SCM15: AKI Post Cardiac Surgery, What’s New

Dr. Minh-Thu DuongDr. Minh-Thu Duong (MD), from Staten Island University Hospital, NSLIJ Health System, New York, NY, discusses her abstract for the National Kidney Foundation’s 2015 Spring Clinical Meetings (SCM15), Acute Kidney Injury Post Cardiac Surgery: Incidence, Mortality, Renal Recovery, and Quality of Life in Those Requiring Continuous Veno-Venous Hemofiltration, with Dr. Kenar Jhaveri, AJKD Blog Editor.

AJKDblog: Why don’t you tell us a little about your research and abstract being presented at the NKF 2015 Spring Meetings?
MD: Acute kidney injury (AKI) is a significant cause of morbidity and mortality following cardiac surgery. Some of these AKI cases recover with medical management or intermittent hemodialysis while others require continuous venovenous hemofiltration (CVVH). Many studies have been done on mortality in the CVVH group but they all have only included cardiac surgery cases that involved utilization of the cardiopulmonary bypass (CPB). This study reviews post cardiac surgery patients who developed AKI, assesses for preoperative risks, determines 30-day and long-term survival differences between those who were put on CVVH versus those treated without CVVH, and assesses for quality of life after hospital discharge. In terms of preoperative risk factors in our study, the CVVH group had a higher rate of CPB utilization, higher Parsonnet and EuroScore mortality risk, lower rate of CABG surgeries while higher number of CABG-valve combined surgeries. The CVVH group had a higher 30-day mortality rate and a lower mean number of months for long-term survival. However, in those who survived past 30 days, the CVVH group had a slightly lower rate requiring permanent hemodialysis and lower rate of discharging to nursing facility instead of going home.

This is the first study that includes non-CPB cardiac surgery subjects and the largest study that assesses long-term survival and quality of life in CPB and non-CPB cardiac surgery patients.

AJKDblog: Dialysis requiring AKI had no impact on permanent need of HD and long term nursing facility and recovery in the hospital. How do you explain this finding?
MD: CVVH-requiring AKI patients actually had a slightly lower rate of permanent need for hemodialysis. Although previous studies have shown no difference in renal recovery in CVVH versus intermittent HD, our study focused on post cardiac surgery patients, which is a unique subgroup of patients within critical care medicine. The general population of patients started on CVVH is mostly due to hyperkalemia and acidosis while post cardiac surgery patients in our study were mostly started on CVVH due to fluid overload. Hence, these patients may have benefited more from the hemodynamic stability offered by CVVH over intermittent HD. Hemodynamic stability translates to less hypotensive episodes during and following HD, which translates to less injury to the kidneys and lower rate of requiring permanent HD.

AJKDblog: Did you notice a difference in Off-Pump vs. On Pump patients in Group 1 and 2?

MD: Group 1, the CVVH group, had a significantly higher rate of on-pump surgeries. This group also had a 30-day mortality rate roughly three times as high as the non-CVVH group. It is understood that the mortality in CVVH group is multifactorial, but on-pump cardiac surgeries may be associated with increased mortality for two reasons. The first reason is the fact that on-pump patients come into the procedure already at higher risk. If patients are hemodynamically unstable at time of surgery, if target vessels are not readily visible, if cardiac position is not optimal, patients meet criteria to be on-pump. Therefore, the association between cardiopulmonary bypass utilization and increased mortality may be due to selection of patients.

Cardiopulmonary bypass utilization may also be associated with increased mortality because it is associated with a systemic inflammatory response. On-pump procedures are linked to increased production of oxygen-derived free radicals, activation of neutrophils and complement cascade, all of which will pose negative influences on the heart, lung, and kidneys.

Click here for a full list of SCM15 abstracts of poster presentations.

Check out more AJKDblog coverage of the NKF’s 2015 Spring Clinical Meetings!

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