Digoxin toxicity: Difference between revisions
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* Hemodialysis does not work | * Hemodialysis does not work | ||
== Risk Factors == | |||
== | |||
*Hypokalemia | *Hypokalemia | ||
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== Treatment == | == Treatment == | ||
*Fab fragment | *Fab fragment therapy | ||
** | **Indications | ||
***Severe rhythm disturbances refractory to conventional therapy | |||
***End-organ dysfunction | |||
***Hyperkalemia >5 after acute overdose | |||
***Pacemaker (may mask cardiac dysrhythmia) | |||
***Consider for: | |||
**** Dig level > 10 in acute ingestion | |||
**** Dig level > 4 in chronic ingestion | |||
**** If adult acutely ingests > 10mg | |||
**** If child acutely ingests > 4mg | |||
'''**Neither amount ingested nor digoxin level are known:''' | |||
*** 1 vial binds 0.5mg of digoxin | *** 1 vial binds 0.5mg of digoxin | ||
*** Adult dose | *** Adult dose | ||
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***Peds dose | ***Peds dose | ||
**** 5 vials | **** 5 vials | ||
**Peak effect occurs after 90min, initial response after 20min | |||
***Repeat dose if clinical response is inadequate | |||
'''Amount ingested is known but digoxin level is unknown''' | |||
* Step 1: Calculate total body load (TBL) | |||
** TBL = dose (in mg) ingested | |||
* Step 2: Calculate number of vials needed | |||
** Number of vials = TBL X 2 (round up to nearest whole number) | |||
'''Steady state digoxin level is known''' | |||
* Number of vials = (dig level(in ng/mL) X pt wt) / 100 | |||
'''Chronic toxicity without severe signs''' | |||
* Give half the recommended dose | |||
** Otherwise may unmask the condition for which the pt is taking digoxin | |||
*Fab side-effects | |||
** Allergic reaction | |||
** Withdrawal of dig effect: | |||
*** CHF | |||
** Hypokalemia | |||
*Activated charcoal 1g/kg (max 50g) | *Activated charcoal 1g/kg (max 50g) | ||
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*Hypomagnesemia | *Hypomagnesemia | ||
** Treat | ** Treat | ||
*Bradycardia | *Bradycardia | ||
** Atropine 0.5mg IV | ** Atropine 0.5mg IV | ||
** Pacing | |||
*Hypotension | *Hypotension | ||
*Fluid | *Fluid | ||
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-frequent/complex ventricular ectopy | -frequent/complex ventricular ectopy | ||
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-Cardioversion | -Cardioversion | ||
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Revision as of 07:06, 18 March 2011
Background
- Positive inotropic effect
- Inhibits Na-K pump -> increased intracellular Na -> increased intracellular Ca
- Increases vagal tone
- Decreases refractory time; increases automaticity
- Increases risk of dysrhythmias
- Renally cleared
- Hemodialysis does not work
Risk Factors
- Hypokalemia
- Hypovolemia
- Hypoxia
- cardiac ischemia
- renal insufficiency
- Meds
- CCBs, amiodarone
Work-Up
- Dig level
- Normal = 0.8-2 ng/mL
- May have toxicity even with "therapeutic" levels
- Measure serum level at least 6 hours after acute ingestion, immediately for chronic ingestion
- If measure before this may be falsely elevated due to incomplete drug distribution
- Normal = 0.8-2 ng/mL
- Chemistry
- Hyperkalemia level correlates with degree of toxicity
- Hyperkalemia does not cause death; lowering K+ does not reduce mortality
- Hypokalemia increases susceptibility in chronic toxicity
- Hypomagnesemia is common
- Hyperkalemia level correlates with degree of toxicity
- Cr/BUN
- Urine output
- ECG (serial)
Clinical Manifestations
Cardiac
- Any type of dysrhythmia is possible except for rapidly conducted atrial arrhythmias
- Most common:
- PVCs
- Bradycardia
- Digitalis Effect
- T wave changes
- QT interval shortening
- Scooped ST segments with depression in lateral leads
GI
- Nausea/vomiting
- Abdominal pain
Neuro
- Confusion
- Weakness
- Visual disturbances
- yellow halos
- Scotomas
- Delirium
Treatment
- Fab fragment therapy
- Indications
- Severe rhythm disturbances refractory to conventional therapy
- End-organ dysfunction
- Hyperkalemia >5 after acute overdose
- Pacemaker (may mask cardiac dysrhythmia)
- Consider for:
- Dig level > 10 in acute ingestion
- Dig level > 4 in chronic ingestion
- If adult acutely ingests > 10mg
- If child acutely ingests > 4mg
- Indications
**Neither amount ingested nor digoxin level are known:
- 1 vial binds 0.5mg of digoxin
- Adult dose
- 10 vials over 30 minutes through 0.22 micron filter
- Peds dose
- 5 vials
- Peak effect occurs after 90min, initial response after 20min
- Repeat dose if clinical response is inadequate
Amount ingested is known but digoxin level is unknown
- Step 1: Calculate total body load (TBL)
- TBL = dose (in mg) ingested
- Step 2: Calculate number of vials needed
- Number of vials = TBL X 2 (round up to nearest whole number)
Steady state digoxin level is known
- Number of vials = (dig level(in ng/mL) X pt wt) / 100
Chronic toxicity without severe signs
- Give half the recommended dose
- Otherwise may unmask the condition for which the pt is taking digoxin
- Fab side-effects
- Allergic reaction
- Withdrawal of dig effect:
- CHF
- Hypokalemia
- Activated charcoal 1g/kg (max 50g)
- Only an adjunctive tx; NOT an alternative to fab fragment therapy
- Consider only if present within 2 hr of ingestion
- Hyperkalemia
- Do not treat! Do not give calcium!
- Once fab is given hyperkalemia will rapidly correct
- Aggressive tx with potassium-lowering agents could cause sig hypokalemia following therapy
- Once fab is given hyperkalemia will rapidly correct
- Do not treat! Do not give calcium!
- Hypokalemia
- Treat!
- Hypomagnesemia
- Treat
- Bradycardia
- Atropine 0.5mg IV
- Pacing
- Hypotension
- Fluid
Indications for Rx of rhythm disturbances
-hemodynamic compromise caused by bradycardia or tachycardia
-frequent/complex ventricular ectopy
Tachyarrhythmias, increased automaticity
-K
-Mag
-Lidocaine
-Phenytoin
-Cardioversion
-co-ingestion of cardiotoxic drugs: CCBs, beta-blockers, or TCAs
Empiric Dosages
-Chronic toxicity and unkown level: 4-6 vials (1/2 vial in child)
-Cariac arrest = 20 vials undiluted by IV bolus
Source
Rosen's, UpToDate