How do they get there? How do we get rid of them? And do we need to worry about them in the first place?

Perhaps you have been a patient in hospital and had a drip running. And perhaps you have looked down and noticed some tiny bubbles in the IV.
Somewhat alarmed you watch as they slowly float down the tubing and then disappear up into your arm.

You vaguely remember watching a TV drama where someone was killed in a hospital by the villain injecting air into their IV line.

“OMG!….Am I about to die?”

No. In most cases, it would require at least 50 mL of air to result in any significant risk to life. However, there are case studies in which 20 mLs or less of air rapidly injected into a patients circulation has resulted in a fatal air embolism (essentially a blockage caused by the air bubble).

So, you can be assured that it usually requires a very large volume of air in the IV to produce a life threatening risk of air embolism. Much more than you will typically see in your IV line.

Despite the tiny risk,  very small amounts of air, known as micro-bubbles have the potential to migrate through the chambers of the heart and lodge in the pulmonary vascular bed of the lungs. This is not usually a problem as they are readily absorbed, but if large numbers rapidly accumulate they may merge into larger emboli and present a greater risk. This is of particular concern in older patients and those with multiple medical problems.

So… do not be alarmed with those small air bubbles (which often appear mysteriously) in the line. And be assured that medical staff are always attempting to minimise the risk of them forming.

But what about when the bag is empty, can air run down the line then?
If your IV is on an electronic pump, it will automatically stop once the bag is empty. It also has bubble detectors that will stop the pump (and sound an annoying alarm) if any air bubbles are detected.

If your IV is not on a pump, the plastic IV bag collapses as it empties forming a vacuum inside that stops any further flow. You may notice that the drip chamber (that little plastic reservoir on the IV tubing just below the bag of fluids) may be empty and the level of fluid may have dropped just below it.

You should NEVER attempt to stop or alter your IV rate or change settings on the pump.
Instead, notify a nurse.
And as you can see there is really no need to obsessively watch your IV line.
But to improve your knowledge and help identify potential problems to staff, here are some of the preventable things that could lead to a more significant amount of air in your IV line.

Drip chamber not filled properly. This occurs when the nurse or doctor has not adequately primed the drip chamber. The drip chamber is usually marked with a fill line and if it is under filled it may increase the likelihood of air bubbles making their way into the IV line. Especially if it is running at faster rates or if the IV tubing is jiggling around (when you are being transported somewhere for example).

IV line not ‘primed’. Before connecting your IV staff will run fluid from your IV flask down through the tubing to prime it and remove all the air. If distracted or interrupted there is a risk that the tubing may not have been fully primed and it can be difficult to tell if the IV tubing is full of fluid or air on a quick glance. An un-primed IV line presents a potential for a more significant volume of air to be accidentally infused into the circulation.

Air is added to the IV bag when injecting additives. Medical staff should ensure that there is no extra air injected from the syringe into your IV bag when adding medications or electrolytes. Any extra air pressure may exceed atmospheric within the bag, forcing air down the IV line once the bag is empty (this will only happen if the IV is not connected to an IV pump).

The IV bag is placed on the bed. Air can enter the line from the IV bag if it is placed down on the bed (when, for example, transferring you from one bed to another).
The IV bag should always be hanging vertically.

OK. I see a bubble. Now what?

Nurses don’t worry too much about those individual tiny bubbles. But for larger ones (where it becomes more of a long ‘gap’ in the fluid than a bubble), or multiple bubbles, you should let a nurse know so they can remove them.

There are specific procedures they might use to do this including:

  • Disconnecting the IV tubing and flushing any air out of the line.
  • ‘Milking’ bubbles back up the tubing and into the drip chamber.
  • Removing air from the line with a syringe.

 


References:
1. Infusion-related air embolism. – PubMed – NCBI [Internet]. [cited 2015 Apr 12]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/23271149
2. Air Embolism. Risk Prevention in Infusion Therapy. [cited 2015 Apr 12]. Available from: http://www.safeinfusiontherapy.com/documents/french/air_embolism%281%29.pdf

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