UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl)
Early neurological delopment, growth and nutrition in very preterm infants
Maas, Y.G.H.
Publication date
1999
Link to publication
Citation for published version (APA):
Maas, Y. G. H. (1999). Early neurological delopment, growth and nutrition in very preterm
infants.
General rights
It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons).
Disclaimer/Complaints regulations
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.
CHAPTER 2
Study design
2.1 Introduction 2.2 Study population 2.3 Methods 2.3.1 Nutritional intake 2.3.1.1 Feeding regimen 2.3.1.2 Daily dietary intake 2.3.1.3 Maternal milk samples 2.3.1.4 Calculating nutritional intake 2.3.2 Physical development (growth) 2.3.3 Neurological development2.3.3.1 Behavioural States
2.3.3.2 Quality of General Movements 2.3.4 Clinical data
2.3.5 Administration of T4/Placebo 2.3.6 Statistical analysis
29
2.1 Introduction
We initiated a longitudinal study on physical and neurological development in preterm infants born before 30 weeks gestational age. In this study the infants were randomly assigned to two different dietary regimens: standard formula (STF) or preterm formula (PTF) as a supplement to maternal milk. Due to reasons of logistic nature, these infants were also enrolled in a placebo controlled (double-blind), randomized trial on thyroxine supplementation (T4), compelling us to first examine possible interaction effects of an early feeding regimen and thyroxine supplementation on early development (1). This study was carried out in the neonatal intensive care unit (NICU) of the Academical Medical Center (AMC) in Amsterdam. The study protocol approved by the AMC Medical Ethical
Committee. This chapter describes our study population and the methods for as far as they have reference to more than one of the chapters 3 to 7. Statistical methods used for the analysis of the different data are described in each of the relevant chapters.
2.2 Study population
This study is based on 160 infants, born in 1991 and 1992, that participated in a "parent" study on thyroxine (T4) administration in 200 infants, born between Januari 1991 and July 1993. All infants born at a gestational age of less than 30 weeks and admitted to the Intensive Care Unit of the Academical Medical Center, were entered into the randomized, double-blind, placebo controlled parent trial of T4 administration (8), if after full
explanation informed consent from at least one parent was obtained within 24 hours after birth. Babies were excluded if they had a major congenital abnormality known to influence growth or neurological development or when the mother had an endocrinological disease or was an illicit drug user. Of the 216 infants considered for inclusion in 1991 and 1992, 19 infants died within 24 hours after birth, 8 were not included based on our exclusion criteria, the parents of 16 infants refused informed consent and the parents of 13 infants were not asked informed consent for reasons like e.g. a language barrier. Assignment to thyroxine or placebo took place within 24 hours following birth and additional random assignment to standard (STF) or preterm formula (PTF) within 72 hours postpartum. T4 randomization was performed in blocks of 10 infants and diet randomization was done
within the T4 randomization scheme in 4 blocks of 40 infants. An additional 11 infants died between 24 and 72 hours after birth (Figure 2.1).
It was not considered acceptable to influence a mother's choice whether or not to give breastmilk to her infant(s). Therefore all mothers were asked if they wanted to give their own milk to their infant(s) and infants were stratified according to this choice, after randomization to thyroxine or placebo. If the mother chose not to express breast milk, her infant was randomly allocated to start enteral feeding with either 'standard' formula (STF) or 'preterm' formula (PTF), as sole diet. If she decided to feed her baby with her own milk, the infant was randomly allocated to start enteral feeding with the standard formula (STF) or the preterm formula (PTF) as a supplement to maternal milk. Of the 149 infants enrolled in our study, 120 entered into the "maternal milk (MM) group" and 29 into the
"only formula feeding (FF) group".
The infants were studied in the postnatal period until they left our neonatal unit (either to go home or to be transferred to another hospital) or until they reached term age in our unit. Whenever possible, the infants were seen again at term age.
