To assess the risk of developing transient decreases in thyroid hormone levels in infants after surgery with CPB and their impact on the early postoperative period, as well as to determine the necessity of including hormone replacement therapy with levothyroxine sodium in the treatment regimen for patients at high risk of postoperative thyroid hormone decline.

Methods:

A single-center prospective cohort study was conducted, analyzing 104 cases of surgical treatment for congenital heart defects under CPB in infants from 2014 to 2019. Patients were divided into two groups based on the type of congenital heart defect:

Group 1: Septal defects (55 infants, “acyanotic” defects, blood oxygen saturation >95%).

Group 2: Conotruncal defects (49 infants, “cyanotic” defects, blood oxygen saturation <85%).

To evaluate thyroid profiles, levels of thyroid-stimulating hormone (TSH), free thyroxine (T4), and free triiodothyronine (T3) were measured at three stages: preoperatively, 24 hours postoperatively, and 7–10 days postoperatively.

The study was carried out in two phases:

1. Without hormone replacement therapy.

2 .With hormone replacement therapy during the postoperative period.

Levothyroxine sodium was prescribed to infants on the first day after transfer from the ICU, with individual dosage calculated according to the drug’s instructions.

Results:

The majority of infants with both cyanotic and acyanotic defects had thyroid profiles within normal limits upon admission. In the early postoperative period, a decrease in thyroid hormone and TSH levels was observed.

Infants with free T3 levels below normal 24 hours postoperatively had longer CPB durations (p<0.05), longer aortic clamping times (p<0.05), and higher inotropic indices (p<0.05) compared to those with normal free T3 levels.

Hormone replacement therapy resulted in the following improvements:

• Reduced cardiotonic support volume (p<0.05)

• Decreased manifestations of circulatory failure (p<0.05)

• Fewer complications (p<0.05)

• Fewer medications required upon discharge (p<0.05)

• Increased proportion of patients discharged without requiring prescription medications (p<0.05)

Vlasova Maria completed Pirogov Russian National Research Medical University in 2011 and finished residency in the Federal State Budgetary Institution “Bakulev National Medical Research Center for Cardiovascular Surgery” of the Ministry of Health of Russia (Moscow); Still she work in the Department of Neonatal Reconstructive Surgery in Federal State Budgetary Institution “Bakulev National Medical Research Center for Cardiovascular Surgery” of the Ministry of Health of Russia (Moscow)