Dialysis is a complex medical procedure that is primarily used to remove excess water and waste from the bloodstream of individuals who suffer from end stage renal failure.
In order to understand the treatment process, dialysis technicians and patients must learn about the principles of osmosis and diffusion.
These two concepts are the driving forces behind healthy kidney function and the design of the dialysis machine.
Osmosis and diffusion are constantly at work in the kidneys of those who still have properly functioning kidneys.
These concepts can also be used to help educate the public on how the kidneys work and the actions that can be taken to help reduce the risk of developing advanced renal disease.
The human bloodstream is a chemical solution that contains both solutes and solvents.
A solute is something that can be dissolved by a solvent and includes things such as electrolytes, sugar, and waste particles.
A solvent is something that dissolves other substances.
Water is the most widespread solvent on earth and it is abundant throughout the body.
To perform dialysis, a special fluid referred to as dialysate is used to take advantage of the principles of diffusion and osmosis so that excess water and waste can be removed from the blood.
A dialysis machine contains a membrane that is permeable to small particles like waste and water, but is impermeable to particles such as blood and protein.
This is an important component of the treatment process because it allows the body to retain substances that it needs while getting rid of substances that could cause harm to vital organs.
A healthy kidney contains a similar membrane that only allows certain molecules to cross.
If the membrane becomes damaged, the patient may experience adverse health effects that result from the improper filtration of essential nutrients, proteins, and blood cells.
In order to facilitate the exchange process between the blood and the dialysis fluid, the blood is pumped along one side of the membrane while the dialysate is pumped along the opposite side.
Since diffusion dictates that solutes move from areas of high concentration to areas of low concentration when a permeable membrane exists between the two, waste molecules leave the blood and cross the membrane into the dialysate.
At the same time, osmosis dictates that water move across the membrane in an effort to maintain equal concentration on either side.
In essence, water follows the movement of waste particles so that a state of equilibrium is maintained on both sides of the permeable membrane.
The dialysate is then collected and disposed of by nurses and technicians.
The rate at which the blood can be filtered during dialysis is largely affected by the fact that the body contains three compartments in which equilibrium must be maintained.
These compartments include the intracellular space, extracellular space, and intravascular space.
In more basic terms these represent the spaces inside cells, outside cells, and inside the blood vessels.
Dialysis can only remove excess water and waste from the intravascular space and is dependent on the body's ability to restore equilibrium between the three compartments in order to remove water and waste from the cellular spaces.
The blood that is returned from the dialysis machine to the body has a lower particle concentration than that of the cellular spaces and it causes water and waste to leave the cells and enter the bloodstream via diffusion and osmosis.
This blood can then be cycled back through the machine so that additional water and waste can be removed.
In order to protect the health and well-being of patients, it is important for dialysis technicians to understand that this recycling process must occur slowly.
The human body does not react well to rapid shifts in particle concentrations between compartments and will experience adverse side effects such as nausea, vomiting, muscle cramps, and low blood pressure if the procedure is performed too fast.
This is why dialysis treatment sessions last for a minimum of four hours.