Question 1

What is the expected haemoglobin increment per unit of PRBC?

Accepted Answer

In a 70 kg adult, 1 unit of PRBC raises haemoglobin by approximately 1 g/dL (or haematocrit by ~3%). In children, the increment per mL/kg transfused is more predictable: 3 mL/kg PRBC raises Hb by ~1 g/dL.

Question 2

Should I transfuse to a target Hb or a target haematocrit?

Accepted Answer

Both are acceptable. Hb is more directly relevant to oxygen-carrying capacity. The target Hb is typically 7–8 g/dL for most stable patients. Higher targets (8–10 g/dL) are reserved for acute coronary syndrome or ongoing haemorrhage.

Question 3

Does the calculator account for wastage in the transfusion line?

Accepted Answer

The formula assumes no wastage. In neonates and small infants, the dead space of the transfusion line may represent a significant proportion of the administered volume — the calculated volume should be increased by 15–20% or the line primed with compatible blood.

Question 4

How does the calculator apply to massive transfusion?

Accepted Answer

In massive transfusion (replacement of >1 blood volume in 24 hours), the simple Hb deficit formula underestimates requirements because of ongoing loss, dilution, and consumption. A 1:1:1 ratio of PRBC:FFP:platelets (e.g., 6 PRBC + 6 FFP + 1 pool platelets) is recommended as a starting point, adjusted by thromboelastography (TEG/ROTEM) if available.