Air embolisms are rare, but potentially lethal, complications of certain medical and surgical procedures that occur every day within health care organizations. Air Embolisms are considered preventable hospital-acquired conditions that often result in serious patient harm. The Centers for Medicare and Medicaid Services classify an Air Embolism as a “never event”; as such, an air embolism receives a nonpayment for harm from the Centers for Medicare and Medicaid Services ^1,3.

Outside of a very strict set of natural circumstances (rapid ascent while scuba diving, severe chest trauma, and orogenital sex during pregnancy) air embolisms primarily occur during medical or surgical procedures^{1, 2, 6}. Air can enter the human vascular system through a number of ways:

• Air often enters the vascular system during surgical procedures. Surgeries associated with neurosurgical, vascular, obstetric, gynecological, or certain orthopedic procedures have a particularly high risk of air embolism ².
• Air can enter the vascular system due to the incorrect execution of pressure infusion procedures ⁴.
• An Improperly filled and completely vented infusion line can be a source of air entry ^{4, 5}.
• Parallel infusions – situations where gravity infusions and infusion pumps are attached together and interact through the infusion lines. When the gravity infusion runs dry, these systems can develop a beading (fluid-air-fluid) pattern and become particularly dangerous ².
• Open IV access and infusion systems can become sources of air entry. In this situation, the amount of air entry is determined by the position of the patient and the height of the vein in relation to the right side of the heart.
• In short, no vascular procedure is exempt from the risk of air embolism. Air embolisms have been identified in relation to nearly all forms of vascular procedures and devices ⁵.

The severity of an air embolism depends on the volume of air that enters the vessel, the rate at which the air enters the vessel, and the patient’s body position at the moment of entry ^{3, 5}. In order for an air embolism to occur, there must be a direct line of access to the blood vessel and there must be a pressure gradient between the vascular space and atmospheric air⁵. Pressure gradients are generally classified as either passive or active:

• Passive – This occurs when the access point to the blood vessel is above the level of the heart. This creates a situation for passive entry ^{2, 4} .
• Active – This occurs when devices are improperly utilized. Syringes that have not been completely purged of air or intravenous tubing that was improperly primed are two examples of active entry ⁴.

The human body can tolerate small amounts of air introduced into the peripheral venous system at slow rates, often without symptoms ³. Although the exact maximum amount of air able to be tolerated is not known, and is most likely different from person to person, amounts greater than 20ml have proven fatal ^{2, 5}. The peripheral venous system is able to tolerate slow rates of air introduction, often without symptom. Larger volumes and rapid infusions of air cause the pulmonary artery pressure to rise which in turn places strain on the right side of the heart ⁵. This can then create an airlock in one or more of the pulmonary arteries, obstructing the circulation and causing circulatory collapse ^{3, 5}. The closer to the heart the air embolism is introduced, the smaller the volume of air is required to be symptomatic ⁵. Even small air embolisms can cause tissue ischemia or inflammatory changes within blood vessels, leading to a host of lethal complications.

A bolus influx of air is the most typical form of air entry into the vascular system ². This can happen either passively or actively, however passive entry is the most common scenario. The symptoms of a bolus air embolism include:

• Sudden dyspnea ⁹
• Lightheadedness
• Shoulder and chest pain ⁶
• Nausea

Arterial air embolisms, on the other hand, are very poorly tolerated by the human body. Even a small amount of air can be lethal. The danger is multiplied if the patient has a patent foramen ovale (an opening between the left and right atria – an estimated 1 in 5 Americans have a PFO) because a pathway then exists by which the venous air embolism can pass into the arterial circulation and enter the brain (causing stroke) or the coronary circulation (causing a myocardial infarction) ^{2, 5, 9} .

Diagnosing an air embolism can be difficult and is rarely straightforward. Air emboli symptoms are often similar to a wide range of other varying diseases. Symptoms can be as diverse as lightheadedness, shoulder and chest pain, tachypnea, tachycardia, and hypotension ⁵. Transthoracic echocardiography and precordial ultrasonography have been proven to be effective at diagnosing air embolisms and enabling proper interventions ². However, these devices are normally only used during surgical or invasive procedures where there is a heightened risk of air embolism.

