Comparison of two strategies for surfactant prophylaxis in very premature infants: a multicenter randomized trial

Less Invasive Surfactant Administration: A Viewpoint

The standard of care in treating respiratory distress syndrome in preterm infants is respiratory support with nasal continuous positive airway pressure or a combination of continuous positive airway pressure and exogenous surfactant replacement. Endotracheal intubation, the conventional method for surfactant administration, is an invasive procedure associated with procedural and mechanical ventilation complications. The INSURE (intubation, surfactant administration, and extubation soon after) technique is an accepted method aimed at reducing the short-term complications and long-term morbidities related to mechanical ventilation but does not eliminate risks associated with endotracheal intubation and mechanical ventilation. Alternative methods of surfactant delivery that can overcome the problems associated with the INSURE technique are surfactant through a laryngeal mask, surfactant through a thin intratracheal catheter, and aerosolized surfactant delivered using nebulizers. The three alternative methods of surfactant delivery studied in the last two decades have advantages and limitations. More than a dozen randomized controlled trials have aimed to study the benefits of the three alternative techniques of surfactant delivery compared with INSURE as the control arm, with promising results in terms of reduction in mortality, need for mechanical ventilation, and bronchopulmonary dysplasia. The need to find a less invasive surfactant administration technique is a clinically relevant problem. Before broader adoption in routine clinical practice, the most beneficial technique among the three alternative strategies should be identified. This review aims to summarize the current evidence for using the three alternative techniques of surfactant administration in neonates, compare the three techniques, highlight the knowledge gaps, and suggest future directions. KEY POINTS: · The need to find a less invasive alternative method of surfactant delivery is a clinically relevant problem.. · Clinical trials that have studied alternative surfactant delivery methods have shown promising results but are inconclusive for broader adoption into clinical practice.. · Future studies should explore novel clinical trial methodologies and select clinically significant long term outcomes for comparison..

Surfactant replacement therapy in extremely low gestational age newborns

There is a growing body of evidence over the last years suggesting continuous positive airway pressure (CPAP) ventilation being the first choice of ventilatory support in newborns with extremely low gestational age, and early rescue surfactant treatment being as effective as prophylactic therapy. The Intubation Surfactant Extubation procedure is discussed as an alternative procedure that may have the potential to combine the positive effects of surfactant and early CPAP. A further mode of surfactant administration, administration via a thin endotracheal catheter during spontaneous breathing with CPAP, has recently come into clinical use. This less invasive surfactant administration technique shows some short-term benefits but still cannot be recommended for general use in this vulnerable population. Long-term follow-up studies are needed to allow new recommendations on surfactant therapy in this high-risk population.

Acute Neonatal Respiratory Failure

Acute respiratory failure requiring assisted ventilation is one of the most common reasons for admission to the neonatal intensive care unit. Respiratory failure is the inability to maintain either normal delivery of oxygen to the tissues or normal removal of carbon dioxide from the tissues. It occurs when there is an imbalance between the respiratory workload and ventilatory strength and endurance. Definitions are somewhat arbitrary but suggested laboratory criteria for respiratory failure include two or more of the following: PaCO₂ > 60 mmHg, PaO₂ < 50 mmHg or O₂ saturation <80 % with an FiO₂ of 1.0 and pH < 7.25 (Wen et al. 2004).

Surfactant

Exogenous pulmonary surfactant, widely used in neonatal care, is one of the best-studied treatments in neonatology, and its introduction in the 1990s led to a significant improvement in neonatal outcomes in preterm infants, including a decrease in mortality. This chapter provides an overview of surfactant composition and function in health and disease and summarizes the evidence for its clinical use.

Surfactant replacement therapy for preterm and term neonates with respiratory distress

Respiratory failure secondary to surfactant deficiency is a major cause of morbidity and mortality in preterm infants. Surfactant therapy substantially reduces mortality and respiratory morbidity for this population. Secondary surfactant deficiency also contributes to acute respiratory morbidity in late-preterm and term neonates with meconium aspiration syndrome, pneumonia/sepsis, and perhaps pulmonary hemorrhage; surfactant replacement may be beneficial for these infants. This statement summarizes the evidence regarding indications, administration, formulations, and outcomes for surfactant-replacement therapy. The clinical strategy of intubation, surfactant administration, and extubation to continuous positive airway pressure and the effect of continuous positive airway pressure on outcomes and surfactant use in preterm infants are also reviewed.

