Relationship between bioimpedance-determined body composition and peritoneal transport in peritoneal dialysis

The centre-calculated cutoff value is better for identifying fast peritoneal solute transfer of patients on peritoneal dialysis than the traditional value: a retrospective cohort study

Background

The mean 4-h dialysate to plasma ratio of creatinine (4-h D/Pcr) is a vital cutoff value for recognizing the fast peritoneal solute transfer rate (PSTR) in patients on peritoneal dialysis (PD); however, it shows a noticeable centre effect. We aimed to investigate our centre-calculated cutoff value (CCV) of 4-h D/Pcr and compare it with the traditional cutoff value (TCV) (0.65).

Methods

In this study, we enrolled incident PD patients at our centre from 2008 to 2019, and divided them into fast or non-fast PSTR groups according to baseline 4-h D/Pcr-based CCV or TCV. We compared the efficiency of the fast PSTR recognized by two cutoff values in predicting mortality, ultrafiltration (UF) insufficiency and technical survival.

Results

In total, 1905 patients were enrolled, with a mean 4-h D/Pcr of 0.71 ± 0.11. Compared with TCV (0.65), CCV (0.71) showed superiority in predicting mortality of PD patients [hazard ratio (HR) 1.27, 95% confidence interval (CI) 1.02-1.59 vs HR 1.24, 95% CI 0.97-1.59]. The odds ratio (OR) of the fast PSTR in centre classification was slightly higher than traditional classification in predicting UF insufficiency (OR 1.67, 95% CI 1.25-2.24 vs OR 1.60, 95% CI 1.15-2.22). Additionally, the restricted cubic splines 4-h D/Pcr has an S-shaped association with mortality and UF insufficiency, and the inflection points of 4-h D/Pcr were 0.71 (equal to CCV).

Conclusions

The CCV of 4-h D/Pcr for identifying fast PSTR was 0.71. It was superior to TCV in predicting mortality and UF insufficiency.

Monitoring of Intraperitoneal Fluid Volume during Peritoneal Equilibration Testing using Segmental Bioimpedance

BACKGROUND

Ultrafiltration failure and fluid overload are common in peritoneal dialysis (PD) patients. Knowledge of intraperitoneal volume (IPV) and time to peak IPV during a dwell would permit improved PD prescription. This study aimed to utilize trunk segmental bioimpedance analysis (SBIA) to quasi-continuously monitor IPV (IPVSBIA) during the peritoneal dwell.

METHODS

IPVSBIA was measured every minute using lower-trunk SBIA (Hydra 4200; Xitron Technologies Inc., CA, USA) in 10 PD patients during a standard 240-min peritoneal equilibration test (PET). The known dialysate volume (2 L) rendered IPVSBIA calibration and calculation of instantaneous ultrafiltration volume (UFVSBIA) possible. UFVSBIA was defined as IPVSBIA - 2 L.

RESULTS

Based on dialysate-to-plasma creatinine ratio, 2 patients were high, 7 high-average, and 1 low-average transporters. Technically sound IPVSBIA measurements were obtained in 9 patients (age 59.0 ± 8.8 years, 7 females, 5 African Americans). Drained ultrafiltration volume (UFVdrain) was 0.47 ± 0.21 L and correlated (r = 0.74; p < 0.05) with end-dwell UFVSBIA (0.55 ± 0.17 L). Peak UFVSBIA was 1.04 ± 0.32 L, it was reached 177 ± 61 min into the dwell and exceeded end-dwell UFVSBIA by 0.49 ± 0.28 L (95% CI: 0.27-0.7) and UFVdrain by 0.52 ± 0.31 L (95% CI: 0.29-0.76), respectively.

CONCLUSION

This pilot study demonstrates the feasibility of trunk segmental bioimpedance to quasi-continuously monitor IPVSBIA and identify the time to peak UFVSBIA during a standard PET. Such new insights into the dynamics of intraperitoneal fluid volume during the dwell may advance our understanding of the underlying transport physiology and eventually assist in improving PD treatment prescriptions.