Amplitude-integrated electroencephalography shows that doxapram influences the brain activity of preterm infants

Doxapram for apnoea of prematurity and neurodevelopmental outcomes at age 5-6 years

OBJECTIVE

To assess the long-term neurodevelopmental impact of doxapram for treating apnoea of prematurity.

DESIGN

Secondary analysis of the French national cohort study EPIPAGE-2. Recruitment took place in 2011. A standardised neurodevelopmental assessment was performed at age 5-6 years. A 2:1 propensity score matching was used to control for the non-randomised assignment of doxapram treatment.

SETTING

Population-based cohort study.

PATIENTS

All children born before 32 weeks' gestation alive at age 5-6 years.

INTERVENTIONS

Blind and standardised assessment by trained neuropsychologists and paediatricians at age 5-6 years.

MAIN OUTCOME MEASURES

Neurodevelopmental outcomes at age 5-6 years assessed by trained paediatricians and neuropsychologists: cerebral palsy, developmental coordination disorders, IQ and behavioural difficulties. A composite criterion for overall neurodevelopmental disabilities was built.

RESULTS

The population consisted of 2950 children; 275 (8.6%) received doxapram. Median (IQR) gestational age was 29.4 (27.6-30.9) weeks. At age 5-6 years, complete neurodevelopmental assessment was available for 60.3% (1780 of 2950) of children and partial assessment for 10.6% (314 of 2950). In the initial sample, children receiving doxapram had evidence of greater clinical severity than those not treated. Doxapram treatment was associated with overall neurodevelopmental disabilities of any severity (OR 1.43, 95% CI 1.07 to 1.92, p=0.02). Eight hundred and twenty-one children were included in the 2:1 matched sample. In this sample, perinatal characteristics of both groups were similar and doxapram treatment was not associated with overall neurodevelopmental disabilities (OR 1.09, 95% CI 0.76 to 1.57, p=0.63).

CONCLUSIONS

In children born before 32 weeks' gestation, doxapram treatment for apnoea of prematurity was not associated with neurodevelopmental disabilities.

The effect of acute respiratory events and respiratory stimulants on EEG-recorded brain activity in neonates: A systematic review

Objective

We conducted a systematic review to investigate electroencephalography (EEG) changes during periods of acute respiratory events such as apnoea and the effect of respiratory stimulants on EEG features in infants.

Methods

Studies examining respiration and EEG-recorded brain activity in human neonates between 28 and 42 weeks postmenstrual age were included. Two reviewers independently screened all records and included studies were assessed using the Joanna Briggs Institute Critical Appraisal Tool. The protocol was registered in PROSPERO (CRD42022339873).

Results

We identified 14 studies with a total of 534 infants. Nine articles assessed EEG changes in relation to apnoea, one assessed hiccups, and four investigated the effect of respiratory stimulants. The relationship between neonatal apnoea and EEG changes was inconsistent; EEG suppression and decreased amplitude and frequency were observed during some, but not all, apnoeas. Respiratory stimulants increased EEG continuity compared with before use.

Conclusions

Current studies in this area are constrained by small sample sizes. Diverse exposure definitions and outcome measures impact inference.

Significance

This review highlights the need for further work; understanding the relationship between respiration and the developing brain is key to mitigating the long-term effects of apnoea.

Doxapram for the prevention and treatment of apnea in preterm infants

BACKGROUND

Apnea of prematurity is a common problem in preterm infants that may have significant consequences on their development. Methylxanthines (aminophylline, theophylline, and caffeine) are effective in the treatment of apnea of prematurity. Doxapram is used as a respiratory stimulant in cases refractory to the methylxanthine treatment.

OBJECTIVES

To evaluate the benefits and harms of doxapram administration on the incidence of apnea and other short-term and longer-term clinical outcomes in preterm infants.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was March 2023.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) assessing the role of doxapram in prevention and treatment of apnea of prematurity and prevention of reintubation in preterm infants (less than 37 weeks' gestation). We included studies comparing doxapram with either placebo or methylxanthines as a control group, or when doxapram was used as an adjunct to methylxanthines and compared to methylxanthines alone as a control group. We included studies of doxapram at any dose and route.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were clinical apnea, need for positive pressure ventilation after initiation of treatment, failed apnea reduction after two to seven days, and failed extubation (defined as unable to wean from invasive intermittent positive pressure ventilation [IPPV] and extubate or reintubation for IPPV within one week). We used GRADE to assess the certainty of evidence for each outcome.

