In austere situations, there may be no blood available for transfusion. If blood is available, there is a greater risk that it could be contaminated and infect the patient than under optimal circumstances. In addition, the methods to rapidly rewarm blood to avoid the complications of hypothermic transfusion may not be available.
Blood can easily transmit human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), Chaga's disease, malaria, and other diseases. Only about 66% of developed countries and 46% of least-developed countries screen blood for HIV, although there is about a 90% seroconversion rate following the transfusion of blood infected with HIV. Even where (often, for-profit private) blood banks purport to screen for HIV, many either don't screen or use insensitive tests. Government oversight is sparse.1,2
Use non-blood substitutes, if possible. They are much safer, easier to use, and (sometimes) less costly than using blood. Substitutes include crystalloids, synthetic colloids (e.g., Dextran), and noninfectious plasma derivatives. For all but crystalloids, however, both cost and availability may be a problem.
To avoid a transfusion, especially in the operative patient: (a) restrict preoperative diagnostic phlebotomy, (b) use meticulous intraoperative surgical hemostasis, (c) use blood/cell salvage, (d) employ hemodilution, (e) use pharmaceutical hemostasis agents, (f) maintain normothermia, and (g) position patients to minimize blood loss and hypertension. Postoperatively, (a) use blood/cell salvage, (b) tolerate anemia (as described later in this chapter), (c) optimize fluid and volume management, and (d) restrict diagnostic phlebotomy. The units of blood potentially saved by not doing a transfusion with each strategy are shown in Table 17-1.3
Table 17-1 Blood Conservation Methods in the Surgical Patient |Favorite Table|Download (.pdf)
Table 17-1 Blood Conservation Methods in the Surgical Patient
|Preoperative Options||Units of Blood Conserved|
|Tolerance of anemia (reduce transfusion trigger)||1-2|
|Increase preoperative red blood cell mass||2|
|Preoperative autologous donation||1-2|
|Meticulous hemostasis and operative technique||1 or more|
|Acute normovolemic hemodilution||1-2|
|Blood salvage||1 or more|
The decision to transfuse blood depends on the clinical condition of the patient and on their ability to compensate for reduced tissue oxygenation. Patients with evidence of severe cardiac or respiratory disease or with preexisting anemia have a limited ability to compensate.4 In critically ill, non-bleeding adult patients <55 years old and without evidence of an acute myocardial infarction or unstable angina, keeping the hemoglobin (Hgb) >7.0 g/dL, rather than >10 g/dL, results in no change in mortality.5 The mortality increases dramatically when the Hgb drops below 5 to 6 g/dL, especially in postoperative patients.6
Levels of anemia that would not be tolerated under optimal conditions can, and must, be tolerated when the blood supply is scarce or dangerous. The World Health Organization (WHO) defines very severe anemia in a child as an Hgb <4 g/dL (40 g/L) or a hematocrit (packed-cell volume; Hct) <12%. If the blood supply is tested for HIV and HBV, transfuse these children with 10 mL/kg packed red blood cells (RBCs). If the blood supply may be tainted, wait to transfuse until the Hgb is <3 g/dL (30 g/L) or the Hct is <10%.7 Also, limit the amount transfused. Critically ill ...