Intradialytic hypotension (IDH) is a frequent complication of haemodialysis. Reducing the temperature of the dialysis fluid is a simple therapeutic strategy but is relatively underused. This may be due to concerns regarding its effects on symptoms and dialysis adequacy. We performed a systematic review of the literature to examine the effects of cool dialysis on intradialytic blood pressure, and to assess its safety in terms of thermal symptoms and small solute clearance. We searched the Cochrane Central Register of Controlled Trials, Medline, Embase, Cumulative Index to Nursing and Allied Health Literature, databases of ongoing trials, the contents of four major renal journals as well as hand-searching reference lists. We included all prospective randomized studies that compared any technique of reducing dialysate temperature with standard bicarbonate dialysis. These techniques included an empirical, fixed reduction of dialysate temperature or use of a biofeedback temperature-control device (BTM) to deliver isothermic dialysis or programmed patient cooling. A total of 22 studies comprising 408 patients were included (16 studies examined a fixed empirical temperature reduction and six examined BTM). All studies were of crossover design and relatively short duration. IDH occurred 7.1 (95% CI, 5.3-8.9) times less frequently with cool dialysis (both fixed reduction and BTM). Post-dialysis mean arterial pressure was higher with cool-temperature dialysis by 11.3 mmHg (95% CI, 7.7-15.0). No studies reported that cool dialysis led to a reduction in dialysis adequacy as assessed by urea clearance. The frequency and severity of thermal-related symptoms were generally reported inadequately. Reducing the temperature of the dialysate is an effective intervention to reduce the frequency of IDH and does not adversely affect dialysis adequacy. This applies to the fixed reduction of dialysate temperature and BTM. It remains unclear as to what extent cool-temperature dialysis causes intolerable cold symptoms during dialysis. There are no trials comparing fixed empirical temperature reduction with BTM, and no trials examining the long-term effects of cool dialysis on patient outcomes.
