Sb Oetomo

Distribution of exogenous surfactant in rabbits with severe respiratory failure : the effect of volume

ABSTRACT: The transient effect of surfactant therapy that is observed in some patients might, at least in part, be explained by a nonhomogeneous distribution. Therefore, we investigated the distribution of a surfactant preparation (Alvofact, 45 g/L) that is used clinically. Rabbits with severe respiratory failure were treated with this surfactant at a dose of 100 mg/kg body weight, and the distribution of surfactant was determined by the use of 141Ce-labeled microspheres that were mixed with the surfactant. Fifteen min after surfactant administration, the rabbits were killed, and the lungs were removed and divided into 200 pieces. The radioactivity per mg lung tissue was determined in each piece. We found that the endotracheal instillation of this surfactant preparation results in a nonhomogeneous distribution. However, a significantly improved distribution was obtained when this dose of surfactant (100 mg/kg body weight) was diluted with normal saline to a concentration of 6.25 g/L. The consequence of the administration of this dose was an intratracheal fluid administration of 16.0 mL/kg body weight. The distribution was also nonhomogeneous after the administration of a small-volume (2.4 mL/kg body weight), low-concentration surfactant preparation (6.25 g/L). We conclude that a surfactant preparation with clinical application is distributed nonhomogeneously in the lungs after endotracheal administration. The distribution can be significantly improved by increasing the fluid volume in which the surfactant is suspended.

ACTIVATION OF THE PLASMA CLOTTING, FIBRINOLYTIC, AND KININ-KALLIKREIN SYSTEM IN PRETERM INFANTS WITH SEVERE IDIOPATHIC RESPIRATORY DISTRESS SYNDROME

ABSTRACT: We studied the activation pattern of clotting, fibrinolysis, and kinin-kallikrein during the first 5 d of life in 10 preterm infants with signs of severe idiopathic respiratory distress syndrome (IRDS) after birth (IRDS group) and in 12 healthy preterm infants (reference group). We found systemic activation of clotting, fibrinolysis, and kinin-kallikrein in the IRDS infants within 12 to 24 h of birth, represented by increased median thrombin-antithrombin III complex formation (90 ng/mL versus 10 ng/mL in the reference group, p < 0.05), increased mean tissue-type plasminogen activator plasma concentrations (11.8 ng/mL versus 3.5 ng/mL in the reference group, p < 0.05), and increased mean plasma kallikrein activity (182.6% versus 162.0% of maximal activated human plasma in the reference group, p < 0.05), respectively. Clotting activation was accompanied by a significant decrease of the platelet count. Clotting and fibrinolytic activity decreased in the IRDS group during the first 2 to 3 d of life. Kinin-kallikrein activation was accompanied by decreased plasma kallikrein inhibitor activity values and did not change throughout the study period. Plasma factor XII activity was not significantly increased in the IRDS infants during the first 2 d of life but did significantly increase thereafter. The cause of simultaneous activation of clotting, fibrinolysis, and kinin-kallikrein in our IRDS infants has not yet been clarified. However, this activation process may contribute to lung injury such as that described in the adult respiratory distress syndrome.

Disease severity is correlated with plasma clotting and fibrinolytic and kinin-kallikrein activity in neonatal respiratory distress syndrome

This study was undertaken to determine whether simultaneous activation of clotting, fibrinolysis, and kinin-kallikrein is associated with disease severity in preterm infants with neonatal respiratory distress syndrome (RDS), during the first 5 d of life. In the infants with severe RDS, we found activation of clotting, fibrinolysis, and kinin-kallikrein within 6-12 h of birth, indicated by increased thrombin-antithrombin III complex formation[22.5 ng/ml versus 1.4 ng/ml (median values) in the mild/moderate RDS infants, p < 0.001], increased tissue-type plasminogen activator plasma concentrations [5.1 ng/ml versus 2.6 ng/ml (median values) in the mild/moderate RDS infants, p < 0.01], and increased plasma kallikrein activity [198% versus 189% of maximal activated human plasma (median values) in the mild/moderate infants,p < 0.01], respectively. Thrombin generation, tissue-type plasminogen activator release, and kallikrein activity did not change significantly in the severe RDS group throughout the study. In these infants, kallikrein activity was accompanied by lower values of plasma kallikrein inhibitory activity. Activation of clotting, fibrinolysis, and kinin-kallikrein was accompanied with a transient decrease of the neutrophil count and a steady decrease of the platelet count in the severe RDS group. The studied parameters of clotting and fibrinolytic and kinin-kallikrein activation were significantly correlated with continuous measures of RDS severity. We, therefore, suggest that this activation process likely contributes to respiratory insufficiency in neonatal RDS.

