Debunking myths: how much air in an IV line is too much?

Is it true that ‘a little air in an intravenous line won't cause harm’? The second article in our series looks at the evidence and provides advice

As nurses we are vigilant to remove air bubbles from patients’ intravenous (IV) lines, yet we have probably also all heard that ‘a little air won’t cause harm’. Is this true or is it a myth?

How much air in an IV line is okay and how much could potentially cause harm? This article will debunk the myth and help you practise with confidence.

This question is not one that can be answered easily. To say it would be unethical to inject air into people and see how much was required to cause harm is an understatement. Initial studies that sought to answer how much air was unsafe used animals – which still raises ethical concerns – and these studies often produced widely varying results (Adornato et al 1978, Ohkuda et al 1981).

Study showed a small air embolism was visible in 4.8% of patients

A venous air embolism occurs when air enters a venous structure and moves through the heart to the pulmonary circulation (Gordy and Rowell 2013). The increase in pressure in the circulatory system from an air embolism can cause pulmonary hypertension and death (McCarthy et al 2016).

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It is recognised that air embolisms due to IV infusions or cannulation are rare, although they do occur (Vinan-Vega et al 2019), and there are cases in paediatrics where air embolisms from IV cannulas have proved fatal (Wald et al 2003, Agarwal et al 2009, Watkins et al  2012).

A study that sought to identify how frequently the insertion of IV cannulas was associated with air embolisms discovered that a small air embolism was visible in 4.8% of patients, though these air embolisms were not identified to be harmful (Groell et al 1997).

What size of air bubble constitutes a risk?

How much air is okay? It seems no one is sure. Tiny volumes of air, under 0.2mL, have been proved not to be hazardous (Blomley et al 2001), while IV administration of 300-500mL of air at a speed of 100mL/min is considered to be fatal in adults (Yesilaras et al 2014).

Ho (1999) suggests that 0.5-1mL of air in the pulmonary vein of an adult can cause cardiac arrest, which leaves uncertainty about the effect a smaller bubble could have in a neonate. The size of the air bubble that constitutes a risk is proportionate to the diameter of the vessel it occludes, therefore the smaller the child, the smaller the bubble that could cause harm.

Use of IV infusion pumps does not negate need for nursing recognition and action

What should we do? As children’s nurses what can we say with confidence?

The ideal management of IV lines is to remove all air from the IV giving set. National Institute for Health and Care Excellence (2013) guidelines state that staff must be competent in the preparation and administration of IV fluids. The use of IV infusion pumps to recognise air bubbles and filters to remove air from lines can be useful, but does not negate the need for nursing recognition and action.

• RELATED: Debunking myths: can you over-oxygenate a child?

We should be alert as well to the signs and symptoms of a possible air embolism if air were to get into an IV line. These are: anxiety, shortness of breath and/or increased respiratory rate, chest pain, cyanosis, tachycardia, headache, confusion, agitation, fainting, slurred speech, blurred vision, seizures or ataxia (Yesilaras et al 2014, Vinan-Vega et al 2019).

Leah Rosengarten is a lecturer at Northumbria University, Newcastle upon Tyne, England

This article has been subject to open peer review and has been checked for plagiarism using automated software

References

• Adornato DC, Gildenberg PL, Ferrario CM et al (1978) Pathophysiology of intravenous air embolism in dogs.  Anesthesiology. 49, 2, 120-127. doi: 10.1097/00000542-197808000-00013
• Agarwal SS, Kumar L, Chavali KH et al (2009) Fatal venous air embolism following intravenous infusion. Journal of Forensic Sciences. 54, 3, 682-684. doi: 10.1111/j.1556-4029.2009.01004.x
• Blomley MJK, Cooke JC, Unger EC et al (2001) Microbubble contrast agents: a new era in ultrasound.  British Medical Journal. 322, 7296, 1222–1225. doi: 10.1136/bmj.322.7296.1222
• Gordy S, Rowell S (2013) Vascular air embolism. International Journal of Critical Illness and Injury Science. 3, 1, 73-76. doi: 10.4103/2229-5151.109428
• Groell R, Schaffler GJ, Rienmueller R (1997) The peripheral intravenous cannula: a cause of venous air embolism. The American Journal of the Medical Sciences. 314, 5, 300-302. doi: 10.1097/00000441-199711000-00006
• Ho AM-H (1999) Is emergency thoracotomy always the most appropriate immediate intervention for systemic air embolism after lung trauma? Chest. 116, 1, 234-237. doi: 10.1378/chest.116.1.234
• McCarthy CJ, Behravesh S, Naidu SG et al (2016) Air embolism: practical tips for prevention and treatment. Journal of Clinical Medicine. 5, 11, 93. doi: 10.3390/jcm5110093
• National Institute for Health and Care Excellence (2013) Intravenous Fluid Therapy. Intravenous Fluid Therapy in Adults in Hospital
• Ohkuda K, Nakahara K, Binder A et al (1981) Venous air emboli in sheep: reversible increase in lung microvascular permeability. Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology. 51, 4, 887-894. doi.org/10.1152/jappl.1981.51.4.887
• Vinan-Vega MN, Rahman MR, Thompson J et al (2019) Air embolism following peripheral intravenous access. Baylor University Medical Center. Proceedings. 32, 3, 433-434 doi.org/10.1080/08998280.2019.1609154
• Wald M, Kirchner L, Lawrenz K et al (2003) Fatal air embolism in an extremely low birth weight infant: can it be caused by intravenous injections during resuscitation? Intensive Care Medicine. 29, 4, 630-633. doi: 10.1007/s00134-003-1681-7
• Watkins SC, McCarver L, VanBebber A (2012) Venous air embolism leading to cardiac arrest in an infant with cyanotic congenital heart disease. Case Reports in Anesthesiology. doi.org/10.1155/2012/208430
• Yesilaras M, Atilla OD, Aksay E et al (2014) Retrograde cerebral embolism. The American Journal of Emergency Medicine. 32, 12, 1562. doi: 10.1016/j.ajem.2014.05.043