Should diltiazem be administered pre-hospital?

Prehospital Diltiazem Administration

Yes, diltiazem can be safely and effectively administered in the prehospital setting for atrial fibrillation with rapid ventricular response when strict protocols are followed, with clinical improvement rates of 57-74% and low adverse event rates of 3.5-11%. 1, 2, 3

Evidence for Prehospital Use

Efficacy Data

• Clinical improvement occurs in 63-74% of patients when diltiazem is administered prehospitally for atrial fibrillation with rapid ventricular response, defined as heart rate <100 bpm or ≥20% decrease from maximum heart rate 1, 2, 3
• Rate control to <100 bpm is achieved in 27-33% of patients in the prehospital setting 2, 3
• Protocol adherence significantly improves outcomes: patients receiving diltiazem according to protocol showed 63% clinical improvement versus 46% when given outside protocol parameters 1

Safety Profile

• Adverse events occur in only 3.5-11% of prehospital diltiazem administrations, primarily hypotension and bradycardia 1, 2, 3
• The hypotension rate is very low (approximately 2 patients out of 278 in one study became hypotensive, defined as SBP <90 mmHg with ≥10 mmHg drop) 3
• When protocols are violated, adverse event rates nearly double (18% versus 8%) 1

Recommended Protocol Parameters

Patient Selection Criteria

• Stable, symptomatic patients with atrial fibrillation and rapid ventricular response >150 bpm with narrow QRS complex 1
• Systolic blood pressure should be ≥140 mmHg (patients with SBP <140 mmHg have higher adverse event rates) 2
• Heart rate should be ≥120 bpm (lower baseline heart rates increase adverse event risk) 2

Dosing Recommendations

• Standard dose: 0.25 mg/kg IV bolus over 2 minutes (maximum 20 mg) 4, 1
• Lower doses (≤0.2 mg/kg) may be equally effective with reduced hypotension risk (adjusted odds ratio 0.39 for hypotension compared to standard dose) 5
• Average effective dose in prehospital studies was 16.7 mg 3

Absolute Contraindications (FDA Label)

Do not administer prehospital diltiazem in the following situations: 6

• Second- or third-degree AV block without functioning pacemaker
• Sick sinus syndrome without functioning pacemaker
• Severe hypotension or cardiogenic shock
• Atrial fibrillation/flutter with accessory bypass tract (WPW syndrome, short PR syndrome)
• Ventricular tachycardia or wide complex tachycardia (QRS ≥0.12 seconds)
• Recent IV beta-blocker administration (within a few hours)

Critical Safety Considerations

High-Risk Scenarios

• Avoid concurrent nitroglycerin administration, which significantly increases adverse event risk 2
• Patients over age 50 are less likely to achieve clinical improvement 2
• Baseline SBP <140 mmHg, HR <120 bpm, and concurrent vasodilator use predict higher adverse event rates 2

Rhythm Interpretation Accuracy

• Prehospital provider rhythm interpretation shows 92% agreement with physician interpretation (Kappa 0.454), but 8% misdiagnosis rate exists 1
• Critical pitfall: Administering diltiazem for wide-complex tachycardia can cause hemodynamic deterioration and ventricular fibrillation 6
• When in doubt about rhythm diagnosis, defer to cardioversion rather than pharmacologic therapy 6

Guideline Context

AHA/ACC Recommendations

• IV diltiazem is a Class IIa recommendation for acute rate control in atrial fibrillation with rapid ventricular response in hemodynamically stable patients 4
• Synchronized cardioversion remains the treatment of choice for hemodynamically unstable patients 4
• Diltiazem should only be used for hemodynamically stable SVT, not for unstable patients 4

Monitoring Requirements

• Blood pressure and heart rate must be monitored before and after administration 7
• ECG monitoring is essential in patients with any conduction system disease 7
• Resuscitation capabilities including DC cardioversion should ideally be available, particularly for initial use 6

Common Pitfalls to Avoid

1. Do not use diltiazem for wide-complex tachycardia unless supraventricular origin is definitively confirmed—this can cause ventricular fibrillation 4, 6
2. Do not combine with IV beta-blockers within several hours due to synergistic effects on AV conduction and contractility 6
3. Do not administer to patients with decompensated heart failure or severe LV dysfunction—diltiazem has negative inotropic effects 6
4. Avoid in patients already receiving vasodilators or with borderline blood pressure (<140 mmHg systolic) 2