Gastroesophageal reflux in preterm infants: norms for extended distal esophageal pH monitoring

Diagnosis of gastroesophageal reflux disease in infants

Gastroesophageal reflux is commonly encountered in the infant population. Most children will outgrow their reflux but some develop pervasive disease and require medical or surgical treatment. Many tools exist for use in the workup of pediatric gastroesophageal reflux disease; however, the most effective method of diagnosis is not clear. Delineating which patients will benefit from more definitive therapy is a remarkable challenge in this group, often borrowing tools and principles from the adult patient population. Therefore, we reviewed the available literature to critically evaluate the merits and limitations of the current diagnostic modalities available for the evaluation of infantile gastroesophageal reflux.

Anti-reflux surgery for the neonatal intensive care-dependent infant

AIM

The benefit of anti-reflux surgery for gastro-oesophageal reflux (GOR) in early infancy is uncertain. The aim of this study was to assess the value of Nissen fundoplication in a group of infants with severe GOR.

METHODS

10 infants underwent Nissen fundoplication for gastro-oesophageal reflux following a failure of medical management. All had suffered life-threatening respiratory episodes as a consequence of gastro-oesophageal reflux, and were neonatal intensive care-dependent. Median (range) birth weight was 1.26 kg (0.48-3.8 kg), gestation 30 weeks (25-38 weeks); at surgery, weight was 3.25 kg (2.5-6.1 kg) at a corrected age of 11.5 weeks (term-22) weeks. For each infant, the success of enteral feeding and the level of support required pre- and post-operatively was compared, and where appropriate, the facilitation of palliative feeding was assessed. Median follow-up was 14 (3-36) months.

RESULTS

No infant suffered intra-operative morbidity or mortality. One infant died within 1 month of surgery from a collapse unrelated to surgery. Eight of nine surviving infants were discharged from intensive care following extubation and the establishment of enteral feeding. One patient died of severe bronchopulmonary dysplasia 3 months post-surgery. One infant developed a gastrostomy site infection, and two required gastrostomy tube replacement within 6 months of surgery. All were thriving at follow-up. Two infants with a congenital myopathy died as a result of their muscle disease at 9 and 11 months post-operatively.

CONCLUSIONS

Nissen fundoplication is a feasible, effective and safe operation in severe gastro-oesophageal reflux unresponsive to medical treatment in term and pre-term infants. It has an additional important role in facilitating safe palliative enteral feeding in infants with a diagnosis incompatible with survival into adulthood.

Establishing enteral feeding in preterm infants with feeding intolerance: a randomized controlled study of low-dose erythromycin

OBJECTIVE

A prospective, double-blind, randomized, controlled trial was conducted to evaluate the effect of low-dose erythromycin on the time taken to attain full enteral feedings in preterm infants with very low birth weight and feeding intolerance.

METHODS

Two groups of preterm infants (birth weight </= 1500 g) with feeding intolerance were randomized to either low-dose erythromycin (5 mg/kg every 8 hours) or 5% dextrose placebo, both of which were discontinued 1 week after full enteral feedings were tolerated. The primary outcome variable was the time taken to attain full enteral feedings of at least 130 mL/kg/d.

RESULTS

The gestational age at birth was similar in the two groups (erythromycin, 27.1 +/- 1.9 weeks; placebo, 27.5 +/- 2.9 weeks). The mean birth weight of the erythromycin group was lower (806.3 +/- 215.6 g) than the placebo group (981.4 +/- 285.4 g; P = 0.18), and included more infants who were small for gestational age (4/13 = 31% versus 1/11 = 9%; P = 0.224). There was no difference between the two groups with regard to the volume of feedings they were receiving at the time of enrollment. Reduction in symptoms of gastroesophageal reflux was similar in the two groups. 3 of 13 in the erythromycin group and 4 of 11 in the placebo group improved during the study (P = 0.565). The mean time to attain full enteral feedings after enrollment was 24.9 + 2.9 days in the erythromycin group and 30.8 +/- 4.1 days in the placebo group, a difference that did not reach statistical significance (P = 0.17).

CONCLUSIONS

Low-dose erythromycin did not reduce the time taken to attain full enteral feedings in preterm infants with very low birth weight and feeding intolerance. Gastroesophageal reflux decreased as a consequence of maturation of the gastrointestinal tract and not because of erythromycin. These preliminary results justify verification in larger multicenter trials.

Apnea at discharge and gastro-esophageal reflux in the preterm infant

OBJECTIVE

To determine the relationship between respiratory patterns and acid gastro-esophageal reflux (g-e reflux) prior to discharge of the formerly preterm infant.

STUDY DESIGN

Forty-five infants of <32 weeks' gestation were studied at an average postmenstrual age of 37.2 weeks (SD 3.5). Following informed parental consent, a 12-hour multichannel recording including esophageal pH was obtained. Apneas of greater than 10 seconds were recorded, as well as the occurrence of bradycardia or desaturation.

