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Pulseless Electrical Activity (PEA) – Emergency Medicine | Lecturio


[Music] all right we’re gonna switch gears a little bit now and talk about pulseless electrical activity and this is one of my favorite rhythms to think about because it’s physiologically much more complex and interesting than v-fib and v-tach and there’s a broad differential that you’re gonna learn about so what is PE a PE a again stands for pulseless electrical activity and what that means is that there is organized electrical conduction on the monitor normal-looking QRS complexes with P waves and T waves and all the things you expect from a cardiac rhythm however there is clinically no pulse so normal looking activity on the monitor but no pulse when you actually palpate the neck what is the single most important intervention for PE a it’s a little bit of a trick question the most important intervention is to figure out what caused it and fix that so unlike v-fib and v-tach where we do the same thing for everybody across the board regardless of the cause in the case of PE a we’re only going to be able to make our patient better if we can figure out the cause and treat it now of course we’re gonna provide supportive care in the mean time but ultimately our goal is going to be to make a diagnosis there’s two major mechanisms of PE a that I’d like you to be aware of one is the empty heart and the other is EMD or electromechanical dissociation and we’re going to compare and contrast these a little bit so in the case of an empty heart the heart is conducting normally there’s nothing wrong with the hearts conduction system you know if I were to get shot right now in the aorta and all of my blood volume were to pour out on the floor there’s nothing wrong with my heart it’s gonna conduct perfectly normally in the case of electromechanical dissociation the heart is also conducting normally electrical activity in the heart is preserved however when the heart is empty again if I get shot in the aorta and all of my Bloods on the floor there’s nothing wrong with my heart itself so at least in the short term it’s going to keep Contracting just as hard and fast as it can to try to perfuse my body so contraction occurs and it’s normal however that contraction ultimately is ineffective right because no matter how hard the heart squeezes if there’s nothing inside of it if my blood is on the floor and not inside the heart the heart’s not going to fill it’s not going to send blood out to the body by contrast an electromechanical dissociation there are normal cardiac action potentials that yield the pretty spikes that we see on the cardiac monitor however these action potentials do not yield cardiac contraction so the heart’s conduction is normal but the contraction is either absent or so impaired that it doesn’t produce a pulse ultimately empty heart peña is caused either by hypovolemia as I mentioned with the example of all of my blood volume being on the floor or it can be caused by some kind of obstructive process that prevents the heart from filling so examples of those are things like cardiac tamponade you’ve got a big collection of blood around the heart it physically compresses the heart the heart can’t fill normally so it can’t send blood out to the body normally same with tension pneumothorax right you have a huge high pressure air collection in the chest it’s going to mechanically squish the heart and prevent normal filling these are all empty heart forms of peña by contrast electromechanical dissociation is going to be caused by systemic Arrangements in the body so these are going to be things that affect energy metabolism such that the heart is able to produce the energy to maintain normal conduction but it’s not able to maintain the energy to enable mechanical contraction and as you can imagine contraction requires a lot more metabolic energy than conduction so it’s going to be the thing to go in the setting of severe derangements of metabolism in the body so what’s your differential diagnosis of peña there’s a common mnemonic that’s used which is the HS and the t’s and I’m going to tell you a secret I don’t love this because it doesn’t force you to think about it physiologically but a lot of students find it useful so we’ll go through them hypovolemia like we already mentioned if you don’t have any blood volume your heart’s gonna be empty not your heart’s not gonna have good output hypoxia well how do we make energy in the body we make it out of oxygen and glucose so if you’re hypoxic you’re aerobic metabolism is going to be ineffective and you’re not going to be able to produce the normal amount of energy to drive cardiac contraction so it’s potentially a cause of PE a acidosis or hydrogen ion because you know we had to make it start with an H in that kind of situation you know there’s different Optima for every process in the body there’s