Acute kidney injury in traumatic brain injury intensive care unit patients

Table 1 Patient characteristics according to the Kidney Disease Improving Global Outcomes criteria (propensity score matching)

Characteristics	Total patients (n = 582)	Non-AKI (n = 291)	AKI (n = 291)	P value
Ethnicity				0.195
White	415 (71.3)	206 (70.8)	209 (71.8)
Hispanic/Latino	8 (1.4)	7 (2.4)	1 (0.3)
African American	22 (3.8)	13 (4.5)	9 (3.1)
Asian	3 (0.5)	2 (0.7)	1 (0.3)
Other/unknown	134 (23.0)	63 (21.7)	71 (24.4)
Age (yr)	55.3 ± 23.9	54.7 ± 24.7	55.8 ± 23.1	0.595
Sex				0.925
Female	152 (26.1)	75 (25.8)	77 (26.5)
Male	430 (73.9)	216 (74.2)	214 (73.5)
Elixhauser score	8.1 ± 11.5	7.4 ± 10.9	8.7 ± 12.1	0.187
SAPS II	34.8 ± 14.8	33.1 ± 13.4	36.6 ± 15.9	0.004
SOFA	4.4 ± 2.9	4.0 ± 2.7	4.8 ± 3.1	0.001
GCS	12.8 ± 3.2	12.8 ± 3.2	12.9 ± 3.3	0.778
Craniotomy	84 (14.4)	42 (14.4)	42 (14.4)	> 0.99
Peak SCr (µmol/L)	1.46 ± 0.72	1.22 ± 0.34	1.70 ± 0.90	< 0.001
SCr at admission (µmol/L)	1.19 ± 0.46	1.08 ± 0.27	1.29 ± 0.57	< 0.001
Use of antiplatelet drugs	40 (6.87)	16 (5.50)	24 (8.25)	0.251
Use of anticoagulants	13 (2.2)	5 (1.7)	8 (2.8)	0.575
Use of vancomycin	178 (30.6)	80 (27.5)	98 (33.7)	0.126
Use of ARB/ACE-I	34 (5.8)	19 (6.5)	15 (5.2)	0.596
Use of aminoglycosides	39 (6.7)	16 (5.5)	23 (7.9)	0.320
Transfusion (mL)	553 ± 1589	400 ± 1077	645 ± 1967	0.063
Red blood cell (mL)	276 ± 1109	174 ± 623	377 ± 1433	0.027
Plasma (mL)	232 ± 690	214 ± 646	250 ± 733	0.526
Shock	177 (30.4)	73 (25.1)	104 (35.7)	0.007
UO (mL)	0.68 ± 0.60	0.70 ± 0.44	0.67 ± 0.73	0.468

Data are shown as n (%) or mean ± SD. P values < 0.05 were considered statistically significant. KDIGO: Kidney Disease Improving Global Outcomes; PSM: Propensity score matching; AKI: Acute kidney injury; SAPS II: Simplified acute physiology score; SOFA: Sequential organ failure assessment; GCS: Glasgow coma scale; Scr: Serum creatinine; ARB: Angiotensin receptor blocker; ACE-I: Angiotensin-converting enzyme inhibitor; UO: Urine output.

Table 2 Patient characteristics by Kidney Disease Improving Global Outcomes stage before propensity score matching

