Complement-mediated pulmonary edema in sheep

Incubation of plasma with zymosan results in complement activation. Infusion of zymosan-activated plasma (ZAP) into the pulmonary circulation in sheep results in a transient rise in pulmonary vascular resistance, accompanied by hypoxemia. This is associated with production of the vasoactive prostaglandin metabolite, thromboxane. We hypothesized that ZAP infusion caused pulmonary edema and may transiently alter pulmonary permeability to protein. Two sets of experiments were conducted involving six sheep. Three sheep underwent open lung biopsies during ZAP infusion, and electron microscopy documented early reversible interstitial pulmonary edema in response to ZAP infusion. Three other sheep were prepared with lung lymph fistulae and subjected to a similar infusion of ZAP. These studies documented a rapid rise in lymph flow and lymph protein clearance, occurring immediately upon infusion of ZAP. These experiments demonstrate a rapid reversible interstitial edema in sheep lung in response to ZAP infusion and suggest that permeability to protein may be transiently altered as a result of this injury.     

Lung vascular injury with protease infusion. Relationship to plasma fibronectin.

Fibronectin exists in a soluble form in plasma and in an insoluble form in tissues. Plasma fibronectin can modulate phagocytic function as well as incorporate into the tissue matrix where it is believed to influence microvascular integrity and tissue repair. The temporal alterations in plasma and lung lymph fibronectin were studied in relation to increased pulmonary vascular permeability induced by protease infusion. The acute sheep lung lymph fistula model was used. A 39% decrease in plasma fibronectin (control = 421 +/- 67 micrograms/ml) was observed 2.5 hours (255 +/- 43 micrograms/ml) after protease infusion. There was an elevation of lymph fibronectin early after protease infusion, followed by a progressive decline. Concomitant with the decrease in plasma fibronectin, an increase in lymph flow (QL) of greater than 200% (from a control of 6.7 +/- 1.0 ml/hr to 13.9 +/- 1.4 ml/hr) was observed within 2.5 hours. Also, there was a sustained elevation in the total protein lymph/plasma concentration (L/P) ratio, which was maximal at 2.5 hours. The transvascular protein clearance (TVPC = QL X L/P) was 4.5 +/- 0.7 ml/hr at the control period and 13.1 +/- 2.0 ml/hr by 2.5 hours. This was indicative of increased flux of protein-rich fluid across the pulmonary endothelial barrier. Lung vascular permeability stabilized after 2.5 hours as manifested by a slowly declining L/P ratio. Thus, plasma fibronectin deficiency may contribute to the etiology of increased lung vascular permeability with protease infusion. Since the progressive decline in plasma fibronectin was not reflected in a proportional increase in lymph fibronectin, plasma fibronectin may have sequestered in tissues such as the lung, or perhaps in reticuloendothelial cells during the injury phase. Whether the progressive decrease in plasma fibronectin reflects its incorporation into the endothelial barrier matrix where it may mediate stabilization of the pulmonary microvascular barrier remains to be determined.     

The pathophysiology of smoke inhalation injury in a sheep model

This study describes an experimental model of smoke inhalation injury in sheep, in which the same pathophysiologic alterations occur as with clinical inhalation in man. Both the patients and the experimental sheep develop diffuse pulmonary mucosal sloughing, pulmonary edema, and a decrease in systemic oxygen tension. The results of this study indicate that the pulmonary edema is the result of an increase in microvascular permeability, characterized by increases in lung lymph flow (Qlym), lymph-to-plasma protein concentration ratio (L/P), and transvascular protein flux (Qlym X lung lymph protein concentration), while pulmonary vascular pressures remain constant. Neutrophil degranulation may contribute to the increased microvascular permeability.     

Effect of thermal injury on endotoxin-induced lung injury

We studied the effects of a burn injury on the response of the lung to endotoxin. Seventeen unanesthetized sheep with lung lymph fistulas were studied. Eight were given Escherichia coli endotoxin (1.5 micrograms/kg) alone and nine were given the same dose 72 hours after a 25% total body surface burn injury. At this time after burn, all physiologic parameters were at baseline levels. A characteristic two-phase lung injury was seen after administration of endotoxin with an initial hypertension phase, characterized by pulmonary artery hypertension, and a second or permeability phase, characterized by an increase in protein-rich lymph flow. all eight animals that underwent only endotoxin administration survived, whereas four of the nine burned animals died during the permeability phase in pulmonary edema. Major physiologic differences between the groups were noted during the permeability phase, including a more severe hypoxia, pulmonary hypertension, and increased postburn lymph flow. Major biochemical changes included significant increases in lymph thromboxane, thromboxane B2, and beta-glucuronidase activity in the burn group. We conclude that the lung is more sensitive to endotoxin after burn, probably as a result of an increased release of products of arachidonic acid metabolism and products of leukocyte activation caused by the body burn.     