pH optimum temperature optimum and physiologic processes just don’t work right when you have extreme arrangements of those Optima so in the case of profound acidosis the heart actually can’t squeeze normally so even though conduction is intact the cardiac contraction is not hyper or hypokalemia it has to be pretty profound but severe derangements of potassium can actually precipitate PE a hypothermia like I mentioned for the same reason as acidosis if the body’s really really cold the heart’s not going to be able to contract normally we talked about tension pneumothorax as a cause of empty heart PE a and the same for tamponade there’s a number of toxins that can potentially produce PE a by uncoupling energy metabolism from normal cardiac contraction massive m eyes can cause such profound reduction in cardiac squeeze that you can’t actually clinically detect a pulse and massive PE s can cause such severe obstruction of normal pulmonary blood flow that they basically cause empty heart PE a the same way any other obstructive cause would so with PE a it’s even more important than with other types of cardiac arrest to understand the underlying cause and to identify what’s going on so you want to get as much information as you can about the circumstances that led up to the arrest what was the patient doing when it happened did the patient have any symptoms beforehand they suddenly clutch their chests and complain of pain or were they gasping for breath did they turn blue did they attempt suicide was there some type of trauma all of these things will help you narrow the differential for peña and treat the patient accordingly for physical exam it’s especially important if you don’t have a good history which in many cases of cardiac arrest you won’t but if the patient has any signs of physical trauma when you look at them maybe you’re gonna think more about hemorrhage as a potential cause of PE a or tension pneumothorax if the patient’s pregnant that should make you think about pulmonary embolism if they have a dialysis catheter hanging out of the chest that’s going to make you think about hyperkalemia etc so physical findings can potentially give you clues that will help narrow your differential and prioritize your treatments so that you can help the patient with PE a another nice adjunct we have nowadays is bedside ultrasound so ultrasound is a great extension of physical exam it allows us to look inside the body in ways that we couldn’t before and identify in real time is there a pericardial effusion present or signs of tamponade is there evidence of a pneumothorax which is seen by absence of lung sliding on ultrasound is there an abnormal cardiac ejection fraction maybe the heart’s just barely beating maybe the IVC is really distended suggesting that the patient is volume overloaded or maybe it’s really collapsible in tiny suggesting that they’re dehydrated so ultrasound is especially good for cardiac tamponade and pericardial effusion this is an example of a cardiac ultrasound where you can see some of the chambers labeled but most importantly you see a large pericardial effusion which is outlined here on the screen and that’s big enough that you would certainly want to perform a pericardiocentesis and get rid of that to see if that helps the heart beat more effectively and improves your cardiac output there’s also the inferior vena cava which is a great overall indicator of your patient’s volume status so like I mentioned before patients who are really volume depleted either from dehydration may be from a diarrhea illness or hemorrhage blood loss the patience will have very very skinny collapsible inferior vena cavas so if your vena cavas tiny or if it collapses down to nothing when you breathe in deeply that suggests a patient in need of volume whereas if your IVC is normal in calibre and it doesn’t collapse down to nothing or maybe it’s even distended that suggests that your euvolemic or potentially even volume overloaded so this can help kind of guide your thinking a little bit about the patient and particularly for patients who have evidence of intravascular volume depletion by giving them fluids or blood you can potentially reverse their PE a I didn’t have an image to show you here but I’ll also just mention ultrasound is very commonly used to evaluate for tension pneumothorax there’s a number of tests that that you can do that’ll help you quickly identify that at the bedside without moving the patient [Music]

5 Comments

  1. Sami Sami
    Sami Sami August 28, 2018

    excellent

  2. NNEKA A.
    NNEKA A. August 28, 2018

    Shot in the aorta … u definitely work In Baltimore

  3. NNEKA A.
    NNEKA A. August 28, 2018

    Great lecture ✌🏾✌🏾

  4. AngelOne11
    AngelOne11 August 28, 2018

    I enjoyed this lecture. Thank you!

  5. Priya Tripathi
    Priya Tripathi September 18, 2018

    👍

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