Effects of inhaled nitric oxide in patients with acute respiratory distress syndrome: results of a randomized phase II trial. Inhaled Nitric Oxide in ARDS Study Group

OBJECTIVES

To evaluate the safety and physiologic response of inhaled nitric oxide (NO) in patients with acute respiratory distress syndrome (ARDS). In addition, the effect of various doses of inhaled NO on clinical outcome parameters was assessed.

DESIGN

Prospective, multicenter, randomized, double-blind, placebo-controlled study.

SETTING

Intensive care units of 30 academic, teaching, and community hospitals in the United States.

PATIENTS

Patients with ARDS, as defined by the American-European Consensus Conference, were enrolled into the study if the onset of disease was within 72 hrs of randomization.

INTERVENTIONS

Patients were randomized to receive placebo (nitrogen gas) or inhaled NO at concentrations of 1.25, 5, 20, 40, or 80 ppm.

MEASUREMENTS AND MAIN RESULTS

Acute increases in PaO2, decreases in mean pulmonary arterial pressure, intensity of mechanical ventilation, and oxygenation index were examined. Clinical outcomes examined were the dose effects of inhaled NO on mortality, the number of days alive and off mechanical ventilation, and the number of days alive after meeting oxygenation criteria for extubation. A total of 177 patients were enrolled over a 14-month period. An acute response to treatment gas, defined as a PaO2 increase > or =20%, was seen in 60% of the patients receiving inhaled NO with no significant differences between dose groups. Twenty-four percent of placebo patients also had an acute response to treatment gas during the first 4 hrs. The initial increase in oxygenation translated into a reduction in the FIO2 over the first day and in the intensity of mechanical ventilation over the first 4 days of treatment, as measured by the oxygenation index. There were no differences among the pooled inhaled NO groups and placebo with respect to mortality rate, the number of days alive and off mechanical ventilation, or the number of days alive after meeting oxygenation criteria for extubation. However, patients receiving 5 ppm inhaled NO showed an improvement in these parameters. In this dose group, the percentage of patients alive and off mechanical ventilation at day 28 (a post hoc analysis) was higher (62% vs. 44%) than the placebo group. There was no apparent difference in the number or type of adverse events reported among those patients receiving inhaled NO compared with placebo. Four patients had methemoglobin concentrations >5%. The mean inspired nitrogen dioxide concentration in inhaled NO patients was 1.5 ppm.

CONCLUSIONS

From this placebo-controlled study, inhaled NO appears to be well tolerated in the population of ARDS patients studied. With mechanical ventilation held constant, inhaled NO is associated with a significant improvement in oxygenation compared with placebo over the first 4 hrs of treatment. An improvement in oxygenation index was observed over the first 4 days. Larger phase III studies are needed to ascertain if these acute physiologic improvements can lead to altered clinical outcome.

Bovine surfactant therapy for patients with acute respiratory distress syndrome

Lung surfactant is deficient in patients with acute respiratory distress syndrome (ARDS). We performed a randomized, prospective, controlled, open-label clinical study of administration of a bovine surfactant to patients with ARDS to obtain preliminary information about its safety and efficacy. Patients received either surfactant by endotracheal instillation in addition to standard therapy or standard therapy only. Three different groups of patients receiving surfactant were studied: patients receiving up to eight doses of 50 mg phospholipids/kg, those receiving up to eight doses of 100 mg phospholipids/kg, and those receiving up to four doses of 100 mg phospholipids/kg. Outcome measures included ventilatory support parameters, arterial blood gases, organ system failures, bronchoalveolar lavage (BAL) analyses, immunologic analyses, survival, and adverse events during the 28-d study period. Fifty-nine study patients were evaluable; 43 in the surfactant group and 16 in the control group. The FI(O2) at 120 h after treatment began was significantly decreased only for patients who received up to four doses of 100 mg phospholipids/kg surfactant as compared with control patients (p = 0.011). Mortality in the same group of patients was 18.8%, as compared with 43.8% in the control group (p = 0.075). The surfactant instillation was generally well tolerated, and no safety concerns were identified. This pilot study presents preliminary evidence that surfactant might have therapeutic benefit for patients with ARDS, and provides rationale for further clinical study of this agent.

Integrated management of venous thromboembolism

Diagnostic methods for pulmonary embolism and deep vein thrombosis of the lower extremity are intertwined, since the latter nearly always precedes the former. Recent prospective studies show that an independent clinical estimate of disease probability helps to refine probability estimates of ventilation-perfusion lung scans and of ultrasonography with compression, reducing the need for pulmonary angiography and contrast venography. Repeated ultrasonography with compression can also be used to stratify patients into groups that are at high or low risk for subsequent pulmonary embolic events. I give algorithms and guidelines for the clinical use of these findings. Effective treatment of acute venous thromboembolism depends on achieving an antithrombotic state with heparin and warfarin. I give recommendations for dosing and monitoring heparin and warfarin that are based on knowledge of heparin blood levels and on use of the international normalized ratio with warfarin therapy. Use of low-molecular-weight heparin to prevent deep vein thrombosis is briefly described.

