Intraperitoneal Pressure (IPP)

1.- REVIEW. INTRAPERITONEAL PRESSURE (IPP): When performing the SCPD we discovered that UF was strongly influenced by some factor that we did not identify. We suspected that it could be the intra-abdominal pressure (IPP) that we had not measured or considered and we conducted a review of the subject that served for the Final Degree Project of Medicine of the students Elena Descalzo-Casado and Irene Herguedas-Callejo (access to the final degree project and its poster) and that was the basis of a complete review published in Nefrología 2017 in Spanish and English. We undertook experimental studies on IPP in PD that allowed us to learn new aspects that we published in Peritoneal Dialysis International in 2021. Previously, at the ISPD EuroPD 2021 congress, we made two partial pre-presentations of the validation of Durand's method (abstract and poster) and of the evolution over time of IPP (abstract and poster).

2.- EFFECT OF IPP ON UF PRODUCED WITH GLUCOSE 2.27%: Convinced of the influence of IPP on the UF of our SCPD, we wanted to see if its effect was also appreciable with the naked eye in routine clinical practice, where so far it is not considered relevant. We performed an experiment comparing the ultrafiltration of 2 consecutive 2-hour exchanges with 2 liters of 2.27% glucose solution. One of the exchanges was 1500 ml (low IP pressure) and the next 2500 ml (high IP pressure) and since the one with the higher volume would end up with a higher glucose concentration, it should therefore have a higher UF. Would the higher intraperitoneal pressure lower this correlation? This is what happened: we checked the inverse correlation of UF with IPP, as described, but we saw that it was so strong that with the high osmotic force of 2.27%, the increase in IPP caused by 1 liter of intraperitoneal volume not only reduced the UF with respect to that expected but also caused half of the patients to have a lower UF with the exchange of higher concentration than with the exchange of lower concentration. The detailed study was published in Peritoneal Dialysis International in 2020, with partial preliminary presentations at ERA-EDTA 2017 (abstract and poster), SCALN 2018 (abstract and presentation) and SEN 2018 (abstract and poster).

3.- EFFECT OF IPP ON UF PRODUCED WITH GLUCOSE 3.86%: But in PD UF failure is not studied with glucose 2.27% but defined by UF less than 400 ml in PET 3.86% with 2 liters in 4 hours. We therefore performed a second experiment comparing UF in 2 4-hour 3.86% PETs, one with 2 liters and the other with 1 liter, performed less than 1 week apart. Similarly, the 2-liter PET would end up with higher glucose concentration than the 1-liter and thus higher UF. Would intraperitoneal pressure change that result? This was also the case, although the large osmotic force of 3.86% could not be counteracted as strongly by the IPP, the IPP caused 21% of patients to have higher UF with the 1 L exchange and lower final concentration than with the 2L and higher concentration. The final results are not yet published, but we have presented preliminary results at the ERA-EDTA 2018 (abstract and poster), SEN 2019 (abstract and presentation), SCALN 2019 (abstract and poster), and National PD 2020 (English and Spanish abstract and poster) congresses. We also studied the effect of overhydration on UF SCALN 2018 (abstract and presentation).