Pulmonary edema due to increased microvascular permeability to fluid and protein

Postpneumonectomy pulmonary oedema

The occurrence of pulmonary oedema was studied retrospectively in 243 patients who underwent pneumonectomy in one hospital from 1975 to 1984. Pulmonary oedema developed in eight of 113 patients who had a right sided pneumonectomy and in three of 130 patients undergoing a left sided procedure. It occurred more commonly in patients requiring a second thoracotomy because of blood loss (in three out of seven patients). There were no significant differences preoperatively in pulmonary function, lung perfusion scans, or cardiovascular condition between patients who subsequently developed pulmonary oedema and those who did not. Postoperative fluid balance was significantly more positive in patients developing pulmonary oedema than in those not developing oedema. Thus pulmonary oedema was associated with right sided pneumonectomy, repeat thoracotomy, and more positive fluid balance.

Changes in regional plasma extravasation in rats following endotoxin infusion

Regional differences in plasma extravasation during endotoxin shock in rats and a possible relationship with changes in regional blood flow were studied with radioactive isotopes (125I-HSA, 51Cr-labeled red blood cells, microspheres) in anesthetized rats (pentobarbital). Shock was induced by intravenous infusion of endotoxin (Eschericia coli; 10 mg X kg-1) for 60 min (starting at t = 0); at t = 120 min, the experiments were terminated. These rats (n = 8) were compared with time-matched control rats (n = 8). A third group (rats killed 7.5 min after injection of 125I-HSA, i.e., no extravasation; n = 8) served as baseline. The amount of plasma extravasated in 2 hr of endotoxin shock was significantly increased over control values in skin (by 67%), colon (88%), skeletal muscle (105%), stomach (230%), pancreas (300%), and diaphragm (1300%). Losses of 125I-HSA into intestinal lumen and peritoneal cavity had also increased over control values by 146 and 380%, respectively. Blood flow was compromised in most organs except heart and diaphragm. Extravasation when normalized for total plasma supply was correlated with total blood supply; the more the blood supply decreased, the higher the normalized extravasation. In the diaphragm, however, blood supply and plasma leakage increased together. Decreased blood supply and plasma extravasation may be related but they could also be simultaneously occurring independent phenomena with a common origin.

Pathophysiology of pulmonary edema following experimental brain death in the chacma baboon

Systemic and pulmonary hemodynamics have been studied during the induction of brain death in the chacma baboon. In 11 animals brain death was induced by acute intracranial hypertension. Continuous recording of blood flow through both the pulmonary artery and the aorta was obtained by electromagnetic flow meters placed around these vessels. Mean arterial, central venous, pulmonary arterial, and left atrial pressures were recorded continuously. Systemic and pulmonary vascular resistances were calculated. During the agonal period marked sympathetic activity occurred, with significant increases in circulating catecholamines and systemic vascular resistance. The great increase in systemic resistance resulted in acute left ventricular failure. Mean left atrial or pulmonary capillary wedge pressure rose above the mean pulmonary arterial pressure in 9 animals. As the systemic vascular resistance rose, a significant difference between pulmonary artery and aortic blood flows occurred, leading to blood pooling within the lungs. A mean of 72% of the total blood volume of the animal accumulated within these organs. The increase of left atrial pressure to levels higher than pulmonary artery pressure indicated a state of pulmonary capillary blood flow arrest. This, associated with the blood pooling within the lungs, almost certainly resulted in disruption of the anatomic integrity of the pulmonary capillaries (blast injury); 4 animals developed pulmonary edema, with alveolar septal interstitial hemorrhage.

The mechanisms and management of noncardiogenic pulmonary edema following cardiopulmonary bypass

Cardiac surgeons have become more cognizant of the syndrome of noncardiogenic pulmonary edema after cardiopulmonary bypass. Although this syndrome is rare, its occurrence can be catastrophic. This article reviews the current understanding of several factors that have been implicated in the cause of this syndrome and discusses the various options for management of the problem once it has arisen.

