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This study aimed to perform and validate a scale to predict Acute kidney injury (AKI) in patients not requiring renal replacement therapy after coronary artery bypass graft (CABG), using Kidney Disease Improving Global Outcomes (KDIGO) criteria.
This was a retrospective case-control study that included patients over 18 years old who underwent CABG at a third-level hospital from 2013 to 2018 who could develop or not AKI based on the KDIGO criteria. A risk score was developed based on logistic regression modeling and validate using a 10 fold validation.
A total of 191 patients were included in the study; the mean (SD) age was 64.2 (9.2%) years, 161(84.3%) were men. The number of AKI events was 71 (37.1%). Based on the regression model, the predictor factors for AKI where: age (OR 1.052), congestive heart failure (OR 6.201), left predominant coronary lesion with occlusion >90% (OR 3.673), pump time (OR 1.013), and haemoglobin <12mg/dl (OR 0.245). Based on these variables, we computed a scale (AKIM-score) ranged from 0-15, we validated the scale using a 10 fold validation where a score between 5-8 was considered a moderate risk, and > 9 was considered high risk for AKI based on the specificity of each score. A score greater than or equal to 9 had a specificity greater than 0.8 as determined by the 10 fold validation model.
Table 1 Medical history by groups
Characteristic
(n=191)
AKI negative
(n=120)
AKI positive
(n=71)
p-value
Age (years)
62.6 (9.1)
67.06 (8.7)
0.001
Gender (men)
105 (87.5)
56 (78.8)
0.113
BMI
28.4 (4.0)
28.3 (5.1)
0.836
DM2
45 (37.5)
38 (53.5)
0.031
PVD
7 (5.8)
2 (2.8)
0.342
CHF
6 (5)
16 (22.5)
0.000
COPD
0 (0)
3 (4.2)
0.023
Hypertension
76 (63.3)
51 (71.8)
0.229
Smoking status
Never smoked
Ex-smoker
Current smoker
81 (67.5)
12 (10)
27 (22.5)
59 (83)
3 (4.22)
9 (12.6)
0.059
Prior MI
None
One
≥2
75 (62.5)
39 (32.5)
42 (59.1)
28 (39.4)
1 (1.4)
0.322
Triple vessel disease
95(79.1)
53 (74.6)
0.470
Previous Bypass surgery
4 (3.3)
0.843
Results are expressed as mean (SD) if they are continuous variables or frequency (%) if they are categorical
Chi2 and t-test were performed for group comparisons. P <0.05 was considered statistically significant. Hypertension was defined as treated or blood pressure >140/90 mmHg. Abbreviations: AKI: acute Kidney injury, BMI: body mass index. DM2: diabetes mellitus, PVD: peripheral vascular disease. CHF: congestive heart failure, COPD: chronic obstructive pulmonary disease. MI: myocardial infarction. BMI: Body mass index.
Table 2 Pre-operative characteristics associated with AKI by group
AKI negative (n=120)
AKI positive (n=71)
Anginaa
Without angina
CCS 1
CCS 2
CCS 3
CCS 4
4(3.3)
8(6.7)
80(66.7)
27(22.5)
1(0.8)
0(0)
1(1.4)
40(60.6)
27(38)
0.047*
In our predictive model, we found that age and factors related to heart function predicted AKI development in patients who underwent CABG in our population. We developed AKIM-score, where a range from 1-4 was associated with low risk, 5-8 with moderate risk, and a score >9 is associated with a high risk of AKI.