Hypotension in dialysis refers to a decrease in mean arterial pressure of more than 30 mmHg or systolic pressure of less than 90 mmHg during dialysis compared with that before dialysis, and it is one of the common complications in hemodialysis patients, with an incidence of 20%-30%.
I. Clinical manifestations
Typical symptoms include nausea, vomiting, accelerated pulse rate, normal or slightly decreased blood pressure, patients complain of dizziness, cold sweat, followed by pallor, dyspnea, fine and rapid pulse rate, and in severe cases, fainting and impaired consciousness may occur. Some special symptoms may appear in the early stage, such as yawning, abdominal pain, bowel movement, back pain, which should be noted and dealt with early, which can effectively prevent and control the occurrence of hypotension.
II. Causes
1.Reduction of effective blood volume
Dialysis patients have a dry weight, and hypotension is produced when the water removal in each dialysis is lower than this weight, obviously, the total amount of water removal is too low (lower than the dry weight) will definitely appear hypotension. In addition, hypotension can also occur when the rate of water removal is too fast. As the effective blood volume decreases, the blood becomes thicker, the protein concentration increases, and fluid outside the capillaries keeps moving into the capillaries, a process known as capillary refill. If the ultrafiltration rate is greater than the capillary refill rate, hypotension will occur.
2. Changes in plasma osmolality
In dialysis, due to the removal of solutes such as urea and creatinine, plasma osmolality drops rapidly and lines up with extravascular fluid into an osmotic pressure gradient, driving water to intertissue or intracellular, reducing effective blood volume and leading to blood drop.
3, Hypoproteinemia, anemia, diabetes, polycystic liver, ascites, low protein intake.
4.The sodium concentration in dialysis fluid is too low, and the temperature of dialysis fluid is too high.
5.Taking high dose of long-acting antihypertensive drugs before dialysis and high dose or rapid antihypertensive drugs during dialysis.
6, Cardiac factors, such as pericarditis, myocardial infarction, heart rhythm disorder, heart failure.
7, poor biocompatibility of dialyzer membrane, occurrence of allergy; the effect of hypoxemia on cardiovascular function.
8, eating too much and too fast during dialysis, making the gastrointestinal tract vasodilatation, blood shunt.
9.Other, such as sepsis, blood loss (such as dialysis tubing bleeding, visceral bleeding), hemolysis and pericardial bleeding, etc.
Three, prevention
1.First of all, dialysis patients should be relieved of ideological worries and fears.
2. For severe anemia, pre-fill blood in the blood pipeline or transfuse blood at the beginning of dialysis.
3. For severe hypoproteinemia, plasma, albumin, or other colloidal solutions should be entered in dialysis to maintain the patient’s plasma osmolality.
4.For cardiogenic hypotension and infectious shock, use cardiotonic and antihypertensive drugs.
5.Changing the method of blood purification, using sequential dialysis or hemofiltration can also prevent the drop of blood pressure.
6.Use biocompatible dialysis membrane.
7.Maintain plasma osmolarity, can increase the sodium concentration of dialysis fluid, high sodium dialysis is a proven method.
IV. Treatment
1.Once blood pressure or symptoms are obvious, it is not necessary to measure blood pressure first and input saline immediately.
2. Stop ultrafiltration and reduce blood flow.
3.Lie flat or elevate the lower limbs.
4. For patients with frequent hypotension, the incidence of blood pressure can be effectively reduced through targeted changes in treatment mode (sequential dialysis) and full use of machines with advanced intelligent ultrafiltration mode.