Bradycardia Dosing for Atropine & Dopamine
Patients with a heart rate less than 60 are bradycardic. Bradycardic patients may tolerate a slow heart rate well or present with symptoms indicating they’re unstable. Atropine and Dopamine are two medications commonly given to unstable bradycardic patients and is today’s Pass ACLS tip topic.
When should we consider using the bradycardia algorithm? Because patients can generally tolerate a pulse in the 60s, for ACLS, a pulse less than 50 is generally used as an indication for us to use the bradycardia algorithm.
The signs & symptoms indicating that a patient is unstable are the same for bradycardia as they are for tachycardia and include:
- Hypotension, as indicated by a systolic blood pressure less than 90;
- A sudden decrease in level of consciousness;
- Signs of shock such as pale, cool, moist skin or a delayed capillary refill;
- Signs of acute CHF; or
- Ischemic chest pain.
Patients with ANY of these signs or symptoms should be considered unstable.
Atropine
After ensuring adequate oxygenation and starting an IV, Atropine is the first medication given to unstable bradycardic patients.
Atropine’s dose is 1 mg given rapid IV push and can be repeated every 5 minutes until a cumulative maximum of 3 mg for unstable bradycardic patients. The dose, route, and cumulative maximum may be different when Atropine is used for other conditions. (E.g. Atropine has no cumulative maximum when used for the treatment of organophosphate poisoning)
Because of Atropine’s mechanism of action, use Atropine with caution for patients in a second degree type II or third degree heart block. If the ECG shows an increased P wave rate with no increase in QRS complexes, subsequent doses of Atropine are likely to be ineffective. In this case, start TCP as soon as it’s available. If there’s a delay in TCP, start a Dopamine drip.
Dopamine
The dose of Dopamine for unstable bradycardic patients is 5-20 mcg/kg/min. Start at 5 mcg/kg/min and slowly titrate up until the patient’s BP ≥ 90 mm Hg. Do not administer Dopamine at rates over 20 mcg/kg/min as it causes cerebral and renal vasoconstriction.
The use of Dopamine for bradycardia is an interim measure until TCP can be started.
Atropine and Dopamine increases cardiac oxygen demand so they should be used with caution for patients with myocardial ischemia.
Other free medical podcasts (FOAMed) with additional information about bradycardia, Atropine, & Dopamine can be found on the PassACLS.com Pod Resources page. Some of these are aimed more at experienced providers or ER & ICU physicians.
