Acute dissection of Descending Thoracic aorta and Nitropress

[drlee]

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According to the 1994 ITE Question 65:

An elderly man has an acute dissection of the descending thoracic aorta. Which of the following antihypertensive therapies is most likely to extend the dissection?

a) esmolol
b) NTG
c) NTP
d) NTP + beta-blocker
e) Trimethaphan

Answer: C

I have no clue why. Anyone? 😕

 

[ozzie20]

According to the 1994 ITE Question 65:

An elderly man has an acute dissection of the descending thoracic aorta. Which of the following antihypertensive therapies is most likely to extend the dissection?

a) esmolol
b) NTG
c) NTP
d) NTP + beta-blocker
e) Trimethaphan

Answer: C

I have no clue why. Anyone? 😕

Just a guess that because the nitroprusside can increase cardiac output, increasing bloodflow to an area of dissection can increase a tear. Again, only a guess.

 

[anesonia]

Just a guess that because the nitroprusside can increase cardiac output, increasing bloodflow to an area of dissection can increase a tear. Again, only a guess.

I agree- I read not long ago that the increase CO causes more "sheer stress" on the dissection and can make it worse which is why the B blocker is necessary if you give NTP

 

[pgg]

According to the 1994 ITE Question 65:

An elderly man has an acute dissection of the descending thoracic aorta. Which of the following antihypertensive therapies is most likely to extend the dissection?

a) esmolol
b) NTG
c) NTP
d) NTP + beta-blocker
e) Trimethaphan

Answer: C

I have no clue why. Anyone? 😕

All of these are appropriate medications for reducing blood pressure in patients with aortic aneurysms, but a beta-blocker should precede administration of nitroprusside. Without a beta-blocker, the reflex tachycardia associated with nitroprusside will increase dP/dT and shear forces, potentially extending the dissection.

 

[huktonfonix]

just a clarification. SNP does not directly increase cardiac output. It does decrease the SVR/afterload which the heart has to pump against. This may lead to an increase in CO which as the previous poster stated increases the shear forces on the dissection.