Ideal blood pressure
First of all, let's talk about the target blood pressure of our dialysis patients, which is what we call ideal blood pressure: the minimum target blood pressure should conform to the patient's personal health to prevent hypotension during dialysis. We suggest that:
Less than 140/90mmHg before dialysis and less than 130/80mmHg after dialysis.
If it is ambulatory blood pressure, the daytime average ambulatory blood pressure is less than 135/85mmHg, and the nighttime average ambulatory blood pressure is less than 120/80mmHg.
Home blood pressure monitoring: systolic blood pressure is between 125- 145mmHg. In the case of poor blood pressure control (such as gaining a lot of weight during dialysis), it is necessary to continuously monitor blood pressure and seek the help of a nephrologist for treatment if necessary.
pathogenesis
There are many reasons for hypertension, and there may be one or more of the following factors. Patients who feel complicated can skip it and see how to treat it:
Water and sodium retention caused by decreased sodium excretion capacity and excessive capacity load.
Ischemia causes the activation of renin-angiotensin-aldosterone system.
The excitability of sympathetic nervous system increases.
Endothelial vasoconstrictor increased or endothelial vasodilator decreased.
Use erythropoietin.
Excessive parathyroid hormone (PTH) causes the increase of intracellular calcium level.
Arterial calcification.
I used to have essential hypertension.
Here are a few key points:
1. Capacity load is too large.
This may be the main cause of hypertension in dialysis patients. Studies have shown that in more than 60% of patients who rely on hemodialysis and almost all peritoneal dialysis, blood pressure can be restored to normal by removing excessive sodium ions and reaching "dry weight". To see if the patient has the problem of excessive volume load, doctors will generally look at the edema of the patient's face and lower limbs, auscultate the cardiopulmonary condition, monitor the plasma atrial natriuretic peptide (ANP) concentration and color Doppler ultrasound before dialysis, and make judgments according to the changes of weight and blood pressure. Patients can't determine whether there is excessive blood volume just by looking at whether there is edema, because the expansion of extracellular volume may not be enough to cause edema. Therefore, patients without edema cannot rule out hypervolemia.
2. Increased sympathetic nerve excitability.
Sympathetic nerve overexcitation is also a common problem in dialysis patients, but its mechanism is still unclear. The afferent signal of excitement may come from the kidney, because there is no sympathetic nerve activation in patients without kidney, which is the treatment basis for nephrectomy in some patients with refractory hypertension.
3. Changes of endothelial cell function.
NO is a synthetic product of L- arginine in endothelial cells, and it is an effective vasodilator. Evidence shows that there is a high level of asymmetric dimethylarginine in plasma of uremic patients. This substance is an inhibitor of nitric oxide synthesis. When NO is deficient, it may promote the formation of hypertension in dialysis patients.
Treatment of hypertension in dialysis patients
1. Control capacity status
For most dialysis patients, controlling the volume state, setting a reasonable dialysis "dry weight" and avoiding excessive weight gain during dialysis can make blood pressure return to normal. In order to achieve this goal, patients themselves should adhere to a low-salt diet, which also helps to alleviate the symptoms of thirst. However, as a doctor, I know it is difficult for patients to stick to this diet. Another method is to reduce the sodium concentration of dialysate and adjust it individually.
2. Extend hemodialysis time and/or increase hemodialysis frequency.
Patients in the large dialysis center in Tassan, France, and some family hemodialysis patients will receive long-term slow hemodialysis. The standard regimen is 8 hours each time and 3 times a week. This scheme can make almost all patients maintain normal blood pressure without using antihypertensive drugs.
Even night hemodialysis (sleeping 6-7 times at night in a week, the duration of dialysis depends on the required sleep time, usually totaling 6- 12 hours) is related to good blood pressure control. Almost all patients who call at night
Of course, it is difficult for hemodialysis centers in China to do this at present. There are many reasons. We need to work hard and the country needs strong support.
3. Antihypertensive drug therapy
Antihypertensive drugs are mainly used for dialysis patients with persistent hypertension after blood volume is completely controlled. There are four main categories:
Calcium channel blockers-Calcium channel blockers are effective and well tolerated in dialysis patients, even in patients with excessive volume, especially in patients with left ventricular hypertrophy and diastolic dysfunction. The only prospective randomized study found that amlodipine can reduce the overall mortality of hypertensive hemodialysis patients compared with placebo. In addition, calcium channel blockers do not need to be supplemented after dialysis.
ACE inhibitors and ARB drugs-ACE inhibitors are well tolerated, especially for patients with heart failure and acute myocardial infarction caused by cardiac systolic dysfunction. These drugs have certain renal protective effects and are the first choice for dialysis patients with significant residual renal function (a lot of urine a day).
Of course, these drugs also have side effects, including increasing the risk of hyperkalemia in long-term hemodialysis patients, interfering with the role of EPO, and allergic reactions (which may be mediated by kinin) in patients using AN69 dialyzer.
Receptor blockers-Receptor blockers are especially suitable for patients with recent myocardial infarction. Patients with heart failure caused by systolic dysfunction may also benefit from receptor blockers. These drugs should be treated slowly from a very low dose under the guidance of a doctor, and then slowly when the dosage is reduced. You can't stop taking drugs as soon as you stop.
The potential side effects of receptor blockers include central nervous system depression, hyperkalemia (especially when non-selective receptor blockers are used), bradycardia and may aggravate heart failure. In addition, patients taking calcium channel blockers at the same time should use receptor blockers with caution, because there is usually a superposition of negative chronotropic effect and negative inotropic effect.
Central sympathetic agonists-central sympathetic agonists (such as methyldopa and clonidine) are rarely used now, because they will have side effects on the central nervous system.
For some dialysis patients, there is resistance to volume control and antihypertensive drug treatment. When the cause cannot be found, minoxidil may be effective in lowering blood pressure.
Treatment of hypertension in hemodialysis
Some patients will have abnormal hypertension in the late stage of dialysis (when most of the excess fluid has been removed). At present, the pathogenesis is very clear. There is evidence that this may be related to the change of NO/ET- 1 balance or endothelial dysfunction. According to our experience, carvedilol seems to be effective in this case, which can block the release of endothelin-1 In a preliminary study of 12 weeks, the study showed that starting to use carvedilol and gradually increasing the dose to 50mg twice a day could reduce the frequency of hypertension attacks during dialysis from 77% to 28%.