Table 3 Assessment of risk factors for delirium. Patient characteristics were stratified by post-operative delirium status. Significant difference was observed for age, use of sedative-hypnotics, pre-operative Hb, post-operative day 1 Hb, pre-operative Ht, post-operative day 1 Ht, and post-operative day 3 BUN

Age (years)

79.5 ± 6.9

73.0 ± 9.0

0.021*

Sex (male / female)

2/9

30/129

0.955

Type of surgery (unilateral / bilateral TKA)

4/7

88/71

0.221

History of hypertension (n) (%)

9 (81.8%)

86 (54.1%)

0.061

History of diabetes (n) (%)

2 (18.2%)

25 (15.7%)

0.832

History of ischemic heart disease (n) (%)

0 (0%)

5 (3.1%)

0.410

Use of sedative-hypnotics (n) (%)

5 (45.5%)

27 (17.0%)

0.036*

Estimated blood loss (ml)

543 ±169

741 ±594

0.273

Pre-operative levels of Hb (g/dl)

11.6 ±1.7

13.2 ±1.4

<0.001*

Post-operative day 1 Hb (g/dl)

9.9 ±1.6

11.0 ±1.4

0.028*

Post-operative day 3 Hb (g/dl)

8.9 ±1.5

10.4 ±7.7

0.519

Pre-operative levels of Ht (%)

34.8 ±4.7

39.7 ±3.9

<0.001*

Post-operative day 1 Ht (%)

30.4 ±4.7

33.2 ±4.2

0.034*

Post-operative day 3 Ht (%)

26.9 ±4.6

29.5 ±4.8

0.077

Post-operative day 1 TP (g/dl)

5.89 ±0.3

5.68 ±0.5

0.184

Post-operative day 3 TP (g/dl)

5.49 ±0.34

5.54 ±0.57

0.775

Post-operative day 1 Alb (g/dl)

3.28 ±0.17

3.21 ±0.30

0.443

Post-operative day 3 Alb (g/dl)

2.76 ±0.29

2.80 ±0.36

0.766

Post-operative day 1 BUN (mg/dl)

14.9 ±6.4

14.2 ±7.2

0.763

Post-operative day 3 BUN (mg/dl)

20.5 ±8.3

14.2 ±7.3

0.008*

Post-operative day 1 Cr (mg/dl)

0.80 ±0.29

0.80 ±1.33

0.987

Post-operative day 3 Cr (mg/dl)

0.89 ±0.28

0.80 ±1.40

0.835

Post-operative day 1 Na (mmol/l)

138.7 ±3.4

139.0 ±2.4

0.740

Post-operative day 3 Na (mmol/l)

138.6 ±2.8

140.0 ±3.0

0.147

Post-operative day 1 K (mmol/l)

4.15 ±0.59

4.27 ±3.40

0.908

Post-operative day 3 K (mmol/l)

3.88 ±0.39

3.90 ±0.41

0.868

Post-operative day 1 Cl (mmol/l)

105.6 ±3.2

105.5 ±2.6

0.966

Post-operative day 3 Cl (mmol/l)

105.3 ±3.0

105.9 ±3.2

0.623

Post-operative day 1 Ca (mg/dl)

8.65 ±0.64

8.36 ±0.36

0.307

Post-operative day 3 Ca (mg/dl)

8.90 ±0.41

8.39 ±0.15

0.281