HESI CRITICAL CARE STUDY GUIDE
Dysrhythmia Management, Pacemakers, and Defibrillators
Electrical impulses are generated from SA node (pacemaker of the
... [Show More] heart). SA node is located on top of atrium.
Job of SA node to set heartrate.
SA node fires impulses rate at 60-100 beats per minute.
AV node acts as secondary pacemaker. If SA node doesn’t fire, the AV node can initiate impulses. Problem is that AV node generates impulses 40-60 beats per minute.
Signal starts at SA node travels to AV node travels to R and L bundle branches Goes to purkinje fibers (PF).
The purkinje fibers can act as tertiary pacemakers. Problem is that they fire at rate of 20-40 beats per minute (not necessarily suitable with life).
Dysrhythmia: something is wrong with conduction system.
When we interpret dysrhythmia, we use specific graph paper. Reason is bc graphs in little boxes represent something.
We look at 6 second strip; see hash marks at top of strip. Between two hash marks is 3 seconds. If you want 6 second strip, you have 3 hash marks.
Box: we look at vertical and horizontal. Vertically represents amplitude. Horizontally represents time (what we will focus on). One teeny small box = 0.04 seconds. There are 5 small boxes in one big box so 0.04 x 5 = 0.2 seconds.
One ECG/EKG complex: P, PR interval, QRS, etc
We read left to right for EKG complex
P wave: Atrial Depolarization. Round, upright, uniform, 1 for each QRS complex
PR interval: Measure from beginning of P to beginning of QRS complex. Should be 0.12 – 0.2 seconds. Or 3-5 small boxes.
QRS complex/interval: ventricular depolarization. Skinny or narrow. Measure QRS interval = 0.04 – 0.12 seconds. 1-3 small boxes. Measure beginning of Q to end of S. Most people do not have textbook QRS interval.
ST segment: we do not measure, we look at it. If elevated (above baseline), signs of Myocardial Infarction. If depressed, sign of Myocardial Ischemia. If pt is having heart attack & ST segment is elevated = STEMI (ST elevation MI). If not elevated or hasn’t moved, called non-STEMI. Silent heart attack, if ST is depressed means they have had Myocardial Ischemia at some point in the past. If elevated, pt is probably having heart attack.
-If it is elevated, probably having heart attack. If not elevated, can still be having heart attack.
T wave: round, upright, commonly larger than P wave.
U wave: some people have them, most people do not. If your pt has one, it is sign of hypokalemia. Don’t expect to see a U wave.
QT interval: measured from beginning of Q to end of T. There is no normal, depends on pt. We don’t measure. There are some medications that can prolong QT interval which puts pt at risk for lethal dysrhythmias. Common drug is Amiodarone (prolongs QT interval so we watch closely).
We will not measure intervals on exams but need to know what normal intervals are.
Step 1: determine heart rate. Use 6 second method. Count QRS complex and multiply by 10.
Step 2: determine if rhythm is regular or irregular. Measure R waves. Does the difference between the spaces match up with each space?
Step 3: measure intervals. Measure PR interval. Look for a P wave starting on solid line. Measure beginning of P to beginning of QRS. Measure QR interval; beginning of Q to end of S.
Step 4: look at shape of waveforms. Is p wave round, upright, & uniform? Is QRS skinny or narrow? Is T wave round and upright?
Step 5: identify the rhythm. Ex. Normal sinus rhythm. With sinus, we do not treat the pt bc it is normal.
Sinus Tachycardia: sinus rhythm with rate greater than 100 bpm. Normal physiologic response to stress, anxiety, exercise, red bull, pain, meds, hypovolemia, infection (fever).
Treat if pt is symptomatic; hemodynamically unstable; trying to see if pt is tolerating it or not. Treat underlying cause.
Sinus Bradycardia: sinus rhythm with rate < 60 bpm. Normal for athletes and sleeping. Used to have HR of 85, and HR is 40, signs of decreased cardiac output bc heart is not pumping enough. Symptoms due to heart not beating fast enough to meet demands. Decrease capillary refill, changes in mental status, lack of urine output, SOB, syncope. Heart job is to pump blood to organs, not enough blood to organs so what symptoms would you see?
Treatment: drug of choice is Atropine. Epinephrine. Dopamine. To increase pt HR. If meds do not work, final treatment is pacemaker.
Sinus Rhythm with PAC (premature atrial contraction): atria is contracting too early before ventricles had time to fully repolarize. P and QRS come sooner than it has in the past. Typically see one and won’t see another one for hours or days.
Caused by stimulants: nicotine, caffeine, cocaine. Can sometimes see with electrolyte imbalances or myocardial ischemia.
Pts usually asymptomatic. If you start seeing more, you treat cause; quit smoking, red bull, or coffee.
