COOL IT ! -New Research on dialysate temperature

Medscape Medical News

Dialysate Cooling Reduces Hemodialysis-Induced Brain Injury

Diana Phillips
September 25, 2014

Using a cooled dialysate solution protects the brains of patients receiving hemodialysis from the progressive white matter injury to which they are otherwise vulnerable, results from a new study show.

To determine the effect that hemodialysis-associated circulatory stress has on brain white matter microstructure over time and to determine whether a dialysate temperature of 0.5°C below core body temperature mitigates the potential for damage, Mohamed T. Eldehni, MD, from the Division of Medical Sciences and Graduate Entry Medicine, School of Medicine, University of Nottingham, United Kingdom, and colleagues conducted a randomized clinical trial on incident hemodialysis starting within 6 months.

Of 73 patients enrolled in the study, 37 were dialyzed with a dialysate temperature of 37°C and 36 were dialyzed with a solution cooled to 0.5°C below core body temperature. The final analysis included 19 well-matched patients in each group who had undergone diffusion tensor imaging at baseline and at 12-month follow-up.

In aggregate, patients in both groups exhibited a pattern of ischemic brain injury reflected by increased fractional anisotropy (FA) and reduced radial diffusivity (RD), the authors report in an article published online September 18 in the Journal of the American Society of Nephrology.

In the group dialyzed with the cooled solution, "[t]here were no statistically significant changes in FA, RD, or [axial diffusivity (AD)] between baseline and 12 months," the authors write. "However, the group that dialyzed at 37°C had increased FA at 12 months compared with baseline." In the latter group, the mean FA of the statistically significant voxels highlighted in the paired images increased from 0.432 at baseline to 0.452 at 12 months. Moreover, using the John Hopkins University atlas for white matter tracts, the authors "found statistically significant voxels in 18 of 20 regions represented by this atlas."

A voxel-wise analysis comparing the 2 groups at baseline and at 12 months showed no difference in FA at baseline but a significantly higher mean FA in the 37°C group than in the cooled group at 1 year, the authors state.

With respect to hemodynamic performance and brain white matter integrity, "Repeated measures [analysis of variance] showed that the group that dialyzed at 37°C had a significant increase in mean arterial pressure (MAP) extrema points frequencies at 1 year, whereas the intervention group did not," the authors write. "Furthermore, in a voxel-based analysis, the correlation between MAP extrema points frequency during HD on 1 hand and FA and RD on the other hand was examined using [tract-based spatial statistics]. Higher MAP extrema points frequencies were associated with higher FA." There was no correlation between the number of intradialytic hypotension episodes and FA, RD, or AD changes, they report.

The increased FA, decreased RD, and stable AD observed in the control patients appear to correlate with a higher frequency of change in peaks and troughs of MAP, the authors observe. "The pattern that we found in this study of increased FA and reduced RD is rather unexpected, because these changes have been described in acute ischemic stroke within <24 hours. The [magnetic resonance] imaging at baseline and follow-up was performed on a nondialysis day within <24 hours from the dialysis session, and therefore, it is plausible that our findings — indicating acute ischemia — are related to the previous dialysis session, which then was exacerbated over 1 year of [hemodialysis] treatment." This finding supports the hypothesis that patients receiving hemodialysis are susceptible to recurrent acute ischemic brain insults that result from hemodialysis-induced circulatory stress, which is similar to findings previously observed in the myocardium, they note.

The absence of changes in brain white matter FA, AD, or RD in the cooled solution group at 1 year, and the stability of the MAP extrema points frequencies during the same period, suggest that reducing the dialysate temperature "seems to have a significant effect on hemodynamic stability, organ perfusion, and end organ damage in this population, which is burdened with impaired hemodynamic regulatory functions," the authors write.

On the basis of these findings, the authors suggest this study "justifies additional larger-scale testing of dialysis-based interventions to reduce the burden of morbidity and mortality in [hemodialysis]."

The authors have disclosed no relevant financial relationships.