Tissue factor pathway inhibitor and von Willebrand factor antigen levels in adult respiratory distress syndrome and in a primate model of sepsis

Tissue factor pathway inhibitor (TFPI) is an anticoagulant protein primarily synthesized by the endothelium. A major fraction (approximately 85%) of TFPI remains associated with the endothelium, whereas a small fraction (approximately 15%) is secreted into the blood. In our attempts to search for a marker(s) of endothelial injury in the setting of adult respiratory distress syndrome (ARDS), we retrospectively measured plasma TFPI levels in patients at risk for and with ARDS caused by several etiologic factors. Plasma von Willebrand factor antigen (vWF-Ag), another endothelial-specific protein, was also measured in these patients. The mean plasma TFPI levels were slightly elevated (approximately 1.3-fold), whereas vWF-Ag levels were significantly elevated (approximately 3-fold) in the at-risk group as compared with those in the normal subjects. Both the TFPI (approximately 1.8-fold) and the vWF-Ag (approximately 4-fold) levels were further elevated in the ARDS group. Moreover, the sequential plasma samples from patients with ARDS had progressively increased levels of vWF-Ag and TFPI up to Days 4 and 8, respectively. Neither plasma vWF-Ag nor TFPI levels correlated with mortality in the at-risk group or the ARDS group. TFPI levels were also measured in bronchoalveolar lavage fluids (BALF). The levels (ng/ml) were: normal subjects, 0.05 +/- 0.02 SE; at-risk group, 0.35 +/- 0.16 SE; ARDS group, 0.99 +/- 0.28 SE. Thus, the BALF TFPI levels were increased approximately 7-fold in the at-risk group and approximately 20-fold in the ARDS group relative to the value in the normal subjects. These findings indicate increased local synthesis of TFPI in the alveolar space both in the at-risk patients and in those with ARDS. In additional studies in a primate model of sepsis, lethal doses (LD100) of E. coli administered to baboons resulted in a progressive increase in TFPI levels (approximately 2-fold at 6 h), whereas sublethal doses caused only minimal increase (approximately 1.2-fold). The vWF-Ag levels were elevated approximately 5-fold after infusion of LD100 concentrations of E. coli at 6 h and 4-fold after infusion of sublethal concentrations of E. coli at 24 h. Autopsies on animals in the LD100 group revealed pulmonary congestion, leukocyte infiltration, edema, and hemorrhage, all suggestive of acute lung injury. Thus, in the setting of acute lung injury plasma vWF-Ag appears to be considerably increased prior to significant damage to the endothelium, whereas increased plasma TFPI occurs only after severe injury.(ABSTRACT TRUNCATED AT 400 WORDS)

Prediction of survival and mortality in patients with adult respiratory distress syndrome

The adult or acute respiratory distress syndrome (ARDS) is an increased permeability pulmonary edema that occurs most often as a complication of bacterial sepsis, aspiration of gastric contents, or massive trauma. Clinically, the syndrome is recognized as acute respiratory failure with bilateral infiltrates on chest radiograph, a marked oxygenation defect, and normal or nearly normal cardiac function. Since its first comprehensive description > 25 yrs ago, the reported mortality rate of ARDS has remained high. Current series describe mortality rates in the range of 50% to 60%. The major cause of death in patients with ARDS seems to be bacterial sepsis and multiple organ dysfunction. Predictors of survival and mortality have been studied. Older patients (> or = 60 yrs) who develop bacterial sepsis and multiple organ dysfunction are at high risk to die. Younger patients who develop ARDS from trauma or other noninfectious causes have a better prognosis. Persistent metabolic acidosis on the first day of ARDS is a particularly poor prognostic sign.

IR-192, low dose rate endobronchial brachytherapy in the treatment of malignant airway obstruction

PURPOSE

To assess the value of low-dose-rate endobronchial brachytherapy in the treatment of malignant airway obstruction.

METHODS AND MATERIALS

Between September 1986 and April 1989, 39 patients with malignant airway obstruction had 49 catheter placements for an afterloading, low-dose-rate Ir-192 endobronchial brachytherapy. A flexible fiberoptic bronchoscope with fluoroscopic guidance was used for positioning. Thirty-eight of 39 (97%) patients completed the prescribed treatments. Ninety-seven percent had received previous external radiation in doses ranging from 36-60 Gy. One patient had metastatic renal cell carcinoma; the remainder had recurrent lung cancer. Endobronchial laser treatments were given to three patients 2-3 weeks prior to endobronchial brachytherapy. All patients were followed until death. The median dose delivered in 48 of the 49 placements was 20 Gy at 1 cm.

RESULTS

Follow-up bronchoscopy was performed in 28 (72%) of 39 patients. Of these, 13 (46%) had a complete response, 12 (43%) had a partial response, and 3 (17%) had a minor response. Dyspnea improved in 30 of 37 patients (82%); hemoptysis in 17 of 19 patients (89%); cough in 31 of 39 patients (79%); and postobstructive pneumonia in 21 of 23 patients (92%). The median survival for the entire group was 5 months (range 1-31 months).

CONCLUSION

This technique is simple, well-tolerated and offered significant palliation.