2.3 Methods
2.3.1 Nutritional intake
Till the start of this study the feeding regimen in our NICU was to initiate acceptance of enteral feeding with standard formula (STF), based on the experience of an increased incidence of necrotizing enterocolitis with the first introduction of a preterm formula (PTF). STF was replaced by PTF about one week after accepting full enteral feeding. In this study we compared this "old" feeding regimen with one in which new preterm formula was used to initiate acceptance of enteral feeding.
2.3.1.1 Feeding regimen
All infants started enteral feeding between 24 hours and several days after birth, depending on their clinical condition. Enteral feeding was increased thereafter till a full enteral intake of 125 + 15 kcal/kg/day had been achieved. Sick infants were fed intravenously and enteral feeding was started and gradually increased as tolerated, only after extubation. It was assumed that 100 ml of human milk contained the same amount of energy as the
Standard Formula Preterm Formula 66 (280)* 80 (345)* 1.4 [8]" 2.2 [11]* 7.1 [43]* 8.0 [40]* 7.0 4.0 3.6 [49]* 4.4 [49]* 0.44 0.99 3.11 3.33
'standard' formula, i.e. 66 kcal, whereas the 'preterm' formula contained 80 kcal per 100ml.
The macronutrient composition of the standard and preterm formula is shown in table 2.1.
Table 2.1 Macronutrient composition of standard formula (Nutrilon Premium, Nutricia Nederland b.v.) and preterm formula (Nenatal, Nutricia Nederland b.v.)
Energy (kcal/100 ml) Protein (g/100 ml) Carbohydrate (g/100 ml) Lactose (g/100 ml) Fat (g/100 ml) MCT's (g/100 ml) LCT's (g/100 ml) * (kJ/100 ml) Y [energy %]
Since our experimental feeding regimen aimed at feeding isocalorically, the main
differences in macronutrient intake from the two formulas concerned the amount of protein (0.5 g/100ml more in PTF), carbohydrate composition (STF carbohydrate consisted of almost 100% lactose, while PTF carbohydrate of only 50%) and fat composition (twice the amount of MCT's in PTF and a comparable amounts of LCT's in both).
2.3.1.2 Daily dietary intake
Data on daily dietary intake were collected on especially designed forms. The ICU/HCU nursing staff were asked to fill in these forms in addition to and apart from the standard ICU/HCU forms after elaborate instructions. Every day the completed forms were collected and new forms were put at a conspicuous spot near the incubator. Different forms were used for continuous and intermittent feeding. We collected data on the formula/maternal milk used, the amount of formula/maternal milk given to the infant, whether the infant was fed by tube, by breast or bottle, the assessed stomach retention and assessed vomit. We also
Study design 33
asked the nurses of each shift, responsible for the care of an infant in our study protocol, to write down their names in order to be able to trace missing or unclear information on the form.
We collected a total of 6895 24-hour intake records of 148 out of the total of 149 infants randomized for diet; 5766 in the MM group (n= 119) and 1129 in the FF group (n = 29). One infant was randomized in the MM group but died just before 72 hours after birth, therefore no intake data could be collected.
2.3.1.3 Maternal milk samples Collection of milk samples
Milk samples were obtained at weekly intervals from the mothers who had expressed to have the intention to breast-feed their infants. The collection of the 24-h samples started as soon as there was sufficient milk to feed the child and to take an aliquot of 25 ml for analy-sis. Samples were taken for as long as the infant stayed in our hospital and milk production was adequate. Mothers pumped their breasts manually or mechanically, collecting the milk in sterile (deionized) bottles. The number and time of expressions varied per mother, according to their own habits. All expressions were pooled over 24 hours, mixed thoroughly and volume was measured. All samples were stored at -20 °C until analysis.
