Why do the Red Cross and all other blood banks draw blood from your veins? Why does it make a difference?
For that matter, aren’t most (all?) injected drugs given in veins as well?
Seems as though needle-weilding medical folks steer clear of arteries pretty much all the time. Is there a reason?
(Veins carry blood from the tissues back to the lungs for oxygenation; arteries carry oxygenated blood to the tissues. My knowledge base on this subject doesn’t go much farther than that.)
ahem
That is to say, blood pressure is much greater in the arteries, and I suspect as much as a needle prick would end up with a lot of wasted blood.
Ever had ABGs (arterial blood gases) drawn, or had an angiogram? If so, you begin to see why medical folks avoid arteries when possible.
Most arteries are deeper, thicker-walled and more muscular than veins. Often they run along or are near major nerves. They are harder to both access and puncture. You know how they lay the needle almost parallel to your skin when accessing a vein? To reach an artery as in drawing ABGs, they go in at a 45 degree angle or steeper, and they go deeper. It hurts more - a LOT more if they hit a nerve, believe me.
They probably wouldn’t lose a bunch of blood drawing from there - people usually don’t spurt blood after an artery has been accessed. Not out into the air, anyway…BUT the increased pressure in the artery does make it much more likely for blood to escape into surrounding tissue. And it can do so very fast, in large amounts. This will result in a hematoma (large bruise/swelling/pressure) which if unchecked can start impinging on nerves and vessels and cause real tissue damage. That’s why people who have angios or other femoral artery access procedures have a heavy sand bag placed on the groin and lay flat for a time. (They used to anyway - I’ve been out of the field for awhile.)
About administering drugs - most can’t be given intra-arterially. The majority of medications cause arteriospasm, which can cut off blood supply and cause tissue death.
Also keep in mind that while we are messing with said artery, it is supposed to be delivering oxygenated blood to distal points that need O2 to survive. So we try to avoid putting needles there.
To sum up - drawing blood from your artery would not only be considerately more painful, it has potential to cause you some real damage, and the staff would have to spend a lot more time caring for you and monitoring you afterwards to make sure you’re OK.
-sulla
sulla is correct but I would add/clarify a few things:
When you inject something, you generally want it to be diluted as quickly as possible. It will be quickly diluted if it is injected into a vein since the blood will take it straight to the heart where it will mix with blood returning to the heart from the rest of the body. If, on the other hand, it is injected into an artery, it will have to go to whatever particular body part the artery is supplying before it gets diluted.
There are people with really bad veins (small, collapsed, hard-to-find, and/or scarred) from whom it is easier to get blood from an artery. However, using an artery to get a blood sample is considered bad form because of the potential complications mentioned by sulla. (The most important generally being that arteries tend to leak once you’ve punctured them.)
Yes. I, mega the roo, am afraid of arteries.
Just saying that word in my head is making me sick to my stomach, and my body feel heavy.
Bah.
I hate you, arteries.
Not quite correct. Arteries carry oxygenated blood from the heart to the body and the veins carry it back to the heart. Then arteries carry non-oxygenated blood to the lungs where it is oxygenated and returns to the heart via veins.
Mega the Roo, I am laughing out loud. “I hate you arteries”…!
You reminded me of a funny impertinent story a friend of mine told me. She and a couple of friends were camping. A young black bear wandered into camp and started poking around the cooler. The humans were terrified and stood on top of their car, and shouted at the bear. Did they shout something simple? Something intimidating? No, they shouted, “I hate you bear!” at it over and over again until it left with hurt feelings.
Two further points to clarify the excellent responses from Yeah, Sulla and DrMatrix:
Blood does get taken from arteries, usually to check blood gas levels (the partial pressures of oxygen and carbon dioxide). This can’t be done with venous blood because the standard reference values are based on normal levels in arterial blood, hence why O2 should have a much higher level than CO2.
Drugs are given intravenously, when practicable, to ensure a rapid therapeutic effect. The site of action in most major medications is usually found in either the central nervous system, the cardiorespiratory sytem or the endocrine system, all of which are located centrally. Therefore it makes sense to access veins rather than arteries to ensure that medications reach the desired site of action ASAP.
I was drawing bllod from a artery a couple off weeks ago and it SPURTED!!! I mean blood everywhere. I held pressure and it still kept comming out. If the patient hadn’t been drugged up, she would have been freaking out.
michael
::Note to self:
Next time I give blood, request someone other than labdude draw the blood.::
Your arteries are like the water pipes from your local pumping station that lead to your faucets – high pressure and ready to explode.
Your veins are like the drainage pipes at the bottom of the sink or tub that lead to the sewers and back to the processing plant.
If you wanted to make your city’s water supply red by dumping some potent red dye into the system, would you want to dig up and tap water main, or would you just pour it into the sewer?
Peace.
And if you fill up your sink with sponges and let the water run from the faucet and through the sponges into the drain, then you get capillaries!
“If you wanted to make your city’s water SUPPLY red…” (emphasis added) you would want to (have to) dig up the tap water main (unless you live in a city where wastewater is recycled into potable water).