The effects of thyroid hormones and interleukin-8 levels on prognosis after congenital heart surgery

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.