Effect of ONO1714, a specific inducible nitric oxide synthase inhibitor, on lung lymph filtration and gas exchange during endotoxemia in unanesthetized sheep

BACKGROUND: The effect of nitric oxide synthase inhibitor on acute lung injury remains controversial. The current study was designed to examine effects of a newly synthesized and selective inducible nitric oxide synthase inhibitor, ONO1714, on endotoxin-induced lung injury in unanesthetized sheep. METHODS: Thirteen unanesthetized sheep chronically instrumented with a lung lymph fistula and vascular catheters for monitoring were prepared. Animals were randomly allocated into two experimental groups. In experiment 1, sheep (n = 6) were infused only with endotoxin (1 microg/kg) for 30 min. In experiment 2, sheep (n = 7) were pretreated with ONO1714 (0.1 mg/kg) before 30 min of endotoxin administration, and the endotoxin was infused in the same manner as in experiment 1. Mean pulmonary arterial pressure, left atrial pressure, systemic arterial pressure, and lung lymph flow were measured. Observation was continued over 5 h after endotoxin administration. RESULTS: ONO1714 did not cause any pulmonary hemodynamic changes at baseline or exert any influences on transient pulmonary hypertension and increased pulmonary vascular resistance during endotoxemia. However, inducible nitric oxide synthase inhibition with ONO1714 significantly reduced lung lymph filtration and improved abnormal oxygenation during endotoxemia. In addition, increased nitrate-nitrite in plasma and lung lymph in response to endotoxin was prevented by treatment with ONO1714. CONCLUSIONS: These findings suggest that nitric oxide release by the inducible nitric oxide synthase pathway partially contributes to the increased permeability of pulmonary edema and decreased oxygenation during endotoxemia in sheep.     

Pulmonary and systemic fluid filtration after continuous versus bolus interleukin-2 infusion

Interleukin-2 has been widely investigated as adjuvant therapy for advanced cancer and is administered by either bolus or continuous infusion. We compared the effects of bolus and continuous interleukin-2 infusion on pulmonary (QL) and systemic microvascular fluid filtration in 11 adult sheep prepared with chronic lung and soft-tissue lymph fistulas. Interleukin-2 was administered as a bolus infusion (100,000 units/kg) every 8 hours for 3 days or as a continuous infusion at the same dose for 3 days. No significant changes in pulmonary hydrostatic pressures or pulmonary vascular resistance were noted after either bolus or continuous interleukin-2 infusion. However, significantly decreased (p less than or equal to 0.05) systemic vascular resistances were observed in both groups. QL increased steadily throughout the infusion period in both groups, peaking at three times baseline on the third infusion day. The plasma/interstitial protein clearance (QL X lymph/plasma protein ratio) rose similarly in both groups, indicating increased barrier permeability. Increased lymphocyte clearance into lung lymph occurred by day 3 but was not associated with lymphocytic sequestration in the lung interstitium. We conclude that pulmonary and systemic microvascular fluid and protein flux exhibit similar changes after bolus or continuous interleukin-2 infusion. These changes are associated with increased clearance of lymphocytes into lung lymph that are not sequestered in the pulmonary interstitium after infusions of shorter duration.     

Effect of antibody-mediated neutropenia on the cardiopulmonary response to endotoxemia

An ovine anti-neutrophil antibody has been produced by immunizing rabbits with purified sheep neutrophils. Serial intraarterial infusions of anti-neutrophil antibody in awake instrumented sheep produced selective and profound neutropenia. Intravascular infusion of endotoxin (Escherichia coli, 1.5 micrograms/kg/30 min) resulted in significant and equivalent increases in pulmonary artery pressure, peripheral vascular resistance, and protein-rich pulmonary lymph flow in an endotoxin group (n = 9) and a depletion + endotoxin group (n = 4). Changes in cardiopulmonary parameters were most pronounced 2 to 8 hr after endotoxin administration in both groups. Cardiac index (CI) showed a precipitous and transient fall in both experimental groups at 0.5 to 1 hr after endotoxin infusion; however, by 8 hr CI rose significantly in the endotoxin group, while it remained unchanged in the depletion + endotoxin group. A significant rise in the peripheral neutrophil count was associated with the increase in CI in the endotoxin group. Plasma and pulmonary lymph levels of thromboxane-B2 were unchanged during the depletion period with a significant increase 1 hr after endotoxin infusion. In this study questions arise regarding the exclusive role of circulating neutrophils in the microvascular permeability changes seen in sepsis-mediated adult respiratory distress syndrome.     

