Not So Cool After All: No CV Benefit With Lower-Temp Dialysate in Hemodialysis

Using a cooler dialysate during maintenance hemodialysis didn't provide any cardiovascular (CV) benefits, according to the cluster-randomized MyTEMP trial.

In the study of 84 dialysis centers in Ontario, patients receiving a cooler dialysate temperate (average of 35.8°C) didn't have a significantly different risk for a composite outcome of CV-related death or hospital admission with myocardial infarction, ischemic stroke, or congestive heart failure versus those receiving a standard temperature dialysate (average 36.4°C), reported Amit Garg, MD, PhD, of Victoria Hospital in London, Ontario, Canada, and colleagues.

The primary outcome occurred in 21.4% of the cooler dialysate group versus 22.4% of the standard temperature group (adjusted HR 1.00, 96% CI 0.89-1.11, P=0.93), which meant the trial's primary endpoint was missed. There also were no differences in the individual components of the primary composite outcome during the 4-year trial, they stated in the Lancet. These findings also were presented at the American Society of Nephrology Kidney Week.

And administrating a cooler dialysate didn't have a significant effect on systolic blood pressure (BP), which was a key secondary endpoint. The average drop in intradialytic systolic BP was 26.6 mmHg in the cooler group versus 27.1 mmHg in the standard temperature group (mean difference -0.5 mmHg, 99% CI -1.4 to 0.4, P=0.14).

The authors reported that no difference was seen for the risk of intradialytic hypotension between the groups.

Finally, the patients weren't too happy with their personalized cooler dialysate, as those in the cooler group were far more likely to say they were uncomfortably cold versus the standard temperature group (relative risk 1.6, 99% CI 1.1-2.5). A quarter of patients in the cooler dialysate group even said it was the "worst possible feeling."

"A lack of cardiovascular benefit, compounded by the likelihood of patient discomfort, provides no justification to adopt cooler dialysate as a center-wide policy," Garg advised medical directors of dialysis centers during the presentation.

"For nephrologists such as myself who currently use cooler dialysate in individualized patient care, the MyTEMP results provide an opportunity to reflect on practice," he added.

Garg noted that if he does prescribe cooler dialysate for certain patients, such as those with refractory intradialytic hypotension, he plans to do so "more carefully and monitor how well it is tolerated."

"I certainly would be more confident about its use in such patients if future well-conducted multicenter trials with restricted eligibility show the benefits outweigh the risks," he said.

However, Nicholas Selby, DM, and Maarten Taal, MD, both of the University of Nottingham in England, advised against tossing out the practice of cooler dialysate too quickly. In an accompanying Lancet comment, they referenced a 2106, 26-trial meta-analysis that found a 70% reduction in the rate of intradialytic hypotension with this practice.

They also questioned whether the magnitude of cooling was actually sufficient, pointing out that there was also a 20% non-compliance rate with treatment seen in both groups, and noted that there was some overlap between the groups, with some of the cooling group dialyzed at 36.5°C.

While they said MyTEMP was "impressive," its findings "should not...be interpreted as definitive evidence that cooling the dialysate is ineffective for individual patients."

A Kidney Week attendee stated that standard dialysate temperature is usually 37° in the U.S., but Garg said 36.5° is the standard in Ontario, Canada.

A total of 15,413 patients were included in the trial, representing roughly 4.3 million hemodialysis treatments. For patients randomized to the cooler group, nurses set the dialysate temperature between 0.5 to 0.9°C below each patient's measured pre-dialysis body temperature, going as low as 35.5°C. The standard group's dialysate temperature was set at 36.5°C for all treatments.