Current Issues and Challenges in the Use of Aerosolized Surfactant for Respiratory Distress Syndrome in the Newborns

BACKGROUND: Surfactant replacement therapy is a recognized treatment for respiratory distress syndrome (RDS) in the newborns. Over the past 30 years, human and animal trials have been performed regarding administration of aerosolized surfactant to the injured lung, however the result has been unsatisfactory when compared with instilled surfactant delivery via endotracheal tube (ETT). This review aims to investigate the current issues, challenges and future recommendation of aerosolized surfactant therapy.CONTENT: Five randomized clinical trials in humans and 13 animal trials met the inclusion criteria and were reviewed. Most animal trials agree that this method of treatment is feasible. However, human trials presented conflicting results, and generally showed it to be ineffective. When compared with surfactant delivery via ETT, aerosolized surfactant is less effective in improving respiratory function.SUMMARY: The current data from human trials does not support the implementation of aerosolized surfactant therapy to treat newborns with RDS. Further research is necessary to improve nebulization, delivery, distribution and deposition in the lung, to investigate aerosolized surfactant delivery via ETT and to determine the appropriate dose.KEYWORDS: surfactant, aerosol, prematurity, respiratory distress syndrome

Positive end-expiratory pressure and surfactant decrease lung injury during initiation of ventilation in fetal sheep

The initiation of ventilation in preterm, surfactant-deficient sheep without positive end-expiratory pressure (PEEP) causes airway injury and lung inflammation. We hypothesized that PEEP and surfactant treatment would decrease the lung injury from initiation of ventilation with high tidal volumes. Fetal sheep at 128-day gestational age were randomized to ventilation with: 1) no PEEP, no surfactant; 2) 8-cmH(2)O PEEP, no surfactant; 3) no PEEP + surfactant; 4) 8-cmH(2)O PEEP + surfactant; or 5) control (2-cmH(2)O continuous positive airway pressure) (n = 6-7/group). After maternal anesthesia and hysterotomy, the head and chest were exteriorized, and the fetus was intubated. While maintaining placental circulation, the fetus was ventilated for 15 min with a tidal volume escalating to 15 ml/kg using heated, humidified, 100% nitrogen. The fetus then was returned to the uterus, and tissue was collected after 30 min for evaluation of early markers of lung injury. Lambs receiving both surfactant and PEEP had increased dynamic compliance, increased static lung volumes, and decreased total protein and heat shock proteins 70 and 60 in bronchoalveolar lavage fluid compared with other groups. Ventilation, independent of PEEP or surfactant, increased mRNA expression of acute phase response genes and proinflammatory cytokine mRNA in the lung tissue compared with controls. PEEP decreased mRNA for cytokines (2-fold) compared with groups receiving no PEEP. Surfactant administration further decreased some cytokine mRNAs and changed the distribution of early growth response protein-1 expression. The use of PEEP during initiation of ventilation at birth decreased early mediators of lung injury. Surfactant administration changed the distribution of injury and had a moderate additive protective effect.

Gently caring: supporting the first few critical hours of life for the extremely low birth weight infant

Caring for the extremely low birth weight infant in the first days of life is complex and challenging, yet rewarding. It is the experienced health care provider who will be best prepared to meet the needs of these fragile infants and their concerned/frightened parents. Understanding how to minimize stress and support body functions will enable us to better care for these infants in the first few days of life. We should strive to partner with parents, even in the resuscitative and stabilization phases of care, particularly when an infant may not survive. Nursing plays an essential role in providing this minute-to-minute support. It is not always what we do, but how we do it, that may matter most.

Respiratory strategies for preterm infants at birth

Neonatologists treating extremely premature infants in the delivery room are faced with many dilemmas, not least how best to support their breathing. A balance must be struck between helping those infants who need it and not applying potentially harmful treatments to infants who might not need them. Crucial to this process is being able to identify infants who might benefit.

Surfactant-replacement therapy for respiratory distress in the preterm and term neonate

Respiratory failure secondary to surfactant deficiency is a major cause of morbidity and mortality in preterm infants. Surfactant therapy substantially reduces mortality and respiratory morbidity for this population. Secondary surfactant deficiency also contributes to acute respiratory morbidity in late-preterm and term neonates with meconium aspiration syndrome, pneumonia/sepsis, and perhaps pulmonary hemorrhage; surfactant replacement may be beneficial for these infants. This statement summarizes indications, administration, formulations, and outcomes for surfactant-replacement therapy. The impact of antenatal steroids and continuous positive airway pressure on outcomes and surfactant use in preterm infants is reviewed. Because respiratory insufficiency may be a component of multiorgan dysfunction, preterm and term infants receiving surfactant-replacement therapy should be managed in facilities with technical and clinical expertise to administer surfactant and provide multisystem support.

Brief, large tidal volume ventilation initiates lung injury and a systemic response in fetal sheep

RATIONALE

Premature infants are exposed to potentially injurious ventilation in the delivery room. Assessments of lung injury are confounded by effects of subsequent ventilatory support.

OBJECTIVES

To evaluate the injury response to a brief period of large tidal volume (Vt) ventilation, simulating neonatal resuscitation in preterm neonates.

