Cardio Flashcards
what are complications related to HR, pressure and volume?
Heart rate
o Bradyardia
o Tachycardia
o Arrhythmias
Pressure
o Hypotension
o Hypertension
Volume
o Hypovolemia
o Hypervolemia
what considerations do we have to think about when it comes to heart rate?
-age; neonatal animals will have higher HR than adults
-size/breed; especially for dogs
-resting heart rate; know what their normal is because it could be different from what you would expect
what does a high ETCO2 indicate
good cardiac output
what happens when there is bradycardia
- Adequate diastolic filling
o Volume (Preload)
o Time (Heart Rate) - Too low will directly decrease CO and BP
what is the most important parameter for HR
cardiac output
causes of increased parasympathetic activity in bradycardia cases and examples
Vagal tone
▪ Oculocardiac reflex (trigeminovagal)
▪ Increase pressure in GI
▪ During expiration
Drug induced
▪ Alpha 2-agonists (xylazine, romifidine, detomidine, dexmedetomidine)
▪ Opioids (morphine, butorphanol, hydromorphone, fentanyl)
Reflex mechanism due to hypertension
▪ Baroreflex response (Alpha 2 agonists, Cushing reflex, primary
hypertension…)
what is the most common change we see with anesthesia
Hypotension
when there is bradycardia there is an ______ in parasympathetic activity
increase
what can cause bradycardia? (4)
▪ Cardiac disease; Sick sinus syndrome
▪ Increased intracranial pressure; Cushing’s response
▪ Electrolyte abnormalities; Hyperkalemia
▪ Hypothermia (less than 35 °C)
when do we want to treat bradycardia
▪ Treat if marked bradycardia
▪ For example: Dog with a HR of 38 versus 58
▪ Treat if hypotension or low cardiac output is associated. Is your BP high or low?
▪ Treat if rhythm is markedly irregular and/or dysrhytmias are also present
how to treat bradycardia if the cause is due to vagal tone
anticholinergics
how to treat bradycardia if the cause is drug induced
-reversal, lidocaine
-anticholinergics
how to treat bradycardia if the cause is due cardiac disease
-anticholinergics
-isoproterenol
-pacemaker
how to treat bradycardia if the cause is due to hypertension
control hypertension
how to treat bradycardia if the cause is due to increased intracranial pressure
-control ICP
how to treat bradycardia if the cause is due to hypothermia
warm up
how to treat bradycardia if the cause is due to electrolyte abnormalities
-decrease K+
-calcium gluconate
what happens to CO/BP and filling of chambers when there is tachycardia
- Increases CO and BP
- Too fast will decrease filling time and decrease SV
- Increase O2 consumption, can lead to myocardial ischemia and arrythmias
treatment of tachycardia if the cause is due to superficial plane and/or pain
check depth/analgesia
what can cause tachycardia as a result of increased sympathetic activity (6)
▪ Superficial anesthetic plane and/or pain
▪ Hypotension/hypovolemia
▪ Hypercapnia/Hyperthermia
▪ Drug induced
-Ketamine
-Sympathomimetics
-Anticholinergics
▪ Specific diseases: Phaeochromocytoma, Hyperthyroidism, Heart disease
▪ Hypoxia/Shock
tachycardia is from ______ sympathetic activity
increased
treatment of tachycardia if the cause is due to hypotension/hypovolemia
correct fluids/sympathomimetic
treatment of tachycardia if the cause is due to hypercapnia/hyperthermia
adjust ventilation/cool down
treatment of tachycardia if the cause is drug induced
stop administration
treatment of tachycardia if the cause is due to hypoxia/shock
improve oxygen delivery: fluids, inotropes
how can you recognize sinus rhythm and what do we look at specifically
▪ Only possible if ECG monitoring
▪ Heart rate
▪ Rhythm regular or irregular?