Chemotactic activity of plasma and lung lymph in sheep with endotoxemia: effect of hydroxyl radical scavengers

The formation and release of circulating chemoattractants has been considered to be responsible for the initial pulmonary leukostasis and subsequent pulmonary vascular injury seen with endotoxemia. Oxygen radicals released from granulocytes can produce these factors. Our purpose was (1) to determine whether chemotaxins are released with endotoxemia and whether the lung is the source of these factors and (2) if there is a cause and effect relationship between the release of chemoattractants and the lung injury. Lung lymph flow, QL, lymph protein clearance, and vascular pressures were used to monitor lung vascular integrity. Escherichia coli endotoxin was infused into 12 sheep. Six sheep were pretreated with dimethyl thiourea (DMTU), a scavenger of hydroxide ion radicals. Chemotactic activity (CA) of plasma and lung lymph was determined during baseline, the pulmonary hypertensive phase, and the permeability phase of the lung injury. It was found that endotoxemia was associated with generation of a granulocyte chemotactic factor in plasma but not in lung lymph. The peak increase in plasma CA occurred after the early pulmonary leukostasis. Pretreatment with DMTU eliminated the increased CA but had no effect on the initial leukopenia or the lung injury. It was concluded that (1) the lung is not the major source of increased CA after endotoxin and (2) increased plasma CA occurs but does not appear to be causative of the initial pulmonary leukostasis or the granulocyte-induced lung injury.     

Lung injury and lung lysosomal enzyme release during endotoxemia

We measured the release of the lysosomal enzymes β-glucuronidase and aryl sulfatase A into lung lymph and plasma after Escherichia coli endotoxin and compared these changes with the pulmonary vascular injury produced. We used 18 unanesthetized sheep, infusing doses of endotoxin from 1 to 10 αg/kg. We identified an early injury phase characterized by severe pulmonary hypertension, a three- to fivefold increase in protein-poor lung lymph flow, and a marked decrease in blood leukocyte count. This was followed several hours later by an increase in vascular permeability with a three- to fivefold increase in protein-rich lung lymph. Lymph lysosomal enzymes increased 200–800% over baseline with a sharp increase occuring during the early hypertension phase. Lymph β-glucuronidase correlated well with the change in vascular permeability measured by lymph flow, r = 0.7. Plasma enzyme values increased, but to a much lesser degree, correlating poorly, r = 0.2, with the lung injury. However, increases over baseline greater than 200% corresponded into with later systemic shock and mortality. We conclude that lysosomal enzymes are released into the lung after endotoxin, probably from sequestered leukocytes, with the degree of release corresponding to the degree of vascular injury.     

Effect of hydroxyl radical scavenging on endotoxin-induced lung injury

The release of oxygen radicals, in particular the hydroxyl radical, from sequestered neutrophils produces acute lung injury after a number of insults. Our purpose was to determine whether hydroxyl radical, OH., is responsible for the lung injury from endotoxin characterized by (1) pulmonary leukostasis, (2) increased thromboxane production leading to pulmonary hypertension and hypoxia, and (3) increased protein permeability. This hypothesis was tested by infusion of a selective OH. scavenger, dimethyl thiourea (0.75 gm/kg), into unanesthetized sheep before endotoxin and comparison of the response to that seen with endotoxin alone. Pulmonary vascular integrity was measured by the use of lung lymph flow, QL, and lymph protein transport. Thromboxane A2 was measured as TxB2 and prostacyclin as 6-keto-PGF1 alpha. We found no difference in the degree of leukopenia and hypoxia after endotoxin or the levels of TxB2, 6-keto-PGF1 alpha, and pulmonary hypertension with dimethyl thiourea, compared with endotoxin alone. The permeability injury was also identical, with a twofold to threefold increase in protein-rich lymph seen in both groups. It appears that OH. does not play a major causative role in either phase of endotoxin lung injury.     

