Effects of stroma-free hemoglobin solutions on pulmonary vascular resistance and mediator release in the isolated perfused rabbit lung.

The aim of this study was to evaluate the effect of an ultrapure bovine stroma-free hemoglobin (SFH) on pulmonary vascular resistance and mediator release and to analyze potential mechanisms of action in the isolated perfused rabbit lung model. Repetitive bolus applications of small amounts of bovine SFH were examined which resulted in a reproducible acute increase of pulmonary vascular resistance of approx. 9 mmHg (controls, n = 6). It was tested whether the platelet-activating factor (PAF) antagonist WEB 2086 (50 microM; n = 6), the cyclooxygenase blocker diclofenac (10 micrograms/ml; n = 6), the iron-chelating agent deferoxamine (500 micrograms/ml, n = 6) and the radical scavenger catalase (5000 U/ml; n = 6) exert a protective effect on vasoconstrictor response to SFH. The pressure increase was completely suppressed in the lungs pretreated with WEB 2086, whereas diclofenac, deferoxamine and catalase failed to inhibit the vasoconstriction due to SFH. No significant differences in either TXB2 generation or in histamine release were found in the WEB 2086 group compared with untreated lungs. The results point towards the crucial role of PAF in mediation of vasoconstrictor side effects due to SFH.

Effect of hypertonic NaCl-starch-solution on oedema of different pathogenesis.

Small volumes of hypertonic NaCl-solutions have been proven to restore haemodynamics in hypovolemic shock patients. Topic of this study was to investigate whether bolus application of 7.5% NaCl-6.5% starch-solution (HSS) apart from its relevance in shock might be an effective therapy in oedema. Considering differential therapeutic aspects, the volume effects of 7.2 ml HSS were tested in three types of oedema: hydrostatic oedema induced by venous congestion (n = 6), oedema caused by bradykinin injection (n = 6), and proteinase-induced oedema (n = 6). The arterial, venous pressure and weight changes indicating volume shifts between intra- and extravascular space were continuously monitored in 36 isolated perfused rabbit hindlimbs. Oedema formation was induced corresponding to a weight gain of 18-20 g. Subsequently 7.2 ml HSS were injected into the extracorporeal circulation system containing 200 ml cell free, isoosmotic perfusate. Six experiments of each oedema group without HSS-application served as controls. 75-100% of oedema formation could be remobilised via bolus application of HSS within 5 min in all types of oedema. A persisting weight reduction was detectable in the hydrostatic and bradykinin oedema, whereas in the elastase oedema the initial weight loss was followed by a regain of weight up to 180% of initial oedema formation at 120 min after HSS-application. The results show that, due to the osmotic gradient induced by bolus application of HSS, the hydrostatic and bradykinin oedema can be permanently remobilised, whereas the therapeutic effect during proteinase oedema is only short-lasting due to an irreversible damage of barrier function.

Modulation of pulmonary vascular resistance and edema formation by short-term infusion of a 10% fish oil emulsion.

BACKGROUND: The aim of this study was to investigate whether the pulmonary response to inflammatory stimulation, resulting in increased vascular resistance and permeability, could be attenuated by short-term infusion of triglycerides containing omega-3 fatty acids. With the concept of altering the composition of membrane phospholipids in such a manner that stimulation resulted in the release of less vasoconstrictive and permeability-enhancing metabolites of eicosapentaenoic acid instead of those of arachidonic acid (AA), the parenteral application of a lipid emulsion prepared from fish oil (Omegavenös) was tested in comparison with a soy oil preparation (Lipovenös). METHODS: Isolated lungs from anesthetized rabbits were ventilated and recirculatingly perfused (200 ml/min) with 200 ml cell-free buffer solution to which either 2 ml saline (controls, n = 6), 2 ml Lipovenös 10% (n = 6) or 2 ml Omegavenös 10% (n = 6) were added. To study the possible metabolic alterations in states of an enhanced AA turnover, lungs of each group were stimulated with smaller doses of A23187 (10(-8) M) during the 180-min lipid perfusion period, followed by a 10 times higher calcium ionophore A23187 (10(-7) M) challenge after washing out the lipids by exchange of perfusion fluid. Pulmonary artery pressure (PAP) and the lung weight gain indicating edema formation were monitored, and eicosanoids were analyzed in samples of the perfusate. RESULTS: Upon A23187 injection lung weight gain and PAP increase were significantly reduced (50%) in Omegavenös-perfused lungs in comparison with controls and Lipovenös treatment. The vascular reactions were accompanied by a shifting from LTC4 to LTC5 during and after Omegavenös perfusion. CONCLUSION: The data demonstrate that omega-3 fatty acids seem to be incorporated into the phospholipid pool of the pulmonary tissue, even after short-term infusion (3 h) resulting in an attenuated pressure reaction and edema formation due to an altered spectrum of metabolites in the case of inflammatory stimulation.

Effects of hemorrhage, hypoxia, and intravascular coagulation on bacterial clearance and translocation.