Heparin therapy. Regimens and treatment considerations

Heparin is a parenteral antithrombotic agent with efficacy in the treatment and prevention of venous thromboembolic disease and in preinfarctional angina. Accumulating evidence also suggests that heparin is useful in the prevention of coronary artery reocclusion after thrombolytic therapy for acute myocardial infarction, and in the prevention of left ventricular mural thrombosis after anterior wall myocardial infarction. Heparin appears to offer only marginal benefit in reducing mortality when given in combination with thrombolytic therapy and aspirin for acute myocardial infarction. When used for prevention of venous thromboembolism in moderate risk patients, heparin should be given subcutaneously in a dose of 5000 U every 12 hours for 5 to 7 days or until the patient is ambulatory. In higher risk patients, such as those undergoing total hip replacement, heparin should be given subcutaneously every 12 hours in a dose to prolong the activated partial thromboplastin time (aPTT) by 4 to 5 seconds into the upper normal range. When used to treat active venous thromboembolism or the peri-infarctional state, heparin should be given by intravenous infusion with loading and maintenance doses to consistently prolong the aPTT to between 1.5- and 2.5-fold the control value (mean of laboratory's normal range). If constant intravenous infusion is not possible, the drug should be given subcutaneously every 12 hours to consistently prolong the aPTT between 1.5 and 2.5 times control. This regimen is also recommended in pregnant women with venous thromboembolic disease or mechanical heart valves.

Achieving consensus on withdrawing or withholding care for critically ill patients

OBJECTIVE

To examine the decision-making process to withhold or stop life support.

DESIGN

Survey.

SETTING

Medical intensive care unit of a tertiary care center.

PARTICIPANTS

Physicians and families of 15 critically ill patients; in seven cases patients also participated.

MEASUREMENTS

Meetings between physicians and family members concerning a decision to withhold or stop treatment of a critically ill family member were tape-recorded. Transcriptions of the meetings were analyzed for 1) process: how the physician introduced the need for a decision, framed the likely outcomes of options, and closed on a decision; 2) what decision was made; and 3) the outcome; died, discharged home, or discharged to another institution.

RESULTS

The concept of "patient's wishes" was a central orientation point for the negotiation of consensus regarding withholding or withdrawing therapy even when the patient was not a participant. Physicians tended to provide a direct and unambiguous introduction, give equal weights to options during decision framing, but narrow the options during decision closure to correspond to their judgments. Not every decision was consistent with the physician's judgment.

CONCLUSIONS

Decision making to withhold or withdraw life-support therapy from critically ill persons involves complex, difficult processes. Successful management of the tension among life extension, quality of life, patient autonomy, and social justice requires better understanding of these processes.

Priming of human neutrophil functions by tumor necrosis factor: enhancement of superoxide anion generation, degranulation, and chemotaxis to chemoattractants C5a and F-Met-Leu-Phe

Recombinant human tumor necrosis factor-alpha (rTNF) stimulated increased generation of superoxide anion (O2-) by human neutrophils in a concentration-dependent fashion. Preincubation of human neutrophils with rTNF (2.2-2200 units/ml) for 10 min enhanced the subsequent generation of O2- in response to C5a and f-Met-Leu-Phe (FMLP). Recombinant TNF did not enhance O2- generation by neutrophils stimulated with phorbol myristate acetate (PMA). Recombinant TNF alone failed to induce release of myeloperoxidase (MPO) and lysozyme by neutrophils. However, it did enhance the release of MPO and lysozyme by neutrophils stimulated with C5a and FMLP, but not with PMA. Although rTNF alone (0.001-50,000 units/ml) was not chemotactic for neutrophils, preincubation of neutrophils with rTNF (0.001-0.1 units/ml) enhanced the chemotactic activity of suboptimal concentrations of C5a (0.1 nM) and FMLP (5 nM). Neutrophils treated with high concentrations of rTNF (100-10,000 units/ml) showed inhibition of random movement and of chemotaxis induced by C5a or FMLP. We conclude from these studies that rTNF primes neutrophils for enhanced responses to subsequent stimuli and thus may augment the inflammatory response by increased oxidant production and lysosomal enzyme release and promote down-regulation of chemotactic movement.

Inhibition of some human neutrophil functions by the cyclooxygenase inhibitor ketorolac tromethamine

Ketorolac tromethamine, a new nonsteroidal anti-inflammatory agent of the pyrrolo-pyrrole group, was assayed for inhibitory effects on polymorphonuclear leukocytes (PMN) in a variety of systems. Ketorolac inhibited PMN superoxide anion generation, lysozyme release, myeloperoxidase release, adherence to plastic surfaces, and chemotaxis in response to N-formyl-methionyl-leucyl-phenylalanine (fMLP) in a dose-dependent manner. Ketorolac also inhibited phorbol myristate acetate-stimulated adherence of PMN to bovine pulmonary artery endothelial cells. The drug inhibited lysozyme and myeloperoxidase release by PMN in response to C5a but failed to inhibit C5a stimulation of PMN in any of the other assays. Levels of ketorolac required to inhibit PMN function in most systems were in the range of 0.2 to 1.0 mg/ml, but chemotaxis to fMLP was inhibited by concentrations of ketorolac as low as 1 microgram/ml. Ketorolac, currently the only nonsteroidal anti-inflammatory drug available in a parenteral form may have therapeutic usefulness in a variety of conditions thought to be mediated in part by PMN, including sepsis.

