Prehospital Academy Lesson 27.4
Toxicology: Cardiac and Other Common Medications
This lesson provides an advanced overview of cardiac medication toxidromes, crucial for EMS providers to understand for the recognition and management of potentially lethal overdoses and adverse reactions.
General Principles of Cardiac Medication Toxicity
Cardiac medications are potent agents designed to alter the heart's function or rhythm. Overdose or adverse reactions can lead to severe, life-threatening complications. Management often requires a rapid, critical assessment and intervention at the advanced life support (ALS) level.
Assessment: Use patient history and medication lists to identify involved substances.
Goal: Minimize negative effects while determining the appropriate antidote or supportive measures.
Poison Control: Contact Poison Control early to aid in identification and management strategies.
ALS Level Care: Cardiac medication toxicities generally require ALS intervention due to their complexity and potential lethality.
Specific Cardiac Medication Toxidromes
Understanding the presentation of different classes of cardiac medications is vital.
1. Sodium Channel Blocker Toxicity (e.g., Procainamide, Flecainide, Quinidine, also Tricyclic Antidepressants in overdose)
ECG Changes: QRS and PR prolongation, QT prolongation.
Hemodynamic Effects: Hypotension secondary to depressed myocardial contractility.
Dysrhythmias: Ventricular dysrhythmias (e.g., wide complex tachycardia).
Management:
Supportive care (ABCs, IV fluids).
Sodium bicarbonate for QRS widening (ALS protocol).
Vasopressors for hypotension.
Antidysrhythmic as appropriate.
2. Beta-Adrenergic Blocker Toxicity (Beta Blockers)
Presentation: Hypotension, bradycardia, lethargy, weakness. Hypoglycemia can also be present, especially in pediatric patients.
Management:
Supportive care (ABCs, IV fluids).
Atropine for symptomatic bradycardia.
Glucagon (ALS protocol) can bypass beta-receptor blockade.
Vasopressors (e.g., norepinephrine, epinephrine) for persistent hypotension.
High-dose insulin euglycemia therapy may be considered for refractory cases (ALS/MD consultation).
3. Potassium Channel Blocker Toxicity (e.g., Amiodarone, Sotalol)
Presentation: Hypotension, bradycardia, ventricular dysrhythmias (e.g., Torsades de Pointes). Prolonged QT interval on ECG.
Management:
Supportive care (ABCs, IV fluids).
IV magnesium sulfate for Torsades de Pointes (ALS protocol).
Overdrive pacing may be necessary for refractory bradycardia (ALS protocol).
Correct electrolyte abnormalities.
4. Calcium Channel Blocker Toxicity (e.g., Diltiazem, Verapamil, Amlodipine)
Presentation: Decreased heart rate (bradycardia), decreased AV nodal conduction (AV blocks), decreased myocardial contractility, hypotension.
Management:
Supportive care (ABCs, IV fluids).
IV calcium (chloride or gluconate, ALS protocol) to counteract calcium channel blockade.
Glucagon (ALS protocol).
Vasopressors for refractory hypotension.
High-dose insulin euglycemia therapy (ALS/MD consultation).
Atropine for symptomatic bradycardia.
5. Digoxin (Cardiac Glycoside) Toxicity
Presentation: Bradycardia, AV blocks, various dysrhythmias (e.g., ventricular bigeminy, junctional tachycardia), nausea, vomiting, visual disturbances (yellow-green halos).
Management:
Supportive care (ABCs).
Activated charcoal if recent ingestion and patient meets criteria (ALS protocol).
Digoxin-specific antibody fragments (DigiFab) is the antidote (ALS/MD consultation).
Correct electrolyte abnormalities (especially hyperkalemia).
Atropine for symptomatic bradycardia.
Critical Thinking Questions
You are treating a patient with a known history of ingesting an unknown quantity of their beta-blocker medication. What are the key signs and symptoms you would anticipate, and what specific antidotal therapies might an ALS provider consider?
A patient presents with a profound bradycardia, first-degree AV block, and hypotension after an intentional overdose of a calcium channel blocker. Outline the immediate prehospital management steps, including specific pharmacological interventions for ALS.
Describe the ECG changes associated with sodium channel blocker toxicity and explain why sodium bicarbonate is a critical treatment.
Why is it crucial to contact Poison Control and engage medical control early in cases of cardiac medication overdose, especially for non-paramedic providers?
In a patient with suspected digoxin toxicity, what are some of the classic non-cardiac signs and symptoms, and how do they aid in diagnosis?