METHODS

Preterm lambs (129 d gestation; term is150 d) were ventilated (Vt = 15 ml/kg, no positive end-expiratory pressure) for 15 minutes to simulate delivery room resuscitation, either with the placental circulation intact (fetal resuscitation [ FR]) or after delivery (neonatal resuscitation [NR]). After the initial 15 minutes, lambs received surfactant and were maintained with either ventilatory support (FR-VS and NR-VS) or placental support (FR-PS) for 2 hours, 45 minutes. A control group received no resuscitation and was maintained with placental support. Samples of bronchoalveolar lavage fluid, lung, and liver were analyzed.

MEASUREMENTS AND MAIN RESULTS

Inflammatory cells and protein in bronchoalveolar lavage fluid, heat shock protein-70 immunostaining, IL-1beta, IL-6, IL-8, monocyte chemotactic protein-1, serum amyloid A (SAA)-3, Toll-like receptor (TLR)-2, and TLR4 mRNA in the lungs were increased in the FR-PS group compared with control animals. There were further elevations in neutrophils, IL-6, and IL-8 mRNA in the FR-VS and NR-VS groups compared with FR-PS. SAA3, TLR2, and TLR4 mRNA increased in the liver in all resuscitation groups relative to control animals.

CONCLUSIONS

Ventilation for 15 minutes with a Vt of 15 ml/kg initiates an injurious process in the preterm lung and a hepatic acute-phase response. Subsequent ventilatory support causes further increases in some injury indicators.

Selective surfactant prophylaxis in preterm infants born at < or =31 weeks' gestation using the stable microbubble test in gastric aspirates

OBJECTIVE

To evaluate the stable microbubble test (SMT) ability to select candidates for surfactant prophylaxis for respiratory distress syndrome (RDS).

STUDY DESIGN

We followed patients treated according to a new routine for surfactant prophylaxis based on the SMT to determine timing of the initial dose of surfactant, proportion of infants using surfactant, and the predictive value of the SMT. Gastric secretions were collected after birth. Newborns with < 25 microbubbles (MB)/mm(2) received prophylactic surfactant. Surfactant was given only after confirmation of RDS (rescue therapy) to newborns with > or =25 MB/mm(2).

RESULTS

Fifty-four (55%) had a low MB count and received prophylactic surfactant. Three out of 44 infants with a high MB count required rescue therapy (negative predictive value 93%; CI:81.3-98.6%). The median interval and interquartile range between surfactant administration and birth in the prophylaxis group was 20 (17-27) minutes. Surfactant was used in 23 of 28 (82%) infants born at < 28 weeks of gestation and in 34 of 70 (49%) infants between 28 and 31 weeks.

CONCLUSIONS

The SMT may be useful to determine surfactant prophylaxis (< 30 min after birth). This approach may reduce costs and the number of unnecessary interventions.

Nitrous oxide analgesia for intubating preterm neonates: a pilot study

AIM

To evaluate the administration of an equimolar mixture of N2O and O2 for intratracheal intubation in preterm neonates with respiratory distress syndrome (RDS).

DESIGN

Prospective evaluation of N2O/O2 in premature neonates with RDS.

SETTING

Tertiary neonatal unit from March to August 2003.

PATIENTS

Twenty-six of 79 neonates admitted for RDS within 48 h of birth.

INTERVENTION

N2O/O2 was administered until muscle tone was suppressed. Surfactant was given intratracheally. Patients were extubated as soon as possible.

MAIN OUTCOME MEASURES

The time needed for N2O/O2 to suppress muscle tone, an evaluation of sedation/analgesia through movements of the limbs, and indicators of stress-related haemodynamic change, all recorded by an independent observer.

RESULTS

In the 26 patients, gestational age was 30.5 (25th, 75th percentile: 30, 32) wk and median body weight was 1540 (1220, 1900) g. Postnatal age at intubation was 2 (2, 3) h. N2O/O2 administration time was 8 (6, 10) min (range 4-15 min). Sedation/analgesia was complete in 77% of patients. No significant differences between pre-procedure and post-procedure values were found for heart rate (p=0.29) or mean arterial blood pressure (p=0.13) (paired Wilcoxon test). Time needed for intubation was 30 (20, 37) s (range 10-60 s). Side effects included transient agitation (3/26) and retching (2/26). Extubation occurred 5 (5, 10) min (range 2-15 min) after surfactant instillation. Apnoeas occurred in 3/26 patients within 2 h after extubation. Two patients required reintubation to repeat surfactant administration within 24 h after extubation.

CONCLUSION

N2O/O2 may be helpful for intubation in preterm neonates. Larger randomized, double-blind studies are needed for a thorough evaluation of effectiveness and safety.

Initial ventilation strategies during newborn resuscitation

Ventilation alone is usually effective in most neonatal resuscitation episodes. A review of the evidence underpinning recommendations for methods and devices for providing initial ventilation during newborn resuscitation was conducted. Self-inflating bags, flow-inflating (anesthesia) bags, and T-piece devices all may be used to provide effective ventilation after birth, with none clearly superior. Whichever method is used, ventilation is likely to be delivered more consistently if a pressure-monitoring device is incorporated. The best indication of successful ventilation is a prompt increase in heart rate. The role of positive end-expiratory pressure during resuscitation requires further research, particularly in preterm infants, in whom it may protect against lung injury.

