Infant apnea and gastroesophageal reflux

Reflex cardiorespiratory events from esophageal origin are heightened by preterm birth

The involvement of gastroesophageal refluxes in cardiorespiratory events of preterm infants remains controversial. While a few studies in full-term newborn animals have shown that stimulation of esophageal receptors leads to cardiorespiratory reflexes, the latter remain largely unknown, especially after premature birth. The present study aimed to 1) characterize the cardiorespiratory reflexes originating from esophageal receptors in newborn lambs and 2) test the hypotheses that preterm birth enhances reflex cardiorespiratory inhibition and that C-fibers are involved in these reflexes. Eight full-term lambs and 10 lambs born 14 days prematurely were studied. Following surgical instrumentation, a 6-h polysomnography was performed without sedation to record electrocardiogram, respiratory movements, arterial pressure, laryngeal constrictor muscle activity, state of alertness, and hemoglobin oxygen saturation. Five esophageal stimulations of the upper and/or lower esophagus, including rapid balloon inflation and/or HCl injection, were performed in random order. A second recording was performed in full-term lambs 24 h later, after C-fiber blockade by capsaicin. Results confirmed that esophageal stimulations induced inhibitory cardiorespiratory reflexes combined with protective mechanisms, including laryngeal closure, swallowing, coughing, increased arterial pressure, and arousal. Preterm birth heightened cardiorespiratory inhibition. The strongest cardiorespiratory inhibition was observed following simultaneous stimulation of the lower and upper esophagus. Finally, cardiorespiratory inhibition was decreased after C-fiber blockade. In conclusion, esophageal stimulation induces inhibitory cardiorespiratory reflexes, which are partly mediated by C-fibers and more pronounced in preterm lambs. Clinical relevance of these findings requires further studies, especially in conditions associated with increased cardiorespiratory events, e.g., neonatal infection.NEW & NOTEWORTHY Preterm birth heightens the cardiorespiratory events triggered by esophageal stimulation. The most extensive cardiorespiratory events are induced by simultaneous stimulation of the proximal and distal esophagus.

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.

Upper airway reflexes in response to gastric reflux

Gastric reflux, and especially laryngopharyngeal reflux, occur several times a day in every infant. Most often, this does not pose any problem. However, in certain conditions, the contact between the refluxate and the upper airway mucosa can trigger several reflexes leading to cardiorespiratory inhibition. This is especially true for the laryngeal chemoreflexes, which are triggered by laryngeal penetration of gastric refluxate. The laryngeal chemoreflexes are held responsible for a subset of apnoeas of prematurity, many apparent life-threatening events, and probably some cases of sudden infant death syndrome. Although a number of experiments in newborn animals, as well as a few clinical studies in human infants, have been performed in the last 40 years to evaluate laryngeal chemoreflexes, their true role in neonatal cardiorespiratory events is still highly debated. In addition, many uncertainties persist with regard to treatment and prevention of their potentially dramatic consequences.

Apnea-associated reduction in lower esophageal sphincter tone in premature infants

OBJECTIVE

To characterize esophageal motility during episodes of prolonged apnea in premature infants.

STUDY DESIGN

We retrospectively reviewed combined manometric and physiological monitoring studies performed in tube-fed premature infants from 1994 to 2002. Apnea was defined as a respiratory pause of >20 seconds. For each apneic event, pharyngeal swallowing, esophageal motility, and lower esophageal sphincter (LES) pressure were assessed before, during, and after apneic episodes.

RESULTS

Twelve episodes of apnea (duration, 20 to 120 seconds) were identified in 7 infants (34 to 37 weeks postmenstrual age (PMA); study weight, 1950 to 2380 g). During the apneic episodes, swallowing increased (median[interquartile range], 0[0,0], 5[4,7], and 1[0,2] swallows/minute before, during, and after apnea, respectively; P < .05), esophageal pressure wave sequences (PWS) increased (1[0,2], 5[3,6], and 2[1,3] PWS/minute before, during, and after apnea, respectively; P < .05) and LES pressure decreased (16[12,21], 6[5,8], and 27[12,32] mmHg before, during, and after apnea, respectively; P < .05).

CONCLUSION

In premature infants, apnea is associated with reduced LES tone, potentially increasing the likelihood of reflux occurring after the onset of apnea.