Lower torso ischemia-induced lung injury is leukocyte dependent.

Lower torso ischemia leads on reperfusion to sequestration of polymorphonuclear leukocytes (PMN) in the lungs and increased permeability. This study tests the role of circulating leukocytes (WBC) in mediating this lung injury. Anesthetized sheep prepared with chronic lung lymph fistulae underwent 2 hours of bilateral hind limb tourniquet ischemia. In untreated controls (n = 7), 1 minute after reperfusion there were transient increases in mean pulmonary arterial pressure (MPAP) from 13 to 38 mmHg (p less than 0.05) and pulmonary microvascular pressure (Pmv) from 7 to 18 mmHg (p less than 0.05), changes temporally related to a rise in plasma thromboxane (Tx) B2 levels from 211 to 735 pg/ml (p less than 0.05). Lung lymph TxB2 levels rose from 400 to 1005 pg/ml at 30 minutes (p less than 0.05), and remained elevated longer than plasma levels. Lung lymph flow (QL) rose from 4.3 to 8.3 ml/30 minutes (p less than 0.05) after 30 minutes of reperfusion and remained elevated for 2 hours. The lymph/plasma (L/P) protein ratio was unchanged from 0.6, while the lymph protein clearance increased from 2.6 to 4.6 ml/30 minutes (p less than 0.05), suggesting increased microvascular permeability. WBC counts decreased within the first hour of reperfusion from 6853 to 3796/mm3 (p less than 0.05), and lung histology after 2 hours showed proteinaceous exudates and leukosequestration of 62 PMN/10 high-powered fields (HPF), higher than the 22 PMN/10 HPF (p less than 0.05) in sham animals (n = 3). Recruitment of the pulmonary vasculature by left atrial balloon inflation (n = 3) resulted in a rise in MPAP to 20 mmHg. After 3 hours of balloon inflation, QL stabilized at 9.8 ml/15 minutes, and a pressure-independent L/P protein ratio of 0.3 was achieved. During reperfusion, QL increased further to 11.2 ml/15 minutes, the L/P ratio rose to 0.56 and the calculated osmotic reflection coefficient decreased from 0.70 to 0.44, documenting an increase in lung microvascular permeability. In contrast to these untreated ischemic controls, sheep (n = 7) rendered leukopenic with hydroxyurea or nitrogen mustard and having a total WBC count of 760/mm3 and PMN count of 150/mm3 did not manifest reperfusion-induced increases in MPAP, Pmv, QL, lymph protein clearance, or lung lymph. TxB2 level (p less than 0.05). Plasma TxB2 levels rose slightly at 30 minutes from 199 to 288 pg/ml (p less than 0.05). Lung histology was normal. These data indicate that WBC mediate the ischemia-induced increase in pulmonary microvascular permeability.     

Effect of a body burn on the lung response to endotoxin

Our purpose was, in general, to determine the effect of a body burn on the pulmonary response to endotoxemia and, specifically, to determine whether increased thromboxane (TxA2) production by the burn wound was responsible for the accentuated lung injury. Thirty-two unanesthetized sheep with lung and soft tissue lymph fistulae were studied. Twelve sheep were given a sublethal dose of intravenous E. coli endotoxin (2 micrograms/kg). A characteristic two-phase injury was noted as evidenced by early pulmonary hypertension and hypoxia and later increased lung permeability. TxA2 was significantly increased in lung lymph as well as aortic plasma relative to venous plasma, indicating the lung to be the source. Twelve of 12 sheep survived. Five of 13 sheep died from endotoxemia when given 3-5 days after a 25% total body surface (TBS) burn and five of seven died with endotoxin (2 micrograms/kg) and a 50% burn. Physiologic parameters were at preburn levels before endotoxin. Animals died both during the early phase from hypoxia and the later phase due, in large part, to increasing pulmonary dysfunction. Absolute levels of TxA2 were not increased in the postburn animals, nor was there a clear release of TxA2 from burn tissue to explain the accentuated response. Prostacyclin levels were, however, less elevated in postburn animals in response to endotoxin, thereby altering the TxA2/PGI2 ratio in favor of TxA2. However, a cause and effect relationship between the increased lung injury and TxA2 remains undetermined. Lymph flow or lymph protein content was not altered in burn tissue in response to endotoxin.     

