This is a report of a rare presentation of primary node dysfunction in a patient about to undergo thyroidectomy. A 40-year old female patient had been prepared with propanolol for thyroidectomy. In the operating room, on receiving intravenous atropine, she immediately went into asystole sinus arrest and arrhythmia with severe bradycardia. She responded to basic resuscitative measures and the operation was postponed. Following cardiologial and neurological evaluation, she was deemed fit to undergo thyroidectomy for a goitre compressing the trachea. A week later, she underwent thyroidectomy. Postoperative follow up was uneventful.
The mechanism of complete autonomic blockage and the resulting sinus node dysfunction is discussed. Propanolol and atropine block the sympathetic and parasympathetic systems respectively. In a normal heart such blockade does not usually create problems, as the heart will beat at its own fast intrinsic rate of about 100 beats/minute. In contrast, if there is underlying primary node dysfunction or sinoatrial disease, there may be a severe bradycardia and possible complete arrest. The authors advise caution and an awareness of the possibility of such autonomic blockade occurring in a patient about to undergo thyroidectomy.
