Anaesthetic implications of a case of hyperthyroidism detected during the closure of an atrial septal defect.

A woman in her mid-20s who was clinically euthyroid presented with an ostium secondum atrial septal defect for closure. Preoperatively, heart rate ranged from 80 to 110 beats per minute. On the day of surgery, heart rate was 120 beats per minute, which settled after induction. During ultrasound guided central line access, a thyroid swelling was noticed. 20-30 min after commencement of the surgery, heart rate increased up to 130 beats per minute. Since other causes of tachycardia was ruled out, an intraoperative blood sample for thyroid function test was sent. Esmolol was kept ready in case the swelling turned out to be hyperfunctioning thyroid nodule. Post bypass, the patient again developed tachycardia. The thyroid function test showed elevated T3, T4 and a mildly elevated TSH (Thyroid stimulating hormone) value, consistent with an extrathyroid source. The patient is on long-term follow-up under an endocrinologist. Postoperatively, she is again euthyroid and heart rates have settled to less than 100 beats per minute.