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OBJECTIVE: Preterm infants are more likely to have episodes of abdominal distention, emesis, and gastric residuals 24 hours after their first screening examination for retinopathy of prematurity (ROP) than on the day preceding the examination. Because these feeding problems reflect abnormalities in motor function, the purpose of this study was to compare antral and duodenal motor activity and gastric emptying in preterm infants before and after the instillation of mydriatics. STUDY DESIGN: Using a low compliance continuous perfusion manometric system, we recorded antral and duodenal fasting motor activity in 11 preterm infants before and after the instillation of mydriatics for their first screening examination for ROP. Gastric emptying was compared before and after the eye examination. RESULTS: Although the number of antral motor contractions remained relatively constant throughout the study, duodenal motor contractions decreased nearly fourfold after the instillation of mydriatics versus that seen before (P <.01). Gastric emptying was significantly delayed after the completion of the eye examination compared with that seen before the examination (P <.05). CONCLUSION: Current doses of mydriatics inhibit duodenal motor activity and delay gastric emptying, and these gastrointestinal effects of mydriatics may underlie the feeding difficulties seen in preterm infants on the day of screening examinations for ROP.

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OBJECTIVE: Continuous perfusion manometry was performed in 93 preterm and 14 term infants, none of whom had ever been fed enterally, to determine whether duodenal motor responses to bolus feeding differ in preterm and term infants. STUDY DESIGN: Motor activity was recorded for 6 hours: 4 hours before and 2 hours after an intragastric feeding composed of Similac Special Care Formula, 5 ml/kg, infused for 15 minutes. RESULTS: Although 12 of 14 term infants had an increase in duodenal motor activity postprandially, similar to that seen in adults (i.e., a mature fed response), only 32 of the 93 preterm infants did (chi square statistic = 13.2; p < 0.001). In contrast to these infants, 2 term and 77 preterm infants had a decrease in duodenal motor activity (i.e., an immature fed response). There was a significant increase in the number of peaks per 30 minutes in the postprandial recordings of infants who demonstrated the "mature fed response" and a significant decrease in the number of peaks per 30 minutes in the postprandial recordings of infants who had an "immature fed response" (all p < 0.05). We then reevaluated motor responses to feeding among 41 of the preterm infants after they had received small enteral feedings of 24 ml/kg per day for 7 to 10 days. Although 11 of these infants had exhibited a mature response at the time of their initial study, 25 did at the time of the second study (p < 0.03). CONCLUSION: The duodenal motor response to bolus feeding differs in preterm and term infants; however, with enteral feeding experience, preterm infants begin to demonstrate more mature duodenal motor responses to feeding.

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To determine the response of the preterm infant's intestine to entire feedings at different postnatal ages, we recorded results of manometry of the gastroduodenum and determined fasting plasma concentrations of gastrin, gastric inhibitory peptide, neurotensin, and peptide YY three times in each of two groups: 27 preterm infants were randomly assigned to receive hypocaloric enteral nutrition on postnatal days 3 to 5 (early feeding) or on days 10 to 14 (late feeding). Initial observations (study 1) were performed by the fifth postnatal day; study 2 was performed on days 10 to 14, and study 3 on days 24 to 28. Early-fed infants received hypocaloric feedings immediately after study 1; late-fed infants did not receive enteral feedings until the completion of study 2. Although motor activity and fasting gastrointestinal peptide concentrations did not differ between groups at study 1, at study 2 early-fed infants had significantly more mature motor patterns than did babies not being fed. Early-fed infants also had significantly higher plasma concentrations of gastrin and gastric inhibitory peptide than did late-fed infants; neurotensin and peptide YY values were similar in both groups. By the time of study 3, when late-fed infants had also received enteral feedings, gut development was not different in the two groups. However, early-fed infants were able to tolerate full oral nutrition sooner, had fewer days of feeding intolerance, and had shorter hospital stays. Thus the provision of early hypocaloric nutrition was associated with earlier nutrition of preterm infants' intestinal function and resulted in improved feeding tolerance. These findings support the use of early feedings in preterm infants.

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To explore the possibility that the intestinal motor response to feeding is intact even in infants with immature fasting patterns, we performed low-compliance, continuous-infusion manometry in 13 term and 23 preterm infants during the first postnatal week. Babies were fed a standard formula intraduodenally at 4 ml/kg/2 hr by infusion pump. Small bowel motility responded to feeding; fasting patterns were replaced with long periods of persistent activity. During the infusion of formula, there was no significant difference in motor activity between preterm and term infants. Four characteristics of motor activity changed with feeding: motility index, the number of pressure peaks per 30-minute period, mean amplitude of pressure peaks, and duration of periods of quiescence. The number of pressure peaks per 30-minute period was the most sensitive index of the motor response to feeding, and it was used to characterize the fed pattern response. The start and duration of the fed response were similar in both groups of infants. Thus, despite the presence of immaturity in fasting patterns, the intestine of the preterm infant responds appropriately to feeding. These data help explain why preterm infants usually tolerate antral feedings, and support their use.

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Continuous perfusion manometry was performed in 31 preterm and term infants to assess the influence of gestational age on small intestinal motility. Gestational ages ranged from 27 to 42 weeks. All 8 term infants had interdigestive cycles that included all three phases. Only 4 of 23 preterm infants had complete interdigestive cycles. The remaining 19 preterm infants had only periods of motor quiescence and nonpropagating contractions. In term infants the interdigestive cycle was significantly shorter and the amplitude of phase 3 activity was significantly greater (p less than 0.01); velocity and duration of phase 3 activity were similar in both groups of infants. Rhythmic nonpropagating activity, or clusters, made up more than 60% of the phase 2 activity in both term and preterm infants. Although clusters did not propagate across three or more leads, approximately 25% of cluster activity was propagated across two leads. The duration of total cluster activity was similar for all gestational ages, but the frequency of clusters decreased and the mean duration of individual clusters increased with gestational age (both p less than 0.01). The amplitude of individual pressure peaks in clusters and phase 3 increased significantly with gestational age (p less than 0.03 and p less than 0.01, respectively). The motility index also increased with gestational age (p less than 0.02). We conclude that small intestinal motility is more immature in preterm infants than in term infants. Furthermore, cluster activity, which increases in duration and amplitude with gestational age, may be an immature form of phase 3 activity. These data and techniques will provide neonatologists with a direct way of tracking preterm intestinal motor function to provide more appropriate enteral nutrition.

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