Dynamic Change of Thyroid Hormones With Postmenstrual Age in Very Preterm Infants Born With Gestational Age <32 Weeks: A Multicenter Prospective Cohort Study

BackgroundAt present, the relationship between thyrotropin (TSH) and free thyroxine (FT4) in relation to postmenstrual age (PMA) in preterm infants is still unclear, and there is no reliable standard thyroid hormone reference ranges, resulting in different diagnostic criteria for congenital hypothyroidism been used by different newborn screening programs and different countries.ObjectivesTo investigate the relationship between TSH/FT4 and PMA in very preterm infants (VPIs) born with gestational age (GA) <32 weeks and to derive thyroid function reference charts based on PMA.MethodsA prospective cohort study was performed on VPIs born with GA<32 weeks and born in or transferred to the 27 neonatal intensive care units from January 1, 2019 to December 31, 2019. Serial TSH and FT4 values were measured at the end of each week during the first month after birth and also at PMA36 weeks, PMA40 weeks and at discharge, respectively. The 2.5th, 5th, 50th, 95th, and 97.5th percentiles of TSH and FT4 of different PMA groups were calculated to draw the percentile charts based on PMA.Results1,093 preterm infants were included in this study. The percentile charts of TSH and FT4 levels based on PMA were drawn respectively, and the result indicated that the percentile charts of TSH values were gradually increased initially and then decreased with increasing PMA. The 97.5th percentile chart reached the peak at PMA30 weeks (17.38μIU/ml), and then decreased gradually, reaching the same level as full-term infants (9.07μIU/ml) at PMA38–40 weeks. The 2.5th percentile chart of FT4 was at its lowest point at PMA26–27 weeks (5.23pmol/L), then increased slowly with PMA and reached the same level as full-term infants at PMA38–40 weeks (10.87pmol/L). At PMA36 weeks, the reference intervals of the 2.5th to 97.5th percentiles of TSH and FT4 were 1.18–12.3μIU/ml and 8.59–25.98pmol/L, respectively.ConclusionThe percentile charts of TSH and FT4 in VPIs showed characteristic change with PMA. The results prompt that age-related cutoffs, instead of a single reference range, might be more useful to explain the thyroid function of VPIs. And repeated screening is necessary for preterm infants.

Download Full-text

Pulse Oximetry Values in Very Preterm infants Asymtomatic at 34-36 weeks post menstrual age.

10.22541/au.160726775.54268285/v1 ◽

2020 ◽

Author(s):

Ignacio Oyarzún ◽

Marcela Diaz ◽

Paulina Toso ◽

Alejandra Zamorano ◽

Soledad Montes ◽

...

Keyword(s):

Pulse Oximetry ◽

Preterm Infants ◽

Premature Infants ◽

Gestational Age ◽

Oxygen Therapy ◽

Healthy Children ◽

Multicentric Study ◽

Very Preterm Infants ◽

Very Preterm ◽

Postmenstrual Age

Background: Oxygen supplementation is an important component for preterm infants neonatal care. Pulse oximetry (SpO2) is essential to guide oxygen therapy. Evidence on SpO2 values in premature infants previous to discharge is limited. Objectives: To establish SpO2 values in asymptomatic premature infants at 34, 35, and 36 weeks postmenstrual age (PMA). Methods: Longitudinal, multicentric study. From May 2018 to May 2019 premature infants born ≤32 weeks gestational age, from three level III NICUs in Santiago, Chile (altitude 579mt), were enrolled. Healthy children without current apnea of prematurity were included. Continuous SpO2 was obtained with Masimo-Radical 7/8 (USA), averaging time 2-4 seconds. Results: 101 SpO2 recordings (n = 44, 33 and 24 at 34, 35 and 36 weeks PMA respectively) from 62 infants. Twenty eight (45%) male, median (range) gestational age at birth 30 (26-32) weeks, median (range) birth weight 1480 (785-2700) g. Oximetry variables for total recordings: mean SpO2, median (range) 96.9 (93.3-99.3); minimum SpO2, median (range) 74 (51-89); time of SpO2 <90%, median (range) 2% (0-10.6%); time of SpO2 <80%, median (range) 0.1% (0-1.3%); desaturation event by ≥4% (DI4) ≥ 0 and ≥ 10 seconds per sample hour, median (range) 45.2 (5.2-115) and median (range) 15 (3.5-62.5) respectively; desaturation event <80% (DI80), median (range) 0.58 (0-10.8). We found no differences between SpO2 values at different weeks PMA. Conclusions: We described SpO2 values in very preterm infants, asymptomatic at 34, 35 and 36 weeks PMA. These values could be used as a reference to guide oxygen therapy previous to discharge.

Download Full-text