Chemical analysis
Total nitrogen concentration (mg/100 g) was determined using Kjeldhal analysis (Helrich, 1990). Crude protein was calculated by multiplying Kjeldhal nitrogen by 6.38. Fat (g/100 g) was determined according to the method of Roese-Gottlieb (Helrich, 1990). Lactose (g/100 g) was determined using an enzymatic procedure (Boerhinger Mannheim GmbH, 1989). Carbohydrate (g/100 g) was calculated as:
Carbohydrate = dry matter - protein - fat - ashes,
dry matter being determined as the mass left after evaporation (vacuum) at
102 °C and ashes being determined as the mass left after glowing at 550 °C (Helrich, 1990). Gross total energy content (kJoules/100 g) was calculated as:
Energy = ( Protein * 5.65 + Fat * 9.25 + Carbohydrate * 3.95) * 4.18,
4.18 being the conversionfactor in kJoules/kcal to calculate kJoules (Anderson et al. 1981).
We collected a total of 425 milk samples from 95 mothers during the first 14 postnatal weeks. Each sample was checked for its suitability for analysis. All samples taken by another person than myself or my students, were removed from analysis (n = 31). All samples that were of questionable reliability due to other reasons like e.g. a mother's collecting behaviour, insufficient registration of data concerning the sample taken, incompleteness of the 24-hour sample (n = 41), or to "over"-completeness of the 24-hour sample (n=23), were also removed from analysis. This resulted in 330 samples from 80 mothers suitable for analysis.
2.3.1.4 Calculating nutritional intake
Each nutritional intake form was checked carefully when calculating the nutritional intake for every infant per 24 hours for as long as an infant stayed in our department to a maximum of 99 days postpartum. The data on these forms were entered into a large database. From these data we calculated the amount of parenteral and/or enteral formula and/or maternal milk the infants actually received. To be able to calculate nutrient intake these dietary intake data needed to be combined with our maternal milk data. Milk samples were taken weekly at most. When a milk sample had been analysed, these data were used for all seven days of that particular week for that infant. If no sample was available for analysis in a particular postnatal week, the average nutrient values of all the available milk samples in that same postnatal week were used for each day of that week.
From these data we were able to calculate parenteral and enteral (i.e. STF and/or PTF and/or maternal milk) protein, lipids and carbohydrates in grams, which are necessary to calculate the total amount of energy consumed and the energy percentages of parenteral versus enteral nutrition, of the different enteral formulas, of maternal milk and of the separate macronutrients. All above data were also expressed per kg body weight, as daily weights were collected.
2.3.2 Physical development (growth)
Study design 35
chapter 4.
Out of the 149 infants enrolled in our study, 11 were never measured, 10 in the MM group and 1 in the FF group. In the MM group 1 infant was transferred to another hospital within 6 days postpartum. The other 10 infants died between 72 hours and 21 days postpartum. The remaining 138 infants were measured a total of 965 times between the first and 19th postpartum week, 810 in the MM group and 155 in the FF group. Of these 965
measurements 108 were done at term age (38-42 weeks PMA), 91 in the MM group and 17 in the FF group (table 2.2).
2.3.3 Neurological development
At the start of our study we did not do a behavioural states observation when the infants returned at term age for follow-up, but we made a 10 to 15 minutes' video recording of the infant in order to be able to assess the quality of general body movements.
2.3.3.1 Behavioural States
Five channel polygraphic recordings (see fig. 2.2) were made in addition to continuous observation (see fig. 2.3) to be able to determine behavioural states (2-5). For a more detailed description see chapter 5.
Of the 149 infants enrolled in our study 26 were never observed, 24 in the MM group and 2 in the FF group; 12 infants (1 in the FF group) because they died within 3 weeks after birth; 5 (1 in the FF group and 4 in the MM group (of which 3 died)) because of the severity of their illness in the first 7 postnatal weeks, 1 because she was transferred to another hospital 6 days postpartum, 2 (twins) because the parents withdrew their informed consent and 6 because of absence of observers. We observed the remaining 123 infants in total 454 times between PMA-week 26 and PMA-week 46: 372 times in the MM group and 82 times in the FF group. Seventy six of the 454 observations were done at term age (38-42 weeks PMA), 66 in the MM group and 10 in the FF group (table 2.3).