Respiratory failure following anti-lung serum: study on mechanisms associated with surfactant system damage

Within 2 minutes intravenous anti-lung serum (ALS) into guinea pig induces a respiratory failure that is fatal within 30 min. The relationship between surfactant, alveolar-capillary permeability and respiratory failure was studied. Within two minutes ALS induced a leak in the alveolar-capillary barrier. Within 30 minutes 28.3% (controls, given normal rabbit serum: 0.7%) of iv 131I-albumin, and 0.5% (controls 0.02%) of iv surfactant phospholipid tracer were recovered in bronchoalveolar lavage. Furthermore, 57% (controls 32%) of the endotracheally administered surfactant phospholipid became associated with lung tissue and only less than 0.5% left the lung. The distribution of proteins and phospholipids between the in vivo small volume bronchoalveolar lavages and the ex vivo bronchoalveolar lavages were dissimilar: 84% (controls 20%) of intravenously injected, lavageable 131I-albumin and 23% (controls 18%) of total lavageable phospholipid were recovered in the in vivo small volume bronchoalveolar lavages. ALS also decreased lavageable surfactant phospholipid by 41%. After ALS the minimum surface tension increased. The supernatant of the lavage increased the minimum surface tension of normal surfactant. In addition, the sediment fraction of the lavage had slow surface adsorption, and a marked reduction in 35,000 and 10,000 MW peptides. Exogenous surfactant ameliorated the ALS-induced respiratory failure. We propose that inhibition, altered intrapulmonary distribution, and dissociation of protein and phospholipid components of surfactant are important in early pathogenesis of acute respiratory failure.

Measurement of pulmonary epithelial permeability with 99mTc-DTPA aerosol

The rate at which inhaled aerosol of 99mTc-diethylenetriamine pentaacetate (DTPA) leaves the lung by diffusion into the vascular space can be measured with a gamma camera or simple probe. In normal humans, 99mTc-DTPA clears from the lung with a half time of about 80 minutes. Many acute and chronic conditions that alter the integrity of the pulmonary epithelium cause an increased clearance rate. Thus cigarette smoking, alveolitis from a variety of causes, adult respiratory distress syndrome (ARDS), and hyaline membrane disease (HMD) in the infant have all been shown to be associated with rapid pulmonary clearance of 99mTc-DTPA. Rapid clearance is also promoted by increased lung volume and decreased surfactant activity. Although the mechanism of increased clearance in pathological states is not known, the 99mTc-DTPA lung-clearance technique has great potential clinically, particularly in patients at risk from ARDS and HMD and in the diagnosis and follow-up of alveolitis.

Controversies in the fluid management of post-traumatic lung disease

The appropriate intravenous therapy for injured patients is controversial. Use of colloid-containing solutions has been advocated in an attempt to maintain intravascular colloid osmotic pressure, minimize pulmonary oedema and draw fluid out of areas of contused lung. Studies of animals with lymph fistulas in the lung do not support such therapy and there is no difference between lung water volumes in animals resuscitated for 3 hours with colloid as opposed to crystalloid solutions after a standardized traumatic insult (colloid = 8.4 + 0.8 ml/kg; crystalloid = 7.5 + 0.6 ml/kg). Increased pulmonary capillary permeability makes such therapeutic attempts to 'dry out' the lungs even less effective. Studies in human patients of the rate of extravasation of labelled albumin from the pulmonary intravascular space indicate that increased permeability of pulmonary capillaries occurs early after injury and remains elevated in many severely injured patients. Low plasma colloid osmotic pressures do not correlate with increases in extravascular lung water. A shift to the use of vigorous crystalloid resuscitation of injured patients at our institution has resulted in decreases in both mortality rate (1976-1979, 35 per cent; 1979-1981, 28 per cent) and the rate of dialysis-dependent renal failure (1976-1979, 6 per cent; 1979-1981, 2 per cent). Current evidence supports the use of crystalloid solutions together with blood for resuscitation after injury.

Hemofiltration in septic ARDS. The artificial kidney as an artificial endocrine lung

Twenty-four patients with high microvascular permeability pulmonary edema were initially treated by means of conventional supportive therapy for 1-12 days. Continued deterioration was treated by predilutional hemofiltration and induced a dramatic improvement in 22/24 patients. Survival was 92%. Sieving coefficients for autacoids and middle molecular weight vasoactive peptides involved in the development of high microvascular permeability pulmonary edema were higher than 0.88 indicating that clearing from blood of these peptides during one pass through the hemofilter is similar to that obtained during one pass through the pulmonary normal microvasculature. Hemofiltration seems to be a significant breakthrough in the treatment of ARDS secondary to severe sepsis.

