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Extra iodine does not boost thyroid hormone in Liverpudlian preterm babies
Neonatal “sick thyroid” syndrome has perplexed neonatologists since it was recognised in the late 1970s. Apart from one very early study by Schonberger et al (Eur J Pediatr1981;135:245–53) showing a reduction in mortality when thyroxine was replaced, no benefits of giving thyroxine to preterm babies have been shown. The neonatal team in Liverpool decided to investigate the contribution of dietary iodine to thyroid function (page F86). Preterm babies have as much difficulty keeping pace with their iodine requirements as they do with other constituents of their diet, and most preterm formulas (and preterm breast milk) contain less iodine than some authorities recommend. Readers of this column will remember that in May this year we carried an article reminding readers of the potential dangers of large doses of iodine containing radio-opaque dyes (Arch Dis Child Fetal Neonatal Ed 2000;82:F215–17). Babies in this study were randomly allocated to receive an iodine supplemented formula or normal formula as supplementary feed (or as sole feed if the mother chose formula feeding). There was no difference in the thyroid hormone levels between the two groups; iodine status was not measured. The researchers concluded that there is no basis for increasing the amount of iodine in preterm formula milk. Presumably these results would also apply in Derbyshire, although workers in Spain have apparently suggested benefit.
Fluid restriction does not prevent chronic lung disease
CLD continues to afflict large numbers of ex-preterm infants, and it has been suggested that excess fluid intake makes a contribution. Kavvadia and colleagues randomised babies to a high or low fluid regimen, and took pains to measure the actual fluid intake during the trial (page F91). There was no difference in the outcome, perhaps because babies can cope with this degree of difference in water input if their renal function is reasonable.
Glucose levels in breast fed babies, and in those whose mothers needed valproate therapy
The box and whiskers plot in the paper by Hoseth and colleagues bears a marked resemblance to the now classic figure from Srinivasan et al (J Pediatr 1986;109:114–17), but is no less important (page F117). Normative data on blood glucose levels in healthy term babies are few and far between, perhaps because many ethics committees take a dim view of blood sampling in this group. These workers, from Denmark, did obtain the approval of their local committee and managed to recruit 223 normal, healthy, breast fed babies, who were studied once each at a time predetermined by randomisation. Ketone bodies were not measured. None of these babies had a blood glucose less than 2 mmol/l after the first hour, and none became symptomatic. Samples were collected post-feed, not pre-feed. The authors support the recommendations of the World Health Organisation (Williams 1997), namely that screening estimation of blood glucose is not indicated in healthy, breast fed, term infants of appropriate size for gestation. There were no cases of breast milk insufficiency in this group, in whom early breast feeding was encouraged. Ebbesen and co-workers discovered hypoglycaemia, unexpectedly, in babies whose mothers had required valproate treatment for epilepsy in pregnancy (page F124). These 22 pregnant epileptic Danish women received a great deal of attention (by UK standards), with monthly review by a neurologist and frequent measurements of antoconvulsant levels. Thirteen of their babies developed asymptomatic hypoglycaemia (<1.8 mmol/l), and four babies had repeated episodes.
Hazards of reinfusing “waste” blood into babies
Most of us think nothing of re-infusing the contents of the “waste” syringe back into the baby after taking a blood sample from an arterial line; in general we feel that this is a Good Thing because we are reducing the need for blood transfusion by minimising blood lost from the baby. Jackson and Derleth point out the potential hazards of this common practice (page F130). Diluted normal saline solution caused haemolysis in vitro, and the authors advise caution when choosing an infusion solution for arterial catheters.
Teething is normal in ex-preterm children
A hard working dentist in Finland examined 30 preterm children and 60 control children, and found that teething was not delayed in the ex-preterm group (page F104). Parents often ask about teething, and you can now tell them with confidence that the time the first tooth is likely to erupt is nine months, with a range from five to 17 months. For once, girls were later developers than boys, with a delay of about two months in teething.
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