Lavage administration of dilute recombinant surfactant in acute lung injury in piglets

Persurf, a new method to improve surfactant delivery: a study in surfactant depleted rats

PURPOSE

Exogenous surfactant is not very effective in adults with ARDS, since surfactant does not reach atelectatic alveoli. Perfluorocarbons (PFC) can recruit atelectatic areas but do not replace impaired endogenous surfactant. A surfactant-PFC-mixture could combine benefits of both therapies. The aim of the proof-of-principal-study was to produce a PFC-in-surfactant emulsion (Persurf) and to test in surfactant depleted Wistar rats whether Persurf achieves I.) a more homogenous pulmonary distribution and II.) a more homogenous recruitment of alveoli when compared with surfactant or PFC alone.

METHODS

Three different PFC were mixed with surfactant and phospholipid concentration in the emulsion was measured. After surfactant depletion, animals either received 30 ml/kg of PF5080, 100 mg/kg of stained (green dye) Curosurf™ or 30 ml/kg of Persurf. Lungs were fixated after 1 hour of ventilation and alveolar aeration and surfactant distribution was estimated by a stereological approach.

RESULTS

Persurf contained 3 mg/ml phospholipids and was stable for more than 48 hours. Persurf-administration improved oxygenation. Histological evaluation revealed a more homogenous surfactant distribution and alveolar inflation when compared with surfactant treated animals.

CONCLUSIONS

In surfactant depleted rats administration of PFC-in-surfactant emulsion leads to a more homogenous distribution and aeration of the lung than surfactant alone.

Effect of surfactant concentration, compression ratio and compression rate on the surface activity and dynamic properties of a lung surfactant

This paper reports dynamic surface tension experiments of a lung surfactant preparation, BLES, for a wide range of concentrations, compression ratios and compression rates. These experiments were performed using Axisymmetric Drop Shape Analysis-Constrained Sessile Drop (ADSA-CSD). The main purpose of the paper is to interpret the results in terms of physical parameters using the recently developed Compression-Relaxation Model (CRM). In the past, only the minimum surface tension was used generally for the characterization of lung surfactant films; however, this minimum value is not a physical parameter and depends on the compression protocol. CRM is based on the assumption that the dynamic surface tension response is governed by surface elasticities, adsorption and desorption of components of the lung surfactant. The ability of CRM to fit the surface tension response closely for a wide variety of parameters (compression ratio, compression rate and surfactant concentration) and produce sensible values for the elastic and kinetic parameters supports the validity of CRM.

Selective medicated (saline + natural surfactant) bronchoalveolar lavage in unilateral lung contusion. A clinical randomized controlled trial

OBJECTIVE

Open lung and low tidal volume ventilation appear to be a promising ventilation for chest trauma as it can reduce ARDS and improve outcome. Local therapy (e.g. BAL) can be synergic to remove from the lung the debris, mitigate inflammatory cascade and avoid damage spreading to not compromised lung areas.

MATERIALS AND METHODS

44 pulmonary contused patients were randomized to receive broncho-suction and volume controlled low tidal volume ventilation-VCLTVV (Control Group) or the same ventilation plus medicated (saline + surfactant) BAL (Treatment Group). Tidal volume <10 ml/kg, PEEP of 10-12 cm H(2)O and PaO(2) 60-100 mm Hg and PaCO(2) 35-45 mm Hg were used in both groups. BAL was performed using a fiberscope. 4 boluses of 25 ml saline with 2.4 mg/ml of surfactant were introduced into each contused lobe in which, subsequently, 240 mg of surfactant was instilled.

RESULTS

All patients survived. In the Control Group 18 patients developed pneumonia, 5 ARDS and days of intubation were 11.50 (3.83) compared to 5.05 (1.21) of Treatment Group in which OI and PaO(2)/FiO(2) significantly improved from 36 h.

