Table 3 Single-factor chi-square analysis of operational variables (N = 167)

Hidden blood loss (△Hb) (g/L)

△Hb < 10

30

18.00

19.30 ± 6.56

2.729

0.031

10 ≤ △Hb < 20

56

33.50

20.77 ± 8.23

20 ≤ △Hb < 30

43

25.70

17.84 ± 4.54

30 ≤ △Hb < 40

32

19.20

18.94 ± 5.55

40 ≤ △Hb

6

3.60

12.83 ± 3.66

Surgery begins

< 14:00 P.M.

53

31.70

18.86 ± 6.60

0.525

0.470

≥ 14:00 P.M.

114

68.30

19.66 ± 6.75

Op-duration T (h)

T < 2

24

13.50

17.92 ± 3.96

4.524

0.002

2 ≤ T < 3

97

55.90

18.38 ± 5.49

3 ≤ T < 4

35

25.20

23.00 ± 9.78

4 ≤ T < 5

3

1.40

15.33 ± 2.08

5 ≤ T

8

4.00

16.00 ± 3.21

Transfusion

No

152

91.00

18.82 ± 6.15

2.682

0.071

Yes

15

9.00

22.07 ± 10.25

Urine tube

No

33

19.80

17.70 ± 6.46

1.882

0.172

Yes

134

80.20

19.46 ± 6.67

Drainage

No

147

88.00

19.09 ± 6.56

8.345

0.894

Yes

20

12.00

19.30 ± 7.36

Tourniquet

No

2

1.20

12.50 ± 3.54

2.021

0.157

Yes

165

98.80

19.19 ± 6.63