Impact of Ultrafiltration on Kidney Injury After Cardiac Surgery: The Michigan Experience.

BACKGROUND: This study examines the relationship between the use and volume of conventional ultrafiltration (CUF) and the risk of acute kidney injury (AKI) after isolated on-pump coronary artery bypass graft surgery. METHODS: A total of 6,407 consecutive patients underwent isolated on-pump coronary artery bypass graft surgery between 2010 and 2013 at 21 medical centers participating in the PERFusion Measures and Outcomes (PERForm) registry. We assessed the effect of CUF use on AKI and other postoperative sequelae using a generalized linear mixed-effect model with a logit link. We also modeled the effect of increasing volume of CUF per weight on AKI, and tested for any modification by a patient's preoperative kidney function. RESULTS: Patients having CUF were more likely to have diabetes, vascular disease, chronic obstructive pulmonary disease, congestive heart failure, history of a myocardial infarction, or an intraaortic balloon pump (p < 0.05). They had lower preoperative and nadir hematocrits, creatinine clearance, and ejection fraction (p < 0.05). Patients exposed to CUF had higher adjusted risk of AKI (adjusted odds ratio, 1.36; p = 0.002), although similar rates of death, stroke, and reoperation for bleeding (p > 0.05). The risk of AKI was modified by a patient's preoperative kidney function (p < 0.0004). Among patients with a creatinine clearance of less than 99.6 mL/min (95% confidence interval, 67.6 to 137.5), increasing volume of CUF was associated with a higher risk of AKI. CONCLUSIONS: Patients exposed to CUF had a higher adjusted risk of AKI. Clinical teams should consider lower volumes of CUF among patients with low creatinine clearance to minimize the risk of AKI.

Geographic variability in potentially discretionary red blood cell transfusions after coronary artery bypass graft surgery.

OBJECTIVE: A number of established regional quality improvement collaboratives have partnered to assess and improve care across their regions under the umbrella of the Cardiac Surgery Quality Improvement (IMPROVE) Network. The first effort of the IMPROVE Network has been to assess regional differences in potentially discretionary transfusions (<3 units red blood cells [RBCs]). METHODS: We examined 11,200 patients undergoing isolated nonemergent coronary artery bypass graft surgery across 56 medical centers in 4 IMPROVE Network regions between January 2008 and June 2012. Each center submitted the most recent 200 patients who received 0, 1, or 2 units of RBC transfusion during the index admission. Patient and disease characteristics, intraoperative practices, and percentage of patients receiving RBC transfusions were collected. Region-specific transfusion rates were calculated after adjusting for pre- and intraoperative factors among region-specific centers. RESULTS: There were small but significant differences in patient case mix across regions. RBC transfusions of 1 or 2 units occurred among 25.2% of coronary artery bypass graft procedures (2826 out of 11,200). Significant variation in the number of RBC units used existed across regions (no units, 74.8% [min-max, 70.0%-84.1%], 1 unit, 9.7% [min-max, 5.1%-11.8%], 2 units, 15.5% [min-max, 9.1%-18.2%]; P < .001). Variation in overall transfusion rates remained after adjustment (9.1%-31.7%; P < .001). CONCLUSIONS: Delivery of small volumes of RBC transfusions was common, yet varied across geographic regions. These data suggest that differences in regional practice environments, including transfusion triggers and anemia management, may contribute to variability in RBC transfusion rates.

Aortic valve replacement: using a statewide cardiac surgical database identifies a procedural volume hinge point.

BACKGROUND: Expanding therapies for aortic stenosis have focused on high-risk and inoperable patients, suggesting that an evaluation of outcomes of conventional aortic valve replacement (AVR) or AVR and coronary artery bypass grafting (CABG) is timely and warranted. METHODS: Outcomes for 6,270 AVR (3,487) or AVR/CABG (2,783) procedures performed in Michigan (2008-2011) were analyzed using a statewide cardiothoracic surgical database. Hospital and surgeon volume-outcome relationships were assessed. RESULTS: Independent predictors of early mortality (all p < 0.05) included age, female sex, predicted risk of mortality, and hospital volume, with a hinge point of a 4-year volume of 390 procedures (high-volume hospital [HVH], 2.41% versus low-volume hospital [LVH], 4.34%; p < 0.001). At this hinge point, observed to expected ratio (O/E) for operative mortality after AVR was lower in HVHs for patients with a predicted risk of mortality (PRoM) greater than 4.7%. In contrast, no surgeon-volume outcome relationship was identified, even when stratified by preoperative patient-risk profile. With respect to other measures, HVHs reported lower rates of prolonged ventilation (24.9% versus LVH, 30.9%; p < 0.001), postoperative transfusion (46.1% versus LVH, 59.0%; p < 0.001), pneumonia (6.6% versus LVH, 9.0%; p = 0.01), and multisystem organ failure (0.7% versus LVH, 1.8%; p = 0.012). CONCLUSIONS: This population-based analysis suggests that volume-outcome relationships exist for AVR. The predominant effect on mortality appears based on the setting of the procedure and occurs primarily in the high-risk patient. These results provide an opportunity to review approaches for high-risk patients undergoing AVR, including resource availability and system experience as the spectrum of treatment options expands to transcatheter therapies.

Cardiac surgeons and the quality movement: the Michigan experience.

The Michigan Society of Thoracic and Cardiovascular Surgeons created a voluntary quality collaborative with all the cardiac surgeons in the state and all hospitals doing adult cardiac surgery. Utilizing this collaborative over the last 3 years and creating a unique relationship with a payor, an approach to processes and outcomes has produced improvements in the quality of care for cardiac patients in the state of Michigan.