What is Venous Gas Embolism?
Venous gas embolism is the condition when a gas bubble forms in the body’s veins. This bubble can disrupt the normal flow of blood, acting like a blockage. Most of the time, venous gas embolism happens as a result of medical procedures. It can occur during the process of inserting a tube into the central veins, during surgeries involving the head and neck, or as a result of injuries to the chest. It can also happen during procedures to remove fluid from the chest (thoracentesis), during kidney dialysis treatments, and during mechanical ventilation when the pressure is high. Additionally, this condition can occur during diving or when a special dye (radiocontrast) is injected into the body for CT scans.
While in most cases venous gas embolism is harmless and goes unnoticed, there may be cases where symptoms do appear. When this happens, immediate treatment is crucial as there is a risk of death if the problem is not addressed promptly.
What Causes Venous Gas Embolism?
Venous gas embolisms occur when air or gas gets into the veins. This usually happens during medical procedures. Some examples of procedures that might cause venous gas embolisms are when a special tube is inserted or removed from a central vein, CT scanning, kidney dialysis, chest injuries, lung biopsy, heart surgery, brain surgery, angioplasty, joint scope procedure, minimally invasive surgeries, and hysteroscopy among many others.
During any surgery where the patient’s head is raised or in a sitting position, there’s a risk of air embolism. This has been reported after ear, nose, and throat procedures and brain surgery. Women’s health and childbirth related procedures also have a potential to cause venous air embolism. The risk is highest during a cesarean section if the uterus is moved outside the body for the procedure. A central venous access procedure can also cause venous air embolism, especially if the needle isn’t properly covered, the tube gets disconnected, deep inhalation during the tube’s removal or insertion, the patient’s upright position during insertion, and low blood volume.
Another common cause of venous air embolism is during hysteroscopy, laparoscopy, or a procedure on the urethra where air is mechanically blown in. Positive pressure ventilation, a treatment to help patients breathe, can also increase the risk of venous gas embolism. Over-expansion and rupture of tiny air sacs in the lungs from excessive pressure can lead to air escaping.
In all these instances, the common factor is that air or gas can accidentally get into the veins. Deep-sea diving can also cause venous gas embolism. As a diver ascends, the pressure decreases, causing the nitrogen dissolved in the blood to form bubbles, which can block the veins. This can be prevented by ascending slowly and taking deep breaths to help expel the excess nitrogen.
Risk Factors and Frequency for Venous Gas Embolism
The rate of gas embolism, a medical condition where gas bubbles enter the bloodstream, has seen a steady increase over time. This is largely due to the rising number of invasive medical procedures performed. Furthermore, the use of advanced monitoring techniques, such as end-tidal carbon dioxide and Doppler monitoring, has improved our ability to detect gas emboli. However, it’s hard to gauge their actual incidence, as most venous gas emboli do not cause any noticeable symptoms and go under the radar. Neurosurgical procedures carry the highest risk of venous gas embolism for several reasons, including the upright position of the patient, the relative position of the brain and heart, and the unique characteristics of the brain’s venous system.
Signs and Symptoms of Venous Gas Embolism
Venous gas embolism is a medical condition that can be difficult to diagnose, as its symptoms are often similar to those of many other health issues. It is often suspected in those who have recently had surgical procedures or suffered trauma. Symptoms can include an unusually fast or unusually slow heart rate, low blood pressure, difficulty breathing, chest pain, and coughing. Other signs may be noticeable if the patient is being monitored, such as a decrease in end-tidal CO2, high carbon dioxide levels in the blood, and increased pressure in the pulmonary artery. In severe cases, the patient may also show signs of an altered mental state due to low blood pressure, pulmonary artery hypertension, and strain on the right side of the heart. It’s also important to know that though it’s not discussed here, arterial gas emboli can lead to serious conditions like stroke and heart attack.
The signs of venous air embolism related to heart function include:
- A ‘mill-wheel’ murmur, which sounds like loud machinery
- Abnormal heart rhythms that are either too fast or too slow
- Increased pressure in the neck veins
- Low blood pressure
- Signs of decreased blood supply to the heart
Symptoms associated with the lungs include:
- Rapid breathing
- Rales or wheezing
- Bluish skin color due to low oxygen
- Mild spitting up of blood
- Stoppage of breathing
Symptoms affecting the central nervous system can include:
- Changes in mental state
- Seizures
- Coma
- Temporary specific neurological deficits, such as weakness on one side
An eye examination may reveal air bubbles in the small blood vessels of the retina. In cases of massive air embolism, the skin may feel crackly to the touch due to air bubbles in the superficial veins. As there are no specific signs and symptoms, it requires a strong suspicion to diagnose this condition and start treatment.
Testing for Venous Gas Embolism
Diagnosing a venous gas embolism (which is a bubble of gas that is trapped in your blood vessels) largely depends on clinical signs and requires the doctor to be highly suspicious of it. If you suddenly experience symptoms such as loss of consciousness or instability of your vital signs during or after an invasive procedure, doctors would highly suspect the presence of a gas embolism. The timing between your symptoms and the invasive procedure is the biggest clue for the doctor to make a diagnosis.
In the operating room, various monitors may already be used and these can help detect venous gas embolism or arterial gas embolism, which is when the gas bubble gets into the blood vessels that supply your organs with blood. The results of a blood gas test may show high levels of carbon dioxide, low levels of oxygen, and metabolic acidosis, which means your body has an imbalance in its acid-base status.
Transesophageal echocardiography, which is a type of ultrasound test that uses sound waves to create detailed images of your heart, may visualize a gas bubble in your heart and is the most sensitive test for venous gas emboli. Precordial Doppler monitoring, which measures the speed and direction of blood flow in your vessels, is the most sensitive noninvasive test that is commonly used.
