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.     

Abbreviated oesophageal pH monitoring in infants

The results of 24 h oesophageal pH monitoring, performed in 129 infants aged 6–10 weeks, were compared to those in the same patients after shorter periods (3, 6, 9 and 12 h). In the investigated population there was no significant difference between the reflux index (percentage of time with a pH<4.0) after 12 or 24 h. Moreover, the correlation coefficient between the reflux index after 12 and 24 h was excellent (r0.95). However, the intra-individual difference in reflux index after 12 and 24 h was 5% in 19% of the infants, and even exceeded 10% in more than 5% of the infants, making the interpretation of the results unreliable. Even in this particular population of infants in whom a 24-h period could be divided into almost identical periods (including a feeding and a sleeping period), 24-h registrations provided the most reliable results. However, if for some reason the investigation had to be interrupted after a minimum of 12 h, the risk for erroneous interpretation of the data appeared to be acceptable. The results of this study must not be extrapolated to older children.     

Simultaneous tracheal and oesophageal pH monitoring during mechanical ventilation

OBJECTIVE: To simultaneously record tracheal and oesophageal pH in mechanically ventilated children to determine: (1) the feasibility and safety of the method; (2) the incidence of gastro-oesophageal reflux (GOR) and pulmonary contamination; and (3) their associated risk factors. DESIGN: Prospective study. SETTING: Paediatric intensive care unit in a university hospital. PATIENTS: Twenty mechanically ventilated children (mean age 6.7 years) who met the following inclusion criteria: endotracheal tube with an internal diameter of 4 mm or more (cuffed or uncuffed), mechanical ventilation for an acute disease, no treatment with antiacids, prokinetics, or H2-receptor blockers, and no nasogastric or orogastric tube. METHODS: The tracheal antimony pH probe was positioned 1 cm below the distal end of the endotracheal tube. The oesophageal antimony pH probe was positioned at the lower third of the oesophagus. pH was recorded on a double channel recorder and analysed with EsopHogram 5.01 software and by examination of the trace. The following definitions were used: GOR index, percentage of time pH < 4; pathological GOR, GOR index > 4.8%; tracheal reflux, fall in tracheal pH < 4, 4.5, or 5, or a decrease of one unit from baseline, in both cases preceded by an episode of GOR. The results were analysed statistically by Fisher's exact and the Kruskal-Wallis test. RESULTS: The procedure was well tolerated and the median duration of analysable recording was 6 hours (range 5-22.6). Pathological GOR was observed in eight (40%) children. GOR was more frequent with an uncuffed endotracheal tube than with a cuffed one (p = 0.01). Tracheal reflux (pH < 4) was observed in four children (20%) without clinical evidence of pulmonary aspiration. Episodes of tracheal reflux were associated with a GOR index > 10% (p < 0.01) and were more frequent with a maximal inspiratory pressure of < 25 cm H2O (p = 0.03), but were not related to the indication for mechanical ventilation, whether the endotracheal tube was cuffed or not, age, or drug treatment. CONCLUSIONS: Simultaneous tracheal and oesophageal pH monitoring was feasible in the setting of this study. Tracheal reflux can occur without pathological GOR, and GOR may occur without tracheal reflux. Further prospective studies in larger groups of patients are now justified.     

Simultaneous tracheal and oesophageal pH monitoring during mechanical ventilation.

OBJECTIVE: To simultaneously record tracheal and oesophageal pH in mechanically ventilated children to determine: (1) the feasibility and safety of the method; (2) the incidence of gastro-oesophageal reflux (GOR) and pulmonary contamination; and (3) their associated risk factors. DESIGN: Prospective study. SETTING: Paediatric intensive care unit in a university hospital. PATIENTS: Twenty mechanically ventilated children (mean age 6.7 years) who met the following inclusion criteria: endotracheal tube with an internal diameter of 4 mm or more (cuffed or uncuffed), mechanical ventilation for an acute disease, no treatment with antiacids, prokinetics, or H2-receptor blockers, and no nasogastric or orogastric tube. METHODS: The tracheal antimony pH probe was positioned 1 cm below the distal end of the endotracheal tube. The oesophageal antimony pH probe was positioned at the lower third of the oesophagus. pH was recorded on a double channel recorder and analysed with EsopHogram 5.01 software and by examination of the trace. The following definitions were used: GOR index, percentage of time pH < 4; pathological GOR, GOR index > 4.8%; tracheal reflux, fall in tracheal pH < 4, 4.5, or 5, or a decrease of one unit from baseline, in both cases preceded by an episode of GOR. The results were analysed statistically by Fisher''s exact and the Kruskal-Wallis test. RESULTS: The procedure was well tolerated and the median duration of analysable recording was 6 hours (range 5-22.6). Pathological GOR was observed in eight (40%) children. GOR was more frequent with an uncuffed endotracheal tube than with a cuffed one (p = 0.01). Tracheal reflux (pH < 4) was observed in four children (20%) without clinical evidence of pulmonary aspiration. Episodes of tracheal reflux were associated with a GOR index > 10% (p < 0.01) and were more frequent with a maximal inspiratory pressure of < 25 cm H2O (p = 0.03), but were not related to the indication for mechanical ventilation, whether the endotracheal tube was cuffed or not, age, or drug treatment. CONCLUSIONS: Simultaneous tracheal and oesophageal pH monitoring was feasible in the setting of this study. Tracheal reflux can occur without pathological GOR, and GOR may occur without tracheal reflux. Further prospective studies in larger groups of patients are now justified.     

