Significant blood loss
A massive transfusion protocol is used when significant blood loss is present such as in major trauma, when more than ten units of blood are needed. Packed red blood cells, fresh frozen plasma, and platelets are generally administered. Typically higher ratios of fresh frozen plasma and platelets are given relative to packed red blood cells. Unknown blood type
Because blood type O negative is compatible with anyone, it is often overused and in short supply. According to the American Association of Blood Banks, the use of this blood should be restricted to persons with O negative blood, as nothing else is compatible with them, and women who might be pregnant and for whom it would be impossible to do blood group testing before giving them emergency treatment. Whenever possible, the AABB recommends that O negative blood be conserved by using blood type testing to identify a less scarce alternative. Religious objections
Jehovahs Witnesses may object to blood transfusions because of their belief that blood is sacred. Research into alternatives
Although there are clinical situations where transfusion with red blood cells is the only clinically appropriate option, clinicians look at whether alternatives are feasible. This can be due to several reasons, such as patient safety, economic burden or scarcity of blood. Guidelines recommend blood transfusions should be reserved for patients with or at risk of cardiovascular instability due to the degree of their anaemia. In these cases parenteral iron is recommended.
The prevalence of type O blood among Indigenous people of the Andean region meant such procedures would have held less risk than blood transfusion attempts among populations with incompatible blood types, which contributed to the failures of early attempts in Europe. Animal blood
Working at the Royal Society in the 1660s, the physician Richard Lower began examining the effects of changes in blood volume on circulatory function and developed methods for cross-circulatory study in animals, obviating clotting by closed arteriovenous connections. The new instruments he was able to devise enabled him to perform the first reliably documented successful transfusion of blood in front of his distinguished colleagues from the Royal Society.According to Lowers account, "...towards the end of February 1665 [I] selected one dog of medium size, opened its jugular vein, and drew off blood, until its strength was nearly gone. Then, to make up for the great loss of this dog by the blood of a second, I introduced blood from the cervical artery of a fairly large mastiff, which had been fastened alongside the first, until this latter animal showed ... it was overfilled ... by the inflowing blood." After he "sewed up the jugular veins", the animal recovered "with no sign of discomfort or of displeasure". Lower had performed the first blood transfusion between animals.