For many years, lactate-containing peritoneal dialysis (PD) solutions have proved to be safe and effective, but they are not ideal.

To correct acidosis, the concentration of lactate in the dialysis solution needs to be in the range of 35-40mM, and the solution must be kept at low pH to prevent caramelisation of glucose during heat sterilisation (1). The combination of high lactate concentration and low pH can impair cellular function (2), and pain upon infusion during dialysis seems to be at least partly related to low pH (3).

Designing a PD solution

The ideal bio-compatible PD solution is one that does not affect the structure and function of the peritoneum. This can be achieved by using solutions that are identical in composition to that of the body's extracellular fluid: in particular, to the composition of blood.

A buffer in the body is a substance that keeps the pH of the extracellular fluids in the body around 7.4. Lactate buffer has most of its buffering capacity in a pH range of 3 to 5. The ideal buffer, however, is bicarbonate, since it is one of the few systems that acts both as a buffer in the body and as a solution buffer.

So, research into improved bio-compatible solutions has focused on two areas: a better, more bio-compatible osmotic agent; and a better pH and buffer.

An alternative to using lactate-containing buffer solutions is to use the natural buffer, bicarbonate. However, to correct acidosis, supranormal levels of bicarbonate would be needed, and the associated high pCO2 may have a detrimental effect on cell function and, in some instances, may be linked to infusion pain. There may also be an increased risk of calcium precipitation and peritoneal calcium deposition.

Developments in PD solutions

New developments in manufacturing technology have produced solutions such as Physioneal.

		Physioneal™ is an innovative PD solution made up of a combination of bicarbonate (25mmol/L) and lactate (15mmol/L) as the buffer and can be used for all exchanges.
		Physioneal™ has a physiological pH of 7.4, and reduced glucose degradation product levels.
		It maintains a normal intraperitoneal pH whereas conventional lactate solutions need up to 120 minutes for the intraperitoneal pH to reach 7.4 or physiological level (4).
		It allows a significant reduction of inflow pain and/or discomfort in sensitive patients (5) and has a high potential for improved long-term preservation of the peritoneal membrane.

The bag itself is easy to use and comes as a two-chambered format. The top chamber contains a solution of dextrose, calcium chloride and magnesium chloride. The bottom chamber contains a solution of sodium bicarbonate, sodium lactate and sodium chloride. When the frangible seal between the chambers is broken, both solutions are mixed together and can then be infused into the patient.

Bicarbonate/lactate solutions have been shown to be effective in those patients in whom solutions based on lactate buffer only, with a low pH, cause abdominal pain or discomfort. The development of solutions such as Physioneal™ are a new way forward, and such innovative developments will continue to improve both the quality of therapy and the quality of life for patients.