SVT (supraventricular tachycardia) or Atrial tachycardia: pt will be symptomatic. The heart does not have enough time to fill leading to decreased cardiac output. If the heart doesn’t fill, it can’t eject properly. Has many causes or can show up out of nowhere (without cardiac history). Can see in pts with heart disease, valve disease, or electrolyte changes.
Treat: Ask pt to bear down or do vagal maneuver (act like you are taking the biggest poop of your life); this can decrease your HR.
Treatment: drug of choice is Adenosine (stops the heart). Lift arm bc it has very short half-life (seconds); it’ll get medication to heart faster. 3 way stop cock. One end goes to pts IV; take adenosine in syringe and put it on one side, saline flush goes in another. Push in adenosine and flush right after. Can give it more than once (up to 3 times). 6 mg, 12 mg, 12 mg. If you have given twice & still hasn’t worked, usually don’t give 3rd time but you can. If adenosine does not work, you do cardioversion (shock the heart). When you cardiovert, it resets your SA node.
It doesn’t matter what dysrhythmia we talk about, pt will have manifestations of decreased cardiac output. Whatever dysrhythmia you have, pt will have same manifestations.
Atrial Flutter: atria is not beating, atria is fluttering (not contracting). Single ectopic focus. SA node is initiating an electrical impulse but so is another part of your atrial heart tissue. Atria is getting 2 signals to contract which causes atria to flutter. Causes = heart disease, heart failure, valve disease. Waveforms between QRS are more distinguishable. Treat if pt is hemodynamically unstable.
Atrial Fibrillation: multiple ectopic foci. Not just SA node initiating electrical impulse, but so are multiple parts of the heart initiating electrical impulse. Atria is constantly getting signal to contract. Same causes as A-flutter. Most common dysrhythmia. Waveforms between QRS are more chaotic. Treat if pt is hemodynamically unstable.
Both: blood sits in atria leading to clot. If you cardiovert, the clot could dislodge. You have to do echocardiogram first before you cardiovert. If they have clots in atria, we do not cardiovert them. Put pt on anticoagulants (Heparin in hospital & Coumadin for home). If you are giving pt coumadin, they probably have hx of a-fib.
Treatment for both: rate control (if HR is too fast); Digoxin, betablockers, calcium channel blockers. Drug of choice is Cardizem (Diltiazem); comes as IV continuous med & can titrate to get to HR we want. If med doesn’t work, second treatment is cardioversion (shock heart); hoping that SA node is reset and takes over running of the heart. Surgery includes MAZE procedure or ablation; go in with cautery & burn parts of atrial tissue to hopefully stop ectopic response.
AV block (Atrial ventricular Block)
To identify an AV block, look at PR interval.
Causes of ALL blocks: MI, meds, damage to conduction system, aging heart
First degree AV block: delay; prolonged PR interval. SA node is sending signal but taking AV node longer to receive signal. It is working as it is supposed to, just taking longer. Pts usually asymptomatic.
If it is new finding, assess pt. Make note of (document). No treatment (assess & document).
Second degree AV block type 1 (aka Mobitz or Wenchebach): PR interval will progressively get longer & longer until you drop or lose a QRS complex. “Longer, longer, longer, drop, now you got a Wenchebach”. SA node initiates a signal and travels to AV node. SA node initiates another signal but takes longer for AV node to receive. Same thing happens again but takes longer. SA node fires & AV node doesn’t pick it up at all. Once it drops, it starts all over again. Typically asymptomatic.
Treat them because HR is too slow: atropine. Epinephrine. Dopamine. Usually don’t need a pacemaker.
Second degree AV block type 2 (aka Mobitz II): PR interval is constant. You will have more P than QRS. SA node is firing like it is supposed to. The AV node picks up signals sometimes and sometimes it doesn’t. Pt will be symptomatic; decreased cardiac output. Second degree type 2 do not stay second degree type 2 for long; usually pt will quickly progress to third degree heart block.
Treat bc HR too slow: atropine. Epinephrine. Dopamine. If meds do not work, pt needs pacemaker (if meds don’t work).
Third degree AV block (complete heart block): Fatal rhythm!!! As we go from one complex to another, the PR interval does not stay the same. The PR intervals are not constant & do not follow a pattern. Atria and Ventricles are beating completely independent of one another. SA node and AV node are no longer communicating. It looks regular because ventricles are beating at a regular rhythm but not following any pattern with the atria. Pt will be symptomatic.
Medications will not work. Treatment is pacemaker bc heart is not communicating.
Normal Sinus Rhythm with Premature Ventricular Contraction (PVC): ventricles contract too early. QRS will be wide and bizarre looking; origin of beat is coming from different part of heart. Caused by many things; stimulants, caffeine, tobacco, cocaine. Very common with hypoxemia, heart ischemia, hypokalemia, hypomagnesemia, or acid base imbalances.