Overview of surfactant replacement trials

Clinical trials have evaluated the overall efficacy of surfactant therapy, as well as the relative efficacy of different surfactant preparations, the optimal timing of administration and the optimal dosage. Surfactant therapy leads to significant clinical improvement in infants at risk for, or having, respiratory distress syndrome (RDS). Clinical trials that compared the effects of synthetic or animal-derived surfactant preparations to placebo or no therapy demonstrate that surfactant therapy lead to rapid improvement in oxygenation, decreased ventilator support, decreased risk of pneumothorax, and mortality. Earlier treatment, prophylactic treatment of infants at high risk of developing RDS, and selective re-treatment leads to improved clinical outcome as well. Currently available animal-derived surfactants are superior to non-protein-containing synthetic surfactants. Ongoing evaluation will determine if important differences in animal-derived products are noted. Future trials will evaluate third-generation surfactant products and further refine what constitutes optimal use of surfactant.

Pathophysiology of Neonatal Respiratory Distress Syndrome

Neonatal respiratory distress syndrome (RDS) remains one of the major causes of neonatal mortality and morbidity despite advances in perinatal care. The initial management of infants with RDS has almost become 'too routine' with little thought about the pathophysiological processes that lead to the disease and how the clinician can use the existing therapeutic interventions to optimize care. The transition from fetus to infant involves many complex adaptations at birth; the most important is the function of the lungs as a gas exchange organ. Preterm surfactant-deficient infants are less well equipped to deal with this transition. Optimum gas exchange is achieved through matching of ventilation and perfusion. In RDS, ventilation may be affected by homogeneity of the airways with atelectasis and over distension, as hyaline membranes block small airways. In turn this contributes to the inflammation that becomes bronchopulmonary dysplasia. Exogenous surfactant given early, particularly with positive end-expiratory pressure and, where necessary, gentle ventilation, would seem to be the optimum way to prevent atelectasis. How this can be achieved in neonates after surfactant therapy is explored through a review of the normal physiology of the newborn lung and how this is affected by RDS. The therapeutic interventions of resuscitation, exogenous surfactant, ventilation and inhaled nitric oxide are discussed in relation to their effects and what are currently the optimum ways to use these. It is hoped that with a better understanding of the normal physiology in the newborn lung, and the effects of both disease and interventions on that physiology, the practising clinician will have a greater appreciation of management of preterm infants with, or at risk of, RDS.

Delivery room continuous positive airway pressure/positive end-expiratory pressure in extremely low birth weight infants: a feasibility trial

OBJECTIVE

Although earlier studies have suggested that early continuous airway positive pressure (CPAP) may be beneficial in reducing ventilator dependence and subsequent chronic lung disease in the extremely low birth weight (ELBW) infant, the time of initiation of CPAP has varied, and there are no prospective studies of infants who have received CPAP or positive end-expiratory pressure (PEEP) from initial resuscitation in the delivery room (DR). Current practice for the ELBW infant includes early intubation and the administration of prophylactic surfactant, often in the DR. The feasibility of initiating CPAP in the DR and continuing this therapy without intubation for surfactant has never been determined prospectively in a population of ELBW infants. This study was designed to determine the feasibility of randomizing ELBW infants of <28 weeks' gestation to CPAP/PEEP or no CPAP/PEEP during resuscitation immediately after delivery, avoiding routine DR intubation for surfactant administration, initiating CPAP on neonatal intensive care unit (NICU) admission, and assessing compliance with subsequent intubation criteria.

METHODS

Infants who were of <28 weeks' gestation, who were born in 5 National Institute of Child Health and Human Development Neonatal Research Network NICUs from July 2002 to January 2003, and for whom a decision had been made to provide full treatment after birth were randomized to receive either CPAP/PEEP or not using a neonatal T-piece resuscitator (NeoPuff). Infants would not be intubated for the sole purpose of surfactant administration in the DR. After admission to the NICU, all nonintubated infants were placed on CPAP and were to be intubated for surfactant administration only after meeting specific criteria: a fraction of inspired oxygen of >0.3 with an oxygen saturation by pulse oximeter of <90% and/or an arterial oxygen pressure of <45 mm Hg, an arterial partial pressure of carbon dioxide of >55 mm Hg, or apnea requiring bag and mask ventilation.