The role of pulmonary lymphatics in the clearance of hydrostatic pulmonary edema

Pulmonary lymphatics are believed to play a major role in preventing the formation of pulmonary edema, but their role in clearance of established edema has not been defined. To measure the lymphatic contribution to the clearance of acute hydrostatic pulmonary edema, a lung lymph fistula was established in 16 anesthetized sheep. Pulmonary edema was induced by a rapid volume infusion of Ringer's lactate (six animals) or homologous plasma (six animals). Four control animals received no fluid. Simultaneous measurements of lymph flow and extravascular lung water (EVLW) were made. Data were analyzed for the resolution phase of pulmonary edema. The contribution of the pulmonary lymphatics to resolution was expressed as a percentage of total lung water resolved. Resolution rates for crystalloid and plasma infusion groups were 3.8 +/- 2.4 cc/kg/hr and 2.7 +/- 1.0 cc/kg/hr, respectively. There was no statistically significant difference between the groups in terms of EVLW increases or resolution rates. Net measured pulmonary lymph flow during the resolution phase of pulmonary edema was 0.33 +/- 0.18 cc/kg/hr and 0.39 +/- 0.20 and accounted for only 8.8 and 14.6% of resolved pulmonary edema in these respective groups. These data suggest the pulmonary lymphatic drainage plays a very minor role in the clearance of acute hydrostatic edema. The lungs appear to be capable of resolving as much as 40% per hour of increased extravascular lung water produced under these circumstances.     

The effect of leukocyte depletion on smoke inhalation injury in sheep

Leukocytes and the production of oxygen radicals and proteolytic enzymes have been implicated in the pathogenesis of lung injury after smoke inhalation. We investigated the mechanism responsible for this form of pulmonary damage in chronically prepared sheep previously made leukopenic with intra-arterial infusions of nitrogen mustard (mechlorethamine hydrochloride). A control air insufflated group (sham: n = 6), a cotton smoke insufflated group (smoke: n = 12), and a leukopenic cotton smoke insufflation group (smoked + depleted: n = 6) were compared. Although both smoke insufflation groups had equivalent smoke exposure, which was indexed by carboxyhemoglobin, the smoked + depleted group had significant attenuation in the increases in pulmonary artery pressure, pulmonary vascular resistance, and pulmonary lymph flow. The PaO2 to FiO2 ratio (P:F) did not fall to the same extent, nor was there a fall in PaO2. The production of oxygen radicals, which was measured as plasma-conjugated dienes, and the consumption of antiprotease, as measured by alpha 2-macroglobulin levels in lung lymph, were not changed in the smoked + depleted group, whereas it was elevated in the smoked group. We conclude that circulating leukocytes and the release of oxygen radicals and proteolytic enzymes contribute to the lung injury, pulmonary microvascular permeability increase, and pulmonary edema seen after smoke inhalation.     

Reperfusion of ischemic lower limbs increases pulmonary microvascular permeability

Lower torso ischemia and reperfusion has been shown to stimulate the generation of thromboxane (Tx)A2, leading to transient pulmonary hypertension and later to polymorphonuclear leukocyte accumulations in the lungs. This study investigated whether hind limb ischemia leads to increased pulmonary microvascular permeability. Anesthetized sheep (n = 6) previously prepared with a lung lymph fistula underwent 2 hr of tourniquet ischemia of both lower limbs. One minute following tourniquet release mean pulmonary arterial pressure (MPAP) rose from 14 +/- 1 to 36 +/- 4 mm Hg (p less than 0.05) and returned to baseline within 30 min. The pulmonary arterial wedge pressure of 4 +/- 1 mm Hg was unchanged. Plasma TxB2 levels rose from 211 +/- 21 to 304 +/- 52 pg/ml (p less than 0.05) 10 min after tourniquet release and were back to baseline at 30 min. Lymph flow (QL) rose from 4.3 +/- 0.6 ml/30 min to 8.3 +/- 1.8 ml/30 min (p less than 0.05); the lymph/plasma (L/P) protein ratio rose slightly but not significantly. In three sheep, inflation of a left atrial balloon increased left atrial pressure from 3 to 16 mm Hg. MPAP rose from 14 to 24 mm Hg. There was an increase in QL from 3.6 to 17 ml/30 min; the L/P protein ratio declined from 0.63 to 0.41. These results indicate that reperfusion following 2 hr of bilateral hind limb ischemia results in increased pulmonary microvascular permeability.     

