[Thyroid function profile in infants submitted to cardiac surgery with cardiopulmonary bypass.]

Area of Science:

• Pediatric Endocrinology
• Cardiovascular Surgery
• Thyroid Physiology

Context:

• Cardiac surgery with cardiopulmonary bypass (CPB) can induce significant endocrine-metabolic alterations.
• CPB-induced hemodynamic changes trigger complex systemic inflammatory responses.
• Infants are particularly vulnerable to these perioperative endocrine disruptions.

Purpose:

• To evaluate the dynamic changes in triiodothyronine (T3), tetraiodothyronine (T4), and thyrotropin (TSH) levels in infants undergoing cardiac surgery with CPB.
• To correlate thyroid hormone fluctuations with hemodynamic and metabolic parameters during and after CPB.
• To identify the occurrence of "Low T3 Syndrome" in this pediatric surgical population.

Summary:

• Fifteen infants undergoing cardiac surgery with CPB were monitored for T3, T4, and TSH levels at four time points: pre-induction, post-surgery, 6 hours post-surgery, and 24 hours post-surgery.
• Significant variations in T3, T4, and TSH concentrations were observed, with a progressive decrease in T3 levels throughout the study.
• Lowest T3 and T4 levels correlated with higher hematocrit and hemoglobin, ruling out hemodilution, while elevated TSH suggested a hypothalamic-pituitary-thyroid axis response to hypothermia and iodine absorption.

Impact:

• Demonstrates significant alterations in thyroid hormone profiles in infants following CPB, characterized by a "Low T3 Syndrome."
• Provides crucial insights into the hypothalamic-pituitary-thyroid system's response to the physiological stress of pediatric cardiac surgery.
• Highlights the need for careful monitoring and potential therapeutic strategies for thyroid dysfunction in infants undergoing CPB.