Perfluorocarbons (PFCs) are chemically inert molecules containing primarily, as the name suggests, fluorine and carbon atoms. They are capable of dissolving large amounts of many gases, including oxygen. PFC particles are about 40 times smaller than the diameter of a red blood cell, which enables them to go through capillaries where no RBCs are flowing. In theory, this can benefit damaged, blood-starved tissue that conventional red cells cannot reach. In addition to hypovolemia, this may be beneficial for MI, CVA and sickle-cell crises, among other similar obstructive ischemic conditions.
Perfluorochemical solutions carry oxygen so well that mammals and humans can survive breathing liquid PFC solution, called liquid breathing, which has been used in ICU settings. The ability of liquid perfluorochemicals (PFCs) to support liquid breathing was first demonstrated in the early 1960s by immersing a mouse in a glass beaker filled with an oxygenated PFC. Although it was completely submerged in liquid, the mouse was able to breathe, which proved that the PFC was able to facilitate the exchange of oxygen and carbon dioxide. PFCs are entirely man-made, thus eliminating the risk of transmitting viruses and infection from donor material. They are also compatible with all blood types and have a shelf life of approximately 2 years.
After intravenous administration, the droplets of this emulsion are taken up by the lymphatic system and slowly broken down. They are then transported to blood, where they are bound to lipids and move to the lungs. PFCs are typically removed from the body by exhalation.
The first PFC to be marketed was withdrawn from the market due to adverse effects and other problems. Even Oxygent, the most recent PFC to be studied, has showed an increased incidence of stroke in recipients, and trials have been halted.9
Hemoglobin-Based Blood Substitutes
HBBS, sometimes referred to as hemoglobin-based oxygen carriers (HBOCs), use purified human, animal or recombinant hemoglobin. A solution containing hemoglobin not contained within a red blood cell has many advantages over red blood cells, including the ability to withstand sterilization and a shelf life of approximately 2 years at room temperature. Many products have been on the market or in production for years, including HemAssist, Hemopure, Hemolink, PolyHeme and Hemospan.
Hemopure is also known as hemoglobin glutamer-250 (bovine) or HBOC 201. Hemopure is made of chemically stabilized cow hemoglobin situated in a salt solution. It is smaller in size (up to 1,000 times smaller than a typical red blood cell) and has less viscosity than human red blood cells. This means it can carry more oxygen at a lower blood pressure than red blood cells. Also, because of its smaller size, it can carry oxygen through partially obstructed or restricted blood vessels where red blood cells cannot reach. Its advantages over blood include the ability to be stored at room temperature, it is ready to use quickly and has a 3-year shelf life.
Made by the same company as Hemopure, Oxyglobin solution is the first and only oxygen therapeutic to be both U.S. FDA- and European Commission-approved for veterinary use. In 2004, cyclist Jesus Manzano admitted to using Oxyglobin during a Spanish national time trial championship and during the Tour de France, where he became sick and crashed.9
PolyHeme, which utilizes human hemoglobin as the oxygen-carrying molecule in solution, originally began as a military project following the Vietnam War and has since shown great potential for both military and civilian use.9
Hemospan is produced in powder form, allowing it to be stored for years, according to scientists. The powder can be mixed into liquid form and transfused immediately, regardless of a patient's blood type. The starting material for Hemospan is unmodified hemoglobin from outdated human red blood cells; however, the source could be any form of hemoglobin--human, animal or recombinant.9