Sonographic measurement of the abdominal esophagus length in infancy: a diagnostic tool for gastroesophageal reflux

OBJECTIVE

Our aim was to provide exact sonographic measurements of the abdominal esophagus length in neonates and infants with and without gastroesophageal reflux (GER) and to investigate its diagnostic value. GER severity and hiatal hernia presence were also evaluated and correlated with esophageal length.

MATERIALS AND METHODS

This retrospective case-control study comprised 258 neonates and infants (150 without reflux and 108 with reflux). There were 50 children without reflux in each of three age categories: less than 1 month, 1-6 months, and 6-12 months. Of the children with reflux, 42 were less than 1 month old; 34, 1-6 months; and 32, 6-12 months. The abdominal esophagus was measured from its entrance into the diaphragm to the base of gastric folds in fed infants. The number of refluxes during a 10-min period were recorded; GER was categorized as mild, one to three refluxes; moderate, three to six refluxes; and severe, more than six refluxes. Presence of hiatal hernia was recorded.

RESULTS

Neonates and infants with reflux had a significantly shorter abdominal esophagus than subjects without reflux: the mean difference in neonates, 4.8 mm; 1-6 months, 4.5 mm; 6-12 months, 3.4 mm. Children with severe reflux had a shorter esophagus compared with those with mild and moderate reflux only in the neonate group. In contrast, children with reflux associated with hiatal hernia had a significantly shorter esophagus compared with children with mild reflux in all three age groups. Sonographic sensitivity was 94%.

CONCLUSION

Sonographic measurement of the abdominal esophagus length is highly diagnostic for GER in neonates and infants. In neonates, it can also indicate GER severity. Hiatal hernia is associated with a significantly shorter abdominal esophagus.

Gastroesophageal reflux as cause of chronic respiratory symptoms

OBJECTIVE

Gastroesophageal reflux (GER) is a relatively common disorder in infants and children. It maybe associated with severe complications. The coexistence of GER and a wide range of respiratory symptoms has been reported. The purpose of our study was to investigate the relationship between chronic respiratory symptoms and GERD as an underlying cause. To our knowledge, there is not a method known study for identifying this relationship and prevalence in our area.

METHODS

The study group consists of fifty-two (4 months-10 years) children who were referred to pediatric surgery ward for evaluation of GERD as a cause of chronic respiratory symptoms by 24 hours PH monitoring. Additionally, 10 patients with only one episode of pneumonia were evaluated as the control group. Chronic respiratory presentations include the following: chronic cough, recurrent pneumonia, asthma, and respiratory distress.

RESULTS

24 hour esophageal PH monitoring revealed GER in 22 (42.2%) patients as a cause of their chronic respiratory symptoms, while (30 (57.7%) children did not show any evidence of GER. GER was detected in 11 of 24 (45.7%) patients with chronic cough. Thirty-three patients presented with recurrent pneumonia, 13 (39.9%) of whom had GER. In 8 patients with asthma, GER was found in 4 cases. None of the 6 patients with respiratory distress had GERD.

CONCLUSION

The possibility of GERD was significantly higher in study group (children with chronic respiratory symptoms) compared to control group (p-value<0.01). All patients with chronic cough, recurrent pneumonia and asthma should be aggressively investigated for the possibility of GER. Documenting abnormal gastroesophageal reflux helps direct appropriate therapy before occurrence of major complications.

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.

The relationship between gastroesophageal reflux and apnea in infants

OBJECTIVE

To determine the prevalence and relationship between apnea and gastroesophageal reflux (GER) among infants with apparent life-threatening events.

METHODS

We evaluated 67 infants of ages up to 6 months who had an idiopathic apparent life-threatening event as determined by polysomnography and pH monitoring.

RESULTS

No reflux (pH < 4 for more than 6 seconds) was evident in 32 infants. Fourteen others had such prolonged reflux that the relationship between apnea and reflux could not be evaluated. The 21 remaining infants who had episodes of apnea and reflux constituted the study group. In 81% of the apneic episodes, no relationship to GER was noted. Apnea preceded reflux in 93.6% of the episodes, and only 6.4% of the apneic episodes followed reflux. When apnea preceded reflux, the apnea was obstructive in 66.8% of episodes and mixed in 33.2%. Central apnea was not recorded preceding reflux.

CONCLUSIONS

Episodes of apnea were seldom associated with GER. However, in those instances when apnea and reflux were associated, the predominant sequence of events was obstructive apnea and to a lesser extent mixed apnea followed by reflux.

