Calcium channel blocker toxicity

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Background

  • Hemodialysis is ineffective
  • Precipitous deterioration is common (esp with verapamil)
  • Nifedipine can kill a child with a single pill

2 Classes

Dihydropyridines

  • Nifedipine, Amlodipine, Nicardipine
    • Systemic vasodilation, mild effect on heart
  • Toxicity = Hypotension, reflex tachycardia
  • With higher doses of toxicity peripheral selectivity is lost
    • I.e. may see decreased inotrophy, bradycardia

Non-dihydropyridines (verapamil, diltiazem)

  • Stronger effect on heart, weak vasodilators
  • Toxicity = Bradycardia, decreased inotropy

Clinical Features

Differential Diagnosis

Symptomatic bradycardia

Evaluation

  • ECG
    • PR prolongation (varying degrees of AV block)
      • AV block occurs more commonly with verapamil
    • Bradydysrhythmia
  • Glucose
    • hyperglycemia, may help distinguish beta blocker toxicity
  • Chemistry
    • Serum calcium is often normal

Management

The majority of literature on calcium channel blocker overdose management is low-quality evidence and high-dose insulin and extracorporeal life support have the best evidence; other therapies such as include calcium, dopamine, norepinephrine, and lipid emulsion therapy may be beneficial but are poorly studied[1]

  • Monotherapy only successful for trivial overdoses

GI decontamination

  • Charcoal
    • 1g/kg (max 50g) x1
    • Consider if present within 1-2hr with delayed-release preparation
  • Consider whole bowel irrigation if sustained or extended-release, esp if the drug is verapamil or diltiazem

Fluids

  • Initial 20cc/kg bolus especially if source of hypotension is undifferentiated and also possibly hypovolemic or due to Sepsis

Atropine

  • Adult: 0.5-1mg IV q2-3min to max of 3g
  • Ped: 0.02mg/kg (minimum is 0.1mg)
  • Administer to anyone with symptomatic bradycardia

Calcium

Avoid if digoxin toxicity is possible

  • Calcium gluconate 3g (30-60mL of 10% soln)
  • Calcium chloride 1-3g IV bolus (10-20mL of 10% soln (requires large IV/central line)
    • Preferred over calcium gluconate because it provides triple the amount of calcium on a weight-to-weight basis [2]
    • Give Calcium 1g Q5min to titrate to BP effect
    • If effect in BP is seen can give as a drip at 10-50mg/kg/hr
    • can safely push serum Calcium levels to 15-18 or even low 20s if patient tolerates (double normal)

Glucagon

  • 5mg IV bolus q10min x 2
  • will often cause severe nausea/vomiting, give Zofran prior

Vasopressors

  • Norepinephrine is agent of choice
    • Start at 2mcg/min, uptitrate rapidly, goal MAP 65mmHg

High-dose insulin and glucose

  • Takes 30-60min for effect
  • Glucose:
    • Adult: 50mL of D50W
    • Ped: 2.5mL/kg of D10
  • Insulin bolus 1 unit/kg given with 1amp of D50
    • Titrate infusion until hypotension is corrected or max 2u/kg/hr
    • Titrate dextrose drip to avoid hypoglycemia
    • initial glucose checks q15 minutes until blood sugar stability established
  • Potassium
    • If <3 administer 20mEq IV

Intravenous lipid emulsion

  • 1.5mL/kg bolus of 20% lipid followed by 0.25mL/kg/minute

Disposition

  • Admit all symptomatic patients
  • Admit all sustained-release ingestions
  • Discharge if asymptomatic x 6-8hrs

See Also

Video

References

  1. ↑ St-Onge M, et al. Treatment for calcium channel blocker poisoning: a systematic review. Clin Toxicol 2014 PDF
  2. ↑ Tintinalli's 7th Ed.
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