RN here. There are two main types of IV lines. Peripheral IVs and central lines. Peripheral IVs are typically inserted into a small vein of the arm or hand and have a tiny diameter. This is what most people think of as an IV. Central lines (google PICC ) have a much larger diameter and are inserted in larger veins and terminate in one of the body's large vessels -e.g Superior Vena Cava very close to the heart. The real danger of air in the circulatory system is that if a bubble is large enough and makes it to the brain it can cause a blockage called an embolism in one of the smaller vessels supplying blood to the brain. This would essentially cause a stroke. A small amount of air passing (<10ml-about the size of a test tube from HS chemistry) passing through a peripheral IV just simply can't form a large enough bubble to pose a danger. In fact it has been estimated that you would need as much as 100ml of air pushed through a peripheral IV to do harm. Those tiny bubbles just get dissolved in your blood very quickly. A central line however is a much different situation. Because they have a much larger diameter and are placed in larger vessels with larger volumes of blood then it doesn't take much air for a large bubble to form. A few tiny bubbles of air that you would typically see in IV tubing is not likely to do any harm but as little as 2-3ml air pushed in all at once with a medication for instance could easily be dangerous in a central line. That's why nurses trained to clear all the air from syringes used for central lines. It all about how big of bubble can form in your blood. So if you have peripheral IV in your arm or hand and you see a few bubbles in your IV tubing don't let it concern you it's just not enough to hurt you.
The most feared complication of an 'air embolus' (in that you could die immediately) requires enough air to obstruct the outflow tract of the right ventricle. Basically causes an air ball-valve effect that prevents any blood from leaving the right side of the heart. Smaller amounts of air that are introduced into your veins will simply be absorbed as they move through pulmonary capillaries in the lung and not cause you any issue. In regards to how much, most traditional studies show that 200cc should be fatal. Recently case reports have suggested somewhere between 50-100cc could be as well, but I can't find any precisely agreed upon amount.
The other potential complications can occur only if there is some way that air can travel from the right side of your heart to the left, without passing through the lungs. Most commonly, this would be through a patent foramen ovale, or PFO, that allows blood to be shunted without passage through the lungs. There are other possibilities but require some kind of 'abnormal' communication. In that scenario, an air embolism could cause a myocardial infarction or stroke due to obstruction of an artery as mentioned as it was able to cross from venous to systemic circulation without being 'filtered' through the lungs.
So, in practice, we use filters or aspiration of fluid and blood to clear IV lines to try and prevent it, but small amounts of air should not cause any detriment as you noticed.
I read IV as Roman numerals and only came here for clarification on why it was ok for 4 drips to have air bubbles running through their lines. I had completly had 100% no idea what was going on.
Air is only of major concern in arterial lines. True, don't inject more than 30 ml or so in a venous line, but air in the arterial system can be very dangerous with just tiny bubbles.
Doctor here, at medical school we were taught that anything over 10ccs of air given IV can be lethal, as an air embolus that size can cause cardiopulmonary arrest. All veins are, practically speaking, a non stop highway to the heart, and it is unlikely the air would pass through the heart, and certainly would go no further than the capillary bed of the lungs, which would be the next port of call. 10ccs of air would fill a roughly 90-100cm length of UK IV giving set tubing. Smaller bubbles are usually harmless as they can dissolve into the blood and other tissues without causing any havoc. In fact, tiny bubbles are deliberately injected IV during 'bubble study' echocardiograms which are used to detect holes in the heart.
There's a difference between a rapid infusion of a large volume of air and a slow infusion of a small volume of air. For the most part, our bodies can deal with small amounts of small volumes (a small number of small bubbles), but the danger comes when you introduce a large volume of air quickly into the circulatory system. In popular culture the bad guy injects a large volume of air into a victim's neck quickly, causing death due to an embolism.
Pump fed IV-lines have built in bubble detectors to make sure that they're not a threat to the patient, but gravity fed lines can be more of a problem if proper precautions are not met and most medical professionals have the proper training to reduce the incidence of harmful bubbles in IV-lines.
Your IV drip may be required to have a [little dime-shaped thing](https://shop.pall.com/us/en/medical/infusion-therapy/iv-fluids/supor-aef-intravenous-filter-set-zidgri78m2i#attr_description) somewhere along it, which passively separates and expels the air from the drip. It's pretty cool.
I was in the hospital for a knee surgery a while back, and they kept me overnight. During one of my IV changes, I saw a pretty large air bubble (maybe 20 inches of line) go into my hand. I asked the nurse about it, and she was most of the way through telling me that it was nothing when my heart felt like it was jumping out of my chest. The heart monitor I was hooked up to started alarming. She looked worried. I was worried. Then it passed.
Someone else came by (guessing a head nurse?), and asked me about what happened. I said I saw some air in my IV, which she said was normal, but didn't seem pleased when I mentioned how much there was. I had a different nurse for the rest of my stay.
1) you need a lot of air to cause any big issues.
2) if you're using a pump it'll alarm like a banshee at the slightest bubble, often when a bag has run empty you'll see a bunch of air in it cause it's above the pump and no longer flowing. This is the same with gravity fed, there is no pressure so the air doesn't get pushed in.
3) if you've hung and primed the tube like a noob, it's often easiest to let the bag empty for a bit till the air moves down, the you lock the port near the wrist and use a syringe to suck the air out. This way you don't waste whatever you're giving your patient, however this method requires you to watch the air move down.
4) Cause the tubes are so thin it looks likes like a lot of air when it's actually only a little bit