prognostic utility of serum potassium in chronic digoxin toxicity a casecontrol study objective in contrast to patients with acute digoxin overdose the prognostic utility of the serum potassium concentration for patients with chronic digoxin toxicity is unclear in such patients we aimed to evaluate the relationship between pretreatment serum potassium and survivalmethods this was a casecontrol study at an urban poison control center affiliated with a large urban medical center we compared the serum potassium concentration between patients with chronic digoxin toxicity resulting in fatality cases over a 7year period 20002006 versus survivors controls over a 1year period 20072008results during the study period there were 13 fatalities cases and 13 survivors controls of whom seven cases and five controls received appropriately dosed digoxinspecific antibody fab fragments fab there were no statistically significant differences between cases and controls with respect to serum digoxin concentration creatinine age or sex serum potassium elevation prefab was significantly associated with fatality both in mean difference p003 and using a dichotomous cutoff of 50meql p0001 which performed with 92 sensitivity 95 ci 67 99 in 86 of deaths despite appropriate fab administration the clinical presentation included the combination of bradycardia plus hyperkalemiaconclusion in these patients with chronic digoxin toxicity elevated serum potassium was associated with fatality the combination of bradycardia and hyperkalemia strongly predicted fatality even in cases with appropriate fab administration