Does gastroesophageal reflux cause apnea in preterm infants?

The link between airway reflux and non-acid reflux in children: a review

OBJECTIVE

Airway reflux, a member of extra-esophageal reflux, has been linked to countless respiratory pathologies amongst children. The advent of novel instrumentation has enabled the discovery of non-acid reflux which was postulated as the main culprit of airway reflux. The objective of this review is to outline the association between non-acid reflux and airway reflux in children.

METHODS

A comprehensive review of recent literature on non-acid reflux and airway reflux in children was conducted. Studies ranged from January 2010 till November 2021 were searched over a period of a month: December 2021.

RESULTS

A total of eleven studies were identified. All studies included in this review revealed a strong link between non-acid reflux and airway reflux in children. 6 of the included studies are prospective studies, 3 retrospective studies, 1 cross-section study, and type of study was not mentioned in 1 study. The most common reported respiratory manifestation of non-acid reflux in children was chronic cough (7 studies). Predominant non-acid reflux was noted in 4 studies. The total number of children in each study ranges from 21 to 150 patients. MII-pH study was carried out in all studies included as a diagnostic tool for reflux investigation.

CONCLUSION

Non-acid reflux is the culprit behind airway reflux as well as other myriads of extra-esophageal manifestations in children. Multicentre international studies with a standardized protocol could improve scientific knowledge in managing non-acid reflux in airway reflux amongst children.

The epidemiology of apnoea of prematurity

WHAT IS KNOWN AND OBJECTIVE

Many premature infants less than 37 weeks gestational age (GA), and almost all infants less than 28 weeks GA, will experience apnoea of prematurity (AOP)-a cessation of respiration for 20 or more seconds (or less than 20 s if accompanied by other signs). Because the treatment options for AOP are so limited, we explore its epidemiology, with the ultimate hope of learning how to decrease its incidence.

COMMENT

Although AOP usually resolves with maturation of the respiratory system, many short- and long-term negative effects are correlated statistically with AOP (although direct causality has not been established). The primary risk factor for AOP is preterm birth, but delivery technique, genetics, socioeconomic status, racial disparities and other influences are suspected to be involved. Anaemia, asthma and gastric reflux have also been associated with preterm birth, but the relationship with AOP is unclear. The postulated associations and the strength of the evidence are briefly reviewed and discussed.

WHAT IS NEW AND CONCLUSION

Attempts to elucidate the epidemiology of apnoea of prematurity have been challenging. Studies of AOP are hampered in part by challenges in monitoring the condition, the interplay of multiple comorbidities in preterm neonates and lack of expert consensus definitions. However, since the primary risk factor is preterm birth, efforts to decrease the prevalence of preterm birth would have a positive secondary effect on the prevalence of AOP. Until then, better pharmacotherapeutic options are needed.

Apnea in preterm neonates: what's the role of gastroesophageal reflux? A systematic review

A causal relationship between gastro-esophageal reflux (GER) and apnea in preterm infants has been frequently hypothesized and is currently debated. The present study aims at reviewing the currently available scientific evidence, in order to clarify the role of GER on the occurrence of apnea and to help improving the clinical management of apneic preterm neonates. We performed a systematic literature search to identify all the clinical studies on preterm neonates that properly assessed the relationship between apnea and GER. Two-hundred and fifty-two papers, including 32 reviews and meta-analysis, were screened. Out of them, only 7 were included in the final analysis according to the selected criteria. Among them, 3 studies reported an increased frequency of apnea after reflux compared to reflux-free period and 4 denied a significant temporal relation. In conclusion, a minority of apneic events occurs soon after GER episodes. Whether this happens by chance or because of a causal relationship is still impossible to define. Based on the available data, empirical treatment with acid inhibitors is not recommended in neonates with apnea unless a proven temporal relation is shown by simultaneous esophageal pH-impedance and polysomnography or cardiorespiratory monitoring and in the absence of a clear clinical benefit.

Diagnostic Evaluation and Home Monitor Use in Late Preterm to Term Infants With Apnea, Bradycardia, and Desaturations

Apnea, bradycardia, and oxygen desaturation events are a common in neonatal intensive care units, with relevant literature to date largely focusing on very low birth weight and extremely low birth weight infants. We conducted a retrospective review of infants born at ≥34 weeks gestational age at 2 tertiary neonatal intensive care units in Boston, MA, between January 2009 and December 2013. Our objectives included (1) describing the diagnostic evaluations performed in late preterm to term infants with discharge-delaying apnea, bradycardia, or oxygen desaturation events and (2) identifying variables associated with home monitor use. Of the 741 eligible infants identified, diagnostic evaluations were variable and infrequent with blood culture, blood glucose, and head ultrasound performed most commonly. The likelihood of home monitor use was greater in infants with either a prolonged inpatient stay or greater gestational age at birth.

