When the doctor/nurse takes blood from you, why do they try to find a vein, not an artery? And also why is this mainly done on the arm as opposed to other parts of the body?
In: Biology
Just to add a bit, peripheral IVs are mainly done on the arm for convenience. It’s easier for patients to manage and convenient for people to start them there. You can do them on the hand, as well, but the veins are smaller and it’s not an appropriate site for when you want higher flow IV fluids or etc. (CT contrast, for example, won’t be administered through an IV in your hand but can go through one in your arm).
But we can and do start them pretty much anywhere that has a large enough vein/can be accessed/is appropriate for the situation. In an emergency we can even drill a hole into one of your bones to put the IV in there instead of in a vein.
The arteries have higher blood pressure so there would be a lot more bleeding.
They are alose deeper down in the tissue. So just for this reason, you use veins.
The arms are primarily used because people care less if you touch them, easy to get access, and move and there are shallow and large veins in the elbow area. You can in a simple way put a tourniquet around the arm so the veins increase in size.
The tourniquet usage make the arms and legs the best spot to find veins.
If there is one location with easy access, you can just sit down and stretch out your you arm, none or very little clothing need to be moved a people do not care if you touch that part, Why would you not primary use it?
If that fails for some reason like lots of scar tissue on the veins you usually do it on the feet with shallow veins and part of the body to access and another location people do not care if you touch.
Thre is likely shallow veins in the knees but to get there the patient would need to lay down on this stomach so it is a very unpractical location.
You do not use the hand to take blood in large part because it is a more sensitive area and if there is some bleeding below the skint it is a lot more visible.
But you use it for intravenous therapy because you can use tape to attach the catheter and the lines to the skin a simple way. the backside of the hand is a stable area that in most situations is not in contact with other parts of the body, a chair, bed etc so it is a location where is the leas in the way for the patient.
Veins are directly under the skin, arteries are not. Also it would be harder to deal with the bleeding. On ICU’s there are arterial catheters which measure the blood pressure and allow you to take blood from patients. The blood from an artery enables you to monitor the blood gases. Arms are easy to reach and it’s not as painful. I also have taken blood from someone’s feet for example. With baby’s you take it from the head.
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Arteries actually spray, like, in the movies kinda. Arteries are also Kinda protected in the body and buried deeper.
Arteries also are wrapped in nerves, veins not so much. Arteries hurt to poke. However, we do poke arteries for doing Arterial Blood Gas analysis. We poke people in the wrist where you can feel the pulse. It hurts, people hate it.
I have drawn blood from many different places on a human. Neck, feet, groin, legs, front of shoulder, forehead, yeah lots of places.
First post here. I’ve been a phlebotomist for 16 years and specifically on pediatrics for the last 13.
A lot of people have already mentioned the pain factor but you also want to think about the sample type and the test results you get from each. Veins have venous blood, arteries have arterial blood and capillaries give capillary blood.
Venous blood is on its way back to the heart, so you get your base line results there. Your body has already soaked up all of the oxygen the red blood cells are carrying. Thats why its dark. Arterial blood is bright red of course because its pumped straight from your heart with all the oxygen. Your capillaries return your blood to your veins so its also a bright red. Venous blood is the primary sample type to run the majority of tests.
Capillary blood is used for quick tests like jaundice tests in babies or sugar tests for diabetics. I typically stop poking babies heels at around 4 to 5 months because the capillaries are to deep to reach. Then you end up squeezing the foot to hard and then hemolizing the sample. Thats bad. You’ll end up having to recollect the sample.
Arterial blood as mentioned before is used to measure your oxygen level mostly. Usually when you’ve had a heart attack and not pleasant at all.
Veins bleed less than arteries when you remove the needle, because the pressure is less in the veins. They are easier to see as well, the arteries in the arm can be felt but not well seen. Another thing people aren’t saying is risk. Doing arterial lines and ABGs have a risk of vasospasm, which is when the vessel “clamps down”, and can restrict blood flow. This is bad because arteries supply tissue with blood, and the tissue will die if it gets no blood, but that’s fairly rare. We do arterial lines in the wrist because there are other arteries that also supply blood to the hand, should vasospasm occur in the artery we are working on. The arm is just easiest, and least uncomfortable for people.
Follow up question:
Does anyone know why there’s sometimes a lot of pain after having an IV in for a while? And what it means for a vein to get “tired”?
I had an IV that was fine, then all of a sudden, it felt like they were pumping viscous mercury into my veins.
The nurse quickly realized what it was, and said something like veins get “tired” and switched it to my other arm.
What does that mean?
Arteries pulsate (as they arise directly from the beating heart and are hence, difficult to control bleeding from), are deeper, and are quite painful to get access to. Veins don’t have such features which is why they’re preferred for general access to your circulatory system
Exceptions to this include taking an ABG (arterial blood gas), procedures (like coronary artery stenting (opening arteries that are blocked in the heart)) etc
Arms are preferable due to easy access although the feet may be used as well for venous access
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