Dialysate Cooling May Help Protect Against Brain Damage

Dialysate Cooling May Help Protect Against Brain Damage

Hemodialysis can cause significant circulatory stress that negatively affects various organs, including the heart and brain. New research indicates that cooling dialysis fluids can protect against blood pressure changes that damage the brain. The findings, published in the Journal of the American Society of Nephrology, offer a simple and inexpensive way to improve dialysis care.

“This study demonstrates that paying attention to improving the tolerability of dialysis treatment—in this case by the simple and safe intervention of reducing the temperature of dialysate—does not just make patients feel better, but also can completely protect the brain from progressive damage,” said senior author Christopher McIntyre, DM.

Through their investigations into the adverse consequences of hemodialysis treatment, McIntyre and his team noted that circulatory effects of hemodialysis are likely caused by hemodynamic factors that lead to perfusion anomalies in vulnerable vascular beds.

Their previous work demonstrated a link between hemodialysis and significant reductions in myocardial blood flow. Through a systematic review of the literature, they found that reducing the temperature of the dialysate is an effective intervention to reduce the frequency of intradialytic hypotension and does not adversely affect dialysis adequacy (Selby NM, McIntyre CW. Nephrol Dial Transplant 2006; 21(7):1883–1898). Intradialytic hypotension occurred 7.1 times less frequently with cool dialysis, and average post-dialysis arterial pressure was higher with cool-temperature dialysis by 11.3 mm Hg. None of the studies reviewed reported that cool dialysis led to a reduction in dialysis adequacy as assessed by urea clearance.

In this latest work, McIntyre and his colleagues looked to see if dialysate cooling might also have measurable beneficial effects on the brain. McIntyre was at the University of Nottingham in the UK while conducting this work but is now at the University of Western Ontario and the London Health Sciences Centre, in Canada. He noted that cognitive, psychological, and functional difficulties are present in many hemodialysis patients, with some experiencing deficiencies in memory, executive function, and language.

The team sought to characterize hemodialysis-induced brain injury by studying the effects of the treatment on brain white matter microstructure, as well as to determine whether dialysate cooling could provide protection against hemodialysis-associated brain injury. The researchers randomized 73 incident hemodialysis patients starting within 6 months to dialyze with a dialysate temperature of either 37° C or 0.5° C below the core body temperature. Patients were followed for one year.

Diffusion tensor magnetic resonance imaging tests revealed that hemodialysis patients exhibited a pattern of brain injury similar to that described in acute ischemic stroke: increased fractional anisotropy and reduced radial diffusivity. Therefore, hemodialysis patients may be susceptible to recurrent acute ischemic brain insults due to dialysis-induced circulatory stress, analogous to that observed previously in the muscular tissue of the heart.

“This is the first study to show that hemodialysis drives progressive white matter brain injury, and that the extent of this is proportional to the degree of dialysis-induced blood pressure instability,” McIntyre said. “This provides a plausible biological basis for cognitive dysfunction, increasing dependency, and potentially depression.”

The researchers found that simply dialyzing at 0.5° C below core body temperature completely protected against white matter changes at one year. No patients withdrew from the study owing to lack of treatment tolerability, and absolute brain protection was evident even when applying the most sensitive measures of detecting injury.

McIntyre noted that the study was limited to patients new to dialysis. He said it is unclear if the protective effects would also be seen in patients who have been receiving dialysis long-term and who may already be experiencing cognitive and other difficulties. Also, the study was relatively small in size and needs to be followed up by larger and longer studies to accurately assess the impact of this approach.

“The paper significantly extends our knowledge on the advantages derived from reducing the dialysate temperature in patients during hemodialysis,” said Fresenius Medical Care’s Ciro Tetta, MD, who was not involved with the research. “Further studies will need to relate this protection on brain white matter changes to a lesser incidence of neurologic and psychiatric disorders in the hemodialysis population.”