Acid-Base Balance in Peritoneal Dialysis Patients: A Stewart-Fencl Analysis

Figures & data

Table 1  Biochemical characteristics of the study group and control group

	PD patients, median (min-max)	HV, median(min-max)
pH^§	7.41 (7.27–7.48)	7.45 (7.39–7.48)
HCO3^− (mmol/L)^§	23.7 (17.6–29.5)	24.3 (20.0–26.6)
pCO2 (kPa)^§	5.1 (4.6–5.7)	4.9 (3.9–5.7)
Base excess (mmol/L)^§	−0.2 (−8.3–5.9)	0.1 (−2.5–2.4)
Anion gap (mmol/L)	20.2 (16.0–24.9)^†	18.2 (11.3–21.4)
Anion gap corrected for albumin phosphates and lactate (mmol/L)	12.48 (9.48–17.77)^‡	8.43 (1.74–13.27)
Anion gap corrected for albumin (mmol/L)	20.68 (18.43–25.80)^‡	16.33 (9.88–20.78)
Difference between anion gap and charge carried by albumin (mmol/L)	8.78 (7.12–14.50)^‡	4.22 (−1.98–8.71)
Lactate (mmol/L)	1.43 (0.99–2.46)	1.06 (0.76–2.81)
Strong ion difference (mmol/L)	36.26 (29.49–41.32)^†	39.29 (35.31–42.46)
Sodium–chloride difference (mmol/L)	39.0 (31.0–44.0)	37.0 (31.0–40.0)
Undetermined anions (mmol/L)	9.10 (6.02–14.01)^‡	5.41 (−0.56–9.54)
Sodium (mmol/L)	138 (134–143)^†	141 (139–145)
Chlorides (mmol/L)	100 (93–112)^‡	103 (101–109)
Potassium (mmol/L)	4.2 (3.3–4.8)	4.1 (3.6–4.6)
Calcium total (mmol/L)	2.22 (1.72–2.64)	2.30 (2.17–2.49)
Ionized calcium (mmol/L)^§	0.98 (0.49–1.35)^‡	1.19 (1.00–1.34)
Magnesium (mmol/L)	0.86 (0.62–1.09)	0.89 (0.78–1.05)
Albumin (g/L)	39.7 (28.8–43.4)^‡	49.0 (45.4–53.5)
Inorganic phosphates (mmol/L)	1.60 (0.83–2.54)^‡	1.12 (0.92–1.43)
Creatinine (μmol/L)	612 (358–1200)^‡	87 (65–105)
Urea (mmol/L)	15.5 (8.6–34.6)^‡	4.7 (3.3–6.3)
Residual renal function (mL/min)	5.62 (0–10.25)	—
Kt/V urea	1.93 (1.33–3.64)	—
Total weekly creatinine clearance (L/1.73 m^2)	87.95 (36.08–142.85)	—
Dialysate-to-plasma creatinine ratio; hour 4 of the peritoneal equilibration test	0.78 (0.60–0.85)	—
Mass transfer area coefficient (mL/min)	13.44 (8.54–17.75)	—

Difference between groups: *p < 0.05, ^†p < 0.01, ^‡p < 0.001.

^§Capillary blood.

Figure 1.  Correlation between bicarbonate in blood and strong ion difference. Spearman's rank order correlation test. Abbreviations: SID = strong ion difference, [HCO₃⁻] = bicarbonate in blood.

Figure 2.  Correlation between bicarbonate in blood and sodium-chloride difference. Spearman's rank order correlation test. Abbreviation: [HCO₃−] = bicarbonate in blood.

Figure 3.  Correlation between undetermined anions and difference between anion gap and charge carried by albumin. Spearman's rank order correlation test. Abbreviations: AG-Alb⁻ difference = difference between anion gap and charge carried by albumin, [UA⁻] = undetermined anions.

Table 2  Additional significant correlations of investigated parameters

N = 17	Rho	p
[HCO3^−] × [SID]	0.823	<0.001
[HCO3^−] × [Na^+−Cl−] difference	0.649	<0.01
[SID] × [Na^+−Cl^−] difference	0.653	<0.01
[UA^−] × AG − Alb^− difference	0.931	<0.001
pH × [SID]	0.646	<0.01
pH × [Na^+−Cl^−] difference	0.466	0.0580
[HCO3^− ] × RRF	−0.517	<0.05

*This correlation was close to reaching statistical significance.

Abbreviations: SID = strong ion difference, [Na⁺−Cl⁻] difference = sodium–chloride difference, [UA⁻] = undetermined anions, AG = anion gap, AG − Alb⁻ difference = difference between anion gap and charge carried by albumin, RRF = residual renal function.