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.

Adverse effects of nicotine and interleukin-1beta on autoresuscitation after apnea in piglets: implications for sudden infant death syndrome

OBJECTIVES

Maternal cigarette smoking is established as a major dose-dependent risk factor for sudden infant death syndrome (SIDS). Both prenatal and postnatal exposures to constituents of tobacco smoke are associated with SIDS, but no mechanism of death attributable to nicotine has been found. Breastfeeding gives a substantial increase in absorbed nicotine compared with only environmental tobacco smoke when the mother smokes, because the milk:plasma concentration ratio of nicotine is 2.9 in smoking mothers. Furthermore, many SIDS victims have a slight infection and a triggered immune system before their death, thus experiencing a release of cytokines like interleukin-1beta (IL-1beta) that may depress respiration. Because apneas in infancy are associated with SIDS, we have tested the hypothesis that postnatal exposure to tobacco constituents and infections might adversely affect an infant's ability to cope with an apneic episode. This is performed by investigating the acute effects of nicotine and IL-1beta on apnea by laryngeal reflex stimulation and on the subsequent autoresuscitation.

DESIGN

Thirty 1-week-old piglets (+/-1 day) were sedated with azaperone. A tracheal and an arterial catheter were inserted during a short halothane anesthesia. The piglets were allowed a 30-minute stabilization period before baseline values were recorded and they were randomized to 4 pretreatment groups (avoiding siblings in the same group): 1) immediate infusion of 10 pmol IL-1beta intravenously/kg (IL-1beta group; n = 8); 2) slow infusion of 5 microg nicotine intravenously/kg 5 minutes later (NIC group; n = 8); 3) both IL-1beta and NIC combined (NIC + IL-1beta group; n = 6); or 4) placebo by infusion of 1 ml .9% NaCl (CTR group; n = 8). Fifteen minutes later, apnea was induced by insufflation of .1 ml of acidified saline (pH = 2) in the subglottic space 5 times with 5-minute intervals, and variables of respiration, heart rate, blood pressure, and blood gases were recorded.

RESULTS

Stimulation of the laryngeal chemoreflex by insufflation of acidified saline in the subglottic space produced apneas, primarily of central origin. This was followed by a decrease in heart rate, a fall in blood pressure, swallowing, occasional coughs, and finally autoresuscitation with gasping followed by rapid increase in heart rate, rise in blood pressure, and (in the CTR group) an increase of respiratory rate. Piglets pretreated with nicotine had more spontaneous apneas, and repeated spontaneous apneas caused an inability to perform a compensatory increase of the respiratory rate after induced apnea. This resulted in a lower SaO(2) than did CTR at 2 minutes after apnea (data shown as median [interquartile range]: 91% [91-94] vs 97% [94-98]). The pretreatment with IL-1beta caused prolonged apneas in piglets and an inability to hyperventilate causing a postapneic respiratory rate similar to the NIC. When nicotine and IL-1beta were combined, additive adverse effects on respiratory control and autoresuscitation compared with CTR were observed: NIC + IL-1beta had significantly more spontaneous apneas the last 5 minutes before induction of apnea (2 [.3-3] vs 0 [0-0]). Apneas were prolonged (46 seconds [39-51] vs 26 seconds [22-31]) and followed by far more spontaneous apneas the following 5 minutes (6.6 [4.0-7.9] vs.5 [.2- .9]). Instead of normal hyperventilation after apnea, a dramatic decrease in respiratory rate was seen (at 20 seconds: -45% [-28 to -53] vs +29% [+24-+50], and at 60 seconds: -27% [-23 to -32] vs +3% [-2-+6), leading to SaO(2) below 90% 3 minutes after end of apnea: 89% (87-93) versus 97% (95-98). These prolonged adverse effects on ventilation were reflected in lowered PaO(2), elevated PaCO(2) and lowered pH 2 minutes, and even 5 minutes, after induction of apnea.

CONCLUSIONS

Nicotine interferes with normal autoresuscitation after apnea when given in doses within the range of what the child of a smoking mother could receive through environmental t

Dual pH probe monitoring versus single pH probe monitoring in infants on milk feeds: the impact on diagnosis

OBJECTIVES

Oesophageal pH monitoring is the gold standard technique for the detection of gastro-oesophageal reflux in adults and children. A standard parameter used to define "abnormal" reflux is the percentage of recording time for which the gastric pH is < 4. This study investigated the relevance of this measure in infants on regular milk feeds whose gastric contents and refluxate will be neutral for most of the recording time.

