Heart and Kidneys: „Self-defense“ prevents Surgery Complications

Münster (mfm/tw) – Heart surgeries endanger the kidneys: Open heart surgeries can lead to acute kidney failure and there is no effective protection against it so far. An international team surrounding the Münster Professor of Anesthesiology, MD Alexander Zarbock, tricked the kidney into defending themselves. The findings from the study were made public in the American Expert Magazine JAMA (The Journal of the American Medical Association) on 29th May.

Acute kidney failure is one of the most frequent complications with heart surgeries – the kidneys do not function at an efficient level and can only insufficiently eliminate toxins. Very often the blood of the patients needs to be cleansed by dialysis and in the worst case kidney failure leads to death. Zarbock and his colleagues have now significantly lowered the likelihood of complications by warning the kidneys in advance.

“The trick is simple”, explains Zarbock: “We feign an injury inside the body by stopping the blood flow of an artery in the arm of the patient for only a few minutes. The blood flow into the forearm is stopped and the body releases message substances (neurotransmitters) into the blood circulation. The kidneys filter these molecules and identify them as alarm signals for damages in the body and get their defense running”. The procedure – known as ischemic preconditioning – has already proven its effectiveness in some studies as a preventive measure for damages to the heart with coronary heart diseases.

In the current study the team detected some signals that are applied by kidney cells when they alert each other to the threat of injury, according to Zarbock who works as a senior physician at the Department of Anesthesiology, Intensive Care and Pain Therapy of the University Clinic Münster and holds a Heisenberg Professorship of the German Research Foundation: “We were able to identify the biomarkers TIMP2 and IGFBP7 in the urine of patients receiving pre-treatment. Normally these molecules signal that the kidneys are stressed and are not functioning properly but in this case they are protective to secondary damages”.

“This system works very similar to a fire-alarm”, explains co-author John Kellum, MD, Director of the Center for Critical Care Nephrology at the University of Pittsburgh/Pennsylvania in the USA. “Fire alarms are installed to help protect the building and its occupants. When a fire-alarm goes off it indicates a dangerous situation – the alarm itself has a positive effect. We have managed to trip the alarm even before the fire breaks out.”

In total the researchers consider 240 high-risk cardiac surgery patients in Münster, Tübingen, Freiburg and Bochum. 38 per cent of the patients whose kidneys had been prepared for injuries suffered acute kidney failure and those who had not received pre-treatment stood at 53 per cent. For IPC patients the duration of intensive care was reduced by one day at an average, only 6 per cent required dialysis after the surgery compared to 16 per cent of the untreated patients. Whether the mortality rate following a heart surgery can be decreased by IPC can still not be stated by the researchers due to the size of the study.

“This study indicates several helpful aspects”, according to Kellum: “A new treatment approach for a dangerous disease, new tests to gauge the treatment´s efficacy and new insights into why the disease occurs in the first place. Very rarely a single study does accomplish so much”.

Original publication:

Zarbock A. et al.: Effect of Remote Ischemic Preconditioning on Kidney Injury Among High-Risk Patients Undergoing Cardiac Surgery: Randomized Clinical Trial. JAMA. Published online May 29, 2015. doi:10.1001/jama.2015.4189

Contact:

Dr. Thomas Bauer
Referent Research and Teaching
Medical Faculty, Westfälische Wilhelms-Universität Münster
Phone: 0251-83-58937
Mail: thbauer@uni-muenster.de

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