Approximately 50% of all red blood cells are transfused in association with surgical procedures, many of which are elective in nature. On account of this large percentage, the transfusion practices of anesthesiologists and surgeons greatly impact on the blood resources of the community.
Ordering practices are those practices which relate to the anticipated or potential use of blood in association with surgery or invasive diagnostic procedures. Mostly, these develop on the basis of historical clinical experience with the procedure being performed. As shown in Table 9.1, there are various potential approaches to ensuring the availability of blood in the event of hemorrhage. This reflects nothing more than a hierarchy of probabilities that any allogeneic blood may need to be transfused. First, those situations where the blood use is exceedingly rare are unlikely to benefit from any blood-banking test for compatibility. Examples of these kinds of procedures are superficial skin biopsies or lumpectomies. In the past, specimens were routinely sent to the blood bank for typing, or screening, but this is wasteful. The next level is blood typing only, but this is of little value, as the patient's blood type has no diagnostic value in surgery. If blood is needed in an emergency, ABO identical blood could be issued, but this is no known gain in safety over the emergency issue of group O blood. A third level of request is the so-called "type and hold". This does not generally increase safety, since if blood is needed urgently, it will simply be issued as ABO identical or group O, i.e., similar to a "type only" request. A fourth level of request is "type and screen". This is a very useful request in situations where blood may (occasionally) be needed. From a practical point of view, this approach should be used for the majority of such surgical procedures. When a type and screen is requested, the ABO and Rhesus (D) type is determined and the serum screened for unexpected antibodies (see Chapter 8). A variation of type and screen is to screen for unexpected antibodies but not to type the patient ("screen and hold"). This is an interesting approach in the management of situations where blood transfusion is rarely required. If the antibody screen is negative, the transfusion of group O uncrossmatched blood has almost no statistical likelihood of a hemolytic reaction. Screen and "hold" is an uncommon request as most blood banks discourage performing a screen without a type and therefore "type and screen" is the more common approach.
For those procedures however, in which blood is commonly transfused, the approach is to type, screen and crossmatch (or have available electronically) a predetermined number of units sometimes called "type and crossmatch". Under
Table 9.1. Ordering practices: anticipated or potential use of blood
1. No specimen: Suitable when blood use is exceedingly rare.
2. Type only (ABO, Rhesus): A practice of no known value.
3. Type and "hold": Better to request #4 or consider #1, depending on the procedure.
4. Type and Screen: Suitable when blood use is occasional.
5. Screen and Hold: This is a reasonable approach if blood use is very occasional: However, blood banks have a bias to type always and probably #4 is preferable.
6. Type, screen and crossmatch: Suitable when blood use is common or routine.
these circumstances, compatible blood is identified and set aside for potential use, usually for a 48 or 72 hour period. There is no clear definition of what is considered "commonly transfused" but, in general, if blood is transfused in more than 50% of cases for any given surgical procedure, it is not unreasonable to have crossmatched blood available. The concept of crossmatching has undergone significant evolution, however. Patients with negative antibody screening (97% of specimens, Chapter 8) can now receive ABO identical blood dispensed without a technical procedure being performed (electronic crossmatch). This greatly expedites the availability of red cells in the event of unexpected hemorrhage. In the past, there has been a trend to over request crossmatched blood in order to give a "cushion" in the event of unexpected hemorrhage. This approach results in unnecessary crossmatches and a high crossmatch to transfusion ratio (CT Ratio). In situations where the antibody screen is positive, the blood bank commonly doubles the number of units made available (crossmatched) as a matter of practice. Therefore, the practice of over ordering crossmatched blood because of concern surrounding the potential inability of the blood bank to respond to unexpected situations should not be justifiable. Most over-crossmatching of blood has evolved as a perception issue on the part of operating room personnel that the blood bank will be unable to respond to an emergency situation. Therefore, development of good communication between the transfusion service, anesthesiologists and surgeons is critical in overcoming this perception.