Usefulness of oesophageal pH monitoring

Gastro-oesophageal reflux (GOR) is a common paediatric problem which usually in the past has been diagnosed clinically, perhaps backed up by the barium oesophagogram. In the past 10 years, there has been a proliferation of further diagnostic techniques for GOR, possibly reflecting the inability of any single test to make a definitive diagnosis. The justification for this explosion of tests and the need to make a definitive diagnosis is two fold. Firstly, we know that GOR can cause significant disabilities which are often difficult to diagnose or determine the cause of (e.g. recurrent respiratory disease and sudden infant death syndrome),¹ and secondly, an effective model of surgical therapy is now available.²     

Value of simultaneous monitoring of esophageal and gastric pH in infants

Simultaneous monitoring of esophageal and gastric pH in infants makes clear some peculiarities of digestive physiology and improves the sensibility of the simple method, usual mean of diagnosis of GER. In that way, a gastro-esophageal pH gradient is showed; gradient absolutely necessary to a good interpretation of this test. In twenty-two infants, younger than one year, continuous and extended monitoring of esophageal and gastric pH was realised with a specially-designed-combination microelectrode. Results pointed out that, after a meal, especially a milked meal, the post prandial period isn't suitable for the diagnosis of GER. Indeed, the gastric acidity is buffered, sometimes during many hours: that decreases or cancels the gastro-esophageal pH gradient. Besides, transient neutralisation periods of gastric acidity may occur, perhaps related with duodenogastric-biliary reflux. Before two months, the gastric pH is less acid that involves, one more time, on insufficient gastro-esophageal pH gradient for the diagnosis of GER.     

Effects of formula feeding on gastric acidity time and oesophageal pH monitoring data

Gastro-oesophageal reflux (GOR) occurs mainly during postcibal (PC) periods. The duration of PC gastric acidity and the incidence of GOR were analysed in 11 asymptomatic premature infants. GOR was studied during PC periods of 120 min and also during the following 120 min defined as fasting (FT) periods. These infants were subjected to simultaneous continuous gastric and oesophageal pH monitoring using a double-blind crossover technique. Two formulae with different fat contents (2.6 vs 3.6 g/100 ml) and different carbohydrate concentrations (8.1 vs 7.3 g/100 ml; malto-dextrin 2.8 vs 1.9 g/100 ml) were given. Gastric acidity (pH<4) in the PC periods lasted significantly (P<0.001) longer (68 min±10) with the low fat/high malto-dextrin formula versus 43 min±11 with the high fat/low malto-dextrin formula. Oesophageal pH monitoring data were within normal limits for the total investigation time in all infants. During PC periods acid GOR was detected more frequently in the group with a low fat formula. More PC GOR was recorded when the gastric acidity time was longer.Abbreviations F1 formula 1 - F2 formula 2 - FT fasting - GOR gastro-oesophageal reflux - PC postcibal     

The interpretation of oesophageal pH monitoring data

Continuous monitoring of oesophageal pH is regarded as the gold standard for all reflux investigations. However, since gastro-oesophageal reflux is considered a normal phenomenon which occurs to a certain extent in each individual, the distinction between normal and abnormal is not always obvious and is not possible to achieve with a single test. Moreover, data depend on technical hardware such as recording devices and electrodes together with such patient characteristics as age, position, activity, and medication. Although much literature on pH monitoring has appeared recently, many investigations have failed to take into account the basic principles that are of major importance for any biomedical test such as reproducibility, sample reliability, and indications. There is a need to standardize the technique in order to compare studies performed in different centres, provided the technique is reproducible.     

Nutrient intakes of formula-fed infants and infants fed cow's milk

Twenty-four-hour dietary intake data from the second National Health and Nutrition Examination Survey (NHANES II), 1976-1980, were analyzed to compare nutrient intakes among infants 7 to 12 months of age who were fed mixed diets containing solid foods and either infant formula or cow's milk. Solid foods fed to the infants in both groups were low in iron and linoleic acid, and high in sodium, potassium, and protein, relative to Recommended Dietary Allowances. Infants who were fed cow's milk received lower median intakes of iron (7.8 mg v 14.9 mg), linoleic acid (1.8 g v 6.1 g), and vitamin C (39 mg v 64 mg), and higher median intakes of protein (41 g v 25 g), sodium (1,000 mg v 580 mg), and potassium (1,630 mg v 1,020 mg) than formula-fed infants. Seventy-five percent of the infants fed cow's milk had iron intakes below the Recommended Dietary Allowance; 69% had sodium intakes above the range of estimated safe and adequate daily dietary intake. Linoleic acid provided less than 3% of energy intake for 74% of the infants fed cow's milk. Differences in nutrient intakes were due not only to different concentrations of nutrients in each of the milk feedings but also to the different amounts and types of solid foods fed to the two groups of infants.     