Evidence, Quality, and Waste: Solving the Value Equation in Neonatology

Rising health care costs challenge governments, payers, and providers in delivering health care services. Tremendous pressures result to deliver better quality care while simultaneously reducing costs. This has led to a wholesale re-examination of current practice methods, including explicit consideration of efficiency and waste. Traditionally, reductions in the costs of care have been considered as independent, and sometimes even antithetical, to the practice of high-quality, intensive medicine. However, it is evident that provision of evidence-based, locally relevant care can result in improved outcomes, lower resource utilization, and opportunities to reallocate resources. This is particularly relevant to the practice of neonatology. In the United States, 12% of the annual birth cohort is affected by preterm birth, and 3% is affected by congenital anomalies. Both of these conditions are associated with costly health care during, and often long after, the NICU admission. We will discuss how 3 drivers of clinical practice in neonatal care (evidence-based medicine, evidence-based economics, and quality improvement) can together optimize clinical and fiscal outcomes.

Oxygen saturation profile of term equivalent extreme preterm infants at discharge - comparison with healthy term counterparts

AIM

Compare the oxygen saturation profiles before discharge of neonates born extremely preterm (<28 weeks), now at term equivalent age, with healthy term neonates and assess the impact of feeding on this profile in each group.

METHODS

We prospectively evaluated and compared the oxygen saturation profile in 15 very low birthweight infants at term equivalent age, ready to be discharged home without any oxygen and 15 term newborns after 48 hours of life. We also evaluated and compared the saturations of these two groups during a one-hour period during and after feeding.

RESULTS

Term equivalent preterm and term infants spent median 3% and 0%, respectively, of the time below 90% in a 12-hour saturation-recording period. Term infants spent a median 0.26% and 0.65% of the time in <90% saturation during feed time and no feed time, respectively. In contrast, preterm infants spent significantly more time <90% saturation (3.47% and 3.5% during feed time and no feed time, respectively).

CONCLUSION

Term equivalent preterm infants spent significantly more time in a saturation range <90% compared to term infants. Feeding had little effect on saturation profile overall within each group.

Refluxo gastroesofágico e deglutição em recém nascidos e lactentes: revisão integrativa da literatura

Resumo: O refluxo gastroesofágico é encontrado em 25% dos bebês e pode acarretar vários prejuízos para o desenvolvimento. O objetivo deste trabalho foi realizar uma revisão integrativa da literatura buscando verificar se há publicações relacionando alterações da deglutição com o quadro de refluxo gastroesofágico em recém-nascidos e lactentes. A pesquisa foi realizada consultando os sites da Bireme e da PubMed. Os unitermos utilizados foram refluxo gastroesofágico, recém-nascido e lactente, em português e os correspondentes em inglês. Os descritores foram utilizados pareados, pois isolados abrangia muitos textos com temáticas diferentes da de interesse. Os trabalhos selecionados foram dos últimos dez anos. Não houve limite de tempo. De 1184 artigos da Bireme e 1600 da PubMed analisados a partir da aplicação dos critérios de inclusão e exclusão, restaram 23 artigos, sendo a maioria voltada aos sinais, sintomas e diagnóstico do RGE. Dois artigos abordaram o RGE e a deglutição, demonstrando que pode haver ou não relação entre RGE e disfagia orofaríngea em recém nascidos e lactentes, sendo que a escassez de pesquisas com essa temática demonstrou a necessidade de novos estudos abordando os aspectos patofisiológicos envolvidos.

Association between gastroesophageal reflux and pathologic apneas in infants: a systematic review

BACKGROUND

In infants, apneas can be centrally mediated, obstructive or both and have been proposed to be gastroesophageal reflux (GER) induced. Evidence for this possible association has never been systematically reviewed.

PURPOSE

To perform a systematic review using PubMed, EMBASE and Cochrane databases to determine whether an association between GER and apnea in infants exists. Studies with n ≥ 10 infants, aged <12 months, were included. GER had to be studied by pH-metry or pH-impedancemetry. GER episodes were defined as pH <4 for ≥ 5 s and/or a drop of >50% of baseline in impedance signal in distal channels. An apneic event was defined as a cessation of breathing for >20 s, or ≥ 10 s with hypoxemia or bradycardia. An epoch of ≤ 2 min was used to define temporal relation between GER and apnea. Methodological quality of studies was assessed with Newcastle Ottawa Scale (NOS). Of 1959 abstracts found, 6 articles met the inclusion criteria. All studies had poor methodological quality. A total of 289 infants were included. The temporal association of GER followed by apnea was assessed in all studies, with epochs varying from 10 s to 2 min. One study found an increase of apneic events after GER, the remaining 5 studies did not find an association. Two studies assessed apnea followed by GER as well, but did not find sufficient evidence for association. This systematic review showed insufficient evidence for an association between GER and apneas in infants. High quality studies using uniform inclusion criteria, definitions according to accepted guidelines, and patient relevant outcome measures are needed.

