Emergency HBOT Indications: Gas Embolism, Severe Anemia, Retinal Artery Occlusion, Intracranial Abscess

Each of these conditions is on the Undersea and Hyperbaric Medical Society (UHMS) indications list. Three of them (gas embolism, severe anemia and intracranial abscess) are also on the FDA's list of cleared uses for hyperbaric chambers; central retinal artery occlusion is recognized by the UHMS but is not on that FDA list. They also share three things:

• They are diagnosed in hospital, often in an emergency department or intensive care unit.
• When HBOT is used, it is given in hospital chambers with critical-care support, alongside other urgent treatment.
• None of them is managed as a scheduled outpatient course.

Other emergencies on the list have their own pages: decompression sickness, carbon monoxide poisoning, crush injury, necrotizing soft tissue infections and thermal burns. For the full picture, see the conditions HBOT is cleared for.

When it is used

Normally, severe blood loss is treated with a blood transfusion. HBOT is considered only in rare situations where transfusion is not possible: compatible blood cannot be found, or the patient declines blood products, for example for religious reasons, as many Jehovah's Witnesses do. It is used when the patient shows signs that organs are not getting enough oxygen despite fluids and other care.

Here is how it works. Almost all the oxygen in blood is carried by red blood cells. When too many red cells are lost, the body cannot deliver enough oxygen. Under pressure, oxygen dissolves directly into the liquid part of the blood (plasma). At about 2.5 to 3.0 ATA, enough oxygen can dissolve in plasma to help meet the body's basic needs for a period of time. For more on this, see how dissolved plasma oxygen works.

HBOT does not make new red blood cells. It buys time while the body rebuilds its blood supply, supported by treatments such as iron and medicines that stimulate red cell production. It is a bridge, not a substitute for blood.

What the evidence shows

The evidence comes from physiology studies and case reports or case series; randomized trials are not practical in this situation. Sessions are often repeated several times a day at first and tapered over days as blood counts recover. Because patients may need a lot of oxygen time, hospital teams monitor closely for oxygen toxicity, which can affect the lungs and, rarely, cause seizures. Exceptional blood-loss anemia is on Medicare's non-covered list for HBOT, although it remains an FDA-cleared and UHMS-listed indication.

What it is

An intracranial abscess is a pocket of infection inside the skull, in or around the brain. Symptoms can include severe headache, fever, confusion, seizures, weakness on one side, and vomiting. Treatment is urgent: surgical drainage when possible, and weeks of IV antibiotics.

When HBOT is considered

UHMS lists HBOT as an adjunct to surgery and antibiotics, not a replacement, in selected situations, such as:

• Multiple abscesses
• An abscess deep in the brain or in a critical area
• A patient with a weakened immune system
• A patient who is not a good candidate for surgery
• An abscess that is not responding to standard treatment

The rationale is similar to other severe infections: higher oxygen levels may help white blood cells fight bacteria, act against bacteria that thrive without oxygen, and reduce brain swelling.

What the evidence shows

The evidence is limited to case series and reviews, including a 2021 review in Undersea and Hyperbaric Medicine. These report good outcomes in selected patients, but without comparison groups it is hard to know how much HBOT itself contributed. The decision rests with the neurosurgery, infectious disease and hyperbaric teams.

Generations Wellness is a physician-directed outpatient center under Dr. Rajwinder Singh Bahia, MD. We do not provide emergency hyperbaric treatment, and we do not treat any of these four conditions. They require hospital diagnosis and, where indicated, hospital chambers.

Follow-up after these emergencies is led by the hospital team and specialists: a neurologist after gas embolism or brain abscess, a hematologist or primary care doctor after severe anemia, and an ophthalmologist and stroke team after CRAO.

Once you are stable and home, our team is glad to talk with you. We can answer general questions about hyperbaric oxygen therapy and tell you honestly whether anything we offer is relevant, including whether a separate cleared indication such as a non-healing wound might apply. Clinicians can find information for referring physicians.