cardiology

[l.a.m.b, ADN, RN]

help! i am in the cardio section now and i am loving it! its very interesting!! im just stuck on something: i know that CO is influenced by activity level, metabolic rate, stress responses, age and body size, but what conditions can alter the values of cardiac output, MAP and pulse pressure? besides a rapid hr and bradycardia? anyone?

[fiveofpeep]

Well CO = SV X HR

Stroke Volume = preload, afterload, and contractility

you can have decreased CO from an arrhythmia that results in impaired contraction or insufficient diastolic filling time.

i.e. v. fib = no cardiac output because there isnt a contraction going on

or if the SA node goes, you lose atrial kick which accounts for 25% of CO

you could have decreased contractility r/t prior infarction --> scarring

you could have decreased venous return/preload from cardiac tamponade, for ie.

we havent gone over hemodynamics yet and phys was a long time ago so not so sure about pulse pressure and MAP.

theres plenty more examples but I cant think of them

[geek, BSN]

Heart Failure, Aortic Valve Regurgitation both lower output.

[Daytonite, BSN, RN]

cardiac output (co) is the amount of blood that is ejected by the heart each minute. it is dependent on 2 factors. anything that messes with either of those two factors affects the co (cardiac output).

1. the rate of the heart (i.e. beats per minute)
   • affected by
     • electrolytes, medications, oxygen levels, activity level, stress, age, body size

[*]results in:

• bradycardia
  
• arrhythmias (due to electrical abnormalities)
  
• tachycardia

[*]stroke volume (millimeters of blood that are ejected with each ventricular contraction). this is the force of the heart's contraction.

• affected by:
  • increased/decreased preload (ventricular volume: amount of blood coming into the heart at one time)
    
  • thyroid hormone, epinephine, norepinephrine, dopamine, isoproterenol and calcium salt

  [*]results in:

  • changes in blood pressure
    
  • changes in body's fluid and electrolyte status

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save this information. you need to know it to help in understand using the nursing diagnosis of decreased cardiac output. to see specific symptoms caused by results of increased or decreased co, see the defining characteristic listed with this diagnosis ([color=#3366ff]decreased cardiac output)