Impaired kidney function is strongly associated with increased risk of stroke and dementia. Some of this risk may relate to dialysis which is a procedure that removes waste products and excess fluid from the blood when the kidneys stop working properly. This is a therapy that is frequently required in the intensive care unit (ICU) for patients who are critically ill. However, it is not known how dialysis affects the blood flow in the brain, whether it may generate some small air bubbles that reach the brain during the dialysis session and whether these events may subsequently increase the risk of stroke.

Therefore, the aim of our study is to investigate the impact of continuous dialysis therapy on brain blood flow in a group of patients with acute kidney injury in the ICU. We will explore whether these dialysis sessions generate frequent air bubbles in the brain and whether there is then a higher risk of stroke or delirium in this setting.

We will include all critically ill patients treated with continuous dialysis in the general ICU and neurocritical care unit in the John Radcliffe Hospital, Oxford, between the 1st September 2023 and 1st September 2024. We will perform transcranial Doppler ultrasound measurements during the dialysis sessions. This is a non-invasive test that uses sound waves to examine blood flow in the brain. We will also perform some routine clinical examinations to evaluate for neurological and cognitive disturbances. We will record any stroke or delirium events that may occur as well as the results of brain imaging tests performed.

Since up to one in four patients in the ICU are in receipt of continuous dialysis therapy, this study will address an important gap in our knowledge. If we uncover a negative impact of dialysis on brain health, we will need to conduct larger studies and trials to find ways to make dialysis safer for patients in the future.

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