Impact of Mild Acute Kidney Injury (AKI) on Outcome after Open Repair of Aortic Aneurysms

Figures & data

Table 1 Demographic and clinical characteristics of the overall population (n = 77)

Variable	Result
Age (years)	68.4 ± 9.7
Gender (M/F)	64/13
Weight (Kg)	69.2 ± 13.3
Hypertension (%)	83%
DM (%)	10%
CAD (%)	46.7%
Baseline SCr (mg/dL)	1.47 ± 1.18
Baseline GFR (mL/min)	58.6 ± 28.9
CRF (%)	32.5%
Thoraco-abdominal aneurysm (%)	10%
Maximal diameter (cm)	6.47 ± 1.36

Abbreviations: DM = diabetes mellitus, CAD = coronary artery disease, SCr = serum creatinine, GFR = calculated glomerular filtration rate, CRF = chronic renal failure.

Table 2 Outcomes of the overall population (n =  77)

Variable	Result
Overall mortality (%)	21 (27.3%)
Mortality of supra-renal aortic cross-clamping (%)	11 (42.8%)
Mortality without supra-renal clamping (%)	10 (21.4%)
AKI, increase ≥25% SCr (%)	44 (57%)
AKI, increase ≥%50 SCr (%)	37 (48%)
AKI, decrease ≥25% GFR (%)	26 (33.7%)
RRT (%)	10 (12.9%)
Duration of operation (min)	350 [IQ 220–480]
Supra-renal aortic cross-clamping (%)	19 (24.6%)
Time of supra-renal clamping (min)	33 [IQ 20–42]
Time of infra-renal clamping (min)	55 [IQ 42–68]
IOP transfusion (%)	51 (66.3%)
PO infection (%)	31 (46.2%)
Length of ICU stay (days)	5.2 ± 3.9
Length of hospital stay (days)	21.2 ± 17.5

Abbreviations: AKI = acute kidney injury, SCr = serum creatinine, RRT = renal replacement therapy, IOP = intraoperative, PO = post-operative, ICU = intensive care unit.

Table 3 Demographic and clinical characteristics of the patients that developed AKI 50% compared to controls

Variable	AKI 50% (n = 26)	Control (n = 51)	p
Age (years)	71 ± 7	67 ± 11	.143
Gender (M/F)	21/3	42/9	.741
Baseline SCr (mg/dL)	1.43 ± 0.54	1.49 ± 1.39	.307
Baseline GFR (mL/min)	54.0 ± 28.8	60.9 ± 28.9	.207
Maximal diameter of aneurysm (cm)	6.7 ± 1.6	6.3 ± 1.2	.465
DM (%)	3 (11.5%)	5 (9.8%)	1
CRF (%)	10 (38%)	15 (29.4%)	.423
Hypertension (%)	22 (84%)	42 (82%)	1
CAD (%)	11 (42%)	25 (49%)	.577

Abbreviation: SCr = serum creatinine, GFR = calculated glomerular filtration rate, DM = diabetes mellitus, CRF = chronic renal failure, CAD = coronary artery disease.

Table 4 Comparison between AKI 50% and controls regarding perioperative variables (intra-operative [IOP] and immediate post-operative [POI])

Variable	AKI 50%(n = 26)	Control(n = 51)	p
IOP hypotension (%)	14 (53.8%)	27 (64.2%)	.940
Minimal MAP IOP (mmHg)	63.8 ± 11.1	64.2 ± 13.5	.632
Vasoactive drug IOP (%)	12 (46.1%)	8 (15.6%)	.004
Length of operation (min)	435 [IQ 255–600]	320 [IQ 208–360]	.001
Supra-renal aortic cross-clamping (%)	14 (53%)	5 (9.8%)	.001
Time of supra-renal clamping (min)	30 [IQ 13–30]	32 [IQ 20–35]	.782
Time of infra-renal clamping (min)	57 [IQ 28–60]	55 [IQ 33–56]	.759
Transfusion IOP (%)	22 (84.6%)	29 (56.8%)	.015
Urine output IOP (mL/min)	2.42 ± 1.55	3.17 ± 1.51	.047
Rate of volume infusion IOP (mL/min)	13.84 ± 4.08	16.24 ± 4.52	.026
Net fluid balance IOP (mL/min)	11.42 ± 4.06	13.06 ± 4.35	.113
Urine output POI (mL/min)	1.58 ± 1.20	1.97 ± 1.18	.159
Net fluid balance (mL/min)	1.39 ± 1.52	0.40 ± 1.36	.005
Lactate POI (mg/dL)	29.2 ± 16.0	21.9 ± 9.8	.072
BE POI	−6.91 ± 3.27	−6.30 ± 3.39	.452
HB POI (g/dL)	12.6 ± 1.6	11.6 ± 1.5	.007
Platelet POI (×10^3/μL)	137 ± 37	187 ± 64	.001
Maximal glucose POI (mg/dL)	202 ± 90	160 ± 80	.004

Abbreviations: IOP = intra-operative, POI = immediate post-operative period, BE = base excess, Hb = hemoglobin.