RESULTS

A total of 104 infants were enrolled over a 6-month period: 55 CPAP and 49 control infants. No infant was intubated in the DR for the exclusive purpose of surfactant administration. Forty-seven infants were intubated for resuscitation in the DR: 27 of 55 CPAP infants and 20 of 49 control infants. Only 4 of the 43 infants who had a birth weight of <700 g and 3 of the 37 infants of <25 weeks' gestation were resuscitated successfully without positive pressure ventilation, and no difference was observed between the treatment groups. All infants of 23 weeks' gestation required intubation in the DR, irrespective of treatment group, whereas only 3 (14%) of 21 infants of 27 weeks' required such intubation. For infants who were not intubated in the DR, 36 infants (16 CPAP infants and 20 control infants) were subsequently intubated in the NICU by day 7, in accordance with the protocol. Overall, 80% of studied infants required intubation within the first 7 days of life. The care provided for 52 (95%) of 55 CPAP infants and 43 (88%) of the 49 control infants was in compliance with the study protocol, with an overall compliance of 91%.

CONCLUSIONS

This study demonstrated that infants could be randomized successfully to a DR intervention of CPAP/PEEP compared with no CPAP/PEEP, with intubation provided only for resuscitation indications, and subsequent intubation for prespecified criteria. Forty-five percent (47 of 104) of infants <28 weeks' gestation required intubation for resuscitation in the DR. CPAP/PEEP in the DR did not affect the need for intubation at birth or during the subsequent week. Overall, 20% of infants did not need intubation by 7 days of life. This experience should be helpful in facilitating the design of subsequent prospective studies of ventilatory support in ELBW infants.

Technique for intrapartum administration of surfactant without requirement for an endotracheal tube

OBJECTIVE

To evaluate the feasibility and safety of administering surfactant into the nasopharynx during delivery, thus permitting the baby to aspirate the solution into the fluid-filled airway as an air-fluid interface is established. This process avoids the endotracheal intubation (ETI) and positive pressure ventilation (PPV) usually associated with prophylaxis, thus avoiding the pulmonary barotrauma associated with the conventional method of surfactant administration.

STUDY DESIGN

In all, 23 neonates weighing 560 to 1804 g and born at 27 to 30 weeks had their nasopharyngeal airways suctioned and then 3.0-4.5 ml Infasurf instilled into the nasopharynx before delivery of the shoulders. Continuous positive airway pressure (CPAP) of 10 cmH(2)O was administered by mask as the babies initiated breathing. Nasal CPAP at 6 cmH(2)O was then continued for a minimum of 48 hours.

RESULTS

In all, 13 of 15 babies delivered vaginally were weaned quickly to room air and required no further surfactant or endotracheal intubation for RDS. Five of eight babies delivered by C-section required subsequent endotracheal intubation soon after birth and two received subsequent endotracheal tube surfactant.

CONCLUSION

Nasopharyngeal surfactant instillation at birth appears to be relatively safe and simple to accomplish, especially for vaginal births. A large randomized clinical trial will be required to determine the efficacy of this technique when compared to prophylaxis by endotracheal intubation and to nCPAP alone.

Surfactant therapy for respiratory distress syndrome in premature neonates: a comparative review

Exogenous surfactant therapy has been part of the routine care of preterm neonates with respiratory distress syndrome (RDS) since the beginning of the 1990s. Discoveries that led to its development as a therapeutic agent span the whole of the 20th century but it was not until 1980 that the first successful use of exogenous surfactant therapy in a human population was reported. Since then, randomized controlled studies demonstrated that surfactant therapy was not only well tolerated but that it significantly reduced both neonatal mortality and pulmonary air leaks; importantly, those surviving neonates were not at greater risk of subsequent neurological impairment. Surfactants may be of animal or synthetic origin. Both types of surfactants have been extensively studied in animal models and in clinical trials to determine the optimum timing, dose size and frequency, route and method of administration. The advantages of one type of surfactant over another are discussed in relation to biophysical properties, animal studies and results of randomized trials in neonatal populations. Animal-derived exogenous surfactants are the treatment of choice at the present time with relatively few adverse effects related largely to changes in oxygenation and heart rate during surfactant administration. The optimum dose of surfactant is usually 100 mg/kg. The use of surfactant with high frequency oscillation and continuous positive pressure modes of respiratory support presents different problems compared with its use with conventional ventilation. The different components of surfactant have important functions that influence its effectiveness both in the primary function of the reduction of surface tension and also in secondary, but nonetheless just as important, role of lung defense. With greater understanding of the individual surfactant components, particularly the surfactant-associated proteins, development of newer synthetic surfactants has been made possible. Despite being an effective therapy for RDS, surfactant has failed to have a significant impact on the incidence of chronic lung disease in survivors. Paradoxically the cost of care has increased as surviving neonates are more immature and consume a greater proportion of neonatal intensive care resources. Despite this, surfactant is considered a cost-effective therapy for RDS compared with other therapeutic interventions in premature infants.

