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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.