CBF reactivity in hypotensive and normotensive preterm infants

Perinatal distress in the preterm neonate, and the consequent loss of cerebrovascular autoregulation, has been implicated in the pathogenesis of neonatal cerebral lesions. A component of this distress is thought to be hypotension. We examined the autoregulatory capacity of hypotensive and normotensive infants using the 133Xe technique to measure cerebral blood flow. Global CBF was measured during only normotension in 5 infants, and during both hypotension and normotension in 11 infants. All the infants were ventilated and blood pressure was measured using an intra-arterial catheter. Fourteen CBF measurements were made on the normotensive infants. Forty-seven CBF measurements were made on the hypotensive infants, 34 measurements during hypotension and 13 during normotension. The global CBF of the normotensive and hypotensive infants were 13.3 and 13.6 mL/100 g/min, respectively. The mean arterial blood pressure (MABP)-CBF reactivity (95% CI) of the normotensive and hypotensive infants were 1.9% (-0.8% to 4.7%)/mm Hg and 1.9% (0.8% to 3.0%)/mm Hg, respectively. The CO2-CBF reactivity (95%CI) of the normotensive and hypotensive infants was 11.1% (6.8% to 15.5%)/KPa deltaPaCO2 and 4.1% (-5.0% to 14.1%)/KPa deltaPaCO2. The implications of these calculated CBF reactivities is that normotensive infants may have intact autoregulation but with a diminished response to fluctuations in PaCO2. The hypotensive infants appear to have attenuated or absent autoregulation with little or no response in CBF to changes in PaCO2.     

Compensatory Increase of CBF in Preterm Infants during Hypoglycaemia

ABSTRACT. Cerebral blood flow (CBF₀₀) was investigated in 24 preterm infants (mean 30.8 weeks of gestational age) by use of intravenous 133-Xe clearance technique while screening simultaneously for low blood glucose after birth (mean 3 hours). CBF was significantly increased in 10 infants with blood glucose lower than 1.7 mmol/l compared to normoglycaemic infants and tended to decrease rapidly after treatment. Nine of the 10 hypoglycaemic infants were monitored for cerebral function. Well defined visual evoked cortical potentials were elicit-able in all and the aEEG was not less active during the hypoglycaemic episode. Therefore, it is suggested that compensatory increase of CBF may have supported the cerebral metabolism during uncomplicated hypoglycaemia.     

Hyperinsulinaemic hypoglycaemia in preterm neonates

Hyperinsulinism in infancy (HI) is an important cause of severe and recurrent hypoglycaemia in newborn infants. It usually appears in infants born at term, and only one case of its occurrence in a prematurely born infant has been reported as an incidental finding. This is a report of seven infants born at 31-36 weeks gestation who experienced severe persistent hyperinsulinism. Two infants were large for dates. All infants were difficult to manage, suggesting that the occurrence of HI with prematurity may be associated with a particularly aggressive illness. HI should be considered in the differential diagnosis of severe hypoglycaemia in preterm infants.     

Cerebral hemodynamics during arousals in preterm infants

The aim of the study was to evaluate potential changes of cerebral blood volume (CBV) related to arousals in preterm infants. As arousals are known to change different physiological parameters, it was postulated that this could also hold true for CBV. Polygraphic recordings were performed in 38 preterm infants (18 female, 20 male). The infants' gestational age at birth was 32.0+/-2.3 weeks, postconceptional age was 35.1+/-1.2 weeks and postnatal age at study entry was 24.3+/-2.9 days, birth weight was 1793+/-527 g and actual weight at study entry was 2011+/-324 g [mean (+/- standard deviation)]. CBV was measured using near infrared spectroscopy. Arousals were scored due to the guidelines of the "International Paediatric Work Group on Arousals" and categorized as either cortical (CA) or subcortical arousals (SCA). Altogether, 122 arousals (66 CA, 56 SCA) were scored. According to sleep stage, 77 arousals were analyzed in active sleep, 23 in quiet sleep and 22 in intermediate sleep. Mean duration of arousals was 8.8+/-0.3 s. CBV, cerebral vascular oxygenation and the balance between oxygen delivery and oxygen consumption remained constant during arousals in preterm infants. This was demonstrated for both CA and SCA and was independent of sleep stage, suggesting that the impact of arousals in stable preterm infants is too small to alter cerebral vascular autoregulation.     

