Levothyroxine Sodium Administration and Late Circulatory Collapse in Premature Infants with Thyroid Dysfunction

Objective: Levothyroxine sodium (LT4) is considered safe, and widely administered to premature infants with thyroid dysfunction. Late circulatory collapse (LCC) has not been defined clearly, but it has been characterized as refractory hypotension in premature infants. Recently, LCC after LT4 administration was reported in Japan. However, there is controversy on the aspect of LT4 as a risk factor of LCC. The purpose of this study was to investigate relations between LT4 administration and LCC in premature infants. Methods: We retrospectively reviewed medical records of premature infants (≤32 weeks gestation) admitted in Gyeongsang National University Hospital between 2011 and 2018. To investigate the relation between LT4 supplementation and LCC, clinical and laboratory findings were reviewed and compared between premature infants with and without LCC. Results: Among 347 premature infants, LCC occurred in 21 (6.1%) on median 19.0th day. Sixteen (76.2%) of 21 infants with LCC were receiving LT4 and LCC was developed on median 3.0 days after LT4 initiation. Gestational age ≤28 weeks, birth weight <1.5 kg, hemodynamically significant patent ductus arteriosus, culture proven sepsis, necrotizing enterocolitis, congenital hypothyroidism, use of LT4 and diuretics, values of serum thyroid stimulating hormone, free thyroxine and sodium were significantly statistically different between LCC and no LCC group. Prematurity ≤28 weeks of gestation and LT4 replacement were risk factors of LCC on multivariate logistic regression analysis. Conclusion: Supplementation of LT4 should be carefully considered in premature infants with thyroid dysfunction and serial monitoring of blood pressure should be warranted if LT4 was administered.