Characteristics	Total patients (n = 1648)	Non-AKI (n = 1357)	AKI (n = 291)	P value
Ethnicity				0.070
White	1220 (74.0)	1011 (74.5)	209 (71.8)
Hispanic/Latino	20 (1.2)	19 (1.4)	1 (0.3)
African American	55 (3.3)	46 (3.4)	9 (3.1)
Asian	23 (1.4)	22 (1.6)	1 (0.3)
Other/unknown	330 (20.0)	259 (18.8)	71 (28.4)
Age (yr)	58.5 ± 22.5	59.0 ± 22.4	55.8 ± 22.1	0.025
Sex				0.001
Female	603 (36.6)	526 (38.8)	77 (26.5)
Male	1045 (63.4)	831 (61.2)	214 (73.5)
Elixhauser score	6.4 ± 10.2	5.9 ± 9.6	8.7 ± 12.1	< 0.001
SAPS II	31.9 ± 13.0	30.9 ± 12.0	36.6 ± 15.9	< 0.001
SOFA	3.3 ± 2.5	2.9 ± 2.2	4.8 ± 3.1	< 0.001
GCS	13.1 ± 2.9	13.1 ± 2.8	12.9 ± 3.3	0.096
Craniotomy	344 (20.9)	302 (22.3)	42 (14.4)	0.020
Peak SCr (µmol/L)	1.09 ± 0.53	0.96 ± 0.27	1.70 ± 0.90	< 0.001
SCr at admission (µmol/L)	0.95 ± 0.36	0.88 ± 0.23	1.29 ± 0.57	< 0.001
Use of antiplatelet drugs	138 (8.4)	114 (8.4)	24 (8.3)	0.932
Use of anticoagulants	31 (1.9)	23 (1.7)	8 (2.8)	0.235
Use of vancomycin	408 (24.8)	310 (22.8)	98 (33.7)	< 0.001
Use of ARB/ACE-I	84 (5.1)	69 (5.1)	15 (5.2)	0.961
Use of aminoglycosides	80 (4.9)	57 (4.2)	23 (7.9)	0.008
Transfusion (mL)	309 ± 1082	237 ± 752	645 ± 1967	0.001
Red blood cell (mL)	141 ± 710	93 ± 398	377 ± 1433	0.001
Plasma (mL)	158 ± 596	138 ± 560	250 ± 733	0.004
Shock	460 (27.9)	356 (26.2)	104 (35.7)	< 0.001
UO (mL)	0.80 ± 1.06	0.83 ± 1.12	0.67 ± 0.73	0.016

Data are shown as n (%) or mean ± SD. P values < 0.05 were considered statistically significant. KDIGO: Kidney Disease Improving Global Outcomes; PSM: Propensity score matching; AKI: Acute kidney injury; SAPS II: Simplified acute physiology score; SOFA: Sequential organ failure assessment; GCS: Glasgow coma scale; Scr: Serum creatinine; ARB: Angiotensin receptor blocker; ACE-I: Angiotensin-converting enzyme inhibitor; UO: Urine output.

Table 3 Patient characteristics by Kidney Disease Improving Global Outcomes stage

Characteristics	Stage 1 (n = 200)	Stage 2 (n = 53)	Stage 3 (n = 38)	P value
Ethnicity				0.512
White	141 (70.5)	39 (73.6)	29 (76.3)
Hispanic/Latino	1 (0.5)	0	0
African American	5 (2.5)	3 (5.7)	1 (2.6)
Asian	1 (0.5)	0	0
Other/unknown	52 (26.0)	11 (20.8)	8 (21.1)
Age (yr)	53.4 ± 23.1	64.6 ± 20.4	55.8 ± 23.9	0.001
Sex				< 0.001
Female	42 (21.0)	23 (43.4)	12 (31.6)
Male	158 (79.0)	30 (56.6)	26 (68.4)
Elixhauser score	8.2 ± 12.5	8.9 ± 9.9	11.1 ± 12.9	< 0.001
SAPS II	35.1 ± 16.0	39.2 ± 12.8	40.6 ± 18.1	< 0.001
SOFA	4.6 ± 2.9	4.6 ± 2.9	6.3 ± 4.0	< 0.001
GCS	12.9 ± 3.3	12.9 ± 3.2	12.7 ± 3.8	0.582
Craniotomy	28 (14.0)	7 (13.2)	7 (18.4)	0.025
Max creatinine (µmol/L)	1.49 ± 0.44	1.70 ± 1.03	2.81 ± 1.54	< 0.001
Creatinine at admission (µmol/L)	1.24 ± 0.34	1.22 ± 0.57	1.67 ± 1.14	< 0.001
Use of antiplatelet drugs	94 (9.8)	20 (13.2)	10 (13.0)	0.890
Use of anticoagulant	21 (2.2)	8 (5.3)	5 (6.49)	0.281
Use of vancomycin	74 (37.0)	14 (26.4)	10 (26.32)	< 0.001
Use of ARB/ACE-I	9 (4.5)	5 (9.4)	1 (2.63)	0.443
Use of aminoglycosides	14 (7.0)	5 (9.4)	4 (10.53)	0.040
Transfusion (mL)	537 ± 1081	500 ± 1210	1412 ± 4613	< 0.001
Red blood cell (mL)	291 ± 692	274 ± 920	974 ± 3451	< 0.001
Plasma (mL)	231 ± 666	213 ± 606	400 ± 1133	0.010
Shock	460 (26.9)	356 (26.2)	104 (35.74)	0.004
UO (mL)	0.70 ± 0.80	0.62 ± 0.47	0.53 ± 0.58	0.080