Cardiorespiratory stability during echocardiography in preterm infants

Blood pressure, heart rate, and oxygen saturation were monitored prospectively during 40 echocardiography recordings on 17 preterm infants (25-29 weeks; 510-1430 g), to examine whether echocardiography can be performed without disturbing cardiorespiratory status in preterm infants. There was no impact on absolute blood pressure. Heart rate increased by a mean of 4 beats per minute, and oxygen saturation decreased by a mean of 1% during echocardiography. While these changes reached statistical significance they are not of clinical significance as they remained well within ranges seen during control rest periods. All readings had greater minute-to-minute variability during echocardiography but differences were small and again remained within physiological ranges.     

Body composition of preterm infants during infancy

AIMS: To examine body composition in preterm infants. METHODS: Body composition was measured by dual energy x-ray absorptiometry (DEXA) at hospital discharge, term, 12 weeks, and at 6 and 12 months corrected age in 125 infants (birthweight < or = 1750 g, gestational age < or = 34 weeks). RESULTS: Body weight derived by DEXA accurately predicted that determined by conventional scales. In both sexes lean mass (LM), fat mass (FM), %FM, bone area (BA), bone mineral mass (BMM), and bone mineral density (BMD) increased rapidly during the study; significant changes were detectable between discharge and term. At 12 months, LM, BA, and BMM, but not FM, %FM, or BMD were greater in boys than in girls. Corrected for age, LM was less than those of the reference term infant; FM and %FM were similar; BMM was greater. Corrected for weight, LM was similar to those of the reference infant, while the FM and %FM of study infants were slightly greater. CONCLUSIONS: DEXA accurately measures body mass. Body composition in preterm boys and girls differs. Interpretation of DEXA values may depend on whether age or body weight are regarded as the appropriate reference.     

Inflation times during resuscitation of preterm infants

Data on the effects of a prolonged inflation time during the resuscitation of very prematurely born infants are limited; one study showed no effect, and in another, although lower bronchopulmonary dysplasia (BPD) rates were seen, that effect could have been due to the prolonged inflation time, the positive end expiratory pressure applied or the combination of the two. The aims of our study were to assess the length of inflation times used during face mask and t-piece resuscitation of prematurely born infants in the labour suite and determine whether prolonged inflations led to longer inflation flow times. A respiration monitor (NM3 respiratory profile monitor) was used to record flow, airway pressure and tidal volume changes. The first five inflations for each baby were analysed. Forty prematurely born infants (median gestational age 30, range 26–32 weeks) were examined. Their median inflation pressure was 17.6 (range 12.2–27.4) cm H₂O, inflation time 0.89 (range 0.33–2.92) s, expiratory tidal volume 1.01 (range 0.02–11.41) ml/kg and inflation flow time 0.11 (range 0.04–0.54) s. There was no significant relationship between the inflation time and the inflation flow time, but there was a significant relationship between the inflation pressure and the inflation flow time (p = 0.024). Conclusion: These results suggest that prolonging inflation times during face mask resuscitation of prematurely born infants would not improve ventilation as prolonged inflation did not lead to longer inflation flow times.     