CONCLUSIONS

VCLTVV alone was not able to prevent ARDS and infection in the Control Group as the reduction of intubation. In the Treatment Group, VCLTVV and medicated BAL facilitated the removal of degradated lung material and recruited the contused lung regions, enabling the healing of the lung pathology.

[Value of surfactant replacement therapy in the treatment of acute respiratory distress syndrome]

Acute respiratory distress syndrome (ARDS) is a common, devastating clinical problem arising from a number of conditions, such as pneumonia, trauma or sepsis. Because of its significant mortality and morbidity, ARDS has been in the focus of extensive experimental and clinical research. Since there is little doubt that alterations of the surfactant system contribute to lung dysfunction and the onset of ARDS, several clinical studies examined the therapeutic safety and efficacy of a surfactant replacement therapy. Clinical experience with exogenous surfactant has proven inconsistent as a therapeutic modality for adult patients with ARDS. This is mainly due to a number of confounding factors, e.g. severity of injury at the time of treatment, dosing regimes and delivery methods used in different trials. However, current data suggest that patients with direct ARDS (e.g. pneumonia, aspiration) could benefit from surfactant replacement therapy rather than patients with indirect ARDS (e.g. sepsis, trauma). Although surfactant replacement therapy has been shown to significantly reduce mortality in neonates with ARDS, there has been no large randomised clinical trial showing that exogenous surfactant improves outcome in adults with respiratory failure. Therefore, surfactant therapy cannot be recommended for routine clinical use in adult patients and has to be considered as a last resort treatment.

Expanded use of surfactant therapy in newborns

Although there is no doubt that administration of exogenous surfactant to very preterm babies who have respiratory distress syndrome is safe and efficacious, surfactant inactivation or deficiency plays a role in the pathophysiology of other pulmonary disorders affecting newborn infants. Preliminary data suggest that there may be a role for surfactant administration to babies who have meconium aspiration syndrome, pneumonia, and possibly bronchopulmonary dysplasia. Further investigation is necessary but seems warranted.

Lung Volume Recruitment after Surfactant Administration Modifies Spatial Distribution of Ventilation

RATIONALE

Although surfactant replacement therapy is an established treatment in infant respiratory distress syndrome, the optimum strategy for ventilatory management before, during, and after surfactant instillation remains to be elucidated.

OBJECTIVES

To determine the effects of surfactant and lung volume recruitment on the distribution of regional lung ventilation.

METHODS

Acute lung injury was induced in 16 newborn piglets by endotracheal lavage. Optimum positive end-expiratory pressure was identified after lung recruitment and surfactant was administered either at this pressure in the "open" lung or after disconnection of the endotracheal tube in the "closed" lung. An additional recruitment maneuver with subsequent optimum end-expiratory pressure finding was executed in eight animals; in the remaining eight animals, end-expiratory pressure was set at the same level as before surfactant without further recruitment. ("Open" and "closed" lung surfactant administration was evenly distributed in the groups.) Regional ventilation was assessed by electrical impedance tomography.

MEASUREMENTS AND MAIN RESULTS

Impedance tomography data, airway pressure, flow, and arterial blood gases were acquired during baseline conditions, after induction of lung injury, after the first lung recruitment, and before as well as 10 and 60 min after surfactant administration. Significant shift in ventilation toward the dependent lung regions and less asymmetry in the right-to-left lung ventilation distribution occurred in the postsurfactant period when an additional recruitment maneuver was performed. Surfactant instillation in an "open" versus "closed" lung did not influence ventilation distribution in a major way.

CONCLUSIONS

The spatial distribution of ventilation in the lavaged lung is modified by a recruitment maneuver performed after surfactant administration.

Bilateral lavage with diluted surfactant improves lung function after unilateral lung contusion in pigs*

OBJECTIVE

This study evaluates the effects of bronchoalveolar lavage with diluted surfactant on unilateral lung contusion-induced lung dysfunction.

