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

Background And Objectives: Cardiac surgery with cardiopulmonary bypass (CPB) is related to euthyroid disease or hypothalamic-pituitary-thyroid system depression. Abnormal hemodynamic status induced by CPB is responsible for several endocrine-metabolic changes, triggering complex systemic inflammatory response. This study aimed at evaluating triiodothyronine (T3), tetraiodothyronine (T4) and thyrotrophin (TSH) behavior in infants submitted to cardiac surgery with CPB.

Methods: Participated in this study 15 infants. Blood samples for T3, T4 and TSH evaluation were collected in four moments: M1 - after anesthetic induction; M2 - at surgery completion; M3 - six hours after surgery completion; M4 - 24 hours after M1. To complete this study the following parameters were evaluated: mean blood pressure (MBP), central blood temperature ( masculineC), tissue oxygenation and acid-base attributes (M1, CPB, M2, M3 and M4).

Results: The patients' means aged, weigh, height and body surface were 3.9 months; 4.708 kg; 0.65 m and 0.3 m(2) respectivety. Plasma T3 (p < 0.0001), T4 (p < 0.0001) and TSH (p = 0.0021) concentrations have significantly varied throughout the study with T3 concentrations progressively decreasing. Lowest T3 and T4 values were coincident with highest Ht and Hb values, discarding hemodilution effects. Highest serum TSH concentrations have shown a possible hypothalamic-pituitary-thyroid system reaction to hypothermia and of massive iodine absorption (topic use of antiseptic solutions). 'Low T3 Syndrome' aspects were identified in all studied moments.

Conclusions: There have been changes in serum T3, T4 and TSH concentrations in infants submitted to cardiac surgery with cardiopulmonary bypass.