To meet the ultrafiltration requirements of patients on peritoneal dialysis, the peritoneal dialysate is deliberately rendered hyperosmolar relative to plasma, to create an osmotic gradient that favors net movement of water into the peritoneal cavity. In commercially available peritoneal dialysates, glucose serves as the osmotic agent that enhances ultrafiltration. Available concentrations range from 1.5% to 4.25% dextrose. Over time, the osmolality of the dialysate declines as a result of water moving into the peritoneal cavity and of absorption of dialysate glucose.
The absorption of glucose contributes substantially to the calorie intake of patients on continuous peritoneal dialysis. Over time, this carbohydrate load is thought to contribute to progressive obesity, hypertriglyceridemia, and decreased nutrition as a result of loss of appetite and decreased protein intake. In addition, the high glucose concentrations and high osmolality of currently available solutions may have inhibitory effects on the function of leukocytes, peritoneal macrophages, and mesothelial cells. In an attempt to develop a more physiologic solution, various new osmotic agents are now under investigation. Some of these may prove useful as alternatives to the standard glucose solutions.
Those that contain amino acids have received the most attention.
DIALYSIS TREATMENT OF END STAGE RENAL DISEASE
The goal of dialysis for patients with chronic renal failure is to restore the composition of the body’s fluid environment toward normal. This is accomplished principally by formulating a dialysate whose constituent concentrations are set to approximate normal values in the body. Over time, by diffusional transfer along
favorable concentration gradients, the concentrations of solutes that were initially increased or decreased tend to be corrected. When an abnormal electrolyte concentration poses immediate danger, the dialysate concentration of that electrolyte can be set at a nonphysiologic level to achieve a more rapid correction. On a more chronic basis the composition of the dialysate can be individually adjusted in order to meet the specific needs of each patient.
Dialysate Composition for Hemodialysis
In the early days of hemodialysis, the dialysate sodium concentration was deliberately set low to avoid problems of chronic volume overload such as hypertension and heart failure. As volume removal became more rapid because of shorter dialysis times, symptomatic hypotension emerged as a common and often disabling problem during dialysis. It soon became apparent that changes in the serum sodium concentration—and more specifically changes in serum osmolality— were contributing to the development of this hemodynamic instability.
favorable concentration gradients, the concentrations of solutes that were initially increased or decreased tend to be corrected. When an abnormal electrolyte concentration poses immediate danger, the dialysate concentration of that electrolyte can be set at a nonphysiologic level to achieve a more rapid correction. On a more chronic basis the composition of the dialysate can be individually adjusted in order to meet the specific needs of each patient.
Dialysate Composition for Hemodialysis
In the early days of hemodialysis, the dialysate sodium concentration was deliberately set low to avoid problems of chronic volume overload such as hypertension and heart failure. As volume removal became more rapid because of shorter dialysis times, symptomatic hypotension emerged as a common and often disabling problem during dialysis. It soon became apparent that changes in the serum sodium concentration—and more specifically changes in serum osmolality— were contributing to the development of this hemodynamic instability.
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