Decreased ventilation in preterm infants during oral feeding

As respiratory difficulty may accompany nipple feeding in preterm neonates, we studied the effect of oral feeding on ventilation in 23 preterm infants. The infants composed two groups based on their postconceptional age at the time of study: Group A comprised 12 infants 34 to 35.9 weeks of age, and group B, 11 infants 36 to 38 weeks. Ventilation was measured via a nasal mask pneumotachometer, and sucking pressure via a nipple that also permitted milk delivery; transcutaneous PO2 and PCO2 were continuously monitored. The feeding pattern comprised an initial period of continuous sucking of at least 30 seconds, followed by intermittent sucking bursts for the remainder of the feed. When compared with an initial semi-upright control period, minute ventilation (V1) during continuous sucking fell by 52 +/- 6% (P less than 0.001) and 40 +/- 2% (P less than 0.001) in groups A and B, respectively. This was the result of a decrease in respiratory frequency and tidal volume and was associated with a fall in TcPO2 of 13 +/- 4 mm Hg (P less than 0.01) in group A and 10 +/- 2 mm Hg (P less than 0.01) in group B. During intermittent sucking, V1 and TcPO2 recovered partially only in the more mature infants (group B). At the end of the feed, TcPCO2 have risen by 3 +/- 1 mm Hg (P less than 0.001) in group A and by 2 +/- 2 mm Hg (P less than 0.05) in group B. Thus oral feeding results in an impairment of ventilation during continuous sucking and the subsequent recovery during intermittent sucking is dependent on postconceptional age.     

Cardiorespiratory stability during echocardiography in preterm infants.

Blood pressure, heart rate, and oxygen saturation were monitored prospectively during 40 echocardiography recordings on 17 preterm infants (25-29 weeks; 510-1430 g), to examine whether echocardiography can be performed without disturbing cardiorespiratory status in preterm infants. There was no impact on absolute blood pressure. Heart rate increased by a mean of 4 beats per minute, and oxygen saturation decreased by a mean of 1% during echocardiography. While these changes reached statistical significance they are not of clinical significance as they remained well within ranges seen during control rest periods. All readings had greater minute-to-minute variability during echocardiography but differences were small and again remained within physiological ranges.     

Patterns of oxygenation during periodic breathing in preterm infants

The characteristics of the arterial oxygen saturation (SaO2) signal during episodes of hypoxaemia (SaO2 less than or equal to 80% for greater than or equal to 4 s) associated with periodic and non-periodic apnoeic pauses were studied in 16 preterm infants with cyanotic episodes (patients). and 15 asymptomatic preterm infants (controls), matched on birthweight and gestational age. The patients showed a significantly higher percentage of apnoeic pauses followed by a hypoxaemic episode (25 vs. 6%, P less than 0.01), and a two-fold increase in the slope of the desaturation curve (8.4 vs. 4.3% per s, P less than 0.005) in periodic compared with non-periodic breathing. All other characteristic of oxygenation (baseline SaO2 before episodes of hypoxaemia, delay between onset of apnoeic pause and onset of desaturation, lowest SaO2 during episodes of hypoxaemia) were similar for periodic and non-periodic breathing patterns. Similar, but not significant, differences between isolated and periodic apnoeic pauses were also present in the controls. An analysis of episodes of bradycardia (less than or equal to 100 beats per minute (bpm] showed that out of 121 episodes in the patients 118 were accompanied by a fall in SaO2 to less than or equal to 80%, and in the remaining three SaO2 fell to 82%, 85% and 86%, respectively. Thus all episodes of bradycardia (less than or equal to 100 bpm) were associated with a fall in SaO2 detected by beat-to-beat pulse oximetry. Examination of hypoxaemic episodes and their relationship with bradycardia and with apnoeic pauses, periodic and non-periodic, may help the further understanding of the control of arterial oxygenation in preterm infants with cyanotic episodes.     

Transcutaneous oxygen tension during nonnutritive sucking in preterm infants

The effects of nonnutritive sucking on transcutaneous oxygen tension, heart rate, and respiratory rate were studied sequentially in 14 sleeping preterm infants breathing room air. Transcutaneous oxygen tension increased during nonnutritive sucking in infants between 32 and 35 weeks postconceptional age, but not in those between 36 and 39 weeks. This response was not associated with a change in respiratory rate or sleep state, although heart rate tended to increase. These data offer further support for the beneficial effects of nonnutritive sucking in preterm infants.     

