Question 1

What is the minimum acceptable haematocrit for different patient populations?

Accepted Answer

For healthy adults: Hct 21–24% (Hb 7–8 g/dL). For elderly or those with cardiovascular disease: Hct 30% (Hb 10 g/dL). For neonates and infants: Hct 30–35% depending on clinical status. These thresholds are guidelines — individualise based on the patient's physiology, ongoing blood loss, and symptoms.

Question 2

How does the MABL change if the patient donates autologous blood preoperatively?

Accepted Answer

Preoperative autologous blood donation reduces the total circulating blood volume, paradoxically decreasing MABL. This approach has largely been replaced by intraoperative cell salvage and tolerance of normovolaemic anaemia.

Question 3

Should MABL be recalculated if preoperative Hct changes?

Accepted Answer

Yes. MABL should be recalculated when the latest preoperative Hct is available (ideally within 72 hours of surgery). A lower-than-expected Hct may necessitate postponement or preoperative optimisation.

Question 4

Is MABL used for paediatric patients?

Accepted Answer

Yes. Paediatric EBV is higher per kg (80–85 mL/kg for children, 90–100 mL/kg for neonates). The minimum acceptable Hct is higher in neonates and small infants due to decreased cardiac reserve. MABL calculations are particularly important in paediatric surgery due to small absolute blood volumes.