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 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.     

Food allergy in preterm infants fed human milk

In 80 preterms aged 9-24 months (mean age: 15.9) and in 80 sex- and age-matched full-terms the frequency of atopic diseases and of positive skin tests to 8 food and 6 inhalant allergens was determined. The two groups did not differ as to overall percentages of cutipositive subjects and patients with atopic diseases. In particular, frequencies of positive skin tests to foods and of atopic dermatitis (the peak prevalence of which occurs early in infancy) were similar in preterm (16.2 and 7.5%, respectively) and full-term (13.7 and 5.0%, respectively) infants. We suggest that preterm infants fed human milk are not at increased risk of developing food allergy and related diseases and that the absorption of antigens through the immature intestine does not seem to favor the development of an IgE sensitization to foods.     

Reproducibility of 24 hour oesophageal pH studies in infants.

Thirteen infants who had undergone 24 hour oesophageal pH monitoring to diagnose gastro-oesophageal reflux had a second study carried out to see if the results were reproducible. The studies were done without restricting the babies'' activities. Appreciable differences were found, the percentage of the total time during which the pH was less than 4 varying by up to 3.7-fold between the two tests. The differences were largely the result of biological rather than technical variability. From these results estimates were made of the reliability of a single diagnostic study and the size of changes that would be necessary to show the effect of treatment. These findings have a considerable impact on the diagnosis of abnormal gastro-oesophageal reflux and its response to treatment whether using 24 hour pH monitoring or any other method of measurement.     

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.
     

Feeding tolerance in premature infants fed fortified human milk

BACKGROUND: To evaluate feeding tolerance in premature infants immediately after the addition of human milk fortifier (HMF) to their expressed human milk diet. METHODS: Data on milk intake, feeding tolerance, and related assessments and growth milestones from a prospective study of feeding strategies in premature infants were analyzed. The database was searched for the first day HMF was added to the feeding of infants receiving human milk exclusively. The following assessments were tabulated for the 5 days before and the 5 days after the addition of HMF: milk intake, the number of episodes of abdominal distension, gastric residual volume (GRV) more than 2 ml/kg and more than 50% of the volume fed in the prior 3 hours. bile-stained gastric residual, emesis or regurgitation, blood in the stool, the number of abdominal radiographs, the number of episodes of apnea and bradycardia, changes in findings in the clinical examination, and the number of hours feeding was withheld. The time to achieve full tube feeding, complete oral feeding, and hospital discharge were recorded. RESULTS: Seventy-six exclusively human milk-fed premature infants (birth weight, 1065+/-18 g; gestational age, 27+/-0.1 weeks; mean +/- SEM) who received HMF beginning 22+/-0.8 days of age were evaluated. There were significant increases in milk intake and in the number of episodes of GRV more than 2 ml/kg and emesis after the addition of HMF. There were no differences in the number of hours feeding was withheld or any other assessment after the addition of HMF. Infants with increases in GRV more than 2 ml/kg and/or emesis after the addition of HMF were not more likely to be delayed in the time to achieve full tube feeding, complete oral feeding, or hospital discharge than infants who did not experience these events. CONCLUSION: These data suggest that, when all feeding and related assessments and the time to achieve important growth milestones are considered, the addition of HMF does not adversely affect the outcome of the premature infant.     

Lipoprotein changes in small-for-gestational-age infants fed nucleotide-supplemented milk formula

Morillas J, Moltó L, Robles R, Gil A, Sánchez-Pozo A. Lipoprotein changes in small-for-gestational-age infants fed nucleotide-supplemented milk formula. Acta Prediatr 1994;83:481–5. Stockholm. ISSN 0803–5253
We determined the effect of supplementing milk formula with nucleotides on plasma lipoproteins in small-for-gestational-age infants: 21 infants were fed a nucleotide-supplemented formula and 20 infants were fed the same nucleotide-free formula. On days 0, 3 and 7 after birth, major plasma lipoprotein fractions were analyzed for apolipoprotein and lipid composition. Compared with the control group, the group receiving nucleotides had increased total apoprotein concentrations in all lipoproteins as well as increased apo A-I in high-density lipoproteins and very low-density lipoproteins, and apo B-100 in very low-density lipoproteins and low-density lipoproteins. Very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol and very low-density lipoprotein triglycerides increased in parallel to the changes in apoproteins. The cholesterol ester to unesterified cholesterol ratio was increased in low-density lipoproteins and, particularly, in high-density lipoproteins. These data support the hypothesis that lipoprotein metabolism in small-for-gestational-age infants is affected by dietary nucleotide supplementation, enhancing lipoprotein synthesis or secretion. Cholesterol esterification capacity paralleled the apo A-I increase, in agreement with the co-factor role of apo A-I on lecithin: cholesterol acyltransferase.