Generally adverse reactions of blood transfusion are (1) non immune mediated and (2) immune mediated. Fortunately the common adverse reactions that occurs after blood transfusion are mild and serious adverse reactions occur only rarely, if ever.

The blood transfusion may also be complicated by transmission of infectious agents, such as virus, bacteria, and other infectious agents. Fortunately the transmission of infectious agents is also rare, especially viral transmissions are becoming rarer due to pretransfusion screening of donor’s blood.

What are the non immune mediated adverse reactions that can occur?

The non immune mediated adverse reactions that can occur after transfusion of blood and blood components are volume overload, hypothermia (subnormal body temperature), electrolyte imbalance (mainly toxicity), iron overload, hypotensive reactions and immunomodulation etc.

During the time of evolution of humans, the food supply was intermittent and for survival there was need to store energy in excess of what is required for immediate use. Fat cells did the job of storing energy, which are widely distributed in adipose tissues. The fat cells can store excess energy efficiently as triglyceride and, when needed, release stored energy as free fatty acids for use at other sites. This physiologic system developed during the time of evolution acts through endocrine and neural pathways and even can permit humans to survive starvation for as long as several months. But at present era of nutritional abundance, sedentary lifestyle, and influenced importantly by genetic endowment, this physiologic system of storing energy in adipose tissues can produce obesity and adverse health consequences due to obesity.