Table 1.
Independent Preoperative Predictors of Acute Kidney Injury from the Derivation Cohort of 70,929 Patients: Weighted Risk Score Multivariable Logistic Regression Model
| Risk Factor | β-Coefficient | aOR (95% CI) | Points in Model* | |
|---|---|---|---|---|
| Medical factors | ||||
| Patient age (yr) | ||||
| 18–30 | Reference | 0 | ||
| 31–40 | −0.001 | 1.00 (0.86–1.16) | ||
| 41–50 | −0.029 | 0.97 (0.85–1.12) | ||
| 51–60 | 0.090 | 1.09 (0.96–1.24) | ||
| 61–70 | 0.065 | 1.07 (0.94–1.22) | ||
| 71–80 | 0.028 | 1.03 (0.89–1.19) | ||
| > 80 | 0.070 | 1.07 (0.91–1.26) | ||
| BMI (kg/m2, by WHO Classification) | ||||
| Underweight (< 18.5) | 0.010 | 1.01 (0.85–1.20) | 0 | |
| Normal weight (18.5–24.9) | Reference | |||
| Overweight (25.0–29.9) | 0.078 | 1.08 (1.00–1.17) | ||
| Class I obesity (30.0–34.9) | 0.235 | 1.27 (1.16–1.38) | 1 | |
| Class II obesity (35.0–39.9) | 0.344 | 1.41 (1.27–1.56) | ||
| Class III obesity (> 40.0) | 0.426 | 1.53 (1.39–1.69) | ||
| Male gender | 0.215 | 1.24 (1.17–1.31) | ||
| Patient medical history† | ||||
| Liver disease | 0.427 | 1.53 (1.40–1.68) | 1 | |
| Coagulopathy | 0.369 | 1.44 (1.32–1.59) | 1 | |
| Hypertension, complicated | 0.264 | 1.30 (1.18–1.44) | 1 | |
| Diabetes, complicated | 0.293 | 1.34 (1.15–1.57) | 1 | |
| Weight loss | 0.220 | 1.25 (1.14–1.36) | 1 | |
| Pulmonary circulation disorders | 0.160 | 1.17 (1.05–1.31) | 1 | |
| AIDS/HIV | 0.547 | 1.73 (1.02–2.92) | 2 | |
| Congestive heart failure | 0.034 | 1.04 (0.94–1.14) | 0 | |
| Cardiac arrhythmias | 0.104 | 1.11 (1.03–1.20) | 0 | |
| Peripheral vascular disorders | 0.062 | 1.06 (0.98–1.15) | 0 | |
| Chronic pulmonary disease | 0.009 | 1.01 (0.94–1.09) | 0 | |
| Hypertension, uncomplicated | 0.023 | 1.02 (0.96–1.10) | 0 | |
| Diabetes, uncomplicated | 0.051 | 1.05 (0.98–1.13) | 0 | |
| Lymphoma | 0.113 | 1.12 (0.92–1.36) | 0 | |
| Paralysis/other neurologic disorders | 0.106 | 1.12 (1.01–1.23) | 0 | |
| Metastatic cancer | 0.013 | 1.01 (0.92–1.12) | 0 | |
| Psychoses | −0.077 | 0.93 (0.73–1.18) | 0 | |
| Valvular disease | 0.003 | 1.00 (0.90–1.12) | 0 | |
| Drug abuse | −0.042 | 0.96 (0.81–1.14) | 0 | |
| Rheumatoid arthritis/collagen vascular diseases | −0.067 | 0.94 (0.81–1.08) | 0 | |
| Peptic ulcer disease excluding bleeding | 0.028 | 1.03 (0.85–1.25) | 0 | |
| Solid tumor | −0.014 | 0.99 (0.91–1.07) | 0 | |
| Hypothyroidism | −0.135 | 0.87 (0.80–0.96) | 0 | |
| Alcohol abuse | −0.155 | 0.86 (0.75–0.99) | 0 | |
| Preoperative chronic medications | ||||
| ACEI/ARB | −0.016 | 0.98 (0.91–1.07) | 0 | |
| β-Blocker | −0.114 | 0.89 (0.83–0.96) | 0 | |
| Anemia (hemoglobin range, g/dl) | ||||
| Normal (> 12.0, females; > 13.0, males) | Reference | 0 | ||
| Mild (10.1–12.0, females; 10.1–13.0, males)‡ | 0.523 | 1.69 (1.57–1.81) | 2 | |
| Moderate to severe (≤ 10.0)‡ | 0.731 | 2.08 (1.92–2.25) | 2 | |
| CKD severity (eGFR range, ml · min−1 · 1.73 m−2) | ||||