Clinical controversies in asbestos-induced lung diseases

Asbestos is a heterogeneous mineral fiber with considerable heat resistance and sound-abatement properties. It is relatively easily mined and processed and has been applied in a number of forms to ships and buildings. Unfortunately, respirable asbestos fibers have significant pathologic effects on the human lung and other organs. These effects can result in characteristic pleuropulmonary diseases, which become manifest after a latency period of 10 to 40 years from first exposure. This brief review will outline some major current controversies in the clinical approach to evaluation of asbestos-induced lung diseases.

The effects of prostaglandin E1 on non-pulmonary organ function during clinical acute respiratory failure. The Prostaglandin E1 Study Group

The effects of prostaglandin E1 (PGE1) on non-pulmonary vital organs in critically ill patients are not well defined. This study evaluated the role of exogenous PGE1 in systemic homeostasis during the adult respiratory distress syndrome (ARDS). Indicators of end-organ function were analyzed retrospectively in 146 septic or post-trauma patients with ARDS who received PGE1 (30/ng/kg/min) or placebo IV for up to 7 days in a randomized, double-blind clinical trial. Hemodynamic variables and serum levels of creatinine, bilirubin, and SGOT, platelet count, and changes in the white blood cell count were measured daily. Our results indicate that mean arterial pressure, pulmonary artery pressure, and systemic and pulmonary vascular resistance indices were significantly lower in the PGE1 group versus the placebo-treated group. Cardiac index, stroke index, and oxygen delivery index were significantly increased in the PGE1 group. Serum bilirubin and SGOT were decreased significantly among PGE1-treated patients compared with placebo-treated patients, while the white blood cell count increased more significantly from baseline values with PGE1 treatment. Intergroup differences in platelet count and serum creatinine levels were not statistically significant. The results indicate that PGE1 improves cardiovascular performance, hepatic function, and leukocyte availability during clinical ARDS. Prostaglandin E1 did not affect platelet counts and renal function in this study.

Adult respiratory distress syndrome. Sequence and importance of development of multiple organ failure. The Prostaglandin E1 Study Group

STUDY OBJECTIVE

To determine the epidemiology of multiple organ failure (MOF) in patients with the adult respiratory distress syndrome.

PATIENTS

We followed up 50 patients with serial determinations of respiratory and nonrespiratory organ function for seven days after diagnosis.

DESIGN

Data were stratified between patients who died and those who survived (defined as hospital discharge).

MEASUREMENTS AND RESULTS

Values that did not differ at any time between the two groups of patients included oxygen availability, oxygen consumption, oxygen extraction, PaCO2, respiratory rate, heart rate, systolic blood pressure, cardiac output, stroke index, systemic vascular resistance, and temperature. Patients who died had greater defects in oxygenation (from day 1 through day 7). They also exhibited decreased arterial oxygen content (from day 1 to day 4), decreased mixed venous oxygen content (day 1), increased peak inspiratory pressure (present on day 2, persisted to day 5, reappeared on day 7), decreased diastolic blood pressure (seen on days 1 through 3, reappeared on day 7), and increased mean pulmonary artery pressure (seen on days 2 and 3). Nonsurvivors also exhibited greater degrees of thrombocytopenia (from day 1 to day 4). Decreases in pH (seen on day 1, reappeared from days 4 to 7), abnormalities in liver function (seen only on day 1), and increases in serum creatinine levels (appeared on day 7) were also observed.

CONCLUSIONS

Multiorgan dysfunction (MOD) was frequently observed in both groups of patients. Alterations in organ function and the pattern of abnormalities were often subtle and would not be characterized as significant organ dysfunction by most available organ scoring systems. Adult respiratory distress syndrome is a manifestation of systemic disease produced by widespread increases in endothelial permeability; lung dysfunction dominates the early clinical course. When respiratory function is supported, it becomes evident that alterations occur in other organs. Multiorgan failure is really a misnomer; the term emphasizes end-stage changes. Multiorgan dysfunction is common and often resolves without progressing to MOF. Alternatively, MOD can progress to MOF.

Surfactant chemical composition and biophysical activity in acute respiratory distress syndrome

Acute Respiratory Distress Syndrome (ARDS) is characterized by lung injury and damage to the alveolar type II cells. This study sought to determine if endogenous surfactant is altered in ARDS. Bronchoalveolar lavage was performed in patients at-risk to develop ARDS (AR, n = 20), with ARDS (A, n = 66) and in normal subjects (N, n = 29). The crude surfactant pellet was analyzed for total phospholipids (PL), individual phospholipids, SP-A, SP-B, and minimum surface tension (STmin). PL was decreased in both AR and A (3.48 +/- 0.61 and 2.47 +/- 0.40 mumol/ml, respectively) compared to N (7.99 +/- 0.60 mumol/ml). Phosphatidylcholine was decreased in A (62.64 +/- 2.20% PL) compared to N (76.27 +/- 2.05% PL). Phosphatidylglycerol was 11.58 +/- 1.21% PL in N and was decreased to 6.48 +/- 1.43% PL in A. SP-A was 123.64 +/- 20.66 micrograms/ml in N and was decreased to 49.28 +/- 21.68 micrograms/ml in AR and to 29.88 +/- 8.49 micrograms/ml in A. SP-B was 1.28 +/- 0.33 micrograms/ml in N and was decreased to 0.57 +/- 0.24 micrograms/ml in A. STmin was increased in AR (15.1 +/- 2.53 dyn/cm) and A (29.04 +/- 2.05 dyn/cm) compared to N (7.44 +/- 1.61 dyn/cm). These data demonstrate that the chemical composition and functional activity of surfactant is altered in ARDS. Several of these alterations also occur in AR, suggesting that these abnormalities occur early in the disease process.

