Thursday, July 12, 2012

Injectable Oxygen. A Potential New Anesthesia Paradigm

Most medical research attempt to show incremental improvements to already proven treatments. But a team out of Boston Children's Hospital is working on a project that I believe will truly revolutionize anesthesia, and medicine in general: injectable oxygen. John Kheir, MD, et al, have been studying ways to bypass the lungs' oxygenation function and give the oxygen directly into the bloodstream ever since he and his colleagues had the misfortune to watch a pediatric patient die from severe respiratory distress and hypoxia in 2006.

Attempts at oxygenating blood directly have been tried for a century. Unfortunately the early experiments met with failure when patients developed air embolism instead. Later, machines such as the cardiopulmonary bypass machine and ECMO were invented that simulated lung function outside the body. While the machines are generally successful, they also carry high risk complications. First of all, they are highly invasive, requiring tricky cannulations of central vessels with large tubing. The machines are also bulky, tethering the patient in place with no possibility of mobility. Then there are all the complications associated with these devices. Patients have suffered air embolism, thrombotic embolism, bleeding catastrophes, and strokes when placed on these machines.

Dr. Kheir and his team changed the whole concept of oxygenating the blood by not trying to simulate the lungs. They used a machine called a sonicator that emits sound waves to mix together oxygen and lipids. The resultant emulsion carries three to four times the amount of oxygen that is carried by our own red blood cells. The lipid-O2 particles can be safely injected into the bloodstream without causing an embolism. They tested their creation on rabbit models which had their trachea occluded for up to 15 minutes. After injecting the rabbits with the emulsion, the rabbits' hypoxia immediately improved. Dr. Kheir states that currently only small amounts of the emulsion can be given. It cannot be infused over a prolonged period of time as the patient would likely get fluid overloaded receiving that much volume to maintain oxygenation. He envisions keeping small syringes of the emulsion in a crash cart for emergency situations.

I say he is being too modest. While the research team claims that the amount of emulsion that needs to be infused is currently too large to support more than a few minutes of oxygenation, I have confidence that they will refine and improve their technique to incorporate larger amounts of oxygen into their system. Once that happens, the product could truly change the practice of anesthesia. Imagine the potential of bypassing the lungs during an operation. Anything involving the use of the cardiopulmonary bypass machine would immediately become obsolete. Performing a double lung transplant would be a snap. Lung resections and pneumonectomies would no longer require the intricate placement of double lumen endotracheal tubes. We won't have to rush patients to the operating room for emergency tracheostomies because of foreign body or tumor occlusions of the airway. ENT can perform their laser surgeries in the oropharynx with little fear of causing an operating room fire because no oxygen will need to be blown into the lungs. Intubated ICU patients will suffer less barotrauma if they can give their lungs a rest for even a few hours a day. The possibilites are truly astounding.

The use of this oxygenated lipid reaches beyond the hospital walls. Firefighters would carry oxygenated lipids into a fire instead of pressurized oxygen. They can inject flame victims with the stuff to get them safely out of an inferno. Near drowning victims can be injected with oxygen instead of receiving the less efficient mouth to mouth or bag-mask resuscitation. The list goes on and on. I wish the Boston team the best of luck on improving their wondrous work.

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