Activation of Circulating Polymorphonuclear Leukocytes in Preterm Infants with Severe Idiopathic Respiratory Distress Syndrome

We have studied activation of circulating polymorphonuclear leukocytes(PMN) in plasma of preterm infants with severe idiopathic respiratory distress syndrome (IRDS group, n = 15) and without IRDS (reference group,n = 15) during the first 5 postnatal days. We have observed lower median PMN counts in the IRDS group than in the reference group from d 2 (1.4× 109/L versus 4.8 × 109/L in the reference group, p < 0.001) to d 4 to 6 (1.6 × 109/Lversus 4.0 × 109/L, p < 0.01). Lower PMN counts in the IRDS infants were accompanied by lower median plasma elastase-α1-proteinase inhibitor (PI) concentrations (53.6 ng/mLversus 128.0 ng/mL in the reference group on d 2, p < 0.05). Simultaneously, median elastase-α1-PI/PMN ratios of these infants were significantly higher (40.8 ng/106 PMN versus 21.8 ng/106 PMN on d 2, p < 0.05), indicating activation of circulating PMN. Activation of circulating PMN in the IRDS group is associated with platelet-activating factor (PAF) release and complement activation from within 6 to 12 h of birth but not with release of tumor necrosis factor-α. PAF release was represented by significantly reduced inhibiting capacity (58% of normal human plasma, p < 0.01) and complement activation by higher median plasma C3a des-Arg concentrations (1680 ng/mL versus 325 ng/mL in the reference group, p < 0.001). We conclude that circulating PMN are activated in preterm infants with severe IRDS, which might be caused by systemic PAF release and complement activation. This activation process may play a role in the pathogenesis of the IRDS by influx of activated PMN into the lungs.

Leakage of protein into lungs of preterm ventilated rabbits is correlated with activation of clotting, complement, and polymorphonuclear leukocytes in plasma

We investigated whether leakage of protein in lungs of preterm ventilated rabbits of 28- and 29-d gestational age is correlated with activation of clotting, complement, and polymorphonuclear leukocytes (PMN) in plasma. We found signs of systemic activation of clotting, complement, and PMN in ventilated 28-d gestational age rabbits, as indicated, respectively, by increased median plasma fibrin monomer concentrations (83 versus 40% of normal adult rabbit plasma in nonventilated 28-d gestational age rabbits,p < 0.01), decreased median plasma CH50 activity (112versus 122 U/L in nonventilated 28-d gestational age rabbits,p < 0.05), and increased median plasma β-glucuronidase concentrations (159 versus 97% of maximal activated adult rabbit plasma in nonventilated 28-d gestational age rabbits, p < 0.05). We did not find signs of systemic activation in the ventilated 29-d gestational age group. Higher median total protein concentrations in alveolar wash of the ventilated 28-d gestational age rabbits (2.7 versus 1.3 mg/mL in the nonventilated rabbits, p < 0.01) indicated protein leakage into the lungs, and this protein leakage was more pronounced in the lungs of ventilated 28-d gestational age rabbits than in those of ventilated 29-d gestational age rabbits (2.1 mg/mL, p < 0.01). The total protein concentration in the alveolar wash of all 28-d gestational age rabbits was correlated with the concentration of fibrin monomers (ρ = 0.51,p = 0.035) and β-glucuronidase (ρ = 0.61, p = 0.011), and the CH50 activity (ρ = -0.73, p = 0.002) in plasma. We conclude that leakage of protein in lungs of preterm ventilated rabbits of 28-d gestational age is correlated with activation of clotting, complement, and PMN in plasma. This activation process may contribute to lung injury by intravascular and intraalveolar deposition of fibrin and formation of proteinaceous edema.

Surfactant replacement therapy in surfactant-deficient rabbits: Early effects on lung function and biochemical aspects

Lung-surfactant-deficient rabbits (n = 6) requiring artificial ventilation were subjected to a weaning-off regimen following surfactant replacement therapy. Surfactant-deficient rabbits (n = 6) that did not receive surfactant but underwent the same procedure served as controls. All surfactant-treated rabbits survived (i.e., reestablished spontaneous air breathing) whereas all the control animals died. In the surfactant-treated animals lung function improved in such a way that during the weaning period PaCO2 did not increase and the level of PaO2 remained significantly higher than in the control animals. The static lung compliance and the stability and expansion indices in vitro were significantly higher in the surfactant-treated rabbits. The lamellar body fraction of the lungs of surfactant-treated animals contained a significantly higher amount of surfactant phospholipids than those of the control animals.It is concluded that the animal model used in this study is an excellent tool for testing early effects of different surfactant preparations.

