Successful extubation of infants with respiratory distress syndrome using aminophylline

Neuroprotective effect of roflumilast under cerebral ischaemia/reperfusion injury in juvenile rats through NLRP-mediated inflammatory response inhibition

This study aims to investigate the protective effect of roflumilast, a phosphodiesterase (PDE)-4 enzyme inhibitor, and demonstrate its possible role in the development prevention of cerebral ischemia/reperfusion injury (CI/RI) after stroke induced by carotid artery ligation in juvenile rats. The rats were randomly divided into five groups: healthy group without any treatment, healthy group administered with 1 mg/kg roflumilast, CI group not administered with roflumilast, CI group administered with 0.5 mg/kg roflumilast, and CI group administered with 1 mg/kg roflumilast. In the CI groups, reperfusion was achieved 2h after ischemia induction; in the roflumilast groups, this drug was intraperitoneally administered immediately after reperfusion and at the 12th hour. At the end of 24h, the rats were sacrificed and their brain tissues removed for examination. The mRNA expressions obtained with real-time PCR of IL-1β, TNF-α, and NLRP3 significantly increased in the CI/RI-induced groups compared with the control group, and this increase was significantly lower in the groups administered with roflumilast compared with the CI/RI-induced groups. Moreover, ELISA revealed that both IL-1 β and IL-6 brain levels were significantly higher in the CI/RI-induced groups than in the controls. This increase was significantly lower in the groups administered with roflumilast compared with the CI/RI-induced groups. Histopathological studies revealed that the values closest to those of the healthy group were obtained from the roflumilast groups. Nissl staining revealed that the Nissl bodies manifested normal density in the healthy and roflumilast-administered healthy groups, but were rare in the CI/RI-induced groups. Roflumilast treatment increased these decreased Nissl bodies with increasing doses. Observations indicated that the Nissl body density was close to the value in the healthy group in the CI/RI-induced group administered with 1 mg/kg roflumilast. Overall, roflumilast reduced cellular damage caused by CI/RI in juvenile rats, and this effect may be mediated by NLRP3.

Synergistic effect of caffeine and glucocorticoids on expression of surfactant protein B (SP-B) mRNA

Administration of glucocorticoids and caffeine is a common therapeutic intervention in the neonatal period, but possible interactions between these substances are still unclear. The present study investigated the effect of caffeine and different glucocorticoids on expression of surfactant protein (SP)-B, crucial for the physiological function of pulmonary surfactant. We measured expression levels of SP-B, various SP-B transcription factors including erythroblastic leukemia viral oncogene homolog 4 (ErbB4) and thyroid transcription factor-1 (TTF-1), as well as the glucocorticoid receptor (GR) after administering different doses of glucocorticoids, caffeine, cAMP, or the phosphodiesterase-4 inhibitor rolipram in the human airway epithelial cell line NCI-H441. Administration of dexamethasone (1 µM) or caffeine (5 mM) stimulated SP-B mRNA expression with a maximal of 38.8±11.1-fold and 5.2±1.4-fold increase, respectively. Synergistic induction was achieved after co-administration of dexamethasone (1 mM) in combination with caffeine (10 mM) (206±59.7-fold increase, p<0.0001) or cAMP (1 mM) (213±111-fold increase, p = 0.0108). SP-B mRNA was synergistically induced also by administration of caffeine with hydrocortisone (87.9±39.0), prednisolone (154±66.8), and betamethasone (123±6.4). Rolipram also induced SP-B mRNA (64.9±21.0-fold increase). We detected a higher expression of ErbB4 and GR mRNA (7.0- and 1.7-fold increase, respectively), whereas TTF-1, Jun B, c-Jun, SP1, SP3, and HNF-3α mRNA expression was predominantly unchanged. In accordance with mRNA data, mature SP-B was induced significantly by dexamethasone with caffeine (13.8±9.0-fold increase, p = 0.0134). We found a synergistic upregulation of SP-B mRNA expression induced by co-administration of various glucocorticoids and caffeine, achieved by accumulation of intracellular cAMP. This effect was mediated by a caffeine-dependent phosphodiesterase inhibition and by upregulation of both ErbB4 and the GR. These results suggested that caffeine is able to induce the expression of SP-transcription factors and affects the signaling pathways of glucocorticoids, amplifying their effects. Co-administration of caffeine and corticosteroids may therefore be of benefit in surfactant homeostasis.

