Paul Thottakkara

COST AND MORTALITY ASSOCIATED WITH POSTOPERATIVE ACUTE KIDNEY INJURY

OBJECTIVE To determine the incremental hospital cost and mortality associated with the development of postoperative acute kidney injury (AKI) and with other associated postoperative complications. BACKGROUND Each year 1.5 million patients develop a major complication after surgery. Postoperative AKI is one of the most common postoperative complications and is associated with an increase in hospital mortality and decreased survival for up to 15 years after surgery. METHODS In a single-center cohort of 50,314 adult surgical patients undergoing major inpatient surgery, we applied risk-adjusted regression models for cost and mortality using postoperative AKI and other complications as the main independent predictors. We defined AKI using consensus Risk, Injury, Failure, Loss and End-Stage Renal Disease criteria. RESULTS The prevalence of AKI was 39% among 50,314 patients with available serum creatinine. Patients with AKI were more likely to have postoperative complications and had longer lengths of stay in the intensive care unit and the hospital. The risk-adjusted average cost of care for patients undergoing surgery was

Mortality and Cost of Acute and Chronic Kidney Disease after Vascular Surgery

42,600 for patients with any AKI compared with

The Pattern of Longitudinal Change in Serum Creatinine and 90-Day Mortality After Major Surgery.

26,700 for patients without AKI. The risk-adjusted 90-day mortality was 6.5% for patients with any AKI compared with 4.4% for patients without AKI. Serious postoperative complications resulted in increased cost of care and mortality for all patients, but the increase was much larger for those patients with any degree of AKI. CONCLUSIONS Hospital costs and mortality are strongly associated with postoperative AKI, are correlated with the severity of AKI, and are much higher for patients with other postoperative complications in addition to AKI.

Acute and Chronic Kidney Disease and Cardiovascular Mortality After Major Surgery.

BACKGROUND Both acute kidney injury (AKI) and chronic kidney disease (CKD) are common yet underappreciated risk factors for adverse perioperative outcomes. We hypothesize that AKI and CKD are associated with similar increases in 90-day mortality and cost in patients undergoing major vascular surgery. METHODS We used multivariable regression analyses to evaluate the associations between AKI and CKD and incremental 90-day mortality and hospital cost in a single-center cohort of 3646 adult patients undergoing major vascular surgery. We defined AKI using Kidney Disease: Improving Global Outcomes criteria as change in creatinine ≥ 0.3 mg/dL or ≥ 50% increase from the reference value. CKD was determined from medical history. Regression models were adjusted for demographic and socioeconomic characteristics, comorbid conditions, surgery type, and postoperative complications. RESULTS The prevalence of kidney disease among vascular surgery patients is high with 49% of patients developing AKI during hospitalization and 17% presenting with CKD on admission. In risk-adjusted logistic regression analysis, perioperative AKI (odds ratio 2.2, 95% confidence interval 1.5-3.3) was the most significant predictor of 90-day mortality. The risk-adjusted average cost was significantly higher for patients with any type of kidney disease. The incremental cost of having any type of kidney disease ranged from

Application of Machine Learning Techniques to High-Dimensional Clinical Data to Forecast Postoperative Complications

9100 to

Mortality and Cost of Acute and Chronic Kidney Disease After Vascular Surgery

19,100, even after adjustment for underlying comorbidities and other postoperative complications. CONCLUSIONS Kidney disease after major vascular surgery is associated with significant increases in 90-day mortality and cost with the highest risk observed among patients with AKI regardless of previous CKD.

Preoperative assessment of the risk for multiple complications after surgery

Objective:Calculate mortality risk that accounts for both severity and recovery of postoperative kidney dysfunction using the pattern of longitudinal change in creatinine. Background:Although the importance of renal recovery after acute kidney injury (AKI) is increasingly recognized, the complex association that accounts for longitudinal creatinine changes and mortality is not fully described. Methods:We used routinely collected clinical information for 46,299 adult patients undergoing major surgery to develop a multivariable probabilistic model optimized for nonlinearity of serum creatinine time series that calculates the risk function for 90-day mortality. We performed a 70/30 cross validation analysis to assess the accuracy of the model. Results:All creatinine time series exhibited nonlinear risk function in relation to 90-day mortality and their addition to other clinical factors improved the model discrimination. For any given severity of AKI, patients with complete renal recovery, as manifested by the return of the discharge creatinine to the baseline value, experienced a significant decrease in the odds of dying within 90 days of admission compared with patients with partial recovery. Yet, for any severity of AKI, even complete renal recovery did not entirely mitigate the increased odds of dying, as patients with mild AKI and complete renal recovery still had significantly increased odds for dying compared with patients without AKI [odds ratio: 1.48 (95% confidence interval: 1.30–1.68)]. Conclusions:We demonstrate the nonlinear relationship between both severity and recovery of renal dysfunction and 90-day mortality after major surgery. We have developed an easily applicable computer algorithm that calculates this complex relationship.