Treat if hemodynamically unstable. Treat the cause.
Lethal Rhythms (KNOW THESE)
Ventricular Tachycardia: Stable V-tach & Unstable V-tach. Stable V-tach has a pulse. Unstable V-tach has no pulse. Pt will be symptomatic & will need to be treated. Treatment is based on whether they have pulse or no pulse.
Pulse (stable): amiodarone & cardioversion.
No pulse (unstable): CPR, defibrillation, meds (epinephrine)
Defibrillation, Amiodarone, Epinephrine, Vasopressin CPR
Ventricular Fibrillation: pt will not have a pulse. Check your pt to make sure it is actually V-fib.
Treat: CPR, defib, meds (epinephrine)
Defibrillation, Amiodarone, Epinephrine, Vasopressin CPR
Asystole: very difficult to get pts back.
Treat: CPR & meds (epinephrine). Cannot defib (defib means stopping fibrillation)!
Check in 2 EKG leads: reason is because pts are prone to pulling them off purposely or accidentally.
CPR, Epinephrine, Vasopressin
Dysrhythmia Management
Slow Rhythms
Medications to increase heart rate
Temporary/permanent pacemaker
Fast rhythms
Sinus tachycardia- treat underlying cause
For other fast rhythms
-Valsalva maneuvers, medications to slow heart rate, anticoagulants, cardioversion
Code Management for Ventricular Rhythms
Ventricular Tachycardia
Defibrillation, Amiodarone, Epinephrine, Vasopressin CPR
Ventricular Fibrillation
Defibrillation, Amiodarone, Epinephrine, Vasopressin CPR
Asystole
CPR, Epinephrine, Vasopressin
PEA Arrest
CPR, Epinephrine, Vasopressin– look for underlying cause
Epinephrine: potent vasoconstrictor. Helps shunt all the blood back to heart. Given q3 minutes during a code.
Vasopressin: does same thing as epinephrine. Can’t give any more vasopressin or epinephrine for 20 minutes once medication is given.
Torsades de Pointes: form of V-tach. Pt needs magnesium.
PEA: pulseless electrical activity. Electrical activity in heart has woken up but it is not enough to get mechanics of heart moving. On the monitor, it looks like the pt is in sinus rhythm. Pt will be treated just like asystole.
CPR, Epinephrine, Vasopressin– look for underlying cause
How can it be assessed: H’s
1. Hypoxia: oxygen
2. Hypovolemia: fluids
3. Hypothermia: warming
4. H+ ions (acidosis): bicarb
5. Hypokalemia or hyperkalemia: potassium. Insulin/glucose.
What are the causes and treatments: T’s
1. Tablets (overdose): whatever the antidote is.
2. Tamponade (cardiac): pericardial centises.
3. Tension pneumothorax: chest tube.
4. Thrombosis (coronary): thrombolytics (TPA)
5. Thrombosis (pulmonary): thrombolytics (TPA)
Code Procedure
1. Assess ABCD’s (quickly, no more than 10 seconds)
2. Call a Code Blue and have someone bring the crash cart
3. Begin CPR (need a backboard): Push hard and fast
4. Code procedure is determined by patient’s underlying pathology
Remain present even after the code team arrives!
Medications for Dysrhythmias:
Rate control medications
1. Beta blockers
2. Calcium Channel Blockers
3. Amiodarone
Medications for bradycardia
1. Atropine
2. Epinephrine
3. Dopamine
Anticoagulants
1. Heparin
2. Coumadin
Emergency Medications
1. Epinephrine
2. Vasopressin
3. Lidocaine: old school drug. Antiarrhythmic like amiodarone; we use amiodarone a lot more. Used in case pt is allergic to amiodarone or has been on amiodarone.
4. Adenosine
5. Amiodarone
6. Atropine
Pacemaker:
Delivers electricity to the heart to stimulate depolarization (contraction)
Stimulates atria, ventricles or both (dual)
Indications: slow rhythm, HF, pts post-cabbage.
Temporary
1. Cutaneous
2. Intravenous
3. Epicardial
Permanent: Implanted
Temporary Pacemaker:
Transcutaneous Pacemaker: pace pts through skin.
Epicardial Pacemaker: seen in pts post cabg. Leads are sewn into heart during surgery. Not all pts need to be paced after surgery but are there if needed.
Transvenous Pacemaker: insert pacemaker into one of veins. (intrajugular, subclavian, femoral). Put lead into heart & pt will be hooked up to pacemaker generator.
-Generator has different knobs for different settings.
Pacemaker Terminology:
Mode:
1. Demand (only fires/works if the pts heart does not. Preferred mode. If your heart is able to do it, just let your heart do it.)
