Calcium Channel Blocker Overdose

Overview

A relatively common and potentially lethal ingestion...and often in a slow release form (eg Diltiazem CR).

Morbidity and mortality is generally due to cardiovascular collapse resulting from a combination of

  • extreme peripheral vasodilatation
  • myocardial depression
  • impaired myocardial conduction.

Extra-cardiac toxicity such as

  • Hyperglycaemia
  • Lactic acidosis
  • Seizures
  • Non-cardiogenic pulmonary oedema

are less common but imply a poorer prognosis.

 

INVESTIGATIONS

Close cardiac monitoring is paramount.

ECG FINDINGS

  • Bradycardia
  • First degree heart block
  • Progressive complete heart block
  • Sinus arrest with node escape
  • Asystole

 

 

MANAGEMENT

Resuscitation

  • A: Intubate if agitated or obtunded (EARLY IS BETTER)
  • B: Supportive
  • C: IV fluid, Calcium, High Dose Insulin, Inotropes, Invasive Monitoring

SPECIFIC TREATMENTS (GRADUATED APPROACH)

  1. Fluid resuscitation, crystalloid
  2. Calcium: 60ml (0.6-1.0 ml/kg in children) bolus of 10% Calcium Gluconate over 5-10 min. May need to be repeated every 20 mins (Up to 3 doses). Then commence an infusion of Calcium Chloride (1g/hour), suggested optimal serum ionised Calcium 2mmol/L (VBG/ABG monitoring)
  3. High - Dose Insulin Therapy
  • 50ml of 50% Glucose (25g) bolus THEN 1 IU/kg Actrapid (short acting Insulin) bolus
  • Continue Glucose 25g/hr IV infusion & Short Acting Insulin 0.5 IU/kg/hr IV infusion
  • Glucose infusion titrated to maintain euglycaemia
  • Insulin infusion may need to be increased to 1 IU/kg/hr
  • Infusions need to continue until CV instability has resolved

     5. Inotropes: Noradrenaline &/or Adrenaline titration

     6. Na Bicarbonate (50-100 mmol/L (0.5-1.0 mmol/L in children) for metabolic acidosis

     7. Cardiac pacing: Often Difficult Transcutaneously, Transvenously next step

If cardiovascular collapse despite above, consider

  • early invasive intervention and consideration of ECMO / Cardiopulmonary Bypass / Balloon Pump
  • Methylene Blue (controversial and lacking good data but several case studies have shown benefit) 1.5mg/kg loading dose then 1.5mg/kg/hr infusion
  • Lipid emulsion (Intralipid)

Decontamination

  • Consider activated charcoal if presents early
  • Whole bowel irrigation if slow release form ingested
  • Consider charcoal haemoperfusion for verapamil

 

References

Calcium Channel Blocker Toxicity

Is methylene blue beneficial in treating calcium-channel-blocker overdose?

Methylene Blue in the Treatment of Refractory Shock From an Amlodipine Overdose.