Oct 20, 2012
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ImageUploadedByTapatalk1360631820.793579.jpg

Can someone explain why there is a fall in systolic pressure with isoproterenol ?
 
Aug 14, 2012
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My class notes say it increases systolic BP, decreases (or no change in) MAP, and widens pulse pressure (decreases diastolic pressure)
 

dragon529

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Jul 25, 2007
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Isoproternol only affects B1 and B2. Through B1, it increases heart rate and through B2 it vasodilates. The vasodilation cause drop in blood pressure.

Compare with norepinephrine which affects alpha 1,2 and beta 1 so it vasoconstricts via alpha1 and there's a reflex decrease in heart rate because of that.

I know you took this from FA and that little paragraph underneath sums it up.
 
OP
Ycut
Oct 20, 2012
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Isoproternol only affects B1 and B2. Through B1, it increases heart rate and through B2 it vasodilates. The vasodilation cause drop in blood pressure.

Compare with norepinephrine which affects alpha 1,2 and beta 1 so it vasoconstricts via alpha1 and there's a reflex decrease in heart rate because of that.

I know you took this from FA and that little paragraph underneath sums it up.
B2 stimulation-Vasodilation-decreases (TPR) and as a result diastolic BP
B1 stimulation-positive inotropism+ chronotropism-which must increase (Stroke volume) and as a result systolic BP
 
OP
Ycut
Oct 20, 2012
101
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I guess the primary bump on the picture is the result of increased stroke volume and subsequently tachycardia compromises filling which is why systolic BP decreases

Any other suggestions ?
 

dragon529

MS-III
10+ Year Member
Jul 25, 2007
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If you inject isoproternol, BP has to decrease for 2 reasons. Through beta1, you pump the heart stronger and faster then you'll get reflex vasodilation. Also, through beta2, it vasodilates because that's what it does.

You have to think about the reflex the drug is indirectly causing because our body is constantly trying to maintain homeostasis.