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Table 2 Effects of case mix factors on ultimate hospital outcome in admissions with acute kidney injury

From: Case mix, outcome and activity for patients with severe acute kidney injury during the first 24 hours after admission to an adult, general critical care unit: application of predictive models from a secondary analysis of the ICNARC Case Mix Programme Database

Case mix factor

 

Deaths (n)

n

%

Adjusted OR (95% CI)

P value

Age (years)

< 45

817

2,128

38.4

1.48 (1.44–1.52) per 10 year increase

< 0.001

 

45–54

846

1,776

47.6

  
 

55–64

1,671

3,086

54.1

  
 

65–74

2,991

4,866

61.5

  
 

75+

2,553

3,720

68.6

  

Sex

Female

2,905

5,217

55.7

Reference

0.004

 

Male

5,973

10,359

57.7

1.13 (1.04–1.22)

 

Past medical history

Absent

7,355

13,298

55.3

Reference

< 0.001

 

Present

1,523

2,278

66.9

1.82 (1.63–2.03)

 

CPR before admission

No

7,679

14,062

54.6

Reference

< 0.001

 

Yes

1,199

1,514

79.2

1.64 (1.41–1.90)

 

Mechanical ventilation

No

2,086

5,250

39.7

Reference

< 0.001

 

Yes

6,792

10,326

65.8

1.93 (1.76–2.12)

 

Surgery within 1 week of admission

No

6,324

10,751

58.8

Reference

< 0.001

 

Yes

2,554

4,825

52.9

0.80 (0.73–0.87)

 

Sepsis

No

4,362

8,207

53.1

Reference

< 0.001

 

Yes

4,516

7,369

61.3

1.14 (1.06–1.21)

 

Oliguria

No

4,766

9,660

49.3

Reference

< 0.001

 

Yes

3,844

5,466

70.3

1.90 (1.75–2.07)

 

Length of stay before unit admission

0 days

2,451

4,261

57.5

Reference

< 0.001

 

1 day

1,952

3,666

53.2

0.90 (0.81–1.01)

 
 

2–6 days

2,269

4,133

54.9

1.00 (0.90–1.12)

 
 

7+ days

2,199

3,508

62.7

1.54 (1.38–1.73)

 

Temperature (°C)a

< 32

68

89

76.4

1.96 (1.12–3.40)

< 0.001

 

32–34

399

557

71.6

1.32 (1.05–1.65)

 
 

34–36

2,779

4,595

60.5

1.11 (1.01–1.22)

 
 

36–38.5

2,918

5,789

50.4

Reference

 
 

38.5–39

882

1,680

52.5

0.96 (0.85–1.10)

 
 

39–41

1,614

2,595

62.2

1.16 (1.03–1.30)

 
 

≥ 41

185

217

85.3

3.35 (2.18–5.15)

 

Mean arterial pressure (mmHg)a

< 50

2,923

3,803

76.9

2.08 (1.80–2.41)

< 0.001

 

50–70

4,164

7,013

59.4

1.45 (1.28–1.65)

 
 

70–110

634

1,682

37.7

Reference

 
 

110–130

724

1,988

36.4

0.89 (0.77–1.04)

 
 

130–160

366

955

38.3

0.94 (0.78–1.13)

 
 

≥ 160

48

96

50.0

1.33 (0.83–2.12)

 

Heart rate (beats/minute)b

< 40

134

187

71.7

1.42 (0.97–2.08)

< 0.001

 

40–50

179

324

55.2

1.14 (0.87–1.50)

 
 

50–100

1,229

2,775

44.3

Reference

 
 

100–110

1,044

2,085

50.1

1.18 (1.03–1.35)

 
 

110–120

1,287

2,408

53.4

1.26 (1.11–1.44)

 
 

120–140

2,543

4,251

59.8

1.46 (1.30–1.64)

 
 

140–155

1,262

1,878

67.2

1.66 (1.43–1.93)

 
 

≥ 155

1,173

1,623

72.3

1.94 (1.66–2.28)

 

Respiratory rate (breaths/minute)b

< 6

403

628

64.2

1.05 (0.85–1.30)

0.001

 

6–12

1,836

3,509

52.3

1.00 (0.88–1.13)

 
 

12–14

1,771

2,867

61.8

1.19 (1.05–1.36)

 
 

14–25

1,395

2,397

58.2

Reference

 
 

25–35

2,007

3,784

53.0

1.04 (0.92–1.18)

 
 

35–40

689

1,109

62.1

1.33 (1.12–1.58)

 
 

40–50

608

1,015

59.9

1.16 (0.97–1.39)

 
 

≥ 50

135

203

66.5

1.49 (1.05–2.13)

 

Oxygenation (mmHg; A-aDO2 [FiO2 ≥0.5])b

A-aDO2 (FIO2 ≥ 0.5)