MAIN RESULTS

We included eight RCTs enrolling 248 infants. Seven studies (214 participants) provided data for meta-analysis. Five studied doxapram for treatment of apnea in preterm infants. Three studied doxapram to prevent reintubation in preterm infants. None studied doxapram in preventing apnea in preterm infants. All studies administered doxapram intravenously as continuous infusions. Two studies used doxapram as an adjunct to aminophylline compared to aminophylline alone and one study as an adjunct to caffeine compared to caffeine alone. When used to treat apnea, compared to no treatment, doxapram may result in a slight reduction in failed apnea reduction (risk ratio [RR] 0.45, 95% confidence interval [CI] 0.20 to 1.05; 1 study, 21 participants; low-certainty evidence). The evidence is very uncertain about the effect of doxapram on need for positive pressure ventilation after initiation of treatment (RR 0.31, 95% CI 0.01 to 6.74; 1 study, 21 participants; very low-certainty evidence). Doxapram may result in little to no difference in side effects causing cessation of therapy (0 events in both groups; risk difference [RD] 0.00, 95% CI -0.17 to 0.17; 1 study, 21 participants; low-certainty evidence). Compared to alternative treatment, the evidence is very uncertain about the effect of doxapram on failed apnea reduction (RR 1.35, 95% CI 0.53 to 3.45; 4 studies, 84 participants; very low-certainty evidence). The evidence is very uncertain about the effect of doxapram on need for positive pressure ventilation after initiation of treatment (RR 2.40, 95% CI 0.11 to 51.32; 2 studies, 37 participants; very-low certainty evidence; note 1 study recorded 0 events in both groups. Thus, the RR and CIs were calculated from 1 study rather than 2). Doxapram may result in little to no difference in side effects causing cessation of therapy (0 events in all groups; RD 0.00, 95% CI -0.15 to 0.15; 37 participants; 2 studies; low-certainty evidence). As adjunct therapy to methylxanthine, the evidence is very uncertain about the effect of doxapram on failed apnea reduction after two to seven days (RR 0.08, 95% CI 0.01 to 1.17; 1 study, 10 participants; very low-certainty evidence). No studies reported on clinical apnea, chronic lung disease at 36 weeks' postmenstrual age (PMA), death at any time during initial hospitalization, long-term neurodevelopmental outcomes in the three comparisons, and need for positive pressure ventilation and side effects when used as adjunct therapy to methylxanthine. In studies to prevent reintubation, when compared to alternative treatment, the evidence is very uncertain about the effect of doxapram on failed extubation (RR 0.43, 95% CI 0.10 to 1.83; 1 study, 25 participants; very low-certainty evidence). As adjunct therapy to methylxanthine, doxapram may result in a slight reduction in 'clinical apnea' after initiation of treatment (RR 0.36, 95% CI 0.13 to 0.98; 1 study, 56 participants; low-certainty evidence). Doxapram may result in little to no difference in failed extubation (RR 0.92, 95% CI 0.52 to 1.62; 1 study, 56 participants; low-certainty evidence). The evidence is very uncertain about the effect of doxapram on side effects causing cessation of therapy (RR 6.42, 95% CI 0.80 to 51.26; 2 studies, 85 participants; very low-certainty evidence). No studies reported need for positive pressure ventilation, chronic lung disease at 36 weeks' PMA, long-term neurodevelopmental outcomes in the three comparisons; failed extubation when compared to no treatment; and clinical apnea, death at any time during initial hospitalization, and side effects when compared to no treatment or alternative treatment. We identified two ongoing studies, one conducted in Germany and one in multiple centers in the Netherlands and Belgium.

