Acute kidney injury in intensive care unit patients: a comparison between the RIFLE and the Acute Kidney Injury Network classifications

Table 4 Patient baseline characteristics and the Risk, Injury, Failure, Loss of Kidney Function, End-stage Kidney Disease (RIFLE) criteria

Variable	No acute kidney injury (n = 372)	Risk (n = 97)	Injury (n = 73)	Failure (n = 120)	P value
Mean age (years)	55 ± 19	64 ± 18	63 ± 15	61 ± 16	< 0.0001
Male (%)	55.6	65.9	63	62.5	0.252
Caucasian (%)	93	91.7	91.8	92.5	1.000
History of cardiovascular disease^a (%)	48.4	63.9	61.6	54.2	0.023
Medical admission (%)	71.8	78.4	80.8	86.7	0.008
Sepsis^b (%)	26.6	39.2	61.6	74.2	< 0.0001
Baseline serum creatinine (μmol/l)^c	86 ± 24	100 ± 42	107 ± 26	123 ± 50	< 0.0001
Simplified Acute Physiology Score version II^d	40 ± 15	48 ± 15	51 ± 18	62 ± 21	< 0.0001
Vasopressors (%)	21.5	48.5	63	76.7	< 0.0001
Need for mechanical ventilation (%)	83.6	85.6	86.3	86.7	1.000
Urine output (l)^e	2.2 ± 0.9	0.5 ± 0.2	0.9 ± 0.5	1.4 ± 1.1
Serum creatinine at maximum RIFLE		162 ± 35	235 ± 32	395 ± 54
Need for renal replacement therapy
% of patients		2	12.3	56.7	< 0.0001
Mean time (days)	5 ± 2	10 ± 8	9 ± 7	0.599
Mean length of stay (days)	7 ± 8	8 ± 6	9 ± 10	11 ± 12	0.009
Mortality	11	30.9	32.8	55	< 0.0001
Complete renal function recovery^f	74.6	73.5	55.6	0.053

^aAangina pectoris, myocardial infarction, cerebrovascular disease, and diabetes mellitus. ^bDefined in accordance with the American College of Chest Physicians and the Society of Critical Care Medicine consensus [15]. ^cEstimated by the Modification of Diet in Renal Disease equation [14], assuming a lower limit of the normal baseline glomerular filtration rate of 75 ml/min/1.73 m². ^dCalculated based on the worst variables recorded during the first 24 hours of admission [16]. ^eAt maximum RIFLE (6-hour urine output for risk, 12-hour urine output for injury, and 24-hour urine output for failure). ^fIf the patient returned to their baseline classification within the RIFLE criteria [2].

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