Incidence, Risk Factors, and Prediction of Acute Kidney Injury After Off-Pump Coronary Artery Bypass Grafting

Figures & data

Table 1. Baseline characteristics of patients who underwent isolated first off-pump coronary artery bypass graft surgery

Characteristic	All patients (n = 448)
Age (years)	65 (59–70)
Female [n (%)]	118 (26.3)
Body mass index (kg/m^2)	24.5 (23.0–26.3)
Smoking [n (%)]	133 (29.7)
Systolic blood pressure (mmHg)	128 ± 19
Diastolic blood pressure (mmHg)	72 ± 11
Diabetes mellitus [n (%)]	201 (44.9)
Cerebrovascular accident [n (%)]	83 (18.5)
Peripheral artery occlusive disease [n (%)]	23 (5.1)
Chronic obstructive pulmonary disease [n (%)]	37 (8.3)
Preoperative GFR (mL/min/1.73 m^2)	72 ± 19
Recent myocardial infarction [n (%)]	28 (6.3)
Intra-aortic balloon pump prior to surgery [n (%)]	2 (0.4)
Preoperative inotropics [n (%)]	5 (1.1)
Coronary arteries with ≥50% stenosis
1 vessel [n (%)]	24 (5.4)
2 vessels [n (%)]	83 (18.5)
3 vessels [n (%)]	320 (71.4)
^aLeft ventricular ejection fraction
≥55 [n (%)]	318 (72.3)
45≤ <55 [n (%)]	64 (14.5)
35≤ <45 [n (%)]	40 (9.1)
<35 [n (%)]	18 (4.1)
Coronary angiography ≤7 days [n (%)]	302 (67.4%)

Notes: GFR, glomerular filtration rate.

^aData on preoperative ejection fraction were not available for eight patients.

Table 2. Univariate analysis of acute kidney injury following isolated first off-pump coronary artery bypass graft surgery

Characteristic	No AKI (n = 414)	AKI (n = 34)	OR (95% CI)	p-Value
Age (years)	65 (58–70)	67 (60–73)	1.03 (0.99–1.08)	0.141
Female [n (%)]	110 (26.6)	8 (23.5)	1.18 (0.52–2.68)	0.699
BMI >25 kg/m^2 [n (%)]	170 (41.1)	16 (47.1)	1.28 (0.63–2.57)	0.496
SBP (per 20 mmHg)	127 ± 19	138 ± 17	^a1.70 (1.17–2.47)	0.005^b
<120 [n (%)]	150 (36.2)	4 (11.8)	1.0
120≤ <140 [n (%)] (vs. <120)	165 (39.9)	18 (52.9)	4.09 (1.35–12.40)	0.013
140≤ <160 [n (%)] (vs. <120)	76 (18.4)	7 (20.6)	3.45 (0.98–12.17)	0.054
≥160 [n (%)] (vs. <120)	23 (5.6)	5 (14.7)	8.15 (2.04–32.60)	0.003
DM [n (%)]	184 (44.4)	17 (50)	1.25 (0.62–2.52)	0.532
CVA [n (%)]	74 (17.9)	8 (26.5)	1.65 (0.74–3.69)	0.219
PAOD [n (%)]	20 (4.8)	3 (8.8)	1.91 (0.54–6.77)	0.318
COPD [n (%)]	32 (7.7)	5 (14.7)	2.06 (0.75–5.68)	0.163
Preoperative GFR (per 15 mL/min/1.73 m^2)	72.1 ± 18.3	65.0 ± 28.5	^c2.12 (1.45–3.10)	0.000b
≥60	314 (75.8)	17 (50)	1.0
45≤ <60 (vs. ≥60)	76 (18.4)	9 (26.5)	2.19 (0.94–5.10)	0.070
30≤ <45 (vs. ≥60)	17 (4.1)	5 (14.7)	5.43 (1.79–16.49)	0.003
15≤ <30 (vs. ≥60)	7 (1.7)	3 (8.8)	7.92 (1.88–33.34)	0.005
Recent MI [n (%)]	23 (5.6)	5 (14.7)	2.93 (1.04–8.28)	0.042
Coronary arteries with ≥50% stenosis
1 vessel [n (%)] (vs. 3 vessels)	22 (5.3)	2 (5.9)	0.99 (0.22–4.42)	0.986
2 vessels [n (%)] (vs. 3 vessels)	78 (18.8)	5 (14.7)	0.70 (0.26–1.87)	0.471
3 vessels [n (%)]	293 (70.8)	27 (79.4)	1.0
^dLVEF (%)	61 (53–68)	59 (51–65)
≥55 [n (%)]	295 (72.5)	23 (69.7)	1.0
45≤ <55 [n (%)] (vs. ≥55)	58 (14.3)	6 (18.2)	1.33 (0.52–3.40)	0.556
35≤ <45 [n (%)] (vs. ≥55)	38 (9.3)	2 (6.1)	0.68 (0.15–2.98)	0.604
<35 [n (%)] (vs. ≥55)	16 (3.9)	2 (6.1)	1.60 (0.35–7.40)	0.545
CAG ≤7 days [n (%)]	274 (66.2)	28 (82.4)	2.37 (0.96–5.85)	0.062

