The dialyzer membrane area is generally determined based on dry body weight, while taking into account comprehensive considerations such as cardiac function and nutritional status.
1. Dry body weight
Dialyzer membrane area = dry body weight (kg) * 2% + 0.2~0.4.
For example, for a kidney patient with a dry body weight of 50kg, the membrane area = 50*2% + 0.2~0.4 = 1.2~1.4
Therefore, it is better for kidney patients with small body weight to choose a small membrane area. If you use a large membrane area with a small body weight, there may be problems.
The total amount of blood in the human body ≈ 7%~8% of body weight, and a dialyzer with a large membrane area will cause more blood to circulate outside the body during dialysis, and less effective circulating blood, which will not only cause discomfort such as hypotension and cramps during dialysis, but also lead to insufficient blood supply to other tissues and organs, causing serious harm.
2. Blood flow
The size of the membrane area needs to match the blood flow to ensure the flow rate of blood in the dialyzer.
The normal blood flow should be more than 4 times of dry body weight. If the blood flow is low and the membrane area is too large, the blood flow rate in the dialyzer will slow down, resulting in a longer contact time between the blood and the dialyzer membrane, which is more likely to cause tube blockage and coagulation.
Repeated tube blockage and coagulation will lead to insufficient dialysis, accumulation of toxins, and aggravation of anemia, which will indirectly affect the quality of life and dialysis safety after dialysis.
3. Dialysis imbalance syndrome
For example, a person weighing 50kg, with a blood flow of 200 or slightly higher and a dialyzer membrane area of 1.3, can be fully dialyzed. However, if an oversized dialyzer is used, dialysis imbalance may occur due to excessive clearance.
Dialysis imbalance often occurs 2-3 hours after dialysis or shortly after the end of dialysis, with headaches, nausea, vomiting, and even convulsions and coma, which directly cause discomfort after dialysis and the risk of emergency medical treatment.
4. Cardiovascular function
For patients with hemodialysis filtration, if the cardiovascular function is stable, a larger membrane area can be selected within the allowable range. However, if the cardiovascular function is unstable, it will directly increase the risk of cardiovascular accidents. In this case, the most appropriate membrane area should be selected under the guidance of a doctor.
5. Nutritional status
A large membrane area not only removes toxins, but also loses nutrients such as erythropoietin, transferrin, and albumin, aggravating or inducing anemia and malnutrition.
Kidney patients with poor nutritional status should choose a small membrane area within the allowable range.
6. Toxin removal efficiency
Kidney patients with stable overall conditions and poor removal efficiency of certain indicators can choose a relatively large membrane area within the allowable range.
It is unnecessary and may cause discomfort to use a large membrane area for a small body weight, and a small membrane area for a large body weight will result in insufficient dialysis. Kidney patients should not use it blindly, and choose the one that suits them best.