INTRAVENOUS OXYGEN

Pre-oxygenation – pffft!… Who needs that?! We’ve now got i.v. oxygen to save the patient from critical hypoxemia.

Dr. Kheir was involved in an incident with a critically ill 9 month old patient who sustained brain injury after prolonged hypoxemia. She was put on bypass, but it was too late to save her brain. After that, Kheir started dreaming of a syringe with intravenous oxygen they could’ve given her. And went to work on it.

They now seem to have a working prototype of a lipid emulsion that contains oxygen and can be injected into the blood stream, release the oxygen and thereby reoxygenate the blood. Their findings are published in Science Translational Medicine. A journal I don’t have access to, but the abstract sounds intriguing.

Intravenous Oxygen
Intravenous administration of oxygen was tried in the early 1900s, but these attempts failed to oxygenate the blood and often caused dangerous gas embolisms as free oxygen oxygen in blood spontaneously formed larger gas bubbles.

Dr Kheir and his Harvard Team has engineered around this problem by packaging the gas into small, deformable lipid particles. They also increase the surface area for gas exchange and are able to squeeze through capillaries where free gas bubbles would get stuck.

Mixing the solution with human blood in a lab glass immediately turned the dark blood bright red, and measurements showed the oxygen was available for gas exchange. They have also injected the solution into hypoxemic rabbits. Arterial saturation was near normal after a few seconds. And fell again when they stopped the infusion.

Current Limitations and Obstacles
There still seems to be a few problems. The solution carrying the oxygen isn’t too healthy for you in large quanteties. They have managed to concentrate a lot of oxygen into a small amount of liquid, but apparently you can only infuse this agent for 15-30 mins before you start to reach maximum safe levels.

And it might not be working as well as one would hope, just yet. Reading the abstract, the outcome of the next experiment was a little more worrying:

“The particles were also infused into rabbits undergoing 15 min of complete tracheal occlusion. The oxygen microparticles significantly decreased the degree of hypoxemia in these rabbits, and the incidence of cardiac arrest and organ injury was reduced compared to controls.”

Hypoxemia was significantly decreased? The incidence of cardiac arrrest was reduced? The incidence of cardiac arrest should be gone, if this really worked. So this doesn’t sound like the pocketable pre-drawn i.v. oxygen syringe I was hoping for. In any case, this is an exciting sic-fi innovation.

In a later iteration, it could save difficult intubation scenarios, can’t intubate can’t ventilate, or other forms of acute and critical airways, lung injuries or other events leading to severe hypoxemia. It would buy us time to intervene to establish an airway, or put the patient on ECMO.

Oxygen gas-filled microparticles provide intravenous oxygen delivery, Kheir et al, Sci Transl Med, 2012 June.

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