Predictive Accuracy of a Perioperative Laboratory Test-Based Prediction Model for Moderate to Severe Acute Kidney Injury After Cardiac Surgery

Abstract

Importance: Effective treatment of acute kidney injury (AKI) is predicated on timely diagnosis; however, the lag in the increase in serum creatinine levels after kidney injury may delay therapy initiation.

Objective: To determine the derivation and validation of predictive models for AKI after cardiac surgery.

Design, setting, and participants: Multivariable prediction models were derived based on a retrospective observational cohort of adult patients undergoing cardiac surgery between January 2000 and December 2019 from a US academic medical center (n = 58 526) and subsequently validated on an external cohort from 3 US community hospitals (n = 4734). The date of final follow-up was January 15, 2020.

Exposures: Perioperative change in serum creatinine and postoperative blood urea nitrogen, serum sodium, potassium, bicarbonate, and albumin from the first metabolic panel after cardiac surgery.

Main outcomes and measures: Area under the receiver-operating characteristic curve (AUC) and calibration measures for moderate to severe AKI, per Kidney Disease: Improving Global Outcomes (KDIGO), and AKI requiring dialysis prediction models within 72 hours and 14 days following surgery.

Results: In a derivation cohort of 58 526 patients (median [IQR] age, 66 [56-74] years; 39 173 [67%] men; 51 503 [91%] White participants), the rates of moderate to severe AKI and AKIrequiring dialysis were 2674 (4.6%) and 868 (1.48%) within 72 hours and 3156 (5.4%) and 1018 (1.74%) within 14 days after surgery. The median (IQR) interval to first metabolic panel from conclusion of the surgical procedure was 10 (7-12) hours. In the derivation cohort, the metabolic panel-based models had excellent predictive discrimination for moderate to severe AKI within 72 hours (AUC, 0.876 [95% CI, 0.869-0.883]) and 14 days (AUC, 0.854 [95% CI, 0.850-0.861]) after the surgical procedure and for AKI requiring dialysis within 72 hours (AUC, 0.916 [95% CI, 0.907-0.926]) and 14 days (AUC, 0.900 [95% CI, 0.889-0.909]) after the surgical procedure. In the validation cohort of 4734 patients (median [IQR] age, 67 (60-74) years; 3361 [71%] men; 3977 [87%] White participants), the models for moderate to severe AKI after the surgical procedure showed AUCs of 0.860 (95% CI, 0.838-0.882) within 72 hours and 0.842 (95% CI, 0.820-0.865) within 14 days and the models for AKI requiring dialysis and 14 days had an AUC of 0.879 (95% CI, 0.840-0.918) within 72 hours and 0.873 (95% CI, 0.836-0.910) within 14 days after the surgical procedure. Calibration assessed by Spiegelhalter z test showed P >.05 indicating adequate calibration for both validation and derivation models.

Conclusions and relevance: Among patients undergoing cardiac surgery, a prediction model based on perioperative basic metabolic panel laboratory values demonstrated good predictive accuracy for moderate to severe acute kidney injury within 72 hours and 14 days after the surgical procedure. Further research is needed to determine whether use of the risk prediction tool improves clinical outcomes.

Figure 1.. Derivation and Validation Cohorts Used to Develop the Prediction Models for Acute Kidney Injury (AKI) After Cardiac Surgery

CABG indicates coronary artery bypass.

Figure 2.. Adjusted Odds Ratios for Moderate to Severe Acute Kidney Injury (AKI) and AKI Requiring Dialysis Within 72 Hours of Surgery in the Derivation Cohort (n = 58 526)

The shaded area represents the 95% CI from the restricted cubic spline models. All plots were centered at median values for the respective variables. The odds ratio for each variable was adjusted for the median values of other variables in the model: preoperative serum creatinine at 1 mg/dL, serum albumin at 2.9 mg/dL, serum bicarbonate at 23 mmol/L, blood urea nitrogen at 15 mg/dL, change in serum creatinine at −0.06 mg/dL, serum potassium at 4.4 mmol/L, serum sodium at 138 mmol/L, and time from end of the operation to metabolic panel blood draw at 10 hours. Boxplots display the laboratory parameter distribution with or without AKI along the shared x-axis of each plot; boxes show the IQR, with the line representing the median point, box edges representing first and third quartiles, and whiskers extending to the value closest to 1.5 times the IQR (more extreme values not plotted).

Figure 3.. Receiver-Operating Characteristic Curves for Moderate to Severe AKI and AKI Requiring Dialysis in the Derivation and Validation Cohorts

The models include preoperative serum creatinine, perioperative change in serum creatinine, and postoperative serum albumin, bicarbonate, urea, potassium, sodium, time from end of the operation to panel blood draw, and 2 interaction terms.