Frontal horn thin walled cysts in preterm neonates are benign.

BACKGROUND: Screening cranial ultrasound led to the discovery of isolated frontal horn cysts quite distinct from periventricular leucomalacia cysts. AIM: To clarify their significance, incidence, characteristics, causal factors or aetiology, and effect on long term outcome. DESIGN: A retrospective observational study of all first cranial ultrasound scans (total of 2914) performed during the period 1984-1994 inclusive found 21 neonates with smooth thin walled frontal horn cysts: 18 of 2629 scanned were of birth weight < 1500 g or gestation < 33 weeks, and three of 285 were > 33 weeks gestation. Sequential ultrasound, maternal records, and neonatal events were retrospectively assessed. In survivors, routine neurodevelopmental evaluations were obtained. Postmortem studies of one cyst were performed to determine the nature and origin of these lesions. RESULTS: Of the 21 subjects, 15 had isolated frontal horn cysts and six had additional ultrasound scan abnormalities, including four with subependymal haemorrhage. The sonographic features of frontal horn cysts were of distinctive morphology (elliptical, smooth, thin walled, ranging in size from 3 to 20 mm) and position (adjacent to the tip of the anterior horns). The cysts enlarged and then regressed by a median corrected age of 2 months. Subjects of < 33 weeks gestation (n = 18) had a median birth weight of 1465 g (range 720-1990) and median gestation of 30 weeks (range 24-32). There was no consistent perinatal course. The neurodevelopmental outcome in 10 of the 11 survivors with isolated frontal horn cysts was normal. Five subjects died from causes unrelated to brain pathology in the neonatal period, and one subject died after infancy. Histological examination of a cyst at autopsy in one additional subject subsequent to the period of study confirmed the cyst to be lined by neuroblasts and ependymal cells. CONCLUSIONS: The incidence of frontal horn cysts in this low birthweight population was 7 per 1000 (0.7%) subjects scanned. They are present in the first week of life, enlarge, and resolve spontaneously. Survivors with isolated frontal horn cysts appear to have normal neurodevelopmental outcome. The prognosis of these distinct frontal horn cysts therefore appears to be benign.

An outbreak of Bacillus cereus respiratory tract infections on a neonatal unit due to contaminated ventilator circuits.

An outbreak of Bacillus cereus respiratory tract infections affecting six ventilated preterm neonates over a two-week period is described. Reusable ventilator circuits were identified as the cause of the outbreak. Ordinarily these were reprocessed on the Neonatal Unit (NNU), first through a washing machine and then through a low-temperature steam (LTS) disinfector. The onset of the outbreak coincided with a breakdown of the LTS facility, which necessitated sending the washed circuits off site for LTS disinfection. The washing machine was shown to be contaminated with the same serovars of B. cereus as those isolated from patients. Two critical steps in the off site LTS disinfection process allowed exsporulation and multiplication of B. cereus: the circuits were inadequately dried after processing, whilst return of the moist circuits to the NNU was often delayed. The outbreak was terminated by withdrawal of the heat-disinfected ventilator circuits. This outbreak emphasizes the need for high standards where medical equipment is reprocessed, especially for use in vulnerable patients.

Gastric emptying and gastro-oesophageal reflux in preterm infants.

Gastro-oesophageal reflux is common in preterm infants, but the role of gastric emptying as a causal factor has not been studied before. Gastric emptying was therefore measured in 19 healthy preterm infants (median gestational age 32 weeks) while concurrently measuring 24 hour lower oesophageal pH, using an antimony pH electrode, positioned manometrically. Real time ultrasonic images of the gastric antrum were obtained, and measurements of antral cross-sectional area (ACSA) were made immediately before a nasogastric feed and then during subsequent gastric emptying until ACSA returned to its pre-feed value. Half emptying time (50% delta ACSA) was calculated as the time taken for the ACSA to fall to half the maximal postprandial increment. Mean (SEM) reflux index for the group was 11.9 (2.0)%; number of reflux episodes per 24 hours: 15.4 (1.7); and number of reflux episodes longer than five minutes 5.5 (0.8). Average half emptying times for an individual infant were: median (range) 46 (18-105) minutes. There was no association between gastric emptying rates and any of the indices of gastro-oesophageal reflux, either during the entire 24 hour period for which the lower oesophageal pH was recorded, or in the postprandial periods after the feeds which were studied ultrasonically. Gastro-oesophageal reflux was also unrelated to feed volume and feed type. Asymptomatic gastro-oesophageal reflux is common in preterm infants, but gastric emptying time is not a determinant of it. Inappropriate relaxation of the lower oesophageal sphincter or abnormal oesophageal motility offer more plausible explanations.

