Hemodialysis is the removal of excess water from the body and the return of purified blood to the body, the following is a compilation of my Q&A about the basics of hemodialysis, I hope you like it!
Hemodialysis basics Q&A
1, the principle of hemodialysis to remove toxins
Dialysis is the process of solutes from one side of a semi-permeable membrane through the membrane to the other side of the process of dialysis, any natural (eg, peritoneum) or man-made semi-permeable membranes, as long as the membrane contains the apertures that enable the passage of solutes of a certain size, then the solutes are can move from one side of the membrane to the other by diffusion and convection. In the human body? Toxins? Including metabolites, drugs, and exogenous poisons, as long as they have the right atomic or molecular weight, they can be removed from the body by dialysis. The basic principles are diffusion and convection. Diffusion is the gradient of the concentration of solutes contained in the liquid on both sides of the semipermeable membrane and the different osmotic concentrations it creates, the solutes move from the side with the higher concentration through the semipermeable membrane to the side with the lower concentration. Convection, also known as ultrafiltration, is the process by which solutes and solvents are transported across the membrane due to differences in hydrostatic and osmotic pressure gradients on either side of the dialysis membrane.
The basic principle of hemodialysis is the clinical use of diffusion to separate and purify blood for purification.
The basic principles of blood purification technology are: diffusion, convection, ultrafiltration and adsorption.
2, induction dialysis for what kind of patients, principles, methods
Induction dialysis should be based on the patient's general condition, residual renal function, age and primary disease and other comprehensive consideration of the time to start hemodialysis, in general, in the glomerular filtration rate of 10 ml / min, serum creatinine more than 8 mg% or so when the start of hemodialysis. Children, old age, diabetic patients due to less muscle volume in the body, serum creatinine level is also low, can not accurately reflect the renal function, and children need to grow and develop, old age, diabetic patients with many complications, need to appropriate early dialysis, can be in the glomerular filtration rate of 15 milliliters / minute, serum creatinine 6 - 8 mg% when the start of dialysis. New patients who have just started dialysis cannot be dialyzed with conventional dialysis method at the beginning due to the high level of uremic toxins retained in the body, and it is necessary to take the method of induced dialysis to make the patients adapt gradually. Otherwise, serious complications may occur. The principle of induced dialysis is to carry out small dose, short time and multiple dialysis under the condition that the patient can tolerate it\. The method is generally to use a smaller area of the dialyzer, the first dialysis time in about two hours, dehydration of about 2 liters; the next day or every other day dialysis for three hours, thereafter can be gradually carried out for four hours of regular dialysis; dehydration is decided according to the patient's water and sodium retention. In order to prevent the occurrence of adverse reactions such as imbalance syndrome, dialysis can be performed in small amounts and many times, and high-tension solutions such as 10% sodium chloride, 50% dextrose solution, and 20% mannitol can be used if necessary. During induction dialysis, patients are prone to maladaptation and complications, so it is important to cooperate with healthcare professionals to take preventive and curative measures at the right time.
3. What is an imbalance reaction?
Imbalance syndrome: the main reason is that hemodialysis makes uremic patients blood urea nitrogen and other small molecules in the blood is quickly removed, the plasma osmolality is reduced, and at this time the extravascular tissues, intracellular urea nitrogen has not yet been removed, osmolality is higher than the plasma, the water from the plasma to the tissues, the intracellular transfer of water caused by. In the central nervous system can cause cerebral edema, intracranial pressure rise caused by headache, nausea and vomiting, blood pressure rise, impaired consciousness, spasms and so on. Changes in osmolality can increase intraocular pressure in some patients, which is manifested by ocular distension, orbital and forehead headaches. Other patients develop abdominal pain. The transfer of water to the extravasation can also cause a drop in blood pressure, cardiac arrhythmias, and weakness, which usually disappears within a day after dialysis is stopped. It can be treated intravenously with 10% sodium chloride or 50% dextrose. The use of lower blood flow and smaller area dialyzer can prevent plasma osmolality from decreasing too fast, which is the main method to prevent imbalance syndrome; in addition, the use of high sodium dialysis and drip hypertonic solution can also prevent plasma osmolality from decreasing too fast, maintain effective circulating blood volume and prevent imbalance syndrome from occurring. A biocompatible dialyzer can reduce the reaction between blood and dialysis membrane, which is also beneficial in avoiding hypoxemia and blood pressure drop
4. What is the first-use syndrome and what are the types?
First-use syndrome is a group of syndromes resulting from the use of a new dialyzer and is clinically categorized as Type A (allergic reaction) and Type B (non-specific).
