Emergency management of digitalis toxicity

1. DIGITALIS GLYCOSIDE TOXICITY
BY: DR.AISHWARYA TD
MODERATOR: DR.SHRUTHI

2. INTRODUCTION
• Digitalis is a plant-derived cardiac glycoside commonly used in the
treatment of chronic heart failure (CHF), atrial fibrillation, and re-entrant
supraventricular tachycardia.
• Cardiac glyosides are found in certain flowering plants, such as oleander
and lily-of-the-valley.
• Indigenous people in various parts of the world have used many plant
extracts containing cardiac glycosides as arrow and ordeal poisons.

3. MECHANISM OF ACTION
Direct and indirect effects resulting in:
• increased inotropy (mild effect).
• increased automaticity.
• negative dromotropy (slowing of AV conduction).
• increased vagal tone.
DIRECT:
inhibition of Na/K ATPase on the cell surface.
-> increased intracellular Na+ and increased extracellular K+.
-> increased intracellular Ca2+ due to Na+/Ca2+ antiporter.
-> calcium-mediated inotropy and increased automaticity, as well as negative
dromotropy due to decreased intracellular K+.

4. THERMOKINETICS
• Absorption – good oral absorption with oral bioavailability of
80% and peak levels at 6 hours.
• Distribution – 30% protein bound, Vd 10L/kg (higher in the
elderly and obese).
• Metabolism – minimal hepatic metabolism.
• Elimination – 60% renal, t ½ of 30-40 h, longer in renal failure.

5. CLINICAL FEATURES

6. DIAGNOSIS
• In patients with heart failure and normal renal function: daily Digoxin
doses- 125 to 250mcg .
• Fatalities: acute ingestion of 10mg in adults, 4mg in children.
• Screening : ECG
• Specific: serum potassium and digoxin levels.
• Acute: perform at 4 hours post-ingestion and then every 4 hours until
definitive treatment or toxicity has resolved.
• Chronic: perform levels 6hours of post last dose, to monitor steady state
level. levels can be misleading as levels near the therapeutic range 0.5-
2.0ng/ml(1.0-2.6nmol/L) correlate poorly with severity of intoxication.

7. ECG:
• The most common arrhythmias in digoxin toxicity are
premature ventricular contractions and bradycardic rhythms.

8. Four specific findings:
• Flattening or inversion of T wave.
• QT- interval shortening.
• Scooped depression of ST segment/Salvador Dali’s moustache”
• Increased U wave amplitude.

9. Additional ECG Features
• Mild PR interval prolongation,
up to 240 ms (due to
increased vagal tone)
• Prominent U waves.
• Peaking of the terminal
portion of the T waves.
• J point depression (usually in
leads with tall R waves).
NOTE: The presence of digoxin effect on the ECG is not a marker of digoxin toxicity. —
it merely indicates that the patient is taking digoxin.

10. MANAGEMENT
Resuscitation:
• Attend to life-threats resulting from dysrhythmias and hyperkalaemia.
• Digoxin-induced cardiotoxicity is refractory to standard measures.
• Bradyarrhythmias:
– Digibind( Digoxin specific antibody fragments) is the definitive
treatment.
– Atropine: 0.5-1.0mg IV as temporary mearues.
– Adrenaline (but may aggravate cardiac irritability).
– Transcutaneous Pacing (rarely effective).

11. • Tachyarrhythmias:
– Digibind is the definitive treatment.
– Mgso4 as an adjunctive measure.
– Lignocaine (unproven).
– Often refractory to cardioversion.
• Hyperkalemia:
– Insulin and glucose, bicarbonate (salbutamol may aggravate
automaticity).
– Calcium is traditionally contra-indicated due to the risk of
precipitating a ‘stone heart’.

12.  Supportive care and monitoring
• Cardiac monitoring must continue until reversal of toxicity.
 Decontamination
• Activated charcoal if presents <1h post-ingestion(unlikely to
prevent severe toxicity in large ingestions).
• Gastric lavage is not recommended.
 Antidote
• Digibind is the definitive treatment.

13. DIGOXIN-SPECIFIC ANTIBODY FRAGMENTS
(DIGOXIN-FAB)
• Digoxin-Fabs are derived from ovine
antibodies to digoxin. Following IV infusion,
the antibody fragments bind digoxin in the
plasma and distribute widely throughout the
body, removing digoxin from tissues.

14. Based on suspected amount ingested •Digoxin body load (mg) = 0.8 × suspected
ingested amount (mg)
•Digoxin body load (mg) = serum digoxin
concentration (ng/mL) × 5.6 L/kg × weight
(kg)/1000
•One vial (about 40 mg)digoxin-Fab
neutralizes 0.5 milligram Adigoxin
ingested
Based on total serum digoxin
concentration
Number of vials = serum concentration
(ng/mL) × patient weight (kg)/100
Calculation of Digoxin-Specific Antibody Fragment (Fab) Full Neutralizing Dose

15. • In an acute poisoning, each vial of digoxin-Fab reverses approximately 0.5
milligram of ingested digoxin.
• In hemodynamically stable patients, half the calculated total neutralizing
dose is infused initially, and the other half is given if an adequate clinical
response is not seen in 1 to 2 hours.
• Observational studies report that a total of 200 to 480mg of digoxin-Fab (5
to 12 vials) were required to effectively treat severely digoxin-toxic
patients.
• When the ingested dose is unknown and serum level is unavailable, 10
vials are recommended as initial treatment in life-threatening situations.
• Digoxin-Fab is administered IV over 30 minutes, except in cardiac arrest,
when the dose is given as an IV bolus.

16. • In chronic toxicity, an acceptable approach in the hemodynamically stable
patient without clear lifethreatening arrhythmias : administer half of the
dose calculated by level.
• If instability develops, the remaining of the full calculated dose can be
administered.
• One to three vials (40 to 120 milligrams) of digoxinFab are often adequate
in reversing chronic toxicity.

17. DISPOSITION:
• Falling serial serum digoxin levels.
• Normal serum K.
• No GI symptoms.
• No evidence of cardiotoxicity.
Or if digoxin-specific fab given:
• Patients normal serum K.
• No significant cardiac arrhythmia.
• Remains clinically well over the next 6h.
Psychiatry assessment.