The percent dextrose in the solution used for peritoneal dialysis plays a crucial role in the process. Peritoneal dialysis is a form of renal replacement therapy that involves using the peritoneal membrane in the abdomen as a natural filter to remove waste products and excess fluids from the body.
The dextrose solution used in peritoneal dialysis serves two main purposes:
Osmotic gradient: The dextrose in the solution creates an osmotic gradient across the peritoneal membrane. When the solution is infused into the peritoneal cavity, the dextrose molecules draw water from the bloodstream into the peritoneal space through osmosis. This movement of water helps remove waste products and excess fluids from the body.
Ultrafiltration: The concentration of dextrose in the solution determines the extent of fluid removal during peritoneal dialysis. Higher concentrations of dextrose, such as 2.5% or 4.25%, create a stronger osmotic gradient and promote greater fluid removal. This is known as ultrafiltration. The dextrose molecules draw more water from the bloodstream into the peritoneal cavity, resulting in higher volumes of fluid being removed during the dwell phase of peritoneal dialysis.
Closer to home, I use on alternative nights a back-and-forth combination of first a 5-liter bag of 1.5% solution accompanied by a 3-liter bag of 2.5% solution. The next night the solutions are reversed with a 3-liter bag of 1.5% solution and a 5-liter bag of 2.5% solution. Why so? I have found through experience and experimentation that this mix results in the least amount of leg cramps during the night. It does not preclude them. Often I must get up out of bed and walk around to get things back to normal, but that goes with the treatment.
I know you all enjoyed your high school algebra classes where you were required to solve word problems, thinking you would never encounter them in real life. But real life is real life and it is full of word problems like the following in this context: What is the overall percentage of dextrose in the two different mixtures I am using for dialysis as outlined above?
To determine the percent dextrose solution of the combined solutions, you need to calculate the total amount of dextrose in both solutions and divide it by the total volume of the combined solutions.
Let’s calculate the total amount of dextrose in each solution first:
5 liters of a 2.5% dextrose solution:
Total dextrose = 5 liters × 2.5% = 0.125 liters or 125 milliliters (ml)
3 liters of a 1.5% dextrose solution:
Total dextrose = 3 liters × 1.5% = 0.045 liters or 45 milliliters (ml)
Now, add the total amounts of dextrose from both solutions:
Total dextrose = 125 ml + 45 ml = 170 milliliters (ml)
Next, calculate the total volume of the combined solutions:
Total volume = 5 liters + 3 liters = 8 liters or 8000 milliliters (ml)
Finally, determine the percent dextrose of the combined solutions by dividing the total amount of dextrose by the total volume and multiplying by 100:
Percent dextrose = (Total dextrose / Total volume) × 100
= (170 ml / 8000 ml) × 100
≈ 2.125%
Therefore, the percent dextrose solution of the combined solutions is approximately 2.125%. Following the same methodology for the alternative days yields a solution of approximately 1.72%.
And now we know what combined percentages are, how to calculate them for your own prescription, and in general what the fluids are doing in your peritoneal lining. QED
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