2.3.3.2 Quality of General Movements
During each behavioural states observation a 2-hour video recording was made for assessment of the quality of general body movements and at term age a video recording of
o ti-li, 00 e 5 o ON o3 O 3 1) O o-o oo ON CN -cj-C N NO f -•* NO OO oo 0 0 0 0 CN CN oo CN oo oo co CN co NO NO O. 3 O Ui OO M S 2 oo G O P. •a a M ,—.. S U i S £ » ^ < S
s
Cu 3 CA AC Ü 1) u cd £ CM o xt-. G 1 OC a CO TS 3 O " Ü S- u< 3 a* <u •— ^ o ° Ü « •» T3 3 cO co o U *-* ra vO CN CO CO 15 M Ut CD 3 1) C £ > cd cd Ä 3 0) l—i . O CO S eu 3s
S a, CO O ex u 1-CO OJ o =s o , , U i cd 3 =3 CU U, 3 C/3 U i Ö ,o (L>4--g
X3 ÇL) en O •3 c 3 t-H CO 1) CO c e CX ,cd 3 E 3 3 1) H d-3 •a 3 3 3 -o CU CU CJ JS Cl— H cd m 3 CN E aj ,o C 4 - . S ra OJ H -5 tu- en uu -* O ra O co NO co •4 O O ex co co O N N O N O CN CO NO co CS co oo en o m NO ON CN t - -CN oo CN O CN ON NC' CN ^ 3 O Ui 00 ON oo o o o o o ON oo CO NO oo C N C N C N •O co N O n. 3 O OO C tu ra JS 3 Ui 3 Ui NO 3 B O N E cd II s-S G O t u CN o HStudy design
Figure 2.2 Polygraphie recordings showing a) "Active" or REM-sleep and b) "Quiet" sleep. The 4 lines represent: respiratory frequency (RF). heart rate (HR), spontaneous motility (ACTIVITY) and rapid eye movements (REM).
37
feW)^'^
111 -.. ' \ . ti' * • IUL
IfiCTll/ITy
Tr
Figure 2.3 Fragments from a 2-hour (120 minutes) observation for assesment of behavioural states. The upper 6 photo's show facial expressions like grimaces (second photo on the left), smiles (first photo on the right and third photo on the left) and "opened" REM eyes (third photo on the right) that can be seen in state 2. The 2 photo's at the bottom show the same baby while awake, with eyes open. Note the difference in quality of eye opening with above.
Study design 39
at least 15 minutes to be able to assess the quality of general movements. Video tapes were replayed and from each recording session a number of the most complete general
movements were selected to be analysed (6-8). For a more detailed description see chapter 6.
The number of infants seen for assessment of general body movement quality is the same as for the behavioural states observation except for term age and beyond term age.
We scored 123 infants a total of 495 times for quality of general body movements between PMA-week 26 and PMA-week 46: 406 times in the MM group and 89 times in the FF group. One hundred and ten of the 495 general body movements recordings were made at term age (38-42 weeks PMA), 93 in the MM group and 17 in the FF group (table 2.3).
2.3.4 Clinical data
Gestational age was determined by the first day of the last menstrual period of the mother. This was confirmed either by an ultrasound examination during early pregnancy or a maturational assessment of the preterm infant with the help of the Dubowitz score (9). Data concerning clinical outcome within 24 hours after birth and neonatal clinical data were collected until discharge. The clinical data were mortality, the incidence of respiratory distress syndrome, the need for supplemental oxygen at 36 weeks postmenstrual age, the incidence of patent ductus arteriosis, the incidence of necrotizing enterocolitis, the number of proven septicaemias and the incidence of cerebral haemorrhage, ischaemic lesions, and ventriculomegaly.
Patent ductus arteriosus was diagnosed when clinical symptoms were confirmed by a cardiac ultrasound. Necrotizing enterocolitis was diagnosed by pneumatosis on an
abdominal radiograph and/or by findings during surgery. Cranial ultrasounds were carried out, using a 7.5 MHz transducer, before starting T4/placebo and on days 5, 14, 28 and 42 or more often if clinically indicated. Classification of haemorrhage was done as described by Volpe (10). Haemorrhagic venous infarction followed by cysts were classified as parenchymal haemorrhages. Ischaemic lesions were classified according to De Vries et al. (11). Classification of ventriculomegaly was performed according to Levene (12).
