Critical Care - Week 5 Notes (Cardiovascular - Part 2) Flashcards

Critical Care - Week 5 Notes (Cardiovascular - Part 2)

Learning Objectives

  • Draw the cardiac cycle: P wave, QRS complex, and T wave, noting important segments and intervals.
  • List normal measurements of intervals/complexes.
  • Calculate ventricular heart rate on a six-second rhythm strip/note Lead II on a 12-Lead EKG and use it for rhythm analysis.
  • Discuss what is “happening” in the heart during one cardiac cycle (PQRST). Recognize depolarization and repolarization periods.
  • Identify rhythms by sight, relate pathophysiology, and discuss treatment pathways (stable vs unstable) of entry-level practice rhythms:
    • Sinus Bradycardia
    • Sinus Tachycardia
    • Supraventricular Tachycardia
    • Atrial Fibrillation
    • Premature Atrial Contraction (PAC)
    • Premature Ventricular Contraction (PVC)
    • 3rd Degree AV Block
    • Torsades de Pointes
    • Ventricular Tachycardia
    • Ventricular Fibrillation
    • Asystole

Arrhythmia vs. Dysrhythmia

  • Arrhythmia: NOT normal sinus rhythm.
  • Dysrhythmia:
    • Heart is NOT working properly. A disorder. A disease.
    • More serious than an arrhythmia.
    • Puts the patient’s life at risk.

A & P of the EKG - Little Boxes and Large Boxes

  • Little box: .04 seconds.
  • Big box: .20 seconds.
  • Boxes help determine arrhythmias and dysrhythmias, stable vs. unstable.

Depolarization (Contraction) and Repolarization (Relaxation)

  • Atrial depolarization (contraction): PR interval
  • Ventricular depolarization (contraction): QRS duration
  • Ventricular repolarization (relaxation): T wave
  • "Hills": P and T waves
  • Peak: QRS duration
  • Most important intervals: ST interval (especially in MIs) and the QT interval (which encapsulates all the ventricular activity).
  • The PQRST is the movement of electricity through the myocardium – The heartbeat

Hills, Peaks, and Valleys - Waves, Intervals, and Complex

  • The nurse cares most about the PR interval, QRS duration, and ST interval.
  • Count boxes to determine waves, intervals, and complex measurements.
  • When measuring the PR interval, start right where the P starts to curve up and make sure to go past the Q.
  • PR interval should be .12 to .20 seconds, or 3 to 5 little boxes.
  • A rhythm strip is 6 seconds (multiply number of QRS peaks on a 6-second rhythm strip by 10 to get HR – QRS is the actual pulse).
  • QRS should be .08 to .12 seconds, or 2 to 3 little boxes.
  • QT should be .36 to .44 seconds, or 11 little boxes.

Normal Sinus Rhythm (NSR) - Highest Standard

  • All the complexes are in the same boxes, and everything is the same way every time.
  • Electricity originates in the same place (SA node) and goes to the “finish line” (Purkinje fibers) every single time.
  • Indicates the cardiomyocytes are healthy and contract (depolarize) normally and relax (repolarize) normally each time.
  • NSR is the rhythm by which all other rhythms are judged.

Homeostasis

  • Balance
  • When a pt is not in NSR, homeostasis may fail
  • Perfusing rhythm – Means the cells are getting oxygen d/t a normal rhythm
  • Stable abnormal rhythm (Arrhythmia) - Warning signs. Can still get bad and precipitate into an unstable rhythm. Monitor. Give drugs
  • Unstable rhythm (Dysrhythmia) - Pt will be symptomatic. Use electricity FIRST