DESIGN

Randomized prospective animal study.

SETTING

An animal laboratory.

SUBJECTS

Twenty adult pigs, weighing 25-35 kg.

INTERVENTIONS

Animals were randomly assigned to controls and surfactant treatment. Bilateral lavage with surfactant treatment began 30 mins after unilateral lung contusion. Then 25 mg/kg of body weight diluted Curosurf (5 mg/mL) was applied in a volume of 5 mL/kg of body weight. Observation time was 8 hrs postinjury.

MEASUREMENTS AND MAIN RESULTS

The Pao2/Fio2 ratio fell from 500 to 250 and then recovered gradually in controls and surfactant-treated pigs. After another 4 hrs, the Pao2/Fio2 ratio deteriorated again in controls, but not in surfactant-treated animals. Total compliance fell by 50% after injury but was completely restored by surfactant treatment. Lung contusion increased the median number of neutrophils in bronchoalveolar lavage fluid from 2% to 30% of total cells and peaked >60% at 480 mins in the contused lungs of control pigs. Surfactant-treated pigs had 40% neutrophils at 480 mins without reaching significant difference to controls. The leukocyte neutral proteinase inhibitor increased to 500 ng/mL at 30 mins postinjury in the contused lungs and increased to 2000 ng/mL after surfactant treatment.

CONCLUSIONS

Bilateral bronchoalveolar lavage with diluted surfactant can effectively improve lung function after experimental unilateral lung contusion in pigs.

Surfactant lavage with lidocaine improves pulmonary function in piglets after HCl-induced acute lung injury

Acute respiratory distress syndrome (ARDS) is associated with significant morbidity and mortality. The pathophysiology of ARDS includes abnormalities of surfactant function as well as pulmonary inflammation. Immunomodulating drugs, like Lidocaine, have shown some success in decreasing inflammation in ARDS. We attempted to combine surfactant lavage's ability to reverse the surfactant dysfunction, while acting as a vehicle to deliver Lidocaine. Gravity-driven surfactant (Infasurf) lavage (35 ml/kg) was administered alone or mixed with Lidocaine after severe HCl acid injury (0.3 N; 3 cc/kg) in neonatal piglets. Treatment groups included: control (C) ( n = 5), surfactant lavage (SL) (35 ml/kg-diluted Infasurf) ( n = 7) and SL mixed with Lidocaine (SL+L) ( n = 7). About 26-27% of the lavage was retained (phospholipid 73-74 mg/kg; Lidocaine 1.8 mg/kg). Oxygenation progressively increased in the SL and SL+L groups over the 4-hour period (at 240 min: C = 99 +/- 14; SL = 154 +/- 39; SL+L = 230 +/- 40 mmHg) ( p < 0.05). PaCO(2) increased in all groups from 43 +/- 0.3 to 55 +/- 0.7 mmHg. Only SL+L showed a reduction in PaCO(2) (at 240 min: C = 54 +/- 4; SL = 53 +/- 7; SL+L = 49 +/- 2 mmHg) ( p < 0.05). Finally, SL and SL + L had superior characteristics during the quasi-static pressure volume (PV) procedure as compared to Control ( p < 0.05). In our HCl ALI model, SL improved oxygenation and quasi-static lung compliance over C. The pulmonary function effects of SL were further enhanced by the addition of Lidocaine to the surfactant suspension. Combining therapeutic agents with surfactant lavage may be an effective strategy in ALI.

