[A case of atropine-resistant bradycardia in a patient on long-term lithium medication].

A 44-year-old woman was scheduled for laparoscopic cholecystectomy and partial thyroidectomy. She had received lithium, 400-1200 mg daily, and other antidepressants for 10 years for her depressive disorder. Preoperative examination revealed a swelling of the right thyroid associated with hypothyroidism. Her heart rate was in the range of 45-70 min-1 preoperatively. After induction of anesthesia with propofol 50 mg, and fentanyl 100 micrograms, heart rate decreased to 36 min-1 and remained low after tracheal intubation. Atropine sulfate 1.1 mg in divided doses, and ephedrine 4 mg i.v. did not change the heart rate. However, a bolus of isoproterenol 0.02 mg i.v. increased the heart rate to 95 min-1. We suspect that atropine-resistant bradycardia was due to sinus node dysfunction produced by interaction of chronic lithium treatment, fentanyl and propofol. Therefore, an intractable sinus node dysfunction may occur in a patient in whom lithium is given chronically, particularly in whom hypothyroidism is associated. In such a patient, a beta-adrenergic stimulant may be effective in treating bradycardia.