Notes: AKI, acute kidney injury; OR, odds ratio; CI, confidence interval; BMI, body mass index; SBP, systolic blood pressure; DM, diabetes mellitus; CVA, cerebrovascular accident; PAOD, peripheral artery occlusive disease; COPD, chronic obstructive pulmonary disease; GFR, glomerular filtration rate; MI, myocardial infarction; LVEF, left ventricular ejection fraction; CAG, coronary angiography.

^aThe OR is for 20 mmHg increment in systolic blood pressure.

^bp for trend.

^cThe OR is for 15 mL/min/1.73 m2 decrement in glomerular filtration rate.

^dData on preoperative ejection fraction were not available for eight patients.

Figure 1. Proportion of patients according to AKIN classification.

Table 3. Multivariate analysis of acute kidney injury following isolated first off-pump coronary artery bypass graft surgery

Covariate	OR	95% CI	p-Value	Points	AUC for single variable
SBP (mmHg)	^a1.65	1.11–2.45	0.013		0.645
<120	1.0			0
120≤ <140 (vs. <120)	4.32	1.38–13.54	0.012	1
140≤ <160 (vs. <120)	2.71	0.73–10.06	0.136	1
≥160 (vs. <120)	8.61	2.05–36.24	0.003	2
Preoperative GFR (mL/min/1.73 m^2)	^b2.27	1.46–3.53	0.000		0.644
≥60	1.0			0
45≤ <60 (vs. ≥60)	2.67	0.993–7.19	0.052	1
30≤ <45 (vs. ≥60)	8.26	2.20–30.96	0.002	2
15≤ <30 (vs. ≥60)	12.14	2.30–63.98	0.003	3
CAG ≤7 days	3.00	1.12–8.01	0.029	1	0.581

Notes: Multivariate analysis was done with age, sex, SBP, GFR, recent MI, CAG ≤7 days. SBP, systolic blood pressure; GFR, glomerular filtration rate; MI, myocardial infarction; CAG, coronary angiography.

^aThe OR is for 20 mmHg increment in systolic blood pressure.

^bThe OR is for 15 mL/min/1.73 m2 decrement in glomerular filtration rate.

Figure 2. A risk-scoring scheme for estimating acute kidney injury after off-pump coronary artery bypass grafting.

Notes: SBP, systemic blood pressure; GFR, glomerular filtration rate; CAG, coronary angiography.

Figure 3. Incidence of postoperative acute kidney injury by risk score.

Figure 4. Receiver operating characteristic curve for prediction of acute kidney injury after off-pump coronary artery bypass grafting.