Nosocomial infection with Rhizopus microsporus in preterm infants: association with wooden tongue depressors.

BACKGROUND: We report four cases of cutaneous infection with Rhizopus microsporus in vulnerable preterm infants in one neonatal nursery. METHODS: There was no overlap in hospital stay between the first two cases and an extensive programme of environmental sampling was therefore initiated, with special attention being paid to items that had close contact with infants' skin. Samples were cultured by standard techniques, including fungal culture with Sabouraud's medium. Filamentous fungi with non-septate hyphae were presumptively identified as agents of mucormycosis and referred to the Mycology Reference Laboratory, Bristol, UK, for speciation. FINDINGS: The source of infection was identified as wooden tongue depressors, which were used on the nursery to construct splints for intravenous and arterial cannulation sites. The outbreak was ended by the removal of these items from the nursery. INTERPRETATION: Wooden tongue depressors can be a vehicle for transmission of mucormycosis. The combination of warm, humid conditions in neonatal incubators, particularly in association with occlusive dressings, may favour cutaneous fungal invasion and put small, sick babies at risk of infection.

Catch up growth and pancreatic function in growth retarded neonates.

To test the hypothesis that relative pancreatic dysfunction is a determinant of catch up growth in small for gestational age (SGA) babies, 47 such babies (median gestation 38 weeks; range 27-41) and 41 appropriate for gestational age (AGA) babies matched for sex, race, and gestational age were recruited. Anthropometry was performed within 48 hours of birth and at 6 months. Faecal chymotrypsin activities were measured at 0-2 days, 14 days, 6 weeks and 6 months. At 6 months 30 SGA infants and 25 AGA infants were remeasured. In each group, median stool chymotrypsin activities doubled between 0-2 days and 6 months (9.0-25.5 IU/g SGA group; 11.6-25.3 IU/g AGA group). SGA babies had significantly lower chymotrypsin activities at 14 days (10.9 U/g) than AGA babies (15.5 U/g). In the SGA group faecal chymotrypsin activities at 0-2 days were strongly correlated with both catch up weight and with catch up length when corrected for the effects of birthweight. These data show that impaired pancreatic exocrine function at birth is associated with severe intrauterine malnutrition and with impaired catch up growth during the first 6 months of life.

Gastric emptying in preterm infants.

An ultrasonic technique was used to compare gastric emptying after a feed of expressed breast milk and formula milk in a blind, cross over study of preterm infants. Fourteen infants (median gestational age 33 weeks) were studied on 46 occasions. Each infant received a nasogastric feed of either expressed breast milk or formula milk, and the alternative at the next feed. Real time ultrasound images of the gastric antrum were obtained and measurements of antral cross sectional area (ACSA) were made before the feed and then sequentially after its completion until the ACSA returned to its prefeed value. The half emptying time (50% delta ACSA) was calculated as the time taken for the ACSA to decrease to half the maximum increment. On average, expressed breast milk emptied twice as fast as formula milk: mean 50% delta ACSA expressed breast milk 36 minutes; formula milk 72 minutes. The technique was reproducible and there was no significant difference between the emptying rates of feeds of the same type for an individual infant. These data show that breast milk has a major effect on gastric emptying, which may have important implications for preterm infants who have a feed intolerance due to delayed gastric emptying.

Abnormal gut blood flow velocities in neonates at risk of necrotising enterocolitis.