Non-nutritive sucking for gastro-oesophageal reflux disease in preterm and low birth weight infants

BACKGROUND

Gastro-oesophageal reflux (GOR) is commonly diagnosed in the neonatal population (DiPietro 1994), and generally causes few or no symptoms (Vandenplas 2009). Conversely, gastro-oesophageal reflux disease (GORD) refers to GOR that causes troublesome symptoms with or without complications such as damage to the oesophagus (Vandenplas 2009). Currently there is no evidence to support the range of measures recommended to help alleviate acid reflux experienced by infants. Non-nutritive sucking (NNS) has been used as an intervention to modulate neonatal state behaviours through its pacifying effects such as decrease infant fussiness and crying during feeds (Boiron 2007; Pickler 2004).

OBJECTIVES

To determine if NNS reduces GORD in preterm infants (less than 37 weeks' gestation) and low birth weight (less than 2500 g) infants, three months of age and less, with signs or symptoms suggestive of GORD, or infants with a diagnosis of GORD.

SEARCH METHODS

We performed computerised searches of the electronic databases of the Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 9, 2013), MEDLINE (1966 to September 2013), CINAHL (1982 to September 2013), and EMBASE (1988 to September 2013). We applied no language restrictions.

SELECTION CRITERIA

Controlled trials using random or quasi-random allocation of preterm infants (less than 37 weeks' gestation) and low birth weight (less than 2500 g) infants three months of age and less with signs or symptoms suggestive of GORD, or infants with a diagnosis of GORD. We included studies reported only by abstracts, and cluster and cross-over randomised trials.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed and selected trials from searches, assessed and rated study quality and extracted relevant data. We identified two studies from the initial search. After further review, we excluded both studies.

MAIN RESULTS

We identified no studies examining the effects of NNS for GORD in preterm and low birth weight infants

AUTHORS' CONCLUSIONS

There was insufficient evidence to determine the effectiveness of NNS for GORD. Adequately powered RCTs on the effect of NNS in preterm and low birth weight infants diagnosed with GORD are required.

Caffeine citrate: when and for how long. A literature review

The efficacy of caffeine in an episode of Apnoea of Prematurity (AOP) has been known for over thirty years. Its use over long periods of time has not only found it to be manageable within the field of neonatology, but it has also been found to have other favourable actions, such as reducing the incidence of extubation failure, preventing Bronchopulmonary Dysplasia (BPD), reducing the need for Patent Ductus Arteriosus treatment and the beneficial effect it has on Retinopathy of Prematurity. Recent in vitro trials have highlighted the neuroprotective role that caffeine plays, which has already partly been observed from in vivo trials. Just recently, caffeine citrate has become a "label" drug and it would be beneficial if more studies could confirm the more significant effects it has on the more severe conditions of prematurity.

Metoclopramide, H2 blockers, and proton pump inhibitors: pharmacotherapy for gastroesophageal reflux in neonates

Pharmacotherapy for gastroesophageal reflux (GER) in neonates, aimed at interfering with this physiologic process and potentially reducing the negative sequelae that providers often attribute to GER, consists primarily of drugs that increase the viscosity of feeds, reduce stomach acidity, or improve gut motility. Medications used to treat clinical signs thought to be from GER, such as apnea, bradycardia, or feeding intolerance, are among the most commonly prescribed medications in neonatal intensive care units in the United States, despite the lack of evidence of safety and efficacy in this population.

Myth: gastroesophageal reflux is a pathological entity in the preterm infant

There is concern about possible consequences of gastroesophageal reflux (GER) in preterm infants. GER is perceived to be a frequent condition in these infants, often causing an exhaustive investigation and expensive therapy. We review current evidence for and against an association between GER and apnea, failure to thrive, wheezing and respiratory diseases. Although there are some limitations to the methodologies currently used for detecting GER, there is clearly a lack of unequivocal evidence supporting a causal relationship between GER and its assumed consequences, particularly in preterm infants. Despite physiologic data that stimulation of laryngeal efferents by GER may induce apnea, there is little evidence for a causal relationship between GER and apnea. Studies on preterm infants with failure to thrive have also not demonstrated an association between the latter and GER in most cases, and there is equally little evidence for a casual relationship with respiratory problems. Therefore, we believe that GER in preterm infants is only rarely associated with serious consequences and existing evidence does not support the widespread use of anti-reflux medications for treatment of these signs in this age group. An improvement of methods to identify the few preterm infants at risk for developing serious consequences of GER is urgently needed.

