OBJECTIVES: We evaluated the effects of thyroid hormone levels and interleukin-8 
levels on prognosis in patients undergoing congenital heart surgery under 
cardiopulmonary bypass (CPB).
STUDY DESIGN: The study included 41 consecutive children (19 boys, 22 girls; 
mean age 3.4 ± 3.1 years; range 0.3 to 12 years). The patients were divided into 
two groups based on the presence or absence of postoperative low cardiac output 
state (LCOS). The definition of LCOS included oliguria, tachycardia, metabolic 
acidosis, and increased plasma lactate level. Plasma total (tT4) and free (fT4) 
thyroxine, total (tT3) and free (fT3) triiodothyronine, thyroid stimulating 
hormone (TSH), and interleukin-8 (IL-8) levels were measured preoperatively and 
at 48 hours postoperatively.
RESULTS: Postoperatively, nine patients (22%) developed LCOS. While the two 
groups were similar with respect to preoperative levels of thyroid hormones, 
lactate, and IL-8, postoperative tT3 and fT3 levels were significantly lower, 
and lactate and IL-8 levels were significantly higher in the LCOS group 
(p<0.05). In correlation analysis, postoperative IL-8 level showed significant 
correlations with CPB time (r=0.66), duration of mechanical ventilation 
(r=0.68), and inotropic requirement (r=0.59) (for all p<0.001). On the other 
hand, LCOS was significantly correlated with the following: preoperative tT4 
(r=-0.32, p=0.043) and postoperative fT3 (r=-0.44, p=0.004) levels, duration of 
mechanical ventilation (r=0.56, p<0.001), intensive care unit stay (r=0.45, 
p=0.003), and cross-clamp time (r=0.43, p=0.005). Regression analysis showed 
preoperative level of tT4 as the independent predictor of LCOS (t=-2.092, 
p=0.045). Mortality occurred in four patients (9.8%) in the early postoperative 
period, all of whom were in the LCOS group.
CONCLUSION: Our findings suggest that the development of LCOS after congenital 
heart surgery is associated with decreased total and free T3, and increased IL-8 
levels at 48 hours, and preoperative tT4 level is an independent predictor of 
LCOS.