Digoxin Toxicity Flashcards
Onset of acute digoxin toxicity
Minutes to several hours
Symptoms of acute digoxin toxicity
Can be asymptomatic, but symptoms include N/V, abdominal pain, lethargy, confusion, weakness
Caveat about chronic digoxin toxicity
Can be difficult to diagnose
Chronic digoxin toxicity symptoms
Loss of appetite, weakness, anorexia, N/V, abdominal pain, weight loss, delirium, confusion, drowsiness, HA, hallucinations, visual disturbances, seizures (rarely)
What electrolyte abnormality should you watch out for in digoxin toxicity and why?
HYPERKALEMIA, because it’s an indication for DigiFab treatment!
Digoxin toxicity symptoms: cardiac abnormalities
cardiac dysrhythmias including ventricular tachydysrhythmias and bradydysrhythmias
The cardiac dysrhythmias are due to what?
Sensitized myocardium and depressed AV node
Examples of cardiac dysrhythmias in digoxin toxicity
atrial flutter, afib with AV block, non-sustained ventricular tachycardia, high-degree AV block, junctional tachycardia, sinus bradycardia
Diagnostic tests for digoxin toxicity
Digoxin serum concentrations, BMP with calcium and magnesium, blood gas, ECG, thyroid function tests, med list for DDIs
How long should you wait to obtain digoxin serum concentrations to ensure accuracy?
At least 6 hours
Total therapeutic range for digoxin
0.5-2ng/ml
What will give false positive results of digoxin toxicity?
Bilirubin and spironolactone
GI decontamination in digoxin toxicity: treatment
AC 1g/kg q2-4h up to 4 doses
Purpose of AC in digoxin toxicity
Prevents reabsorption from the GI tract and reduces half-life
When to use AC in digoxin toxicty
If definitive therapy with digoxin-specific Fab isn’t immediately available or if AKI
If a patient with digoxin toxicity has hypokalemia or hyperkalemia, what should you NOT administer and why?
Calcium, because it can exaggerate the cardiac effects and lead to the stone heart phenomenon
What can you administer for hyperkalemia?
IV insulin and sodium bicarb IF DigiFab won’t be administered immediately
What can you administer for hypomagnesemia in a patient with digoxin toxicity?
mag sulfate 2gm IV over 20 minutes followed by 1-2g/hr PRN
Indications for DigiFab
Life-threatening dysrhythmia regardless of serum concentration
Potassium concentration >5mEq/L in digoxin toxicity
Chronic elevations of serum digoxin concentrations with dysrhythmias, GI symptoms, or AMS
Serum digoxin concentration of >15mg/ml anytime after ingestion or >10ng/ml after 6 hours
Acute ingestion of 10mg of digoxin in an adult
MoA of DigiFab
free digoxin in the intravascular and interstitial space is bound by the antigen-binding fragments
The movement of free intracellular and dissociated digoxin into the interstitial or intravascular space is due to what?
The concentration gradient
What happens to the free digoxin concentrations with DigiFab?
It decreases
What happens to the total serum digoxin concentrations with DigiFab?
It increases
What happens to renal CL with DigiFab?
It increases
What happens to serum potassium concentrations with DigiFab?
It decreases
Empiric DigiFab dosing for chronic toxicity
3-6 vials
Empiric DigiFab dosing for acute toxicity
10 vials
DigiFab formula for known serum concentration
[serum digoxin concentration (ng/ml) * patient weight (kg)]/100 = # of vials
DigiFab formula for known amount ingested
[amount ingested (mg) / 0.5 (mg/vial)] * 80% bioavailability = # of vials
Other cardiac therapies for digoxin toxicity: when to use atropine
Early bradydysrhythmias
Atropine dosing
0.5mg IV push repeated q5min
Other cardiac therapies for digoxin toxicity: when to use phenytoin and lidocaine
Ventricular dysrhythmias
Phenytoin dosing for digoxin toxicity
100mg (50mg/min) q5min until dysrhythmia is controlled or until 1,000mg; maintenance dose of 100mg IV q8h until digoxin toxicity has resolved
Lidocaine dosing for digoxin toxicity
1-1.5mg/kg IV bolus followed by a continuous infusion of 1-4mg/min
Other cardiac therapies (non-pharmacological) for digoxin toxicity
Pacemakers, cardioversion
