Digoxin toxicity: Difference between revisions
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*Positive inotropic effect
*Positive inotropic effect
** Inhibits Na-K pump -> incr extracelluar K, incr intracellular Na -> incr intracellular Ca
**Inhibits Na-K pump -> incr extracelluar K, incr intracellular Na -> incr intracellular Ca
*Increases vagal tone
*Increases vagal tone
**Bradyarrhythmias (esp in young)
**Can lead to bradyarrhythmias (esp in young)
*Increases automaticity
*Increases automaticity
**Tachyarrhythmias (esp in elderly)
**Can lead to tachyarrhythmias (esp in elderly)
*Renally cleared
*Renally cleared
*Hemodialysis does not work
*Hemodialysis does not work
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== Risk Factors ==
== Risk Factors ==


*Electrolyte
*Electrolyte Imbalance
**Hypokalemia, hypomagnesemia, Hypercalcemia
**Hypokalemia, hypomagnesemia, Hypercalcemia
*Hypovolemia
*Hypovolemia
*Renal insufficiency
*Cardiac ischemia
*Cardiac ischemia
*Renal insufficiency
*Hypothyroidism
*Hypothyroidism
*Meds
*Meds
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Cardiac
Cardiac
*Any type of dysrhythmia is possible except for rapidly conducted atrial arrhythmias
*Any type of dysrhythmia is possible except for rapidly conducted atrial arrhythmias
*Most common:
*Most common:
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**Bradycardia
**Bradycardia
*Digitalis Effect
*Digitalis Effect
** T wave changes
**T wave changes
** QT interval shortening
**QT interval shortening
** Scooped ST segments with depression in lateral leads
**Scooped ST segments with depression in lateral leads


GI
GI
*Nausea/vomiting
*Nausea/vomiting
*Abdominal pain
*Abdominal pain


Neuro
Neuro
*Confusion
*Confusion
*Weakness
*Weakness
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**Scotomas
**Scotomas
*Delirium
*Delirium




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*Dig level
*Dig level
**Normal = 0.8-2 ng/mL
**Normal = 0.8-2 ng/mL (ideal = 0.7-1.1)
***May have toxicity even with "therapeutic" levels
***May have toxicity even with "therapeutic" levels
**Measure serum level at least 6 hours after acute ingestion, immediately for chronic ingestion
**Measure serum level at least 6 hours after acute ingestion (if stable), immediately for chronic ingestion
***If measure before this may be falsely elevated due to incomplete drug distribution
***If measure before this may be falsely elevated due to incomplete drug distribution
*Chemistry
*Chemistry
**Hyperkalemia level correlates with degree of toxicity
**Hyperkalemia level correlates with degree of toxicity
*** Hyperkalemia does not cause death; lowering K+ does not reduce mortality
***Hyperkalemia does not cause death; lowering K+ does not reduce mortality
**Hypokalemia increases susceptibility in chronic toxicity
**Hypokalemia increases susceptibility in chronic toxicity
**Hypomagnesemia is common
**Hypomagnesemia is common
*Cr/BUN
*Cr/BUN
*Urine output
*Urine output
* ECG (serial)
*ECG (serial)
 




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***CHF, a fib w/ RVR
***CHF, a fib w/ RVR
**Hypokalemia
**Hypokalemia
*Initial response time ~ 20min, peak effect ~ 90min


*How To Use
*How To Use
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***Peds dose
***Peds dose
****5 vials over 30 min
****5 vials over 30 min
***Peak effect occurs after 90min, initial response after 20min
****Repeat dose if clinical response is inadequate
****Repeat dose if clinical response is inadequate
**'''2. Amount ingested is known but digoxin level is unknown'''
**'''2. Amount ingested is known but digoxin level is unknown'''
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**Give half the recommended dose
**Give half the recommended dose
***Otherwise may unmask the condition for which the pt is taking digoxin
***Otherwise may unmask the condition for which the pt is taking digoxin
**'''5. Cardiac Arrest'''
***20 vials administered undiluted by IV bolus


'''Activated charcoal'''
'''Activated charcoal'''
*Questionable efficacy
*Only an adjunctive tx; NOT an alternative to fab fragment therapy
*Only an adjunctive tx; NOT an alternative to fab fragment therapy
*Consider only if present within 2 hr of ingestion
*Consider only if present within 1 hr of ingestion
*1g/kg (max 50g)
*1g/kg (max 50g)


'''Rhythm Disturbances'''
'''Rhythm Disturbances'''
*Bradycardia (symptomatic)
*Fab fragments is the agent of choice for all dysrhythmias!
*Bradyarrhythmias (symptomatic)
**Atropine 0.5mg IV
**Atropine 0.5mg IV
**Pacing
**Pacing
*Tachyarrhythmias
*Tachyarrhythmias
**K
**Mag
**Lidocaine
**Lidocaine
***1-3mg/kg over several minutes, followed by 1-4mg/min
**Phenytoin
**Phenytoin
**Cardioversion  
***May enhance AV conduction
***Infuse at 25-50 mg/min to a loading dose of 10-15mg/kg
*Cardioversion
**Consider lower energy settings (25-50J)