Data are shown as n (%) or mean ± SD. P values < 0.05 were considered statistically significant. KDIGO: Kidney Disease Improving Global Outcomes; PSM: Propensity score matching; AKI: Acute kidney injury; SAPS II: Simplified acute physiology score; SOFA: Sequential organ failure assessment; GCS: Glasgow coma scale; Scr: Serum creatinine; ARB: Angiotensin receptor blocker; ACE-I: Angiotensin-converting enzyme inhibitor; UO: Urine output.

Table 4 Stages of acute kidney injury according to each classification

Stages, n (%)	KDIGO	AKIN	RIFLE	CK	P value
Stage 0	1357 (82.3)	1365 (82.9)	1439 (87.3)	1458 (88.5)	0.967
Stage 1	200 (12.1)	199 (12.1)	118 (7.2)	103 (6.3)	0.370
Stage 2	53 (3.2)	49 (3.0)	57 (3.5)	51 (3.1)	0.998
Stage 3	38 (2.3)	34 (2.1)	34 (2.1)	35 (2.1)	> 0.99

Stage 0 is considered as no-acute kidney injury. Data are shown as n (%) or mean ± SD. P values < 0.05 were considered statistically significant. KDIGO: Kidney Disease Improving Global Outcomes; AKIN: Acute Kidney Injury Network; RIFLE: Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease; CK: Creatinine kinetics.

Table 5 Overlap of classification systems

KDIGO definition	Compared criteria	AKI Stage by RIFLE, AKIN, or CK
		Stage 0, n (%)	R/Stage1, n (%)	I/Stage 2, n (%)	F/Stage 3, n (%)
Stage 0	RIFLE	1348 (99.3)	9 (0.1)	0	0
Stage 1		126 (63.0)	72 (36.0)	2 (1.0)	0
Stage 2		31 (58.5)	2 (3.8)	19 (35.9)	1 (1.9)
Stage 3		14 (36.8)	2 (5.3)	4 (10.5)	18 (47.4)
Stage 0	AKIN	1344 (99.1)	12 (0.9)	0	0
Stage 1		17 (8.5)	183 (91.5)	0	0
Stage 2		2 (3.8)	3 (5.7)	48 (90.6)	0
Stage 3		2 (5.3)	1 (2.6)	1 (2.6)	34 (89.5)
Stage 0	CK	1346 (99.3)	5 (0.4)	2 (0.2)	3 (0.2)
Stage 1		66 (33.0)	89 (44.5)	40 (20.0)	5 (2.5)
Stage 2		31 (58.5)	3 (5.7)	6 (11.3)	13 (24.5)
Stage 3		15 (39.5)	6 (15.8)	3 (7.9)	14 (36.8)

Stage 0 is considered no Acute Kidney Injury. Stage 1 is at risk. Stage 2 is injury. Stage 3 is failure. KDIGO: Kidney Disease Improving Global Outcomes; AKIN: Acute Kidney Injury Network; RIFLE: Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease; CK: Creatinine kinetics.