Sensibilidade da seriografia do esôfago, estômago e duodeno para o diagnóstico de doença do refluxo gastroesofágico em recém-nascidos prematuros

OBJETIVO: Determinar a sensibilidade da seriografia do esôfago, estômago e duodeno (SEED) para o diagnóstico da doença do refluxo gastroesofágico (DRGE) em recém-nascidos prematuros, tendo como padrão ouro a monitoração prolongada do pH esofágico distal, e descrever a presença de anormalidades anatômicas do tubo digestivo. MATERIAIS E MÉTODOS: Foram incluídos no estudo 41 recém-nascidos, com média de 1.243,9 g, apresentando sinais/sintomas de DRGE e resultados alterados na monitoração do pH (índice de refluxo > 10%). A SEED foi realizada logo que as condições clínicas dos recém-nascidos foram estáveis para a realização dos exames radiológicos. RESULTADOS: A monitoração prolongada do pH e a SEED foram realizadas com 49,8 e 66,8 dias de vida, respectivamente. A sensibilidade da seriografia foi de 39,0% (IC 95%: 25,7–54,3%). Refluxo significativo foi observado em 41,4% dos casos, refluxo médio em 44,8% e refluxo pequeno em 13,8%. A SEED identificou apenas um caso de hérnia de hiato. CONCLUSÃO: A SEED apresentou baixa sensibilidade para a DRGE em prematuros e não se associou com a gravidade do refluxo, na comparação com a monitoração do pH, sendo, entretanto, útil no diagnóstico de alteração anatômica.

Characterization of cardiorespiratory events following gastroesophageal reflux in preterm infants

OBJECTIVE

The aim of this study was to characterize cardiorespiratory events in preterm infants after both acid and nonacid gastroesophageal reflux (GER) as detected by pH and multiple intraluminal impedance (MII).

STUDY DESIGN

Twelve hour overnight studies were performed in 71 preterm infants (gestational age 29.4±3.0 weeks, birth weight 1319±496 g). Apnea ≥10 s in duration, bradycardia ≤80 b.p.m. and oxygen desaturation ≤85% that occurred within 30 s after the initiation of GER were classified as associated with GER.

RESULT

A total of 12,957 cardiorespiratory events and 4164 GER episodes were documented. Less than 3% of all cardiorespiratory events were preceded by GER constituting 3.4% of apnea, 2.8% of oxygen desaturation and 2.9% of bradycardia events. GER did not prolong cardiorespiratory event duration or increase severity. In contrast, GER was associated with a shorter duration of oxygen desaturation events (7.8±4.6 vs 6.3±5.6 s, P<0.05).

CONCLUSION

GER is rarely associated with cardiorespiratory events, and has no detrimental effect on cardiorespiratory event duration or severity.

Clinical predictors of abnormal esophageal pH monitoring in preterm infants

BACKGROUND

Risk factors for gastroesophageal reflux disease in preterm neonates have not been yet clearly defined.

AIM

To identify factors associated with increased esophageal acid exposition in preterm infants during the stay in the neonatal unit.

METHODS

A case-control study in preterm infants who had undergone prolonged monitoring of distal esophageal pH, following clinical indication. Eighty-seven preterms with reflux index (percentage of total time of esophageal pHmetry) > or = 10% (cases) and 87 unpaired preterms were selected with reflux index <10% (controls). Demographic variables, signs and symptoms, main diagnoses and some aspects of treatment were studied. Simple and multiple logistic regression analysis adjusted for birthweight and postconceptional age at the pH study were used.

RESULTS

The factors associated with a greater chance of reflux index > or = 10% in preterms were: vomiting, regurgitation, Apnea, female gender. The variables that were associated with a lower frequency of increased reflux index were: volume of enteral intake at the onset of symptoms > or = 147 mL/kg/day, and postnatal corticoid use.

CONCLUSIONS

Vomiting, regurgitation, apnea, female gender and acute respiratory distress during the first week of life were variables predictive of increased esophageal acid exposition in preterm infants with birthweight <2000 g. Bronchopulmonary dysplasia and use of caffeine were not associated with reflux index > or = 10%.

Transpyloric tube feeding in very low birthweight infants with suspected gastroesophageal reflux: impact on apnea and bradycardia

OBJECTIVE

Our aim was to assess the safety and efficacy of transpyloric tube feeding as a therapeutic option to reduce apnea and bradycardia in hospitalized very low birthweight (VLBW) infants with clinical signs suggestive of gastroesophageal reflux (GER).