Improved Predictive Models for Acute Kidney Injury with IDEAs: Intraoperative Data Embedded Analytics.

Objective: The aim of the study was to determine the long-term cardiovascular-specific mortality in patients with acute kidney injury (AKI) or chronic kidney disease (CKD) after major surgery. Background: In surgical patients, pre-existing CKD and postoperative AKI are associated with increases in all-cause mortality. Methods: In a single-center cohort of 51,457 adult surgical patients undergoing major inpatient surgery, long-term cardiovascular-specific mortality was modeled using a multivariable subdistributional hazards model while treating any other cause of death as a competing risk and accounting for the progression to end-stage renal disease (ESRD) after discharge. Pre-existing CKD and ESRD, and postoperative AKI were the main independent predictors. Results: Before the admission, 4% and 8% of the cohort had pre-existing ESRD and CKD not requiring renal replacement therapy, respectively. During hospitalization, 39% developed AKI. At 10-year follow-up, adjusted cardiovascular-specific mortality estimates were 6%, 11%, 12%, 19%, and 27% for patients with no kidney disease, AKI with no CKD, CKD with no AKI, AKI with CKD, and ESRD, respectively (P < 0.001). This association remained after excluding 916 patients who progressed to ESRD after discharge, although it was significantly amplified among them. Compared with patients having no kidney disease, adjusted hazard ratios for cardiovascular mortality were significantly higher among patients with kidney disease, ranging from 1.95 (95% confidence interval, 1.80–2.11) for patients with de novo AKI to 5.70 (95% confidence interval, 5.00–6.49) for patients with pre-existing ESRD. Conclusions: Both AKI and CKD were associated with higher long-term cardiovascular-specific mortality compared with patients having no kidney disease.

Cardiovascular-Specific Mortality and Kidney Disease in Patients Undergoing Vascular Surgery

Objective To compare performance of risk prediction models for forecasting postoperative sepsis and acute kidney injury. Design Retrospective single center cohort study of adult surgical patients admitted between 2000 and 2010. Patients 50,318 adult patients undergoing major surgery. Measurements We evaluated the performance of logistic regression, generalized additive models, naïve Bayes and support vector machines for forecasting postoperative sepsis and acute kidney injury. We assessed the impact of feature reduction techniques on predictive performance. Model performance was determined using the area under the receiver operating characteristic curve, accuracy, and positive predicted value. The results were reported based on a 70/30 cross validation procedure where the data were randomly split into 70% used for training the model and the 30% for validation. Main Results The areas under the receiver operating characteristic curve for different models ranged between 0.797 and 0.858 for acute kidney injury and between 0.757 and 0.909 for severe sepsis. Logistic regression, generalized additive model, and support vector machines had better performance compared to Naïve Bayes model. Generalized additive models additionally accounted for non-linearity of continuous clinical variables as depicted in their risk patterns plots. Reducing the input feature space with LASSO had minimal effect on prediction performance, while feature extraction using principal component analysis improved performance of the models. Conclusions Generalized additive models and support vector machines had good performance as risk prediction model for postoperative sepsis and AKI. Feature extraction using principal component analysis improved the predictive performance of all models.

35. Mortality and Cost of Chronic and Acute Kidney Disease After Vascular Surgery

Background: Both acute kidney injury (AKI) and chronic kidney disease (CKD) are common yet underappreciated risk factors for adverse perioperative outcomes. We hypothesize that AKI and CKD are associated with similar increases in 90-day mortality and cost in patients undergoing major vascular surgery. Methods: We used multivariable regression analyses to evaluate the associations between AKI and CKD and incremental 90-day mortality and hospital cost in a single-center cohort of 3646 adult patients undergoing major vascular surgery. We defined AKI using Kidney Disease: Improving Global Outcomes criteria as change in creatinine 0.3 mg/dL or 50% increase from the reference value. CKD was determined from medical history. Regression models were adjusted for demographic and socioeconomic characteristics, comorbid conditions, surgery type, and postoperative complications. Results: The prevalence of kidney disease among vascular surgery patients is high with 49% of patients developing AKI during hospitalization and 17% presenting with CKD on admission. In risk-adjusted logistic regression analysis, perioperative AKI (odds ratio 2.2, 95% confidence interval 1.5e3.3) was the most significant predictor of 90-day mortality. The risk-adjusted average cost was significantly higher for patients with any type of kidney disease. The incremental cost of having any type of kidney disease ranged from