Atropine Dosing in Trauma
In trauma patients requiring atropine for symptomatic bradycardia, administer an initial dose of 0.5 to 1 mg IV, repeated every 3 to 5 minutes as needed, up to a total dose of 3 mg. 1
Initial Dosing Strategy
The standard approach for trauma patients with hemodynamically significant bradycardia follows the same protocol as other acute care settings:
- Start with 0.5 to 1 mg IV bolus as the initial dose 1, 2
- Repeat every 3 to 5 minutes if bradycardia persists and hemodynamic instability continues 1
- Maximum total dose is 3 mg (representing complete vagal blockade) 1, 3
The American Heart Association's 2010 International Consensus guidelines established this dosing regimen based on randomized clinical trials and observational studies demonstrating effectiveness in both in-hospital and out-of-hospital settings 1. The FDA-approved labeling confirms 0.5 to 1 mg as the appropriate initial dose for antisialagogue or antivagal effects 2.
Route of Administration
Intravenous administration is strongly preferred in trauma resuscitation 1, 2. Endotracheal administration is ineffective during cardiac arrest and CPR, with studies showing only 11-12% positive rhythm response compared to 64-69% with IV administration 4. The poor pulmonary blood flow during arrest (<20% of normal) severely limits transalveolar drug absorption 4.
Pediatric Trauma Considerations
For pediatric trauma patients requiring atropine:
- Dose: 0.02 mg/kg IV with no minimum dose required 1
- This represents a change from older guidelines that recommended a 0.1 mg minimum dose 1
- Recent case series demonstrated effectiveness of 0.02 mg/kg without minimum dosing 1
Critical Caveats in Trauma
Atropine does not improve survival in traumatic cardiac arrest and should not be used routinely in this setting 5. A retrospective study of 136 trauma patients requiring CPR found atropine use did not contribute to survival rates, with an overall survival of only 9.5% 5.
Monitor for paradoxical hypertensive crisis, though exceedingly rare. One case report documented blood pressure reaching 294/121 mmHg approximately 10 minutes after 0.5 mg atropine administration, requiring urgent treatment with IV nitroglycerin and furosemide 6.
When Atropine Fails
If bradycardia persists after maximum atropine dosing (3 mg total):
- Consider epinephrine infusion (2-10 mcg/min) or dopamine (2-10 mcg/kg/min) as second-line agents 1
- Transcutaneous pacing may be considered, though it shows no superiority over second-line pharmacotherapy 1
- In trauma with spinal cord injury, theophylline (100-200 mg slow IV) may be effective for atropine-refractory bradycardia 1
Special Trauma Scenarios
Avoid atropine in complete heart block with wide QRS complex, as it can paradoxically worsen bradycardia and precipitate ventricular asystole 3. This is particularly relevant in trauma patients with conduction abnormalities from cardiac contusion or electrolyte disturbances.
Use caution with concurrent myocardial injury, as the resulting tachycardia can increase myocardial oxygen demand and extend infarction 3.