Thyroid storm is a hypermetabolic crisis seen in patients with untreated or undertreated Grave's disease, which carries a mortality rate of 30% even after early diagnosis and treatment.1, 2 We report an unusual case of intraoperative thyroid storm in a male patient with multinodular goiter undergoing total thyroidectomy even though he was clinically and biochemically euthyroid.
A 35-year-old man with toxic multinodular goiter, who was made euthyroid clinically and biochemically (free T4 1.01 ng/dL, free T3 1.8 pg/mL) with antithyroid drugs, was scheduled for total thyroidectomy. General anesthesia with endotracheal intubation under standard monitoring was induced intravenously with fentanyl (200 μg), propofol (150 mg), and vecuronium (8 mg), and maintained intravenously with morphine (8 mg), isoflurane, and N2O in O2 (1–2% and 60–66%, respectively), and ventilation was controlled. In the 3rd intraoperative hour during skin closure, his heart rate (80/min to 120/min), blood pressure (110/70 to 170/108 mmHg), temperature (36.2–39.3°C), and ETCO2 (35–65 mmHg) were observed to rise over 30 minutes. The CO2 absorber was warm to the touch. There was sweating without skin mottling and skeletal muscle rigidity. An arterial blood gas analysis revealed respiratory and metabolic acidosis. Based on these findings, thyroid storm was diagnosed. Propranolol (5 mg) and hydrocortisone (200 mg) were administered intravenously, and propylthiouracil (500 mg) was given enterally through the nasogastric tube. The patient was cooled with an ice pack, and the operation theater temperature was lowered. Controlled mechanical ventilation was continued with minute ventilation settings raised by increasing the respiratory rate. Urine from the indwelling urinary catheter was normal in terms of quantity and quality. Within 30 minutes, the patient's body temperature, heart rate, blood pressure, ETCO2, and arterial blood gas analysis started to normalize and eventually reached normal levels after the above treatment was continued in the intensive care unit for 2 hours. The trachea was extubated when the patient was fully conscious, and neuromuscular blockade was adequately reversed. The patient was closely monitored in the intensive care unit for 24 hours. The levels of thyroid hormones (free T4 = 1.9 ng/dl, free T3 = 3.8 pg/dl) and creatine phosphokinase (drawn during the episode) were found to be within normal limits.
Thyroid storm is almost always a clinical diagnosis, and no laboratory tests are diagnostic.3 There may be an increase in target cell beta adrenergic receptor density or postreceptor modification in signaling pathways in a thyroid storm.4 In our patient, the levels of free thyroid hormones were within normal limits during the episode, but both free T3 and T4 were relatively increased when compared with the preoperative values. This relative increase in the levels of hormones may have triggered the thyroid storm with exaggerated receptor or postreceptor signaling pathway response.
Thyroid storm, although a rare intraoperative complication in modern practice, can nevertheless occur. Our case serves to remind practitioners that thyroid storm can occur even in a patient who has been rendered euthyroid preoperatively. Therefore, anesthesiologists should keep a high degree of suspicion about euthyroid status and should be prepared for early recognition and management of thyroid storm in suspected patients.