Incidence and Burden of Acute Kidney Injury among Traumatic Brain-Injury Patients

Figures & data

Figure 1 Flowchart of patient inclusion.

Table 1 Baseline characteristics of TBI patients with and without AKI

	Overall (n=419)	Non-AKI (n=336, 80.2%)	AKI (n=83, 19.8%)	p
Age (years)	43 (25–57)	41 (24–54)	47 (36–60)	0.004
Male sex	320 (76.4%)	253 (75.3%)	67 (80.7%)	0.289
Injury cause				0.006
Motor-vehicle accident	262 (62.5%)	205 (61.0%)	57 (68.7%)
Fall	84 (20.0%)	67 (19.9%)	17 (20.5%)
Stumble	46 (11.0%)	37 (11.0%)	9 (10.8%)
Other	27 (6.4%)	27 (8.0%)	0
Vital signs on admission
Systolic blood pressure (mmHg)	120 (106–138)	121 (106–138)	118 (103–144)	0.400
Diastolic blood pressure (mmHg)	72±16.51	73±15.29	69±20.46	0.074
Heart rate (bpm)	100 (81–120)	98 (80–118)	104 (86–124)	0.120
Body temperature (°C)	36.7 (36.5–37.0)	36.7 (36.5–37.0)	36.8 (36.3–37.1)	0.681
Anisocoria	116 (27.7%)	96 (28.6%)	20 (24.1%)	0.409
GCS	6 (5–9)	6 (5–10)	5 (4–6)	<0.001
ISS	25 (16–25)	22 (13–25)	25 (16–29)	<0.001
Laboratory tests
Glucose (mmol/L)	9.64 (7.04–13.16)	8.97 (6.64–12.50)	12.24 (9.00–17.15)	<0.001
Platelets (10^9/L)	105 (68–165)	116 (74–176)	74 (45–111)	<0.001
Hemoglobin (g/L)	90 (76–110)	94 (78–112)	80 (72–90)	<0.001
Serum creatinine (µmol/L)	71 (53–96)	65 (49–83)	128 (86–209)	<0.001
Radiology
Epidural hematoma	43 (10.3%)	38 (11.3%)	5 (6.0%)	0.133
Subdural hematoma	101 (24.1%)	78 (23.2%)	23 (27.7%)	0.397
Subarachnoid hemorrhage	230 (54.9%)	184 (54.8%)	46 (55.4%)	0.914
Diffuse axonal injury	103 (24.6%)	76 (22.6%)	27 (32.5%)	0.067
AKI-related variables
Initial day of AKI development	0	—	1 (1–2)	<0.001
AKI duration	0	—	1 (1–3)	<0.001
Highest AKI stage	0	—	2 (1–3)	<0.001
AKI burden	0	—	2 (1–6)	<0.001
Mortality	205 (48.9%)	135 (40.2%)	70 (84.3%)	<0.001
Length of ICU stay (days)	3 (1–3)	4 (1–18)	2 (1–11)	0.997
Length of hospital stay (days)	12 (5–12)	15 (5–31)	7 (3–14)	<0.001

Abbreviations: AKI, acute kidney injury; GCS, Glasgow coma scale; ISS, injury- severity score.

Figure 2 (A) Initial day of AKI development during hospitalization in TBI patients. This was principally on the first day (10.74%). (B) Distribution of AKI duration during hospitalization in TBI patients, most commonly 1 day (10%). (C) Distribution of highest AKI stage during hospitalization in TBI patients. Stage 1, 2, and 3 AKI incidence was 9.79%, 3.34%, and 6.68%, respectively. (D) Distribution of AKI burden during hospitalization in TBI patients, most commonly stage 1 (7.2%).

Table 2 Univariate logistic regression analysis for risk factors of mortality in TBI patients

	OR	95% Cl	p
Age (years)	1.004	0.995–1.013	0.403
Male sex	0.873	0.556–1.371	0.556
Injury cause			0.017
Motor-vehicle accident	1	Reference
Fall	0.584	0.354–0.961	0.034
Stumble	0.858	0.458–1.606	0.632
Other	0.300	0.123–0.735	0.008
Systolic blood pressure (mmHg)	0.993	0.986–1.001	0.080
Diastolic blood pressure (mmHg)	0.989	0.978–1.001	0.071
Heart rate (bpm)	1.013	1.006–1.021	<0.001
Body temperature (°C)	0.825	0.661–1.030	0.089
Anisocoria	0.689	0.447–1.061	0.091
GCS	0.597	0.533–0.668	<0.001
ISS	1.108	1.080–1.136	<0.001
Glucose (mmol/L)	1.279	1.204–1.358	<0.001
Platelets (10^9/L)	0.991	0.988–0.994	<0.001
Hemoglobin (g/L)	0.975	0.967–0.984	<0.001
Serum creatinine (µmol/L)	1.013	1.007–1.018	<0.001
Epidural hematoma	0.898	0.477–1.690	0.738
Subdural hematoma	2.886	1.796–4.637	<0.001
Subarachnoid hemorrhage	1.825	1.236–2.695	0.002
Diffuse axonal injury	1.829	1.164–2.876	0.009

Abbreviations: GCS, Glasgow Coma Scale; ISS, injury-severity score.

Table 3 Characteristics of AKI-related variables and their association with mortality on univariate and multivariate logistic regression analysis

	Univariate			Multivariate
	OR	95% CI	p	OR	95% CI	p
AKI occurrence	8.017	4.266–15.065	<0.001	3.792	1.540–9.341	0.004
AKI duration	1.512	1.187–1.926	0.001	1.083	0.957–1.225	0.206
Highest AKI stage	3.307	2.166–5.049	<0.001	3.122	1.669–5.837	<0.001
AKI burden	1.261	1.099–1.447	0.001	1.062	0.974–1.158	0.171

Note: Multivariate logistic regression adjusted for GCS, ISS, injury cause, heart rate, glucose, platelets, hemoglobin, serum creatinine, subdural hematoma, subarachnoid hemorrhage, and diffuse axonal injury.

Figure 3 (A) Mortality comparison of TBI patients grouped by AKI occurrence. (B) Mortality comparison of included TBI grouped by AKI duration. Bonferroni corrected α was 0.05/3 (p=0.0167). (C) Mortality comparison of TBI patients grouped by the highest AKI stage. Bonferroni corrected α was 0.05/6 (p=0.0083). (D) Mortality comparison of TBI patients grouped by AKI burden. Bonferroni corrected α was 0.05/3 (p=0.0167).

Table 4 Predictive value of single lactate and the logistic model

	AUC	95% CI	Sensitivity	Specificity
AKI occurrence	0.640	0.587–0.694	0.341	0.939
AKI duration	0.643	0.590–0.696	0.341	0.939
Highest AKI stage	0.643	0.590–0.696	0.341	0.939
AKI burden	0.644	0.591–0.697	0.341	0.939
Model 1	0.860	0.825–0.895	0.858	0.724
Model 2	0.880	0.848–0.912	0.912	0.720
Model 3	0.885	0.854–0.916	0.907	0.720

Notes: Model 1 composed of GCS, glucose, and SDH; model 2 composed of GCS, glucose, SDH, and AKI; model 3 composed of GCS, glucose, SDH, and highest AKI stage.

Figure 4 Receiver-operating characteristic curve of multivariate logistic models incorporating AKI-related variables for predicting mortality of TBI patients. Model 1 was composed of GCS, glucose, and SDH, with AUC of 0.860. Model 2 was composed of GCS, glucose, SDH, and AKI, with AUC of 0.880. Model 3 was composed of GCS, glucose, SDH, and highest AKI stage, with AUC of 0.885.