AUTHORS' CONCLUSIONS

In treating apnea of prematurity, doxapram may slightly reduce failure in apnea reduction when compared to no treatment and there may be little to no difference in side effects against both no treatment and alternative treatment. The evidence is very uncertain about the need for positive pressure ventilation when compared to no treatment or alternative treatment and about failed apnea reduction when used as alternative or adjunct therapy to methylxanthine. For use to prevent reintubation, doxapram may reduce apnea episodes when administered in adjunct to methylxanthine, but with little to no difference in failed extubation. The evidence is very uncertain about doxapram's effect on death when used as adjunct therapy to methylxanthine and about failed extubation when used as alternative or adjunct therapy to methylxanthine. There is a knowledge gap about the use of doxapram as a therapy to prevent apnea. More studies are needed to clarify the role of doxapram in the treatment of apnea of prematurity, addressing concerns about long-term outcomes. The ongoing studies may provide useful data.

Doxapram versus placebo in preterm newborns: a study protocol for an international double blinded multicentre randomized controlled trial (DOXA-trial)

BACKGROUND

Apnoea of prematurity (AOP) is one of the most common diagnoses among preterm infants. AOP often leads to hypoxemia and bradycardia which are associated with an increased risk of death or disability. In addition to caffeine therapy and non-invasive respiratory support, doxapram might be used to reduce hypoxemic episodes and the need for invasive mechanical ventilation in preterm infants, thereby possibly improving their long-term outcome. However, high-quality trials on doxapram are lacking. The DOXA-trial therefore aims to investigate the safety and efficacy of doxapram compared to placebo in reducing the composite outcome of death or severe disability at 18 to 24 months corrected age.

METHODS

The DOXA-trial is a double blinded, multicentre, randomized, placebo-controlled trial conducted in the Netherlands, Belgium and Canada. A total of 396 preterm infants with a gestational age below 29 weeks, suffering from AOP unresponsive to non-invasive respiratory support and caffeine will be randomized to receive doxapram therapy or placebo. The primary outcome is death or severe disability, defined as cognitive delay, cerebral palsy, severe hearing loss, or bilateral blindness, at 18-24 months corrected age. Secondary outcomes are short-term neonatal morbidity, including duration of mechanical ventilation, bronchopulmonary dysplasia and necrotising enterocolitis, hospital mortality, adverse effects, pharmacokinetics and cost-effectiveness. Analysis will be on an intention-to-treat principle.

DISCUSSION

Doxapram has the potential to improve neonatal outcomes by improving respiration, but the safety concerns need to be weighed against the potential risks of invasive mechanical ventilation. It is unknown if the use of doxapram improves the long-term outcome. This forms the clinical equipoise of the current trial. This international, multicentre trial will provide the needed high-quality evidence on the efficacy and safety of doxapram in the treatment of AOP in preterm infants.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04430790 and EUDRACT 2019-003666-41. Prospectively registered on respectively June and January 2020.

The bioavailability and maturing clearance of doxapram in preterm infants

BACKGROUND

Doxapram is used for the treatment of apnea of prematurity in dosing regimens only based on bodyweight, as pharmacokinetic data are limited. This study describes the pharmacokinetics of doxapram and keto-doxapram in preterm infants.

METHODS

Data (302 samples) from 75 neonates were included with a median (range) gestational age (GA) 25.9 (23.9-29.4) weeks, bodyweight 0.95 (0.48-1.61) kg, and postnatal age (PNA) 17 (1-52) days at the start of continuous treatment. A population pharmacokinetic model was developed using non-linear mixed-effects modelling (NONMEM®).

RESULTS

A two-compartment model best described the pharmacokinetics of doxapram and keto-doxapram. PNA and GA affected the formation clearance of keto-doxapram (CL_{FORMATION KETO-DOXAPRAM}) and clearance of doxapram via other routes (CL_{DOXAPRAM OTHER ROUTES}). For a median individual of 0.95 kg, GA 25.6 weeks, and PNA 29 days, CL_{FORMATION KETO-DOXAPRAM} was 0.115 L/h (relative standard error (RSE) 12%) and CL_{DOXAPRAM OTHER ROUTES} was 0.645 L/h (RSE 9%). Oral bioavailability was estimated at 74% (RSE 10%).