Sildenafil attenuates pulmonary inflammation and fibrin deposition, mortality and right ventricular hypertrophy in neonatal hyperoxic lung injury

Background

Phosphodiesterase-5 inhibition with sildenafil has been used to treat severe pulmonary hypertension and bronchopulmonary dysplasia (BPD), a chronic lung disease in very preterm infants who were mechanically ventilated for respiratory distress syndrome.

Methods

Sildenafil treatment was investigated in 2 models of experimental BPD: a lethal neonatal model, in which rat pups were continuously exposed to hyperoxia and treated daily with sildenafil (50–150 mg/kg body weight/day; injected subcutaneously) and a neonatal lung injury-recovery model in which rat pups were exposed to hyperoxia for 9 days, followed by 9 days of recovery in room air and started sildenafil treatment on day 6 of hyperoxia exposure. Parameters investigated include survival, histopathology, fibrin deposition, alveolar vascular leakage, right ventricular hypertrophy, and differential mRNA expression in lung and heart tissue.

Results

Prophylactic treatment with an optimal dose of sildenafil (2 × 50 mg/kg/day) significantly increased lung cGMP levels, prolonged median survival, reduced fibrin deposition, total protein content in bronchoalveolar lavage fluid, inflammation and septum thickness. Treatment with sildenafil partially corrected the differential mRNA expression of amphiregulin, plasminogen activator inhibitor-1, fibroblast growth factor receptor-4 and vascular endothelial growth factor receptor-2 in the lung and of brain and c-type natriuretic peptides and the natriuretic peptide receptors NPR-A, -B, and -C in the right ventricle. In the lethal and injury-recovery model we demonstrated improved alveolarization and angiogenesis by attenuating mean linear intercept and arteriolar wall thickness and increasing pulmonary blood vessel density, and right ventricular hypertrophy (RVH).

Conclusion

Sildenafil treatment, started simultaneously with exposure to hyperoxia after birth, prolongs survival, increases pulmonary cGMP levels, reduces the pulmonary inflammatory response, fibrin deposition and RVH, and stimulates alveolarization. Initiation of sildenafil treatment after hyperoxic lung injury and continued during room air recovery improves alveolarization and restores pulmonary angiogenesis and RVH in experimental BPD.

Apneic preterms and methylxanthines: arousal deficits, sleep fragmentation and suppressed spontaneous movements

OBJECTIVE

To determine if apneic preterm infants currently treated with methylxanthines develop evidence of sleep deprivation from cumulative arousal and motor activational effects.

STUDY DESIGN

Sleep, wake, arousal and actigraphic movements were monitored in extubated clinically stable premature infants (N=37). Neonates were free of other medications for >72 h and were grouped based on methylxanthine exposure: >5 days with caffeine (n=14), >5 days theophylline (n=13) or no prior exposure (n=10).

RESULT

Duration of methylxanthine treatment predicted increased arousals, wakefulness and actigraphic movements, and decreased active sleep. Recording from 1200 to 0500 hours, methylxanthine-treated groups showed reductions in all arousal parameters: waking state, number of wake epochs, brief arousals and composite arousal index, and shorter fast-burst, sleep-related motility than untreated controls.

CONCLUSION

In apneic preterms, chronic methylxanthine treatment appears to produce sleep deprivation secondary to the stimulatory action of methylxanthines on arousal and motor systems.

Bronchopulmonary dysplasia in preterm infants: pathophysiology and management strategies

