There are three medications used in the bradycardia algorithm: atropine, epinephrine, and dopamine. Read about each drug and its use within the bradycardia algorithm below.
When symptomatic bradycardia occurs, the primary objective is to identify and treat the cause of the problem. Medications are indicated if symptomatic bradycardia cannot be corrected by treating an underlying cause or if the cause cannot be determined.
2020 AHA UpdateThe single-dose administration of atropine was increased from 0.5 mg to 1 mg. Now give 1 mg for the first dose and then repeat every 3-5 minutes at the 1 mg dose. Also, the dopamine infusion rate for chemical pacing was changed to 5-20 mcg/kg/min. The previous rate from the 2015 guidelines was 2-20 mcg/kg/min.
Atropine
Atropine is the first line medication for the treatment of bradycardia. The administration of atropine typically causes an increase in heart rate. This increase in the heart rate occurs when atropine blocks the effects of the vagus nerve on the heart. When the vagus nerve is blocked, the SA node increases its rate of electrical discharge and this, in turn, results in the increased HR.
Use atropine cautiously in the presence of myocardial ischemia and hypoxia because it increases oxygen demand on the heart and can worsen ischemia.
The dosing for Atropine is 1 mg IV every 3-5 minutes as needed, and the maximum total dosage for administration is 3 mg.
Atropine should be avoided with bradycardia caused by hypothermia and, in most cases, it will not be effective for Mobitz type II/Second-degree block type 2 or complete heart block.
You may have read that atropine is not effective for Mobitz II (2nd-degree block type II) and complete heart block (3rd-degree block)
Click here to find out why
Atropine for Mobitz II and Complete Heart Block
In your AHA provider manual, you will see it stated in the bradycardia section that atropine is not effective for Mobitz II and complete heart block. I have had a number of people ask why it is not effective. Read below for the explanation.
First, let’s look at atropine and how it works. Atropine increases the firing of the sinoatrial node (atria) and conduction through the atrioventricular node (AV) of the heart by blocking the action of the vagus nerve.
With 3rd-degree block, there is a complete block and disassociation of the electrical activity that is occurring in the atria and ventricles. Since atropine’s effect is primarily on the SA node in the atria, a 3rd-degree block would prevent its effect on the SA node from influencing the rate of ventricular contraction which is needed to improve perfusion.
With Mobitz-II, aka, second-degree AV block type II, the situation is similar. There is a partial block in the electrical impulses from the atria (SA) to the ventricles, and thus the effects of atropine would not significantly change the status of the ventricles. This block can also rapidly progress to 3rd-degree block.
To summarize, atropine may speed the firing rate of the SA node (atria), but the ventricles are not responding to anything the atria (SA node) puts out. Thus, the heart rates will not increase.
There may be some action at the AV-node with atropine, but the effect will be negligible and typically not therapeutic. In most cases, atropine will not hurt the patient with 3rd-degree block unless they are unstable and cardiac pacing is delayed in order to administer atropine.
Caution with Atropine
It is important to note that Mobitz II and complete heart block may be associated with acute myocardial ischemia. If atropine is used when there is ongoing myocardial ischemia this may worsen myocardial ischemia because of an increase in oxygen consumption. The increased heart rate will also reduce the diastolic filling time which may worsen coronary perfusion.
Since new-onset Mobitz II and complete heart block are commonly associated with myocardial infarction, it is recommended to maintain a slow HR (50-60) in order to increase the diastolic filling time. Any time you increase HR, the diastolic filling time is reduced and this reduces the coronary perfusion.
Transcutaneous pacing should be the first line action for symptomatic Mobitz II and symptomatic complete heart block. It is very safe & less painful than in previous times due to technological improvements. Research has shown that most individuals can tolerate > 15min of transcutaneous pacing without significant pain or discomfort.
Now back to the bradycardia drugs
Epinephrine and Dopamine
Epinephrine and dopamine are second-line drugs for symptomatic bradycardia. They are both used as infusions in the bradycardia algorithm if atropine is ineffective.
ACLS guidelines state that if bradycardia is unresponsive to atropine, an equally effective alternative to transcutaneous pacing is the use of an IV infusion of the beta-adrenergic agonists (dopamine or epinephrine).
Dosing:
IV infusion for bradycardia:
- 1mg epinephrine is mixed with 500ml of NS or D5W. The infusion should run at 2-10 mcg/min and titrate to the patient’s response.
- Dopamine 400 mg is mixed with 250 ml NS. Begin the dopamine infusion at 5 to 20 mcg/kg/min and titrate to the patient’s response.
The goal of therapy is to improve the patient’s clinical status rather than target an exact heart rate.
Precautions
Prior to the use of ACLS drugs in the treatment of symptomatic bradycardia, contributing factors of the bradycardia should be explored then ruled out or corrected.
karen says
Just wondering……..Here’s the scenario….Pt on vent, started desatting, 70’s, then hr 26, called code.
I asked for atropine, but they gave epi, then started dopamine gtt. Why not atrpoine first?> They never gave atropine so I was wondering have the guidelines changed?> Pplease respond. BtW, we lost the patient.
Jeff with admin. says
It would be nice to know what the pateint’s diagnosis was, but that is o.k.
It sounds like the code was caused by a respiratory issue (dislodged ET tube, mucus plug, or pulmonary embolus).
AHA rule #1 is tailor the interventions around the cause of the arrest which in this case seems to be respiratory in nature.
The patient’s oxygen saturation decreased into the 70’s and then the patient developed bradycardia most likely related to the hypoxia.
