Age-related differences in digoxin toxicity and its treatment

Development and validation of a risk prediction nomogram for serious arrhythmias in acute digoxin toxicity among pediatrics: A multicenter study

Digoxin is a cardiac glycoside obtained from the leaves of the foxglove plant, Digitalis lanata. Several studies have described the safety of digoxin including various life-threatening events, notably cardiac arrhythmias. Early identification of high-risk patients and subsequent initiation of the utmost medical care are associated with a better prognosis. The assessment of serum digoxin levels, which is not always convenient, is the only tool used to evaluate the severity of digoxin exposure. However, the feasibility of this tool, particularly in resource-restricted countries, remains unclear. Therefore, the current study aimed to establish and validate a feasible alternative tool, a bedside nomogram, to identify pediatric patients diagnosed with acute digoxin intoxication who are at risk of developing serious arrhythmias. This was a two-phase, multicenter, retrospective study. The prevalence of serious arrhythmias was approximately 17%. Patients diagnosed with serious arrhythmias showed significantly higher serum digoxin, random blood glucose, and potassium levels but lower sodium, magnesium, and hemoglobin levels. Serious arrhythmias were associated with significantly lower P-R intervals, shorter QTc intervals, and more frequent digoxin effects (p < 0.05). The proposed nomogram showed that combining age and initial random blood glucose, sodium, and potassium levels could predict the future incidence of serious arrhythmia with an accuracy of 96.2% (sensitivity = 94.4%, specificity = 96.5%), an area under the curve (AUC) of 0.977, and p < 0.001. Validation of the proposed nomogram yielded an AUC for the nomogram probability of approximately 81%, and the AUC for the predicted probability using the developed model was 98.3%, indicating that both the validated model and the developed nomogram were significant predictors of serious arrhythmia. The utility of using the four-factor nomogram to determine the risk of serious arrhythmia in children exposed to an overdose of digoxin is comparable, if not superior, to the serum digoxin level.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Antiarrhythmics

OBJECTIVE

Arrhythmias are a common occurrence in critically ill pediatric patients. Pharmacotherapy is a usual modality for treatment and prevention of arrhythmias in this patient population. This review will highlight particular arrhythmias in the pediatric critical care population and discuss salient points of pharmacotherapy of these arrhythmias. The mechanisms of action for the various agents, potential adverse events, place in therapy, and evidence for their use will be summarized.

DATA SOURCES

The literature was searched for articles related to the topic. Expertise of the authors and a consensus of the editors were additional sources of data in the article.

DATA SYNTHESIS

The author team synthesized the current pharmacology and recommendations and present them in this review. Tables were generated to summarize the state of the art evidence-based practice.

CONCLUSION

Specialized knowledge as to the safe and effective use of the antiarrhythmic pharmacotherapy in the intensive care setting can lead to safe and effective rhythm management in patients with complex heart disease.

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 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.

Fab antibody fragments: some applications in clinical toxicology

This review provides current information on the use of antigen-binding fragments (Fab) from cleaved antibodies to treat poisoning with digoxin and other potent, low formula mass poisons, such as colchicine and tricyclic antidepressants. Anti-digoxin Fab fragments have been used successfully for many years in the management of severe poisoning with digoxin, digitoxin, and a range of other structurally related compounds, including cardiotoxins from Nerium and Thevetia sp. (oleander) and Bufo sp. (toads). However, their main use remains treating digoxin poisoning. Equimolar doses of anti-digoxin Fab fragments completely bind digoxin in vivo. The approximate dose of Fab fragments (mg) is 80 times the digoxin body burden (mg). If neither the dose ingested nor the plasma digoxin/digitoxin concentration is known, in an adult 380 mg of anti-digoxin Fab fragments should be given. The dose for elderly patients or those with renal impairment should be similar to that for those with normal renal function. Fab fragments have a plasma half-life of 12-20 hours, but this can be prolonged in patients with renal impairment. Analysis of serum ultrafiltrate using an immunoassay shown not to have matrix bias remains the most accurate approach to measuring free digoxin in the presence of anti-digoxin Fab fragments. The antibody fragments are given intravenously over 15-30 minutes after dilution to at least 250 mL with plasma protein solution, 0.9% (w/v) sodium chloride, or deionised water, except in infants where the volume infused can be reduced. Factors limiting the efficacy of Fab fragments are the dose, the duration of the infusion and any delay in administration. Guidelines for Fab fragment administration in children include (i) dilution to a final Fab concentration of 10 g/L in either 5% (w/v) dextrose or 0.9% (w/v) sodium chloride; (ii) infusion through a 0.22 microm filter; (iii) administration of the total dose over a minimum of 30 minutes; and (iv) avoiding coadministration of other drugs and/or electrolyte solutions. Fab fragments are generally well tolerated. Adverse effects attributable to Fab treatment include hypokalaemia and exacerbation of congestive cardiac failure; renal function could be impaired in some patients. Fab fragment preparations for treating acute colchicine and tricyclic antidepressant poisoning have been developed, but are not available commercially. Colchicine poisoning is rare in Western countries, and pharmacological management together with supportive care is usually effective even in severe tricyclic antidepressant overdosage. Attempts have been made to produce anti-paraquat antibodies capable of enhancing paraquat elimination from the lung, but thus far all such attempts have proved unsuccessful.

Therapeutic drug monitoring in drug overdose

The treatment of poisoned patients is still largely defined by history, clinical assessment and interpretation of ancillary investigations. Measurement of drug concentrations is clinically important for relatively few compounds. Most measurements form an adjunct to and should not be considered a substitute for clinical assessment. Drug concentrations are particularly important for those compounds where the concentration is predictive of serious toxicity in an otherwise asymptomatic patient.

Digoxin toxicity presenting as encephalopathy

We describe two cases of digoxin toxicity presenting with clinical and electroencephalographic evidence of encephalopathy without other features of digoxin toxicity.

Therapeutic drug monitoring in pediatrics: a need for improvement

Therapeutic drug monitoring (TDM) is practiced for a number of frequently used drugs in infants and children. It is believed that monitoring drug levels will increase the probability of a therapeutic response and minimize the probability of adverse drug sequelae. Dose adjustments are based on measured drug levels interpreted relative to published therapeutic ranges which may or may not reflect the true relationship with either therapeutic or adverse effects. Potential errors derive from many sources, some amenable to solutions based on current knowledge, others awaiting improved understanding of the causes and consequences of unreliable therapeutic ranges.