The choice of hemodialysis machine is a basic factor in determining the hemodialysis program. Here are some factors that influence the choice of dialyzer:
Currently, commonly used dialyzers mainly include four types of dialysis membranes: regenerated cellulose membranes, cellulose acetate membranes, alternative fiber membranes, and synthetic membranes. But please note the following:
1. Both cellulose membrane and synthetic membrane have high flux and low flux.
2. Please do not regard all cellulose membranes as the same, nor should all synthetic membranes be regarded as the same.
3. The biocompatibility between various cellulose membranes or between various synthetic membranes can be different.
As a foreign substance, the dialysis membrane can cause a series of reactions in the patient.
It includes two aspects. One is the blood-membrane reaction, which releases anaphylactic toxins after complement activation And it results in a series of clinical and subclinical manifestations. The other is the disinfectant used for the disinfection of dialyzers, such as ethylene oxide, which has a direct toxic effect on the human body.
Broadly speaking, the biocompatibility of the dialysis membrane refers to a series of reactions directly caused by the establishment of extracorporeal circulation to the patient, among which the blood-membrane reaction is the most important aspect that determines the biocompatibility.
In addition, the form and permeability of the membrane can promote or prevent pyrogen reactions. The temperature, composition, and type of anticoagulant of the dialysate directly affect the patient's hemodynamics and the severity of membrane-mediated reactions, exchange rate, and exchange method, and also affect the stability of the patient's blood flow.
In a narrow sense, biocompatibility refers to the interaction between blood and the dialysis membrane of the hemodialyzer. If the reaction is mild and the patient can tolerate it, the membrane material is biocompatible. If the reaction is severe, affects the health of the patient, or is harmful to the patient, it is biologically incompatible.
The clearance rate is the most useful and important feature of a disposable dialyzer, and it is the main factor in determining the dialysis plan. The clearance rate ranges of different dialyzers have obvious overlaps, which can be selected according to needs. In recent years, the clearance rate of mid-molecular substances represented by VB12 is no longer considered important, but the importance of eliminating β2-microglobulin has attracted more and more attention.
Patients who gain more weight in the dialysis interval need to use a dialyzer with a large ultrafiltration coefficient. However, the stability and tolerance of the patient's cardiovascular system must be considered. The ultrafiltration coefficient of the synthetic membrane is relatively high. The new type of fiber membrane currently used clinically can also meet the treatment needs of patients.
The surface area of the dialyzer is related to the clearance rate and the ultrafiltration coefficient of the dialyzer, but the surface area of the dialyzer is not always proportional to the urea clearance rate.
The surface area of the dialyzer has a smaller urea clearance rate than the surface area, but the dialyzer with more membrane pores is lower. The blood chamber volume of the hemodialyzer is 30-160ml, but the blood chamber volume is only a part of the total external circulation, and the total extracorporeal circulation blood volume is usually 160-270ml. Therefore, the size of the blood chamber of the dialyzer is not the main consideration when choosing a dialyzer.