Drug-induced pulmonary edema and acute respiratory distress syndrome.

Noncardiogenic pulmonary edema, and, to a lesser extent, acute respiratory distress syndrome (ARDS), are common clinical manifestations of drug-induced lung diseases. Clinical features and radiographic appearances are generally indistinguishable from other causes of pulmonary edema and ARDS. Typical manifestations include dyspnea, chest discomfort, tachypnea, and hypoxemia. Chest radiographs commonly reveal interstitial and alveolar filling infiltrates. Unlike pulmonary edema that is due to congestive heart failure, cardiomegaly and pulmonary vascular redistribution are generally absent in cases that are drug-related. Rare cases of drug-induced myocarditis with heart failure and pulmonary edema have been described. Results from laboratory evaluation and respiratory function tests are nonspecific.

Inhibition of cytochrome P-450 attenuates hypoxemia of acute lung injury in dogs.

The intravenous administration of ethchlorvynol (ECV), in dogs, resulted in an acute lung injury (ALI) characterized by a 200 +/- 80% increase in venous admixture and a 142 +/- 30% increase in extravascular lung water (EVLW). Pretreatment with the cytochrome P-450 inhibitor 8-methoxypsoralen prevented the ECV-induced increase in venous admixture but not the increased EVLW. These findings parallel those reported for cyclooxygenase inhibition in ECV-induced ALI and suggest that an arachidonic acid (AA) metabolite of pulmonary cytochrome P-450 activity may mediate the increase in venous admixture of ALI. We demonstrate that canine pulmonary microsomes metabolize [1-(14)C]AA to a variety of products, including the cytochrome P-450 metabolites 5,6-, 8,9-, 11,12-, and 14,15-epoxyeicosatrienoic acid (EET). In prostaglandin F2 alpha-contracted, isolated pulmonary venous rings, 5,6-EET induced relaxation in a concentration-dependent manner. This action of 5,6-EET was prevented by indomethacin (10(-5) M). These results suggest that may serve as the cyclooxygenase-dependent endogenous pulmonary vasodilator responsible for the increase in venous admixture of ECV-induced ALI.

Inhibition of nitric oxide synthesis improves arterial oxygenation in ethchlorvynol-induced acute lung injury in dogs.

In both humans and in experimental animals, acute lung injury (ALI) is characterized by the development of pulmonary edema and arterial hypoxemia. It has been reported that the hypoxemia of ALI is related to the failure of those mechanisms that result in the diversion of blood flow away from hypoxic (edematous) lung units to those that are well oxygenated. One such mechanism is hypoxic pulmonary vasoconstriction (HPV). In the pulmonary circulation, endogenous nitric oxide (NO) has been shown to oppose HPV and, thereby, to support blood flow to hypoxic alveoli. In the present work we investigated the hypothesis that, in ALI, endogenous NO, by virtue of its ability to oppose HPV, supports blood flow to hypoxic lung units resulting in increases in venous admixture (Qva/Qt) and decreases in arterial oxygen tension (PaO2). In anesthetized and mechanically ventilated dogs, the intravenous administration of ethchlorvynol (ECV, 15 mg/kg) resulted in an increase in extravascular lung water (EVLW) of 10 +/- 1 ml/kg body wt (p < 0.001) as well as a 120 +/- 45% increase in Qva/Qt (p < 0.01) and a 23 +/- 5% decrease in PaO2 (p < 0.01) (n = 3). L-NAME (1 mg/kg iv, followed by 5 mg/kg/h, iv), administrated 60 min after ethchlorvynol (ECV), prevented entirely the ECV-induced increase in Qva/Qt and fall in PaO2 with minimal effect on EVLW (n = 3). We conclude that, in this model of ALI, endogenous NO is present in the lung and acts to support blood flow to poorly oxygenated lung units resulting, thereby, in reductions in PaO2.

Effect of hydroxyethyl starch on alveolar flooding in acute lung injury in dogs.

