Sinus node dysfunction in a patient with lithium intoxication

Lithium can suppress sinus node function, especially when it is used concom itantly with carbamazepine. We describe a 42-year-old woman who took lithiu m and carbamazepine for manic-depressive psychosis and seizure disorders, a nd developed marked sinus node dysfunction. Drug screening showed a toxic s erum lithium level of 3.38 mmol/L and a normal serum carbamazepine level of 2.1 mu mol/L. An electrophysiologic study showed prolongation of the corre cted sinus node recovery time (CSNRTT) of up to 9,708 msec. After three ses sions of hemodialysis, normal sinus rhythm xas resumed. The serum lithium l evel was 0.1 mmol/L 2 weeks later, and the CSNRT shortened to 309 msec. Bec ause the combination of lithium and carbamazepine in psychiatric patients i s not uncommon; recognition of the potential complication of severe bradyar rhythmia is essential in the emergency care of such patients.