Sympatho-adrenal response to hypoglycaemia in infants

The response of the sympathoadrenal system to hypoglycaemia of different etiology was studied in seven infants, aged 10–189 days. Five infants had hyperinsulinism secondary to nesidioblastosis or to a -cell adenoma of the pancreas, one infant had neonatal sepsis due to staphylococcal infection and one infant congenital growth hormone (HGH) and adrenocorticotropic hormone (ACTH) deficiency. In babies with hyperinsulinism, plasma noradrenaline increased from 0.29±0.03 to 0.61±0.09 ng/ml (P<0.01), whereas adrenaline increased only in three, but did not change in two babies. Increases in heart rate and blood pressure paralleled these changes. In hypoglycaemia due to congenital sepsis, noradrenaline increased from 0.39 to 1.64 ng/ml and adrenaline from 0.05 to 0.86 ng/ml. This was associated with marked haemodynamic changes. In congenital HGH and ACTH deficiency, the low basal plasma levels of noradrenaline (0.12 ng/ml) and adrenaline (0.01 ng/ml) remained unchanged in response to hypoglycaemia. Heart rate and blood pressure were unaffected. The sympathoadrenal system was activated by hypoglycaemia in all infants except in congenital HGH and ACTH deficiency. In contrast to adults, noradrenaline was the preferentially released catecholamine, suggesting an involvement of noradrenaline in glucose counter regulation in infancy.Abbreviations ACTH adrenocorticotropic hormone - HGH human growth hormone     

Routine handling of milk fed to preterm infants can significantly increase osmolality

BACKGROUND: The purpose of these studies was to evaluate the changes in osmolality which occur in human breast milk or formula after two modifications; these changes are sometimes used in preparing these milks for consumption by premature infants, namely, the addition of fortifiers and the addition of exogenous lactase enzyme. METHODS: The osmolality of expressed, previously frozen human breast milk, breast milk fortified with commercial fortifiers, liquid formulas, powdered formulas, or glucose polymers was measured. Osmolality was measured before and after warming (15 minutes at 37 degrees C) or after refrigeration at 4 degrees C for 12 hours with subsequent warming. In a second group of experiments, the osmolality of expressed breast milk and three lactose-containing formulas was measured before and after incubation with lactase (Lactaid ) at 4 degrees C for 2, 6, and 24 hours. RESULTS: Warming of breast milk mixed with some of the additives was associated with a significant increase in osmolality. The additives which increased osmolality included liquid glucose polymers, two commercially available powdered human milk fortifiers, and three formulas which contain glucose polymers (a protein hydrolysate infant formula powder, powdered lactose free formula, and a powdered preterm formula). Maximum increase in osmolality of breast milk occurred with the addition of 20 ml/100ml liquid glucose polymers (Polycose, Ross Laboratories) which resulted in a 21% increase in osmolality after refrigeration and warming. The addition of liquid glucose polymers and of powdered preterm formulas containing glucose polymers (Enfacare, Mead Johnson, 9.5 g/100ml and Nutramigen, Mead Johnson, 6 g/100ml) resulted in a final osmolality of over 425 mOsmol/L. The addition of lactase and subsequent incubation under refrigeration resulted in significant increases in osmolality that ranged from 25 to 66% in fortified breast milks and lactose-containing formulas. Incubation of these milks at 37 degrees for 15 minutes produced about 50% greater increase in osmolality than observed after 2 hours of incubation under refrigeration. CONCLUSIONS: Routine warming of breast milk with glucose polymer-containing additives, or the addition of lactase enzyme to lactose-containing feedings, can increase osmolality to levels that exceed current guidelines for premature infant feedings.     

