Feasibility and normal values of an integrated conductivity (Nanoduct™) sweat test system in healthy newborns.

BACKGROUND: Nanoduct™ is a simple and practical sweat analysis system measuring conductivity in situ. It requires only three microlitres of sweat, making it especially applicable to newborns. METHODS: We measured conductivity in 260 healthy term infants at the age of four days, and again at four weeks to determine the proportion of successful tests, test duration, and normal values for sweat conductivity in newborns. RESULTS: Sufficient sweat was collected in 159/260 of four-day olds (61%), and in 225/239 of four-week olds (94%). Mean (sd) test duration was 27 (5) and 25 (5) min. Mean (sd, range) conductivity was 53mmol/l (16, 8-114) at age four days, and 36 (9, 12-64) at four weeks. CONCLUSIONS: Determination of sweat conductivity using Nanoduct™ cannot be recommended for four-day old newborns. However, at the age of four weeks the success rate is high (94%), and conductivity values at that age are comparable to older healthy children.

Lethargy in a newborn: lithium toxicity or lab error?

Lithium medication during pregnancy is uncommon and the problems of a neonate who has been exposed to lithium represents a rare situation in neonatology. The clinical presentation and management of a newborn whose mother received lithium during pregnancy is presented. The newborn manifested a four day course of lethargy with unexplained high lithium levels in the adult toxic range. The infant improved clinically under intravenous hydration therapy, nevertheless lithium serum levels increased again and we did not know for certain if our clinical instinct or the actual figures were correct. Finally we noticed that our confusion had resulted from test tubes containing lithium heparine.