Table 5 Clinical data of the first two post-operative days comparing AKI 50% patients to controls

Variable	AKI 50%(n = 25)	Control(n = 51)	p
Hypotension (%)	8 (32%)	11 (21.5%)	.324
Minimal MAP (mmHg)	72.8 ± 10.6	77.7 ± 12.6	.050
Vasoactive drug (%)	13 (52%)	8 (15.7%)	.001
Urine output 1^st PO (mL/min)	0.98 ± 0.63	1.60 ± 0.68	.001
Rate of volume infusion 1^st PO (mL/min)	2.54 ± 0.97	2.79 ± 2.63	.477
Net fluid balance 1^st PO (mL/min)	1.37 ± 0.98	0.64 ± 1.35	.005
Lactate 1st PO (mg/dL)	25.8 ± 11.8	22.9 ± 9.6	.472
BE 1^st PO	−5.94 ± 3.80	−4.64 ± 2.77	.118
HB 1^st PO (g/dL)	10.8 ± 1.5	10.9 ± 1.9	.790
Platelet 1^st PO (x10^3/μL)	117 ± 37	141 ± 51	.038
Maximal glucose 1st PO (mg/dL)	184 ± 77	143 ± 44	.006
Maximal CK level (U/L)	974 (236–2700)	463 (188–1479)	.005
Serum albumin (g/dL)	2.06 ± 0.41	2.40 ± 0.41	.007

Abbreviations: MAP = mean arterial pressure, BE = base excess, HB = hemoglobin, CK = creatine phosphokinase.

Table 6 Regression analysis of the risk factors for AKI 50%

Variable	OR (95% CI)	p
Supra-renal aortic cross-clamping	7.31 (1.66–32.11)	.008
Need for vasoactive drugs in the perioperative period	6.13 (1.65–22.85)	.005
Duration of the operation longer than 383 min	7.16 (1.70–30.32)	.007

Abbreviation: OR (95% CI) = odds ratio (95% confidence interval).

Figure 1. Probability of AKI 50% after aortic aneurysm open repair according to the regression analysis model. Abbreviations: SUPRA = need of supra-renal aortic cross-clamping, VAD = use of vasoactive drugs during peri-operative period.

Table 7 Demographic and clinical characteristics comparing survivors and non-survivors after aortic aneurysm open repair

Variable	Non-survivors(n = 21)	Survivors(n = 56)	p
Age (years)	70.8 ± 7.3	67.5 ± 10.4	.271
Gender (M/F)	18/3	46/10
Baseline SCr (mg/dL)	1.61 ± 0.65	1.41 ± 1.32	.297
Baseline GFR(mL/min)	45.9 ± 19.2	63.4 ± 30.5	.009
Maximal diameter (cm)	6.58 ± 1.23	6.43 ± 1.40	.386
DM (%)	2 (9%)	6 (11%)	1
CRF (%)	12 (57%)	13 (23%)	.005
Hypertension (%)	20 (95%)	44 (78.5%)	.161
CAD (%)	13 (62%)	23 (41%)	.103

Abbreviations: SCr = serum creatinine, GFR = calculated glomerular filtration rate, DM = diabetes mellitus, CRF = chronic renal failure, CAD = coronary artery disease.

Figure 2. Outcomes (AKI 25%, AKI 50%, and mortality rate) after aortic aneurysm open repair according to the level of aortic cross-clamping.

Table 8 Comparison of peri-operative (within 48 h after operation) variables between survivors and non-survivors

Variable	Non-survivors(n = 21)	Survivors (n = 56)	p
IOP hypotension (%)	15 (71.4%)	26 (46.4%)	.05
Minimal IOP MAP (mmHg)	58.5 ± 10.0	66.1 ± 12.9	.003
Need of VAD (%)	16 (71.2%)	12 (21.5%)	.001
Duration ofoperation (min)	420 [IQ 244–500]	330 [IQ 207–380]	.002
Transfusion (%)	20 (95%)	31 (55%)	.001
Supra-renal aortic cross-clamping (%)	11 (52%)	8 (14%)	.001
UV IOP (mL/min)	2.19 ± 1.55	3.19 ± 1.48	.011
Net fluid balance POI (ml)	1,268 ± 1,467	400 ± 1,095	.006
Lactate 1^st PO (mg/dL)	30.8 ± 10.5	20.5 ± 8.5	.006
BE 1^st PO	−5.66 ± 4.15	−4.86 ± 2.76	.419
Hb 1^st PO (g/dL)	10.9 ± 1.9	10.8 ± 1.6	.851
Platelets 1^st PO (×10^3/μL)	99 ± 33	146 ± 47	.001
Glucose (mg/dL)	188 ± 138	127 ± 73	.036
Serum albumin (g/dL)	2.02 ± 0.27	2.41 ± 0.46	.001

Abbreviations: IOP = intra-operative, VAD = vasoactive drugs, UV = urinary volume, BE = base excess, Hb = hemoglobin.

Figure 3. Mortality after aortic aneurysm open repair according to AKI definitions, compared to controls. Legend: AKI 25% vs. control, p = 0.121; AKI GFR 25% vs. control, p = 0.012; AKI 50% vs. control, p = 0.001; dialysis vs. control, p = 0.0001.

Figure 4. Hospital mortality and change in serum creatinine within 48 h after aortic surgery. Legend: Distribution of Δ serum creatinine and mortality rates calculated for serum creatinine intervals. Bars represent the number of patients in each interval. Broken line represents tendency of death with Δ serum creatinine elevation.

Table 9 Regression analysis for risk of mortality after aortic aneurysm open repair

Variable	OR (95% CI)	p
AKI 50%	8.84 (1.32–59.4)	.025
Need for a supra-renal aortic cross-clamping	9.67 (1.38–67.88)	.022
Baseline GFR <49 mL/min	17.07 (2.01–145.23)	.009
Glucose levels higher than 118 mg/dL post-operatively	19.99 (2.32–172.29)	.006

Abbreviations: AKI = acute kidney injury, GFR = calculated glomerular filtration rate, OR (95% CI) = odds ratio (95% confidence interval).