| Stage 1 (≥ 90)§ | Reference | 0 | ||
| Stage 2 (60–89§ | 0.085 | 1.09 (1.01–1.17) | 2 | |
| Stage 3a (45–59)§ | 0.371 | 1.45 (1.31–1.60) | 3 | |
| Stage 3b (30–44)§ | 0.706 | 2.03 (1.82–2.26) | ||
| Stage 4 (15–29)§ | 1.357 | 3.89 (3.47–4.38) | 4 | |
| Preinduction baseline mean arterial pressure range (mmHg)∥ | ||||
| Hypotensive (< 70) | 0.283 | 1.33 (1.21–1.45) | 1 | |
| Normotensive (70–107) | Reference | 0 | ||
| Stage 1 hypertension (108–120) | 0.135 | 1.15 (1.04–1.26) | ||
| Stage 2 hypertension (> 120) | 0.348 | 1.42 (1.22–1.65) | 1 | |
| Surgical factors | ||||
| Surgical body region | ||||
| Elevated risk (all regions except below) | 0.839 | 2.31 (2.10–2.55) | 3 | |
| Low Risk (ENT, upper extremity, spine) | Reference | 0 | ||
| Emergent surgery | 0.253 | 1.29 (1.18–1.41) | 1 | |
| Anesthetic factors | ||||
| ASA class | ||||
| ASA class 1 | Reference | 0 | ||
| ASA class 2 | −0.019 | 0.98 (0.77–1.25) | ||
| ASA class 3 | 0.586 | 1.80 (1.41–2.29) | 3 | |
| ASA class 4 | 0.924 | 2.52 (1.96–3.23) | 4 | |
| ASA class 5 | 1.561 | 4.76 (3.22–7.05) | 5 | |
| Expected anesthesia duration > 1 h | 0.077 | 1.08 (1.07–1.09) | (h/4)# | |
| General anesthesia | 0.395 | 1.49 (1.36–1.63) | 1 | |
| Institutional factors | ||||
| Nonuniversity hospital | 0.195 | 1.22 (1.09–1.36) | 1 | |
| Weighted risk score model c-statistic (95% CI) | 0.76 (0.75–0.76) | |||
| Preoperative Risk Quartiles | Points in Model | Number of Cases, n (%) | observed AKI Proportion (%) | |
| Quartile 1 (low risk) | 1–7 | 14,521 (20) | 1.7 | |
| Quartile 2 (medium risk) | 8–10 | 20,372 (29) | 4.6 | |
| Quartile 3 (high risk) | 11–12 | 15,255 (22) | 7.8 | |
| Quartile 4 (highest risk) | ≥ 13 | 20,781 (29) | 17.8 | |
Fixed-effects model excluding anonymized institution identifier; continuous variables transformed to ordinal/interval scales. Weighted risk score values were derived using β-coefficients normalized to approximated integer multiples for clinical simplification.
As determined by Elixhauser Comorbidity Enhanced ICD-9-CM/ICD-10 CM algorithm.
As determined by CKD–EPI formula, indexed by body surface area; classification of chronic kidney disease stage by the Kidney Disease: Improving Global Outcomes 2012 practice guidelines.48
Classification of hypertension ranges by Seventh Report of the Joint National Committee,50 and hypotension range as defined by the National Heart, Lung, and Blood Institute’s Health Information for the Public.51
One point for every 4 h.
ACEI, angiotensin converting enzyme inhibitor; AIDS, autoimmune deficiency syndrome; AKI, acute kidney injury; aOR, adjusted odds ratio; ARB, angiotensin receptor blocker; ASA, American Society of Anesthesiologists; BMI, body mass index; CKD, chronic kidney disease; CKD–EPI, Chronic Kidney Disease Epidemiology Collaboration; eGFR, estimated glomerular filtration rate; ENT, ear/nose/throat; HIV, human immunodeficiency virus; WHO, World Health Organization.