Supine equilibration of extracellular fluid in peritoneal dialysis varies with intra-abdominal pressure

BACKGROUND

Increased intra-abdominal pressure (PIA) leads to venous congestion in splanchnic and adjoining circulations. The aim is to examine whether PIA in peritoneal dialysis (PD) affects the mobilization of extracellular fluid from the lower body in supine body position.

METHODS

Patients were studied during a regular peritoneal equilibration test (PET) in supine body position using multifrequency bioimpedance analysis to determine extracellular resistance and absolute volume overload (AVO) in wrist-to-ankle (W2A) as well as in ankle-to-ankle (A2A) configurations. Measurements were taken at baseline (T0) after draining the peritoneal cavity, at T1 shortly after filling with 2 L of standard dialysate, and at T2 before taking the 2 h PET samples. PIA was measured from the column height in the PD catheter. Extracellular resistance in the lower extremities (RL) was taken as half of the A2A resistance.

RESULTS

Eighteen patients (56 ± 15 years, 76 ± 21 kg, body mass index (BMI) 26.4 ± 7 kg/m², 13 men) were studied. After having assumed a supine body position for the duration of 17, 77, and 155 min, AVO continuously decreased from 1.6 ± 1.3 (T0) to 1.2 ± 1.5 (T1) and 1.0 ± 1.4 L (T2). RL significantly increased from 238 ± 57 (T0) to 254 ± 62 (T1) and 264 ± 67 Ohm (T2). This increase was negatively correlated to BMI and PIA measured at any time point, but not to net ultrafiltration volume.

CONCLUSIONS

Orthostatic fluid shifts from the lower limbs may take up to 2 h in supine PD patients, especially with high BMI and PIA because of venous congestion in splanchnic and adjoining circulations.

The Influence of Colloid Osmotic Pressure on Hydrostatic Pressures in High- and Low-Flux Hemodialyzers

The aim of this study was to examine the relationship between hydrostatic trans-membrane pressure (TMP_h ) and colloid osmotic pressure (COP) in low-flux (LF) and high-flux (HF) dialyzers. Hydrostatic pressures were measured in dialyzers distinguished by their ultrafiltration coefficient K_uf (16 and 85 mL/h/mm Hg) under constant dialysate flow and variable blood flow (Q_b ) ranging from 0 to 400 mL/min using (i) alginate (70 kDa) dissolved in dialysate, (ii) diluted, undiluted, and concentrated plasma, or (iii) whole blood at different hematocrit, all in absence of ultrafiltration (UF). For a given fluid, TMP_h linearly increased with increasing Q_b . The intercept of the linear TMP_h to Q_b relationship correlated with measured COP with an average bias of 1.00 ± 2.26 mm Hg and a concordance correlation coefficient of 0.98. The slope of the linear TMP_h to Q_b relationship increased with increasing sample viscosity and was much larger in HF dialyzers under otherwise identical operating conditions, most likely because of increased internal filtration. The TMP_h to Q_b relationship measured in dialyzers in absence of UF can be described by the intercept related to measured COP and the slope related to internal filtration. This relationship could be of interest to estimate internal filtration and COP under in vivo conditions.

Osmotic and Hemodynamic Effects of Hypertonic Glucose During Hemodialysis

It was the purpose to quantify the hemodynamic effects of a bolus of hypertonic glucose injected into the extracorporeal system in a group of stable and nondiabetic patients during hemodialysis (HD). Glucose and electrolytes were measured in frequent intervals. Arterial blood pressures and heart rates were continuously recorded by noninvasive vascular unloading technique. Beat-to-beat stroke volume, cardiac output, and total peripheral resistance were determined by Modelflow method. Relative blood volumes were continuously measured by ultrasonic and optical means. Eight patients were studied in two treatments. Although arterial pressures and heart rates remained stable, stroke volume and cardiac output transiently increased above (19.2 ± 12.3%) and total peripheral resistance dropped below baseline (18.2 ± 8.6%) by a comparable magnitude. Relative blood volume transiently increased above baseline at 100% (104.9 ± 1.0%). Glucose concentrations were significantly related to relative blood volumes (r = 0.86, p < 0.001). In spite of a substantial increase in blood volume, a bolus of hypertonic glucose does not increase arterial pressures in nondiabetic patients because of concomitant vasodilatation. The relative increase in blood volume quantified by noninvasive HD technology follows the course of glucose and could be used as a surrogate to characterize patients with regard to their glucose metabolism during HD.

1,3-ß-d-Glucan testing is highly specific in patients undergoing dialysis treatment

BACKGROUND

The aim of this combined in-vitro and in-vivo study was to investigate whether state of the art dialysis modalities produce false positive serum 1,3-ß-d-Glucan (BDG) levels.

METHODS

Dialysis fluid for simulated dialysis treatments was spiked with BDG from different sources. Samples were taken from the dialysate and dialyzer blood compartments at various time points. In addition, serum samples were obtained in three groups of patients without invasive fungal disease: a.) twelve patients on chronic hemodialysis (HD)/hemodiafiltration (HDF); b.) ten patients on continuous ambulatory peritoneal dialysis (CAPD); and c.) ten patients with stable chronic kidney disease (CKD) but without dialysis.

RESULTS

Median BDG levels in BDG spiked dialysate were 3250.9, 2050.4, and 390.1 pg/ml respectively. All corresponding samples from the blood compartments were BDG negative. In HD/HDF patients no increase of serum BDG levels could be observed over the duration of treatment. 71/72 BDG tests in this group remained negative. BDG tests were also negative in 9/10 CAPD patients, both in in- and outflow dialysates as well as in all ten patients with CKD.

CONCLUSION

We conclude that state of the art renal replacement therapies using up-to-date treatments are not a cause of falsely elevated serum BDG levels.