Duplex pulsed Doppler ultrasound was used to determine blood flow velocities in the coeliac axis and superior mesenteric artery in three groups of neonates: a group at high risk of developing necrotising enterocolitis (n = 27) and two control groups, i.e., a nonasphyxiated, appropriately grown group of preterm infants (n = 18) and a group of nonasphyxiated term infants (n = 14). Subjects were studied on the first, second, and fourth days of life. The median peak systolic velocities in the superior mesenteric artery were between 20 and 51% lower in the at-risk group than in the term control group on all 3 days of measurement (p less than 0.05-p less than 0.002). The ratio of peak systolic velocity in the coeliac axis to that in superior mesenteric artery, an index of relative downstream vascular resistance in the superior mesenteric artery, was 42-65% greater in the at-risk group compared with the other two groups on days 1 and 2 (p less than 0.05-p less than 0.001) and significantly greater than the term group on day 4 (73%, p less than 0.002). These data demonstrate that neonates at risk of developing necrotising enterocolitis have abnormal gut blood flow velocities. Furthermore, they provide evidence that an alteration in the splanchnic circulation may be an important factor in the final common pathway that links diverse risk factors for necrotising enterocolitis with clinical disease.

Doppler assessment of human neonatal gut blood flow velocities: postnatal adaptation and response to feeds.

Duplex pulsed Doppler ultrasound was used to study changes in gut blood flow velocities during the first week of life in a group of 14 term babies. There was a significant increase in fasting peak systolic velocity in the superior mesenteric artery between days 1 and 2 with a further upward trend until day 5; no such changes were seen in the coeliac axis. Fasting velocities were 20% lower in breast-fed babies than bottle-fed babies. Following feeds, there was a significant increase in velocity in the superior mesenteric artery that was 35% greater in the bottle-fed than breast-fed babies. Changes in the coeliac axis were qualitatively similar but substantially smaller. The peak velocity in both vessels occurred 50 min after a feed. We conclude that Doppler ultrasound can be readily used to measure gut blood flow velocities in the human newborn. It provides a noninvasive technique for investigating adaptive postnatal changes in the splanchnic circulation, and, in particular, the response to feeds.

Caffeine or theophylline for neonatal apnoea?

Caffeine, in the dose usually recommended (12.5 mg/kg loading dose and 3 mg/kg daily maintenance), and a higher dose regimen (25 mg/kg loading and 6 mg/kg daily maintenance), was compared with theophylline (7.5 mg/kg loading and 3 mg/kg thrice daily maintenance). The study was a randomised controlled trial in the treatment of a group of 44 infants of less than 31 weeks' gestation (mean gestational age 28.3 weeks) who were suffering from frequent apnoeic attacks. All three regimens produced a significant reduction in apnoeic attacks within 24 hours, but only the higher dose caffeine and theophylline groups showed a significant improvement in apnoea within eight hours. The use of caffeine for the treatment of neonatal apnoea is recommended, because a once daily dose is more easily administered, and because it was found that plasma concentrations were more predictable than those of theophylline. If used in very preterm infants, however, its is suggested that a higher dose regimen than that previously recommended be used to achieve a faster response.

Postnatal encephaloclastic porencephaly--a new lesion?

A previously unrecognised and distinctive pattern of severe brain injury in extreme preterm neonates was observed recently. Fifteen neonates of birth weight 600-1270 g and gestation of 24-32 weeks showed relatively late development on cerebral ultrasound scan of extensive dense and cystic lesions involving the periphery of the brain. The extent of the changes was confirmed at postmortem examination in 11 babies. These changes have been called encephaloclastic porencephaly. The population of babies in whom this has occurred and their clinical outcome has been reviewed, with comparison between the evolution of the ultrasound changes and pathological findings at postmortem examination.

Atypical allergic colitis in preterm infants.

Two atypical cases of colitis due to cow's milk protein intolerance (CMPI) are reported, affecting preterm infants. One developed a toxic dilatation of the colon and responded well to a casein hydrolysate based feed. The second presented insidiously and failed to tolerate a casein hydrolysate, but responded well to a chicken-based modular feed.

Gut blood flow velocities in the newborn: effects of patent ductus arteriosus and parenteral indomethacin.