STUDY DESIGN

This was a retrospective single-center cohort study of VLBW infants hospitalized from 2001 to 2004 with signs of GER who received transpyloric enteral tube feedings. Apnea (>10 s) and bradycardia (<100 bpm) episodes were compared before and after the initiation of transpyloric feedings. The Wilcoxon signed-rank test was used to compare differences between cardiorespiratory episodes before and after treatment at 1-day and combined 3-day intervals. Events recorded to assess the safety of transpyloric feedings included death, sepsis and necrotizing enterocolitis (NEC).

RESULTS

A total of 72 VLBW infants with a median birthweight of 870 g (ranging from 365 to 1435 g) and gestational age of 26 weeks (from 23 to 31 weeks) were identified. The median weight at initiation of transpyloric feedings was 1297 g (from 820 to 3145 g) and infants received transpyloric feeds for a median duration of 18 days (from 1 to 86 days). After the initiation of transpyloric feedings, a reduction in apnea episodes from 4.0 to 2.5 (P=0.02) and a decrease in bradycardia episodes from 7.2 to 4.5 (P<0.001) was observed when comparing the total number of episodes for the 3 days before and after treatment. Five (6.9%) of the infants developed NEC while receiving transpyloric feedings. None of the infants receiving human milk (P=0.07) and 36% of those receiving hydrolysate-based formula (P<0.01) during transpyloric feeds developed NEC. No infants had late-onset culture-proven sepsis. Seven (9.7%) infants died before hospital discharge.

CONCLUSIONS

Transpyloric feedings, especially when limited to human milk, may safely reduce episodes of apnea and bradycardia in preterm infants with suspected GER. Prospective randomized studies are needed to determine the biological impact of bypassing the stomach, as well as the safety and efficacy of this intervention. The results of such studies could modify the current prevailing safety concerns regarding transpyloric feeding in this population.

A global, evidence-based consensus on the definition of gastroesophageal reflux disease in the pediatric population

OBJECTIVES

To develop an international consensus on the definition of gastroesophageal reflux disease (GERD) in the pediatric population.

METHODS

Using the Delphi process, a set of statements was developed and voted on by an international panel of eight pediatric gastroenterologists. Statements were based on systematic literature searches using Medline, EMBASE, and CINAHL. Voting was conducted using a six-point scale, with consensus defined, a priori, as agreed by 75% of the group. The strength of each statement was assessed using the GRADE system.

RESULTS

There were four rounds of voting. In the final vote, consensus was reached on 98% of the 59 statements. In this vote, 95% of the statements were accepted by seven of eight voters. Consensus items of particular note were: (i) GERD is present when reflux of gastric contents causes troublesome symptoms and/or complications, but this definition is complicated by unreliable reporting of symptoms in children under the age of approximately 8 years; (ii) histology has limited use in establishing or excluding a diagnosis of GERD; its primary role is to exclude other conditions; (iii) Barrett's esophagus should be defined as esophageal metaplasia that is intestinal metaplasia positive or negative; and (iv) extraesophageal conditions may be associated with GERD, but for most of these conditions causality remains to be established.

CONCLUSIONS

The consensus statements that comprise the Definition of GERD in the Pediatric Population were developed through a rigorous process. These statements are intended to be used for the development of future clinical practice guidelines and as a basis for clinical trials.

Differential diagnosis of apneas in preterm infants

Clinically relevant apneas, which are common in preterm infants, may adversely affect later neuropsychological condition in this group of patients. Pharmacotherapy to stimulate respiratory functions may be unsuccessful. Polygraphic recording may help in the differential diagnosis of these clinically relevant events. Twenty-nine preterm neonates born before 36 weeks of gestational age were examined using polygraphic recording (respiration--two channels, perioral electromyography, oxygen saturation, heart rate, electroencephalography, electrocardiography, electrooculography). The examination was ordered by the attending physician after an unsuccessful treatment of apnea by Aminophylline, and it should contribute to the clarification of the causes of these events. In the course of the polygraphic examinations, altogether 63 episodes were recorded during which the pulse oximeter alarm signal was set off. In 42 cases, the alarm signal was set off in events during which SaO(2) fell below 85%. In the remaining 21 cases, the alarm signal was set off in episodes during which early bradycardia below 90/min occurred. The onset of apnea was very often associated with the phasic increase of the perioral electromyography and with electroencephalography arousal reaction. Because of suspicion that these apneas may be triggered by episodes of gastroesophageal reflux, the interruption of the Aminophylline treatment and setting up an antireflux regimen were recommended. These therapeutic measures had a positive effect: The frequency of alarm signals decreased within 48 h by a statistically significant 50%. In cases where the pharmacotherapy of apnea by stimulation of respiratory functions is not successful, differential diagnostic analysis should be performed. Polygraphy may contribute to the clarification of the causes underlying clinically relevant apneas in a view of newly described polygraphic signs. It is feasible to suspect, based on these signs, that gastroesophageal reflux is the cause for clinically significant apneas in that case.

