Twenty-two crossover RCTs were included (n=408): 16 studies (n=235) evaluated fixed empirical temperature reductions and 6 studies (n=173) evaluated BTM.
One study reported adequate allocation concealment. Nineteen studies scored 2 out of a maximum of 5 on the Jadad scale for quality; the remaining three studies scored 1, 3 and 4, respectively. Though randomisation was generally adequate, most of the studies did not use blinding; only one was double-blinded. Most of the studies were short term and reported no drop-outs; the 4 studies that reported drop-outs only analysed data from patients who completed the study.
IDH was 7.1 times less common (95% CI: 5.3, 8.9) with cool dialysate than with standard dialysis (based on 8 studies). Statistically significant heterogeneity was found (chi-squared p<0.00001, I-squared 99.3%). The reduction in IDH was found for both fixed reductions in temperature (IDH rate 9.5 times lower, 95% CI: 6.7, 12.4; based on 6 studies; significant heterogeneity was detected, p<0.00001) and BTM (IDH rate 2.0 times lower, 95% CI: 1.9, 2.1; based on 2 studies; no significant heterogeneity). Reductions in IDH rate were smaller, but remained significant, when the 2 studies that reported zero events in the intervention group were excluded.
Compared with standard dialysis, cool dialysis was associated with significantly higher post-dialysis mean arterial pressure (MAP) (WMD of MAP 11.3 mmHg, 95% CI: 7.7, 15.0; based on 10 studies) and a significantly smaller delta MAP (WMD 7.1 mmHg, 95% CI: 4.9, 9.4; based on 7 studies). The treatment difference was no longer statistically significant when only studies evaluating BTM were pooled.
Reporting of symptoms during dialysis was generally poor. The 6 studies reporting symptoms presented no consistent ratings of severity and did not clearly report the frequency of symptoms.
Adequacy of dialysis.
There was no significant difference between cool and standard dialysis for dialysis adequacy measured using the Kt/V urea (based on 5 studies) or the urea reduction ratio (based on 2 studies).