Calculation methods
Uterine leiomyoma is approximately elliptical, so we calculate its
volume according to the following formula:
Volume (cm³) = \(\frac{\pi}{6}\) * ( a*b*c),
where a, b and c are the three largest vertical diameters of uterine
fibroids measuring by ultrasound scan (USS).(16)
We calculate estimated blood volume (EBV) by referring to the formula
used by Nadler,(17) as follows:
EBV (L) = 0.3561 × height (m) ³ + 0.03308 × weight (kg) + 0.1833
(females).
We used preoperative Hct, Hct on the third post-operative day and EBV to
calculate the total
blood loss (TBL) according to the method of Gross,(18) as follows:
TBL (mL) = EBV (L)
×\(\frac{(preoperative\ Hct-\ postoperative\ Hct)}{\text{average\ Hct}}\)×
1000.
In this formula, the average Hct is the average of the preoperative and
postoperative Hct.
If there is a blood transfusion during the operation, the blood loss
calculated from the change in Hct will be smaller than the actual TBL.
Therefore, the true TBL is equal to the TBL calculated by the Gross
formula plus the amount of blood transfusion.
True TBL (mL) = TBL (mL) + blood infused (mL).
The true TBL is equal to the sum of the Intra-operative blood loss
(IBL), post-operative drainage volume, and HBL. Visible blood loss (VBL)
is equal to the IBL plus the post-operative drainage volume.
Post-operative blood loss (PBL) in patients was equal to the HBL plus
the post-operative drainage volume. Thus, the HBL, VBL and PBL in the
patients were calculated as follows:
HBL (mL) = True TBL (mL)− IBL (mL) − blood drained (mL),
VBL (mL) = IBL (mL) + blood drained (mL),
PBL (mL) = HBL (mL) + blood drained (mL).
On the second or third day after surgery, the body hemodynamics of
patients tend to be stable, so we assumed that the blood volume on the
third day after surgery was the same as that at admission. We use
pre-operative and post-operative Hb to calculate the Hb loss, as
follows:
Hbloss (g/L) = Hbpre –
Hbpost,
in which Hbpre is the pre-operative Hb,
Hbpost is the Hb on the third post-operative day, and
Hbloss is the loss of Hb.