Bio-Impedance Monitoring In Patients With Intradialytic Hypertension

Abstract

Intradialytic hypertension (IDH) is regarded as the paradoxical rise in blood pressure (BP) during chronic haemodialysis (HD). IDH increases morbidity and mortality. It is suggested that IDH may be due to subclinical fluid overload, but this has not been proven. A multicentre, cross-sectional study was conducted at four HD units in the Western Cape. Cases of IDH were defined as a rise of ≥10mmHg in systolic BP between pre-dialysis and post-dialysis in at least four out of six consecutive dialysis sessions. One hundred and ninety participants were included in the final analysis. Fluid status using whole body bio-impedance measurements (Body composition monitor, Fresenius Medical Care), hourly data regarding the HD procedure, pharmacological data and demographic data were collected. There was a trend toward statistical significance regarding pre-dialysis fluid status when measured by whole body bio-impedance (mean overhydration (OH) pre-dialysis was 2.6L [95% confidence interval (CI) 1.7–3.4] in the IDH group versus (vs.) 1.8L [95% CI 1.4–2.1] in the control group; p=0.06). There was also a trend toward statistical significance in post-dialysis OH as measured by whole body bio-impedance (mean post-dialysis OH was 0.79L [95% CI -0.04–1.62] in the IDH groups vs. -0.17L [95% CI 0.52–0.18] in the control group; p=0.06). Pre-dialysis percentage extracellular water (ECW) did not achieve a significant result as measured by whole body bio-impedance (mean pre-dialysis percentage ECW was 12.3% [95% CI 8.3–16.3] vs. 9.6% [95% CI 7.8–11.5]; p=0.12) in IDH cases compared to controls. The post-dialysis results showed statistical significance with the IDH group’s mean percentage ECW decreasing to 3.5% (95% CI -1.4–8.5) compared to the control group’s mean percentage ECW of -1.4% post-dialysis (95% CI -3.7–0.8; p=0.04). There was no statistically significant difference regarding mean total ultrafiltration (UF) volume (2 274ml vs. 2 462ml; p=0.32) in the IDH vs. the control group. There was no statistically significant difference regarding mean age (57.1 years vs. 55.1 years; p=0.42), gender (males 53.7% vs. 59.5%; p=0.46), mean time-averaged sodium concentration (138.3mmol/L vs. 138.4mmol/L; p=0.72), mean dialysate calcium concentration (1.34mmol/L vs. 1.36mmol/L; p=0.45) or mode of dialysis (p=0.66) in the IDH group vs. the control group. There is a statistically significant trend towards a difference in hydration status between patients who develop IDH and patients with stable BP on dialysis. The researcher hypothesises that subclinical fluid overload may be primarily responsible in the development of IDH.