Current surfactant use in premature infants

Exogenous surfactant therapy has been a significant advance in the management of preterm infants with RDS. It has become established as a standard part of the management of such infants. Both natural and synthetic surfactants lead to clinical improvement and decreased mortality, with natural surfactants having additional advantages over currently available synthetic surfactants. The use of prophylactic surfactant administered after initial stabilization at birth to infants at risk for RDS has benefits compared with rescue surfactant given to treat infants with established RDS. In infants who do not receive prophylaxis, earlier treatment (before 2 hours) has benefits over later treatment. The use of multiple doses of surfactant is a superior strategy to the use of a single dose, whereas the use of a higher threshold for retreatment seems to be as effective as a low threshold. Adverse effects of surfactant therapy are infrequent and usually not serious. Long-term follow-up of infants treated with surfactant in the neonatal period is reassuring. In the future we are likely to see the development of new types of surfactants. Further research is required to determine the optimal use of surfactant in conjunction with other respiratory interventions.

Calfactant

Surfactant administration has proven remarkably effective in the prevention and treatment of infantile respiratory distress syndrome (IRDS) and may also be beneficial in other forms of acute lung injury. Several surfactant products are available commercially along with others in various phases of development and clinical trials. While all of these products share an ability to lower surface tension in vitro, there are substantial compositional differences that appear to affect their in vivo efficacy. At present, the 'modified natural' surfactants containing the hydrophobic surfactant proteins SP-B and SP-C appear most effective. Calfactant may have a particular advantage because of its relatively high content of SP-B and its lack of contamination with non-surfactant lipids and proteins.

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.

Targeted early rescue surfactant in ventilated preterm infants using the click test

OBJECTIVE

To determine whether use of the click test, a rapid bedside test of surfactant function, results in earlier and more appropriate surfactant administration in ventilated preterm infants than does usual early rescue treatment.

STUDY DESIGN

Ventilated preterm infants (n = 126) with inspired oxygen >/=25% and mean airway pressure >/=7 cm H(2)O were randomized in gestational strata (<28 weeks and 28-36 weeks) to have surfactant therapy determined by the click test or by usual clinical and chest radiograph criteria. The treatment group had the click test performed on a tracheal aspirate as soon as possible after intubation and, if negative or equivocal (surfactant deficient), surfactant was given. The control group had surfactant given as soon as possible based on clinical and chest radiograph diagnoses of respiratory distress syndrome.

RESULTS

In infants of <28 weeks' gestation, use of the click test resulted in significantly earlier surfactant therapy (median time: 50 vs 159 minutes) and a reduction in the number of infants receiving surfactant (48% vs 79%). In infants of 28 to 36 weeks' gestation, there was no difference in time to surfactant (median time: 300 vs 268 minutes) or in the number of infants receiving surfactant. Neonatal morbidity and mortality were similar in click test and control groups.

CONCLUSIONS

Use of the click test in ventilated, extremely premature infants results in significantly earlier and more appropriately targeted administration of surfactant than does early rescue therapy based on clinical and radiograph criteria. A randomized trial of targeted early rescue surfactant therapy versus prophylactic surfactant therapy in infants of <28 weeks' gestation is warranted. The click test has the potential to improve clinical outcomes and reduce costs.

Neonatal acute respiratory failure

Acute respiratory failure is the most common problem seen in the preterm and term infants admitted to neonatal intensive care units. In preterm infants, the most common cause of acute respiratory failure is respiratory distress syndrome caused by surfactant deficiency. Acute respiratory failure in term and near term infants is usually a result of meconium aspiration syndrome, sepsis, pulmonary hypoplasia, and primary pulmonary hypertension of the newborn. The response to various methods of treatment may vary, depending on the severity of respiratory failure and the cause of the acute respiratory failure. We reviewed the evidence for efficacy and current utilization of newer treatment modalities, including exogenous surfactant administration, high frequency ventilation, inhaled nitric oxide therapy, antenatal steroids for the prevention of respiratory distress syndrome, and use of postnatal steroids for the prevention of chronic lung disease.

Early dexamethasone-attempting to prevent chronic lung disease

BACKGROUND

We previously demonstrated improved survival and early outcomes in a pilot trial of 2 doses of intravenous dexamethasone for infants with surfactant-treated respiratory distress syndrome. (1) A multicenter, randomized, double-blind trial was undertaken to confirm these results.

METHODS

Infants <30 weeks' gestation were eligible if they had respiratory distress syndrome, required mechanical ventilation at 12 to 18 hours of age, and had received at least 1 dose of exogenous surfactant. Infants were excluded if sepsis or pneumonia was suspected or if congenital heart disease or chromosomal abnormalities were present. A total of 384 infants were enrolled-189 randomized to dexamethasone (.5mg/kg birth weight at 12-18 hours of age and a second dose 12 hours later) and 195 to an equal volume of saline placebo.