OBJECTIVE: This study was undertaken to discover if impaired blood clearance functions and killing capacity of the reticuloendothelial system contribute to the high occurrence rate of septic complications after shock, trauma, and thermal injury. DESIGN: Prospective, randomized, controlled trial. SETTING: Experimental laboratory in a university teaching hospital. SUBJECTS: Thirty-three standard-breed rabbits of either sex. INTERVENTIONS: Defined numbers of Escherichia coli (1.3 x 10(8)) colony-forming units were injected intravenously 60 min after induction of hypoxia, standardized by defined reduction of oxygen uptake (60% to 75% of baseline) induced by hypoventilation (n = 6) or hemorrhage (n = 6), after complete defibrination caused by the snake toxin, ancrod (n = 6), and after 60 mins without intervention (controls, n = 6). At 180 mins after bacterial injection, the animals were killed and tissue samples of liver, kidney, spleen, and lung were collected for microbiological examinations. MEASUREMENTS AND MAIN RESULTS: Bacterial elimination from the blood and distribution pattern of viable bacteria in liver, spleen, kidney, and lung were investigated in hemorrhagic, hypoxic, and defibrinated rabbits. Compared with controls, there was a distinct alteration of the elimination kinetics of bacteria from the circulating blood in the experimental groups. First, the initial counts of viable E. coli were up to 300% (p < .05) higher in the defibrination, hemorrhage, and hypoxia groups than in controls. Second, greater numbers of E. coli were found in the blood for a significantly (p < .001) longer period, coupled with up to four times higher counts in organ homogenates in the hemorrhagic and defibrinated groups (p < .01) and more than 100 times higher counts than control values in the hypoxic animals (p < .001). CONCLUSION: Hemorrhage, hypoxia, and intravascular coagulation induce impaired bacterial clearance from the blood that is associated with altered organ distribution patterns, thus reflecting dysfunction of the reticuloendothelial system.

Alterations of bacterial clearance induced by endotoxin and tumor necrosis factor.

The purpose of the study was to investigate the potential influence of endotoxin and tumor necrosis factor (TNF) on immune function in terms of systemic clearance and organ distribution of injected Escherichia coli in a rabbit model. To enable quantification of the clearance process, defined numbers of exogenous E. coli (1.3 x 10(8) CFU) were injected intravenously 60 min after bolus application of TNF (4 x 10(5) U, n = 6), after infusion of endotoxin (40 micrograms/kg of body weight) for 1 h (n = 6) or 4 h (n = 6), or after saline infusion (controls, n = 6). Parameters monitored were arterial pressure, oxygen uptake, and rates of bacterial elimination from the blood. At 180 min after E. coli injection, the animals were sacrificed, and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts. Endotoxin infusion produced a significant delay in blood clearance compared with saline and TNF pretreatment. The diminished systemic bacterial elimination was associated with significantly higher numbers of E. coli in the organs, thus reflecting reticuloendothelial system dysfunction. TNF had no major influence on the elimination kinetics of bacteria but affected the tissue distribution pattern with increased accumulation of E. coli in the lung (up to 100-fold of control values; P < 0.001).

Influence of a pentoxifylline-analogue on the granulocyte-mediated pulmonary mediator release and vascular reaction.

The influence of a novel pentoxifylline-analogue, HWA 138, on the polymorphonuclear neutrophil leukocyte (PMN)-mediated changes in pulmonary resistance and mediator release was investigated in the isolated perfused and ventilated rabbit lung model. Isolated, washed human granulocytes were injected into the pulmonary artery and stimulated by either 10(-6) mol/L N-formyl-L-leucin-methionyl-L-phenylalanine (FMP) or 3 x 10(-8) mol/L phorbol 12-myristate 13-acetate (PMA) in the presence or absence (controls) of HWA 138 (10(-4) mol/L). Shortly after granulocyte activation, there was a massive generation and release of thromboxane (> 110 pg/ml) and histamine (150-400 nmol/L), with an acute increase of pulmonary artery pressure (> 8 mmHg) in the control groups. Application of HWA 138 almost completely suppressed mediator formation and release as well as pulmonary vascular reaction in the FMP stimulated group. In contrast to this, HWA 138 was unable to influence either mediator release, the pulmonary pressure reaction or interstitial edema formation following PMA stimulation. In the present model, HWA 138 is supposed to be effective via granulocytes by decreasing mediator release, obviously due to burst reaction.

Alterations of filtration coefficients in pulmonary edema of different pathogenesis.

Different pathomechanisms in the development of pulmonary edema are being discussed. We investigated the effect of pathogenetically varying forms of edema on lung vascular barrier function in isolated cell-free perfused rabbit lungs. As an index of permeability, capillary filtration coefficients (Kfc) were determined from the slope of lung weight change over periods of stepwise venous pressure elevation (5, 7.5, and 10 mmHg) before (controls) and 60 min after edema induction. Edema was induced by venous congestion (n = 6), by application of arachidonic acid in the presence of diclofenac sodium (n = 6), and by elastase application (n = 6). Control values ranged from 0.28 to 0.51 ml.min-1 x mmHg-1 x 100 g-1. Kfc was significantly enhanced after edema induction up to 243% of control value in the hydrostatic edema, 357% in the arachidonic acid edema, and 594% in the elastase edema. When the alterations in capillary filtration due to the different types of edema were compared, Kfc was significantly higher in the proteinase edema, indicating an irreversibly damaged barrier function. These data exemplify different pathophysiological characteristics due to the pathogenesis of interstitial edema formation.