Bronchopulmonary dysplasia (BPD) has classically been described as including inflammation, architectural disruption, fibrosis, and disordered/delayed development of the infant lung. As infants born at progressively earlier gestations have begun to survive the neonatal period, a 'new' BPD, consisting primarily of disordered/delayed development, has emerged. BPD causes not only significant complications in the newborn period, but is associated with continuing mortality, cardiopulmonary dysfunction, re-hospitalization, growth failure, and poor neurodevelopmental outcome after hospital discharge. Four major risk factors for BPD include premature birth, respiratory failure, oxygen supplementation, and mechanical ventilation, although it is unclear whether any of these factors is absolutely necessary for development of the condition. Genetic susceptibility, infection, and patent ductus arteriosus have also been implicated in the pathogenesis of the disease. The strategies with the strongest evidence for effectiveness in preventing or lessening the severity of BPD include prevention of prematurity and closure of a clinically significant patent ductus arteriosus. Some evidence of effectiveness also exists for single-course therapy with antenatal glucocorticoids in women at risk for delivering premature infants, surfactant replacement therapy in intubated infants with respiratory distress syndrome, retinol (vitamin A) therapy, and modes of respiratory support designed to minimize 'volutrauma' and oxygen toxicity. The most effective treatments for ameliorating symptoms or preventing exacerbation in established BPD include oxygen therapy, inhaled glucocorticoid therapy, and vaccination against respiratory pathogens.Many other strategies for the prevention or treatment of BPD have been proposed, but have weaker or conflicting evidence of effectiveness. In addition, many therapies have significant side effects, including the possibility of worsening the disease despite symptom improvement. For instance, supraphysiologic systemic doses of glucocorticoids lessen the incidence of BPD in infants at risk for the disease, and promote weaning of oxygen and mechanical ventilation in infants with established BPD. However, the side effects of systemic glucocorticoid therapy, most notably the recently recognized adverse effects on neurodevelopment, preclude their routine use for the prevention or treatment of BPD. Future research in BPD will most probably focus on continued incremental improvements in outcome, which are likely to be achieved through the combined effects of many therapeutic modalities.

Effects of theophylline on the pattern of spontaneous breathing in preterm infants less than 1000 g of birth weight

Proportional assist ventilation (PAV) amplifies the ventilatory effect of the spontaneous respiratory effort and therefore allows analysis of drug-induced changes in the spontaneous breathing pattern of subjects who depend on mechanical ventilatory assistance. We hypothesized that theophylline will reduce the number and duration of respiratory pauses and apneic events in infants less than 1000 g of birth weight on PAV. Twelve infants were studied: median birth weight was 773 g; gestational age 26.0 weeks and postnatal age 9 days. Measurements were obtained over a 2-h period before and after 5 mg/kg of intravenous theophylline. A respiratory pause was defined as cessation of breathing for at least the duration of three preceeding breaths. The total number of respiratory pauses and the number of apneas followed by either cardiac slowing (decrease in heart rate more than 10%) or bradycardia decreased significantly. Minute ventilation increased due to a rise in tidal volume from 5.6+/-1.3 to 6.1+/-1.2 ml/kg (p=0.004). The duration of respiratory pauses, the respiratory rate, and the number of apneas followed by desaturation did not change significantly. We conclude that theophylline stimulates spontaneous breathing in infants less than 1000 g, reduces the number of apneas, and increases minute volume by increasing the tidal volumes.

Metabolic and respiratory effects of theophylline in the preterm infant

BACKGROUND

Methylxanthines are often administered to preterm infants for the treatment of apnoea.

AIMS

To study the effects of theophylline on energy metabolism, physical activity, and lung mechanics in preterm infants.

METHODS

Indirect calorimetry was performed for six hours before and after administration of a bolus of theophylline (5 mg/kg) in 18 preterm infants while physical activity was recorded with a video camera. Lung mechanics measurements were performed at baseline and 12 and 24 hours after theophylline treatment.

RESULTS

Theophylline increased mean (SEM) energy expenditure by 15 (5) kJ/kg/day and augmented carbohydrate utilisation from 6.8 to 8.0 g/kg/day, but fat oxidation was unchanged. After theophylline treatment, preterm infants had faster respiration, lower transcutaneous CO2, and improved static respiratory compliance without increased physical activity.

CONCLUSIONS

A bolus of 5 mg/kg theophylline increased energy expenditure independently of physical activity, increased carbohydrate utilisation, and improved respiratory compliance. The increased energy expenditure could be detrimental to the growth of the preterm infant.

Population pharmacokinetics of caffeine in neonates and young infants

The population pharmacokinetics of caffeine were investigated in 60 neonates and young infants using data collected during routine therapeutic drug monitoring. Clearance was influenced by body weight and postnatal age, and increased in the presence of dexamethasone. No clinical factors were identified that influenced volume of distribution. The population pharmacokinetic parameter estimates were then tested prospectively in a further 20 neonates. Although they produced unbiased results, the dexamethasone effect could not be identified. A final analysis using all 80 patients found clearance (L/day) = 0.14 x weight (kg) + 0.0024 x postnatal age (days) (+/- 20%) and volume of distribution = 0.82 L (+/- 24%). Simulations based on these results indicated that the current dosage guidelines of 20 mg/kg loading dose of caffeine citrate followed by a 5 mg/kg/day maintenance dose should achieve concentrations within the traditional target range in > 70% of neonates.