The main symptoms are: hypotension, shortness of breath, chest and back pain, burning, itching, warmth, angioedema, urticaria, runny nose, tearing, and abdominal cramps within 1 hour of using the new dialyzer.
Treatment: ① Severe cases can suspend dialysis, blood is not returned to the patient, with epinephrine, antihistamines or hormones. ② Mild cases continue dialysis, no special treatment.
5. What are the complications of dialysis?
Complications occurring during or at the end of hemodialysis that are related to the dialysis treatment itself are acute complications. These include: imbalance syndrome, first use syndrome, symptomatic hypotension, hypertension, cardiac arrest, arrhythmia, acute left heart failure, pyrogenic reaction, bleeding and acute hemolysis.
Chronic complications of hemodialysis include infection, anemia, neurological complications, dialysis osteodystrophy, heart failure, joint amyloidosis, and pruritus.
6, the classification of dialyzer
Dialyzer is the most important part of the artificial kidney, which consists of dialysis membrane and support structure, according to the support structure of the membrane, the shape of the membrane and the mutual configuration of the relationship, basically can be divided into three major categories: flat plate dialyzer, coiled tubing dialyzer, hollow fiber type dialyzer. In recent years, the emergence of high-flux dialyzers have hollow fiber-type and laminated type two.
Nowadays, the commonly used dialyzer is the hollow fiber dialyzer, which consists of 8,000~15,000 capillary-shaped hollow fiber membranes, with an inner diameter of 200~300 microns and a wall thickness of 20~30 microns, and the blood flow passes through the center of the fibers, and the surrounding area is in contact with the dialysis fluid. The dialysis membrane is a translucent membrane, which can only allow small molecules to be impermeable. When the blood passes through the translucent membrane, small molecules in the blood, such as creatinine, urea, and electrolytes, can enter the dialysis fluid through the translucent membrane, while the electrolytes in the dialysis fluid on the outside of the membrane can also enter the blood through the translucent membrane. This movement of substances through the translucent membrane is called diffusion. Dialysis is the diffusion of substances through the translucent membrane to remove metabolic wastes from the blood. The discharge of water is mainly regulated by the ultrafiltration program control system of the ultrafiltration dialysis machine of the artificial kidney.
7, the causes of hypotension, treatment
Causes: reduction in effective blood volume, reduced vasoconstriction, cardiogenic and dialysis membrane biocompatibility, severe anemia and infection.
Mostly occurs in ultrafiltration excess, blood volume insufficiency, application of antihypertensive drugs, acetate dialysis, eating in dialysis, etc., and partly related to cardiac insufficiency, arrhythmia, pericardial effusion and other cardiogenic factors, which should be dealt with in terms of the cause of the disease.
Manifestations: typical symptoms are cold sweat, nausea, vomiting, and in severe cases, pallor, dyspnea, accelerated heart rate, transient loss of consciousness, and even coma.
Treatment: take the head-low-feet-high position, stop ultrafiltration, slow down the flow rate of the pump, oxygen, if necessary, rapid replenishment of saline 100-200 ml or 50% dextrose solution 20 ml, transfusion of plasma and albumin, and combined with the cause of the disease, timely treatment.
8. Indicators for nutritional assessment
All patients with maintenance hemodialysis (MHD) should be assessed for nutritional status before dialysis using a comprehensive set of indicators, which are examined, including the patient's pre-dialysis or steady state blood albumin, the usual percentage of body weight, and the standard percentage of body weight.
Serum albumin, blood creatinine and creatinine index, and cholesterol levels are valid indicators of a patient's nutritional status, and other measurements include anthropometric indices (including triceps or subscapularis skin fold and mid-upper arm circumference), dual-energy X-ray absorptiometry (DXA), and dry weight. Measurement of PNA or PCR is an effective method to understand the state of protein homeostasis in patients.
Hemodialysis equipmentThe equipment for hemodialysis includes hemodialysis machine, water treatment and dialyzer, **** with the composition of hemodialysis system.
1, hemodialysis machine: is the most widely used in blood purification treatment of a therapeutic instrument, is a more complex electromechanical integration equipment, by the dialysis fluid supply monitoring device and extracorporeal circulation monitoring device. It includes a blood pump, which is the driving force of the extracorporeal circulation of blood; dialysate configuration system; on-line configuration of dialysate with appropriate electrolyte concentration; volume control system, which ensures that the amount of liquid in and out of the dialyzer reaches the predetermined balance target; and various safety monitoring systems, including pressure monitoring, air monitoring and blood leakage monitoring.
