Monitoring digoxin therapy: The use of plasma digoxin concentration measurements in the diagnosis of digoxin toxicity
Aronson JK., Grahame-Smith DG., Wigley FM.
The usefulness of measuring plasma digoxin concentrations in the diagnosis of digoxin toxicity has been assessed in 83 in-patients. the mean plasma digoxin concentration in clinically toxic patients was significantly higher than the mean concentration in non-toxic patients. the overlap between the groups, however, was extensive and could partly be accounted for by hypokalaemia in those toxic patients whose plasma digoxin concentration was less than 3 ng/ml. there was, in addition, a higher incidence of hyperkalemia, without obvious cause, in toxic patients than in non-toxic patients. consideration of the incidence of various non-cardiac factors, specifically plasma potassium concentration > 5.0 mmol/1, plasma creatinine concentration > 150 µmol/1, daily maintenance dose > 6 µg/kg, and age > 60 years, led to the development of guidelines to aid in the diagnosis of digoxin toxicity. patients with plasma digoxin concentration > 3 ng/ml or with hypokalaemia should be considered probably toxic and those with plasma digoxin concentration ≤ 3 ng/ml in the absence of hypokalaemia should only be considered toxic if they have at least two of the non-cardiac factors outlined above. plasma digoxin concentrations could not be predicted with more than 31 per cent certainty by considering the magnitude of those non-cardiac factors. © 1978, Oxford University Press.