METHODS

Simultaneous oesophageal and gastric pH monitoring was carried out on all infants who were milk fed exclusively and admitted to hospital for suspected gastro-oesophageal reflux. In vitro studies were performed to establish the buffering capacities of the fruit juice, Dioralyte (a glucose electrolyte solution), breast milk, and milk formula feeds available on the paediatric wards.

RESULTS

Complete sets of data were obtained from 30 babies with a mean age of 4 months. Gastric pH was </= 4 for a mean (SEM) of 42.4 (4.9)% of the recording time. The mean (SEM) percentage time that oesophageal pH was < 4 for the total recording period was 6.89 (0.92)%. Recalculation of the percentage of time that the gastric pH was > 4 increased this value to 17.81 (2. 46)%. Using a cut off point of 10%, 11 of the 30 babies would have been diagnosed positive for reflux using the conventional method; however, recalculation by ignoring the time for which gastric pH was high doubled this to 22 positive for reflux.

CONCLUSION

Combined oesophageal and gastric pH monitoring greatly increases the number of positive results from tests in infants on regular milk feeds.

Antireflux surgery in children under 3 months of age

PURPOSE

The aim of this study was to analyze the indications and results of fundoplication in 110 infants under 3 months of age.

METHODS

A retrospective review was conducted on the charts of all infants operated on for gastroesophageal reflux disease (GERD) at the UCLA Medical Center from January 1980 to December 1997. There were 59 boys and 51 girls. Recurrent emesis was the indication for operation in 62 of 110 infants, and respiratory symptoms in 85 of 110, with 54 of 110 having both. Neurological impairment was present in 32%. Prematurity was present in 21%; 35% had associated anomalies. Overall, 81 of 110 infants (73.6%) had one or more associated major malformations or disorders. Reflux was confirmed by upper gastrointestinal series findings in 63 of 78, esophageal pH monitoring in 60 of 62, and endoscopy in five of seven.

RESULTS

Mean age at operation was 1.8+/-0.1 months and mean weight was 3,686+/-90.2 g. A Nissen fundoplication was performed on 104 children, and six underwent a Thal procedure. Thirty-one had a gastric emptying procedure for delayed gastric emptying. Complications occurred in 7 infants. Emesis was controlled in 57 of 62 patients, aspiration in 38 of 48, and apneic spells in 54 of 57. Follow-up greater than 6 months was available for 73 patients. There were nine late deaths, all related to severe associated malformations. Seven patients required a redo fundoplication for recurrent reflux.

CONCLUSIONS

Nissen fundoplication can be performed safely in symptomatic infants under 3 months of age with low mortality and morbidity rates and with resolution of the presenting symptoms in 79% of infants.

Effects of promethazine on porcine gastroduodenal function: a sonographic study

This sonographic study was aimed at examining the effect of sedation with promethazine (1.5 mg x kg(-1)), on gastroduodenal function in neonatal piglets. On 3 consecutive days, observations of gastroduodenal motility during the first 3 postprandial h were made in 13 animals (3 to 5 days old; 7 sleeping naturally and 6 sedated 2 h prior to feeding). Promethazine significantly reduced both the closures per min of the terminal part of the pyloric antrum and pyloric canal and the percentage of gastric contractions that were followed by closure of the terminal pyloric antrum and canal. Such actions of promethazine on motility of the gastroduodenal junction could lead to a delay in gastric emptying of ingesta with a consequent increased risk of reflux of gastric contents into the esophagus. Because gastroesophageal reflux has been associated with the pathogenesis of sudden infant death syndrome (SIDS), care should be taken if promethazine is to be used as a sedative in neonates.

Ultrasound of the gastroesophageal junction

In 560 endoscopy examinations performed on infants with severe vomiting, no esophagitis was found without endoscopic herniation of the gastroesophageal junction. The length of the abdominal esophagus therefore appears fundamental in reflux studies. Sonography is one of few techniques able to define the abdominal esophagus in vivo, both in terms of its anatomy and as a functional structure. Accurate assessment of the sonographic canal requires careful measurement under strictly defined clinical conditions. Using such criteria, ultrasound has a better sensitivity than barium studies in detecting small herniations. In addition to the important length measurements of the abdominal esophagus, other morphological and functional data can also be acquired by ultrasound.