If an air emboli is suspected, treatment must begin rapidly in order to prevent patient harm. Treatment options include:

• Place the patient in the Trendelenburg position (on their left side with their head flat). This will help decrease the gradient between atmospheric air and the vasculature. Laying on the left side helps hold any entrapped air in the apex of the right atrium to prevent occlusion of the pulmonary artery ⁷.
  • This position can be contraindicated in patients with increased intracranial pressure, cerebral oedema, increased intraocular pressure, and ischaemia of the lower limbs ².
  • Fowlers and semi-fowlers can be other options if the Trendelenburg is contraindicated.
• Close or cover the entryway of passive air.
• Administer Oxygen at 100%. This helps to reduce the size of an air bubble ⁵.
• If possible, attempt to aspirate air from the catheter ³.
• Monitor vital signs and immediately notify the physician.

Air embolisms have been associated with a wide range of clinical procedures such as: high-pressure mechanical ventilation, seated neurological procedures, thoracocentesis, and Central Venous Catheterization. Of the wide variety of procedures, air embolisms most commonly are reported during central venous catheterization. It is estimated that venous air embolism with central venous catheters occurs from a range of 1 in 47 patients to 1 in 3,000 patients ⁶. Two key factors remain the most commonly documented errors resulting in Air Emboli during or after the removal of a central line:

• Failure to place the patient in a supine or Trendelenburg position during removal ².
• Failure to provide an occlusive dressing over the site ⁵.

It is believed that because the actual recognized incidence of Air Embolisms is low, the basic safety protocols are routinely overlooked in hospitals across the nation ⁵. Here are several evidence based tips for the insertion, maintenance, and removal of a central line:

• Catheter Insertion and Removal:
  • Supine or Trendelenburg position – as long as not contraindicated by patient specific considerations ⁵.
  • Patient may hold breath or perform Valsalva’s maneuver during catheter insertion.
  • Ensure that a petroleum based gauze or gel is placed over the insertion immediately after removal in order to ensure that the dressing is air occlusive.
    • Keep this equipment at the bedside in the event of an unanticipated event.
  • An air occlusive dressing should be maintained until the epithelialization ⁵.
• Catheter Use and Maintenance
  • Do not leave tubing attached to a fluid but unprimed at the bedside if it is intended to be connected ².
  • Whenever connecting subsequent fluid bags to the IV Tubing, ensure that all air is purged from the primary or secondary tubing.
  • Prior to puncturing any fluid bag, ensure that an appropriate clamp is closed.
  • Vented tubing or alternative forms of venting with collapsible fluid should be avoided. These are at particular risk for air entry.
  • Luer-Lock connections can be used to reduce accidental disconnection of IV tubing. During phlebotomy evacuated containers should be avoided ².
  • Always be sure to examine all equipment for cracks or leaks that could let air in. Cracks on the catheter hub are a particularly common entry point.

Air embolisms have been documented since the mid 1800’s and are a constant threat to patient safety. Although their reported occurrences are rare, it is crucial for nursing leaders to consider the potential for air emboli while working with potentially at risk patients.

(1) Air Embolism (Arterial Gas Embolism). (2006). National Association of Rescue Divers. Retrieved June 23, 2014, from http://www.rescuediver.org/med/age.htm

(2) Cook, Lynda. (2013). Infusion Related Air Embolism. Journal of Infusion Nursing. January-February Volume 36 Number 1 Pages 26-36.

(3) Feil, Michelle. (2012). “Reducing Risk of Air Embolism Associated With Central Venous Access Devices”. Pennsylvania Patient Safety Advisory. June; 9(2): 58-64

(4) Infusion Nurses Society (INS). (2011). Infusion nursing standards of practice. Hagerstown (MD): INS; 2011.

(5) Joint Commission Resources (JCR). (2010). Clinical care improvement strategies: preventing air embolism. Oak Brook (IL): JCR; Jul.

(6) Kivi, Rose and Rudd, Peter. (2012). “Air Embolism”. Health Line. Retrieved From: http://www.healthline.com/health/air-embolism#Overview%201

(7) “Preventative Strategies – Air Embolism” (2014). B.Braun Melsungen AG. Retrieved from: http://www.safeinfusiontherapy.com/cps/rde/xchg/hc-safeinfusion-en- int/hs.xsl/7725.html

(8) Rosenthal K. (2008). Targeting “never events.” Nursing Management. Dec; 39 (12):35-8.

(9) Shaikh, Nissar and Ummunisa, Firdous. (2009). Acute Management of Vascular Air Embolism. Journal of Emergencies, Trauma and Shock. September – December; 2(3): 180-185. doi: 10.4103/0974-2700.55330