The efficacy of hydroxyethyl starch (HES) in limiting alveolar flooding after acute lung injury was investigated using ethchlorvynol (ECV)-induced low pressure pulmonary edema in dogs. Harvested autologous plasma (PL) (control, n = 8) or 6% HES (n = 8) was infused (25 ml/kg) along with packed cells to result in an isovolemic, normochromic preparation before the administration of ECV. Extravascular thermal volume significantly increased after ECV administration in both groups of animals (6.6 to 13.4 ml/kg in PL, 6.5 to 15.0 ml/kg in HES). Systemic arterial PO2 decreased from 216 +/- 4 to 113 +/- 20 mm Hg, and venous admixture increased from 2.8 to 12.8% in the PL group but was not significantly changed in the HES group (219 +/- 5 to 203 +/- 8 mm Hg, and 2.9 to 4.4%, respectively). Epithelial lining fluid volumes after ECV administration increased in both groups but were elevated in the PL group to a greater extent than in the HES group (13.5 ml in HES versus 24.8 ml in PL). In the HES group there appeared to be no difference in the ability of plasma proteins to move across the alveolar epithelium. These results suggest that HES attenuates the flooding of the alveolar space and the resulting alterations in gas exchange during the development of low pressure pulmonary edema. The replacement of the plasma proteins with HES and the apparent inability of HES to cross the epithelial barrier into the alveoli may account for the protective effect of HES in these experiments.

The effects of amrinone and calcium chloride on pulmonary vasculature and biventricular function in ethchlorvynol-induced lung injury in sheep.

The effects of amrinone and CaCl2 on pulmonary vasculature and biventricular function in sheep with acute lung injury (ALI) were studied. Seven sheep were ventilated with a tidal volume of 10-12 ml.kg-1 with end-tidal CO2 of 40 +/- 5 mmHg (5.3 +/- 0.7 kPa) after acute lung injury was induced with up to 30 mg kg-1 of ethchlorvynol (ECV). Biventricular function and hemodynamic profiles were estimated with a rapid computerized thermodilution method and modified pulmonary artery catheters after acute lung injury, following a loading dose (1 mg kg-1) and maintenance dose (5 micrograms kg-1 min-1) of amrinone and after a bolus dose of CaCl2 (20 mg kg-1). ECV successfully induced acute lung damage in sheep, causing significant increases in pulmonary artery pressure (PAP) and pulmonary vascular resistance index (PVRI). Amrinone reversed the unfavorable changes induced by ECV, significantly reducing PAP, PVRI and left ventricular end-diastolic volume (LVEDV). CaCl2, however, reversed the effect of amrinone and increased PAP, PVRI, and LVEDV but decreased left ventricular ejection fraction.

Effect of tidal volume and PEEP in ethchlorvynol-induced asymmetric lung injury.

We examined the effects of positive end-expiratory pressure (PEEP) and tidal volume on the distribution of ventilation and perfusion in a canine model of asymmetric lung injury. Unilateral right lung edema was established in 10 animals by use of a selective infusion of ethchlorvynol. Five animals were tested in the supine position (horizontal asymmetry) and five in the right decubitus position (vertical asymmetry). Raising PEEP from 5 to 12 cmH2O improved oxygenation despite a redistribution of blood flow toward the damage lung and a consistent decrease in total respiratory system compliance. This improvement paralleled a redistribution of tidal ventilation to the injured lung. This was effected primarily by a fall in the compliance of the noninjured lung due to hyperinflation. The effects of higher tidal volume were additive to those of PEEP. We propose that the major effect of PEEP in inhomogeneous lung injury is to restore tidal ventilation to a population of alveoli recruitable only at high airway pressures.

Ibuprofen reduces ethchlorvynol lung injury: possible role of blood flow distribution.

The role of cyclooxygenase products in acute lung injury was determined by pretreatment of dogs with ibuprofen before injury with intravenous ethchlovynol (ECV). In animals given ECV only, lung injury resulted in extravascular lung water of 18.9 ml/kg after 2 h, which was significantly higher than the 14.8 ml/kg in the group pretreated with ibuprofen. The comparison of gravimetric and indicator-dilution measurements of edema fluid indicates that edema fluid could not be reliably detected after treatment with ibuprofen because of diversion of flow from injured areas. Venous admixture increased from 6% at baseline to 32% 120 min after ECV in the vehicle-pretreated group compared with an increase from 4% at baseline to 7% in the ibuprofen-pretreated group. The regression analysis of the relationship between venous admixture and extravascular lung water indicated that, at any level of edema, venous admixture was significantly less in the group treated with ibuprofen than in the untreated group. Measurement of plasma and bronchoalveolar lavage fluid indicated that ibuprofen inhibited cyclooxygenase activity without affecting lipoxygenase activity. These results suggest that in intact dogs ibuprofen has a protective effect on both pulmonary gas transfer and pulmonary edema formation in ECV-injured lungs, which is consistent with limiting blood flow to injured segments of the lung.