Lung lysosomal enzyme release during hemorrhagic shock and endotoxemia

Lysosomal enzymes are felt to be released during hemorrhage and endotoxin from ischemic splanchnic viscera and from leukocytes sequestered in the lungs. It is hypothesized that these enzymes then produce endothelial cell damage. Lysosomal enzymes are generally found at highest concentration in lymph draining an injured organ. We determined the extent of β-glucuronidase and aryl sulfatase release into blood and lung lymph during hemorrhagic shock and endotoxemia, correlating this with changes in pulmonary microvascular integrity. We found a 100% increase in plasma β-glucuronidase during fatal hemorrhage but noted no change in the lung lymph concentration. Lung injury was also not seen. After Escherichia coli endotoxin, the plasma levels of both enzymes increased by 100%, while the lung lymph levels increased by 400–600%. A severe alteration in lung permeability was also seen. The actual transport of enzymes in lung lymph increased 20- to 40-fold. We therefore documented a strong correlation between lung injury and changes in lung lymph lysosomal enzyme content, while changes in plasma enzyme content reflected systemic injury.     

Pulmonary dysfunction secondary to soft-tissue endotoxin

Our purpose was to determine whether peripheral soft tissues produce and release prostanoids in response to local sepsis, and whether this mediator release can produce pulmonary dysfunction. Escherichia coli endotoxin (2 micrograms/kg in 100 mL of saline) was injected below the hide of the flank in seven unanesthetized sheep. In three additional sheep, ibuprofen (12.5 mg/kg of body weight) was injected with the endotoxin. Thromboxane B2 and 6-keto-PGF1 alpha (prostacyclin) levels were measured in tissue lymph draining the flank, lung lymph, pulmonary artery (Ppa), and aortic plasma. One hour after endotoxin administration, mean PaO2 decreased from 90 to 74 mm Hg and Ppa increased from 22 to 35 mm Hg. Lung lymph flow (QL) increased only 50% with QL being protein poor. No increase in lung or peripheral soft-tissue vascular permeability was noted. Tissue lymph (TxB2) increased from 220 +/- 114 to greater than 10,000 pg/mL with levels in Ppa plasma increasing from 300 +/- 128 to 595 +/- 124 pg/mL and aortic plasma from 270 +/- 141 to 410 +/- 104 pg/mL. Lung lymph TxB2 paralleled aortic values. Peak levels of 6-keto-PGF1 alpha in systemic lymph exceeded 2,000 pg/mL while levels in lung lymph remained relatively constant. The pulmonary injury and the increase in TxB2 was prevented by ibuprofen. We conclude that the response of soft tissue to local endotoxin is to release thromboxane in quantities sufficient to raise plasma levels and to produce hypoxia and pulmonary hypertension. The lung dysfunction is not produced by an increase in lung water or vascular permeability.     

C1-esterase inhibitor reduces reperfusion injury after lung transplantation

BACKGROUND: Activation of the complement system and polymorphonuclear neutrophilic leukocytes plays a major role in mediating reperfusion injury after lung transplantation. We hypothesized that early interference with complement activation would reduce lung reperfusion injury after transplantation. METHODS: Unilateral left lung autotransplantation was performed in 6 sheep. After hilar stripping the left lung was flushed with Euro-Collins solution and preserved for 2 hours in situ at 15 degrees C. After reperfusion the right main bronchus and pulmonary artery were occluded, leaving the animal dependent on the reperfused lung (reperfused group). C1-esterase inhibitor group animals (n = 6) received 200 U/kg body weight of C1-esterase inhibitor as a short infusion, half 10 minutes before, the other half 10 minutes after reperfusion. Controls (n = 6) underwent hilar preparation only. Pulmonary function was assessed by alveolar-arterial oxygen difference and pulmonary vascular resistance. The release of beta-N-acetylglucosaminidase served as indicator of polymorphonuclear neutrophilic leukocyte activation. Extravascular lung water was an indicator for pulmonary edema formation. Biopsy specimens were taken from all groups 3 hours after reperfusion for light and electron microscopy. RESULTS: In the reperfused group, alveolar-arterial oxygen difference and pulmonary vascular resistance were significantly elevated after reperfusion. All animals developed frank alveolar edema. The biochemical marker beta-N-acetylglucosaminidase showed significant leukocyte activation. In the C1-esterase inhibitor group, alveolar-arterial oxygen difference, pulmonary vascular resistance, and the level of polymorphonuclear neutrophilic leukocyte activation were significantly lower. CONCLUSIONS: Treatment with C1-esterase inhibitor reduces reperfusion injury and improves pulmonary function in this experimental model.     

