PERITONEAL DIALYSIS
In peritoneal dialysis, 1.5-3 L of a dextrose-containing solution is infused into the peritoneal cavity and allowed to dwel usually 2-4 h. As with hemodialysis, toxic materials are removed through a combination of convective clearance genera and diffusive clearance down a concentration gradient. The clearance of solutes and water during a peritoneal dialysis e balance between the movement of solute and water into the peritoneal cavity versus absorption from the peritoneal cav diminishes with time and eventually stops when equilibration between plasma and dialysate is reached. Absorption of so peritoneal cavity occurs across the peritoneal membrane into the peritoneal capillary circulation and via peritoneal lymp circulation. The rate of peritoneal solute transport varies from patient to patient and may be altered by the presence of drugs, and physical factors such as position and exercise.
Forms of Peritoneal Dialysis
Peritoneal dialysis may be carried out as continuous ambulatory peritoneal dialysis (CAPD), continuous cyclic peritoneal combination of both. In CAPD, dialysis solution is manually infused into the peritoneal cavity during the day and exchan daily. A nighttime dwell is frequently instilled at bedtime and remains in the peritoneal cavity through the night. The dra performed manually with the assistance of gravity to move fluid out of the abdomen. In CCPD, exchanges are performe usually at night; the patient is connected to an automated cycler that performs a series of exchange cycles while the pa exchange cycles required to optimize peritoneal solute clearance varies by the peritoneal membrane characteristics; as suggest careful tracking of solute clearances to ensure dialysis "adequacy."
Peritoneal dialysis solutions are available in volumes typically ranging from 1.5 to 3.0 L. Lactate is the preferred buffer i solutions. The most common additives to peritoneal dialysis solutions are heparin to prevent obstruction of the dialysis c and antibiotics during an episode of acute peritonitis. Insulin may also be added in patients with diabetes mellitus.
Access to the Peritoneal Cavity
Access to the peritoneal cavity is obtained through a peritoneal catheter. Catheters used for maintenance peritoneal dia made of silicon rubber with numerous side holes at the distal end. These catheters usually have two Dacron cuffs to pro proliferation, granulation, and invasion of the cuff. The scarring that occurs around the cuffs anchors the catheter and s tracking from the skin surface into the peritoneal cavity; it also prevents the external leakage of fluid from the peritonea placed in the preperitoneal plane and ~2 cm from the skin surface.
The peritoneal equilibrium test is a formal evaluation of peritoneal membrane characteristics that measures the transfer glucose across the peritoneal membrane. Patients are classified as low, low-average, high-average, and high "transpor equilibration (i.e., high transporters) tend to absorb more glucose and lose efficiency of ultrafiltration with long daytime also tend to lose larger quantities of albumin and other proteins across the peritoneal membrane. In general, patients w characteristics require more frequent, shorter dwell time exchanges, nearly always obligating use of a cycler for feasibil average) transporters tend to do well with fewer exchanges. The efficiency of solute clearance also depends on the volu Larger volumes allow for greater solute clearance, particularly with CAPD in patients with low and low-average transpor Interestingly, solute clearance also increases with physical activity, presumably related to more efficient flow dynamics
As with hemodialysis, the optimal dose of peritoneal dialysis is unknown. Several observational studies have suggested and creatinine clearance (the latter generally measured in L/week) are associated with lower mortality rates and fewer u However, a randomized clinical trial (ADEMEX) failed to show a significant reduction in mortality or complications with a in urea clearance. In general, patients on peritoneal dialysis do well when they retain residual kidney function. The rates increase with years on dialysis and have been correlated with loss of residual function to a greater extent than loss of p capacity. Recently, a nonabsorbable carbohydrate (icodextrin) has been introduced as an alternative osmotic agent. Stu more efficient ultrafiltration with icodextrin than with dextrose-containing solutions. Icodextrin is typically used as the "l CCPD or for the longest dwell in patients on CAPD. For some patients in whom CCPD does not provide sufficient solute c approach can be adopted where one or more daytime exchanges are added to the CCPD regimen. While this approach c clearance and prolong a patient's capacity to remain on peritoneal dialysis, the burden of the hybrid approach can be ov