Quantitative morphology of peracute pulmonary lesions in swine induced by Haemophilus pleuropneumoniae

Twenty-seven six-week-old cesarean-derived, colostrum-deprived pigs were inoculated intratracheally with an isolate of Haemophilus pleuropneumoniae serotype 5 (principles) of high virulence (I-200) or low virulence (B-8) or phosphate buffered saline (controls). Pigs given I-200 had severe serofibrinous pleuropneumonia at three hours after inoculation; two of three pigs were dead by 24 hours after inoculation. Interalveolar septa in the caudal lung lobes were 41% thicker than septa from control pigs at three hours after inoculation and 79% thicker by 24 hours after inoculation. Interalveolar septal capillaries in caudal lung lobes were 10.2% larger than control capillaries at three hours after inoculation and 25.6% larger by 24 hours after inoculation. Interalveolar septal capillary platelet volume was greater than the platelet volume of controls; 70% of these platelets were aggregated. There was severe diffuse alveolar, interalveolar septal, and interlobular septal edema at three hours after inoculation with fibrin, neutrophils, and macrophages present in later samples. Thirty-three percent of the lung parenchyma was necrotic at 24 hours after inoculation. Endothelial cell degeneration was generally mild, but necrotic in regions of pulmonary infarction. Pigs inoculated with the B-8 isolate did not develop marked macroscopic lesions at any sampling time. Interalveolar septa were 18% thicker than controls nine hours after inoculation and 5% thicker at six and 24 hours after inoculation. Capillary platelet volume was greatest at nine hours after inoculation with 50% of these platelets aggregated; 30% of the platelet volume was aggregated at the 24-hour sample period. Moderate diffuse pulmonary and interlobular septal edema was present at three, six, and nine hours after inoculation, but absent 24 hours after inoculation. Intravascular macrophages were present in the six, nine, and 24-hour lung samples in both B-8 and I-200 inoculated pigs. These cells were adherent to interalveolar septal capillary endothelial cells and contained phagocytized cellular debris and fibrin. These results indicate the early effects of H. pleuropneumoniae infection involve macrophage and platelet activation, and a marked increase in interalveolar septal capillary permeability.

Thermal dye measurements of extravascular lung water in critically ill patients. Intravascular Starling forces and extravascular lung water in the adult respiratory distress syndrome

To assess the concurrent influence on extravascular lung water (EVLW) content of the intravascular Starling forces, the pulmonary capillary wedge pressure (PCWP), and the colloid osmotic pressure (COP), we measured EVLW by the thermal green dye technique in 174 patients with and without radiographically defined pulmonary edema; in the former group, patients with cardiac (CPE) and noncardiac (NCPE) causes of pulmonary edema were compared (study A). In 119 patients, EVLW was again measured one to three days later (study B). Patients with CPE demonstrated a significantly lower EVLW (9.3 +/- 3.9 ml/kg) (mean +/- SD) than patients with NCPE (14.5 +/- 4.9 ml/kg; p less than 0.05), despite a higher mean PCWP in the former group (20 +/- 7 mm Hg) than in the latter (12 +/- 6 mm Hg; p less than 0.05). In patients potentially with only a hydrostatic cause of pulmonary edema in study A, regression analysis demonstrated the following: EVLW = 3.2 + 0.30 PCWP (r2 = 0.38; p less than 0.005); and in patients with NCPE, EVLW = 10.9 + 0.304 PCWP (r2 = 0.17; p less than 0.01). In study B the change (delta) in EVLW between the two studies was described as follows: delta EVLW = 0.25 + 0.173 delta PCWP (p less than 0.01) + 0.663 group NCPE (p, not significant) + 0.236 group NCPE X delta PCWP (p less than 0.01). This latter equation indicated that the EVLW content manifested a greater change with concurrent alterations in the PCWP in patients with NCPE than was found in patients with only a hydrostatic influence to EVLW formation. Therefore, NCPE is characterized by a greater measurable thermal green dye EVLW than is observed in CPE at any given PCWP, and the PCWP synergistically influences EVLW accumulation in both CPE and NCPE.

