Maintaining a safe blood supply will require constant vigilance on the part of blood-banking and public health officials. No one could have predicted the enormous challenges created by the AIDS pandemic, and no doubt new challenges will arise in the years ahead. One such relatively new concern is terrorism (see Chapter 12). Officials in the United States are concerned about the possibility that terrorists could obtain access to the smallpox virus and use it against the public. Before 1972, vaccinia, the live virus used in smallpox vaccinations, was routinely administered to Americans. Smallpox can be highly infectious - for example, a scab at the inoculation site can contain infectious virus, so it is possible for a scab that spontaneously separates from the skin to inadvertently infect close contacts that touch the vaccination site or dressing. Another area of concern is blood-banking. In response to this potential threat, the United States Department of Health and Human Services (HHS) has been working with state and local governments to strengthen preparedness. Part of the strategy is to expand the national stockpile of smallpox vaccine, which is highly effective when administered shortly after exposure. To make certain the virus is not transmitted through a blood transfusion, potential donors will be asked at blood collection facilities about a history of vaccination or close contact with anyone who has been vaccinated. A vaccine recipient who has had no complications may donate after the vaccination scab has spontaneously separated, or 21 days after vaccination, whichever is the later. Individuals who receive a smallpox vaccination may be asked to refrain from donating for an interval of two months if a scab was pulled off or knocked off (i.e. did not spontaneously separate), and to refrain for 14 symptom-free days if there has been a complication or contact with a vaccine recipient that developed skin lesions or other complications. If smallpox vaccinations were to be administered rapidly to a large section of the population, this would have a substantial negative effect on the blood supply, particularly platelets. The current FDA recommendation is for individuals to refrain from donating blood for one month after smallpox vaccination.
Another future consideration for blood safety is "pathogen inactivation." Several large corporations have spent hundreds of millions of dollars exploring this. There are different approaches to pathogen inactivation of red cells, platelets, and plasma; since the functionality of red cells, platelets, and plasma proteins are different in their fragility, the function of each must be preserved to be effective. These approaches involve exposing each single blood component to a chemical, sometimes along with UV light, such that viruses, bacteria, and parasites would be inactivated and no longer infectious. These processes require addition of inactivating chemicals to the blood, then washing out these chemicals so the patient is not exposed to the chemical. To perform this inactivation on each component would be expensive and require very large laboratories, and would generate huge volumes of hazardous waste (the wash solution). Due to the increasing safety of blood for transfusion that has occurred in the last 20 years, it is questioned whether this (now) small incremental (theoretic) improvement in safety is worth the huge expense (and risk to staff in handling all these chemicals). Clinical trials of these processes have been terminated (red cells), though some continue (platelets).
Traditionally a conservative group, blood-bankers, sensitive to patient safety, public perception, and regulatory agencies (e.g. FDA), have been slow to change longstanding processes developed earlier to improve safety. Following this tradition, more and more tests will be added to each donation, more and more questions will be asked of all prospective donors, and more and more donors will be deferred - such that the blood supply will dwindle. To offset this, major initiatives to encourage donations from new donors, and more frequent donations from existing suitable donors, will continue to be needed.
For some time it has been a popular lay belief that "artificial blood" or "synthetic blood" will solve this problem. Truly synthetic blood is represented by perfluorocarbons that can carry and release oxygen. Several trials have been discontinued due to safety concerns. Other problems include that the beneficial effect is brief, administration of 100 percent oxygen is required during its use, and the recipient patient's blood is then milky, interfering with the interpretation of many clinical laboratory test results. These perfluorocarbons have no role other than oxygen delivery, and cannot supplant the need for platelet or plasma transfusion.
Some refer to stroma-free hemoglobin solutions as artificial blood, but the source is still blood. Advantages include extended shelf-life and more lax storage conditions, no need to match blood type, and presumed lack of infectious risk. Some clinical trials with this have been halted due to safety concerns as well, and the beneficial effect in the recipient is short-lived - again, it is just a bridge until transfusion of traditional red cells becomes available. A bovine-sourced hemoglobin continues to face multiple challenges in getting through regulatory and other hurdles.
There is no artificial substitute for platelets on the horizon. Several isolated plasma proteins have been synthesized (Factor VIII and Factor IX for example), and others can be (albumin) but it wouldn't be cost-effective. No substitute for gamma globulin is expected, since this requires the panoply of antibodies from >1000 donors to all the things these donors have been exposed to. This changes as the population is exposed to new infectious and other agents to which they make antibodies.
Multiple attempts to grow blood cells in tissue culture and propagate them have not yet been fruitful.
While pathogen inactivation may help to maintain safety for additional infectious threats, it would be expensive. It might eventually, however, permit more individuals to be eligible as donors, and various approaches to pathogen inacti-vation appear applicable to red cells, platelets, and plasma.
The bottom line is that for quite some time we will continue to be dependent on altruistic voluntary donations from more and more people, and more and more often. If eligible, please give blood. In the United States you can make an appointment at a site convenient to you by calling 1-800-GIVE LIFE. If not eligible, encourage friends, family and acquaintances that may be eligible to donate.
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