Factors affecting intraperitoneal pressure (IPP) and its prognostic value in predicting leak risk and gastrointestinal symptoms in adult peritoneal dialysis patients: a systematic review and meta-analysis

BACKGROUND

Intraperitoneal pressure measurement offers therapeutic and prognostic benefits in predicting leak risks and gastrointestinal symptoms in Peritoneal Dialysis (PD) patients. This systematic review aims to evaluate the prognostic utility of intraperitoneal pressure measurements and different estimated intraperitoneal pressure equations in predicting the risk of non-infectious complications in PD patients.

METHODS

Databases including MEDLINE, EMBASE and Cochrane were searched up to July 2023. Randomised and non-randomised trials were included, focusing on End-Stage Kidney Disease (ESKD) patients undergoing PD. Primary outcomes were variables associated with intraperitoneal pressure, while secondary outcomes included PD-related non-infectious complications and gastrointestinal symptoms. Data synthesis combined meta-analysis with narrative synthesis. This review has been registered on PROSPERO (CRD42023475138).

RESULTS

Out of 1828 identified studies, 12 were included for systematic review and 10 for meta-analysis. Body Mass Index (BMI) and Body Surface Area (BSA) showed a consistent positive correlation with intraperitoneal pressure (BMI: r = 0.49, 95% CI 0.35-0.61, I2 = 67.39%, p = 0.003; BSA: r = 0.2, 95% CI 0.08-0.31, I2 = 14.10%, p = 0.324). Conversely, the association between intraperitoneal pressure and age, intraperitoneal volume, and Charlson Comorbidity Index were less consistent. Subgroup analysis demonstrated an association between higher intraperitoneal pressure in patients with increased BMI and BSA. However, the relationship between intraperitoneal pressure and non-infectious mechanical complications remained inconclusive.

DISCUSSION

This review underscores a significant association between intraperitoneal pressure and anthropometric measures (BMI and BSA). The majority of the studies identified included a small sample and considerable bias. However, the association between intraperitoneal pressure and clinically relevant outcomes was not clear.

CONCLUSIONS

While increasing body mass index and body surface areas are associated with increasing intraperitoneal pressure, the clinical relevance of measuring intraperitoneal pressure in an adult population remains unclear, particularly given the absence of an association with clinically relevant non-infectious outcomes.

Intraperitoneal pressure: Stability over time and validation of Durand's measurement method

Intraperitoneal pressure (IPP) is gaining consideration as a relevant parameter of peritoneal dialysis (PD) in adults, although many of its aspects are still pending clarification. We address here its stability over time and the validity of the usual method of clinical measurement, as proposed by Durand in 1992 but never specifically validated. We performed this validation by comparing Durand's method and direct measurements with a central venous pressure system. We performed a total of 250 measurement pairs in 50 patients with different intraperitoneal volumes plus in-vitro measurements with a simulated peritoneum. Absolute differences between the two systems in vivo were 0.87 ± 0.91 cmH₂O (range 0-5 cmH₂O); only 6.4% of them were ≥3 cmH₂O. In vitro results for both methods were identical. We also compared IPP measurements in the same patient separated by 1-4 h (514 measurement pairs in 136 patients), 1 week (92 pairs in 92 patients), and 2 years (34 pairs in 17 patients). Net differences of measurements separated by hours or 1 week were close to 0 cmH₂O, with oscillations of 1.5 cmH₂O in hours and 2.3 cmH₂O in 1 week. IPP measured 2 years apart presented a net decrease of 2.5 ± 4.9 cmH₂O, without correlation with body mass index changes or any other usual parameter of PD. In hours, 7% of IPP differences were >3 cmH₂O, 22% in 1 week, and 50% in 2 years. In conclusion, Durand's method is precise enough to measure IPP in peritoneal dialysis. This parameter is not stable over long timescales, so it is necessary to use recent measurements.

Clinical relevance of marginal factors on ultrafiltration in peritoneal dialysis

BACKGROUND

Ultrafiltration (UF) in peritoneal dialysis (PD) is mainly driven by the osmotic gradient and peritoneal permeability, but other factors-such as intraperitoneal pressure (IPP)-also have an influence.

METHODS

To assess the clinical relevance of these marginal factors, we studied 41 unselected PD patients undergoing two consecutive 2 h, 2.27% glucose exchanges, first with 2.5 L and then with 1.5 L.

RESULTS

IPP, higher in the 2.5 L exchange, had a wide interpatient range, was higher in obese and polycystic patients and their increase with infusion volume was higher for women regardless of body size. UF with 2.5 L correlated inversely with IPP and was higher for patients with polycystosis or hernias, while for 1.5 L we found no significant correlations. The effluent had higher glucose and osmolarity in the 2.5 L exchange than in the 1.5 L one, similar for both sexes. In spite of this stronger osmotic gradient, only 21 patients had more UF in the 2.5 L exchange, with differences up to 240 mL. The other 20 patients had more UF in the 1.5 L exchange, with stronger differences (up to 800 mL, and more than 240 mL for 9 patients). The second group, with similar effluent osmolarity and peritoneal equilibration test (PET) parameters than the first, has higher IPP and preponderance of men. The sex influence is so intense that men decreased average UF with 2.5 L with respect to 1.5 L, while women increased it.