'''Hyperkalemia'''


'''Hyperkalemia'''
*Treat with Fab, not with usual meds
*Treat with Fab, not with usual meds. Do not give calcium!
**Once fab is given hyperkalemia will rapidly correct
**Once fab is given hyperkalemia will rapidly correct
***Aggressive tx with potassium-lowering agents could cause sig hypokalemia following therapy
**Aggressive tx with potassium-lowering agents could cause sig hypokalemia following therapy
*If Fab is not available and hyperkalemia is life-threatening then treat
*Calcium is controversial (some say dangerous, others say not)


'''Hypokalemia'''
'''Hypokalemia'''
*Treat!
 
*Chronic intoxication
**Raise level to 3.5-4
*Acute intoxication
**Do not treat (likely that potassium level is rapidly rising)


'''Hypomagnesemia'''
'''Hypomagnesemia'''
*Treat
*Treat with 1-2g over 10-20 min
**Monitor for resp depresion
**Avoid in pts with:
***Renal failure
***Bradydysrhythmias/conduction blocks


== Source ==
== Source ==


Rosen's, UpToDate
Rosen's


<br/>[[Category:Tox]] <br/><br/>
[[Category:Tox]] <br/>

Revision as of 18:06, 21 March 2011

Background

  • Positive inotropic effect
    • Inhibits Na-K pump -> incr extracelluar K, incr intracellular Na -> incr intracellular Ca
  • Increases vagal tone
    • Can lead to bradyarrhythmias (esp in young)
  • Increases automaticity
    • Can lead to tachyarrhythmias (esp in elderly)
  • Renally cleared
  • Hemodialysis does not work
  • 1 fab vial binds 0.5mg of digoxin

Risk Factors

  • Electrolyte Imbalance
    • Hypokalemia, hypomagnesemia, Hypercalcemia
  • Hypovolemia
  • Renal insufficiency
  • Cardiac ischemia
  • Hypothyroidism
  • Meds
    • CCBs, amiodarone

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


Work-Up

  • Dig level
    • Normal = 0.8-2 ng/mL (ideal = 0.7-1.1)
      • May have toxicity even with "therapeutic" levels
    • Measure serum level at least 6 hours after acute ingestion (if stable), immediately for chronic ingestion
      • If measure before this may be falsely elevated due to incomplete drug distribution
  • 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
  • Cr/BUN
  • Urine output
  • ECG (serial)


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
  • Side effects
    • Allergic reaction
    • Withdrawal of dig effect:
      • CHF, a fib w/ RVR
    • Hypokalemia
  • Initial response time ~ 20min, peak effect ~ 90min
  • How To Use
    • 1. Neither amount ingested nor digoxin level are known:
      • Adult dose
        • 10 vials over 30 min
      • Peds dose
        • 5 vials over 30 min
        • Repeat dose if clinical response is inadequate
    • 2. 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)
    • 3. Steady state digoxin level is known
    • Number of vials = (dig level(in ng/mL) X pt wt) / 100
    • 4. Chronic toxicity without severe signs
    • Give half the recommended dose
      • Otherwise may unmask the condition for which the pt is taking digoxin
    • 5. Cardiac Arrest
      • 20 vials administered undiluted by IV bolus

Activated charcoal

  • Questionable efficacy
  • Only an adjunctive tx; NOT an alternative to fab fragment therapy
  • Consider only if present within 1 hr of ingestion
  • 1g/kg (max 50g)

Rhythm Disturbances

  • Fab fragments is the agent of choice for all dysrhythmias!
  • Bradyarrhythmias (symptomatic)
    • Atropine 0.5mg IV
    • Pacing
  • Tachyarrhythmias
    • Lidocaine
      • 1-3mg/kg over several minutes, followed by 1-4mg/min
    • Phenytoin
      • May enhance AV conduction
      • Infuse at 25-50 mg/min to a loading dose of 10-15mg/kg
  • Cardioversion
    • Consider lower energy settings (25-50J)

Hyperkalemia

  • Treat with Fab, not with usual meds
    • Once fab is given hyperkalemia will rapidly correct
    • Aggressive tx with potassium-lowering agents could cause sig hypokalemia following therapy
  • If Fab is not available and hyperkalemia is life-threatening then treat
  • Calcium is controversial (some say dangerous, others say not)

Hypokalemia

  • Chronic intoxication
    • Raise level to 3.5-4
  • Acute intoxication
    • Do not treat (likely that potassium level is rapidly rising)

Hypomagnesemia

  • Treat with 1-2g over 10-20 min
    • Monitor for resp depresion
    • Avoid in pts with:
      • Renal failure
      • Bradydysrhythmias/conduction blocks

Source

Rosen's

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