Does continuous positive airway pressure (CPAP) during weaning from intermittent mandatory ventilation in very low birth weight infants have risks or benefits? A controlled trial

OBJECTIVE

The purpose of this study was to evaluate three ventilator weaning strategies and to evaluate whether the use of continuous positive airway pressure (CPAP) via a nasopharyngeal or endotracheal tube would increase the likelihood of extubation failure in very low birth weight (VLBW) infants.

STUDY DESIGN

We studied prospectively 87 preterm infants (mean +/- SD; birth weight: 1078 +/- 188 g; gestational age: 28.8 +/- 2.2 weeks) who were in the process of being weaned from intermittent mandatory ventilation (IMV). Infants were assigned by systematic sampling to one of the following three treatment groups: (1) direct extubation from IMV (D.EXT) (n = 30); (2) preextubation endotracheal CPAP (ET-CPAP) for 12-24 hr (n = 28); or (3) postextubation nasopharyngeal CPAP (NP-CPAP) for 12-24 hr (n = 29). Failure was defined as the need for resumption of mechanical ventilation within 72 hr of extubation due to frequent or severe apnea and/or respiratory failure (pH < 7.25, PaCO2 > 60 mm Hg, and/or requirement for oxygen FiO2 > 60%).

RESULTS

There were no significant differences in failure rates among the three procedures. Failures were 2/30 (7%) in D.EXT; 4/28 (14%) in ET-CPAP; and 7/29 (24%) in the NP-CPAP. There were also no differences in FiO2, PaO2, and respiratory rates before and after discontinuation of IMV among the three groups. PaCO2 values were slightly higher in the NP-CPAP group 12-24 hr after weaning from IMV.

CONCLUSION

We were unable to demonstrate a clear difference in extubation outcome by use of CPAP administered via an endotracheal or nasopharyngeal tube when compared to direct extubation from low-rate IMV in VLBW infants.

Aminophylline therapy and cerebral blood flow velocity in preterm infants

Pulsed Doppler ultrasound was used to evaluate the cerebral blood flow velocity (CBFV), in the middle and anterior cerebral arteries in 10 infants before and after the administration of aminophylline (7.5 mg/kg). Mean CBFV, heart rate, blood pressure, oxygen and carbon dioxide tensions were recorded before the loading dose, and then at 1, 2, 6 and 24 h after completion of the infusion. Mean CBFV in the middle and anterior cerebral arteries were 16.8 cm/s and 10.8 cm/s respectively prior to the infusion. There was a significant decrease (P < 0.05) in velocities in both arteries at 1 and 2h post drug therapy, which returned to base values by 6 h, and remained as such at 24 h. The heart rate increased (P < 0.05) after the infusion, while no consistent changes were observed in blood pressure or oxygen tension. Carbon dioxide levels were significantly reduced (P < 0.05) at 2 h. The reduction in CBFV, however, was more than would be expected on the basis of the change in carbon dioxide levels alone, suggesting that other factors may be exerting an influence. While no adverse effects were noted in the infants studied, it is suggested that aminophylline should be used judiciously in sick preterm infants at highest risk from ischaemic brain injury.

Response to added dead space in ventilated preterm neonates and outcome of trial of extubation

The ventilatory response to an added external dead space was assessed in preterm babies, recovering from respiratory distress syndrome, immediately prior to extubation. All babies were ready for extubation as defined by routine clinical criteria. Baseline measurements of respiratory rate, tidal volume, and minute ventilation were made over a 2 min period using a computerized system consisting of a pneumotachometer connected directly to the proximal end of the endotracheal tube. The measurements were repeated after addition of an external dead space equivalent to 2 anatomical dead spaces (4.4 mL/kg body weight). Thirty-four babies were studied on 40 occasions. Twenty-four infants (60%) were successfully extubated and 16 (40%) required reintubation. Infants in the success and failure groups were matched for gestation at birth, postconceptional age and weight at the time of study, maximum ventilatory requirements, and treatment with methylxanthines. The added external dead space resulted in an increase in minute ventilation in 38 out of the 40 studies. Extubation success and failure groups were compared by expressing the minute ventilation after addition of the external dead space as a percentage of the baseline minute ventilation (%MV1). Successful extubation was associated with a higher median %MV1 compared with babies who failed extubation (156; range, 89.3 to 230; compared to 131; range, 75.2 to 165; P = 0.006). This test may be useful in deciding which babies could be successfully extubated.

