The Evaluation of Kidney Function in Elderly Individuals Under Renin Angiotensin Aldosterone System Inhibitor Therapy

RAAS blockers in Elderly and eGFR

Abstract

Background: We aim to investigate the impact of hydration status (12-hour fasting or 12-hour water-free fasting) on the estimated glomerular filtration rate (eGFR) and serum potassium in renin-angiotensin-aldosterone (RAAS) blocker users during biochemical assessments.
Material and Methods: A total of 90 individuals were enrolled in this longitudinal study. 57 of those were advised to be hydrated for at least 1 L before the next hospital visit. 33 of 90 individuals remained in the non-hydrated group and their blood samples were evaluated following 12-hour fasting. Hypertensive patients were divided according to the antihypertensive medicine group (RAAS blockers, RAAS blockers + diuretics, and others). eGFR, serum potassium, calcium, magnesium, albumin, and glucose levels were compared between hydrated and non-hydrated individuals.
Results: The mean age was 48.21±16.59 in hydrated and 47.42±17.12 in non-hydrated groups (p=0.831). Hypertension prevalence was 59.6% in the hydrated group and 54.5% in non hydrated group. In the RAAS blocker users, following hydration, eGFR elevated up to 8-11 ml/dk (p<0.05). In the hydrated individuals with age ≥65 years and receiving RAAS blockers, the increment in eGFR was most prominent (p=0.002). Hydration increased eGFR in individuals with RAAS blockers-free and nonhypertensive, however, those increments were not statistically significant (p>0.05). Similarly, serum potassium levels decreased following hydration in RAAS blocker users (p<0.05). Hyperkalemia (serum potassium ≥ 5 mEq/L) risk decreased from 9.2 fold to 6.16 fold following hydration (p<0.05).
Conclusion: Twelve-hour fasting is associated with lower eGFR and higher serum potassium levels. An assessment of eGFR and serum potassium following hydration (12-hour water-free fasting) is beneficial for accurately assessing. This impact is more prominent in RAAS blocker users, especially in individuals ≥65 years.