Serum digoxin concentrations and clinical signs and symptoms of digoxin toxicity in the paediatric population

Background Serum digoxin levels have limited utility for determining digoxin toxicity in adults. Paediatric data assessing the utility of monitoring serum digoxin concentration are scarce. We sought to determine whether serum digoxin concentrations are associated with signs and symptoms of digoxin toxicity in children. Methods We carried out a retrospective review of patients <19 years of age who received digoxin and had serum digoxin concentrations assessed between January, 2007 and June, 2013. Data collection included patient demographics, digoxin indication, serum digoxin concentrations, signs and symptoms of digoxin toxicity, electrocardiograms, and co-morbidities. Reviewers performing chart review and electrocardiogram analysis were blinded to digoxin levels. Descriptive statistical methods were used and comparisons were made between patients with and without toxic serum digoxin concentrations (>2 ng/ml). Results There were 87 patients who met study criteria (male 46%, mean age 8.4 years). CHD was present in 67.8% and electrocardiograms were performed in 72.4% of the patients. The most common indication for digoxin toxicity was heart failure symptoms (61.5%). Toxic serum digoxin concentrations were present in 6.9% of patients (mean 2.6 ng/ml). Symptoms associated with digoxin toxicity occurred in 48.4%, with nausea/vomiting as the most common symptom (36.4%), followed by tachycardia (29.5%). Compared with those without toxic serum digoxin concentrations, significantly more patients with toxic serum digoxin concentrations were female (p=0.02). The presence of electrocardiogram abnormalities and/or signs and symptoms of digoxin toxicity was not significantly different between patients with and without serum digoxin concentrations (p>0.05). Conclusion Serum digoxin concentrations in children are not strongly associated with signs and symptoms of digoxin toxicity.