Rapid change in pulmonary vascular hemodynamics with pulmonary edema during cardiopulmonary resuscitation

Previous studies have shown that pulmonary edema occurs in half of all pre-hospital cardiac arrest victims who cannot be successfully resuscitated and is a major cause of hypoxemia and poor lung compliance during resuscitation. Pulmonary vascular hypertension and elevation of pulmonary capillary wedge pressure have been observed during cardiac resuscitation in humans. To further define the time course of the pulmonary hemodynamic changes, pulmonary artery diastolic pressure (PAd) was measured on a computerized trend recorder prior to, during, and immediately after arrest in three adult patients. Prior to arrest, PADP was 20.9 +/- 3.1 mm Hg. The PADP rose in all three patients by an average of 30.6% after 5-10 minutes and 71.3% after 10-15 minutes of CPR. Peak PADP reached 35.8 +/- 5.1 mm Hg (difference from pre-arrest level significant, P less than 0.001). In both patients who were resuscitated successfully, the PADP returned to baseline within 5 minutes of effective spontaneous circulation. The finding that such hemodynamic changes occur rapidly during resuscitation and can reverse quickly with resumption of effective spontaneous circulation is consistent with the time course for the early development of pulmonary edema. Development of pulmonary edema many hours following successful resuscitation likely involves other mechanisms.

Binding of charged ferritin to alveolar wall components and charge selectivity of macromolecular transport in permeability pulmonary edema in rats

Rat lungs were inflated and incubated in either anionic or cationic ferritin, and alveolar and capillary basement membranes were examined by electron microscopy. Cationic ferritin bound to heparan sulfate proteoglycans on the external surface of the alveolar basement membrane, whereas cationic ferritin bound to the lamina densa of the capillary basement membranes. Anionic and cationic ferritin was also perfused through the pulmonary circulation of lungs isolated from control rats and rats previously injected with alpha-naphthylthiourea, which produces permeability pulmonary edema. Neither anionic nor cationic ferritin leaked from the pulmonary capillaries in perfused controls; cationic, but not anionic, ferritin adhered to endothelial cell surfaces. In lungs with alpha-naphthylthiourea pulmonary edema, perfused for 2-15 minutes, anionic ferritin leaked from pulmonary capillaries into the alveolar interstitium and alveolar space, while cationic ferritin remained within the capillary lumen. Five times as much anionic ferritin appeared in the capillary basement membranes on the thick side of the alveolar wall, as in the alveolar basement membranes on the thin side of the alveolar wall. In alpha-naphthylthiourea lungs perfused for 45-60 minutes, cationic ferritin also leaked through the injured endothelium and bound twice as much to the alveolar as the capillary basement membranes. The negatively charged pulmonary capillary endothelium, the positively charged capillary basement membranes, and the negatively charged alveolar basement membranes may influence the transport of macromolecules from the pulmonary circulation in permeability pulmonary edema.

Lung injury edema in dogs. Influence of sympathetic ablation

Increased vascular permeability characterizes lung injury pulmonary edema and renders fluid balance in the injured lung especially sensitive to changes in hydrostatic pressure. Pulmonary edema is often associated with increased sympathetic nervous system activity which can lead to pulmonary venoconstriction. This postcapillary venoconstriction could raise microvascular pressure and might therefore increase edema in the injured lung. We produced lung injury edema in dogs with oleic acid and directly measured small (less than 2 mm) pulmonary vein pressure. We found that the small pulmonary vein pressure was increased from 9.8 +/- 0.5 mmHg to 12.6 +/- 0.5 mmHg (n = 10) by oleic acid injury edema. The increase was not due to a rise in left atrial pressure since the small pulmonary vein-left atrial pressure gradient also increased. To test if this increase in the postcapillary pressure gradient was sympathetically mediated, we either unilaterally ablated the stellate ganglion or produced unilateral alpha adrenergic blockade with phenoxybenzamine before giving oleic acid. Both of these "antisympathetic" interventions prevented the increase in pulmonary vein pressure caused by oleic acid edema in the protected lung but not in the intact contralateral lung. These interventions produced a 30 +/- 6.8% reduction in the amount of edema caused by oleic acid. Restoring the increase in small vein pressure by inflating a balloon in the left atrium of dogs with bilateral stellate ganglion ablations abolished the reduction in edema produced by antisympathetic treatment. However, the decrease in edema was not significantly correlated with the reduction in pulmonary vein pressure. Thus, the mechanism of the effects of these antisympathetic interventions remains unclear. We conclude that lung injury edema causes sympathetically mediated pulmonary venoconstriction and that antisympathetic interventions significantly reduce lung injury edema and microvascular pressure.