CONCLUSIONS

With 2.27% glucose, sex and IPP-modulated by obesity, polycystosis, hernias, and intraperitoneal volume-significantly affect UF in clinical settings and might be useful for its management.

Intraperitoneal pressure in peritoneal dialysis

The measure of intraperitoneal pressure in peritoneal dialysis is easy and provides clear therapeutic benefits. However it is measured only rarely in adult peritoneal dialysis units. This review aims to disseminate the usefulness of measuring intraperitoneal pressure. This measurement is performed in supine before initiating the drain of a manual exchange with "Y" system, by raising the drain bag and measuring from the mid-axillary line the height of the liquid column that rises from the patient. With typical values of 10-16 cmH₂O, intraperitoneal pressure should never exceed 18 cmH₂O. With basal values that depend on body mass index, it increases 1-3 cmH₂O/L of intraperitoneal volume, and varies with posture and physical activity. Its increase causes discomfort, sleep and breathing disturbances, and has been linked to the occurrence of leaks, hernias, hydrothorax, gastro-esophageal reflux and enteric peritonitis. Less known and valued is its ability to decrease the effectiveness of dialysis significantly counteracting ultrafiltration and decreasing solute clearance to a smaller degree. Because of its easy measurement and potential utility, should be monitored in case of ultrafiltration failure to rule out its eventual contribution in some patients. Although not yet mentioned in the clinical practice guidelines for PD, its clear benefits justify its inclusion among the periodic measurements to consider for prescribing and monitoring peritoneal dialysis.

A New Method to Increase Ultrafiltration in Peritoneal Dialysis: Steady Concentration Peritoneal Dialysis

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BACKGROUND

Peritoneal dialysis (PD) has limited power for liquid extraction (ultrafiltration), so fluid overload remains a major cause of treatment failure. ♦

METHODS

We present steady concentration peritonal dialysis (SCPD), which increases ultrafiltration of PD exchanges by maintaining a constant peritoneal glucose concentration. This is achieved by infusing 50% glucose solution at a constant rate (typically 40 mL/h) during the 4-hour dwell of a 2-L 1.36% glucose exchange. We treated 21 fluid overload episodes on 6 PD patients with high or average-high peritoneal transport characteristics who refused hemodialysis as an alternative. Each treatment consisted of a single session with 1 to 4 SCPD exchanges (as needed). ♦

RESULTS

Ultrafiltration averaged 653 ± 363 mL/4 h - twice the ultrafiltration of the peritoneal equilibration test (PET) (300 ± 251 mL/4 h, p < 0.001) and 6-fold the daily ultrafiltration (100 ± 123 mL/4 h, p < 0.001). Serum and peritoneal glucose stability and dialysis efficacy were excellent (glycemia 126 ± 25 mg/dL, peritoneal glucose 1,830 ± 365 mg/dL, D/P creatinine 0.77 ± 0.08). The treatment reversed all episodes of fluid overload, avoiding transfer to hemodialysis. Ultrafiltration was proportional to fluid overload (p < 0.01) and inversely proportional to final peritoneal glucose concentration (p < 0.05). ♦

CONCLUSION

This preliminary clinical experience confirms the potential of SCPD to safely and effectively increase ultrafiltration of PD exchanges. It also shows peritoneal transport in a new dynamic context, enhancing the influence of factors unrelated to the osmotic gradient.

Oxidative Stress and Nuclear Factor κB (NF-κB) Increase Peritoneal Filtration and Contribute to Ascites Formation in Nephrotic Syndrome

Water accumulation in the interstitium (edema) and the peritoneum (ascites) of nephrotic patients is classically thought to stem from the prevailing low plasma albumin concentration and the decreased transcapillary oncotic pressure gradient. However, several clinical and experimental observations suggest that it might also stem from changes in capillary permeability. We addressed this hypothesis by studying the peritoneum permeability of rats with puromycin aminonucleoside-induced nephrotic syndrome. The peritoneum of puromycin aminonucleoside rats displayed an increase in the water filtration coefficient of paracellular and transcellular pathways, and a decrease in the reflection coefficient to proteins. It also displayed oxidative stress and subsequent activation of NF-κB. Scavenging of reactive oxygen species and inhibition of NF-κB prevented the changes in the water permeability and reflection coefficient to proteins and reduced the volume of ascites by over 50%. Changes in water permeability were associated with the overexpression of the water channel aquaporin 1, which was prevented by reactive oxygen species scavenging and inhibition of NF-κB. In conclusion, nephrotic syndrome is associated with an increased filtration coefficient of the peritoneum and a decreased reflection coefficient to proteins. These changes, which account for over half of ascite volume, are triggered by oxidative stress and subsequent activation of NF-κB.