CONCLUSIONS

Dosing of doxapram only based on bodyweight results in the highest exposure in preterm infants with the lowest PNA and GA. Therefore, dosing may need to be adjusted for GA and PNA to minimize the risk of accumulation and adverse events. For switching to oral therapy, a 33% dose increase is required to maintain exposure.

IMPACT

Current dosing regimens of doxapram in preterm infants only based on bodyweight result in the highest exposure in infants with the lowest PNA and GA. Dosing of doxapram may need to be adjusted for GA and PNA to minimize the risk of accumulation and adverse events. Describing the pharmacokinetics of doxapram and its active metabolite keto-doxapram following intravenous and gastroenteral administration enables to include drug exposure to the evaluation of treatment of AOP. The oral bioavailability of doxapram in preterm neonates is 74%, requiring a 33% higher dose via oral than intravenous administration to maintain exposure.

Precision Dosing of Doxapram in Preterm Infants Using Continuous Pharmacodynamic Data and Model-Based Pharmacokinetics: An Illustrative Case Series

INTRODUCTION

Current drug dosing in preterm infants is standardized, mostly based on bodyweight. Still, covariates such as gestational and postnatal age may importantly alter pharmacokinetics and pharmacodynamics. Evaluation of drug therapy in these patients is very difficult because objective pharmacodynamic parameters are generally lacking. By integrating continuous physiological data with model-based drug exposure and data on adverse drug reactions (ADRs), we aimed to show the potential benefit for optimized individual pharmacotherapy.

MATERIALS AND METHODS

Continuous data on oxygen saturation (SpO2), fraction of inspired oxygen (FiO2) and composite parameters, including the SpO2/FiO2 ratio and the cumulative oxygen shortage under the 89% SpO2 limit, served as indicators for doxapram effectiveness. We analyzed these continuous effect data, integrated with doxapram exposure and ADR parameters, obtained in preterm infants around the start of doxapram therapy. The exposures to doxapram and the active metabolite keto-doxapram were simulated using a population pharmacokinetic model. Infants were selected and retrospectively compared on the indication to start doxapram, the first response to doxapram, a potential dose-response relationship, and the administered dosage over time. Recommendations were made for individual improvements of therapy.

RESULTS

We provide eight cases of continuous doxapram administration that illustrate a correct and incorrect indication to start doxapram, responders and non-responders to therapy, and unnecessary over-exposure with ADRs. Recommendations for improvement of therapy include: objective evaluation of added effect of doxapram after start, prevention of overdosing by earlier down-titration or termination of therapy, and the prevention of hypoxia and agitation by measuring specific parameters at strategical time-points.

CONCLUSION

Real-time and non-invasive effect monitoring of drug therapy combined with model-based exposure provides relevant information to clinicians and can importantly improve therapy. The variability between and within patients emphasizes the importance of individual, objective evaluation of pharmacotherapy. These measurements, together with data on ADRs, allow for precision medicine in neonatology that should be brought to the bedside.

Early preterm infants with abnormal psychomotor neurodevelopmental outcome at age two show alterations in amplitude-integrated electroencephalography signals

INTRODUCTION

Recent studies showed that neurodevelopment in preterm infants can be predicted by using amplitude-integrated electroencephalography (aEEG)-derived parameters. In our previous study we demonstrated that aEEG could be useful in predicting neurodevelopmental outcome in very preterm infants at the corrected age of 2 years.

AIM

The aim of this study was to further evaluate aEEG for predicting neurodevelopmental outcome at the at the corrected age of 2 years in preterm infants.

METHODS

Between July 2010 and June 2016 440 very preterm infants were eligible for the study at Innsbruck Medical University Hospital. The aEEG was evaluated for the Burdjalov score in 306 preterm infants (mean gestational age 29.5 weeks; range: 24.1-31.9 weeks). At the corrected age of 2 years outcome was assessed by the Bayley Scales of Infant and Toddler Development.