Effect of positive end-expiratory pressure on lung water in pulmonary edema caused by increased membrane permeability

Pulmonary edema caused by increased membrane permeability was created in dogs by alloxan and infusion of saline solution. Pulmonary extravascular water volume was measured gravimetrically using the supernatant hemoglobin concentration to estimate red cell mass in the calculation of residual pulmonary blood volume. Three groups were studied for two hours: a control group, a group given alloxan and mechanical ventilation without positive end-expiratory pressure (PEEP), and a group given alloxan and mechanical ventilation with 10 cm H2O of PEEP. After two hours, alloxan caused moderately severe pulmonary edema in the two experimental groups, but PEEP had no effect on the accumulation of pulmonary extravascular water volume. No sustained differences in pulmonary or systemic hemodynamics were present throughout two hours of pulmonary edema. The pulmonary shunt was increased in the group without PEEP but was similar in the control group and the group with PEEP. No significant changes in alveolar dead space were noted among the three groups.

Radionuclide evaluation of lung trauma

Nuclear medicine imaging procedures can play a significant role in evaluating the pulmonary complications that are seen in trauma patients. A quantitative method for measuring increased pulmonary capillary permeability that uses Tc-99m HSA allows early diagnosis of acute respiratory distress syndrome (ARDS) and accurately differentiates this condition from pneumonia or cardiogenic pulmonary edema. This technique may be of great value in following the response to therapy. The use of 133Xe to diagnose inhalation injury remains an important diagnostic tool, particularly at hospitals with specialized burn units. Regional decreases in ventilation-perfusion images reliably localize aspirated foreign bodies. Radionuclide techniques that are used to demonstrate gastropulmonary aspiration remain controversial and require further clinical evaluation. Pulmonary perfusion imaging, although nonspecific, may provide the earliest clue for correct diagnosis of fat embolism, air embolism, contusion, or laceration. Furthermore, the possibility of perfusion abnormality due to these uncommon conditions must be remembered whenever trauma patients are evaluated for pulmonary thromboembolism with scintigraphy. Occasionally, liver or spleen scintigraphy may be the most appropriate procedure when penetrating chest trauma also involves these subdiaphragmatic organs.

Concepts in the pharmacologic and nonpharmacologic support of cardiovascular function in critically ill surgical patients

The critically ill surgical patient requires close clinical, biochemical, and hemodynamic monitoring to define the right timing as well as the proper type of therapeutic intervention. Although many factors are available for monitoring, O2 delivery and extraction are two of the most important, since the enhanced metabolic demands of the stressed patient dictate a need to maintain greater than normal values to ensure survival. In other situations, primary therapy of the blood pressure, the PCWP, or other indices may take temporary precedence in the choice of therapeutic agents. Regardless of the means used to optimize O2 delivery, scrutiny of the consequences of therapy is equally important. Above all, any therapeutic intervention does not negate the need to treat the primary underlying process expeditiously.

Role of endothelial cell cytoskeleton in control of endothelial permeability

Increased permeability of the pulmonary microvasculature is felt to cause acute noncardiogenic lung edema, and histological studies of edematous lungs show gaps between apparently healthy endothelial cells. To determine whether alterations in endothelial cell cytoskeletons would alter endothelial permeability, we exposed monolayers of pulmonary artery endothelial cells grown on micropore filters to cytochalasin B or D. Cytochalasin exposed monolayers demonstrated a 2- to 3-fold increase in endothelial permeability that was readily reversible by washing the monolayers free of cytochalasins. Parallel phase contrast and fluorescence microscopy demonstrated retraction of cell cytoplasm and disruption of bundles of microfilaments in cytochalasin exposed cells. These changes also were readily reversed after washing the cells free from cytochalasins. To test the relevance of these findings to an in situ microvasculature, we added cytochalasin B to the perfusate of isolated rabbit lungs and observed that cytochalasin B caused a high permeability lung edema. These studies suggest that endothelial cell cytoskeletons may be important determinants of endothelial permeability.

Mechanisms of lung vascular injury after intravascular coagulation

Pulmonary intravascular coagulation and the resultant microembolization increase lung vascular permeability to proteins. The increase in permeability is mediated by the activation of cellular and humoral factors after intravascular coagulation. In particular, intravascular coagulation results in sequestration and activation of leukocytes, which appears to be of primary importance in mediating the lung vascular injury. In addition, fibrin entrapment and the generation of fibrin-degradation products after fibrinolysis also contribute to the vascular injury. The classical inflammatory agents, such as prostaglandin, histamine, bradykinin, and serotonin, may modulate the degree of injury after pulmonary vascular thrombosis, but they do not appear to be the primary mediators of the injury. Platelet aggregation did not mediate the lung vascular injury after intravascular coagulation, but was responsible for the pulmonary gas-exchange impairment that occurs with pulmonary vascular thrombosis.