Peritoneal dialysis tailored to pediatric needs

Consideration of specific pediatric aspects is essential to achieve adequate peritoneal dialysis (PD) treatment in children. These are first of all the rapid growth, in particular during infancy and puberty, which must be accompanied by a positive calcium balance, and the age dependent changes in body composition. The high total body water content and the high ultrafiltration rates required in anuric infants for adequate nutrition predispose to overshooting convective sodium losses and severe hypotension. Tissue fragility and rapid increases in intraabdominal fat mass predispose to hernia and dialysate leaks. Peritoneal equilibration tests should repeatedly been performed to optimize individual dwell time. Intraperitoneal pressure measurements give an objective measure of intraperitoneal filling, which allow for an optimized dwell volume, that is, increased dialysis efficiency without increasing the risk of hernias, leaks, and retrofiltration. We present the concept of adapted PD, that is, the combination of short dwells with low fill volume to promote ultrafiltration and long dwells with a high fill volume to improve purification within one PD session. The use of PD solutions with low glucose degradation product content is recommended in children, but unfortunately still not feasible in many countries.

A reference equation for objectively adjusting dwell volume to obtain more ultrafiltration in daily practice of peritoneal dialysis

OBJECTIVES

Few studies mention how to objectively adjust peritoneal dialysis (PD) dwell volume for adult continuous ambulatory peritoneal dialysis (CAPD) patients. We proposed a reference equation composed of parameters from the peritoneal equilibrium test (PET) for adjusting daily dialysate dwell volume to obtain more ultrafiltration volume. Better fluid control could reduce more fluid overload-related complications.

DESIGN

We used body mass index, waist circumference, intraperitoneal pressure, and other parameters from peritoneal equilibrium test to compose a reference equation for fine-tuning daily dwell volume.

PATIENTS AND SETTING

Eighty-eight PD patients in one center with laboratory data collected during half-yearly PET evaluations were enrolled. Instilled dialysate was composed of 2.57% glucose PD fluid, either 1500 ml or 2000 ml in volume. In addition to other demographic data, intraperitoneal pressure (IPP) was also measured twice in the supine position four hours apart. We applied statistical multivariate techniques of discrimination analysis and logistic regression to verify the most feasible and optimal formula to determine infill volumes for patients.

RESULTS

We determined a novel formula for calculating daily dialysate dwell volume, Z: Z = (0.523 x waist circumference) + (0.852 x body mass index), derived from rotating axes to obtain an accurate prediction rate of 80.68% using the multivariate approach.

CONCLUSION

The novel formula used objective, real-time parameters for determining appropriate dwell volumes for PD patients to optimize maximal ultrafiltration volumes and reduce subjective abdominal discomfort. The novel formula makes frequent adjustment of daily dwell volume by physicians or patients easy to calculate.

Selection of modalities, prescription, and technical issues in children on peritoneal dialysis

Peritoneal dialysis (PD) is widely employed as a dialytic therapy for uraemic children, especially in its automated form (APD), that is associated with less burden of care on patient and family than continuous ambulatory PD. Since APD offers a wide range of treatment options, based on intermittent and continuous regimens, prescription can be individualized according to patient's age, body size, residual renal function, nutritional intake, and growth-related metabolic needs. Transport capacity of the peritoneal membrane of each individual patient should be assessed, and regularly monitored, by means of standardized peritoneal function tests validated in pediatric patients. To ensure maximum recruitment of peritoneal exchange area, fill volume should be scaled to body surface area and adapted to each patient, according to clinical tolerance and intraperitoneal pressure. PD solutions should be employed according to their biocompatibility and potential ultrafiltration capacity; new pH-neutral, glucose-free solutions can be used in an integrated way in separate dwells, or by appropriately mixing during the same dialytic session. Kinetic modelling software programs may help in the tailoring of PD prescription to individual patients' characteristics and needs. Owing to advances in the technology of new APD machines, greater programming flexibility, memorized delivery control, and tele-dialysis are currently possible.

Use of new peritoneal dialysis solutions in children

Standard peritoneal dialysis (PD) solutions with low pH and containing high concentrations of lactate and glucose have been demonstrated to negatively affect the peritoneal membrane, mesothelial cell viability, residential peritoneal cells, and also to inhibit phagocytic functions. An increasing body of experimental evidence supports the idea that the peritoneal hypervascularization and fibrosis observed in long-term PD are causally related to the acute and chronic toxicity of conventional PD solutions. A Physioneal (lactate/bicarbonate mixed buffer pH 7-7.4), Physioneal, Extraneal (7.5% icodextrin), Nutrineal (1.1% amino-acid-containing solution) regimen, for example, offers a significant reduction in carbohydrate load (approximately 40-50%), lower exposure to and absorption of glucose degradation products, reduced oxidative stress, and improved volume control when compared with a first-generation DDDD (4 x Dianeal) regimen. The positive aspects of each solution that we have observed in our patients allow a recommendation on the potential benefit of using these solutions in children treated with PD. In fact, data from the literature as well as the results of the studies reported in this paper show that in children the application of neutral pH bicarbonate/lactate-buffered solution for the standard nighttime APD prescription, icodextrin solution for a long daytime dwell, and AA-based solution in malnourished patients is safe and effective. Extended clinical trials should be encouraged to better define the PD schedules for the combined use of these solutions that may be associated with the best clinical efficacy and the highest level of biocompatibility.