Hemolytic Transfusion Reaction - The incidence of immediate hemolytic transfusion reactions is estimated to be 1 per 6000-7000 units transfused. - Reactions to transfused blood products can occur as a result of the presence of constitutive antibodies ( e.g.,anti-A,anti-B ) - Mortality ranging from 20-60%. - Infusion of ABO incompatible blood is most commonly due to errors in taking or labelling the sample,collecting the wrong blood from the refrigerator or inadequate checking when the transfusion of the pack is being started.

- When incompatible blood is administered,Abs and complement in recipient plasma attack the corresponding antigens on donor RBCs Hemolysis ensues - The hemolytic reaction may take place in the intravascular space and/or it may occur extra- vascularly within the endoplasmic reticulum. - The antigen-antibody complexes activate Hage- man factor(factor 12) which in turn acts on the kinin system to produce bradykinin. - Bradykinin---> capillary permeability & dilate arterioles ---> hypotension

- Activation of the complement system release histamine and serotonin from masts cells bronchospasm - Hemolysis releases hemoglobin into the blood. - Initially it is bound to haptoglobin and albumin until the binding sites are saturated,then it circulate freely in the blood until it is excreted by the kidneys.

- Renal damage occurs for several reasons. 1. Blood flow to the kidneys is reduced in the presence of systemic hypotension and renal vasoconstriction 2. Free hemoglobin and RBC stroma may precipitate in the renal tubules,causing mechanical obstruction and nephrotoxicity 3. Antigen-antibody complexes may be deposited in the glomeruli 4. If the patient develops DIC ,fibrin thrombi will also be deposited in the renal vasculature

- DIC commonly occurs with hemolytic transfusion reactions,probably because RBC stroma is severed,release erythrocytin,which activates the intrinsic system of coagulation. - This activated coagulation leads to fibrin formation.Subsequently,platelets and factors 1, 2,5 and 7 are consumed.

- Signs and symptoms may occur only 5-10ml transfusion of incompatible blood,so observe the patient carefully at the start of the transfusion of each blood unit. Symptoms & Signs # fever,chills,nausea and vomiting,diarrhea, rigors,restless,headache # flushing,dyspneic,bronchospasm (histamine) # hypotension,tachycardia (bradykinin effects) # chest & back pain result from diffuse intravascular occlusion by agglutinated RBCs. # hemoglobinuria # generalised oozing from wounds or puncture sites

** During general anesthesia ,many signs are masked. - Hypotension and hemoglobinuria and diffuse bleeding may be the only clues that a hemolytic transfusion reaction has occurred. Management 1. If a reaction is suspected,the transfusion should be stopped and the identity of the patient and the labeling of the blood should be rechecked. 2. Maintenance of systemic blood pressure --> volume,pressors,inotropes 3. Preservation of renal function

3. Preservation of renal function 3.1 Maintain the urine output at a minimum of 75 - 100 ml/hr by the following methods: # generously administer fluids intravenous & possibly mannitol 12.5-50 g,given over a 5 -15 minute period. # if intravenous administered fluids and mannitol are ineffective,then administer furosemide 20-40 mg IV 3.2 Alkalinize the urine;because bicarbonate is preferentially excreted in the urine,only 40-70 mEq/70kg of sodium bicarbonate is usually required to raise the urine pH to 8

4. Prevention of DIC - Currently,there is no specific therapy to prevent the develope of DIC - However,preventing hypotension and supporting cardiac output to prevent stasis and hypoperfusion,both of which contribute to the evolution of DIC,are important. - Laboratory tests to establish baseline coagulation status # platelet count # prothrombin time (PT) # partial thromboplastin time (PTT) # thrombin time (TT) # fibrinogen level # fibrin degradation products ( FDPs)

5. Blood samples should be collected in an EDTA tube,the specific tests should include 5.1 a repeat cross-match 5.2 a direct antiglobulin (Coombs) test definitive test for an acute hemolytic transfusion reaction 5.3 serum haptoglobin level,plasma and urine Hgb,and bilirubin concentrations