Drug therapy for bronchopulmonary dysplasia

With improved survival of critically ill premature infants, BPD has become an important sequela of neonatal intensive care. A variety of medications are used in the management of BPD. In this article we have attempted to summarize clinical efficacy, pharmacokinetics, and side effects of many of these medications. Longer-term studies on the efficacy of drug therapy are needed and may be facilitated by the development of accurate and reproducible computerized techniques for the measurement of pulmonary mechanics in neonates. Ultimately, new pharmacologic agents or other strategies that will prevent lung injury from hyperoxia and mechanical ventilation or accelerate tissue repair once injury occurs will play a major role in the prevention and treatment of infants with BPD.

Inadequacy of FDA dosing guidelines for theophylline use in neonates

The efficacy of the FDA guidelines for theophylline dosing in newborns was evaluated retrospectively in 224 patients who had clearance data available. Mean projected post loading dose serum concentration was 4.1 +/- 1.0 mg/L in 160 patients. Mean projected steady-state concentration was 4.8 +/- 1.6 mg/L in 189 patients receiving intravenous aminophylline and 4.2 +/- 1.3 mg/L in 35 patients on oral therapy. Projected serum concentrations were subtherapeutic (less than 6.0 mg/L) in 181 of the 224 patients analyzed. There was a statistically significant difference in serum concentrations between asphyxiated and nonasphyxiated patients (p less than 0.001). There was no significant difference in mean projected serum concentrations between patients age 26-41 weeks (postconceptional age). This study suggests that the FDA dosing guidelines for theophylline in infants is inadequate and results in subtherapeutic (less than 6.0 mg/L) serum concentrations in the majority of newborns.

Principles of neonatal assisted ventilation

Based on the current knowledge of pulmonary mechanics and the results of clinical studies, we have reviewed principles that govern gas exchange during assisted ventilation in infants with RDS. Guidelines for changes in ventilator settings have been presented with respect to their specific effects on CO2 elimination and O2 uptake. In addition, their possible mechanisms of action and potential side effects have been addressed. General strategies have been presented, but they must be employed with caution. All infants will not exhibit the expected response to changes in ventilator setting, and thus their ventilatory management, as well as their general medical care, will need to be individualized.

The therapeutic actions of theophylline in preterm ventilated infants

40 preterm, ventilated infants (gestational ages 24-33 weeks) were entered into a double-blind randomised trial to assess the effect of oral theophylline on lung function and ventilator dependence. Theophylline administration was associated with a significant improvement in compliance (P less than 0.05) and hastened weaning from ventilation (P less than 0.01).

The efficacy of oral theophylline in ventilated premature infants

40 ventilated premature infants, with gestational ages of 24-34 weeks and a mean birthweight of 1422 g, were entered into a randomised controlled trial. 20 of the infants received orally 5 mg/ml anhydrous theophylline dissolved in 20% pure alcohol, with a loading dose of 5 mg/kg and then 1.25 mg/kg every 6 h. Plasma samples were assayed via an emit enzyme immunoassay, demonstrating satisfactory serum levels in all infants at 54 h after the loading dose. Possible side-effects were seen only in two infants, in one a tachycardia (220 beats/min) and the other became agitated during treatment.

Bronchopulmonary dysplasia. Chronic pulmonary disease following neonatal respiratory failure

Infants with respiratory failure in the first weeks of life may develop a chronic pulmonary condition called bronchopulmonary dysplasia. Their lungs have areas of atelectasis and areas of air trapping from variable obstruction of the airways. These infants may be dependent on supplemental oxygen or a ventilator and may require hospitalization for months, and have symptoms of airway obstruction which last for years. They require meticulous medical management to avoid a number of common complications such as patent ductus arteriosus, cor pulmonale, tracheal stenosis, recurrent aspiration, and death. The condition of most infants improves over the first two years. Preliminary studies suggest that their exercise and pulmonary function is usually close to normal by school-age. The long-term implications for the increasing number of children with this disease who will soon reach adulthood are still unknown.