Developmental maturation of gastro-oesophageal reflux in preterm infants

[Sleeping habits related to sudden infant death syndrome: a population-based study]

This cross-sectional study on sleeping habits with potential risk for sudden infant death syndrome included all live births in Passo Fundo, Rio Grande do Sul, Brazil, in 2003 with data collection from Certificates of Live Birth and interviews, analyzed with descriptive statistics and the chi-squared test. From the 2,634 live births, 2,285 children were selected (86.75%), with 8.4% exclusion and 5.2% losses. Protective habits included 77% of infants with appropriate clothing, 90% loosely wrapped, 69% with thin blankets, 98% sleeping in the parents' bedroom, and 56% in the crib. Potentially risky habits included lateral decubitus (92%), use of a pillow (88%), and feet far from the lower edge of the crib (96%). Among low-income families, bed-sharing with other children was significant (p = 0.00). Thus, in a county with a low prevalence of sudden infant death syndrome, infants are exposed to both protective and risk factors, suggesting that in underprivileged populations in developing countries, other risk factors for this syndrome should be considered.

Mechanisms of gastroesophageal reflux and gastroesophageal reflux disease

Gastroesophageal reflux is a physiological phenomenon, occurring with different severity and duration in different individuals. Reflux occurs when this normal event results in the occurrence of symptoms/signs or complications. The pathophysiology of gastroesophageal reflux is complex and diverse, since it is influenced by factors that are genetic, environmental (e.g., diet smoking), anatomic, hormonal, and neurogenic. However, many mechanisms remain incompletely understood. Future research should focus on a better understanding of the physiology of the upper and lower esophageal sphincters, and of gastric motility. The afferent and efferent neural pathways and neuropharmacologic mediators of transient lower esophageal sphincter relaxations and gastric dysmotility require further study. The role of anatomic malformations such as hiatal hernia in children has been underestimated. While therapeutic possibilities are greater in number and largely improved, the outcomes of some treatments are far from satisfactory in many cases. In addition to development of new forms of treatment, research should address better use of currently available medical and surgical treatments.

Gastroesophageal reflux in the neonate

Physiologic GER may be a maturational phenomenon, because infants outgrow this over time. Many aspects of GERD in neonates and young infants remain incompletely understood, however, particularly the pathophysiology and long-term problems in high-risk neonates. Diagnostic and therapeutic availability is vital in infants with GER and airway compromise, apnea events, or chronic lung disease. Although most infants improve with conservative therapy, there is a dire lack of ideal pharmacologic agents that work on all the mechanisms of GER with the least consequences. Studies that permit diagnosis not only of the disease but also of the causal mechanism, better feeding strategies, and prevention of morbidity from GERD will be beneficial.

Correlation of color Doppler sonographic findings with pH measurements in gastroesophageal reflux in children

PURPOSE

We conducted a prospective study of color Doppler sonography in children with suspected gastroesophageal reflux (GER). The purpose of this study was to compare the accuracy of color Doppler sonography with that of continuous 24-hour pH monitoring of the esophagus in diagnosing GER and to determine how to interpret the reflux episodes detected on color Doppler sonography in children at high risk for reflux.

METHODS

Color Doppler sonography and 24-hour esophageal pH monitoring were performed in 54 children ranging in age from 2 months to 10 years (mean, 3 years). The stomach of each patient was filled for adequate gastric distention just before the color Doppler sonographic examination. We counted the number of reflux episodes over a period of 15 minutes. One day after the sonographic examination, the reflux was evaluated with esophageal pH monitoring, and the resultant reflux index (ReI) was obtained. The ReI was considered to be pathologic when it was equal to or greater than 11.99%. The number of refluxes on color Doppler sonography and the ReI were correlated for each patient.

RESULTS

The 2 tests showed an 81.5% agreement in the detection of GER. When pH monitoring was taken as the reference test, color Doppler sonography had a high sensitivity (95.5%) for diagnosing GER but a very low specificity (11.0%), with a positive predictive value of 84.3% and a negative predictive value of 33.3%. There was no statistically significant correlation between the frequencies of GER detected on color Doppler sonography and the ReIs on pH monitoring (p = 0.1103). There was no correlation between the reflux grades on sonography and the ReI grades on pH monitoring (p = 0.422).