RESULTS

No differences were found in the dexamethasone versus placebo groups, respectively, regarding the primary outcomes of survival (79% vs 83%), survival without oxygen at 36 weeks' corrected gestational age (CGA; both 59%), and survival without oxygen at 36 weeks' CGA and without late glucocorticoid therapy (46% vs 44%). No significant differences between the groups in estimates from Kaplan-Meier survival analyses were found for median days on oxygen (50 vs 56 days), ventilation (20 vs 27 days), days to regain birth weight (15.5 vs 14 days), or length of stay (LOS; 88 vs 89 days). Infants given early dexamethasone were less likely to receive later glucocorticoid therapy for bronchopulmonary dysplasia during their hospitalization (27% vs 35%). No clinically significant side effects were noted in the dexamethasone group, although there were transient elevations in blood glucose and blood pressure followed by a return to baseline by study day 10. Among infants who died (40 vs 33), there were no differences in the median days on oxygen, ventilation, nor LOS. However, in survivors (149 vs 162), the following were observed: median days on oxygen 37 versus 45 days, ventilation 14 versus 19 days, and LOS 79 versus 81 days, for the dexamethasone versus placebo groups, respectively.

CONCLUSIONS

This dose of early intravenous dexamethasone did not reduce the requirement for oxygen at 36 weeks' CGA and survival was not improved. However, early dexamethasone reduced the use of later prolonged dexamethasone therapy, and among survivors, reduced the median days on oxygen and ventilation. We conclude that this course of early dexamethasone probably represents a near minimum dose for instituting a prophylactic regimen against bronchopulmonary dysplasia.

Early versus delayed selective surfactant treatment for neonatal respiratory distress syndrome

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To compare the effects of early vs. delayed selective surfactant therapy for newborns intubated for respiratory distress within the first two hours of life. Planned subgroup analyses include separate comparisons for studies utilizing natural surfactant extract and synthetic surfactant.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, Medline (MeSH terms: pulmonary surfactant; text word: early; limits: age, newborn: publication type, clinical trial), PubMed, abstracts, conference and symposia proceedings, expert informants, and journal hand searching in the English language.

SELECTION CRITERIA

Only randomized controlled clinical trials comparing early selective surfactant administration (surfactant administration via the endotracheal tube in infants intubated for respiratory distress, not specifically for surfactant dosage) within the first 2 hours of life versus delayed selective surfactant administration to infants with established respiratory distress syndrome were considered for review.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including the incidence of pneumothorax, patent ductus arteriosus, pulmonary interstitial emphysema, pulmonary hemorrhage, necrotizing enterocolitis, retinopathy of prematurity, intraventricular hemorrhage (any and severe IVH), bronchopulmonary dysplasia, chronic lung disease, neonatal mortality, mortality prior to hospital discharge, bronchopulmonary dysplasia or death, and chronic lung disease or death were excerpted from the reports of the clinical trials by the reviewers. Data regarding the average number of surfactant doses per infant were also analyzed. Further analysis of data with regard to surfactant type was performed. Data analysis was performed in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Four randomized controlled trials met selection criteria. Two of the trials utilized synthetic surfactant (Exosurf Neonatal) and two utilized a natural surfactant extract. The meta-analyses demonstrated significant reductions in risk of pneumothorax (Typical RR 0.70, 95%CI 0.59, 0.82; Typical RD -0.05, 95%CI -0.08, -0.03), and pulmonary interstitial emphysema (Typical RR 0.63, 95%CI 0.43, 0.93; Typical RD -0.06, 95%CI -0.10, -0.01) in infants randomized to early selective surfactant administration. Infants randomized to early selective surfactant administration also demonstrated a decreased risk of neonatal mortality (Typical RR 0.87, 95%CI 0.77, 0.99; Typical RD -0.03, 95%CI -0.06, -0.00), chronic lung disease (Typical RR 0.70, 95%CI 0. 55, 0.88; Typical RD -0.03, 95%CI -0.05, -0.01), and chronic lung disease or death at 36 weeks (Typical RR 0.84, 95%CI 0.75, 0.93; Typical RD -0.06, 95%CI -0.09, -0.03). A trend toward risk reduction for bronchopulmonary dysplasia or death at 28 days was also evident (Typical RR 0.94, 95%CI 0.88, 1.00; Typical RD -0.04, 95%CI -0.07, -0.00). No differences in other complications of RDS or prematurity were noted.

REVIEWER'S CONCLUSIONS

Early selective surfactant administration given to infants with RDS requiring assisted ventilation leads to a decreased risk of acute pulmonary injury (decreased risk of pneumothorax and pulmonary interstitial emphysema) and a decreased risk of neonatal mortality and chronic lung disease compared to delaying treatment of such infants until they develop established RDS.

Prophylactic versus selective use of surfactant for preventing morbidity and mortality in preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To compare the effect of prophylactic surfactant administration to surfactant treatment of established respiratory distress syndrome in premature infants.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, Medline (MeSH terms: pulmonary surfactant; limits: age groups, newborn infants), previous reviews including cross-references, abstracts, conference and symposia proceedings, expert informants, and journal handsearching in the English language.

