Calcium Channel Blocker Overdose Management (309)

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A guideline is intended to assist healthcare professionals in the choice of disease-specific treatments.

Clinical judgement should be exercised on the applicability of any guideline, influenced by individual patient characteristics. Clinicians should be mindful of the potential for harmful polypharmacy and increased susceptibility to adverse drug reactions in patients with multiple morbidities or frailty.

If, after discussion with the patient or carer, there are good reasons for not following a guideline, it is good practice to record these and communicate them to others involved in the care of the patient.

Background

Calcium channel blockers (CCB) are used to in the treatment of angina, hypertension, and the rate control of tachyarrhythmias. The most commonly prescribed agents are verapamil, diltiazem, amlodipine, and nifedipine; with immediate and modified release preparations available.

Common complications associated with overdose of these agents includes hypotension and bradycardia whilst hyperglycaemia, hyperkalaemia, acidosis, ischaemic bowel and seizures may be encountered.

Death secondary to refractory hypotension, and cardiac suppression may develop up to 12 hours in immediate release preparations, and within 24 hours for modified release agents.

 

Management

Please refer to TOXBASE for definitive recommendations, however as a quick reference:

1. Gastric decontamination

a. For patients presenting within 1 hour, particularly for modified release preparations, gastric lavage (in those with skills to do so), and/or activated charcoal.

b. Multi-dose activated charcoal for late presentations of modified release agents.

c. Consider whole-bowel irrigation with modified release agents.

2. Bradycardia

a. Treat with IV atropine (titrate to response)

b. Consider IV dobutamine, isoprenaline

c. Temporary pacing.

3. Hypotension

a. IV fluid bolus of 0.9% NaCl 20 mls/kg

b. IV calcium chloride or IV calcium gluconate as a slow bolus

c. IV Insulin & dextrose therapy as second-line agent.

d. For treatment resistant cases, Intralipid may prove of benefit if the above measures fail e. Consider IV inotropes, and/or mechanical means of blood pressure support.

4. Cardiac Arrest

a. For in-hospital, or witnessed cardiac arrest with immediate CPR, resuscitation should be continued for at least 1 hour.

NOTES

IV calcium therapy is used to temporarily restore blood pressure Repeat doses (maximum 4), or an infusion may be required.

IV insulin & dextrose therapy (High Dose Insulin Euglycaemic Therapy, HIET) has been used successfully to restore cardiac function, and reverse hypotension in beta-blocker and CCB overdose, and is considered superior to inotropes for treatment resistant cases. HIET may be administered peripherally, reducing the time necessary to initiate treatment, but it may be up to 15 minutes for clinical effect to become apparent.

 

Drug Doses

DRUG DOSES

Please check with TOXBASE for up-to-date drug doses. Below is a guide to the relevant therapeutic interventions:

10% CALCIUM GLUCONATE

  • 0.6 ml/kg up to 30 ml over 5 minutes repeated every 10-20 minutes; MAX 4 DOSES
  • Monitor calcium levels if repeated doses are required

INSULIN & DEXTROSE PROTOCOL

  • Check plasma glucose and potassium
  • If plasma glucose < 10 mmol/L, give 50 mL of 50% dextrose
  • If plasma potassium <2.5 mmol/L, give 20mmol potassium IV over 30 mins with cardiac monitoring*
  • Once hypokalaemia corrected:
  • ACTRAPID 1 unit/kg as a bolus followed by
  • ACTRAPID infusion 0.5-2.0 units/kg/hr titrated to clinical response
  • Increase rate by 2 units/kg/hr every 10 minutes (max 10 units/kg/hr) o 10% dextrose infusion run 100 ml/hr concurrently.
  • Check BM every 10 mins after dose change, then hourly when stable dose o Check potassium hourly (on venous gas?)
  • Target systolic BP >100 mmHg and heart rate > 50/min

This is faster than GG&C currently recommend for routine treatment of hypokalaemia.

If hypoglycaemia develops during treatment, increase of rate of infusion of 10% dextrose or to minimise fluid overload using higher concentrations of dextrose (20% peripherally, 50% via central/long peripheral line access), titrated to effect may be required.

INTRALIPID

1.5 ml/kg of 20% Intralipid as an IV bolus followed by:

  • 0.25-0.5 ml/kg/min for 30-60 mins to a max dose of 500ml (titrate to response) o Repeated bolus 1-2 times for cardiovascular collapse or asystole

 

Last reviewed: 24 February 2021

Next review: 01 December 2022

Author(s): Richard Stevenson

Version: 3

Author Email(s): [email protected]

Approved By: North Emergency Department Clinical Governance Group

Document Id: 309