CONCLUSIONS

Color Doppler sonography is highly sensitive and easier to use than pH monitoring. Although there are no definite criteria for evaluating the severity of GER on color Doppler imaging, this modality may be useful in screening children for GER.

Cisapride decreases gastroesophageal reflux in preterm infants

OBJECTIVE

Gastrointestinal prokinetic agents, such as cisapride, are commonly used in pediatric practice to improve gastric emptying, to decrease emesis, to improve lower esophageal sphincter tone, and to improve irritability and feeding aversion associated with gastroesophageal reflux (GER). Although cisapride seems to be effective in infants from 2 months to 14 years old, data for younger and preterm infants are not available. Whether reflux is a significant cause of reflex apnea or feeding intolerance in the preterm infant is controversial. The objective of this 1-year prospective study, started in 1998, was to determine the efficacy of cisapride for treatment of reflux and reflux-associated apnea (RAAP) in preterm infants. Before this study, the diagnosis of reflux was often made clinically and the effect of therapy on reflux or the decision to increase the dose of cisapride was made empirically. The clinical bias was that persistent apnea, not responding to caffeine, was caused by GER. We reasoned that a systematic approach to the diagnosis and treatment of reflux would improve the care of preterm infants and reduce the risk of toxicity, especially if an increased dose of cisapride showed no improvement in reflux or apnea.

STUDY DESIGN

Twenty-four preterm infants (24-36 weeks' gestational age) had clinical apnea/pH studies when they were referred by the attending neonatologist for suspected GER. These infants were born at 28.8 +/- 3.1 weeks with birth weight of 1169 +/- 387 g (range: 631-2263 g). Each infant was studied before and 8 days after starting cisapride treatment. Cisapride dose was 0.09 to 0.25 mg/kg every 6 hours enterally. Treatment decisions regarding dose of cisapride were the responsibility of the attending neonatologist. The pH was recorded continuously for 24 hours at 0.25 Hz and was analyzed using EsopHogram software. A single sensor pH catheter was inserted to ~2 cm above the esophageal gastric junction. GER was defined as a drop in esophageal pH below 4.0 for a least 5 seconds, or pathologic GER was defined as a reflux index (RI) >2 standard deviation (SD) from the mean based on published norms for term infants. The following parameters were calculated from the pH recording: number of reflux events per 24 hours, duration of the longest episode, number of episodes >5 minutes per 24 hours, and RI, ie, percentage of time with pH <4.0. Each study had a combined time-lapse video recording and multichannel digital recording. Recorded parameters were: continuous pulse oximetry, electrocardiogram, respiratory effort (piezo sensor), and airflow (temperature sensor at nostrils and mouth). The recording was scored for central apneas of 10 to 14 seconds and >/=15 seconds (prolonged) and >/=10 seconds for obstructive and mixed apneas. RAAP was scored when an apnea (irrespective of the type) occurred within 1 minute of a GER event. Baseline, after cisapride, and follow-up electrocardiograms were performed because of concern about prolonged QTc and cardiac arrhythmias. The infants were 35.6 +/- 4.5 weeks postconceptional age when first studied. Twelve infants (mean birth weight: 1821 +/- 749 g; gestational age: 32 +/- 2 weeks; postconceptional age: 35.6 +/- 2.6 weeks) were identified retrospectively as controls because their baseline GER parameters were within the normal range using Vandenplas' criteria.

