Cardiac Output NCLEX Flashcards
what is cardiac output
amount of blood ejected from the heart in 1 minute
cardiac output equation
CO=HR X SV
cardiac output units
ml/min
heart rate units
beats per min
stroke volume units
ml per beat
increased heart rate ____ cardiac output
increases
decreased heart rate ____ cardiac output
decreases
heart rate is controlled by what node
the SA node/pacemaker of the heart
SA node beats per minute?
60-80 beats per minute
what are some positive chronotropes that increase heart rate
SNS, Epinephrine, Norepinephrine, Atropine, exercise, age, hormones (T3, T4)
what are some negative chronotropes that decreases heart rate
PSNS, digoxin, metotropolol (any beta blocker), hormones
what is stroke volume
the amount of blood we push out of our heart per beat
increased stroke volume ___ cardiac output
increases
decreased stroke volume ____ cardiac output
decreases
stroke volume can be divided into what 3 categories
preload, contractility, and afterload
what is preload?
this is the amount of stretch/force in the ventricles before contraction
EDV (end diastolic volume, at the end of filling the ventricles right before contraction)
how can you increase preload
increase volume/fluids, vasopressors
how can you decrease preload
diuretics (peeing a-lot), hemorrhage, blood loss
contractility of the heart is dependent upon?
the strength of contraction
(positive ionotrope- increase contractility)
(negative ionotrope- decrease contractility)
what is afterload
force the ventricle must push against to eject blood
what increases afterload?
vasocontriction (plaque, meds, valve stenosis)- greater force to push against to eject blood
increase in afterload ____ stroke volume
decrease ( the heart has to work harder to eject from the ventricles)
what causes decreased afterload
vasodilation
decrease in afterload ____ stroke volume
increases
