Salt intake
Volume expansion, net positive sodium balance, renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system activation contribute to high BP in people on dialysis (40). Lifestyle interventions that attenuate these effects may have some impact on BP control.
Volume expansion by salt and water is thought to be a major contributor to hypertension in people on dialysis (41, 42). Higher dietary sodium intake is independently associated with greater mortality in people on haemodialysis (43). Reduction in salt intake lowers BP in the general population, in hypertensives of all ethnicities, in people with and without diabetes and in people with chronic kidney disease (CKD) (44-48). A low salt diet may be particularly beneficial in people on dialysis because they are largely dependent on the dialysis process to remove excess sodium and water. Studies in the 1990s explored dietary salt reduction together with dialysis interventions to achieve optimal dry weight and BP control (49-51). The studies reported to date, however, are poorly designed, uncontrolled and underpowered to show a BP difference following dietary interventions. A meta-analysis of randomized controlled trials in 91 haemodialysis patients has shown that a mean difference in salt intake of 5 g/day was associated with a reduction in BP of 8/4 mmHg (95% CI 4.8 to 12/2.2 to 6.6) (52). A subsequent systematic review and meta-analysis of salt reduction in all stages of CKD included 5 studies in haemodialysis patients and found reducing salt intake reduced systolic BP by 6.32 mmHg (95% CI -11.04 to -1.60) and diastolic BP by 3.46 mm Hg (95% CI -6.39 to -0.54) (53).
Fluid restriction
Volume overload is a risk factor for mortality amongst dialysis patients (54). Efforts to achieve ideal target weight are discussed in other sections of this guideline, some of which will involve salt and water restriction, increased ultrafiltration and longer dialysis times to facilitate achieving euvolaemia. There is an acceptance that fluid restriction requires concomitant salt intake reduction, but evidence for fluid restriction alone lacks any contemporary evidence base (55).
Other dietary approaches
There is good evidence in the general population that a diet high in fruits and vegetables such as the Dietary Approaches to Stop Hypertension (DASH) diet can help to lower BP (46, 56). However, trials in people on dialysis are lacking. An observational cross-sectional study in 2022 assessed the diets of 583 individuals on haemodialysis and categorized according to adherence to the DASH diet (57). Higher adherence to the DASH diet was associated with lower serum potassium levels, although no difference in BP was observed between the groups (personal communication with author). This study allays concerns that a DASH diet may lead to hyperkalaemia and paves the way for further research.
Several authors have investigated diets rich in polyphenols. A systematic review of three trials found a reduction in DBP but not SBP (58). Another small study has reported a reduction in SBP and DBP with pomegranate juice (59). Due the small number of trials with low numbers the evidence is not strong enough to make a recommendation.
Although there is a lack of evidence in the dialysis population, we suggest that other lifestyle measures to control BP are adopted including maintenance of ideal body weight, excessive intake of alcohol, coffee and caffeine rich foods and drinks should be discouraged as per advice for the general population with hypertension. We also suggest that specialist renal dietitians are best placed to provide dietary advice to those on dialysis. Patients on dialysis have complex dietary requirements and renal dietitians can provide individualized, holistic advice.
Exercise
A number of systematic reviews and meta-analyses have considered whether exercise reduces BP in dialysis. Most studies have focused on intra-dialytic exercise.
In a 2019 meta-analysis of intradialytic exercise trials that included BP as an outcome, there was a significant reduction in SBP of 4.87 mmHg (95% CI -9.2 to -0.5, p=0.03) and DBP of 4.11 mmHg (95% CI -6.5 to -1.72, p=0.0007) (60). In another meta-analysis of intradialytic exercise, the effect of aerobic exercise and combined exercise (aerobic and strength) were analysed separately. The authors found a significant reduction in SBP of 10.07 mmHg (95% CI –16.36 to –3.78) with aerobic exercise and a reduction in DBP of 5.76 mmHg (95% CI -2.7 to -8.83) with combined exercise, but there was no reduction in SBP with combined exercise or DBP with aerobic exercise (61).
Other meta-analyses have explored the effects of all types of exercise, intradialytic exercise, exercise on non-dialysis days, aerobic and combined strength and aerobic, on BP in dialysis populations. One included 16 studies of at least 8 weeks and found that only combined training reduced BP. SBP was reduced by 9 mmHg (95% CI -13 to -4) and DBP by 5 mmHg (95% CI -6 to -3) (62). The other considered whether the intensity of exercise was important. Moderate to vigorous exercise was found to be most effective at reducing SBP by 8.8 mmHg (95% CI -17 to -1.6) and DBP by 4.9 mmHg (95% CI –9.9 to –0.4) (63). Both meta-analyses suggest that combined training was the most effective.
The most comprehensive report on exercise in dialysis populations is a 2022 Cochrane systematic review of RCTs and quasi-RCTs of any structured exercise programs of eight weeks or more in adults undergoing maintenance dialysis compared to no exercise or sham exercise (64). The authors report uncertainty as to whether exercise training reduces the risk of death and no studies reported CV events. They found that exercise training was likely to improve functional capacity and depressive symptoms with some degree of certainty. The effects of exercise on BP were analysed in smaller meta-analyses, which considered different types of exercise regimens separately. There was a significant reduction in SBP 8.69 mmHg (95% CI -13.69 to -3.69) and DBP 4.45 mmHg (95% CI -5.98 to -2.91)- with combined exercise, but authors consider the results are of very low certainty due to the high risk of bias, the short duration of the interventions and follow-up and the low number of participants in the included studies. There was no significant reduction in BP with aerobic exercise alone. We are unable to make any recommendations for exercise reducing BP in PD patients due to the lack of evidence.
Self-care engagement
Achieving BP targets is notoriously difficult for a combination of reasons. Some small studies have reported recently that explore the impact of interventions on adherence to diet, fluid and BP medications (65). An educative nursing intervention in 118 participants recruited from 6 haemodialysis units in the USA found that BP education sessions, with home BP monitoring twice daily, diarising salt and fluid intake weekly for a 12-week period vs. standard care with BP monitoring and medication adjustment by health care providers on a weekly basis in the haemodialysis unit significantly decreased both SBP and DBP in the treatment group. Another non-controlled study has reported a greater likelihood of reduction in SBP in a cohort of 58 haemodialysis patients, who received counselling from a pharmacist on adherence to BP medications (66). We considered that these studies are not sufficient to make a recommendation on the role of supportive care interventions in BP management of dialysis patients, but measures to support adherence to treatment goals is possibly an area for further research.