Table 3.

Characteristics of study population by RIFLE classa

CharacteristicAll AKIRiskInjuryFailureP
n2344582107
Demographics
    age (yr; mean [95% CI])68.5 (66.6 to 70.4)63.6 (59.5 to 67.7)72.0 (69.3 to 74.7)67.1 (64.1 to 70.1)0.001
    male gender (%)176 (75.2)40 (88.9)62 (75.6)74 (69.2)0.036
    diabetes (%)60 (25.6)7 (15.6)23 (28)30 (28)0.476
    hypertension (%)137 (58.5)27 (60)57 (69.5)53 (49.5)0.040
    NSAID (%)30 (12.8)6 (13.3)13 (15.9)11 (10.3)0.521
    ACEI or ARB (%)45 (19.2)9 (20)23 (28)13 (12.1)0.023
Department of origin0.004
    direct ICU admission69 (29.5)20 (44.4)26 (31.7)23 (21.5)
    medical87 (37.2)14 (31.1)23 (28)50 (46.7)
    surgical65 (27.8)7 (15.6)31 (37.8)27 (25.2)
    transfer from other ICU13 (5.6)4 (8.9)2 (2.4)7 (6.5)
Baseline renal characteristics
    abnormal renal function (%)86 (36.8)13 (28.9)30 (36.6)43 (40.2)0.001
    proteinuria or microhematuria (%)16 (6.8)3 (6.7)6 (7.3)7 (6.5)0.977
Diagnosis of AKI
    serum creatinine (mg/dl; median [IQR])2 (2.0 to 3.0)1.8 (1.5 to 2.0)2 (2.0 to 2.0)3.2 (3.0 to 5.0)<0.001
    diuresis (ml/d; median [IQR])1100 (520 to 1760)1655 (1235 to 2075)1490 (958 to 1910)500 (100 to 1000)<0.001
    oliguria (%)44 (19.7)0 (0)0 (0)44 (45.4)<0.001
Associated abnormalities
    acid-base (%)130 (55.6)17 (37.8)47 (57.3)66 (61.7)0.02
    electrolytes (%)b128 (54.7)19 (42.2)43 (52.4)66 (61.7)0.08
    hepatic enzymes (%)76 (32.5)9 (20)27 (32.9)40 (37.4)0.11
    cardiac enzymes (%)64 (27.4)9 (20)25 (30.5)30 (28)0.44
    hypoalbuminemia (%)102 (43.6)13 (28.9)30 (36.6)59 (55.1)0.003
    hematologic (%)c115 (49.1)19 (42.2)38 (46.3)58 (54.2)0.33
    coagulation (%)87 (37.2)10 (22.2)31 (37.8)46 (43)0.053
Cause of AKI
    prerenal (%)89 (38.0)14 (31.1)49 (59.8)26 (24.3)<0.001
    sepsis (%)60 (25.6)9 (20)20 (24.4)31 (29)0.49
    ischemic ATN (%)34 (14.5)7 (15.6)10 (12.2)17 (15.9)0.76
    radiocontrast (%)1 (0.4)0 (0)0 (0)1 (0.9)
    nephrotoxic ATN other than contrast (%)13 (5.6)2 (4.4)4 (4.9)7 (6.5)0.83
    other (%)12 (5.1)2 (4.4)2 (2.4)8 (7.5)0.29
Treatment of AKI<0.001
    any RRT (%)71 (30.3)2 (4.4)15 (18.3)54 (50.5)
    no RRT (%)163 (69.7)43 (95.6)67 (81.7)53 (49.5)
RRT modality (% of those who needed RRT)0.96
    CRRT only (%)61 (85.9)2 (100)13 (86.7)46 (85.2)
    CRRT then IHD (%)0 (0)0 (0)0 (0)0 (0)
    IHD only (%)1 (1.4)0 (0)0 (0)1 (1.9)
    IHD then CRRT (%)9 (12.7)0 (0)2 (13.3)7 (13)
Outcome
    ICU mortality (%)85 (36.3)9 (20)24 (29.3)52 (49.5)0.001
    renal recovery at time of death or ICU discharge (%)84 (35.9)26 (57.8)36 (43.9)22 (20.6)<0.001
    length of stay (d; median [IQR])10 (3 to 24)10 (2 to 20)8 (3 to 23)12 (4 to 29)0.16
  • a RIFLE class was determined at time of AKI diagnosis. To convert serum creatinine from mg/dl to μmol/L, multiply by 88.4. ACEI, angiotensin-converting enzyme inhibitors; ARB, angiotensin II type 1 receptor blocker; ATN, acute tubular necrosis; CI, confidence interval; CRRT, continuous renal replacement therapy; IHD, intermittent hemodialysis; IQR, interquartile range; NSAID, nonsteroidal anti-inflammatory drug; RIFLE, risk–injury–failure–loss–ESRD; RRT, renal replacement therapy.

  • b Abnormalities in serum or plasma sodium, potassium, calcium, or phosphorus.

  • c Includes anemia, leukocytosis, leukopenia, and thrombocytopenia.