I have just started to take some actualy nursing courses January 10th, and already I have questions! If anyone could help me, I'd really appreciate it. I think our teacher is going to go over these things during Tuesday's class, but beng confused all weekend will be sure to bother me, I know. So I thought I'd come here for some help.
Alrighy, this is concerning the correlation between blood pressure and pulse rate. From my understanding, if blood pressure is too low, the heart will beat faster (thus an increase in pulse rate) in an attempt to compensate for the lower BP and raise the BP. However, I then read something that seemed to be the opposite of this concept-- that tachycardia (heart rate over 100 BPM) would actually lower blood pressure (because the beats are so quick that there is not enough time for the ventricles to fill up sufficently).
Any input at all is very much appreciated! Thanks everyone.
Jan 15, '05
Hey, sounds like you're on the right track so far - if a person's BP drops from something like fluid loss, they're heart rate will go faster, but that doesn't raise the blood pressure. Maybe you're thinking about cardiac output. An increase in HR will increase cardiac output, to a point - once the HR goes over 135 (?) or some high number, than the cardiac output begins to go down. That's the Starling law. I'm sure that somebody could have said that better - but I do know that an increase in HR doesn't equal an increase in BP.
Jan 15, '05
I believe what happens is immediately the BP would raise, the increase would increase the output (cardiac output = stroke volume x heart rate) but eventually the body 'tires out' and there will be a resulting drop in blood pressure again, the heart rate is so fast that there is not enough time for the heart to fill so cardiac output would drop again.
Jan 20, '05
Actually ... I think you are looking at two sides of the same compensatory system.
If something is going on that causes your pressure to drop (dehydration) - then the heart rate will increase to help maintain the cardiac output.
Alternatively ... if something is causing your pulse to rise (temperature, exercise) there can be a compensatory drop in BP so as not to overdo the cardiac output.
Keep asking questions ... it's the best way to learn!
Jan 20, '05
kind of like which came first, the chicken or the egg? The tachycardia or the low bp? Either way they go hand and hand and both of your presumptions, as stated above are correct.
Of course, if medications are involved, you can have that nasty low heart rate, low blood pressure thing going on. Or tachycardia with hypertension that you might see in a renal patient.
That's why nurses need such advanced education, critical thinking to look at all angles and sides to a situation. You're showing an excellent example of that! Keep up the good work.
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