RESULTS

The cohort was divided into three subgroups: 248 infants with normal outcome, 40 infants with delayed outcome and 18 infants with abnormal outcome. Burdjalov scores were lower in infants with delayed outcome than in infants with normal outcome and even lower in infants with abnormal outcome. Post-hoc analysis showed significant differences between normal and delayed psychomotor outcome at 18-24 h (5 (3;6) versus 3 (3;5), p = .024), 30-36 h (6 (4;8) versus 4 (4;6), p = .033), 42-48 h (7 (5;8.5) versus 4 (4;7), p = .003), 54-60 h (7 (6;9) versus 5 (4;7), p = .003), 66-72 h (8 (6;9) versus 6.5 (4.25;7.75), p = .027) and week one (8 (7;10) versus 6.5 (5;8), p = .021). Additionally, when comparing normal to abnormal outcome, a significant difference was found at week four (12 (9;12) versus 8 (7;10), p = .024). The Burdjalov score was only predictive for a delayed psychomotor outcome, presenting the highest area under the curve (0.690) at week two of life.

CONCLUSION

We observed differences in aEEG signals and neurodevelopmental outcome at the corrected age of 2 years, especially for psychomotor outcome. The predictive value of the Burdjalov score regarding neurodevelopmental outcome at the corrected age of 2 years in preterm infants was low.

Retrospective study shows that doxapram therapy avoided the need for endotracheal intubation in most premature neonates

AIM

Using doxapram to treat neonates with apnoea of prematurity might avoid the need for endotracheal intubation and invasive ventilation. We studied whether doxapram prevented the need for intubation and identified the predictors of the success.

METHODS

This was a retrospective study of preterm infants born from January 2006 to August 2014 who received oral or intravenous doxapram. Success was defined as no need for endotracheal intubation, due to apnoea, during doxapram therapy. Univariable and multivariable logistic regression analyses identified predictors of success during the first 48 hours of doxapram therapy.

RESULTS

Data on 203 patients with a median gestational age of 26.1 (interquartile range 25.1-27.4) weeks were analysed. During the first 48 hours of doxapram therapy, 157 (77%) patients did not need endotracheal intubation and 127 (63%) patients were successfully treated over the entire treatment course. The median postnatal age at the start of doxapram therapy was 20 days (interquartile range 12-30). Postnatal age and a lower fraction of inspired oxygen at the start of doxapram therapy were significant predictors of success (odds ratio 0.964, 95% confidence interval 0.938-0.991, p = 0.001).

CONCLUSION

Oral and intravenous doxapram effectively treated most cases of apnoea in preterm infants, avoiding the need for intubation.

Treatment Effects on Neonatal EEG

Conventional EEG and amplitude-integrated electroencephalography are used in neonates to assess prognosis and significant changes in brain activity. Neuroactive medications and hypothermia can influence brain activity and therefore alter EEG interpretation. There are limited studies on the effect of these therapies on neonatal EEG background activity. Medication effects on the EEG or amplitude-integrated electroencephalography include increased interburst interval duration, voltage suppression, and sleep disruption. The effect is transient in term newborns but can be persistent in premature newborns. Although therapeutic hypothermia does not produce significant changes in EEG activity, it does change the time point at which EEG can accurately predict neurodevelopmental outcome. It is important to account for these effects on the EEG to avoid inaccurate interpretation that may affect prognostication.

Doxapram Treatment for Apnea of Prematurity: A Systematic Review

BACKGROUND

Apnea of prematurity (AOP) is a common complication of preterm birth, for which caffeine is the first treatment of choice. In case of persistent AOP, doxapram has been advocated as an additional therapy.

OBJECTIVE

To identify and appraise all existing evidence regarding efficacy and safety of doxapram use for AOP in infants born before 34 weeks of gestational age.

METHODS

All studies reporting on doxapram use for AOP were identified by searching electronic databases, references from relevant studies, and abstracts from the Societies for Pediatric Research. Two reviewers independently assessed study eligibility and quality, and extracted data on study design, patient characteristics, efficacy and safety outcomes.