ET tube placement should have been checked by auscultation. After this, the patient should have been suctioned, placed on 100% oxygen, and ventilated with a bag valve mask.
Questions:
1.Did anyone auscultate this lung sounds to check ET tube placement?
2.Did he get switched to a bag valve mask?
3.Did the patient have good rise and fall of the chest with ventilation?
If all of this was done properly and a respiratory cause was ruled out or not effective (i.e., no positive move of the oxygen saturation, improvement in pt. condition) and bradycardia occurred then atropine would have been appropriate according to AHA guidelines.
After atropine, transcutaneous pacing would have been reasonable if the bradycardia was sustained and not degrading into asystole or PEA.
Epinephrine IV push does diverge away from the bradycardia algorithm, but would have most likely produced a similar effect to atropine (increase heart rate).
Epinephrine drip is appropriate as a drug replacement for TCP.
The only problem is if the patient’s arrest was caused by a respiratory issue and you give atropine or epinephrine (increase heart rate) then you actually can make the problem worse by increasing oxygen demand on the heart.
Always tailor the interventions around the cause of the arrest. The algorithm diagrams merely represent the most common pathway for treatment of arrest conditions.
This sounds like a respiratory issue and should have been treated as such.
I hope this answers your question adequately.
Please let me know if you have any other questions.
Kind regards, Jeff
Neal says
symptomatic bradycardia in pt with glacoma-is atropine still given?
Jeff with admin. says
Narrow angle glaucoma is a relative contraindication. You can skip atropine and go straight to transdermal pacing. Kind regards, Jeff
dma213 says
you know, this is much better and easier to understand, has all the info in the book but much easier to follow…
so glad i joined 🙂
rannie says
Hi,
what about the other drugs used in the ACS or Stroke (eg Verapamil, Nitroprusside etc) which are not elaborated in your site and neither in the ACLS book? Will they ask questions about them as well or is it enough to know about the common drugs used in your site?
Ahmad hosnee says
Do you think that atropine not recommended for complete heart block as its a distal conductive system impairment that make the increased SA node impulses useless ?
So ventricular pacing becomes the first choice.
Jeff with admin. says
If the complete heart block is a result of a distal conductive system impairment then the atropine would be ineffective and could even complicate things by increasing myocardial oxygen demand. If it is clear that the complete block is not associated with an MI, atropine can be given while waiting for pacing to be initiated. It may be effective for a High Purkinje or AV Nodal escape rhythm. —-Kind regards, Jeff
Jacquelyn Costales says
This is really helpful. Thank you so much.
Donna Prochaska says
Some of the comments/answers are very helpful. This is also my first time, and this site has helped a great deal. The hardest for me, is to learn the strips, and like sites that continuously run strips. Thanks again.
Jennie Williams says
I am going to go back and read up on this again but if I can’t find it, can you remind me why atropine is not effective for Mobitz type II/Second Degree Block Type 2 but it IS effective in 2nd degree Wenckebach? Since they are both a result of SA node dysfunction (if I remember correctly), I am struggling to understand why it will be effective in one but not the other. Your input would be greatly appreciated. 🙂
Jeff with admin. says
It’s not so much that the Atropine won’t work with a Mobitz II. In fact it
will probably increase the HR, but this will induce more ischemia as the HR
will double or triple, reducing diastolic filling time and worsening
coronary perfusion. Mobitz II is almost always associated with myocardial
infarction. You would like to keep the HR slow (50-60) to increase diastolic
filling time. Anytime you increase HR, the diastolic filling time is what
takes the biggest hit. Mobitz I is not usually associated with MI.
The comment “Since they are both a result of SA Node dysfunction” is
incorrect. The SA node is intact in both Mobitz I & II. It is the AV node
that is having problems conducting the impulse down to the Bundle Branches.
Transcutaneous Pacing should be the first line in Mobitz II. It is very safe
& less painful than in previous times due to technology improvements.
Research has shown that most individuals can tolerate > 15min of
transcutaneous pacing without too much difficulty.
afsane says
ur structures r great..thanks alot..
i just wanted 2 know that atropin has chronotropic effect or inotropic?
and in sympthomatic bradycardia , which agent is effective? positive chronotropic or inotropic?
thank u…
Jeff with admin. says
Atropine is a positive chronotropic agent. This means that it increases heart rate. Positive chronotropic agents are effective for increasing heart rate. —Jeff
Dave says
An ACLS instructor told me that Atropine is not positive chronotropic, is that right?
Jeff with admin. says
Your instructor has misinformed you. Atropine is a positive chronotropic agent. The word chronotropic means affecting the time or rate. Thus positive chronotropic means increasing the rate. Here is a link that verifies the above: http://en.wikipedia.org/wiki/Chronotropic
Under the heading positive chronotripic, atropine is listed 2nd.
Kind regards,
Jeff
David Dunscombe says
I have yet to see a negative comment, as you can see I have logged a lot of hrs. and learned a great deal, first time for taking this course, so need the time and great instruction.
azaa says
how to treat patient with inferior MI &PR=44/min & BP systolic 90
Jeff with admin. says
Immediate PCI. (PCI) percutaneous coronary intervention.
dr john cardozo says
Hey this is a great site
Kindly expedite these pages underconstruction
Waiting anxiously to read these pages
Keep up the good work
Efe Ototahor says
GREAT! Very simple to study, will recommend this to my colleague.
Tracy Pickett says
Hi, Im 5th semester student RN and I LOVE your site…Im precepting soon in CCU and any drug info. is greatly appreciated, any info at all to help me remember! God Bless!