2. Fixed (fires no matter what you’re heart is doing)
Rate: depends on pt.
Electrical Output: measure in mA (milli-amps). How much energy is needed to depolarize the heart. How hard does the pacemaker have to work to stimulate the heart.
Sensitivity: important in demand pacemaker. Ability of pacemaker to sense the pts intrinsic rhythm.
Sense-Pace indicator: just a light. Tells you when pacemaker is sensing vs pacing.
AV Interval Indicator: when atria is stimulated and when ventricles is stimulated. Want atria to contract first, wait, and then have ventricles contract second.
Electrical Pacemakers: Separate Atrial and Ventricular Pacing
Atrial Pacemaker: see pacer spike before P wave. Length of spike does not matter.
Ventricular Pacemaker: see pacer spike before QRS. Usually with pacemakers, the QRS gets flipped but doesn’t mean anything when they are upside down.
Biventricular (Dual-Chamber) Pacing: pacemaker that does both. Spike then P, Spike then QRS.
Pacemaker Malfunction:
Failure to Pace (look at top strip; HR 30). Due to battery problem (dead battery), don’t have enough milli-amps, sensitivity problem.
Failure to Capture: pacemaker is firing but the heart is not responding to the pacemaker. (look at bottom strip). Due to not enough energy (low milli-amps) or lead dislodgement (one of pacemaker leads got pulled out of heart).
Failure to Sense: seen in pts with demand pacemaker. Pacemaker is not sensing your heart anymore so you get pacer spikes where they’re not supposed to be. Due to sensitivity problem (sensitivity is not high enough).
Nursing Care:
1. Performed in the EPS lab: you get your pacemaker then you go home
2. Patients usually stay for 24 hour observation
3. The arm adjacent to the surgical site should not be lifted: arm should not be higher than shoulder height because you can dislodge the lead. Overtime, your body grows scar tissue around lead to keep it in place.
4. Incision monitored for infection
5. What are some patient teaching points prior to discharge? Minimal activity for couple of weeks. No MRI. No metal detectors. When you get pacemaker, you get a card telling you what type of pacemaker you have. Microwaves are fine; just don’t curl into it. Tell pt to look for signs that it is not working: check pulse, signs of decreased cardiac output (changes in LOC, feel cold, not peeing enough).
When battery dies, you need a new pacemaker.
Cardioversion: Shocks the heart
1. Depolarizes the cardiac cells so that the sinoatrial node can take over as the primary pacemaker of the heart
2. Indicated for fast rhythms with a pulse: SVT. Vtach.
3. External Cardioversion
Pads and Paddles: pads on chest (like AED pads).
Requirements: pain and sedation (propofol). Pts will feel the shock.
4. Internal Cardioversion
AICD: automatic implantable cardioverter defibrillator. Pts will feel the shock.
Ex. If pt is in SVT for longer than 10 seconds, you can shock them.
Sometimes pts will come into ER because AICD keeps firing.
External Defib
Strong Current
Indicated for Pulseless Rhythms
Procedure
1. Paddle or defibrillation pad placement
2. Good contact with skin (protect from burns)
3. Charge defibrillator to desired setting
4. “I’m clear, you’re clear, everyone clear, oxygen clear”. Make sure no one is touching pt or pts bed.
5. Adequate pressure with paddles
6. Shock
7. Continue CPR 2 minutes, then assess rhythm
3 main difference btwn cardioversion & defib:
1. Cardioversion is for pts with a pulse. Defib is for pts without a pulse.
2. You cardiovert pt at lower joules (lower energy; 50-100 J). You use highest amt of joules we can for defib (up to 360).
3. Cardioversion have to synchronize shock with QRS; we want to make sure the shock is delivered at right time in cardiac cycle bc if not, we can put pt into lethal rhythm. Ex. If you shock pt while ventricles are depolarizing, you can put them in V-Tach.
Study strips separately from treatments & causes & rhythms themselves.
Too Slow: speed up
SB / AVB (2-3)
Atropine, epinephrine, dopamine, Pacemaker
Too Fast: slow it down
Sinus Tachy: treat cause
SVT/AT: adenosine (short half-life, push fast, stop heart, given 3 times).
Afib-Aflutter: Cardizem (diltiazem). Afib is always irregular. A flutter can be regular or irregular.
Cardioversion: echo first with afib & aflutter to check for clots.
Too Ugly : defib
Unstable V-tach / Vfib: defib, CPR, epinephrine
Atrial Dysrhythmia: problem with P wave
Ventricular Dysrhythmia: problem with QRS
Sinus Dysrhythmia: problem with rate. Too fast or too slow heartrate.
AV blocks: problem with PR interval.
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