Table 2.

Characteristics of the study population by hazard tier (tranche)

VariableAllHazard Tier 1: Very High RiskHazard Tier 2: High RiskHazard Tier 3: Moderate RiskReference Tier: Low RiskP Value
N50610420615244
Age (yr)66 (52–76)68 (53–76)70 (58–77)64 (49–76)47 (26–59)<0.001
Men301 (59.5)58 (55.8)119 (57.8)96 (63.2)28 (63.6)0.57
BMI (kg/m2)21.5 (19.3–24.1)21.9 (18.8–24.1)21.2 (19.1–24.1)21.3 (19.7–24.3)20.8 (19.4–22.4)0.46
SAPS II43 (35–53)48 (40–59)44 (37–55)41 (32–49)34 (28–41)<0.001
SOFA5 (3–7)8 (7–10)5 (3–7)4 (2–5)3 (2–5)<0.001
APACHE II18 (13–22)20 (16–26)18 (14–23)15 (11–20)12 (7–16)<0.001
Serum creatinine, admission (mg/dl)0.9 (0.7–1.2)1.1 (0.8–1.4)0.9 (0.7–1.2)0.9 (0.7–1.2)0.8 (0.6–1.0)<0.001
Urine output, ICU day 1 (ml/kg per hour)1.2 (0.7–1.9)1.3 (0.7–2.1)1.2 (0.8–1.8)1.2 (0.8–1.8)1.5 (1.2–2.2)0.14
Chronic major risk factors
 Age>70 yr215 (42.5)48 (46.2)108 (52.4)59 (38.8)0 (0)<0.001
 Diabetes92 (18.2)23 (22.1)48 (23.3)21 (13.8)0 (0)0.001
 Cardiovascular disease48 (9.5)8 (7.7)23 (11.2)16 (10.5)1 (2.3)0.27
 CKD31 (6.1)11 (10.6)11 (5.3)9 (5.9)0 (0)0.08
Chronic minor risk factors
 Hypertension228 (45.1)46 (44.2)117 (56.8)59 (38.8)6 (13.6)<0.001
 BMI>30 kg/m234 (6.7)4 (3.8)17 (8.3)13 (8.6)0 (0)0.11
 Bilirubin>2 mg/dl41 (8.1)9 (8.7)22 (10.7)8 (5.3)2 (4.5)0.23
 Cerebrovascular accident216 (42.7)49 (47.1)99 (48.1)58 (38.2)10 (22.7)0.01
 AIDS3 (0.6)2 (1.9)0 (0)1 (1)0 (0)0.20
 Cancer52 (10.3)9 (8.7)23 (11.2)19 (12.5)1 (2.3)0.23
Acute risk factors
 Hypotension162 (32)104 (100)51 (24.8)7 (4.6)0 (0)<0.001
 Vasoactive therapy112 (22.1)104 (100)7 (3.4)1 (0.7)0 (0)<0.001
 Sepsis129 (25.5)37 (35.6)79 (38.3)13 (8.6)0 (0)<0.001
 Mechanical ventilation380 (75.1)98 (94.2)156 (75.7)99 (65.1)27 (61.4)<0.001
 High-risk surgery171 (33.8)46 (44.2)92 (44.7)33 (21.7)0 (0)<0.001
 Nephrotoxin exposure134 (26.5)38 (36.5)88 (42.7)8 (5.3)0 (0)<0.001
ICU outcomes
 Early Cr elevation (%)214 (42.3)94 (90.4)77 (37.4)43 (28.3)0 (0)<0.001
 Severe AKI (%)59 (11.7)21 (20.2)26 (12.6)10 (6.6)2 (4.5)0.004
 RRT (%)36 (7.1)11 (10.6)17 (8.3)6 (3.9)2 (4.5)0.17
 Mortality (%)105 (20.8)42 (40.4)39 (18.9)21 (13.8)3 (6.8)<0.001
 Severe AKI or death129 (25.5)50 (48.1)50 (24.3)25 (16.4)4 (9.1)<0.001
 Length of ICU stay (d)6 (3–14)7 (4–14)7 (3–16)5 (2–14)4 (2–7)0.003
  • Categorical variables are expressed as n (%). Continuous variables are expressed as median (interquartile range). BMI, body mass index; SAPS II, Simplified Acute Physiology Score II; SOFA, Sequential Organ Failure Assessment; APACHE II, Acute Physiology and Chronic Health Evaluation I; ICU, intensive care unit; RRT, renal replacement therapy.