within each site to receive either TLC C-53 (n = 17) or placebo (n = 8). Study drug was infused intravenously over 60 mins every 6 hrs for a 7-day period, starting at a dose of 0.15 micrograms/kg/hr. The dose was increased every 12 hrs until the maximal dose (3.6 micrograms/kg/hr) was attained, intolerance to further increases developed, or invasive monitoring was discontinued. Patients received standard, aggressive, medical/surgical care throughout the trial.

MEASUREMENTS AND MAIN RESULTS

Outcome measurements were Pao2/FI0(2), dynamic pulmonary compliance, ventilator dependence on day 8, and 28-day all-cause mortality rate. At baseline, the distribution of variables describing Lung Injury Scores, Acute Physiology and Chronic Health Evaluation II scores, Pao2/FI0(2), pulmonary compliance, and time from onset of ARDS to first dose of study drug was similar between patients in the TLC C-53 and placebo treatment groups. On day 8, all eight patients given placebo required mechanical ventilation, while eight of 17 patients given TLC C-53 were healthy enough to be removed from the ventilator (p = .03). Improvement in PaO2/FIO2 during the initial 8-day study period was greater in patients receiving TLC C-53. This trend achieved statistical significance on day 3, when the increase in PaO2/FIO2 from baseline was 82.5 +/- 14.6 in the TLC C-53 group compared with 28.3 +/- 22.1 in the placebo group (p = .05). By day 8, lung compliance also increased from baseline significantly more in TLC C-53 patients than in placebo patients (5.7 +/- 1.7 vs -1.5 +/- 1.8 mL/cm H2O; p = .01). The 28-day mortality rate was 6% (1/17 patients) in the TLC C-53 group and 25% (2/8 patients) in the placebo group (p = .23). Drug-related adverse events were reported in 82% of the patients receiving TLC C-53 compared with 38% of the placebo group, with half of the adverse events in the TLC C-53 group being localized infusion site irritation. TLC C-53 was hemodynamically well tolerated, with transient hypotension occurring in three patients.

CONCLUSIONS

In patients with ARDS, TLC C-53 was associated with improved oxygenation, increased lung compliance, and decreased ventilator dependency.

Optimal values for oxygen transport during hypothermia in sepsis and ARDS

Mild hypothermia (33 degrees C to 35.5 degrees C) is reported to improve oxygenation and survival in patients with lung failure (1). Although hypermetabolism may account for about 50% of the ventilatory demand in ARDS patients, the concept of reducing oxygen consumption (VO2) by lowering metabolic rate, has only recently gained attention (2). Our study was aimed to test whether mild hypothermia established by continuous veno-venous haemofiltration (CVVHF), could optimize values for oxygen kinetics in ARDS patients. Overall, we recruited 27 patients with ARDS and sepsis. Prior initiation of CVVHF patients had to meet the following criteria: a) Murray score > 2.5, and hypoxaemia with PaO2/FIO2 < 200, b) hyperthermia of > 38 degrees C, c) cardiovascular instability requiring inotropic support. Evaluation of cardio-respiratory data was performed within four different phases (I = before, II + III during and IV = after CVVHF) every 6 hours. Core temperature as derived from the thermistor of pulmonary artery catheter was aimed to be between 35.0 degrees C and 36.5 degrees C. Optimal values for oxygen delivery (DO2) (> 550 mL/min/m2) and VO2 (> 160 mL/min/m2) were defined according to Shoemaker and achieved by fluid loading, transfusion and inotropic support (3). Septic shock occurred in 10 of 14 nonsurvivors (nons) and 2 of 13 survivors (surv). Mean values for DO2 and VO2 were calculated at different body temperature ranges. While at 37 degrees C DO2 was identical between surv and nons, (663 +/- 128 versus 666 +/- 127 means +/- SD) moderate hypothermia led to a small decrease of DO2 in surv and a significant decrease in nons (632 +/- 134 versus 605 +/- 128 mL/min/m2) at 35 degrees C. Concerning VO2 during hypothermia, there was a significant drop in nonsurvivors while in survivors the decrease was less pronounced. We could demonstrate a decrease in DO2 and VO2 during mild hypothermia during CVVHF. However, decreases in nonsurvivors were more pronounced than in survivors. These results suggest that the inability to achieve optimal values for DO2 and VO2 during mild hypothermia induced by CVVHF could serve as a prognostic sign for fatal outcome. Although oxygen consumption is decreased during hypothermia, hypoxaemia may result due to alterations of the oxygen transport on a cellular basis. The relationship between oxygen transport and temperature during CVVHF therefore deserves further studies.

