Final answer:
Clinicians must know your blood type before surgery to avoid hemolytic transfusion reactions from incompatible blood, which can be fatal. Cross matching determines compatibility unless type O universal donor blood is used in life-threatening emergencies.
Step-by-step explanation:
It is crucial for clinicians to know your blood type before surgery to ensure that any blood transfused is compatible with your own. A mismatched blood transfusion can lead to a hemolytic transfusion reaction (HTR), which is a potentially lethal immune response. During such a reaction, antibodies in the recipient's blood attack the transfused blood cells, leading to their destruction.
Cross matching is the process used to determine blood type and compatibility, which is vital except in extreme emergencies where there is an immediate threat to life. In these cases, type O blood, known as the universal donor type, may be used because it has no A or B antigens on the surface of its red blood cells to trigger an immune reaction.
Moreover, understanding blood types helps to manage risks associated with organ transplantation and enables personalized medical care, particularly with regard to anti-rejection drugs during such procedures. The history of blood transfusions improved drastically after the discovery of blood groups by Karl Landsteiner, before which transfusions often resulted in adverse reactions and deaths due to incompatibility.