Exogenous surfactant therapy: newer developments

There are numerous pulmonary conditions in which qualitative or quantitative anomalies of the surfactant system have been demonstrated. In premature newborns with immature lungs, a functional deficit in surfactant is the main physiopathologic mechanism of the neonatal respiratory distress syndrome (RDS). Since the landmark pilot study of Fujiwara, published more than 20 years ago, the efficacy of exogenous surfactant for the treatment of neonatal RDS has been established by numerous controlled studies and meta-analyses. Promising results have also been reported in infants suffering from other lung disorders in which endogenous surfactant function is compromised. Enlightened by a growing insight into both the structure and function of the different surfactant components, a new generation of synthetic surfactants has been developed. Various complementary approaches have confirmed the fundamental role of the two hydrophobic proteins, SP-B and SP-C, in the surfactant system, thus opening the way to the design of analogues, either by chemical synthesis or expression in a prokaryotic system. These peptide-containing synthetic surfactant preparations are presently undergoing clinical trials, and may eventually replace the animal-derived surfactants currently used for the treatment of RDS.

Pulmonary surfactant for neonatal respiratory disorders

Surfactant therapy has revolutionized neonatal care and is used routinely for preterm infants with respiratory distress syndrome. Recent investigation has further elucidated the function of surfactant-associated proteins and their contribution toward surfactant and lung immune defense functions. As the field of neonatology moves away from intubation and mechanical ventilation of preterm infants at birth toward more aggressive use of nasal continuous positive airway pressure, the optimal timing of exogenous surfactant therapy remains unclear. Evidence suggests that preterm neonates with bronchopulmonary dysplasia and prolonged mechanical ventilation also experience surfactant dysfunction; however, exogenous surfactant therapy beyond the first week of life has not been well studied. Surfactant replacement therapy has been studied for use in other respiratory disorders, including meconium aspiration syndrome and pneumonia. Commercial surfactant preparations currently available are not optimal, given the variability of surfactant protein content and their susceptibility to inhibition. Further progress in the treatment of neonatal respiratory disorders may include the development of "designer" surfactant preparations.

A multicenter, randomized, controlled trial comparing Surfaxin (Lucinactant) lavage with standard care for treatment of meconium aspiration syndrome

OBJECTIVE

Infants with meconium aspiration syndrome (MAS) have marked surfactant dysfunction. Airways and alveoli of affected neonates contain meconium, inflammatory cells, inflammatory mediators, edema fluid, protein, and other debris. The objective of this study was to compare treatment with bronchoalveolar lavage using dilute Surfaxin with standard therapy in a population of newborn infants with MAS.

METHODS

Inclusion criteria were 1) gestational age > or =35 weeks, 2) enrollment within 72 hours of birth, 3) diagnosis of MAS, 4) need for mechanical ventilation, and 5) an oxygenation index > or =8 and < or =25. Subjects were randomized to either lavage with Surfaxin or standard care (2:1 proportion). In lavaged infants, a volume of 8 mL/kg dilute Surfaxin (2.5 mg/mL) was instilled into each lung over approximately 20 seconds followed by suctioning after 5 ventilator breaths. The procedure was repeated twice. The third and final lavage was with a more concentrated solution (10 mg/mL) of Surfaxin.

RESULTS

Twenty-two infants were enrolled (15 Surfaxin and 7 control). Demographic characteristics were similar. There were trends (not significant) for Surfaxin-lavaged infants to be weaned from mechanical ventilation earlier (mean of 6.3 vs 9.9 days, respectively), as well as to have a more rapid decline in their oxygenation indexes compared with control infants, the latter difference persisting for the 96-hour-long study period. The therapy was safe and generally well tolerated by the infants.

CONCLUSIONS

Dilute Surfaxin lavage seems to be a safe and potentially effective therapy in the treatment of MAS. Data from this investigation support future prospective, controlled clinical trials of bronchoalveolar lavage with Surfaxin in neonates with MAS.

