What is the initial assessment and management of a patient with suspected diltiazem overdose?

Diltiazem Overdose: Initial Assessment and Management

Immediate Stabilization and Supportive Care

The cornerstone of diltiazem overdose management is aggressive supportive care focused on maintaining hemodynamic stability, with standard resuscitative measures taking priority over specific antidotes. 1

Primary Clinical Manifestations to Assess

The classic triad of diltiazem toxicity includes:

• Bradycardia (often junctional rhythm or high-degree AV block) 1, 2
• Hypotension (due to peripheral vasodilation and negative inotropy) 1, 3
• Cardiac conduction abnormalities (ranging from first-degree AV block to complete heart block and asystole) 1, 4

Additional critical findings may include cardiac failure, altered mental status, and multiorgan dysfunction in severe cases. 1, 4

Initial Resuscitation Algorithm

Step 1: Airway, Breathing, Circulation

• Ensure patent airway and adequate ventilation; intubate if mental status is compromised or respiratory failure develops 4
• Establish large-bore IV access and initiate aggressive fluid resuscitation with normal saline 2, 3
• Continuous cardiac monitoring and frequent blood pressure measurements are mandatory 5

Step 2: Gastrointestinal Decontamination (if presenting within 1-2 hours)

• Administer activated charcoal (1 g/kg) if airway is protected and no contraindications exist 1, 2
• Consider gastric lavage only if presentation is within 1 hour of massive ingestion 1, 2
• Multiple-dose activated charcoal is NOT beneficial for diltiazem elimination 3

Pharmacological Management

For Bradycardia and Conduction Blocks

First-line: Atropine

• Administer 0.6 to 1.0 mg IV atropine for symptomatic bradycardia 1
• Bradycardia frequently responds favorably to atropine 1, 2
• Repeat dosing may be necessary 1

Second-line: Calcium Salts

• Administer 1 g calcium chloride OR 3 g calcium gluconate IV over 5 minutes 1
• Repeat every 10-20 minutes as necessary 1
• For refractory cases, consider continuous infusion at 2 g/hour for up to 24 hours or more 1
• Important caveat: Calcium effectiveness is inconsistent—some patients respond well, others show minimal benefit 1, 3
• Monitor for signs of hypercalcemia during prolonged infusions 1

Third-line: Cardiac Pacing

• Fixed high-degree AV block or asystole refractory to atropine requires temporary transvenous pacing 1, 6
• Pacing was frequently utilized in reported overdose cases 1, 4

For Hypotension and Cardiac Failure

First-line: Vasopressors

• Dopamine or norepinephrine for hypotension 1, 2
• Titrate to maintain adequate perfusion pressure 1

Second-line: Inotropic Support

• Isoproterenol, dopamine, or dobutamine for cardiac failure 1
• Administer cautiously with isoproterenol if no response to vagal blockade 1

Third-line: Glucagon

• Consider glucagon infusion for refractory hypotension 2, 7
• Mechanism: bypasses calcium channels to increase cardiac contractility 2

Fourth-line: High-Dose Insulin Euglycemia (HIE) Therapy

• For refractory hypotension despite standard measures, administer 1 unit/kg IV bolus of regular insulin followed by continuous infusion at 0.5-1 unit/kg/hour 7
• Simultaneously administer dextrose infusion to maintain euglycemia (target glucose 100-200 mg/dL) 7
• Monitor glucose every 15-30 minutes initially, then hourly 7
• This represents rescue therapy with emerging evidence of efficacy in calcium channel blocker overdose 7

For Refractory Cardiac Arrest

Extracorporeal Membrane Oxygenation (ECMO)

• Consider ECMO for profound cardiovascular collapse refractory to all pharmacological interventions 4
• Case reports demonstrate successful outcomes even after multiple asystolic arrests with 48-hour ECMO support 4
• This is a bridge therapy allowing time for drug elimination 4

Critical Pitfalls to Avoid

• Do NOT rely on diltiazem blood levels for clinical decision-making—levels vary over tenfold due to extensive metabolism and do not correlate reliably with toxicity 1
• Hemodialysis and peritoneal dialysis are ineffective for diltiazem removal 1
• Charcoal hemoperfusion and plasmapheresis have limited and inconsistent efficacy 1, 3, 4
• Multiple-dose activated charcoal does NOT enhance elimination 3
• Calcium administration may initially appear ineffective but can become more effective after repeated dosing 1

Monitoring and Disposition

• Continuous cardiac monitoring for at least 24-48 hours is essential, as diltiazem half-life can be prolonged to 28-48 hours in overdose 4
• Monitor for multiorgan dysfunction (renal, hepatic, neurologic) in massive ingestions 4
• Most patients who survive the initial 48 hours make full recovery 1, 2, 4
• ICU admission is mandatory for all symptomatic patients 4, 7