A venous air embolism occurs when air bubbles accidentally enter the bloodstream. These bubbles can disrupt normal blood flow. While medical procedures have safeguards, understanding the effects of air entering the venous system is valuable.
Understanding Air Embolism
An air embolism develops when gas bubbles obstruct blood vessels, impeding circulation. When air enters a vein, it travels to the right side of the heart. From there, air can move into the pulmonary arteries, which supply the lungs. This can elevate pressure within the right side of the heart, interfering with its ability to pump blood or hindering blood flow through the lungs.
How Air Can Enter a Vein
Air can enter a vein through various mechanisms, often during medical interventions. Common scenarios involve intravenous (IV) lines, such as during insertion, removal, or disconnection of central venous catheters, or during hemodialysis. Certain surgeries, particularly neurosurgery where the surgical site is elevated above the heart, can also create conditions for air entry. Laparoscopic surgeries, lung biopsies, and accidental trauma can also lead to air entering the venous system. Air enters when the pressure inside the vein is lower than atmospheric pressure, creating a favorable pressure gradient.
Recognizing the Signs
Symptoms of an air embolism vary depending on where air bubbles travel and which bodily systems are affected. Respiratory signs include sudden shortness of breath, rapid breathing, and coughing. A decrease in end-tidal carbon dioxide (a measurement of carbon dioxide in exhaled breath) may also be observed.
When the cardiovascular system is involved, individuals may experience chest pain, irregular heart rhythms, or a sudden drop in blood pressure. A characteristic churning sound, sometimes described as a “mill-wheel murmur,” may be heard over the heart. Neurological symptoms can manifest if air reaches the brain, leading to altered mental status, confusion, dizziness, visual changes, or seizures. Stroke-like symptoms, such as weakness or paralysis on one side of the body, can also occur. These symptoms can develop immediately or appear with some delay.
Factors Determining Severity
The outcome of an accidental air injection into a vein depends on the volume of air introduced, its entry speed, and the individual’s body position. Small amounts of air are absorbed by the body without noticeable symptoms. However, larger volumes, especially if rapid, significantly increase the potential for adverse effects.
A potentially harmful volume in adults ranges from 100 to 500 milliliters, with a rapid entry rate of 100 milliliters per second posing a higher risk. The closer the air entry point is to the heart, the smaller the volume required for serious consequences. Patient positioning can also influence the air’s path; for instance, an upright position might cause air to travel towards the brain, leading to neurological symptoms. The presence of a patent foramen ovale (PFO), a small opening between the heart’s upper chambers in some individuals, can allow air to bypass the lungs and enter the arterial system, increasing the risk of stroke or heart complications.
Immediate Steps and Medical Care
Immediate actions following suspected venous air embolism focus on preventing further air from entering the circulatory system. This involves promptly identifying and closing off the source, such as clamping an IV line. Positioning the patient is a primary initial step. Placing the individual in a left lateral decubitus position with the head lowered (Durant’s maneuver) can help trap air bubbles in the right ventricle, preventing them from moving into the pulmonary artery or crossing into the arterial system.
Administering 100% oxygen is also important, as it helps reduce the size of air bubbles and improves oxygen delivery to tissues. Medical professionals provide supportive care, including managing blood pressure with intravenous fluids and vasopressors, and addressing respiratory difficulties. If a central venous catheter is in place, medical staff may attempt to aspirate air directly from the right atrium.
For more serious cases, especially those involving neurological symptoms, hyperbaric oxygen therapy (HBOT) is a specialized treatment. This therapy involves the patient breathing 100% oxygen in a pressurized chamber, which causes air bubbles to shrink and dissolve back into the bloodstream, accelerating their removal. HBOT is most effective when initiated promptly.