2, water treatment system: due to a dialysis in the patient's blood through the dialysis membrane to contact a large number of dialysis fluid (120L), and the city tap water contains a variety of trace elements, especially heavy metal elements, but also contains some disinfectants, endotoxins and bacteria, and blood contact will lead to the entry of these substances into the body. Therefore, tap water needs to be filtered, iron removal, softening, activated carbon, reverse osmosis treatment, only reverse osmosis water can be used as the dilution of concentrated dialysis solution. The tap water for a series of treatment devices that is the water treatment system.
3, dialyzer: also known as ? Artificial kidney? When dialysis blood through the hollow fiber and dialysis fluid through the hollow fiber outside the reverse flow through the blood / dialysis fluid in some small molecules of solutes and water that is through the hollow fiber on the small holes in the exchange, the exchange of the final result is the blood uremic toxins and some electrolytes, excess water into the dialysis fluid is removed, the dialysis fluid in some of the bicarbonate and electrolytes into the blood. Thus, the purpose of removing toxins, water, maintaining acid-base balance and stability of the internal environment is achieved. The total area of the entire hollow fiber, i.e., the exchange area, determines the ability of small molecules to pass, while the size of the membrane pore size determines the ability of medium and large molecules to pass.
4. Dialysis fluid: Dialysis fluid is obtained by diluting the dialysis concentrate containing electrolytes and bases with reverse osmosis water in proportion, eventually forming a solution close to the electrolyte concentration of the blood in order to maintain the normal electrolyte level, and at the same time providing bases to the body through a higher concentration of bases to correct the acidosis existing in the patient. The commonly used dialysis solution bases are mainly bicarbonate, with a small amount of acetic acid.
Indications and contraindications for hemodialysisIndications
I. Acute kidney injury: where acute kidney injury combined with high catabolism (daily blood urea nitrogen BUN rose ?10.7mmol/L, serum creatinine SCr rose ?176.8umol/L, blood potassium rose 1-2mmol/L, HCO3- fell ?2mmol/L) can be dialyzed. .. Non-hypercatabolizers, but those who meet the first of the following and any other of the following can be dialyzed: ① anuria for more than 48h; ② BUN?21.4mmol/L; ③ SCr?442umol/L; ④ blood potassium?6.5mmol/L; ⑤ HCO3-<15mmol/L, CO2-binding capacity L; ⑥ there is obvious edema, pulmonary edema, nausea, vomiting The patient's free hemoglobin >12.4mmol/L. The decision of whether to start renal replacement therapy immediately, and the choice of which modality to choose, should not be based on a certain indicator alone, but should be considered in a comprehensive manner.
Second, chronic renal failure: there is no uniform standard for the timing of hemodialysis for chronic renal failure, due to the limitations of medical and economic conditions, the majority of patients in our country began hemodialysis late. Indications for dialysis: ① endogenous creatinine clearance & lt; 10ml/min; ② BUN & gt; 28.6mmol / L, or SCr & gt; 707.2umol / L; ③ hyperkalemia; ④ metabolic acidosis; ⑤ uremic odor in the mouth with the loss of appetite and nausea, vomiting, etc.; ⑥ chronic congestive heart failure, renal hypertension, or uremic pericarditis with the usual treatment (7) Uremic neurological symptoms, such as personality changes, restless legs syndrome. The time to start dialysis also needs to be a combination of abnormal indicators and clinical symptoms to make a decision.
Third, acute drug or poison poisoning: All drugs and poisons that can be removed through the dialysis membrane, i.e., small molecular weight, do not bind to tissue proteins, and are more evenly distributed in the body can be treated with dialysis. It should be carried out within 8~12h after taking the poison, and the critically ill can start dialysis treatment without waiting for the examination results.
Fourth, other diseases: serious water, electrolyte and acid balance disorders, general therapy is difficult to work and hemodialysis may be effective.
Contraindications
With the improvement of hemodialysis technology, there are no absolute contraindications to hemodialysis, only relative contraindications.
People with shock or hypotension (systolic blood pressure <80mmHg)
Severe myocardial lesions resulting in pulmonary edema and heart failure;
Severe cardiac arrhythmia;
Severe hemorrhagic tendency or cerebral hemorrhage;
Advanced malignant tumors;
Extremely debilitated, terminally ill patients;
Psychotic and uncooperative or those who refuse dialysis by the patients themselves and their families.