00:02
All right, hello.
00:03
So the question here reads, a 24 -year -old woman presents to the emergency department with severe diarrhea.
00:10
When she is supine, lying down, her blood pressure is 90 over 60, and her heart rate was 100.
00:17
When she has moved to a standing position, her heart rate further increases to 120 beats per minute, which the following counts for the further increase in her heart rate upon standing.
00:28
Okay, so initially, initially, when you first go from a supine position to a standing position, blood is going to pull in the legs, right? because we just started, just because of gravity, we just started standing up, so blood goes right down to the legs.
00:44
Now this will initially decrease the venous return.
00:47
So the venous return back to the heart is going to be lowered because, again, the blood is pulling in the legs.
00:53
Now this decreased venous return is going to lower the stroke volume.
00:57
And as we know, when the stroke volume is lowered, the heart rate will increase.
01:06
And the reasoning for that is because the heart is trying to maintain the cardiac output.
01:11
We want to keep the same cardiac output, if at all possible...