End-tidal carbon dioxide and nitrogen monitoring can be useful in detecting venous gas emboli that are stuck in the blood vessels in your lungs. Additionally, a decrease in the tidal volume or the amount of air that moves in and out of the lungs during normal breathing is more specific for venous gas embolism than for many other tests.
CT scans can detect small amounts of air in your central venous system, a part of the circulatory system that carries blood back to the heart. The technique may also reveal air within the brain or brain swelling. While end-tidal nitrogen, a measure of nitrogen in the breath, is a very sensitive way of detecting venous air embolism, its response is much faster than with end-tidal carbon dioxide measurements. However, this technique does not always identify very small amounts of air and may falsely indicate resolution.
If you have a central venous catheter, a tube inserted under your skin so the doctors can easily access your blood vessels, the doctors may try to suck out or “aspirate” air bubbles. Whenever venous air embolism is suspected, they must quickly stop the surgical procedure. Aspiration may occur when inserting a central venous catheter and ideally, the catheter should be placed just 2 cm below the junction of the right atrium and the SVC, where blood from the body returns to the heart.
Treatment Options for Venous Gas Embolism
Venous gas embolism, which is when gas bubbles enter and block your veins, can be quite a serious condition. The treatment usually revolves around helping your body cope with this condition. For instance, if you are inhaling gases like nitrous oxide, it’s important to stop since it could potentially worsen your condition. Instead, you could have 100% oxygen supplementation, which helps to rectify low oxygen in your blood (known as hypoxia), and it could also help to shrink the size of the gas bubble.
In extreme cases of venous gas embolism, performing a cardiac massage can be helpful. This is where a healthcare provider uses their hands to apply pressure and rhythmic movements to your heart area. This could help dislodge air out of the large blood vessels that lead out of the lungs and push them into smaller vessels, leading to improved blood circulation.
In some situations, where a vein catheter (a thin tube inserted into a vein) is already in place, it could be advanced to the heart to remove these gas bubbles. Positioning your body in a certain way, for example, laying on your left side, could make it easier to remove gas bubbles from the right side of your heart. However, this intervention should not be done just for the sake of removing gas emboli unless there is a real need for it.
If your heart function on the right side is compromised, medicines like dobutamine and ephedrine may be administered; these drugs have the effect of strengthening the heart’s pumping power, leading to improved circulation.
While the use of hyperbaric oxygen therapy (a treatment that involves breathing oxygen in a pressurized room to increase oxygen levels in your blood) is somewhat common for arterial gas embolism (when gas bubbles block your arteries), this treatment is not typically used in cases of venous gas embolism.
Some patients with small venous gas embolisms show minimal symptoms and may not need any treatment at all. Usually, these small bubbles eventually reach the lungs, get trapped, and gradually become less in size as the person breathes out. However, in cases where the patient’s health becomes significantly unstable, resorting to hyperbaric oxygen therapy might be considered. Yet, the efficacy of this therapy is still uncertain.
If a patient does not respond to CPR due to suspected air embolism after a chest injury, a thoracotomy, which is an opening of the chest wall, and the clamping of the blood vessels at the lungs’ root (the hilum) may be needed. This is a major operation with a lot of risks and low survival rates, so it should only be done by a specialist surgeon.
What else can Venous Gas Embolism be?
When a doctor is trying to diagnose a venous gas embolism, there are other conditions they might consider because they present with similar symptoms. These include:
- Heart failure
- Tension pneumothorax (collapsed lung)
- Septic shock (a severe infection that can cause low blood pressure)
- Ischemic stroke (a type of stroke caused by a blockage in a blood vessel)
What to expect with Venous Gas Embolism
Generally, most patients don’t experience complications if a small amount of air enters their veins. However, if air gets into the central nervous system (CNS, which includes the brain and spinal cord), the situation can become very serious. The patient’s mental status, any neurological deficits (problems with the nervous system), and their age are the three main factors that can impact their outcome.
There is always a risk of serious, life-threatening complications with venous air embolism (a condition where air bubbles get into the blood vessels). These complications are particularly serious if the air bubble becomes stuck in a blood vessel. Mortality rates (the percentage of people who die from a particular condition) between 30-80% have been reported in cases of venous air embolism following trauma to the chest.
Surgeons who perform procedures with the patient seated or partially seated (known as the Fowler position), or who inflate the body with carbon dioxide, need to be especially careful. This is because there continue to be cases of air embolism occurring under these conditions.
Preventing Venous Gas Embolism
The most effective way to manage air bubbles in the veins, also known as venous air embolism, is to prevent it from occurring at all. Here are some measures to prevent venous air embolism:
* It’s better not to make patients breathe too quickly, especially when they are sitting or standing upright. This can cause more air to get into the veins.
* Alter the posture during surgery by positioning the head lower than the legs. This increases pressure in the sinuses, which are cavities within the skull, and can help prevent the entrance of air.
* If a patient has a medical condition called patent foramen ovale, which is an opening in the heart that hasn’t closed as it should after birth, it’s preferable to avoid surgeries in a seated position.
* Try to minimize the amount of increased pressure used during mechanical ventilation, which is a method of helping patients breathe using a machine.
* It’s safer not to insert central lines (a tube placed into a large vein to administer medication or fluids) in patients with low blood volume.
* Always make sure that the connecting piece of the tubes or catheters is closed.
* Regularly check the connections to central lines to ensure they are secure.
* Advise the patient not to take a deep breath during the insertion of a central line, as this can lead to the entry of air into the vein.