The effects on gut blood flow velocities of parenteral indomethacin (0.2 mg/kg) given either quickly as a bolus or slowly as an infusion were compared in consecutive studies of two groups of infants with symptomatic patent ductus arteriosus. In the presence of patent ductus arteriosus the range of velocities in the superior mesenteric artery before indomethacin was given was characterised by pronounced abnormalities including absent--or in some cases even retrograde--diastolic flow. In eight subjects the first rapidly given bolus dose of indomethacin (duration 20 seconds or less) caused a pronounced and sustained fall in the velocity of the superior mesenteric artery blood flow (mean peak systolic velocity (cm/second): before 74; after 38; median time to maximum fall 7.4 minutes; median time to recovery 50 minutes). A further 10 subjects received their first dose of indomethacin by slow infusion (duration 30-35 min) and the percentage fall in peak systolic velocity was both substantially less (22% compared with 47%) and later (median time to maximum fall 37.3 minutes) than after rapid infusion. Qualitatively similar but smaller changes were seen in the coeliac axis. Return of antegrade end diastolic flow in the superior mesenteric artery within one hour of the first dose of indomethacin was a good predictor of subsequent closure of the ductus. These data suggest that there is a profound disturbance in mid gut perfusion in infants with patent ductus, which is exacerbated by indomethacin given rapidly by intravenous bolus. They may also provide a rational explanation for the well recognised association between necrotising enterocolitis and both patent ductus arteriosus and indomethacin administration. The unwanted effects of the indomethacin are abrogated by slow infusion, without loss of efficacy in closure of the ductus.

Does mechanical ventilation precipitate gastro-oesophageal reflux during enteral feeding?

The influence of intermittent positive pressure ventilation on gastro-oesophageal reflux in preterm infants is not known. In many neonatal units, however, concern that ventilation may increase gastro-oesophageal reflux (and therefore aspiration) leads to avoidance of enteral feeding during ventilation. We have therefore performed a crossover study of gastrooesophageal reflux by monitoring lower oesophageal pH in a group of nine enterally fed, very low birthweight infants both during assisted ventilation and normal breathing. All infants had less reflux during intermittent positive pressure ventilation (mean (SEM) reflux index 2.3 (0.6%)) than during normal breathing (mean (SEM) reflux index 6.1 (1.1%)). Assisted ventilation was associated with a significant reduction in the gastro-oesophageal pressure gradient, an effect which may be related to the use of positive and end expiratory pressure during ventilation. These data show that fear of gastro-oesophageal reflux should not preclude the use of enteral feeding in preterm infants receiving ventilation.

Gastro-oesophageal reflux in preterm infants.

Gastro-oesophageal reflux in very low birthweight infants was studied using a new 1 mm monocrystalline antimony oesophageal pH electrode. Gastro-oesophageal reflux was detected in 30 (85%) subjects. The mean (SEM) number of episodes of reflux in 24 hours was 12.1 (2.1), and 3.2 (0.6) lasted over five minutes. The mean reflux index was 4.5 (1.0)%, and the longest episode 17.1 (4.6) 17.1. Reflux was unrelated to postconceptional age or to resting lower oesophageal sphincter pressure. The mean reflux index was low at rest before feeds, being 1.8 (0.6)%, and increased slightly after feeds (3.8 (1.0)%), but was significantly increased after nursing care to 16.4 (3.0)%, and while xanthines were being given (5.9 (1.6)%. A subgroup of seven infants with xanthine resistant apnoea had severe gastro-oesophageal reflux that was not clinically apparent (reflux index 27.4 (3.6)%). Successful treatment of the reflux (reflux index: 3.6 (1.2)%) was associated with cessation of the apnoea. We conclude that gastro-oesophageal reflux is common, and is usually not clinically apparent, even when severe. It is important to consider gastro-oesophageal reflux in the differential diagnosis of xanthine resistant apnoea in preterm infants.

Maturation of the lower oesophageal sphincter in the preterm baby.

There are few reported studies of the lower oesophageal sphincter in preterm infants and none has investigated babies of less than 34 weeks gestation. Using a modified manometric technique suitable for use on very low birth weight infants we have measured sphincter pressures on 68 occasions in 25 infants of postconceptional age between 27 and 41 weeks. In even the most preterm infants the lower oesophageal sphincter could be defined. The mean effective sphincter pressure rose from 3.8 mmHg in infants of less than 29 weeks gestation to 18.1 mmHg in the term infant. This rise in effective sphincter pressure correlated well with increasing postconceptional age (r = 0.81). This pattern of maturation in our patients was unaffected by intrauterine growth retardation, postnatal illness, or concurrent xanthine administration.