Thyroid Hormone Alterations Following CPB

IntroductionCardiac diseases managed with surgery are growing increasingly because of technologic progress and sedentary lifestyles on one hand and progression of diagnostic procedures on the other. Thyroid dysfunction and alterations in thyroid hormones have a direct effect on the cardiovascular system, and special attention to this issue is required to counter the effects of these two systems (thyroid hormones and cardiovascular system) on each other, especially during and after cardiac surgery and resultant thyroid hormone alterations due to surgery. Frequent use of cardiopulmonary bypass (CPB) during cardiac surgical procedures makes this issue very important. The goal of this research is to study thyroid hormone alterations after cardiopulmonary bypass and its effect on hemodynamic parameters and weaning time of patients from ventilatory support after cardiac surgery. MethodsSixty patients undergoing CPB who had no previous history of thyroid disease and who did not have any diseases affecting weaning time from ventilator were studied. Thyroid hormone levels were measured before and after CPB, and hemodynamic parameters (including mean arterial pressure, heart, HR, rate and central venous pressure, CVP) were measured every 5 minutes in the operating room and every 15 minutes in the ICU. The time of patient arrival to the ICU until extubation of the patient (after meeting the criteria of extubation) was measured in minutes, and the relations between the variables were studied. ResultsAmong all the variable parameters, the correlation between free T3 (FT3) and CVP after discontinuing CPB; TSH alterations and heart rate at arrival to ICU; and TSH alterations and time-to-extubation of the patient were statistically meaningful (P<O.O5). Except for the relation between TSH alterations and HR upon arrival to the ICU, the others had “low predictive value” and the latter had “medium predictive value”. ConclusionThyroid hormones differ after CPB, and this difference has correlations with hemodynamic parameters and time-to-extubation of the patient (weaning time) (Iranian Heart Journal 2006; 7 (1): 21-24).