Digoxin toxicity: Difference between revisions
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***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
***Can lead to bradyarrhythmias (esp in young)
***Can lead to [[Bradyarrhythmias]] (esp in young)
**Increases automaticity
**Increases automaticity
***Can lead to tachyarrhythmias (esp in elderly)
***Can lead to [[Tachyarrhythmias]] (esp in elderly)
*Renally cleared
*Renally cleared
*Hemodialysis does not work
*Hemodialysis does not work


== Risk Factors ==
=== Risk Factors ===
#Electrolyte Imbalance
#Electrolyte Imbalance
##[[Hypokalemia]], [[Hypomagnesemia]], [[Hypercalcemia]]
##[[Hypokalemia]], [[Hypomagnesemia]], [[Hypercalcemia]]
#Hypovolemia
#Hypovolemia
#Renal insufficiency
#Renal insufficiency
#Cardiac ischemia
#[[Cardiac Ischemia]]
#[[Hypothyroidism]]
#[[Hypothyroidism]]
#Meds
#Meds
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== Clinical Manifestations ==
== Clinical Manifestations ==
===Cardiac===
===Cardiac===
#Syncope
#[[Syncope]]
#Dysrhythmias
#Dysrhythmias
##PVCs
##PVCs
##Bradycardia
##[[Bradycardia]]
##SVT w/ AV block
##SVT w/ AV block
##Junctional escape
##Junctional escape
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#Digitalis Effect (seen with therapeutic levels; not indicative of toxicity)
#Digitalis Effect (seen with therapeutic levels; not indicative of toxicity)
##T wave changes (flattening or inversion)
##T wave changes (flattening or inversion)
##QT interval shortening
##[[QT Interval Shortening]]
##Scooped ST segments with depression in lateral leads
##Scooped ST segments with depression in lateral leads
##Increased U-wave amplitude
##Increased U-wave amplitude
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===GI===
===GI===
#Often the earliest manifestation of toxicity
#Often the earliest manifestation of toxicity
##Nausea/vomiting
##[[Nausea/vomiting]]
##Abdominal pain
##[[Abdominal Pain]]


===Neuro===
===Neuro===
#Confusion
#[[Confusion]]
#Weakness
#[[Weakness]]
#Visual disturbances
#Visual disturbances
##Yellow halos
##Yellow halos
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###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
#Potassium level
#Potassium level
##Acute toxicity: Degree of hyperkalemia correlates w/ degree of toxicity
##Acute toxicity: Degree of [[Hyperkalemia]] correlates w/ degree of toxicity
##Chronic toxicity: K+ may be normal/low (concomitant diuretic use) or high (renal failure)
##Chronic toxicity: K+ may be normal/low (concomitant diuretic use) or high (renal failure)


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#CCB/BB toxicity
#CCB/BB toxicity
#Clonidine toxicity
#Clonidine toxicity
#Organophosphate poisoning
#[[Organophosphate pPisoning]]
#Sick sinus syndrome
#Sick sinus syndrome


==Work-Up==
==Work-Up==
#Dig level
#Dig level
##Only useful prior to administration of Fab (otherwise becomes falsely elevated)
##Only useful prior to administration of [[Fab]] (otherwise becomes falsely elevated)
#Chemistry
#Chemistry
#Urine output
#Urine output
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##Consider lower energy settings (25-50J)  
##Consider lower energy settings (25-50J)  
#Bradyarrhythmias (symptomatic)
#Bradyarrhythmias (symptomatic)
##Atropine 0.5mg IV
##[[Atropine]] 0.5mg IV
##Pacing
##[[Pacing]]
#Ventricular dysrhythmias
#Ventricular dysrhythmias
##[[Dilantin Load|Phenytoin]]
##[[Dilantin Load|Phenytoin]]
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===[[Hyperkalemia]]===
===[[Hyperkalemia]]===
#Treat with Fab, not with usual meds
#Treat with [[Fab]], not with usual meds
##Once Fab is given hyperkalemia will rapidly correct
##Once Fab is given hyperkalemia will rapidly correct
#If Fab unavailable and hyperkalemia is life-threatening then treat with:
#If [[Fab]] unavailable and hyperkalemia is life-threatening then treat with:
##Glucose-insulin
##Glucose-insulin
##Sodium bicarb
##Sodium bicarb
##Kayexelate
##Kayexelate
##Dialsysis
##Dialysis
##Calcium (controversial: some say dangerous, others say not)
##Calcium (controversial: some say dangerous, others say not)


