Table 1.
The specific computing process of four common calculated methods
| Calculated methods | Specific computing process | Index |
|---|---|---|
| Method 1: Gross equation[1,2,3] | BV = k1 × H3 + k2 × W + k3 | BV (ml): The patient’s blood volume before surgery |
| Vloss total = BV × (Hctpreop − Hctpostop) | H (m): Height | |
| For males, k1 = 0.3669, k2 = 0.03219, and k3 = 0.6041, while for females, k1 = 0.3561, k2 = 0.03308, and k3 = 0.1833 | W (kg): Weight | |
| Vloss total (ml): The total volume of RBC loss | ||
| Once the mean Hct value is determined, the total blood volume can be further calculated | Hctpreop and Hctpostop (ml): The Hct values before and after surgery | |
| Method 2: Hemoglobin balance[1,4,5,7] | Hbloss total = BV × (Hbi − Hbe) × 0.001 + Hbt | Hbloss total (g): The loss volume of Hb |
| Vloss total = 1000 × Hbloss total/Hbi | Hbi (g/L): The Hb value before surgery | |
| Generally, 1 U banked blood is considered to contain 52 ± 5.4 g Hb[5] | Hbe (g/L): The Hb value after surgery; | |
| Hbt (g): The total volume of blood transfusion | ||
| Method 3: OSTHEO formula[8,9,10,11,12,13] | Vloss total = VURL + VCRL | Vloss total: The total RBC loss |
| VURL = Vinitial − Vfinal | VURL: Uncompensated RBC loss (URL) | |
| Vinitial = BV × Hctpreop | VCRL: Compensated RBC loss (CRL). VCRL represents the combination of all the RBCs from various forms of transfusions | |
| Vfinal = BV × Hctpostop | ||
| BV = Z × k | ||
| For females, k = 2430, while for males, k = 2530 | Vinitial: The RBC volume before surgery (ml) | |
| Z (m2) = 0.0235 × H 0.42246 × W 0.51456 | Vfinal: The RBC volume after surgery (ml) | |
| A Hct of 35% indicates the total blood loss volume: Total blood loss volume = Total RBC loss volume (ml)/0.35. When the Hct = 60%, the RBC volume is equal to 250 ml, and when Hct = 100%, the RBC volume is equal to 150 ml/U[12,13] | Z: The body surface area, k is a regular value relating to sex | |
| Tallogeneic: Transfusion volume | ||
| Tdrainage: The volume of autologous transfusion or drainage | ||
| A Hct from autologous transfusion after surgery is considered to be 30% | ||
| VCRL = Tallogeneic × 150 + Tdrainage × 0.3 | ||
| Method 4: Hemoglobin dilution[1,14] | Vloss total (ml) = BV × (Hbi–Hbe)/Hbi | Hbdecrease (g/L): The decrease in Hb |
| Hbe = Hbi − Boodloss total × Hbi/BV | ||
| Hbdecrease = Hbi − Hbe = Boodloss total × Hbi/BV |
OSTHEO: Orthopedic Surgery Transfusion Hemoglobin European Overview; Hct: Hematocrit; Hb: Hemoglobin; Preop: Preoperative; Postop: Postoperative; URL: Uncompensated RBC loss; CRL: Compensated RBC loss; RBC: Red blood cell.