The difference between delivered and prescribed dialysate sodium in haemodialysis machines

Clinical Kidney Journal ◽

10.1093/ckj/sfaa022 ◽

2020 ◽

Author(s):

Ali M Shendi ◽

Andrew Davenport

Keyword(s):

Blood Pressure ◽

Weight Gain ◽

Blood Pressure Control ◽

Ion Chromatography ◽

Dna Delivery ◽

Pressure Control ◽

Systematic Bias ◽

Selective Electrode ◽

The Difference ◽

Dialysate Sodium

Abstract Background The choice of dialysate sodium (DNa) for haemodialysis (HD) patients remains controversial, with some studies reporting that a lower DNa improves blood pressure control and reduces intradialytic weight gain. Studies on DNa depend on the alignment of programmed to delivered DNa. We wished to determine whether there were differences between programmed and delivered DNa. Methods Dialysate samples were obtained from three dialysis machines: Fresenius 4008H (F4008H) and 5008S (F5008S) and B-Braun hemodiafiltration (HDF) Dialog+(BB). DNa was measured by indirect ion-selective electrode (ISE), flame photometry (FP) and ion chromatography (IC) at different DNa concentrations. Results We tested 18 F5008S, 18 F4008H and 31 BB machines over 153 HD treatments. The median measured minus programmed DNa was significantly greater with the BB machine [ISE, 7 (6–8); FP, 7 (6–8); IC, 6 (5–7)], followed by the F4008H [ISE, 5.5 (5–7); FP, 4 (2.25–5.75); IC, 4 (2–5)]and F5008S [ISE, 4 (2–5); FP, 1 (−1–1.75); IC, 1 (−0.5 to 2)] mEq/L (P < 0.05). At higher programmed DNa (140–145 mEq/L), measured DNa was greater for the BB and F4008 machines by all methods (P < 0.05), but only by ISE for the F5008 (P < 0.05). Conclusions We noted a systematic bias in DNa delivery with measured DNa being greater than that programmed by our HD machines. The magnitude of the bias varied between machines and with DNa. Our results may help explain the diverse results reported in studies of DNa.

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Heat-stress-induced changes in central venous pressure do not explain interindividual differences in orthostatic tolerance during heat stress

Journal of Applied Physiology ◽

10.1152/japplphysiol.00035.2011 ◽

2011 ◽

Vol 110 (5) ◽

pp. 1283-1289 ◽

Cited By ~ 18

Author(s):

R. Matthew Brothers ◽

David M. Keller ◽

Jonathan E. Wingo ◽

Matthew S. Ganio ◽

Craig G. Crandall

Keyword(s):

Blood Pressure ◽

Heat Stress ◽

Central Venous Pressure ◽

Blood Pressure Control ◽

Lower Body Negative Pressure ◽

Venous Pressure ◽

Pressure Control ◽

Stress Index ◽

Central Venous ◽

The Difference

The extent to which heat stress compromises blood pressure control is variable among individuals, with some individuals becoming very intolerant to a hypotensive challenge, such as lower body negative pressure (LBNP) while heat stressed, while others are relatively tolerant. Heat stress itself reduces indexes of ventricular filling pressure, including central venous pressure, which may be reflective of reductions in tolerance in this thermal condition. This study tested the hypothesis that the magnitude of the reduction in central venous pressure in response to heat stress alone is related to the subsequent decrement in LBNP tolerance. In 19 subjects, central hypovolemia was imposed via LBNP to presyncope in both normothermic and heat-stress conditions. Tolerance to LBNP was quantified using a cumulative stress index (CSI), and the difference between normothermic CSI and heat-stress CSI was calculated for each individual. The eight individuals with the greatest CSI difference between normothermic and heat-stress tolerances (LargeDif), and the eight individuals with the smallest CSI difference (SmallDif), were grouped together. By design, the difference in CSI between thermal conditions was greater in the LargeDif group (969 vs. 382 mmHg × min; P < 0.001). Despite this profound difference in the effect of heat stress in decreasing LBNP tolerance between groups, coupled with no difference in the rise in core body temperatures to the heat stress (LargeDif, 1.4 ± 0.1°C vs. SmallDif, 1.4 ± 0.1°C; interaction P = 0.89), the reduction in central venous pressure during heat stress alone was similar between groups (LargeDif: 5.7 ± 1.9 mmHg vs. SmallDif: 5.2 ± 2.0 mmHg; interaction P = 0.85). Contrary to the proposed hypothesis, differences in blood pressure control during LBNP are not related to differences in the magnitude of the heat-stress-induced reductions in central venous pressure.

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