Hospital survival rates of patients with acute respiratory failure in modern respiratory intensive care units. An international, multicenter, prospective survey

An international, multicenter, prospective survey has been conducted to determine the hospital survival rates of patients with potentially reversible acute respiratory failure (ARF) who are managed in sophisticated intensive care units by leading critical care specialists, using current (1991 to 1992) support and treatment techniques and protocols. Twenty-five clinical centers participated in the survey, 11 in the United States and 14 in Europe. A total of 1,426 patients with ARF were studied, all of whom had been receiving closed system positive pressure mechanical ventilation at an FIo2 of at least 0.50 for at least 24 h at the time of entry into the survey. Of the survey patients, 793 (55.6%) survived their hospitalization, while 633 (44.4%) died in the hospital. The 1,426 patients with ARF were prospectively divided into two groups: group A, containing 375 patients, who at the time of entry into the study were hypoxemic or hypercarbic while receiving mechanical ventilator assistance; and group B, containing 1,051 patients, who at the time of entry into the study were neither hypoxemic nor hypercarbic while receiving mechanical ventilator support at an FIo2 of 0.50 or greater. Hospital survival rate for group A patients was 33.3% and for group B patients it was 63.6%. Survival rates were higher in patients with ARF caused by pneumonia (63%) or post shock lung injury (67%) and lower in patients with ARF caused by sepsis (46%). Severity of lung injury at the time of entry into the survey was a major prognostic factor, varying from an 18% hospital survival rate for patients with ARF with far advanced lung injury to a survival rate of 67% for patients with ARF with less severe lung injury. Low survival rates (< 20%) were seen if mechanical ventilator FIo2 was 0.80 to 1.0, while 50% of the patients with ARF survived hospitalization whose FIo2 at entry was 0.50. Peak inspiratory pressure (PIP) > 50 cm H2O at entry into the survey was associated with survival rate of less than 20%, while PIP < 30 cm H2O was associated with survival rate of 60%. Shorter periods of mechanical ventilation (< 48 h) of group A patients before entering the survey were associated with higher survival rates (38%) than patients requiring mechanical ventilation for more than 2 weeks (30%). Patients with ARF with multiorgan failure had lower survival rates (10%) than those with pulmonary dysfunction alone (45%).(ABSTRACT TRUNCATED AT 400 WORDS)

The role of medical informatics in telemedicine

The role of medical informatics in telemedicine is dependent on using the power of the computerized database to not only feed patient specific information to the health care providers, but to use the epidemiological and statistical information in the data base to improve decision making and ultimately care. The computer is also a powerful tool to facilitate standardizing and monitoring of care and when applied in continuous quality improvement methodology it can enhance the improvement process well beyond what can be done by hand. The coupling of medical informatics with telemedicine allows sophisticated medical informatics systems to be applied in low population density and remote areas.

Risks and hazards of mechanical ventilation: a collective review of published literature

A collective, analytic review was undertaken of all available published scientific papers that reported data about risks, hazards, adverse effects, or complications from augmentation of blood gas exchange by means of intensive closed system positive pressure mechanical ventilation. On the basis of the data collected, the adverse effects of intensive positive pressure mechanical ventilation were classified into the following groups: oxygen toxicity; adverse effects from excessive ventilatory pressures, volumes, and flow rates; adverse effects from tracheal intubation; dangers from adjuvant drugs; stress-related sequelae; altered enzyme and hormone systems; nutritional problems; and psychologic trauma. A bibliography pertaining to each group of adverse effects has been prepared. In addition, the reported incidence of adverse effects resulting from intensive mechanical ventilation in patients in clinical intensive care is shown. Clinical and laboratory observations of patients who receive intensive positive pressure mechanical ventilation in respiratory intensive care units have yielded some data, and findings from experimental studies in normal volunteers and laboratory animals have also been collected and reviewed. Tables, charts, and graphs that summarize the pertinent findings are presented and discussed. The following conclusions are drawn from critical evaluation of the collected data: (1) Closed system positive pressure mechanical ventilation applied at mild to moderate levels of intensity is a safe and effective method for augmenting deficient blood gas exchange in most patients who are in acute respiratory failure. (2) On the other hand, intensive levels of mechanical ventilator support or inappropriate methods of applying mechanical ventilation may be accompanied by a variety of risks, hazards, adverse effects, and complications that may further injure the failing lungs or may add significantly to the morbidity and mortality rates of patients in whom it is applied. (3) Because of the unfavorable risk/benefit ratio of intensive positive pressure mechanical ventilation, physicians should consider the use of alternative methods that are now available for augmenting blood gas exchange in patients in acute respiratory failure who are not adequately treated by safe (mild to moderate) levels of positive pressure mechanical ventilation instead of electing to increase the intensity of positive pressure mechanical ventilation to more dangerous (intensive) levels.

Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation has now evolved into standard therapy for patients unresponsive to conventional ventilatory and pharmacological support. This article presents a clinical review of extracorporeal life support and its application to neonatal and pediatric patients as well as children requiring circulatory support after open heart surgery.

Extracorporeal carbon dioxide removal and low-frequency positive-pressure ventilation. Improvement in arterial oxygenation with reduction of risk of pulmonary barotrauma in patients with adult respiratory distress syndrome

Mortality of the adult respiratory distress syndrome (ARDS) remains high and could be increased by pulmonary barotrauma induced by positive-pressure mechanical ventilation. Extracorporeal CO2 removal combined with low-frequency positive-pressure ventilation (ECCO2R-LFPPV) has been proposed to reduce lung injury while supporting respiratory failure. Use of this technique in 23 patients resulted in the following: a dramatic and highly significant increase of PaO2 obtained rapidly with ECCO2R-LFPPV, allowing subsequent reduction in inspired oxygen fraction; a reduction of the risk of barotrauma evidenced by a significant decrease in pressures and insufflated volumes; a survival rate of 50 percent. Bleeding was the only complication related to the technique and was the cause of death in four patients. This method allowed improvement in gas exchange along with reduction of the risk of barotrauma caused by the ventilator.

Management of septic shock

There have been important advances in the resuscitation of patients in septic shock in recent years. Survival can be improved by earlier recognition and therefore eradication of the sepsis combined with logical supportive measures. As with any acutely ill patient consultation with intensive care unit staff may be useful. Consultation with the intensive care unit does not necessarily imply the need for admission and mechanical ventilation; helpful advice may be forthcoming. Equally, referral to the intensive care unit does not mean an admission of failure but merely a recognition that additional skills and technical facilities are necessary for the patient's survival.

Lung protein leakage in feline septic shock

The aim of the present study was to explore lung microvascular leakage of protein and water in a feline model of septic shock, using a double isotope technique with external gamma camera detection and gravimetric lung water measurements. The experiments were performed on artificially ventilated cats. One group of cats (n = 8) was given an infusion of live Escherichia coli bacteria, and another group (n = 5) served as a control group receiving saline. Plasma transferrin was radiolabeled in vivo with indium-113m-chloride, and erythrocytes were labeled with technetium-99m. The distribution of these isotopes in the lungs was continuously measured with a gamma camera. A normalized slope index (NSI) was calculated, indicative of the transferrin accumulation corrected for changes in local blood volume that reflect protein leakage. In the septic group there was a protein leakage after bacterial infusion, with a NSI of 39 x 10(-4) +/- 5 x 10(-4) min-1 (mean +/- SEM), and the PaO2 diminished from 21 +/- 1 to 9.5 +/- 1 kPa. In control cats a slight protein leakage with a NSI of 9 +/- 10(-4) +/- 2 x 10(-4) min-1 was detected, probably caused by the operative procedure, but PaO2 did not change. Wet-to-dry-weight ratios of postmortem lungs were not significantly different between the groups. It was concluded that an intravenous infusion of live E. coli bacteria induces a lung capillary protein leakage without increased lung water and a concomitantly disturbed gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

Uses of extracorporeal membrane oxygenation in nonneonatal respiratory patients. An update

Neonatal extracorporeal membrane oxygenation (ECMO) has progressed rapidly from the experimental stage to a standard of care for certain infants who fail to respond to maximal conventional management. A broad diagnostic group of nonneonatal patients has now been supported by several different modes of ECMO with encouraging results. Selection criteria for nonneonatal patients that differ from those used for neonatal patients are emerging. Prospective randomized clinical trials are needed.