On account of this, most institutions develop what is described as a maximum (surgical) blood ordering system or MBOS. This is a schedule where the number of units to be crossmatched, if any, are agreed by the surgical staff and a written list is assembled. When the MBOS is implemented, there tends to be a significant reduction in the amount of blood that is routinely crossmatched. The MBOS list should ideally show three types of procedures: (a) These procedures for which a specimen is not required, (blood almost never transfused), (b) type and screen, only (blood rarely transfused) and (c) type and crossmatch for a predetermined number of units (blood commonly transfused). The surgical procedures can be
arranged by surgical service, alphabetically, or procedural code. At the time of sample collection (if appropriate), the request should indicate the type of surgical procedure and surgical code (e.g., CPT code or other). This can then be translated into a type and screen, or type and crossmatch, by the blood bank staff.
Related to ordering practices for blood transfusion is decision making regarding transfusion. This is often called "transfusion practices" or "transfusion styles". Transfusion practices and styles tend to evolve on the basis of empiric clinical experience and not on the basis of clinical studies. Transfusion styles differ from transfusion practices, but have in common their origin in empiric clinical experiences. Transfusion styles often have developed from unanalyzed, partially analyzed, and occasionally anecdotal experiences. Table 9.2 shows important distinctions between transfusion practices and transfusion styles. Both can result in either over use or inappropriate use of blood transfusion, but, also potentially, under use of blood transfusion. The most important difference between transfusion practices and transfusion styles is the ability to effect intra-institutional change. Transfusion practices evolve on the experience of a physician or group of physicians within an institution. They are left unchanged until challenged with data or educational material. Under such circumstances, these practices can be changed, resulting in a better utilization of blood products. Transfusion styles differ, however. Transfusion styles, although possibly based initially on empiric, often anecdotal, clinical experience, are often reinforced by the culture of a department within
Table 9.2. Importance of differentiating transfusion practices from transfusion styles
1. Develop/evolve within the framework Develop/evolve within the of empiric clinical experience framework of empiric clinical experience or tradition, sometimes anecdotal
2. Determined by individual physician or group experience
3. Often amenable to change by logic, hard data and education
4. New physicians on staff may influence practices and cause change
5. May result in product wastage
Institutionally determined by culture or attitude
Resistant to change. Short term changes revert to old styles. Logic/data viewed skeptically. Change requires behavioral adjustment
New physicians on staff 'adapt' to the transfusion style (sometimes reluctantly)
Often results in product wastage an institution. They tend to be resistant to change. Educational intervention sometimes causes short-term changes, but reversion to the old transfusion styles tends to recur. New physicians on staff are frequently capable of changing transfusion practices. However, new physicians on staff tend not to influence transfusion styles; and adapt, in time, to the style of the institution. Questionable transfusion practices and transfusion styles result in considerable blood product wastage and unnecessary cost, reducing the available blood supply within the community.
Illustrative examples of transfusion styles are (1) the routine administration of plasma in association with red cell transfusions in surgery. In the past, surgeons or anesthesiologists would transfuse a unit of plasma for every two or three units of red cells transfused during surgery. For most patients with normal hemostatic mechanisms presurgically, there is no evidence that this is of any benefit. Transfusion of plasma may, however, be useful when large volumes of allogeneic red cells or salvaged autologous red cells are transfused (approximating, 0.5-1 blood volume) and initial replacement is red cells in crystalloid. (2) The routine transfusion of platelets presurgically, if the platelet count is less than 100 x 109/L outside of the context of neurosurgical or ophthalmic procedures. In clinical situations where the operative field is well visualized and hemostasis can be controlled by good surgical technique, this practice is of no known benefit. Patients who exhibit excessive microvascular oozing with platelet counts less than 50 x 109/L, may, on the other hand, benefit from platelet transfusions. (3) The routine transfusion of red blood cells to patients with a hemoglobin below 10 g/dL. There is no empiric justification for this approach which, until recently, was largely unchallenged. Some patients, however, may indeed, benefit from transfusion if the hemoglobin is less than 10g/dL in situations where the clinical circumstances indicate critical organ ischemia, and there is risk of imminent hemorrhage (Chapter 26).
The importance of ordering practices, transfusion practices and styles cannot be overemphasized. The ability of the transfusion service to function adequately to meet the surgical needs and promote the optimal usage of blood resources in a community are significantly jeopardized by inappropriate institutional practices or transfusion styles. Much of clinical transfusion medicine is concerned with understanding these practices and styles and intervening to effect a change to better transfusion practice.
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