Assessment of overall cerebral ultrasound findings was done on all assessments made of the infant during the entire stay in our neonatal unit and was classified as follows: Normal: no
haemorrhage and no ischaemia and no ventricular dilatation; Moderately abnormal: a grade 1 or 2 haemorrhage and/or a grade 1 ischaemia and/or a grade 1 ventricular dilatation; Severely abnormal: a grade 3 or 4 haemorrhage and/or a grade 2 or 3 ischaemia and/or a grade 2 ventricular dilatation.
2.3.5 Administration of T4/placebo
For each infant entering the study a numbered 'blind' set of ampoules, containing 25 /tg/ml T4 or placebo, was prepared. Thyroxine supplementation was started 12-24 hours after birth in a daily, fixed dose of 8 /*g per kilogram birth weight. This dose was chosen on the basis of results of a pilot study (13). Trial medication was given by an intravenous injection
as long as intravenous nutrition was given (mean period of 14 days) and enterally
thereafter. The treatment period lasted 6 weeks.
2.3.6 Statistical analysis
The small number of mothers that chose not to express breast milk for their infant(s) resulted in a too small number of infants in the only formula feeding group for reliable statistics. Therefore we further analysed only the data of the maternal milk group. The number of infants available for research decreased progressively in time (due to the transfer to other hospitals). Therefore we used only the data collected before the eighth postnatal week and at corrected term age in our statistical analysis of physical and neurological development (chapters 4,5 and 6) (Figure 2.1). For analysis of macronutrient composition of maternal milk we used the samples collected in the first eight postnatal weeks (chapter 3) (Figure 2.1).
2.4 References
1. Van Wassenaer AG. Thyroxine supplementation in very preterm infants. Thesis, University of Amsterdam, the Netherlands, 1996.
2. Curzi-Dascalova L, Figueroa JM, Eiselt M, et al. Sleep state organization in premature infants of less than 35 weeks gestational age. Pediatric Res.
Study design 41
3. Curzi Dascalova L and Mirmiran M, (eds). Manual of Methods for Recording and Analyzing Sleep-Wakefulness States in Preterm and Full-term Infants.INSERM, Paris, 1996.
4. Curzi-Dascalova L, Peirano P, Morel-Kahn F. Development of sleep states in normal premature and full-term newborns. Dev Psychobiol 1988;21:431-444.
5. Prechtl HFR. The behavioral states of the newborn infant (a review). Brain Res 1974;76:185-212.
6. Ferrari F, Cioni G, Prechtl HFR. Qualitative changes of general movements in preterm infants with brain lesions. Early Hum Dev 1990;23:193-231.
7. Hadders-Algra, M, Klip-Van den Nieuwendijk AWJ, Martijn A, Van Eykern LA. Assessment of general movements: towards a better understanding of a sensitive method to evaluate brain function in young infants. Dev Med Child Neurol 1997;39:89-99.
8. Prechtl, HFR. Qualitative changes of spontaneous movements in fetus and preterm infant are a marker of neurological dysfunction (Editorial). Early Hum Dev 1990;23:151-158.
9. Dubowitz LMS, Dubowitz V, Goldberg C. Clinical assessment of gestational age in newborn infants. J Pediatr 1970;77:1-10.
10. Volpe JJ. Neurology of the newborn. 2nd ed. W.B. Saunders Company; 1987:p331. 11. De Vries LS, Eken P, Dubowitz LMS. The spectrum of leukomalacia using cranial
ultrasound. Behav Brain Res 1992;49:1-6.
12. Levene MI. Measurements of the lateral ventricles in preterm infants with real-time ultrasound. Arch Dis Child 1981;56:900-904.
13. Van Wassenaer AG, Kok JH, Endert E, Vulsma T, de Vijlder JJM. Thyroxine supplementation to infants of less than 30 weeks gestational age does not increase plasma triiodothyronine concentrations. Acta Endocrinol 1993;129:139-146.