RESULTS

The randomized controlled trials showed less apnea during doxapram treatment when compared to placebo, but no difference in treatment effect when compared to theophylline. No serious adverse effects were reported. We identified 28 observational studies consisting mainly of cohort studies and case series (n = 1,994). There was considerable heterogeneity in study design and quality. Most studies reported a positive effect of doxapram on apnea rate. A few studies reported on long-term outcomes with conflicting results. A range of possible doxapram-related short-term adverse effects were reported, sometimes associated with the use of higher doses.

CONCLUSION

Based on the limited number of studies and level of evidence, no firm conclusions on the efficacy and safety of doxapram in preterm infants can be drawn. For this reason, routine use cannot be recommended. A large multicenter randomized controlled trial is urgently needed to provide more conclusive evidence.

Treatment options for apnoea of prematurity

Apnoea of prematurity (AOP) affects almost all infants born at <28 weeks gestation or with birth weight <1000 g. When untreated, AOP may be associated with negative outcomes. Because of these negative outcomes, effective treatment for AOP is an important part of optimising care of preterm infants. Standard treatment usually involves xanthine therapy and respiratory support. Cutting-edge work with stochastic vibrotactile stimulation and new pharmaceutical agents continues to expand therapeutic options. In this article, we review the pathophysiology of AOP, associated conditions and treatment options.

Long-Term Neurodevelopmental Outcome after Doxapram for Apnea of Prematurity

BACKGROUND

Doxapram has been advocated as a treatment for persistent apnea of prematurity (AOP).

OBJECTIVE

To evaluate the effect of doxapram on long-term neurodevelopmental outcome in preterm infants as its safety still needs to be established.

METHODS

From a retrospective cohort of preterm infants with a gestational age (GA) <30 weeks and/or a birth weight <1,250 g, born between 2000 and 2010, infants treated with doxapram (n = 142) and a nontreated control group were selected (n = 284). Patient characteristics and clinical and neurodevelopmental outcome data at 24 months' corrected age were collected. Neurodevelopmental delay (ND) was defined as having a Mental or Psychomotor Developmental Index (MDI/PDI) <-1 standard deviation (SD), cerebral palsy, or a hearing or visual impairment. Odds ratios (OR) were calculated using multiple logistic regression analyses adjusting for potential confounders.

RESULTS

Infants treated with doxapram had a lower GA compared to controls. The number of infants with a MDI or PDI <-1 SD was not different between the groups. The risk of the combined outcome death or ND was significantly lower in the doxapram group after adjusting for confounding factors (OR = 0.54, 95% CI: 0.37, 0.78). Doxapram-treated infants had a higher risk of bronchopulmonary dysplasia and patent ductus arteriosus, but a lower risk of spontaneous intestinal perforation. All other morbidities were not different between the groups.

CONCLUSIONS

This study suggests that doxapram is not associated with an increased risk of ND. These findings need to be confirmed or refuted by a large, well-designed, placebo-controlled randomized trial.

Amplitude-integrated electroencephalography shows mild delays in electrocortical activity in preterm infants born small for gestational age

AIM

Being born small for gestational age (SGA) seems to be a relevant risk factor for long-term neurologic deficits. We compared the differences between amplitude-integrated electroencephalography (aEEG) signals in very preterm infants born small for gestational age (SGA) and those in age-matched infants born appropriate size for gestational age (AGA).

METHODS

We performed serial aEEG recording on 305 infants: 255 (83.6%) were AGA, and 50 (16.3%) were SGA.

RESULTS

The number of bursts per hour decreased over time in both groups, but was higher in the SGA group at every time point. On day one, it was significantly higher in the SGA group (17.4) than in the AGA group (10.1) (p = 0.016). The total Burdjalov score increased with post-natal age and tended to be lower in SGA infants, but did not reach statistical significance at any time point. The percentage of continuous background patterns increased with post-natal age in both groups, with no significant difference between the groups.

CONCLUSION

Very preterm infants born SGA showed normal maturation of aEEG signals during post-natal life, but they also showed mild delays in electrocortical activity compared to age-matched AGA infants. The predictive value of these findings on neurodevelopmental outcome needs to be further evaluated.