Non-hydrostatic pulmonary edema after coronary artery ligation in dogs. Protective effect of indomethacin

Pulmonary edema which develops during acute myocardial infarction is generally believed to result solely from pulmonary microvascular hypertension. However, patient with myocardial infarction and pulmonary edema occasionally are found to have normal pulmonary wedge pressure. We report data indicating that pulmonary edema develops after coronary artery ligation despite stable microvascular pressure. Four groups of open-chest dogs were studied: (1) nine dogs with left anterior descending coronary artery ligation, (2) seven dogs with sham coronary ligation, (3) seven dogs ligated after beginning an infusion of indomethacin (5 mg/kg per hr), and (4) five dogs ligated after an infusion of the drug's vehicle was begun. Extravascular lung water and pulmonary blood volume were measured at hourly intervals during the 2 hours before and after coronary ligation or sham ligation. Gravimetric lung water was measured immediately thereafter. Changes of net pulmonary intravascular driving force (the difference of microvascular hydrostatic and oncotic pressure) after ligation or sham ligation were small and comparable in all groups. Pulmonary blood volume did not change in any group. Pulmonary extravascular water volume remained constant in the sham group but rose significantly in the ligated group. Gravimetric lung water also was significantly higher in the latter group. We interpret these results to indicate that factors other than microvascular pressure can mediate the formation of these results to indicated that factors other than microvascular pressure can mediate the formation of edema during acute myocardial infarction; increased pulmonary microvascular permeability may be responsible. Indomethacin infusion blocked the formation of edema after coronary ligation, even though net microvascular driving force was highest in this group. Infusion of the vehicle alone did not prevent edema. The mechanism by which indomethacin exerts this protective effect is unclear but is probably a result of its inhibition of cyclo-oxygenase or cyclic nucleotide phosphodiesterase.

Experimental neurogenic pulmonary edema Part 2: The role of cardiopulmonary pressure change

Pressure changes in the aorta, left atrium, and main pulmonary artery were measured before, during, and after inducing increased intracranial pressure in cats. By selectively controlling each of the three pressures, it was concluded that pulmonary arterial hypertension is the single most important precursor of experimental neurogenic pulmonary edema. An earlier observation that neurogenic pulmonary edema may develop in the absence of systemic arterial hypertension was confirmed.

Neurogenic pulmonary edema in unexpected, unexplained death of epileptic patients

Eight cases of unexpected, unexplained death in young ambulatory epileptics were examined postmortem with special attention to the heart and lungs. Lung weights uniformly exceeded the expected value, with gross evidence of hemorrhagic pulmonary edema. Microscopic examination revealed moderate to severe pulmonary edema with protein-rich fluid as well as alveolar hemorrhage. There was no evidence of recent or old myocardial disease. Although death due to a seizure is usually thought to be almost instantaneous, the neurogenic pulmonary edema exemplified by these cases takes time to develop and may be remediable. The high frequency of absent or non-therapeutic anticonvulsant levels at the time of death in these patients may play a role in a possible centrally mediated adrenergic cause of neurogenic pulmonary edema and ventricular arrhythmia.

Vascular permeability and transvascular fluid and protein transport in the dog lung

We used steady state lymph-to-plasma concentration ratios of six endogenous protein fractions (effective hydrodynamic radii of 37, 40, 44, 53, 100, and 120 A) to estimate pulmonary capillary permeability characteristics. Pulmonary lymph was collected from an afferent lymphatic to the left tracheobronchial lymph node, and left atrial pressure was elevated in steps until the lymphatic protein concentration obtained a constant value. Lymph flow and transvascular protein flux increased with each increase in left atrial pressure. Convective flux was the predominant mode of transport for the smaller fractions, and solvent-drag reflection coefficients increased as lymph flow increased. This dependency on lymph flow (capillary filtration) indicates a heteroporous membrane system. For lymph flows greater than five times control, the solvent-drag reflection coefficients were: 0.59 +/- 0.11, 0.52 +/- 0.06, 0.66 +/- 0.05, 0.70 +/- 0.05, 1.01 +/- 0.04, and 1.05 +/- 0.03 for the six fractions. Osmotic reflection coefficients estimated from the minimal lymph-to-plasma concentration ratios were: 0.50 +/- 0.03, 0.59 +/- 0.02, 0.67 +/- 0.04, 0.72 +/- 0.03, 0.94 +/- 0.01, and 0.96 +/- 0.01 for the six protein fractions. The osmotic reflection coefficients are consistent with a two- "pore" exchange model possessing equivalent pore radii of 80 and 200 A. Theoretical considerations indicate that only the two largest protein fractions (100 A and 120 A radii) achieved filtration-independent concentrations in pulmonary lymph, even at the highest filtration rates. This suggests that the reported osmotic reflection coefficients of the four small protein fractions underestimate their true values.