Mouse models for disorders of mitochondrial fatty acid beta-oxidation

Mitochondrial beta-oxidation of fatty acids is vital for energy production in periods of fasting and other metabolic stress. Human patients have been identified with inherited disorders of mitochondrial beta-oxidation of fatty acids with enzyme deficiencies identified at many of the steps in this pathway. Although these patients exhibit a range of disease processes, Reye-like illness (hypoketotic-hypoglycemia, hyperammonemia and fatty liver) and cardiomyopathy are common findings. There have been several mouse models developed to aid in the study of these disease conditions. The characterized mouse models include inherited deficiencies of very long-chain acyl-CoA dehydrogenase, long-chain acyl-CoA dehydrogenase, short-chain acyl-CoA dehydrogenase, mitochondrial trifunctional protein-alpha, and medium-/short-chain hydroxyacyl-CoA dehydrogenase. Mouse mutants developed, but presently incompletely characterized as models, include carnitine palmitoyltransferase-1a and medium-chain acyl-CoA dehydrogenase deficiencies. In general, the mouse models of disorders of mitochondrial fatty acid beta-oxidation have shown clinical signs that include Reye-like syndrome and cardiomyopathy, and many are cold intolerant. It is expected that these mouse models will provide vital contributions in understanding the mechanisms of disease pathogenesis of fatty acid oxidation disorders and the development of appropriate treatments and supportive care.

Surfactant therapy in infants and children: three years experience in a pediatric intensive care unit

Despite the established success of surfactant application in neonates, the use of surfactant in older children is still a matter of discussion. We hypothesized that surfactant application in children with acute respiratory distress syndrome (ARDS) secondary to a pulmonary or systemic disease or after cardiac surgery improves pulmonary function. We also asked whether repeated treatment could further improve pulmonary function. To answer these questions, we measured oxygenation index (OI) and hypoxemia score after the first and after a second application of surfactant (50-100 mg/kg body wt) at least 24 h later. We enrolled 19 children (older than 4 weeks) for a retrospective chart review study, and six of them underwent cardiac surgery. Demographic data were extracted. OI and hypoxemia score were estimated before and 2 and 24 h after surfactant application. Lung injury score was calculated before and 24 h after surfactant application. Outcome measures included survival, duration of mechanical ventilation, and pediatric ICU and hospital stay. The median patient age was 9.0 (quarter percentile 3.7/25) months. The median weight was 8.4 (4.1/11.5) kg. The median lung injury score before the first surfactant application was 2.3 (2.3/2.6). Hospital duration and pediatric ICU stay for all patients was 31.0 (20.0/49.5) days and 27.0 (15.5/32.5) days, respectively. The duration of mechanical ventilation was 24.0 (18.5/31.0) days. The overall mortality was 53%. Twenty-four hours after the first surfactant application, pulmonary function significantly improved. The median OI was 14 (5.5/26) before and 7 (4.5/14.5) 24 h after surfactant application (P= 0.027). The hypoxemia score was 91.7 (69.9/154.2) before and 148.4 (99.2/167.6) 24 h after surfactant application (P = 0.0026). Seven children received a second application, which did not further improve pulmonary function. The lung injury score was not influenced by either surfactant application. We conclude that a single surfactant application improves pulmonary function in children with ARDS. A second application of surfactant showed no further benefit. Outcome was not affected in our study population.

Expanded uses of surfactant therapy

There are few therapies for which the cumulative evidence of benefit is as much as that for surfactant therapy for RDS in premature infants. Exogenous surfactant therapy does seem to be beneficial for a number of non-RDS disorders. Although there are some trials supporting its use in MAS and ALI-ARDS, there are only a few small prospective, randomized, controlled trials supporting surfactant use in non-RDS disorders. Use of surfactant therapy for any disorder other than RDS must be considered "off the shelf" and experimental. Much work remains to be done to address the role of surfactant therapy in the myriad disorders discussed. Of import for each of the disorders is addressing the optimum type of surfactant to use, and the appropriate dose, method of delivery, and duration of treatment regimens.

The present status of exogenous surfactant for the newborn

This year is the 20th anniversary of the first successful trial of exogenous surfactant for respiratory distress syndrome in the newborn and it is perhaps a good time to review recent advances in basic science and clinical practice as they relate to surfactant therapy.