Step I Isoproterenol

[Ycut]

Can someone explain why there is a fall in systolic pressure with isoproterenol ?

 

[loveoforganic2]

My class notes say it increases systolic BP, decreases (or no change in) MAP, and widens pulse pressure (decreases diastolic pressure)

 

[dragon529]

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.

 

[Ycut]

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

 

[Ycut]

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]

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.

 

[Ycut]

Much thanks for inputs