Sodium nitroprusside infusion prevents hypothyroidism in patients undergoing coronary artery bypass grafting: a prospective randomized clinical trial.

Objective: The level of thyroid hormones is an important factor in determining the outcome of coronary artery bypass patients. Sodium nitroprusside (SNP) is a natural donor of nitric oxide which has been shown to interfere with thyroid hormone synthesis. Whether clinical use of sodium nitroprusside has any effect on thyroid function has not yet been investigated. The aim of this study was to investigate the effects of SNP administration on circulating levels of thyroid hormones.

Methods: One hundred and six consecutive patients who underwent coronary artery bypass grafting operation were prospectively randomized to receive continuous infusions of either SNP or saline limited to the rewarming time of cardiopulmonary bypass (CPB). Free triiodothyronine (T3), total T3, free thyroxine (T4), total T4 and thyroid-stimulating hormone (TSH) levels were analyzed.

Results: Free T3, TSH and albumin changes of SNP and control groups were statistically different from each other. In the SNP group, free T3 values stayed in the euthyroid range between CPB and post-CPB periods, the period when SNP was infused, whereas it continued to decline to hypothyroidic levels in the control group. In addition, in the SNP group, an elevation in TSH levels was observed during the CPB period. Postoperatively, an earlier restoration of free T3 and TSH levels was observed in the SNP group when compared to the control group.

Conclusion: In this study, administration of SNP during cardiopulmonary bypass is shown to regulate free T3 and TSH levels positively.