Tumor necrosis factor levels in serum and bronchoalveolar lavage fluid of patients with the adult respiratory distress syndrome

Tumor necrosis factor (TNF) was measured antigenically and functionally in serum and bronchoalveolar lavage fluid (BAL) of patients with ARDS and those at high risk for ARDS. Of 22 patients with ARDS, 14 had sepsis or serious infection as the major clinical predisposition, and 10 of 20 high-risk patients had sepsis or serious infection. Mean levels of TNF in serum of patients with ARDS and high risk showed a trend toward elevation but were not significantly higher than mean serum levels in normal subjects. Mean levels of TNF in BAL of ARDS patients (242 +/- 126 pg/ml) were significantly higher than in normal subjects (9 +/- 5 pg/ml), p less than 0.05. Antigenic levels of TNF were undetectable in approximately half the patients with ARDS or the high-risk state. Levels of TNF in BAL appeared to be highest in the first day of ARDS. There appeared to be no relationship between levels of TNF in serum or BAL and subsequent mortality. However, serum levels of TNF were significantly higher in septic patients than in nonseptic patients, whereas this difference was not apparent in BAL. These results show that functional and antigenic elevations of TNF are present in BAL and perhaps in serum of patients with ARDS or with the high-risk state.

Effects of prostaglandin E1 on oxygen delivery and consumption in patients with the adult respiratory distress syndrome. Results from the prostaglandin E1 multicenter trial. The Prostaglandin E1 Study Group

We wanted to determine the long-term effects of a continuous infusion of PGE1 on DO2 and VO2 in patients with ARDS. Data were obtained from a randomized double-blind multicenter trial, which evaluated the effects of PGE1 on survival in patients with ARDS. Patients were stratified according to treatment and outcome: placebo-died (n = 8); PGE1-died (n = 12); placebo-survived (n = 9); and PGE1-survived (n = 8). In the placebo-died group, elevations occurred in VO2, which were associated with increases in O2ext and a constant DO2. In contrast, in the PGE1-died group, elevations in VO2 were associated with increases in DO2 and an unchanged O2ext. In the placebo-survived group, VO2 and DO2 decreased, whereas in the PGE1-survived group, VO2 and DO2 increased; however, O2ext decreased in both of these groups. Since impaired O2ext occurs in ARDS, PGE1-induced elevations in DO2, rather than compensatory increases in O2ext, may achieve better tissue oxygenation. We conclude that although the recently completed multicenter trial failed to show an enhancing effect of PGE1 on survival in patients with advanced ARDS, PGE1 may have important effects on oxygen transport and, therefore, may still have a role in the treatment of early manifestations of ARDS, either alone or in combination with other agents.

The reduction of weaning time from mechanical ventilation using tidal volume and relaxation biofeedback

We sought to determine if biofeedback could reduce weaning time for the hard-to-wean patient by improving important weaning factors that are not effectively dealt with by present weaning methods. These include respiratory muscle electromyograph (EMG) efficiency, respiratory drive, and the anxiety of the ventilator-dependent patient. After the patient had received mechanical ventilation for 7 days and the day weaning began (start), the patient was randomly assigned to biofeedback or to the control group. There were 20 patients assigned to each group, with mean ages of 60.2 (biofeedback) and 59.3 (control) yr. The patients assigned to the biofeedback group received daily, until extubation or being placed on no resuscitation status (termination), frontalis electromyographic (EMG) relaxation feedback for anxiety reduction and improved respiratory muscle EMG efficiency, tidal volume/diaphragm EMG (VT/DAP), and VT feedback for increasing VT and respiratory drive defined as tidal volume/inspiratory time (VT/TI). The control group was visited daily to control for attention and reassurance. The results showed a significant (p less than 0.01) reduction in mean ventilator days for the biofeedback group of 20.6 +/- 8.9 SD compared with 32.6 +/- 17.6 SD mean days for the control group. From start to termination, there was a significant (p less than 0.01) increase in baseline VT, from 295 +/- 41 to 415 +/- 45 ml, and a significant (p less than 0.02) increase in VT/DAP, from 0.33 +/- 0.09 to 0.94 +/- 0.22 L/mV for the biofeedback group but no significant change in these parameters for the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Venous thromboembolic disease: diagnosis and use of antithrombotic therapy

Several invasive and noninvasive tests are available to aid the clinician in the diagnosis of deep venous thrombosis and pulmonary embolism. Contrast venography remains the standard for diagnosing deep venous thrombosis of the lower extremity, while impedance plethysmography is sensitive, specific, and noninvasive. Compressive duplex ultrasonography is useful for deep venous thrombosis of the thigh down to the popliteal vein. The ventilation-perfusion lung scan is the most common test for diagnosing pulmonary embolism, but pulmonary angiography remains the standard. Heparin is the mainstay of treatment for deep venous thrombosis and pulmonary embolism, with an important role played by warfarin therapy.

