Transfusion reactions and massive transfusion: SAQ

Part A — The acute transfusion reaction (10 marks)

The first response to any suspected acute transfusion reaction is to stop the transfusion at once and keep the intravenous line open with normal saline, then check the airway, the breathing and the circulation and give oxygen if the child is breathless or hypoxaemic. The identity of the child, the wristband and the unit label are checked against the paperwork at the bedside, because the acute haemolytic reaction is most often an ABO mismatch from a clerical error that gave the wrong unit to the wrong patient. The unit and the fresh blood samples are returned to the blood bank with a report, and the reaction is reported through the haemovigilance system. [4][11]

The diagnosis of the acute haemolytic reaction is confirmed by the direct antiglobulin test, which shows that antibody or complement has coated the transfused red cells, together with a fall in haemoglobin, a rise in lactate dehydrogenase and bilirubin, a fall in haptoglobin and haemoglobinuria. The repeat of the group and the antibody screen identifies the antibody and the mismatch, and the blood bank repeats the crossmatch on the unit and the samples. The mechanism is the binding of a preformed immunoglobulin M antibody against the A or the B antigen to the transfused red cells, the activation of the complement cascade and the destruction of the red cells within the blood vessel, with the free haemoglobin and the complement fragments driving the fever, the hypotension, the renal injury and the disseminated intravascular coagulation. [3][4]

Part B — The massive transfusion protocol (10 marks)

The massive transfusion protocol is activated the moment a child is recognised to be bleeding faster than the body can replace, defined practically as the replacement of one blood volume in twenty-four hours or the ongoing haemorrhage with shock. The principle is the balanced delivery of red cells, fresh frozen plasma and platelets in a ratio that approaches one unit of red cells to one unit of plasma to one pool of platelets, so that the dilutional coagulopathy is prevented as the bleeding is controlled. Tranexamic acid is given early in trauma, within the first three hours of injury, and the child is warmed throughout to prevent the hypothermia that impairs the coagulation and the platelet function. [9]

The hazards that the protocol must prevent are the citrate toxicity, the hypothermia and the electrolyte disturbance of the rapid transfusion. The citrate in the stored components binds the ionised calcium faster than the liver can metabolise it, so the ionised calcium is monitored and replaced as it falls. The cold blood causes the hypothermia that impairs the coagulation, so the blood is warmed through the device. The stored red cell unit, especially if old or irradiated, carries a high potassium load that causes the hyperkalaemia and the arrhythmia, so the freshest unit is chosen for the large transfusion. The child is monitored for the hypocalcaemia, the hypothermia and the hyperkalaemia throughout the massive transfusion, and the laboratory is used to guide the component delivery and the electrolyte correction. [9][11]