How to Know Stable vs. Unstable

  • Put pieces together – Subjective and objective data. Cues to determine if the pt is stable or unstable.
  • Implement decisive interventions to turn the pt around based on symptoms.
  • Steps to Determine Stable vs. Unstable:
    1. Identify the rhythm by sight and define it
    2. Pulse (just because something is happening on the monitor, it doesn’t necessarily mean the pt is alive). There are such things as pulseless electrical activity (PEA) and pulseless v-tach. Go straight to the room to make sure they’re alive
    3. Pathway – Pulling in objective and subjective data to decide stable vs. unstable and arrhythmia vs. dysrhythmia
    4. Treating the symptoms
  • The DETAILED pathway to determine stable vs. unstable – These three body systems tell you if the pt is about to crash out and die
    • Altered mental status (AMS) – Neuro status (brain) – If there’s not enough CPP, glucose, and oxygen
    • Vital signs (HR and BP) – If the HR is extreme (such as HR of 20) or if the BP is extreme (MAP must be over 65 to be a life-sustaining pressure; remember how to configure MAP)
    • Skin – Pale, cool, wet, delayed cap refill (greater than 3 seconds)
    • If a pt has any of these three symptoms, they are UNSTABLE. You MUST go straight to electricity. There is no time to waste

Sinus Bradycardia

  • HR below 60 BPM
  • Make sure to know pt’s baseline
    • KNOW THE PT’S BP
    • Are they symptomatic?
    • Know quality of the pulse. Is it thready or palpable?
    • If it’s not palpable, it’s bad.
  • First-line intervention for bradycardia – Consider atropine sulfate (if the heart has an SA node problem or parasympathetic stimulation)
  • We try atropine, but it doesn’t work for most people. It usually only works for a few minutes
  • If atropine doesn’t work, or the pt has any S/S of instability, go straight to electricity
  • For bradycardia dysrhythmias – Electricity (do pacing)
  • Defib and cardioversion – For fast rhythms
  • Pacing – For slow rhythms ONLY
  • Start low first (DUH)

Pacing Rhythms

  • Atrial paced rhythm (spike before atrial depolarization – before P):
  • Ventricular paced (spike before ventricular depolarization and repolarization):
  • Dual-paced rhythm (spikes before atrial and ventricular) – Pt is fully dependent on their pacemaker:
  • Spiked paced rhythms mean the pacemaker is working – The spikes are called capture
  • EKG is ONLY always right about measurements. It is not always right about STEMIs and rhythms

Sinus Tachycardia

  • HR 100 or greater
  • Most common arrhythmia
  • “Fess up, chap” Pneumonic – Pathophysiological Reasons for Tachycardia
    • F – Fever
    • Embolism (pulmonary) – Any chest problems – Pt gets scanned immediately
    • S – Shock
    • S – Stimulant drugs (licit and illicit) – Cocaine, meth, any kind of amphetamines
    • UP – HR 101 to 150 (SVT is greater than 150)
    • C – Caffeine
    • H – Hypovolemia (dehydration or bleeding)
    • A – Anxiety
    • P – Pain

Supraventricular Tachycardia (SVT)

  • HR over 150 (some physicians define it as being over 160)
  • SVT happens because the electrical circuit in the SA node “loops around,” causing the atria to fire too much and the ventricles to overcompensate
  • YOU CANNOT SEE P WAVES – You can’t keep up with the pulse if you palpate it
  • Pulse will be thready

Nursing Interventions for SVT - Valsalva Maneuver in SVT

  • For pts who are still stable – No AMS, vital signs are normal, and skin condition is normal
  • Pt needs to bear down like they’re having a bowel movement (stimulates the vagus nerve)
  • Pt can put their mouth on a syringe to blow as hard as they can to try to blow the plunger out to stimulate the vagus
  • This stimulates the vagus nerve and fixes 50% of SVT
  • If the pt responds to Valsalva and remains stable, we go to adenosine (6 mg) STAT
    • If the HR is not abated within 60 seconds, we go to 12mg (2 vials of 6 mg)
    • If 12 mg does not work, we go to electricity (cardioversion)
  • If the pt does NOT respond to Valsalva, we go to electricity (cardioversion)

Nursing Interventions for SVT - Cardioversion

  • We receive the pt’s consent (unless the situation is emergent and pt is unresponsive)
  • PRESS SYNC to SYNCHRONIZE cardioversion to the QRS at the lowest possible joules so the energy goes into the myocardium at the absolute best time
  • It sets the heart rhythm back to normal
  • Make sure the pt is LIGHTLY SEDATED (pt is lightly sedated to preserve airway function) for this because cardioversion is PAINFUL and feels like getting kicked in the chest by a horse

