Extracellular water/total body water ratio as predictor of mortality in hemodialysis patients

Figures & data

Table 1. Comparison of excluded/included clinical and demographic characteristics of the patients.

	Cases n = 60	Excluded n = 110	p-Value
Age (years)	72 ± 11	67 ± 15	0.04
Sex (male) – no. (%)	44 (73.3)	70 (63)	0.20
Height (cm)	167 ± 9	166 ± 9	0.43
Body mass index	26.87 ± 4.48	26.9 ± 4.49	0.92
Hypertension – no. (%)	50 (84.7)	81 (87.1)	0.68
Diabetes mellitus – no. (%)	33(55)	56 (60.2)	0.75
Smoking status – no. (%)	12 (20)	15 (16.1)	0.86

Table 2. Correlation between NT-proBNP and hydration ratios pre and post-dialysis.

	ECW/TBW pre-dialysis	ECW/TBW post-dialysis	E/I pre-dialysis	E/1 post-dialysis
NT-proBNP
Rho	0.32	0.48	0.32	0.48
p	0.01	<0.001	0.01	<0.001
cTnT
Rho	0.21	0.45	0.21	0.45
p	0.12	<0.001	0.11	<0.001
IL-6
Rho	0.01	0.13	0.02	0.13
p	0.96	0.33	0.89	0.33

TBW: total body water; ECW: extracellular water; ICW: intracellular water; NT-proBNP: N-terminal pro-brain natriuretic peptide; cTnT: Troponin T; IL-6: Interleukin 6.

Table 3. Biomarker levels and ECW/TBW ratio cutoff for global and cardiovascular mortality.

Cardiovascular mortality
ECW/TBW ratio cutoff	<0.4713	≥0.4713	p
NT-proBNP	1588 (704–4177)	5324 (2795.3 − 14,566)	0.001
cTnT	34.6 (24 − 49.4)	67.9 (48.3–91.9)	<0.001
IL-6	5.7(3.2 − 9.9)	6.5 (2.9 − 10.9)	0.54
Global mortality
ECW/TBW ratio cutoff	<0.5023	≥0.5023	p
NT-proBNP	3084 (1529–6392.8)	7076.5 (3436.5–17,808)	0.02
cTnT	53.4 (35.2–77.2)	67.9 (51.6–92.7)	0.05
IL-6	6.1 (2.8–10.2)	3.1 (6.4–11.5)	0.77

Results are expressed with median (P₂₅–P₇₅).

Table 4. Demographic and clinical characteristics of the 60 patients included in the study, survivors and non survivors.