Use of medications for gastroesophageal reflux at discharge among extremely low birth weight infants

OBJECTIVES

Our goals were (1) to determine the use of medications to treat gastroesophageal reflux in extremely low birth weight infants (birth weight of < 1000 g) at discharge; (2) to identify risk factors associated with the use of medications to treat gastroesophageal reflux at discharge; and (3) to assess the contribution of gastroesophageal reflux medication use at discharge to growth and development at corrected ages of 18 to 22 months.

METHODS

This retrospective cohort analysis included extremely low birth weight infants enrolled at National Institute of Child Health and Human Development Neonatal Research Network Centers between 2002 and 2003 who survived to follow-up evaluations at corrected ages of 18 to 22 months. Analyses were used to identify factors associated with discharge with antireflux medications and poor growth or neurodevelopmental impairment after discharge.

RESULTS

A total of 1598 infants were included in the analyses; 24.8% were discharged from the hospital with medications to treat gastroesophageal reflux. A total of 19.3% of the 1287 infants discharged at postmenstrual age of < or = 42 weeks were discharged with antireflux medications. For those infants, center, lower gestational age, and race had significant effects on the use of antireflux medications at discharge. A total of 47.6% of the 311 infants discharged at postmenstrual age of > 42 weeks were discharged with antireflux medications. For those infants, no tested variables were associated with treatment with antireflux medications at discharge. Use of antireflux medications at discharge was not associated with either poor growth or neurodevelopmental impairment at corrected ages of 18 to 22 months.

CONCLUSIONS

Use of antireflux medications at the time of discharge seems to be common for extremely low birth weight infants, especially those discharged at postmenstrual age of > 42 weeks, but does not seem to have effects on growth or development at the time of follow-up evaluations.

Laryngeal sensitivity in the neonatal period: from bench to bedside

Laryngeal sensitivity in the newborn has been a subject of great interest for both researchers and clinicians for a number of years. From a clinical standpoint, laryngeal sensitivity is essential for both preventing foreign substances from entering into the lower airway and for finely tuning upper airway resistance. However, heightened reflexes originating from the laryngeal receptors in newborns and infants, due to neural immaturity, can lead to potentially dangerous cardiorespiratory events. The latter have been linked to apneas of prematurity, apparent life-threatening events, and sudden infant death syndrome (SIDS). From a physiological standpoint, many mechanisms pertaining to reflexes originating from laryngeal receptors are yet to be fully understood. This short review is an attempt to summarize current knowledge on laryngeal sensitivity and its potential consequences upon control of breathing abnormalities encountered within the first weeks of life.

Multichannel intraluminal impedance to detect relationship between gastroesophageal reflux and apnoea of prematurity

BACKGROUND

The association between gastroesophageal reflux and apnoea of prematurity is still controversial. Available data are biased by the heterogeneity of the infants enrolled as regard to some confounding factors and by the use of the traditional pH monitoring that is unable to detect non acid reflux events which might be prevalent in infants receiving frequent milk feeding. Multichannel intraluminal impedance has been recently introduced as a pH-independent method to investigate the bolus transport in hollow organs.

OBJECTIVE

To assess if combined multichannel intraluminal impedance-pH study could be useful to detect an association between gastroesophageal reflux and apnoea of prematurity.

METHODS

We prospectively evaluated a group of premature infants with apnoea of prematurity in absence of any confounding factors (ventilatory support, treatment with caffeine, permanent nasogastric tube, post-natal age older than 30 days) by simultaneous recording of 24-h multichannel intraluminal impedance-pH and cardiorespiratory monitoring. A temporal relationship between an apnoea and a reflux event was considered if both commenced within 20s of each other.

RESULTS

Six premature infants [three male; median gestational age 31 weeks (range 27-36); birth weight 1335g (range 1200-2350); age at study 17 days (range 7-28)] were studied. A total of 405 reflux events [306 (76%) weakly acid and 99 acid reflux] and 142 apnoeas were detected. The frequency of apnoeas occurring during the reflux events period was significantly greater than the one calculated for reflux-free period [0.42/min (0.00-1.28) versus 0.016/min (0.003-0.028); p<0.05]. The sub-analysis based on chemical composition and duration of refluxate showed that the frequency of apnoeas associated with weakly acid reflux events was significantly greater than the one calculated for reflux-free period [0.416/min (0.00-1.30) versus 0.016/min (0.003-0.028), respectively; p<0.05] and that the frequency of apnoeas occurring during reflux events longer than 30s was significantly higher than those occurring during shorter reflux events (22% versus 11%; p<0.004).