RESULTS

Acid g-e reflux (pH <4.0) occurred at least once in all of the infants; prevalence was between <1% and 41% of the 12-hour record (median 4.6%, interquartile range 0.5% to 9%). The number of reflux episodes ranged from 1 to 143 (median 23). The number of apneas (>10 seconds duration) ranged from 0 to 71, median 6. There was no correlation between apnea frequency or severity and reflux frequency or duration. There was no difference in apnea frequencies between the 5 minutes after the start of a reflux episode and the 5 minutes prior to each episode.

CONCLUSION

Acid g-e reflux in the formerly preterm infant at discharge is frequent and may be prolonged; there is no association between reflux and apnea.

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)

Simultaneous monitoring of gastric and oesophageal pH reveals limitations of conventional oesophageal pH monitoring in milk fed infants

BACKGROUND

Monitoring oesophageal pH conventionally detects "acid reflux" (pH less than 4). The pH of the gastric contents determines whether or not reflux can be detected.

AIM

To monitor gastric and oesophageal pH simultaneously in order to determine the effect of milk feeds on gastric pH and how this would influence interpretation of the oesophageal pH record.

METHODS

Milk fed infants for whom oesophageal pH monitoring was requested underwent simultaneous gastric and oesophageal pH monitoring using a dual channel pH probe.

RESULTS

Twenty of 24 records were technically satisfactory. Mean reflux index was 1.0%, range 0.0-4.0%. Gastric pH was less than 4 for 24.5% (range 0.6-69.1%) of the total time. The average time the gastric pH was greater than 4 after feeds was 130 minutes (range 29-212 minutes). The corrected reflux index (limited to the time the gastric pH was less than 4) was 2.6% (range 0.0-11.0%).

CONCLUSION

The pH of the gastric contents may be greater than 4 for prolonged intervals, during which oesophageal pH monitoring using current criteria cannot detect reflux nor correlate it with clinical events. A low reflux index may reflect prolonged buffering of gastric acidity rather than the absence of reflux.

PH monitoring in the distal and proximal esophagus in symptomatic infants

BACKGROUND

Standard distal esophageal pH monitoring data are sometimes within normal ranges in children with clinically suspected gastroesophageal reflux disease. Therefore, the authors hypothesized that the amount of acid reflux reaching the proximal esophagus may be greater in some subgroups of patients than in healthy controls or in other subgroups of patients.

METHODS

The parameters of 24-hour pH monitoring in the proximal part of the esophagus were analyzed in 120 symptomatic infants in who the reflux parameters in the lower esophagus were clearly within normal ranges (reflux index < 5.0%). The infants were classified into four patient groups: excessive regurgitation (n = 41): inconsolable crying (n = 31), apparent life-threatening event (ALTE) (n = 18), and chronic respiratory disorders (n = 30). The control group consisted also of 120 infants. The following parameters were calculated: reflux index, the number of reflux episodes, the number of reflux episodes lasting longer than 5 minutes, the duration of the longest reflux episode, and the acid clearance time (ACT, duration of reflux episodes divided by number of reflux episodes).

RESULTS

The patients with chronic respiratory disorders were significantly older than the patients in the other groups and the controls. In the distal esophagus, there was no statistically significant difference between the reflux parameters. As could be expected, every parameter was statistically (paired t test, Wilcoxon signed-rank test) significantly smaller in the proximal than in the distal esophagus, except for the ACT in infants who presented with inconsolable crying. In the proximal esophagus, there was no statistically significant difference between the different patient subgroups or controls, except for the number of reflux episodes in the group with chronic respiratory disorders and the group with inconsolable crying, applying one-way analysis of variance. As determined by applying the Mann-Whitney test, the number of reflux episodes in the upper esophagus was significantly higher in the group with chronic respiratory disorders than in the other patient groups and controls. Therefore, the authors' data do not support the hypothesis that reflux reaching the proximal esophagus is a frequent cause of ALTE. However, the data may suggest that the number of reflux episodes reaching the proximal esophagus in children with chronic respiratory disorders and with distal pH monitoring data within normal ranges may be increased. Whether this finding reflects reality or a statistical coincidence, or is influenced by the older age of this patient group, needs further evaluation.

CONCLUSIONS

In theory, dual simultaneous esophageal pH monitoring in the distal and proximal esophagus may increase the diagnostic accuracy of pH monitoring in infants. Our results do not support a substantial advantage of a systematic application of this new technique, especially not in infants presenting with ALTE, excessive regurgitation, or inconsolable crying. In the subgroup of patients with chronic respiratory disorders, more data are needed before conclusions can be determined and recommendations can be made.

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.