	Cohort n = 60	Survivors n = 32	Non survivors n = 28	p
Sex (men) – n (%)	44 (73.3)	24 (75)	20 (71.4)	0.76
Age (years)	71.8 ± 11.3	67.9 ± 11.2	76.3 ± 9.9	0.004
Cardiovascular background-n (%)
Hypertension	50 (83.3)	29 (90.6)	21 (75)	0.17
Diabetes mellitus	33 (55)	17 (53.1)	16 (57.1)	0.75
Previous cardiovascular events	41 (68.3)	19 (59.4)	22 (78.6)	0.11
Arrhythmia	5 (8.3)	2 (6.3)	3 (10.7)	0.66
Coronary heart disease	11 (18.3)	2 (6.3)	9 (32.1)	0.010
Congestive heart failure	11(18.3)	1 (3.1)	10 (35.7)	0.001
Cerebrovascular disease	16(26.7)	9 (28.1)	7 (25)	0.78
Peripheral vascular disease	20 (33.3)	7 (21.9)	13 (46.4)	0.003
Toxic habits – n (%)
Smoking:
Never	32(53.3)	21 (65.6)	11 (39.3)	0.95
Former smoker	16(26.7)	6 (18.8)	10 (35.7)
Smoker	12(20)	5 (15.6)	7 (25.5)
Alcoholism:
Never	43(71.7)	21(65.6)	22 (78.6)	0.47
Former drinker	7(11.7)	4 (12.5)	3 (42.9)
Active drinker	10(16.7)	7(21.9)	3 (10.7)
Etiology of renal disease – n (%)
Diabetic nephropathy	25(41.7)	13 (40.6)	12 (42.9)	0.81
Unknown	12 (20)	6 (18.8)	6 (21.4)
Nephroangiosclerosis	7 (11.7)	5 (15.6)	2 (7.1)
Polycystic renal disease	6 (10)	3 (9.4)	3 (10.7)
Ischemic nephropathy	6 (10)	2 (6.3)	4 (14.3)
Tubule-interstitial nephropathy	2 (3.3)	1 (3.1)	1 (3.6)
IgA glomerulonephritis	1(1.7)	1 (3.1)	0 (0)
IgG glomerulonephritis	1(1.7)	1 (3.1)	0 (0)
Blood pressure (mmHg)
Systolic	137.72 ± 23.89	139.7 ± 20.9	135.46 ± 27.05	0.50
Diastolic	73.28 ± 16.22	77.7 ± 16.05	68.25 ± 15.16	0.023
Pharmacological treatment – n (%)
Antihypertensive	39 (65)	20 (62.5)	19 (67.9)	0.66
Lipid-lowering	39 (65)	21 (65.6)	18 (64.3)	0.91
Erithropoiesis stimulating agents	51 (85)	25 (80.6)	26 (92.9)	0.162
Iron therapy	38 (63.3)	15 (46.9)	23 (82.1)	0.005
Dialysis vintage	52.33 ± 30.83	51.06 ± 30.3	53.79 ± 31.9	0.694
Dialysis session time – n (%)
Less than 12 h	2 (3.3)	0 (0)	2 (7.1)	0.232
12 h	48 (80)	25 (78.1)	23 (82.1)
More than 12 h	10 (16.7)	7 (21.9)	3 (10.7)
Kt /V – n (%)
Under 1.3	11(18.3)	5 (15.6)	6 (21.4)	0.562
Greater than 1.3	49(81.7)	27 (84.4)	22 (78.6)
EPO resistance index – n (%)	10(16.7)	3 (9.4)	7 (25)	0.046
Vascular access - n (%)
Cuffed catheter	8(13.3)	5 (15.6)	3 (10.7)	0.42
Autologous arteriovenous fistula	50(83.3)	26 (81.3)	24 (85.7)
Prosthetic arteriovenous fistula	2(3.3)	1 (3.1)	1 (3.6)
Type of hemodialysis – n (%)
Standard	59(98.3)	31 (96.9)	28 (47.6)	0.34
On-line	1(1.7)	1 (3.1)	0 (0)
RFO	0.10 ± 0.114	0.087 ± 0.112	0.12 ± 0.115	0.15

RFO: relative fluid overload.

Table 5. Relationship between hydration parameters measured by bioimpedance in survivors and non survivors.

	Survivors (n = 32)	Non Survivors (n = 28)	p
TBW [L] pre-dialysis	36 ± 6.7	33 ± 5.2	0.02
ECW [L] pre-dialysis	18 ± 3.6	17 ± 2.3	0.13
ICW [L] pre-dialysis	18 ± 3.7	16 ± 3.5	0.006
TBW [L] post-dialysis	34 ± 6.0	30 ± 4.5	0.01
ECW [L] post-dialysis	16 ± 3.0	15 ± 2.2	0.14
ICW [L] post-dialysis	18 ± 3.5	15 ± 2.8	0.003
ECW/TBW pre-dialysis	0.492 ± 0.039	0.499 ± 0.049	0.07
ECW/TBW post-dialysis	0.479 ± 0.0366	0.508 ± 0.035	0.006

TBW: total body water; ECW: extracellular water; ICW: intracellular water; SD: standard deviation.

Figure 1. ROC curve for ECW/TBW using death as event.

Figure 2. Kaplan–Meier survival curves using the cutoff ECW/TBW >0.5023. as predictor and death as outcome.

Figure 3. ROC curve for ECW/TBW using cardiovascular death as event.

Figure 4. Kaplan–Meier survival curves using the cutoff ECW/TBW >0.4713 as predictor and death as outcome.

Table 6. Partial Cox regression models to predict global mortality using an ECW/TBW post-dialysis cutoff value higher than 0.5023 as the main independent variable.

	Hazard ratio	95% CI	p
Model 1
ECW/TBW >0.5023	2.46	1.16–5.20	0.02
Model 2
ECW/TBW >0.5023	2.05	0.94–4.48	0.07
Age (years)	1.03	0.99–1.08	0.15
Model 3
ECW/TBW >0.5023	2.05	0.93–4.48	0.07
Charlson Index	1.19	0.96–1.46	0.11
Model 4
ECW/TBW >0.5023	2.01	0.91–4.47	0.09
Charlson Index	1.18	0.94–1.47	0.15
Time in hemodialysis (months)	0.90	0.35–2.33	0.83

Data availability statement

Materials described in the manuscript, including all relevant raw data, will be freely available to any scientist wishing to use them for noncommercial purposes, without breaching participant confidentiality.