How do our veins handle extra liquid from shots or IV


I was in surgery earlier and remember when the nurse put injected anesthesia and something else through the IV and I could feel the liquid push itself into my vein and it felt like my vein in my hand to elbow would explode.

That got me thinking, how does my body intake so much liquid like the full IV bag without exploding or peeing on the operating table while I’m knocked out.

In: Biology

Veins aren’t rigid like home plumbing. They are somewhat elastic. Veins expand and contract for many reasons; Cary nutrients, fats, oxygen, and can expand and distribute vaccines and other liquids as necessary.

General answer. I’m at sure others can be more specific and technical.

Veins and arteries pump liquid through your veins really quickly. It is constantly moving. So, extra fluid in the veins from an IV is no different from drinking a huge amount of liquid for it to also be absorbed. Once the nutrients go where they need to go, the kidneys filter out the excess. And you would absolutely urinate on the operating table, but you most likely had a catheter in that was inserted and removed while you were knocked out.

The sensation of feeling the injection into your veins isn’t really about volume, but more that what was injected was an irritant. That’s why it is diluted with neutral IV fluids from the full bag.

Veins can expand, your kidneys can increase the rate of urine production, and yes, you would pee during surgery. That’s why they insert a catheter into you.

vessels are elastic to a point, if they shove too much in the wrong one you can cause a blowout. You’ll occasionally see people with massive “bruises” from this happening, or from the nurse putting the needle all the way through the vein. With small ones it’s not the end of the world but still definitely not ideal.

As for the “full bag” part your body absorbs the liquids as they go through your system, so it’s just a matter of not delivering liquid faster than your body can do something with it, it’s not a closed system like oil in your car, it’s constantly depositing material and picking up new things to move around.

That’s really simplified but it’s the gist.

I’ve had fluid replacement in hospitals, and first hand found out what happens to any excess.

Being severely dehydrated, I couldn’t urinate. 5 minutes after IV fluid replacement, that wasn’t a problem anymore. Kidneys work pretty fast getting rid of excess.