Neonatal hypoglycaemia in infants of diabetic mothers

OBJECTIVE: To determine whether umbilical cord blood glucose correlates with subsequent hypoglycaemia after birth in infants of well-controlled diabetic mothers. METHODOLOGY: Thirty-eight term infants of well-controlled diabetic mothers were enrolled. Five mothers had pre-existing diabetes. Of the 33 gestational diabetic mothers, 16 were managed on insulin and 17 on diet. Maternal blood glucose was maintained between 4 and 8 mmol/L during labour and delivery. Infants' plasma glucose levels were measured from venous cord blood and serially, at less than 30 min, 1 h and 2 h of life by glucose hexokinase method. Blood glucose levels were further monitored by bedside Dextrostix for 24 h. RESULTS: Eighteen (47%) infants developed hypoglycaemia (blood glucose level less than 2 mmol/L) during the first 2 h of life. There was no difference in the cord blood glucose levels between infants with or without hypoglycaemia (3.7 +/- 1.1 vs 4.5 +/- 1.1 mmol/L, respectively). Infants of mothers with diabetes diagnosed prior to 28 weeks gestation were at a higher risk of developing hypoglycaemia (8 of 10 vs 10 of 28, OR 7.2, 95%CI 1.3-40.7). Hypoglycaemic infants were of significantly higher birthweight, and were more likely to be born to Caucasian mothers and by Caesarean section. Raised maternal fructosamine blood level, the need for insulin treatment or the infant's haematocrit were not different between infants with or without hypoglycaemia. CONCLUSIONS: In well-controlled diabetic mothers, the incidence of early hypoglycaemia in infants is still high, particularly in those mothers who had a longer duration of diabetes. Cord blood glucose level did not identify the infants with hypoglycaemia.     

Parenting stress in mothers of preterm infants during early infancy

Objective

Mothers of preterm infants during the first year of life may experience stresses greater that those found in mothers of term infants. The aim of the study was to determine the levels of parenting stress and psychological well-being in mothers of very preterm babies in comparison to a control group of term mothers.

Methods

One hundred and five mothers who delivered 124 babies at ≤ 30 weeks gestation were recruited together with 105 mothers who delivered 120 babies at term. At 4 months of age (corrected for prematurity for the preterm babies), the mothers completed the Parenting Stress Index Short Form, the Edinburgh Postnatal Depression Scale (EPDS), the Dyadic Adjustment Scale (DAS) and the Short Temperament Scale for Infants (STSI). The preterm and term groups were compared.

Results

Questionnaires were returned from 86 of the preterm mothers and 97 of the term mothers. The mean Total Stress score for the preterm and term groups was 67.0 and 63.79 respectively (P = 0.32) with 17% of the preterm and 9% of the term group having high scores (P = 0.135). There were no differences of the EPDS and the DAS between the groups. The temperament of the preterm infants was similar to the term infants. For both groups, scores on the EPDS, DAS and the STSI were independent predictors of Total Stress scores on multiple regression analysis.

Conclusion

Parenting stress in mothers of preterm infants during early infancy does not appear to be greater than that in mothers of infants born at term. For both groups of mothers, depression symptoms, marital satisfaction and infant temperament were independent risk factors for high levels of parenting stress.     

Development of postural adjustments during reaching in preterm infants.

Preterm infants often show postural abnormalities, such as hyperextension of neck and trunk, which can interfere with motor and cognitive development. Little is, however, known on the pathophysiology of postural development in preterm infants. Therefore, we longitudinally studied the development of postural adjustments during reaching movements in 12 preterm infants between the (corrected) ages of 4 and 18 mo. Five infants showed minor neurological dysfunctions at 18 mo, such as a mild diffuse hypotonia, a mild hypertonia of the legs, or a mild asymmetry in posture and motility, and seven infants were neurologically normal. Each assessment consisted of a simultaneous recording of video-data and surface electromyograms of arm, neck, trunk, and leg muscles during reaching in various lying and sitting positions. Comparable data on postural development in ten full-term infants were available. The preterm infants showed an excessive amount of postural activity during reaching movements at all ages studied. Moreover, the postural adjustments were temporally disorganized and could not be modulated with respect to the velocity of the arm movement and the initial sitting position. We hypothesized that the preterms' disability to modulate their postural adjustments might be due to a reduced capacity to learn from prior experience. In our small group the postural dysfunctions were not related to the presence of hyperextension at early ages, to the neurological outcome at 18 mo, or to the lesions found on the neonatal brain ultrasound scans.