RESULTS

Overall, cisapride treatment significantly improved the RI from 16.6 +/- 15.2 to 9.1 +/- 8.4 SD. The number of reflux episodes >/=5 minutes was reduced from 7.1 +/- 5.8 to 4.3 +/- 4.4 SD. No significant effect was seen on the total number of refluxes (/24 hours). Eight infants (33%) had no decrease in the RI after a week of treatment. Three of these infants improved after cisapride dose was increased from 0.09 to 0.25 mg/kg/dose every 6 hours. Although 0.09 mg/kg/day is the minimum effective dose, 67% of our infants did respond to this low dose. Cisapride was discontinued in 3 infants because of prolonged QTc >/=0.450 seconds (0.473 in 1 and 0.470 in 2). More data about the effect of cisapride on QTc interval are reported in Pediatrics in a separate article. Only 1 infant showed no improvement with increased dose. Caffeine treatment had no effect on the baseline or follow-up GER values. Although apnea indexes for central and obstructive apnea were similar before and after cisapride, mixed apnea was less during treatment. There was a significant decrease (0.32 +/- 0.40 to 0.12 +/- 0.17/hour) in RAAP when the one infant who had increased reflux on increased dose of cisapride was excluded as an outlier. The statistical difference, before and after cisapride, for the group is significant with the outlier omitted. The clinical significance is unclear because ~50% of the infants had minimal changes in their apnea indexes. Furthermore, ~40% of infants did not have RAAP. (ABSTRACT TRUNCATED)

The role of swallowing during active sleep in the clearance of reflux in term and preterm infants

OBJECTIVES

To investigate swallowing and peristalsis in sleep and during gastroesophageal reflux (GER) in both healthy term and preterm infants at term equivalent age.

STUDY DESIGN

Multichannel recordings were made in 12 healthy term and 11 preterm infants, under the same conditions, after feeding. Sleep state, cardiorespiratory variables, esophageal pH, and pharyngeal swallowing and peristalsis were measured. GER was defined as pH <4 for > or = 15 seconds, and swallows were classified as pharyngeal only, primary peristalsis (propagated, dropped, interrupted), or secondary peristalsis.

RESULTS

Spontaneous swallowing rate was not significantly different between term and preterm infants and was sleep state-related, occurring in active sleep but rarely in quiet sleep. In response to acid GER, term infants significantly increased pharyngeal swallowing from a median of 0.7 (25th-75th interquartile range, 0.5-0.9) to 1.7 (1.0-3.0) swallows/min and secondary peristalsis from a median of 0.5 (25th-75th interquartile range, 0.3-0.8) to 1.1 (0.8-2.0) waves/min (P <.05). In contrast, the preterm infants demonstrated a significantly higher proportion of fully propagated peristaltic swallows compared with the term infants (53% and 27%, respectively) (P <.05).

CONCLUSION

The occurrence of swallowing is sleep state-related. In active sleep, term infants clear GER by increasing swallowing and secondary peristalsis, whereas preterm infants at term equivalent age clear GER by increasing propagated peristalsis. This method of clearance would explain the mechanism by which preterm infants have significantly shorter episodes of reflux than term infants.

The role of gastro-oesophageal reflux in the aetiology of SIDS

Gastro-oesophageal reflux (GOR) has been identified as a possible cause of SIDS. Several features of GOR unique to infants presenting with apparent life-threatening events (ALTEs) have led to its 'pathogenic' definition. One is that the life-threatening apnoea itself is initiated by GOR, another is that the ALTE relates to prolonged reflux during sleep, in a vulnerable sleep-state, and finally that the ALTE relates to excessive quantities of GOR. The presumption of GOR 'pathology' as a cause of SIDS however, is questionable in these susceptible infants for three reasons: firstly, GOR is physiological and occurs in most infants; secondly, there is no general consensus on what constitutes normal physiological reflux, and thirdly, variation in the recording technique and methods of data analysis and interpretation may account for the differences between study groups. It seems likely therefore if GOR is implicated in SIDS, additional factors are involved. Under certain circumstances, physiological GOR may trigger life-threatening apnoea in apparently healthy infants, that leads to SIDS. One mechanism that could explain such a death is reflex apnoea by stimulation of laryngeal chemoreceptors (LCR) during sleep. The conditions under which this could be fatal are the occurrence of gastric contents refluxed to the level of the pharynx during sleep, in the young infant who has depressed swallowing and arousal. That is, the occurrence of GOR to the level of the pharynx during sleep, an infrequent event that is usually innocuous, could be converted to a fatal event if swallowing is impaired and arousal depressed, by a variety of mediating factors such as prone sleeping, prematurity, sedatives, seizures or upper respiratory tract infections. The identification of LCR responses, particularly in prone sleeping and premature infants provide further evidence that this mechanism may be implicated in the aetiology of SIDS in apparently healthy infants.

