Effects of Dietary Sodium Restriction in Kidney Transplant Recipients Treated With Renin-Angiotensin-Aldosterone System Blockade: A Randomized Clinical Trial

Abstract

Background: In patients with chronic kidney disease receiving renin-angiotensin-aldosterone system (RAAS) blockade, dietary sodium restriction is an often-used treatment strategy to reduce blood pressure (BP) and albuminuria. Whether these effects extend to kidney transplant recipients is unknown. We therefore studied the effects of dietary sodium restriction on BP and urinary albumin excretion (UAE) in kidney transplant recipients receiving RAAS blockade.

Study design: Two-center randomized crossover trial.

Setting & participants: Stable outpatient kidney transplant recipients with creatinine clearance > 30mL/min, BP ≥120/80mmHg, receiving stable RAAS blockade therapy.

Intervention: 6-week regular-sodium diet (target, 150mmol/24 h) and a 6-week low-sodium diet (target, 50mmol/24 h).

Outcomes & measurements: Main outcome parameters were systolic and diastolic BP, UAE, and estimated glomerular filtration rate (eGFR) at the end of each diet period. Dietary adherence was assessed by 24-hour urinary sodium excretion.

Results: We randomly assigned 23 kidney transplant recipients, of whom 22 (mean age, 58±8 [SD] years; 50% men; mean eGFR, 51±21mL/min/1.73m(2)) completed the study. One patient withdrew from the study because of concerns regarding orthostatic hypotension on the low-sodium diet. Sodium excretion decreased from 164±50mmol/24 h during the regular-sodium diet to 87±55mmol/24 h during the low-sodium diet (mean difference, -77 [95% CI, -110 to -44] mmol/24 h; P<0.001). Sodium restriction significantly reduced systolic BP from 140±14 to 129±12mmHg (mean difference, -11 [95% CI, -14 to -7] mmHg; P<0.001), diastolic BP from 86±8 to 79±8mmHg (mean difference, -7 [95% CI, -10 to -5] mmHg; P<0.001). We found no significant effect on natural log (ln)-transformed UAE (mean difference, -0.03 [95% CI, -0.6 to 0.6] ln(mg/24 h); P=0.9) or eGFR.

Limitations: No hard end points; small study; small proportion of patients willing to test the intervention; adherence to sodium diet was achieved in 86% of patients.

Conclusions: In stable kidney transplant recipients receiving RAAS blockade, dietary sodium restriction effectively reduces BP without affecting eGFR. Dietary sodium restriction is relevant to BP management in kidney transplant recipients receiving RAAS blockade.

Keywords: Kidney transplantation; RAAS blockade; albuminuria; antihypertensive treatment; antiproteinuric treatment; blood pressure; clinical trial; cross-over trial; diet; dietary sodium restriction; hypertension; lifestyle intervention; randomized trial; renal transplant recipients; renin-angiotensin-aldosterone system (RAAS); urinary albumin excretion.