CONCLUSION

Our data show that weakly acidic reflux events are more prevalent than acid reflux events in premature infants, confirming the need for the use of multichannel intraluminal impedance-pH monitoring for diagnosis of gastroesophageal reflux in those patients. Gastroesophageal reflux and apnoea of prematurity are both common occurrences and, in our experience, may be temporally related especially as regard to weakly acid refluxate and reflux events longer than 30s.

Twenty-four-hour esophageal impedance-pH monitoring in healthy preterm neonates: rate and characteristics of acid, weakly acidic, and weakly alkaline gastroesophageal reflux

OBJECTIVE

Gastroesophageal reflux is a physiologic process and is considered pathologic (gastroesophageal reflux disease) when it causes symptoms or results in complications. It is common in preterm infants and occurs in healthy neonates. Twenty-four-hour pH monitoring commonly is used in children for diagnosis of gastroesophageal reflux disease, and abnormal reflux is considered with detection of increased esophageal acid exposure. However, in neonates, relatively few gastroesophageal reflux episodes cause esophageal acidification to pH < 4. Premature infants receive frequent feeds, which can induce a weaker acid secretory response than that observed in older infants and adults. As a consequence, gastric pH may be > 4 for prolonged periods, and reflux of gastric contents might be less acidic or even alkaline. Esophageal impedance monitoring can detect weakly acidic and even alkaline gastroesophageal reflux. The role of weakly acidic reflux in the pathophysiology of gastroesophageal reflux disease in preterm infants is not clear. To date, studies that have used impedance-pH in neonates assessed the association between nonacid reflux and cardiorespiratory symptoms, but no impedance data from healthy preterm neonates have been available to determine whether those symptomatic neonates had an increased number of weakly acidic reflux episodes or increased reactivity to a physiologic number of reflux events. Our aim with this study was to provide impedance-pH values for acid, weakly acidic, and weakly alkaline reflux from healthy preterm neonates.

METHODS

Esophageal impedance was recorded for 24 hours in 21 asymptomatic preterm neonates by replacing the conventional feeding tube with a specially designed feeding tube that included 9 impedance electrodes (8 French). All neonates were asymptomatic, with spontaneous breathing. Reflux monitoring was performed after comprehensive explanation and on receipt of written parental consent. Esophageal and gastric pH were monitored using a separate parallel pediatric catheter (6 French). According to the corresponding pH change, impedance-detected reflux was classified as acid, weakly acidic, and weakly alkaline. For each infant, the total number of reflux events, the acid exposure and bolus exposure times at 2 cm above the respiratory inversion point, and average proximal extent of reflux were calculated.

RESULTS

Twenty-six preterm neonates were recruited into this study. A preliminary analysis was performed, and tracings were classified according to their quality and the presence of technical artifacts (spontaneous pH and impedance drifts, esophageal probe migration, and dysfunction of 1 or more impedance channels). Five studies were excluded because of 1 or more technical artifacts; a total of 21 neonates represent the final cohort included. At birth, the infants had a median postmenstrual age of 32 weeks, and the measurements were performed at a median age of 12 days. The total recording time was 23.7 +/- 2 hours. Gastric pH was higher than 4 during 69.3 +/- 20.4% of the recording time. The median number of reflux events in 24 hours was 71, 25.4% (range: 0%-53.1%) of which were acid, 72.9% (range: 45.3%-98.0%) were weakly acidic, and 0% (range: 0%-8.1%) were weakly alkaline. Compared with fasting periods, feeding periods tended to be associated with a higher number of total reflux events per hour. The acidity of reflux, however, was significantly different: during fasting, the number of acid reflux episodes per hour was higher, whereas during feeding, the number of weakly acidic reflux episodes was increased. Most reflux events were only liquid, whereas gas was present either mixed with liquid or pure only in 7.7% of all reflux episodes detected. The proximal esophageal segments were reached in 90% of reflux episodes. Reflux-related acid exposure (pH drops associated with impedance-detected reflux) was 1.66% (range: 0%-6.43%), whereas total acid exposure (associated and not associated with reflux detected by impedance) was 5.59% (range: 0.04%-20.69%). There was no relationship between the number or acidity of reflux events and anthropometric parameters such as weight and gestational age.