Behavior and gastroesophageal reflux in the premature neonate

BACKGROUND

The belief that behavioral observations assist in the clinical diagnosis of gastroesophageal reflux (GER) disease in premature neonates has not been formally tested. The purpose of this study was to determine whether esophageal acidification was associated with a recognizable pattern of behavioral changes in these infants.

METHODS

The behavior of 14 healthy premature infants was recorded by a video camera while esophageal pH was simultaneously monitored. For each of 20 acid GER episodes recorded, a 10-minute video epoch, encompassing the onset of acid GER and lasting at least 4 minutes after the onset of GER, was examined. Two independent observers each scored reflux-associated epochs of "general" infant behavior and behavior previously shown to be indicative of reflux in normal term infants.

RESULTS

The occurrence of esophageal acidification due to reflux did not significantly alter scores for general behavior. Infants frequently demonstrated reflux-specific behavior, including discomfort, head retraction, and mouthing; however, none of these behavioral patterns was temporally associated with the occurrence of acid GER.

CONCLUSIONS

These data indicate that reflux-specific behavioral criteria, established in older term infants, may be inappropriate as diagnostic criteria for GER in premature neonates and may lead to the unnecessary use of antireflux therapy.

Lower esophageal sphincter position in premature infants cannot be correctly estimated with current formulas

OBJECTIVES

Strobel's formula (Esophageal length = 5 + 0.252 x Height) is frequently used as a guide for determining the distance from the nares to the lower esophageal sphincter (LES) in term infants. The aim of this study was to examine this relationship in premature infants.

STUDY DESIGN

The distance from nares to LES was manometrically determined in 156 premature infants (26-40 weeks' postmenstrual age; body weights of 610-3050 g). The ability of body weight, height (body length), head circumference, and postmenstrual age to predict the manometrically determined LES position was evaluated with linear and non-linear regression analyses.

RESULTS

Body weight and body length were the most predictive of distance from nares to LES (r(2) = 0.848 and 0.802, respectively). These relationships were non-linear and, in the case of body length, deviated substantially from Strobel's model.

CONCLUSIONS

In premature neonates, a different formula is needed for prediction of the distance between nares and LES than that applied to term infants and children.

Physiological studies of gastro-oesophageal reflux and airway protective responses in the young animal and human infant

1. The mechanisms that underlie the Sudden Infant Death Syndrome (SIDS) must explain its two unique features; age at death and death during apparent sleep. 2. The occurrence of gastro-oesophageal reflux (GOR) during active sleep in infants presenting with apparent life threatening episodes (ALTE) and their similar age distribution to SIDS infants, suggested that reflux could be a cause of asphyxia. 3. Sleep related GOR was found to be a physiological and not a pathological event in normal, healthy term infants. 4. In healthy term infants, those infants that were formula-fed (who have a higher incidence of SIDS) had significantly longer oesophageal clearance times for acid reflux and significantly more active sleep compared with breast fed infants. 5. In very preterm infants (who are at increased risk for SIDS), both the frequency and duration of reflux during active sleep was significantly less at term equivalent age compared with healthy term infants, suggesting additional factors must operate to promote an ALTE. 6. One mechanism which may explain the pathogenesis of GOR could be that the reflux reaches the level of the pharynx and this, in turn, stimulates laryngeal receptors to produce apnoea. 7. Simulated reflux to the level of the pharynx in the sleeping piglet evoked airway protective responses, namely swallow, arousal and occasionally expectoration, but neither apnoea nor oxygen desaturation. 8. In the same piglets treated with pentobarbitone sodium, swallowing was impaired and arousal depressed. Simulated reflux to the pharynx produced significant apnoea and oxygen desaturation and death in two of five piglets.(ABSTRACT TRUNCATED AT 250 WORDS)