Cyclooxygenase inhibitors prevent ethchlorvynol-induced injury in rat and rabbit lungs.

The effect of three chemically dissimilar cyclooxygenase inhibitors on ethchlorvynol-(ECV) induced acute lung injury was studied in isolated buffer-perfused rat and blood-perfused rabbit lungs. ECV caused the microvascular fluid filtration coefficient (Kf) to increase by greater than threefold in the rat lungs and twofold in the rabbit lungs. ECV caused increased pulmonary vascular resistance (PVR) and microvascular pressure measured by the double occlusion technique (Pdo) compared with the vehicle control group in the rat experiments. However, ECV had no effect on PVR or Pdo in the rabbit experiments. Pretreatment with the cyclooxygenase inhibitors indomethacin, ibuprofen, and meclofenamate prevented the increase in microvascular permeability in both the rat and rabbit lung preparations. The cyclooxygenase inhibitors also prevented the ECV-induced PVR and Pdo increases in the rat lungs but had no effect on PVR or Pdo in the rabbit lungs. These results indicate that cyclooxygenase products of arachidonate metabolism mediate the ECV-induced Kf increase in both isolated rat and rabbit lungs.

Ethchlorvynol ingestion in San Diego County: a 14-year review of cases with blood concentrations and findings.

Cases of nonfatal (51) and fatal (38) ingestions involving ethchlorvynol over a 14-year period (1975 through 1988) were reviewed in order to evaluate the current status of ingestion of this drug. In both series of cases men and women were involved approximately equally. Sixty-three percent of cases in both series occurred during the period 1975 through 1980. Most (78% of nonfatal and 89% of fatal) ingestions involved other drugs in addition to ethchlorvynol. Physical findings for nonfatal ingestions and causes of death for fatal ingestions are presented. Blood ethchlorvynol concentrations are discussed, and a composite of the average patient for each series is presented. Although ethchlorvynol abuse appears to be decreasing with time, it still occurs, and a search for this sedative-hypnotic agent should be included in the so-called "toxicology screen."

Ethchlorvynol overdose.

Ethchlorvynol remains a drug that frequently surfaces in clinical emergency practice despite safer and more effective pharmaceutical agents on the market. Effects such as poisoning, dependence, ocular damage, and overdose continue to receive attention in the literature. Awareness of complications and treatment in ethchlorvynol exposure requires attention to a drug remaining clinically available without an appropriate clinical indication.

Reduced venous admixture in hemorrhagic hypovolemia: maintenance of arterial oxygenation by selective pulmonary vascular collapse.

In nine anesthetized and ventilated swine, a microcomputer calculated cardiac output, venous admixture (Qsp/Qt) and physiologic deadspace (VD/VT) every 20 sec, utilizing dual oximetry and a gas exchange analyzer. After lung injury with ethchlorvynol (ECV), animals were bled 40% blood volume over 40 min. Mean cardiac output decreased 7.0 to 2.2 L/min (p less than .05) accompanied by a decrease in mean Qsp/Qt from 0.28 to 0.14 (p less than .05) and an increase in mean VD/VT from 0.39 to 0.54 (p less than .05). Arterial Hgb saturation (Sao2) increased from 88 +/- 7% to 90 +/- 6%. On regression of all data points for each variable, Qsp/Qt had a positive correlation with cardiac output (r = .90), mean arterial pressure (MAP, r = .87), mean pulmonary artery pressure (MPAP, r = .86), and mixed venous Hgb saturation (Svo2, r = .89, p less than .001). VD/VT had an inverse correlation with cardiac output (r = -.90), MAP (r = -.82), Qsp/Qt (r = -.83), MPAP (r = -.77), and Svo2 (r = -.92, p less than .001). The decreasing Qsp/Qt and increasing VD/VT, with decreasing pulmonary perfusion pressures, were attributed to selective loss of perfusion to alveoli with low ventilation/perfusion ratios.