    

< 0.001

 

< 250

1,238

2,338

53.0

Reference

 
 

250–350

1,576

2,540

62.0

1.25 (1.12–1.40)

 
 

350–500

1,034

1,453

71.2

1.68 (1.45–1.94)

 
 

≥ 500

1,480

1,951

75.9

1.94 (1.69–2.23)

 
 

PaO2 (FIO2 < 0.5)

     
 

< 50

114

206

55.3

1.10 (0.80–1.53)

 
 

50–70

918

1,786

51.4

1.11 (0.98–1.26)

 
 

70–80

786

1,637

48.0

1.02 (0.90–1.16)

 
 

≥ 80

1,732

3,665

47.3

Reference

 

Arterial pHa

< 7.15

1,380

1,676

82.3

2.13 (1.82–2.49)

< 0.001

 

7.15–7.25

1,871

2,655

70.5

1.63 (1.46–1.83)

 
 

7.25–7.33

2,177

3,744

58.1

1.20 (1.09–1.32)

 
 

7.33–7.5

3,290

7,156

46.0

Reference

 
 

≥ 7.5

160

345

46.4

0.98 (0.76–1.26)

 

Serum sodium (mmol/l)a

< 120

187

326

57.4

1.49 (1.14–1.94)

< 0.001

 

120–130

1,506

2,654

56.7

1.19 (1.07–1.32)

 
 

130–150

6,590

11,687

56.4

Reference

 
 

150–155

358

537

66.7

1.45 (1.17–1.80)

 
 

155–160

153

221

69.2

1.48 (1.06–2.07)

 
 

≥ 160

84

151

55.6

0.92 (0.63–1.36)

 

Serum potassium (mmol/l)a

< 2.5

56

110

50.9

0.67 (0.43–1.05)

< 0.001

 

2.5–3

302

535

56.4

0.93 (0.75–1.14)

 
 

3–3.5

1,106

2,008

55.1

0.91 (0.81–1.02)

 
 

3.5–5.5

4,639

8,297

55.9

Reference

 
 

5.5–6

1,137

1,858

61.2

1.17 (1.04–1.32)

 
 

6–7

1,244

2,028

61.3

1.13 (1.00–1.27)

 
 

≥ 7

394

740

53.2

0.79 (0.66–0.95)

 

Serum albumin (g/l)b

< 20

3,544

5,499

64.4

1.21 (1.11–1.33)

< 0.001

 

20–25

1,834

3,356

54.6

1.02 (0.93–1.13)

 
 

25–45

3,469

6,635

52.3

Reference

 
 

≥ 45

31

86

36.0

0.55 (0.33–0.93)

 

Haematocrit (%)a

< 20

612

1,008

60.7

0.99 (0.84–1.17)

0.011

 

20–30

4,748

8,536

55.6

0.89 (0.82–0.97)

 
 

30–46

3,168

5,473

57.9

Reference

 
 

46–50

218

335

65.1

1.28 (0.98–1.68)

 
 

≥ 50

132

224

58.9

0.99 (0.71–1.38)

 

White blood count (×1,000/mm3)a

< 1

176

223

78.9

2.52 (1.73–3.67)

< 0.001

 

1–3

506

680

74.4

1.77 (1.44–2.18)

 
 

3–15

3,862

7,468

51.7

Reference

 
 

15–20

1,756

3,071

57.2

1.11 (1.00–1.23)

 
 

20–40

2,278

3,681

61.9

1.21 (1.09–1.33)

 
 

≥ 40

300

453

66.2

1.16 (0.91–1.47)

 

Glasgow Coma Scale scored

3–4

1,596

2,019

79.0

1.07 (1.06–1.08) per decrease of 1 point

< 0.001

 

5–12

1,178

1,924

61.2

  
 

13–14

1,099

1,880

58.5

  
 

15

5,005

9,753

51.3

  
  1. All of the factors emerged as statistically significant (P < 0.005) in the multiple logistic regression analysis. Exclusions were as follows: readmissions within the same hospital stay; admissions with length of ICU stay < 8 hours; admissions of patients aged < 16 years; admissions missing age, sex, surgical status, temperature, mean arterial pressure, heart rate or respiratory rate. Admitted patients with missing values for any other physiology variables are assumed to be normal and are placed in the reference category. aCategories from APACHE II (reference category equivalent to zero APACHE II points) bCategories from APACHE III (reference category equivalent to zero APACHE III points). cPre-sedation values used for admissions sedated or paralyzed during the first 24 hours in ICU. A-aDO2, alveolar-arterial oxygen gradient; APACHE, Acute Physiology and Chronic Health Evaluation; CI, confidence interval; CPR, cardiopulmonary resuscitation; FiO2, fractional inspired oxygen; ICU, intensive care unit; OR, odds ratio.
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