Post graduate surgical students

Mr Michael Zhu
Working towards prevention of acute kidney injury in patients undergoing cardiac surgery

Acute kidney injury (AKI) after cardiac surgery is a common, yet difficult problem to tackle. New clinical research at Monash Medical Centre and Monash University may allow clinicians to detect the real-time risk of AKI intraoperatively, offering an opportunity to predict AKI up to 1-2 days earlier than current methods of diagnosis.

The latest research has been conducted by Bachelor of Medical Science (Honours) student Michael Zhu under the supervision of Professor Julian Smith, Associate Professor Roger Evans and Associate Professor Andrew Cochrane. Michael has also been supported by a Monash University Honours scholarship.

The prospective study used a feasible and relatively non-invasive technique, involving a fibre optic oximetry probe deployed in the urinary catheter, to evaluate the relationship between urinary oxygen tension (PO2) and the development of AKI after cardiac surgery requiring cardiopulmonary bypass (CPB).

The study is ongoing, with a current sample-size of 35 subjects. The data indicate that patients who later developed AKI experienced significantly longer and more severe periods of urinary hypoxia intraoperatively; with a median of 14 min per hour of surgery in the AKI group, compared to just 30 seconds per hour of surgery in the non-AKI group.

The promising study has shown that real-time monitoring of risk of AKI during cardiac surgery is feasible and may be prognostically useful. This may in-turn offer clinicians the opportunity to intervene in the operating theatre to minimise the risk of AKI.

The next step will be to investigate, in a large animal model, whether intraoperative interventions (e.g. during CPB) can result in changes in renal and urinary oxygenation. Subsequently, this may translate to strategies to reduce the risk of AKI in patients having open-heart surgery.

Michael wishes to thank his dedicated supervisors for their tremendous support throughout the Honours year. He will present his research at the upcoming Annual Scientific Meeting of the Australia and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) in Cairns.