▪ All waves should be present and normal in morphology
▪ P and QRS are associated
types of dysrhythmias (6)
▪ Atrioventricular (AV) block*
▪ Atrial premature contractions (APC)
▪ Atrial fibrillation (AF)
▪ Ventricular premature contractions (VPC)*
▪ Ventricular tachycardia (VT)*
▪ Ventricular fibrillation (VF)
what is not working in cases of AV blocks
Conduction from atria to ventricles is impaired
what is commonly associated with AV blocks
bradycardia
what do you see in 1st degree vs 2nd/3rd degree AV blocks
▪ Slow conduction (1st degree AV-block)
▪ P waves not followed by QRS complex (2nd and 3rd degree)
treatment for AV blocks
▪ Reversal of alpha2-agonist
▪ Anticholinergics (Check blood pressure if alpha2)
▪ Isoproterenol
▪ 3rd degree need pacemaker
causes of AV blocks
▪ Increased vagal tone
Drug induced
▪ Alpha2-agonists
▪ Low dose anticholinergic; Elicit increased parasympathetic tone (transient effect)
▪ Intrinsic cardiac disease
treatment for VPC (many options)
▪ Oxygenation
▪ Improve contractility
▪ Control underlying cause (correct electrolytes, surgery)
▪ Lidocaine
▪ Prevents ectopic activity by blocking sodium channels during action potential
▪ Procainamide
▪ Magnesium Sulfate
▪ Beta-blockers (esmolol)
▪ Amiodarone
causes of VPC (7)
▪ Heart disease, cardiomyopathies
▪ Catecholamine release: pain, stress, inappropriate anesthetic plane
▪ Myocardial hypoxia
▪ Electrolytic abnormalities (Hypomagnesemia, hypokalemia,
hypercalcemia)
▪ Myocardial depressant factors (GDV, splenic tumors)
▪ Arrhythmogenic drugs (thiopental, B1-agonists-sympathomimetics)
▪ Irritation of ventricle, mechanical stimulation
what happens to when there is VPC? what is it associated with? what is prevented?
▪ Ectopic focus in ventricle originates the ventricular depolarization
▪ Not associated with atrial activity
-No P wave
-Premature
-Bizarre QRS
▪ Premature nature prevents adequate diastolic filling
-Pulse deficit
what defines ventricular tachycardia? what can it turn into if its untreated?
▪ More than 3 VPCs in sequence, high HR (dogs > 140 bpm)
▪ Can become ventricular fibrillation if untreated
▪ Tachycardia is part of this dysrhytmia
▪ Some VT with slower rates (HR <100) in dogs do not result in extreme adverse hemodynamic function
what is the cause and treatment of ventricular tachycardia?
Same etiology and treatment as for VPCs
what can low blood pressure indicate
A low blood pressure may mean inadequate perfusion to vital
organs
what is the most common complication during GA
hypotension
how to measure BP (2)
▪ Non-invasive methods: Doppler and Oscillometric
▪ Invasive method: Arterial catheter
what BP value does the doppler give
systolic
causes of hypotension (7), what is the most common in healthy animals
▪ Excessive depth of anesthesia
▪ Hypovolemia
▪ Peripheral vasodilation
▪ Cardiac dysrhythmias
▪ Decrease cardiac contractility
▪ Bradycardia
▪ Tachycardia
what questions to ask and how to respond as part of your hypertension check list? (5)
▪ Is the animal too deep?
-Check plane, decrease anesthetic if possible
▪ Is the animal dehydrated? Bleeding?
-Correct fluid deficits
-How is the heart rate?
-If bradycardia: anticholinergics
-If tachycardia: hypovolemia, analgesia, anesthetic plane, Beta-
blockers
-Treat dysrhythmias
▪ Increase contractility
-Sympathomimetics (inotropes): Dopamine, Dobutamine,
Norepinephrine (NE)
▪ Vasodilation: inhalants, acepromazine, sepsis, inflammation
-Increase vascular resistance (vasopressors): Dopamine, NE, Phenylephrine, Epinephrine, Ephedrine, Vasopressin
what is hypertension usually associated with? how common?
▪ Usually associated with tachycardia in initial phases
▪ Less common than hypotension
causes of hypertension (5)
▪ Inadequate depth and/or analgesia
▪ Drug induced (⍺2 adrenergics, ketamine, sympathomimetics)
▪ Hypercarbia
▪ Hypoxia
▪ Underlying disease
is hypovolemia the same as hypertension
NAUR
are hypotensive patients always hypovolemic
no
are hypovolemic patients expected to be hypotensive
yes
what does hypovolemia result in
decreased blood flow
does hypotension result in decreased blood flow
not always
what % of blood loss needs to occur to see cardiovascular signs
10%
how can you estimate blood loss (3)
▪ Amount in suction bottle
▪ Amount in lap sponges, gauzes
▪ Assess hemodynamic state
what cardiovascular signs will you see if there is >10% blood loss
▪ Hypovolemic patient would be deeper than normovolemic at the same vaporizer setting
▪ More cardiovascular depression at the same vaporizer setting
▪ HR increases although some animals exhibit bradycardia before
tachycardia
▪ BP decreases
▪ CO decreases
▪ Hemodilution: PCV and TS decreases
therapy for hypovolemia (2 categories)
Volume
▪ Isotonic crystalloids, Colloids, Hypertonic saline
▪ Blood products: FFP, Whole blood, RPCs (>15%)
Contractility
▪ Inotropes
▪ Balanced anesthesia; Decreases cardiac depression
vasoconstriction without ____ ____ will not increase cardiac output
fluid replacement