Leukocytes are required for increased lung microvascular permeability after microembolization in sheep

We studied the effects of uneven pulmonary artery obstruction by microemboli on steady state transvascular fluid and protein exchange in normal and leukopenic sheep. We measured pulmonary artery and left atrial pressures, cardiac output, lung lymph flow, and lymph plasma protein concentrations. Sheep were made profoundly leukopenic by administration of intra-arterial mechlorethamine hydrochloride (0.4 mg/kg, two doses) and colchicine (0.1-0.2 mg/kg, anesthetized sheep only). In anesthetized sheep, we injected glass beads 200 micrometers in diameter via the right atrium to raise pulmonary vascular resistance to 2-3 times baseline values. With normal levels of circulating leukocytes, sheep developed an increased protein-rich lymph flow from the lung characteristic of increased permeability edema. Leukopenic sheep had a significantly attenuated response after embolization for equivalent degrees of vascular obstruction. In unanesthetized sheep, we continuously infused air bubbles 1 mm in diameter via the right atrium to raise pulmonary vascular resistance to about 2 times baseline values. Each sheep served as its own control. With normal circulating leukocyte levels, there was an increase in protein-rich lymph flow from the lung during embolization. When the air infusion ended, the sheep recovered to the baseline condition in 24 hours. We induced emboli with the same amount of air when the sheep were profoundly leukopenic; lymph and protein flow from the lung were significantly less for equivalent degrees of obstruction. We conclude that circulating leukocytes are essential for the microvascular injury that results in increased permeability in the lungs of sheep after microembolization.

The pathophysiology of disorders of oxygen transport in the infant

The major attempt in this monograph has been to provide a systematic approach to OT in the infant under normal and abnormal conditions based on an appreciation of pathophysiologic mechanisms. This has included a consideration of oxygen uptake, gas transfer from the lungs to the circulation, oxygen delivery to the tissues, and various adaptive responses. We have discussed disorders involving the control of respiration, the upper and lower airways, lung parenchyma, pulmonary circulation, heart, and the oxygen carrier, hemoglobin, that may impair OT to tissues, and how compensation for these conditions can be achieved. The clinical presentation in each of these pathologic processes represents the net effect of the lesion on the multiple steps involved in the transport of oxygen to the tissues and the adaptation provided by the lungs, heart, circulation, and hematologic system. These must be taken into account in developing a plan for medical and/or surgical treatment that is focused on improving the supply of oxygen to the various organ systems of the body.

Edema fluid and coagulation changes during fulminant pulmonary edema

Edema fluid and a coagulation profile were obtained in 45 patients (17 to 87 years) during fulminant pulmonary edema. Left ventricular failure and/or volume overload accounted for edema in 18 patients. In another 27 patients, edema developed in association with other features that typify the adult respiratory distress syndrome (ARDS). In the ARDS group, multiple disorders were implicated in the genesis of edema, including shock, bacteremia, drug overdose, and aspiration. Assessment of edema fluid and coagulation measurements is useful to classify and to determine the severity of the edema process. ARDS is characterized by permeability pulmonary edema that usually stems from a combination of multisystemic disorders. Permeability pulmonary edema and coagulation changes appear to be interrelated. However, it is not clear the extent to which the coagulation disturbances are a cause or a result of the alterations in the alveolar-capillary membrane.

Atrax robustus envenomation

Two patients who developed massive pulmonary oedema, profound vasoconstriction and hypertension followed by hypotension after Atrax Robustus envenomation are described. The pulmonary oedema is due to increased pulmonary capillary membrane permeability which may be due to neurogenic or toxic causes. Use of artificial ventilation with high level PEEP, isoprenaline and high dose steroids allowed support of the patients during volume replacement with albumin. When the circulation was stable and airway frothing ceased, conventional dehydration therapy further improved lung function. Both patients were discharged well.