SELECTION CRITERIA

Randomized controlled trials which compared the effects of prophylactic surfactant administration to surfactant treatment of established respiratory distress syndrome in premature infants were included in the analysis.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including the incidence of pneumothorax, pulmonary interstitial emphysema, patent ductus arteriosus, necrotizing enterocolitis, intraventricular hemorrhage (any grade and severe intraventricular hemorrhage), bronchopulmonary dysplasia, mortality, bronchopulmonary dysplasia or death, and retinopathy of prematurity were excerpted from the reports of the clinical trials by the reviewers. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

The majority of included studies noted an initial improvement in the respiratory status and a decrease in the incidence of respiratory distress syndrome in infants who received prophylactic surfactant. The meta-analysis supports a decrease in the incidence of pneumothorax, a decrease in the incidence of pulmonary interstitial emphysema, a decrease in the incidence of mortality and a decrease in the incidence of bronchopulmonary dysplasia or death associated with prophylactic administration of surfactant. No significant untoward effects of prophylactic surfactant administration are noted.

REVIEWER'S CONCLUSIONS

Prophylactic surfactant administration to infants judged to be at risk of developing respiratory distress syndrome (intubated infants less than 30-32 weeks gestation) has been demonstrated to improve clinical outcome. Infants who receive prophylactic surfactant have a decreased incidence of pneumothorax, a decreased incidence of pulmonary interstitial emphysema and a decreased incidence of mortality. However, it remains unclear exactly which criteria should be used to judge "at risk" infants who would require prophylactic surfactant administration.

Following the learning curve: the evolution of kinder, gentler neonatal respiratory technology

Immense progress has been made in all aspects of neonatal critical care during the past 4 decades, particularly in the realm of respiratory support. A historical overview of the evolution of neonatal respiratory support illustrates how technological advances are improving survival and outcome for many sick newborns. Major milestones in this history include continuous positive airway pressure, conventional ventilation, exogenous surfactant, extracorporeal membrane oxygenation, and high frequency ventilation. Changes in clinical and nursing care highlight the significant impact of technological and practice advances on neonatal respiratory morbidity. Although bronchopulmonary dysplasia still occurs, the incidence and severity have decreased. The nature and outcome of the neonatal intensive-care experience has been redefined for many infants; however, great challenges remain in the care of infants on the edge of viability.

Calfactant: a review of its use in neonatal respiratory distress syndrome

Calfactant (Infasurt) is a natural bovine surfactant which has been evaluated for intratracheal use in the prevention and rescue treatment of respiratory distress syndrome (RDS) in preterm infants. In 2 randomised, double-blind, multicentre clinical trials of prophylactic use, calfactant 100 or 105 mg phospholipid per kg bodyweight (mg/kg) reduced RDS incidence, RDS severity and mortality rates to a greater extent than colfosceril palmitate (Exosurf Neonatal) 67.5 mg/kg and was generally similar to beractant (Survanta) 100 mg/kg. Although the rate of mortality before discharge from hospital was significantly higher in infants with birthweights <600 g who received calfactant than in those who received beractant, this may not be a typical result. As rescue treatment, calfactant 100 or 105 mg/kg reduced RDS severity, but not mortality rates, significantly more than colfosceril palmitate 67.5 mg/kg or beractant 100 mg/kg in 2 randomised, double-blind, multicentre clinical trials. In addition, the duration of effect of calfactant as prophylaxis or rescue treatment appeared to be longer than that of beractant. In other randomised trials, prophylaxis was more effective than rescue treatment with calfactant, particularly in infants of < or =29 weeks gestational age. The incidence of pulmonary air leak events was lower with calfactant than with colfosceril palmitate (12 vs 22%) but was identical with calfactant and beractant (15% with either agent). The incidence of other complications associated with RDS was usually similar with all 3 agents in clinical trials in preterm infants. The incidence of intraventricular haemorrhage was significantly higher in 1 clinical trial, and that of septicaemia was significantly lower in another, with calfactant versus colfosceril palmitate, but the combined incidences of these complications was similar with the 2 agents when results from different trials were pooled. The incidence of acute adverse events (i.e. those which occurred during administration of the drug) with calfactant was similar to that with beractant and higher than that with colfosceril palmitate; the difference may been related to reduced RDS severity in calfactant versus colfosceril palmitate recipients. Acute adverse events were usually transient and not severe.

CONCLUSIONS

Calfactant is a well tolerated natural bovine surfactant which is effective in the prevention and treatment of RDS in preterm infants. Further investigation is needed to more clearly determine the efficacy and tolerability of calfactant relative to that of other surfactant preparations. When more data are available, it is likely that calfactant will be useful as an alternative to beractant (at least in infants of birthweights >600 g), and calfactant may be preferred over colfosceril palmitate in both the prophylaxis and treatment of RDS.