Treatment of acute pulmonary failure with extracorporeal support: 100% survival in a pediatric population

Since February 1990, five children, aged 10 days to 6.5 years, were treated with extracorporeal lung support at our hospital for acute, unrelenting pulmonary failure. Two had viral pneumonia: one with respiratory syncytial virus (RSV) bronchiolitis, and one with herpes simplex virus pneumonia, encephalitis, and disseminated intravascular coagulation. One presented with a febrile illness followed by a pulmonary hemorrhage. Two patients had adult respiratory distress syndrome (ARDS) complicating severe systemic illnesses, toxic epidermal necrolysis in one and cat scratch disease with encephalitis in the other. All children had diffuse parenchymal lung disease by chest x-ray. On maximum medical management all patients were developing carbon dioxide retention and progressive hypoxemia, exceeding previously established NIH study criteria for extracorporeal treatment. Three children (10 days, 2 months, 13 months) were placed on venoarterial support and two children (20 months and 6.5 years) were placed on venovenous extracorporeal support (ECCO2R). Three of the five had open lung biopsies performed, which showed findings consistent with a moderate to severe cellular phase of ARDS. No viral inclusions were found in the patient with RSV infection. One hundred percent immediate survival was achieved in this patient population. Average duration of support was 330 hours (range, 89 to 840). Following completion of extracorporeal support, all children were successfully weaned from the ventilator with an average time to extubation of 23.2 days (range, 2 to 58 days). One child died of congestive heart failure following palliative surgery for a complex noncyanotic congenital cardiac lesion 35 days after successfully weaning from extracorporeal support for an acute febrile illness and pulmonary hemorrhage.(ABSTRACT TRUNCATED AT 250 WORDS)

The pulmonary physician and critical care. 2. The injured lung: conventional and novel respiratory therapy

Several alternatives to conventional ventilation in acute lung injury are now available and have been investigated to a varying degree. The assessment of all such techniques is limited by difficulties in designing proper comparative studies and by the time needed to recruit a large number of appropriate patients with acute lung injury. A common theme of lung volume maintenance combined with strategies designed to limit the extent of ventilator induced lung damage has emerged and should encourage reassessment of the conventional approach. The results of several large prospective comparative studies are eagerly awaited. Meanwhile we may reasonably suggest that improvements in respiratory support, together with advances in microbiological and pharmacological treatment, have the potential for improving the persistently disappointing survival rate in acute lung injury.

Medical informatics in the intensive care unit: state of the art 1991

Intensive care medicine requires timely, accurate, and integrated patient records to provide the highest quality patient care. Computerized patient records offer the best method to achieve these needs. The expectations of society for medical progress through increased use of computers is growing. For optimal use of computers in the ICU there must be a harmonious collaboration between medical informaticists, physicians, nurses, therapists, and administrators. The future use of computers in ICU care will be evolutionary rather than revolutionary. We are on the frontier of some exciting times in the next decade as computers become commonplace in the clinical care process rather than an unusual event. This paper discusses the progress and challenges of computers in the ICU.

Fibroproliferative phase of ARDS. Clinical findings and effects of corticosteroids

Most patients with adult respiratory distress syndrome (ARDS) survive the initial insult which caused respiratory failure only to succumb later to sepsis caused by nosocomial pneumonia or to pulmonary fibrosis. Clinical criteria and analysis of the tracheal aspirate are notoriously inadequate for establishing a diagnosis of ventilator-associated pneumonia. We implemented a comprehensive diagnostic protocol to determine the cause of sepsis in ARDS patients who had been ventilated for more than three days and who had no bronchoscopic evidence of pneumonia. Nine patients with late ARDS who had fever (89 percent), leukocytosis (89 percent), a new localized infiltrate (78 percent), purulent tracheal secretions (89 percent), low systemic vascular resistance (50 percent), and marked uptake of gallium in the lungs (100 percent) had no source of infection identified. Open-lung biopsy specimens from seven patients showed the fibroproliferative phase of diffuse alveolar damage and confirmed absence of pneumonia. Treatment with prolonged high doses of corticosteroids was associated with a marked and rapid improvement in lung injury score (p less than 0.003 at five days). Our findings indicate that the fibroproliferative process occurring in the lungs of patients with late ARDS gives rise to clinical manifestations identical to those of pneumonia and is potentially responsive to steroid treatment.