Human C-reactive protein inhibits neutrophil chemotaxis in vitro: possible implications for the adult respiratory distress syndrome

C-reactive protein (CRP) is an acute-phase protein whose serum concentration can rise dramatically after onset of inflammation. Although the precise physiologic role of elevated CRP is not known, in vitro studies have shown that CRP potentially has both pro- and anti-inflammatory properties. We hypothesized that an elevation in serum CRP may be a mechanism to control acute inflammation by down-regulating some neutrophil functions. Therefore, elevated serum CRP levels in an inflammatory state in the lung, such as the adult respiratory distress syndrome (ARDS), may have a protective effect. We observed that highly purified CRP, at levels greater than 25 micrograms/ml, inhibited both random neutrophil movement and C5a-induced chemotaxis. Neutrophils incubated with CRP showed a dose-dependent diminution of migration toward chemotactic stimuli, with complete inhibition occurring at 100 micrograms/ml. This inhibitory effect of CRP on neutrophil movement was only partially reversed by washing the CRP-treated cells before assaying their chemotactic movement to 1 nmol/L C5a. Next we examined the neutrophil chemotactic activity of serum collected from normal nonsmokers, from patients at high risk for developing ARDS, and patients with ARDS. Both high-risk and ARDS serums has significantly less (p less than 0.001) neutrophil chemotactic activity than serums from normal subjects. In addition, serums from high-risk and ARDS patients had significantly elevated (p less than 0.001) levels of CRP compared with normal subjects. Anti-CRP treatment of ARDS and high-risk serum samples resulted in a significant increase (p less than 0.05) in the neutrophil chemotactic activity. Finally, addition of highly purified CRP to normal serum significantly reduces its neutrophil chemotactic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

A rabbit model of pulmonary hypertension induced by the synthetic platelet-activating factor acetylglyceryl ether phosphorylcholine

Development of effective treatment for human pulmonary hypertension (PHT) has been hampered by an incomplete understanding of its pathogenesis. We present a rabbit model of PHT based on platelet-activating factor (PAF), a potent phospholipid autacoid synthesized by a variety of mammalian cells. PAF was intravenously infused into rabbits for 4 wk. After the infusion, rabbits underwent pulmonary arterial catheterization for hemodynamic evaluation, and lung tissue was morphometrically analyzed for changes in cross-sectional areas of intima and media, and alteration in number of small pulmonary arteries. The heart was evaluated by the method of Fulton for right ventricular hypertrophy. Mean pulmonary arterial pressure was 20 +/- 2 mm Hg in PAF-treated rabbits compared with 12 +/- 1 mm Hg in vehicle-treated control rabbits. PAF induced a trend toward loss of small muscular pulmonary arteries, measuring 50 to 200 microns in diameter, and right ventricular hypertrophy. There was a decrease in circumference of the internal elastic lamina in vessels accompanying alveolar ducts and in alveolar walls, and a relative increase in the intimal cross-sectional area of these vessels. These lesions were associated with a trend toward medial hypertrophy. No increase in lung water was found. Pressure changes occurred in the absence of alterations in hematocrit and arterial partial pressure of oxygen. We conclude that chronic intravenous infusion of PAF, a naturally synthesized substance, into rabbits provides a potentially useful model for the study of vascular changes associated with PHT.

Immunoreactive interleukin-1 in bronchoalveolar lavage fluid of high-risk patients and patients with the adult respiratory distress syndrome

The adult respiratory distress syndrome (ARDS) is characterized by increased neutrophils and macrophages in bronchoalveolar lavage (BAL) fluid. Interleukin-1 (IL-1), an inflammatory mediator produced by macrophages, has been shown to be chemotactic for neutrophils and to stimulate lymphocyte activation and proliferation of fibroblasts. BAL was performed in patients with ARDS, patients at high risk to develop ARDS, and in normal nonsmokers. After removal of cells and surfactant-complexed lipids by centrifugation, the remaining supernatant was concentrated by ultrafiltration utilizing membranes retaining substances greater than 5000 daltons. The concentrate was assayed for immunoreactive IL-1 beta by a radioimmunoassay method. Patients with ARDS (n = 9) had an IL-1 level of 184 +/- 67 pg/ml, high-risk patients (n = 9) had 172 +/- 62 pg/ml, and normals (n = 10) had 4 +/- 1 pg/ml. There was a significant (p less than or equal to .05) increase in IL-1 in the ARDS and risk groups compared to normals. IL-1 was detected in serum from patients with ARDS (n = 19), high risk (n = 19), and normals (n = 8), but no difference was noted among the three groups. BAL cell differentials revealed that neutrophils were increased (p less than .05) in both the ARDS (59 +/- 10%) and high-risk (65 +/- 8%) groups compared to normals (2 +/- 1%). There was a correlation (r = 0.64, p less than .001) between IL-1 levels and BAL protein concentration. BAL IL-1 levels were highest in patients with the fully developed syndrome but were also elevated in patients at high risk. The absence of significant amounts of IL-1 in serum suggests that it may be produced within the lung.