Distribution of a Second Dose of Exogenous Surfactant in Rabbits with Severe Respiratory Failure

ABSTRACT: Newborn infants with respiratory distress who fail to respond to surfactant treatment receive a second dose of surfactant. The effect of this strategy on the distribution of surfactant to the lung is unknown. We therefore investigated the distribution of the first (100 mg/kg body weight) and second dose (50 mg/kg body weight) of surfactant (Alveofact) in lung-lavaged rabbits (n= 6). We used 141Ce- and 103Rn-labeled microspheres that were mixed with the first and second dose of surfactant, respectively. Arterial Po2 increased from 5.7 ± 1.1 to 10.6 ± 2.0 kPa (p< 0.05) (mean ± SD) after the first and from 20.1 ± 3.8 to 30.1 ± 2.5 kPa (p< 0.05) after the second dose. Thereafter the rabbits were killed, and the lungs were cut into 200 pieces. The radioactivity of Ce and Rn microspheres was measured and distribution histograms were obtained. Histograms of the first, second, and the total dose of surfactant showed similar nonuniform distribution. Correlation coefficients of the Ce and Rn radioactivity in the different lung lobes widely ranged per lung lobe per rabbit. In addition, the percentage of the number of lung pieces that received an amount of surfactant that was less than the calculated endogenous surfactant pool decreased from 12.5 ± 3.2% to 8.5 ± 3.0% (p< 0.05) after the first and second dose, respectively. This indicates that the second dose was directed both to areas that initially received surfactant and to areas that were still surfactant-deficient. The surfactant-deficient areas were aerated after this second dose, resulting in a further rise in Po2. We conclude that a second dose of surfactant does not lead to homogeneous distribution of surfactant but does result in a significant rise in Po2 that is probably due to increased aeration after the second dose of surfactant, which may be partially related to an additional recruitment of alveoli after the second dose of surfactant.

COMPLEMENT ACTIVATION IN THE IDIOPATHIC RESPIRATORY-DISTRESS SYNDROME (IRDS)

Complement activation in preterm infants with IRDS may be partly caused by platelet-activating factor (PAF). PAF and complement can activate leukocytes. We measured in plasma complement activation (C3a), PAF-inhibitory capacity (PAF-IC;low PAF-IC indicates PAF release), and leukocyte activation (elastase-proteinase inhibitor complex (E-PI) and tumor necrosis factor (TNF-α)) together with the leukocyte count on day 1, 3 and 5 in preterm infants with IRDS and in healthy 1-day-old preterm infants (reference).Conclusion: The leukocyte count and plasma concentrations of E-PI and TNF-α are reduced in the IRDS infants. This may represent activation and sequestration of leukocytes in the lungs due to PAF and activated complement.

SHORTER GESTATIONAL-AGE IS ASSOCIATED WITH SYSTEMIC ACTIVATION OF COMPLEMENT, LEUKOCYTES AND CLOTTING IN PRETERM VENTILATED RABBITS

Activation of plasma proteins and cells in the idiopathic respiratory distress syndrome may be influenced by gestational age. We measured in plasma complement hemolytic activity (CH50), and activation of leukocytes (beta-glucuronidase, BG) and clotting (fibrin monomers, FM) in preterm ventilated rabbits of 28d and 29d of gestational age. Dynamic lung compliance (Cdyn) and ventilatory efficiency index (VEI) served as lung function parameters.Conclusion: Decreased Cdyn and VEI in preterm ventilated rabbits of shorter gestational age are associated with increased systemic activation of complement, leukocytes, and clotting. This systemic activation process may contribute to further lung injury.

EXOGENOUS SURFACTANT PHOSPHOLIPIDS STIMULATE ENDOGENOUS SATURATED PHOSPHATIDYCHOLINE SYNTHESIS

Surfactant treatments result in increased synthesis and secretion of endogenous saturated phosphatidylcholine (Sat.PC) in adult rabbits. To elucidate the contribution to these effects of surfactant associated proteins and surfactant phospholipids in surfactant preparations we studied a mixture (MPCG) of dipalmitoylphosphatidyl choline and phosphatidyl glycerol (9:1), a lipid extract of natural surfactant (LENS), a phospholipid fraction of natural surfactant (PLNS) and a reconstituted natural surfactant (RNS). These surfactants were injected into the left mainstem bronchus after induction of oxygen resorption atelectasis of the left lower lobe of adult rabbits. Surfactant metabolism was studied by injecting 32P-orthophosphate 30 min and 3H palmitic acid i.v. 6 h after the injections, followed by sacrifice at 10 h after the injections with subsequent alveolar wash and processing of the right lung and left lower lobe separately. For the 32P incorporation into Sat.PC the ratios of the left lower lobe to right lung were: 0.87±0.15 (MPCG), 0.74±0.14 (LENS), 0.90±0.11 (PLNS), 0.86±0.14 (RNS) significantly higher than unmanipulated controls: 0.47±0.05 (mean±SD) (P<0.05). LENS tended to decrease the secretion of Sat.PC. These results suggest that Sat.PC synthesis is stimulated aspecificially by phospholipids from exogenous surfactant.