Haemolysis can be dividided into Acute Intravascular and Delayed (usually extrvascular).
Both are detailed below:
Haemolysis: Acute Intravascular
Usual cause
Immunologic destruction of transfused red cells, nearly always due to incompatibility of antigen on the transfused cells with antibody in the recipient circulation. Most common cause is transfusion of ABO-incompatible blood. Rarely due to physical or chemical damage to transfused red cells e.g. effects of drugs, co-administered with transfusion, effects of bacterial toxins, thermal injury due to freezing or overheating or transfusion of red cell antibodies.
Incidence
Variably reported for ABO incompatibility as 1:12,000-77,000 (2).
Main clinical features
Characteristically begins with an increase in temperature and pulse rate; symptoms may include chills, dyspnoea, chest or back pain, abnormal bleeding or shock. Instability of blood pressure is frequent. In anaesthetised patients, hypotension and evidence of DIC may be the first sign.
Investigation
Clinical assessment. Clerical check of ABO typing of patient and unit. Perform Direct Antiglobulin Test (DAT) and Indirect Antiglobulin Test (IAT), renal function, tests for haemolysis etc.
Intervention
Stop transfusion immediately. Maintain blood pressure and renal output. Seek urgent Medical assistance. Inform the laboratory responsible for dispensing blood for transfusion. Inform ARCBS.
Haemolysis: Delayed (Usually Extravascular)
Usual cause
Usually occurs in previously red cell alloimmunised patients in whom antigens on transfused red cells provoke anamnestic production of red cell antibody. Usual timeframe is 2-14 days after transfusion.
Incidence
1:4,000-9,000 (2).
Main clinical features Signs may include unexplained fever, development of a positive DAT, jaundice and unexplained decrease in haemoglobin.
Investigation
DAT and IAT. Liver function tests. Markers of haemolysis (urinary haemosiderin, haptoglobin etc.).
Intervention
Most delayed haemolytic reactions have a benign course and require no treatment. Perform antibody identification and provide antigen negative blood if further transfusion is needed. Inform ARCBS.