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.

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).

Inhibition of neutrophil superoxide anion generation by platelet products: role of adenine nucleotides

Previously, we demonstrated the stimulus-specific ability of platelet lysate or release products to inhibit neutrophil functions in response to f-met-leu-phe (fMLP) or phorbol myristate acetate (PMA). The present study further characterizes these activities and identifies one of the platelet inhibitors of neutrophil superoxide anion (O2-) generation. Sephadex G-200 chromatography revealed two fMLP-specific inhibitory activities in platelet lysate. One component eluted with materials less than 13 kilodaltons (kD) molecular weight, whereas the second fractionated at the void volume (Mr greater than 200 kD). PMA-specific inhibitor(s) cofractionated at the void volume with the lysate's fMLP-inhibitory activity. Release products of activated platelets contained low-molecular-weight (less than 13 kD), fMLP-specific inhibitor activity but failed to demonstrate PMA-specific inhibition of neutrophil O2- generation. Biochemical characterization identified two distinct high-molecular-weight inhibitors in platelet lysate. Pretreatment with adenosine deaminase (ADA) completely abrogated the maximum inhibitory effect (43.8 +/- 7.5%) of the high-molecular-weight, fMLP-specific lysate component but failed to reduce maximum PMA-specific inhibition (93.0 +/- 2.0%) of neutrophil O2- generation. Likewise, while the lysate's fMLP-specific inhibitor was heat stable, heating reduced the PMA-specific inhibition 56.5 +/- 10.4%. Equal sensitivity to ADA, resistance to trypsin, and heat stability were demonstrated by the low-molecular-weight inhibitor(s) in platelet lysate and release products. Neither high- nor low-molecular-weight platelet inhibitors scavenged O2-. High-performance liquid chromatography (HPLC) of the low-molecular-weight inhibitory activity from both platelet lysate and release products revealed physiological levels of adenine nucleotides. Addition of pure adenine nucleotides at physiological levels (1-10 microM) mimicked the effectiveness of the platelet inhibitor. We conclude that stimulus-specific limitation of neutrophil O2- generation by platelet adenine nucleotides may represent a mechanism for reducing inadvertent tissue damage during inflammation.

Increased concentrations of leukotrienes in bronchoalveolar lavage fluid of patients with ARDS or at risk for ARDS

The sulfidopeptide leukotrienes (LT) C4 and D4 have been reported to promote the formation of pulmonary edema when administered into the pulmonary circulation of laboratory animals. As a first step in the evaluation of the hypothesis that these leukotrienes participate in the edema formation of the adult respiratory distress syndrome (ARDS), we investigated whether LTC4 and LTD4 were present in the bronchoalveolar lavage (BAL) fluid of patients with ARDS compared to nonsmoker control subjects and to patients with acute respiratory failure exhibiting no radiographic evidence of widespread pulmonary infiltrates but having a clinical predisposition for developing ARDS, i.e., the "at risk" group. Bronchoscopic lavage was performed with sterile 0.9% NaCl on 32 control subjects, nine patients with ARDS, and nine patients "at risk" for ARDS. Leukotrienes were measured in BAL fluid by radioimmunoassay after methanol extraction and HPLC purification of a 20-ml aliquot of the BAL sample. LTC4 and LTD4 (mean +/- SE) increased from 1.1 +/- 0.2 and 1.2 +/- 0.5 ng/lavage in the BAL fluid of control subjects to 6.3 +/- 2.3 and 20.1 +/- 5.9 ng/lavage in patients "at risk" for ARDS and to 12.5 +/- 3.0 and 30.5 +/- 7.8 ng/lavage in patients with ARDS, respectively. The sulfidopeptide LTs correlated with BAL fluid protein content. These results suggest that increased amounts of LTs in BAL fluid are a general finding in patients with ARDS and those "at risk" for ARDS.

Inhibition of neutrophil functions by platelets and platelet-derived products: description of multiple inhibitory properties

The effect of platelets and their products on in vitro responses of human neutrophils to f-met-leu-phe (fMLP) and phorbol myristate acetate (PMA) was studied. Platelets produced a concentration-dependent inhibition of neutrophil superoxide anion (O2-) generation with maximum inhibition of the response to fMLP approaching 42.2 +/- 5.4% and that to PMA approaching 85.9 +/- 3.4%. Supernates of thrombin-activated platelets produced maximal inhibition of neutrophil O2- generation in response to fMLP (66.3 +/- 4.2%) at a ratio of 10 platelet equivalents (PEQ) to 1 neutrophil but failed to affect the cells' response to PMA. In contrast, lysate of sonicated platelets inhibited neutrophil O2- generation in response to both fMLP (59.6 +/- 2.0%) and PMA (90.1 +/- 1.3%). Biochemical characterization of platelet lysate identified at least two stimulus-specific inhibitory activities which differ in size, thermal stability and enzyme sensitivity. Platelet lysate also maximally inhibited neutrophil degranulation and chemotaxis at a ratio of 20 PEQ to 1 neutrophil. Our findings indicate that physiologically achievable levels of platelets or their products modulate the response of neutrophils in a stimulus-specific manner and are thereby capable of potentially limiting tissue damage which accompanies neutrophil activation during inflammation.

