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.

Volume or Fluid Overload:

As the blood and blood components are excellent volume expenders, blood or blood component transfusion can lead to rapid volume/fluid overload.To minimize the problem of volume/fluid overload, close monitoring (volume and rate of transfusion) of blood and blood component transfusion is essential.

Hypothermia:

Hypothermia can be a problem when frozen (sometimes below –18°C) or refrigerated (4°C) blood components are transfused, especially if transfusion is done rapidly. Problems such as cardiac dysarrhythmia can arise due to exposure of heart to cold blood component. To prevent the above problem, in-line warmer should be used.

Electrolyte Excess/toxicity:

Blood transfusion may lead to electrolyte excess and toxicity, especially if repeated blood transfusion is required. Commonly encountered electrolyte excess/toxicity include hyperkalemia (potassium excess), citrate excess etc. Potassium excess is due to leakage of potassium from RBCs (red blood cells) during storage, which increases concentration of potassium in serum. Patients with renal failure and neonates are at high risk of developing hyperkalemia. To prevent hyperkalemia, especially in neonates, as it can be fatal, fresh blood or washed RBCs should be used.

Hypocalcemia (low calcium in blood) can be also a problem of blood transfusion, especially after frequent and repeated transfusion. Hypocalcemia is due to presence of citrate, which is used as anticoagulant for storing blood, which chelates calcium. Hypocalcemia is manifested as numbness and/or tingling sensation of the fingers and toes. Calcium administration is generally not required as citrate is metabolized to bicarbonate very rapidly. If intravenous calcium is ever required it should be administered using separate intravenous line.

Hypotension:

Hypotension or low blood pressure of transient nature can be seen after blood transfusion in those patients who are using angiotensin-converting enzyme inhibitors (ACEIs) for treatment of high blood pressure (hypertension). Hypotension is due to presence of high concentration of bradykinin which is degraded by angiotensin-converting enzyme and this enzyme is inhibited by ACEIs.

Generally no treatment is required for transient low blood pressure and blood pressure returns to normal without any intervention.

Iron Overload:

Repeated blood transfusion, especially concentrated RBCs can lead to iron overload as one unit of RBC contain 200-250 mg of iron. Iron overload is a common problem after transfusion of 100 units of RBC which contain approximately 20 grams of iron.

Iron overload may be prevented by judicious use of RBC transfusion, which is also cost effective and use of alternative therapy such as erythropoietin. Chelating agent used in iron toxicity, desferrioxamine is of help but may give less than expected result in many cases. Other chelating agents such as calcium editate may also be helpful in some cases.

The signs and symptoms of iron overload include vomiting, blood in the vomit (hematemesis), abdominal pain, diarrhea, lethargy, dehydration, hypotension, acidosis, convulsion and shock.

Immune Suppression:

This may occur in repeated blood transfusions and risk of infection may increase. This is supported by the fact that patients receiving multiple blood transfusions the incidence of graft rejection is lower and cancer patients receiving blood transfusion have poor outcome.

To prevent immune suppression by blood transfusion, leukocyte-depleted (WBC or white blood cell depleted) blood products should be used as immune suppression is most likely mediated by transfused white blood cells. Fortunately in is a universal practice these days to transfuse leukocyte-depleted blood.

Related Articles:

1. Immune Mediated Adverse Reactions in Blood Transfusion

2. What Infections can be Transmitted by Blood Transfusion?