Pleural effusions associated with ethchlorvynol lung injury result from visceral pleural leak.

Traditional thinking suggests that pleural fluid develops on the basis of systemic venous hypertension or a primary pleural process. Recent investigations, however, indicate that both acute lung injury and pulmonary venous hypertension can be important in the pathogenesis of pleural effusions. To evaluate the role of acute lung injury in the formation of pleural effusions, we developed a model of acute, reversible lung injury in NZW rabbits. Intravenous ethchlorvynol (ECV), known to produce permeability edema in humans, was used to produce permeability pulmonary edema in rabbits. The injury was examined over 14 days with bronchoalveolar lavage, pleural fluid analysis, and morphologic analysis. Ethchlorvynol injection (40 mg/kg) produced a PMN-predominant, exudative alveolitis (2 h), alveolar hemorrhage (6 to 10 h), and pleural effusions by 2 h (peak, 10 h). Pathologic findings included a patchy, subpleural, hemorrhagic PMN inflammatory response, which peaked by 24 h, and an acute PMN vasculitis of small arterioles and capillaries; these changes resolved in 5 to 7 days. No parietal pleural abnormalities were observed. We conclude that ECV induces an acute, reversible parenchymal lung injury resulting in a capillary leak and that fluid moves from the interstitium of the lung into the pleural space along a pressure gradient through a relatively permeable mesothelium. The data support the concept that diffuse or localized lung injury can result in pleural effusions.

Body distribution of ethchlorvynol.

Ethchlorvynol (Placidyl) is a nonbarbiturate sedative hypnotic. Two fatal cases of ethchlorvynol overdose are reported. Toxicological analyses of body fluids and tissues were performed by gas chromatography using a flame-ionization detector. The quantitative method was sensitive and reproducible. Body distribution of ethchlorvynol in blood and other tissues is presented. Biological samples analyzed included blood, urine, bile, liver, kidney, eye fluid, and gastric contents. Results presented add to the pharmacokinetic data needed to study the disposition of drugs in different tissues. Findings in present two cases are compared with published toxicological data.

Swine model of early adult respiratory distress syndrome induced by intravenous ethchlorvynol.

Although ethchlorvynol (ECV) has been used to induce pulmonary damage in animals, changes after injection of this drug have not been studied, nor has the stability of the animal been assessed after injection. Continuously monitored hemodynamic and respiratory changes were followed during and after iv injection of 55 mg/kg ECV in ethanol into anesthetized, paralyzed, and ventilated swine (n = 5) and compared to changes in a control group given ethanol alone (n = 5). Arterial and mixed venous saturations were measured by fiberoptic vascular catheters and oxygen exchange by a gas monitor. Twelve direct and derived variables were monitored every 20 sec using a computer data acquisition system. Arterial oxygen saturation was kept at 90 +/- 2% by adjustment of FIO2. Ethanol produced only transitory changes during infusion. Significant elevations in pulmonary vascular resistance (PVR), shunt (Qsp/Qt) and deadspace (VD/VT) were observed during and after ECV. These were unaccompanied by changes in cardiac output or arterial pressure. PVR increased by 137%, Qsp/Qt by 67%, and VD/VT by 28% over 30 min. These changes were then sustained in the postinfusion period, producing a stable model of early adult respiratory distress syndrome for 3.5 h.

Bilateral exudative pleural effusions following intravenous ethchlorvynol administration.

A 26-year-old man had bilateral alveolar infiltrates and exudative pleural effusions following self-administration of intravenous ethchlorvynol (ECV). The effusions and pulmonary edema resolved by 72 h with supportive therapy only. As no other etiology was established, we concluded that the pathogenesis of the pleural fluid was the transvisceral pleural leak of the increased extravascular lung water induced by ECV. Current experimental and clinical evidence support the concept that pleural effusions probably develop in most states of permeability pulmonary edema.