The adult respiratory distress syndrome. Cell populations and soluble mediators in the air spaces of patients at high risk

In order to better understand the modulation of polymorphonuclear neutrophil influx into the lung during the development of the adult respiratory distress syndrome (ARDS), we evaluated bronchoalveolar lavage fluids from control subjects (n = 9), patients at high risk of developing ARDS (n = 12), and patients with ARDS (n = 11) for cellular and protein content and capacity to promote neutrophil adhesion to tissue culture plastic. Analysis of the lavage fluids from high risk patients and patients with ARDS showed an 8- to 10-fold increase in the total number of cells, an increase in the percentage of neutrophils present (control subjects = 1 +/- 0.4%, high risk = 53 +/- 8%, ARDS = 70 +/- 7%), and a 10- to 40-fold increase in protein content. The adherence of normal neutrophils to plastic surfaces after pretreatment with either concentrated lavage fluid, ultrafiltrates of BALF, or plasma samples was determined to evaluate the neutrophil adherence-promoting activity of each. Lavage fluid from high risk patients and patients with ARDS promoted an approximate 3-fold increase in neutrophil adherence when compared with control lavage fluid. Neutrophil adhesion-promoting activity of the plasma and lavage filtrates (mw less than 500 daltons) was not significantly different from that of control subjects. The adherence-promoting activity found in ARDS lavage was stable at 56 degrees C for 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Crossed immunoelectrophoretic analysis of ARDS lavage proteins

Serum proteins in normal and ARDS bronchoalveolar lavages were analyzed using crossed immunoelectrophoresis. Normal lavages demonstrated relatively few proteins (albumin, alpha 1-antitrypsin, transferrin, and haptoglobin) in low concentrations. In contrast, substantial amounts of all identifiable serum proteins were detected in ARDS lavages. IgA was apparently locally produced. Two of the largest proteins, beta-lipoprotein (mol wt greater than 2 million) and IgM (mol wt approximately 900,000) were found to be complexed as evidenced by their coprecipitation in a single spike in ARDS lavage. Electrophoretic modifications of ARDS albumin and alpha 1-antitrypsin precipitation peaks and partial identity spurring of the alpha 1-lipoprotein peak with other precipitation loops indicated possible complex formation between these proteins and other possibly pathogenic lung fluid constituents. Similarly, modifications of orosomucoid and Gc-globulin peaks indicated possible molecular alterations resulting from interactions with other components. The relatively few protein modifications exhibited in ARDS lavages together with alpha 1-antitrypsin-protease complex formation confirm the relative absence of substantial proteolytic activity in ARDS edema fluids obtained within 12 hr of the onset of the syndrome demonstrated in previous studies.

In vitro effects of platelet factor 4 on normal human neutrophil functions

Platelet factor (PF4) prepared from human outdated platelets by heparinagarose affinity chromatography was confirmed to be chemotactic for human neutrophils and in a concentration-dependent fashion caused significant release of lysosomal enzymes (myeloperoxidase, lysozyme, beta-glucuronidase) from human neutrophils treated with cytochalasin B. Lysosomal enzyme release from PF4-stimulated neutrophils was rapid and reached a plateau by 1-3 min. PF4 did not cause release of the cytoplasmic enzyme lactate dehydrogenase which indicates that exocytosis of granule-containing lysosomal enzymes did not result from cytolysis. In contrast, superoxide anion generation from human neutrophils stimulated with PF4 was undetectable even at the highest PF4 concentration tested (2 X 10(-5) M). Pretreatment of neutrophils with PF4 caused significant increased adherence of neutrophils to plastic surfaces and cultured pulmonary artery endothelial cells. The concentration of PF4 that elicited neutrophil chemotaxis, lysosomal enzyme release and increased adherence is slightly higher than those concentrations found in normal human sera. However, the results suggest that PF4 may be an important mediator in neutrophil-platelet interactions and the induction of acute inflammation especially at sites of platelet microthrombi where the concentration of PF4 would be elevated.

Adult respiratory distress syndrome: causes, morbidity, and mortality

The increased microvascular permeability of the adult respiratory distress syndrome (ARDS) results in multiple organ injury with the lungs and subsequently the kidneys as the principal targets. Direct pulmonary injury, for example aspiration of gastric contents, and indirect injury, for instance abdominal sepsis, can lead to the syndrome. The predominant infectious cause of the syndrome is gram-negative aerobic rods. Even in patients with noninfectious causes of the syndrome, the incidence of subsequent pneumonia and sepsis with gram-negative aerobic rods is high so that these organisms contribute greatly to the morbidity and mortality that result from the syndrome. Activation of polymorphonuclear leukocytes and platelets and proteolysis of complement and coagulation components contribute to the pathogenesis of the syndrome, particularly from the indirect or blood-borne causes. Therapy is largely supportive and has not progressed substantially since the introduction of positive end expiratory pressure with mechanical ventilation. The outlook for recovery of lung function of survivors is generally good, but only one in three with the syndrome survives. Because of the inflammatory properties of the syndrome, current interest for therapy centers on parenteral use of nonsteroidal antiinflammatory agents and prostaglandins of the E and I series.