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normal PR interval:
0.12-0.20 seconds = 3 - 5 small boxes = less than 1 big box
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normal QRS interval
less than 0.12 seconds = less than 3 small boxes
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What basic cardiac conduction dysfunction can cause a prolonged PR interval?
- conduction block
- e.g. AV block
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What basic cardiac conduction dysfunction can cause a shortened PR interval?
- "short circuit": bypass AV node with aberrant pathway between atria and ventricles
- e.g. WPW
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What is the basic cardiac conduction dysfunction that causes a prolonged QRS?
- ventricular rhythm = rhythm originates in ventricles and not AV/His/Purkinje system
- e.g. His-Purkinje block
- e.g. aberrant pathway: WPW
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What are the "shockable" and "non-shockable" ACLS cardiac arrest rhythms?
- shockable: VF and pulseless VT
- non-shockable: asystole and PEA
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What are the cardiac arrest rhythms?
PULSELESS rhythms: VF, pulseless VT, PEA, asystole
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What is the 1st ACLS IV/IO drug for cardiac arrest rhythms?
- adult: 1mg epinephrine
- kid: 0.01mg/kg epinephrine
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What are the antiarrhythmic drugs for VFib?
- Amiodarone 300mg (kid = 5mg/kg)
- Magnesium 2g
- Lignocaine 1.5mg/kg
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What antiarrhythmic drug do you use for VT?
- monomorphic VT: Amiodarone 300mg (kid = 5mg/kg)
- polymorphic VT (Torsades de Pointes) = Magnesium 2mg
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Do you "shock" all people with VT?
No: must be ARREST rhythm with PULSELESS VT
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What cardiac rhythms make up PEA?
- any cardiac rhythm except VFib, VT, and asystole
- = any rhythm that does not cause perfusion/pulse
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What are the most common causes of PEA?
- 5 H's and 5 T's:
- Hypoxia
- Hypovolemia
- Hypothermia
- Hypo/hyper-kalemia
- Hypoglycemia
- Hydrogen ions (acidosis)
- Toxins
- Tension Pneumothorax
- Tamponade (cardiac)
- Thrombosis (coronary)
- Thrombosis (pulmonary)
- Trauma
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What are Supraventricular Tachycardias?
- = tachycardia with narrow QRS = originates in atrial nodes
- AFib
- A flutter
- re-entry SVT (AV re-entry tachycardia)
- junctional tachycardia
- multifocal atrial tachycardia
- sinus tachycardia
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What is the max conductance of the AV node?
~200 beat/min
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What are common AV node blocking agents? What are they used for?
- = beta blockers, CCB, digoxin (adenosine, vagal manuevers)
- used for rate control with AFib
- DO NOT USE with WPW/accessory pathway arrhythmias
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What are the vagal maneuvers and what are they used for?
- used to treat SVT; increases AV node blockage
- = carotid sinus massage (10-15s)
- = valsalva maneuver (10s)
- = icepack to face (20-30s)
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What population do you want to avoid using adenosine? Why?
- asthmatics
- adenosine can cause bronchoconstriction
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How do you use adenosine?
- used for transient AV node blockage
- used to try to terminate re-entry circuit
- short half life (5-10s)
- must use rapidly with bolus through large bore IV and immediately flushed with 20-30mL NS
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What are typical features of re-entry SVT in kids compared to sinus tachycardia?
- faster rate (>220 in infants; >180 in kids)
- does not vary with level of activity
- has no P-waves
- has no prodrome of illness
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