increase volume removal in peritoneal dialysis

  • related: Nephrology
  • tags: #literature #nephrology

In patients with volume overload who are receiving PD, the initial focus should be on reducing salt and water intake. For patients who still make urine, high-dose loop diuretics may also be useful. Because the patient is anuric and her salt and water fluid intake has been minimized, the focus should then be turned to improving the effectiveness of salt and water removal during PD.

During each PD exchange, the peritoneum is filled with a dialysate, the dialysate is allowed to dwell for a period of time, and then it is drained. Water is removed by both diffusion and ultrafiltration down osmotic and hydrostatic pressure gradients, respectively, through small pores, gap junctions, and specialized aquaporins in the peritoneal membrane. Solute, in turn, is carried from the blood into the peritoneal dialysate by means of both diffusion and convection. A major determinant of the rate of ultrafiltration is the effective surface area of the peritoneal membrane, which tends to decrease over time owing to chronic low-grade peritonitis caused by the hypertonic dialysate. The most severe form of this process, encapsulating peritoneal sclerosis, can render PD completely ineffective.

The components of PD that can be manipulated are the amount of dialysate instilled, its osmolarity, the dialysate dwell time, and the number of exchanges per day. The primary determinant of the dialysate osmolarity is its glucose concentration, which can be adjusted from approximately 1.5% up to 4.25%. The higher the dialysate glucose concentration, the faster water will diffuse from the blood into the dialysate. As the dwell time increases, water movement into the dialysate and glucose movement into the blood will reduce the osmotic pressure gradients, and water flux will slow. In this patient, shortening the dwell time to keep the osmotic gradients maximal and increasing the frequency of the exchanges is the best way to maximize water removal.

This patient has hyperglycemia that is difficult to control. Increasing (not decreasing) the glucose concentration in the dialysate is a strategy that can be used to improve fluid removal, but it runs the risk of worsening hyperglycemia. In contrast, reducing the amount of glucose in the dialysate may help with the hyperglycemia, but it will also reduce the osmotic gradients driving water into the peritoneal space, so fluid removal will slow. Compared with 2.5% glucose, icodextrin is a high-molecular-weight glucose polymer that can be substituted for glucose in dialysate solutions to reduce the carbohydrate load in patients with diabetes and improve fluid removal, but this choice was not offered.

As mentioned, the longer the dialysate dwells, the more diluted the dialysate becomes, thus slowing the rate of water removal toward the end of the dwell. Furthermore, because this patient is receiving continuous PD, increasing the dwell time will lead to a reduction in the number of exchanges per day.

Increasing the amount of dialysate instilled can increase intraabdominal pressure, which in turn will decrease the hydrostatic pressure gradient for fluid removal. It also runs the risk of causing abdominal compartment syndrome.1234

A patient with a history of anuric end-stage renal disease due to diabetes mellitus is admitted to the ICU with pneumococcal sepsis. She had previously been treated with intermittent hemodialysis, but because of thrombosis of all her access sites, she is now receiving home automated nightly peritoneal dialysis (PD) with a dialysate glucose concentration of 2.5% and a dwell time of 6 h. After her initial resuscitation in the ICU, her fluid intake was minimized, and her home PD prescription was continued. Because her fluid balance remained positive, her PD dwell time was increased to 8 h with three exchanges per day (continuous PD). Two days later, her fluid balance is still positive, and her blood glucose level is consistently greater than 200 mg/dL (11.1 mmol/L).

Which of the following changes to her PD will best help her achieve negative fluid balance?

Footnotes

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  2. Frampton JE, Plosker GL. Icodextrin: a review of its use in peritoneal dialysis. Drugs. 2003;63(19):2079-2105. PubMed ↩

  3. Krediet RT, Douma CE, van Olden RW, et al. Augmenting solute clearance in peritoneal dialysis. Kidney Int. 1998;54(6):2218-2225. PubMed ↩

  4. Zheng S, Auguste BL. Five things to know about volume overload in peritoneal dialysis. Can J Kidney Health Dis. 2023;10:20543581221150590. PubMed ↩