So the first line treatment for symptomatic
or unstable bradycardia is gonna be atropine
which is a parasympathetic antagonist.
Now we talked about how one of the causes of bradycardia
is high parasympathetic tone.
So you can imagine blocking the parasympathetic input to the heart
is potentially gonna speed the heart back up.
The dose is generally gonna be half a milligram given every three to five minutes
You can give a max of three milligrams
before your patient is maximally atropinized,
and there’s not gonna be any additional benefit.
You also can use infusions of sympathomimetic
so dopamine or epinephrine can be used to raise the sympathetic tone,
it’s given as a continuous infusion and titrated
to the desired blood pressure and heart rate parameters.
But you wanna be really careful with these
if you think ischemia is the underlying cause for your patient
because both dopamine and epinephrine
increase myocardial oxygen demand
and can exacerbate ischemia.
So these should be really used with caution.
More typically if we have a patient who has symptomatic bradycardia,
we’re gonna move to pacemaking rather than medical management.
So transcutaneous pacing is the immediate first line pacemaking approach
that we used in the emergency department
because it can be completed very quickly.
So you accomplish this by putting external electrodes
or pacer pads on the patient
and you can see the location on the diagram where those go on the body.
You always wanna make sure your patient has oxygen,
they’re on a cardiac monitor and they have adequate IV access
before you initiate pacing.
And when possible you wanna sedate your patient.
Now, if they're too unstable to do that,
and you need to initiate pacing immediately,
you can for go sedation.
But generally you know, you’re actually shocking the patient repeatedly
when you pace them and it’s quite uncomfortable for them,
so you wanna provide sedation whenever it’s feasible to do so.
The way you initiate transcutaneous pacing is actually pretty straight forward.
So you’re gonna sat your defibrillator to the pacer setting.
You’re gonna set a heart rate of 80 to a hundred.
So you wanna make sure that heart rate is significantly higher
than the patient’s current heart rate,
so that you’ll be able to tell when you get pacer capture.
You’re gonna start off with the low amperage,
a low amount of energy,
and you’re gonna gradually dial it up until you get capture.
Meaning each pacer's spike produces QRS complex.
Once you get captured, you gonna go up by ten milleamperes.
And that’s where you’re gonna stay for the whole time your transcutaneously pacing.
And again, once you have pacing established,
you definitely wanna provide sedation
and that sedation should be continual
until such time as you terminate transcutaneous pacing.
Because this is actually physically shocking the patient
repeatedly, 80 to a hundred times per minute,
and it’s quite uncomfortable for a conscious person.
Now, your more definitive alternative is transvenous pacing.
And this is something that's a little bit more complex to do,
it definitely requires specific training,
and it’s not something you would wanna do in the emergency setting
if you haven’t specifically learn how to do it.
But basically the way the procedure works,
is you introduce a central venous catheter that’s large in caliber,
it's a sheath that will let you put pacer wires through it.
Your two options for catheter insertion
are the right internal jugular which is marked here,
or the left subclavian vein.
What you're gonna do once you have your sheath in place,
is you’re gonna put electrodes through the sheath,
and advance them through the venous system
into the apex of the right ventricle
which is marked right there on the diagram.
You have an external control panel
that allows you to control the heart rate and the amperage.
And the nice thing about this, is that it’s painless for the patient.
I mean obviously introducing the sheath initially can cause some pain.
But once you have the sheath in place
and you have the electrodes inserted, the patient can’t feel this,
the way they can feel transcutaneous pacing.
So you don’t need to provide any ongoing sedation.
It’s also a much more reliable than transcutaneous pacing.
So you basically have an electrode that’s in physical contact
with myocardium and it’s pretty easy to get pacer capture,
and to initiate cardiac contraction with each pacer impulse.
So bottom-line, is that fortunately the vast majority of bradycardias
are not emergencies and emergency treatment
is only necessary for unstable patients.
Now in the long term, some stable patients
might require treatment but in the ED setting,
we’re only gonna be addressing bradycardia, if the patient is unstable.
You can use the EKG to differentiate between different bradycardia types,
and it’s very important that you do so
because the different bradycardias have different pathophysiology
and different prognoses.
So you wanna make sure you know what rhythm you’re dealing with,
so you manage it appropriately.