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==Disposition==
==Disposition==
*Admit for signs of toxicity or history of large ingested dose; admit to ICU if Fab given
*Admit for signs of toxicity or history of large ingested dose; admit to ICU if [[Fab]] given
*Discharge after 12hr observation if asymptomatic after accidental overdose
*Discharge after 12hr observation if asymptomatic after accidental overdose


Revision as of 21:42, 31 March 2012

Background

  • Mechanism of action
    • Positive inotropic effect
      • Inhibits Na-K pump -> incr extracelluar K, incr intracellular Na -> incr intracellular Ca
    • Increases vagal tone
    • Increases automaticity
  • Renally cleared
  • Hemodialysis does not work

Risk Factors

  1. Electrolyte Imbalance
    1. Hypokalemia, Hypomagnesemia, Hypercalcemia
  2. Hypovolemia
  3. Renal insufficiency
  4. Cardiac Ischemia
  5. Hypothyroidism
  6. Meds
    1. CCBs, amiodarone

Clinical Manifestations

Cardiac

  1. Syncope
  2. Dysrhythmias
    1. PVCs
    2. Bradycardia
    3. SVT w/ AV block
    4. Junctional escape
    5. Ventricular dysrhythmia, including bidirectional V-tach (esp in chronic toxicity)
  3. Digitalis Effect (seen with therapeutic levels; not indicative of toxicity)
    1. T wave changes (flattening or inversion)
    2. QT Interval Shortening
    3. Scooped ST segments with depression in lateral leads
    4. Increased U-wave amplitude

GI

  1. Often the earliest manifestation of toxicity
    1. Nausea/vomiting
    2. Abdominal Pain

Neuro

  1. Confusion
  2. Weakness
  3. Visual disturbances
    1. Yellow halos
    2. Scotomas
  4. Delirium

Diagnosis

  1. Must use H&P and labs in combination; no single element excludes or confirms the dx
  2. Digoxin level
    1. Normal = 0.5-2 ng/mL (ideal = 0.7-1.1)
      1. May have toxicity even with "therapeutic" levels (esp w/ chronic toxicity)
    2. Measure at least 6hr after acute ingestion (if stable); immediately for chronic ingestion
      1. If measure before this may be falsely elevated due to incomplete drug distribution
  3. Potassium level
    1. Acute toxicity: Degree of Hyperkalemia correlates w/ degree of toxicity
    2. Chronic toxicity: K+ may be normal/low (concomitant diuretic use) or high (renal failure)

DDX

  1. CCB/BB toxicity
  2. Clonidine toxicity
  3. Organophosphate pPisoning
  4. Sick sinus syndrome

Work-Up

  1. Dig level
    1. Only useful prior to administration of Fab (otherwise becomes falsely elevated)
  2. Chemistry
  3. Urine output
  4. ECG (serial)

Treatment

  1. Digoxin Immune Fab
  2. Activated Charcoal
    1. Questionable efficacy
    2. Only an adjunctive tx; NOT an alternative to fab fragment therapy
    3. Consider only if present within 1 hr of ingestion
    4. 1g/kg (max 50g)

Dysrhythmias

  1. Digoxin Immune Fab is the agent of choice for all dysrhythmias!
  2. Cardioversion should only be used as a last resort (may precipitate V-Fib)
    1. Consider lower energy settings (25-50J)
  3. Bradyarrhythmias (symptomatic)
    1. Atropine 0.5mg IV
    2. Pacing
  4. Ventricular dysrhythmias
    1. Phenytoin
      1. Enhances AV conduction
      2. Phenytoin: 15-20mg/kg at 50mg/min
      3. Fosphenytoin: 15-20mg PE/kg at 100-150mg/min
    2. Lidocaine
      1. Decreases ventricular automaticity
      2. 1-3mg/kg over several minutes; follow by 1-4mg/min

Hyperkalemia

  1. Treat with Fab, not with usual meds
    1. Once Fab is given hyperkalemia will rapidly correct
  2. If Fab unavailable and hyperkalemia is life-threatening then treat with:
    1. Glucose-insulin
    2. Sodium bicarb
    3. Kayexelate
    4. Dialysis
    5. Calcium (controversial: some say dangerous, others say not)

Hypokalemia

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

Hypomagnesemia

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

Disposition

  • Admit for signs of toxicity or history of large ingested dose; admit to ICU if Fab given
  • Discharge after 12hr observation if asymptomatic after accidental overdose

See Also

Source

  • Rosen's
  • Tintinalli
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