Table 6 Prognosis-related indicators in patients

Indicators	Non-AKI	AKI			P value
	Stage 0 n = 291	Stage 1 n = 200	Stage 2 n = 53	Stage 3 n = 38
Ventilation (h)	105.5 ± 132.4	135.4 ± 149.8	138.7 ± 206.7	149.1 ± 207.1	0.029
ICU duration (d)	4.7 ± 5.8	6.5 ± 7.4	5.6 ± 9.1	6.3 ± 9.2	0.001
Hospitalization (d)	10.8 ± 11.0	13.9 ± 14.6	12.6 ± 13.1	12.4 ± 10.2	0.008
Hospital mortality	185 (12.9)	38 (19.0)	14 (26.4)	17 (44.7)	0.001
30-d mortality	202 (14.9)	42 (21.0)	14 (26.4)	17 (44.7)	< 0.001
1-yr mortality	316 (23.3)	51 (25.5)	17 (32.1)	21 (55.3)	< 0.001

Data are shown as n (%) or mean ± SD. P values < 0.05 were considered statistically significant. Acute kidney injury and its stage were diagnosed by the Kidney Disease Improving Global Outcomes criteria. AKI: Acute kidney injury; ICU: Intensive care unit.

Table 7 Association between in-hospital mortality and the acute kidney injury stages in diagnosed by Creatinine kinetics, “Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease”, Acute Kidney Injury Network, and Kidney Disease Improving Global Outcomes

Variables		Univariable analysis		Multivariable analysis
		Odds ratio (95%CI)	P value	Odds ratio (95%CI)	P value
KDIGO	Stage 1	1.64 (1.11-2.41)	0.013	0.70 (0.27-1.83)	0.635
	Stage 2	2.51 (1.33-4.71)	0.004	0.15 (0.00-4.76)	0.242
	Stage 3	5.65 (2.92-10.93)	< 0.001	0.10 (0.00-7.83)	0.705
RIFLE	Stage 1	1.86 (1.16, 2.96)	0.010	0.97 (0.39-2.43)	0.879
	Stage 2	2.70 (1.48-4.90)	0.001	3.26 (0.18-59.43)	0.166
	Stage 3	6.14 (3.08-12.25)	< 0.001	1.90 (0.07-49.94)	0.466
AKIN	Stage 1	1.77 (1.21-2.59)	0.004	1.32 (0.39-4.40)	0.933
	Stage 2	2.54 (1.32-4.88)	0.005	3.23 (0.33-31.98)	0.552
	Stage 3	6.25 (3.13-12.49)	< 0.001	16.88 (0.74-349.18)	0.403
CK	Stage 1	1.49 (0.89-2.51)	0.132	1.34 (0.44-4.83)	0.500
	Stage 2	2.49 (1.32-4.70)	0.005	1.07 (0.35-3.25)	0.579
	Stage 3	4.40 (2.20-8.79)	< 0.001	0.72 (0.17-2.98)	0.615

ORs are adjusted for ethnicity, age, sex, Elixhauser score, simplified acute physiology score, SOFA, Glasgow Coma Scale, craniotomy, max creatinine, creatinine at admission, use of antiplatelet drugs, anticoagulant, vancomycin, angiotensin receptor blocker/angiotensin-converting enzyme inhibitor and aminoglycosides, transfusion, red blood cell, plasma and shock. P values < 0.05 were considered statistically significant. KDIGO: Kidney Disease Improving Global Outcomes; AKIN: Acute Kidney Injury Network; RIFLE: Risk, Injury, Failure, Loss of kidney function, and End-stage kidney disease; CK: Creatinine kinetics; CI: Confidence interval.