In adult with normal hemoglobin and hematocrit blood losses more than 20% of their blood volume (or hematocrit falls below 30%) are to be replaced with blood (while in western countries replacement may be required on loss more than 25 to 30%). A few important indications of transfusion of blood are mentioned below.
• Losses less than 20% can be replaced with crystalloids or colloids (colloids preferred).
• Another indication for transfusion of blood is in children losses more than 10% of their blood volume should be replaced with blood (in western countries replacement is required if loss is more than 15%).
• Minimum acceptable hemoglobin level for elective surgery is 10 g% and hematocrit 35%. Anything lass than these levels comes among the important indications of transfusion.
1 unit of blood raises the hemoglobin by 0.8 g% in India while in western countries by I g% because in India, I unit of blood = 350 ml (301 ml of blood + 49 ml of anticoagulant) while in western countries I unit contains 450 ml (out of which 63 ml is anticoagulant). One unit of fresh blood (with 100% RBCs while stored blood has only 70% RBCs) increase Hb by 1 g%.
• Blood products should not be infused with 5% dextrose (dextrose can cause hemolysis), ringer lactate and haemaccel (as these solutions contain calcium which with citrate can induce clot formation).
As such all patients undergoin major surgeries are to be anticipated for blood losses and blood should be kept ready after crossmatching before any indication for transfusion actually arise.