Atrial Fibrillation

  • P waves are indiscernible (you are unsure if you see one or not)
  • Stable vs. unstable – Neuro, VS (BP), skin
  • There is high stroke risk for a-fib due to pooling and clotting in the atria breaking off and going into the brain
  • Acute (unstable) vs. Chronic (stable)
    • Acute
      • Electricity
    • Chronic
      • Don’t go to electricity right away
      • Anticoags, calcium channel blockers, and beta blockers
      • Elective cardioversion to get them out of the rhythm

Pathology of Atrial Fibrillation

  • Various focal points in the atria send electrical signals through the internodal pathways
  • The atria quiver instead of sending a distinct contraction (hence no discernible P wave since there is no atrial depolarization)
  • In pts with a-fib, pooled blood may clot, increasing the pt’s risk of cardiogenic emboli and CVA (up to 20% of ischemic stroke is from cardiogenic origin)
  • Some electrical signals reach the ventricles via the AV node
  • The ventricles respond to these signals and begin to contract irregularly

Gold-standard A-fib meds

  • Metoprolol and diltiazem (we will give one or the other); about 50% of pts will convert back to NSR after 1 hour
  • Metoprolol – The gold-standard beta blocker for a-fib
    • 5 mg/5mL – Give 1 mL every minute (it’ll take 5 mins to give 5 mL, 4 mins for 4 mL, etc.)
    • Max dose is 15 mg
    • Give each vial 5 minutes apart
  • Diltiazem – The gold-standard calcium channel blocker
    • Bolus – 25 mg/5mL. Give 5 mg every minute (it’ll take 3 mins to give 15 mg)
    • Drip is 5 mg/hr (if you need more, go up to 10 mg/hr; then if you need more, go up to 15 mg/hr)
    • 15 mg/hr is the max dose

Atrial Flutter

  • 2:1 or 3:1 sawtooth pattern
  • Treatment is the same as a-fib

Ectopic Beats: PVCs (Premature Ventricular Contractions) vs. PACs (Premature Atrial Contractions)

  • Premature Atrial Contraction (PAC)
    • P wave shows up too soon
  • Premature Ventricular Contraction (PVC)
    • Happens after a normal PQRST
    • It shows up out of nowhere
    • Two together are a couplet
    • Two PVCs that look the same are unifocal
    • PVCs that look different are multifocal
    • Three PVCs are a triplet
    • Two normal beats and one PVC and so on are trigeminy
    • PVCs will NOT have a P wave and will therefore NOT have a PR interval
    • PVCs count into the HR
    • PVC Trigeminy (two normal beats followed by a PVC):
    • PVC Bigeminy (one normal beat followed by a PVC):
    • PVC couplet:

Ventricular Tachycardia (V-tach)

  • “Hopping” rhythm
  • Deadly rhythm. The pt WILL go into v-fib and code
  • No pulse – Shock
  • Pulse – Cardioversion
  • If the pt is stable (has a pulse, has good skin color, and a BP), give them an antidysrhythmic

The V-tach Antidysrhythmics

  • Amiodarone (360 mg/200 mL)
    • Has a half-life of one month
    • Give the bolus and hang a drip
  • Lidocaine (100 mg/5 mL)

Torsades de Pointes (AKA polymorphic v-tach)

  • Caused by low mag levels (hypomagnesemia)
  • Twisting and upward turning of the points. It’s all over the place

Ventricular Fibrillation (V-fib)

  • VERY unstable (pt’s pretty much cooked at this point)
  • Pt will look dead
  • No pulse, no BP
  • Call for help right away (push the code button and do CPR right away)
  • Put pads on and shock the pt
  • Give epinephrine as the FIRST drug of the 2-minute cycle
  • During the switch (which should be less than 10 seconds), feel carotid for pulse and look at monitor
  • If there’s still no pulse after the first 2-minute cycle, go back to CPR and give amiodarone or lidocaine
  • Rinse and repeat
  • Only give epi every third minute

What to Do in Dead Rhythms vs Ventricular Rhythms

  • Dead rhythms – PEA (pulseless electrical activity) and asystole – CPR and epi
  • V-tach and v-fib – Shock

Asystole

  • Will NOT always look like a flatline

Third-Degree Block

  • Worst heart block and the rarest
  • Seen on the NCLEX