Quote from csns
ok, the question that bothers me the most is what do you do if you get caught up and can't get to your iv in time where the bag runs out and there is air in the tubing? what do you do? you can't hang the new bag with the air in there so what? i read some people said they backflush but what is that? thank you so much for your help!!!
hi, csns. . .here's the answer to your question. to backflush an iv in the situation you describe above you would take the iv bag and lower it below the patient's heart and iv site. what that does is create a negative gravity so that the iv fluid begins to back up the iv tubing. this occurs because the blood pressure in the vein is now greater than the pressure of gravity exerted by the iv fluid since the iv bag is below the level of the patient's heart. you allow the fluid to continue backing up, or backflushing, until it backs up to the drip chamber. when the fluid reaches the drip chamber you can raise the iv bag to it's original position and hang it back on the iv pole. however, if you look down at the patient's iv site and the tubing down near the iv site, you are going to see blood in the tubing. that is the backflow of blood from the vein that pushed that iv fluid back up your iv line. in order to make sure your iv line is going to stay patent you've got to get that blood flushed out of the line and cleared out. one way to do that is to open up the roller clamp on the iv fluid and let it flow wide open. sometimes you can't do that because of the solution in the bag or the patient's condition. another way to get the blood out of an iv line is to just load up a 20cc or 60cc syringe with ns and push it into the iv tubing at the first y-port above the bloody mess. or, third, just change the tubing.
another very easy way to remove air from an iv line when an iv bag has run dry is to do this which is much safer and aseptic. clamp off the iv tubing. hang the new iv bag. squeeze the drip chamber and fill it with some of the iv fluid. find a y-port that is below the air in the line. pinch off the iv line below this y-port. cleanse the y-port covering. insert a needle into the y-port and aim the hub of the needle at a wastebasket. open the roller clamp on the iv tubing. the atmospheric pressure will suck out whatever is above the y-port--that will be the air in the line and new iv fluid from the new iv bag which is why you need somewhere to aim what's going to shoot out of the hub of the needle because it's going to come out fast! when all the air is out of the line, close the roller clamp. remove the needle and discard it in a sharps container. unpinch your iv tubing. reset your iv rate. to be on the safe side i would flush the iv with 10 or 20cc of ns to assure it's patency.
to backflush air out of piggyback tubing, you merely open the roller clamp on the piggyback tubing and lower the little piggyback bag below the main iv bag. gravity wins out and iv fluid will automatically flow back, or backflush, up into the piggyback tubing. the fluid comes from the main iv bag which is able to bypass the rate restriction of the iv pump and detour right into the piggyback tubing. just let this fluid backflush until all the air is pushed back up and into the drip chamber. close off the roller clamp when it's pushed all the air up and out. you can then hang your next piggyback without any air in the line. this is the true backflush procedure and probably the one most people refer to. the procedures i described above are really done in an emergency to save the iv line.
the physics of this: one of the concepts that you need to know here is that the purpose of the drip chamber is to prevent air from getting in the iv tubing. if the iv bag accidentally goes empty and air does start to proceed down into the tubing there is a certain point at which the pressure of the iv fluid equalizes with the pressure exerted by the blood pressure in the vein that the iv device is in. the chance of air actually entering a peripheral vein through an iv cannula is very unlikely. what usually happens is at the point of pressure equalization, blood starts backing up into the tubing because it is exerting a greater pressure on the iv line than the iv fluid. eventually it can push no more. every thing in the iv stops. left unnoticed, the blood in the iv line and iv cannula sit there and clot up. the result, an iv that needs to be re-started unless you have someone who knows how to remove a clot from an iv cannula and the iv tubing is changed.
now, if the iv is in a central line, you've got problems if a bag runs dry and more than a couple of cc's of air run into the vein. i was trying to find a recent thread about this, but the search function hasn't been working properly since the software changeover. any iv on a central line should be on an iv pump to begin with. an iv pump has an air detector in it, so that air should never get into the patient's central circulation. because of the negative pressure pull due to the termination of the central line in the vena cava of the heart, air and fluid will be sucked into a central line that is accidentally left open to the atmosphere. this is why changing iv tubing on a central line needs to be done with care and you want the patient to take a breath and hold it for a couple of seconds or perform a valsalva maneuver while you do the actual change over. the danger of air being sucked into a central line is air embolism. it takes well over a couple of cc's of air pulled into the central circulation for an air embolism to occur.