Chapter 18: Transfusion

INTRODUCTION

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.

DANGERS IN BLOOD SUPPLY

Blood can easily transmit human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), Chagas 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

AVOIDING BLOOD TRANSFUSION

Use non-blood substitutes, if possible. They are much safer, easier to use, and can be 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 18-1.³

DECIDING WHEN TO TRANSFUSE

The decision to transfuse blood depends on the patient’s clinical condition and 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, does not change mortality rates.⁵ The mortality increases dramatically, however, when the Hgb drops lower than 5 to 6 g/dL, especially in postoperative patients.⁶

Severe Anemia