Effect of ibuprofen on the pulmonary and systemic response to repeated doses of endotoxin

We infused 10 doses of Escherichia coli endotoxin, 1 microgram/kg, during a 5-day period, into eight unanesthetized sheep with lung and systemic lymph fistulas. The animals were then monitored for an additional 5 days. We noted an attenuation of the lung microvascular permeability changes with the later endotoxin doses. However, a 50% increase in cardiac index and oxygen consumption and a leukocytosis were seen beginning with the ninth endotoxin injection; these persisted throughout the 15-day postendotoxin period, as did an increase in pulmonary artery pressure. The hyperdynamic state was present when plasma prostanoids were only modestly increased, and there was no evidence of increased lung or systemic vascular permeability. Postmortem lung findings, 5 days after endotoxin administration, showed a marked interstitial inflammatory response, with infiltration of macrophages, neutrophils, and some lymphocytes and an increase in interstitial fibrous tissue. Six sheep were then given ibuprofen, 12.5 mg/kg, intravenously before the ninth and tenth doses and on the subsequent day. Ibuprofen significantly attenuated the hyperdynamic state and the pulmonary hypertension. In addition, the lung inflammation and fibrous tissue deposition was markedly attenuated. We conclude that a systemic hyperdynamic state develops that corresponds in time with lung inflammation but not with increased permeability. The lung and systemic changes may be blocked by ibuprofen. The ibuprofen effect may be due to a response other than prostanoid production.     

Leukotrienes but not complement mediate limb ischemia-induced lung injury.

Reperfusion after limb ischemia leads to sequestration of polymorphonuclear leukocytes (PMN) in the lungs and to leukocyte- (WBC) and thromboxane- (Tx) dependent respiratory dysfunction. This study examines the intermediary role of the chemoattractants leukotriene (LT)B4 and complement (C) fragments. Anesthetized sheep with chronic lung lymph fistulae underwent 2 hours of tourniquet ischemia of both hind limbs. In untreated controls (n = 7), 1 minute after tourniquet release, mean pulmonary artery pressure (MPAP) rose from 13 to 38 mmHg (p less than 0.05) and returned to baseline within 30 minutes. Pulmonary artery wedge pressure was unchanged from 3.6 mmHg. There were increases in plasma LTB4 levels from 2.46 to 9.34 ng/ml (p less than 0.01), plasma TxB2 levels from 211 to 735 pg/ml (p less than 0.05), and lung lymph TxB2 from 400 to 1005 pg/ml (p less than 0.05). C3 levels were 96% of baseline values. Thirty minutes after reperfusion, lung lymph flow (QL) increased from 4.3 to 8.3 ml/30 minutes (p less than 0.05), lymph/plasma protein ratio was unchanged from 0.6, and the lymph protein clearance increased from 2.6 to 4.6 ml/30 minutes (p less than 0.05), data consistent with increased microvascular permeability. WBC count fell within the first hour from 6853 to 3793/mm3 (p less than 0.01). Lung histology showed leukosequestration, 62 PMN/10 high-power fields (HPF) and proteinaceous exudates. In contrast to this untreated ischemic group, animals treated with the lypoxygenase inhibitor diethylcarbamazine (n = 5) demonstrated a blunted reperfusion-induced rise in MPAP to 17 mmHg (p less than 0.05). There were no increases in LTB4, TxB2, QL or lymph protein clearance (p less than 0.05). WBC count was unchanged and lung leukosequestration was reduced to 40 PMN/10 HPF (p less than 0.05). Decomplementation with cobra venom factor (n = 4) resulted in plasma C3 levels, 10% of baseline, but tourniquet release still led to pulmonary hypertension, elevated LTB4, TxB2 levels, and a decline in WBC count similar to that of untreated ischemic control animals. Histology showed 46 PMN/10 HPF sequestered in the lungs. Further, bilateral hind limb ischemia in either genetically sufficient (n = 10) or deficient (n = 10) C5 mice led to significant lung leukosequestration of 108 and 106 PMN/10 HPF, respectively, compared with 42 and 47 PMN/10 HPF in sham C5(+) and C5 (-) mice (n = 20) (p less than 0.01). These results suggest that the lung leukosequestration and increased microvascular permeability after lower torso ischemia are mediated by the chemotactic agent LTB4, but not by the complement system.