quick one about vasoconstriction

[effz87]

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hi,
just a quick question regarding arteries.can they constrict completely after a trauma? (i.e. radial artery when slit,etc) obviously not all of them,like the aorta and its big branches are far too big.but is it possible for arteries with a smaller diameter; and if yes at what level would mere elevation and compresion be enough to stop bleeding? thanks!

 

[Slade009]

From what I know yes (and no). Okay let's start with the basics, the first step in Hemostasis is Vasoconstriction to reduce the loss of blood, so Yes. Now about your scenario, remember that arteries are thicker and have more pressure so you will have vasoconstriction but to less of a degree, that is why we apply pressure to reduce blood loss. Vasoconstriction is much more effective in smaller blood vessels. Now you're probably thinking why I said "No" and the reason is because personally I have always found it contradicting that endothelial cells contain Nitric Oxide (NO) and PGI2 which both are potent vasodilators so damage would actually release these primarily, compared to platelets releasing vasoconstrictors and the effects of vascular spasms from pain receptors, causing vasodilation more than vasocontriction (at least initially).

As for your last question:

Can small arteries be stopped from bleeding by mere elevation and compression?
I would say this is a clinical question and somebody else would better suited to answer this BUT my common sense says yes obviously lol. I hope nobody you know is slitting their radial arteries lol.

 

[pd1112]

I don't believe it's possible to constrict completely. Bleeding eventually stops because of the platelet plug and coagulation, not because the lumen closes completely.

 

[solitarius]

^ amputations?

 

[Slade009]

I don't believe it's possible to constrict completely. Bleeding eventually stops because of the platelet plug and coagulation, not because the lumen closes completely.

Oh sorry I didn't read the wording correctly. I now see in his question he asked if they completely constrict. In that case PD1122 is right, obviously it never constricts completely not even in the smallest vessels, and especially in arteries as thick as they are with their high pressures. To completely constrict would be to occlude blood flow to the areas distal to the occlusion. That's why I said "to reduce blood loss" not "to stop blood loss"!

And no I can't see amputation as an need for a slit artery. Vascular diseases, diabetes, unresolving infection of limb, cancer and maybe in cases of severe accidents usually beyond repair can be causes of amputation.

 

[pd1112]

^ amputations?

What about them?

 

[Transposony]

hi,
just a quick question regarding arteries.can they constrict completely after a trauma? (i.e. radial artery when slit,etc) obviously not all of them,like the aorta and its big branches are far too big.but is it possible for arteries with a smaller diameter; and if yes at what level would mere elevation and compresion be enough to stop bleeding? thanks!

If cut across, arteries like radial are likely to stop bleeding on their own due to a combination of retraction/vasoconstriction and platelet plug formation.
That's why slitting wrist transversely doesn't always work as they pass out due to hypovolemia (thereby making them slump down effectively raising their hands) only to wake up later to find that the artery has stopped bleeding.
That is the reason why people who attempt suicide tend to do it in a bathtub where they can immerse the wrist in water to prevent platelet plug formation.
There was a reference to it in "House of cards" where a senator was advised to do it by slitting the radial artery longitudinally rather than transversely.

 

[Jabbed]

If cut across, arteries like radial are likely to stop bleeding on their own due to a combination of retraction/vasoconstriction and platelet plug formation.
That's why slitting wrist transversely doesn't always work as they pass out due to hypovolemia (thereby making them slump down effectively raising their hands) only to wake up later to find that the artery has stopped bleeding.
That is the reason why people who attempt suicide tend to do it in a bathtub where they can immerse the wrist in water to prevent platelet plug formation.
There was a reference to it in "House of cards" where a senator was advised to do it by slitting the radial artery longitudinally rather than transversely.

Never once have I stopped and wondered why the bathtub suicide is a stereotype.

 

[Slade009]

If cut across, arteries like radial are likely to stop bleeding on their own due to a combination of retraction/vasoconstriction and platelet plug formation.
That's why slitting wrist transversely doesn't always work as they pass out due to hypovolemia (thereby making them slump down effectively raising their hands) only to wake up later to find that the artery has stopped bleeding.
That is the reason why people who attempt suicide tend to do it in a bathtub where they can immerse the wrist in water to prevent platelet plug formation.
There was a reference to it in "House of cards" where a senator was advised to do it by slitting the radial artery longitudinally rather than transversely.

Interesting. I don't recall ever being in a lecture of wrist slitting. I thought that based on the high arterial pressures and thickness it wouldn't stop bleeding. I also thought that, based on the normal Bleeding Time 3-10 mins, even if the bleeding eventually stopped in the normal BT range the person would have died of hypovolemia, 3-10 mins of bleeding from an artery. Great to learn new things, I've been studying for this Step 1 so much now that I feel I'm losing track of my curiousity for General Information and am focusing more on Step 1 related possible questions and topics. The closest question I've seen to wrist slitting was I think:

Question: A girl going through depression decided to cut her wrist. After cutting her wrist she was caught and brought to the hospital where on examination the laceration was superficial to the flexor retinaculum. Which nerve was most likely damaged?
(I don't remember the options)
A. Radial n.
B. Median n.
C. Ulnar n.
D. Musculocutaneous n.
E. Axillary n.

Answer: C. The Ulnar nerve is above the flexor retinaculum and the Median nerve is below.