CONCLUSIONS

We present the first study using 24-hour impedance-pH recordings in asymptomatic premature neonates. Previous studies that used pH-metry suggested that neonatal cardiorespiratory symptoms could be related to acid gastroesophageal reflux. However, pH-metry could not detect accurately weakly acidic or nonacid reflux. Our healthy premature neonates had approximately 70 reflux events in 24 hours, 25% of which were acid, 73% were weakly acidic, and 2% were weakly alkaline. The number of reflux events per hour (2-3 per hour) was slightly lower than that described in premature neonates with cardiorespiratory events (4 per hour). We confirmed that weakly acidic reflux is more prevalent than acid reflux, particularly so during the feeding periods. In contrast, similar to healthy adults, weakly alkaline reflux was very rare. We confirmed findings from previous studies in which most reflux events were pure liquid during both fasting and during postprandial periods and gas reflux was very rare. As in neonates with cardiorespiratory symptoms, the majority of reflux events in asymptomatic preterms reached the proximal esophagus or pharynx, and there were no differences between acid and weakly acidic reflux. The lack of differences between asymptomatic and diseased infants contravenes the hypothesis for macro- or microaspiration but does not exclude hypersensitivity to reflux as a cause for respiratory symptoms. The acid exposure that was related to reflux events and detected by impedance was significantly lower than the total acid exposure during 24 hours. Increased acid exposure could be attributable to pH-only reflux events or, less frequently, to slow drifts of pH from baselines at approximately 5 to values < 4. These changes were not accompanied by a typical impedance pattern of reflux but by slow drifts in impedance in 1 or 2 channels. Our findings confirm the need for the use of impedance together with pH-metry for diagnosis of all gastroesophageal reflux events. The relationship between gastroesophageal reflux and cardiorespiratory events in neonates and older infants has been studied extensively. The current evidence for such a relationship is controversial. This study provides values of impedance-pH monitoring for acid, weakly acidic, and weakly alkaline reflux from healthy preterm neonates that can be used for comparison when evaluating gastroesophageal reflux in preterm infants with a cardiorespiratory disease.

Metoclopramide for the treatment of gastroesophageal reflux disease in infants: a systematic review

OBJECTIVES

Metoclopramide is a commonly used drug to treat gastroesophageal reflux disease in infants. Given its widespread use and growing concern about toxicity in this population, we conducted a systematic review of metoclopramide for the treatment of gastroesophageal reflux disease in infants.

METHODS

We performed a systematic search of PubMed and bibliographies of relevant review articles. We included cohort, case-control, and intervention studies of the efficacy, effectiveness, or toxicity of metoclopramide therapy for gastroesophageal reflux disease in infants. We excluded case reports, case series, review articles, and abstracts.

RESULTS

Twelve articles met our inclusion criteria. Of these, 11 were prospective trials, and 5 were randomized, blinded clinical trials. Study size ranged from 6 to 77 patients. Eight studies showed patient improvement with metoclopramide in at least 1 measured outcome; 1 study showed worsening symptoms with metoclopramide. Of the 5 randomized, blinded trials, 2 showed no effect of metoclopramide on any outcome, and 2 showed a significant placebo effect. Four studies commented on adverse effects of therapy, with irritability being the most frequently reported potential adverse effect of therapy. Other reported adverse effects included dystonic reactions, drowsiness, oculogyric crisis, emesis, and apnea. Among studies, there was marked heterogeneity in the patient populations, dosing, and outcomes studied. Therefore, a meta-analysis was not performed. We both agreed on a US Preventive Service Task Force rating of "poor" for the level of evidence, leading to an "inconclusive" recommendation for the safety and efficacy of metoclopramide in infants.

CONCLUSIONS

The current literature is insufficient to either support or oppose the use of metoclopramide for gastroesophageal reflux disease in infants. In the future, large blinded randomized clinical trials are needed to determine the efficacy and toxicity of metoclopramide in this population.

Gastrointestinal maturation and feeding

The intestine serves not only as a digestive absorptive organ, it is also one of the largest immune organs of the body, has a huge endocrine and exocrine role, and also encompasses neural tissue equivalent to that of the entire spinal cord. The microbial microenvironment also plays a critical role in development. This brief overview of developmental aspects of these intestinal functions will be related to clinical problems in the neonatal period and subsequent health.

Control of Breathing and Neonatal Apnea

Great strides have been made in our understanding of developmental respiratory neurobiology. A clear picture is, therefore, emerging of the physiological mechanisms that underlie apnea of prematurity. The ventral surface of the medulla and adjacent areas play a key integrative function for central CO2 chemosensitivity and modulation of afferent inputs from peripheral chemoreceptors and laryngeal afferents. Maturational change in medullary neurotransmitter function appears to contribute to the physiological events that characterize apnea of prematurity. Despite this greater scientific insight, therapeutic strategies for neonatal apnea have changed little in 30 years. Xanthine therapy and continuous positive airway pressure remain the mainstay of therapy while other therapeutic approaches have been inadequately studied. Our understanding of a possible relationship between the triad of apnea, bradycardia and desaturation, and impaired neurodevelopmental outcome is also limited. These are all issues that need our attention if optimal therapy and outcome are to be provided for preterm infants with immature respiratory control.