Autonomic Dysreflexia: Pathophysiology (Nursing)

by Rhonda Lawes, PhD, RN

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    00:01 Hi. I'm gonna talk about something that is really scary if you see it in your patients.

    00:05 But so important that every nurse recognize this; autonomic dysreflexia.

    00:12 So let's walk through exactly what happens.

    00:15 See, first of all, just think about your spinal cord, what its job is, what it does, right? It takes information up, it sends information down, it controls your body, right? It's the traffic information highway in the middle of your body, between brain and body.

    00:32 Now, we have a spinal cord injury.

    00:34 I want you to think about this as like being electrical wiring that's what those nerves are.

    00:38 Wherever the level of that injury is, now the wiring is just jacked up for lack of a better word.

    00:45 So here's what happens. If your patient has a painful stimulus below the level of the injury, Now, I'm gonna walk you through the pathophysiology, but just follow me with the big concept first.

    00:56 If your patient has injury below the level, they've some type of noxious painful stimulus coming up to the spinal cord.

    01:03 It sends it to the middle of the spinal cord, right? Comes up to hear, boom, it hits the injury and this is where the signals get all jacked up.

    01:13 So, what are some examples of autonomic dysreflexia triggers? If my injury's here, an overfilled bladder is a really good example.

    01:23 Now, whether your patient has a catheter that stays indwelling, well, we hope they don't because we don't like to keep those for too long if we don't have to.

    01:31 But if their bladder is overfilled, their catheter is blocked.

    01:35 Let me walk you through the steps that you'll see happen in that patient's body.

    01:40 Remember, for autonomic dysreflexia, we're talking about the autonomic functions of my body.

    01:46 Dys; meaning difficulty so I've got difficulty with my autonomic reflexes.

    01:53 Where does it come from? Some type of painful, noxious stimulus at the level below a spinal cord injury.

    02:00 So you have to have a spinal cord injury and some noxious stimuli below the level of the injury.

    02:07 Might be an ingrown toenail that's really sore or infected, might be a bedsore, or it can be an overfilled bladder.

    02:15 Okay. Now let's break down what happens in your body.

    02:18 This is pretty cool if it's not happening to you, but just look at what happens.

    02:22 Because when those signals come up to the spinal cord, they just get all jacked up and things go awry.

    02:30 So here's what happens.

    02:31 Let's say we have a patient whose bladder is overfilled, might be because the catheter is blocked or because we haven't remembered to cath the patient.

    02:38 So we've got too much urine, fills up the bladder and it causes this distention.

    02:44 Okay. I don't need to explain that one to you, right? We all know what it feels like when you have to do the potty dance, right? We have to go so bad it hurts so bad.

    02:52 So I don't have to sell you on, this is definitely noxious stimuli when your bladder is overfilled.

    02:58 Now this stretched bladder sends nerve impulses to the spinal cord.

    03:02 The problem is, when the impulses reach the level of T6, the sympathetic neurons here become activated and they release chemicals called norepinephrine.

    03:14 Okay. Now things are gonna get really excited in your body because norepinephrine, these are chemicals that cause the blood vessels in the skin and the abdomen to constrict and this makes the blood pressure go up.

    03:31 Okay. So those are the first four steps.

    03:34 First, noxious stimuli.

    03:36 In this example, it's an overfilled bladder.

    03:40 Second, that bladder, oh, it's in pain, so listen, I'm hurt and somebody needs to do something, sends a signal to my spinal cord. It hits T6, we end up with norepinephrine.

    03:51 Norepinephrine causes blood vessels to constrict and your blood pressure rises.

    03:57 So first problem, now my blood pressure is on the rise.

    04:02 Now the rising blood pressure is detected by the sensors in your heart and your neck.

    04:06 We call those baroreceptors. Make sure you have that clear.

    04:10 Baroreceptors are the ones that control blood pressure.

    04:12 So my bladder's overfilled, send the message to my spinal cord, T6, norepinephrine squirts out.

    04:18 Then all of a sudden, my blood pressure -- it's really high.

    04:21 The baroreceptors pick up that the blood pressure is high. They send a signals to the brain, right? They've got that. So, the brain has two y -- two ways it can oppose the rise in blood pressure.

    04:34 So I'm gonna keep going over this just so you got it.

    04:37 Bladder overfilled signals to the spinal cord up to T6.

    04:42 You've got this release of norepinephrine that causes my blood pressure to rise.

    04:47 The baroreceptors tell the brain, "Hello brain, their blood pressure's getting really, really high." Now the brain has two ways it can lower blood pressure.

    04:57 First, it sends a message through the parasympathetic vagus nerve to the heart.

    05:01 So it's gonna tell it to do what? If my blood pressure is too high, it's gonna tell my heart to beat slower.

    05:09 Next, the brain sends messages down the spinal cord to make the blood vessels open up again or vasodilate.

    05:15 Okay, so here's the problem. So blood pressure's rising, heart rate's gonna be going lower.

    05:21 This will help you in remembering symptoms that you'll watch for as a nurse.

    05:25 And I'm gonna vasodilate, the message will get down to them to have those blood vessels open up again.

    05:32 The problem is, the injury of the cord stops these messages.

    05:36 So only the blood vessels that are above the injury vasodilate.

    05:42 Okay. So that's not enough to overcome the constrictive blood vessels below the injury, so the blood pressure continues to go up, that's the problem.

    05:51 Okay. So one more time briefly through.

    05:56 Your patient with a spinal cord injury has a noxious stimuli.

    06:00 We're using the example of an overfilled bladder.

    06:03 That distended bladder sends a message to the spinal cord that heads all the way up to T6.

    06:09 You end up with norepinephrine excreted in the body which causes extreme vasoconstriction. Right? So everything's vasoconstricting, blood pressure goes up.

    06:19 The baroreceptors sense that the blood pressure's been elevated, send a message to the brain and the brain responds in one of two ways. It uses these two ways.

    06:29 It will first, right, it tells the heart rate to slow down and it tells the vessels to dilate.

    06:37 The problem is, that spinal cord injury, remember that stops the message so only the blood vessels above the injury dilate.

    06:44 You see when we talked about the symptoms, they have a flushed face that's why.

    06:49 So, this is not enough to control the blood pressure.

    06:52 Autonomic dysreflexia is a fatal condition if it's not treated.

    About the Lecture

    The lecture Autonomic Dysreflexia: Pathophysiology (Nursing) by Rhonda Lawes, PhD, RN is from the course Spinal Cord Injuries and Syndromes (Nursing) .

    Included Quiz Questions

    1. Noxious stimuli below the injury
    2. Infection in the spinal column
    3. Pain above the injury
    4. Increased inflammatory response to the injury site
    1. Norepinephrine
    2. Epinephrine
    3. Cortisol
    4. Adrenocorticotropic hormone
    1. Signal to decrease the heart rate
    2. Signal to increase vasodilation
    3. Signal to increase the heart rate
    4. Signal to decrease vasodilation
    5. No actions will be able to be signaled by the brain to the cardiovascular system.

    Author of lecture Autonomic Dysreflexia: Pathophysiology (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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