With rational treatment with modern antihypertensive drugs, the majority of hypertensive patients can effectively control their blood pressure below target levels. the HOT study confirmed that after an average of 3.8 years of antihypertensive treatment, 92% of patients had their diastolic blood pressure reduced to below 90 mmHg. However, in a small percentage of hypertensive patients blood pressure remains difficult to obtain control. Persistent hypertension or refractory hypertension is defined as a failure to achieve target blood pressure levels despite treatment with a combination of three or more appropriate doses of antihypertensive drugs, including diuretics, or in older patients with simple systolic hypertension, systolic blood pressure is not reduced to target levels. Causes of intractable hypertension 1, improper diet. Some patients with hypertension are caused by improper diet. That is, after suffering from hypertension disease do not pay attention to control the diet, aggravated atherosclerosis, affecting the elasticity of blood vessels, resulting in vascular spasm, can make the blood pressure is high, therefore, the effect of taking antihypertensive drugs is not good. 2, improper medication. The use of a single drug, ignoring the comprehensive treatment of drugs, is also often the reason why hypertension does not drop for a long time. Therefore, hypertensive patients should pay attention to the combined use of drugs. At the same time, should also pay attention to adhere to the medication, neither visible good to stop the medication, and not because of the long treatment of blood pressure does not drop and give up treatment. 3, weight loss is not effective. For obese hypertension, the degree of obesity and blood pressure is often in a balanced relationship, such hypertensive patients if relying solely on antihypertensive drug therapy, but not weight loss, blood pressure decline is often not ideal, so such patients in addition to adhere to antihypertensive treatment, should also pay attention to weight loss. 4, mental ill health. Elevated blood pressure and poor mental state is closely related to the emotional instability, sympathetic nerves in a state of tension, so that the secretion of catecholamines in the body increased, the blood vessels are in a state of constriction, and thus blood pressure does not drop, therefore, hypertensive patients should pay attention to self-mediation, keep a happy mood, overcome impatience. 5, exercise too little. Some hypertensive patients do not love exercise, exercise too little, eat and sleep, sleep and eat, rely solely on drug antihypertensive treatment, blood pressure often does not drop; therefore, hypertensive patients should strengthen physical exercise. Physical activity can not only lower blood pressure, but also remove fat and lose weight, regulate psychological balance, and improve mental tension. A patient can have several of these reasons at the same time, while the following main reasons should be noted; blood pressure control situation mainly relies on clinic blood pressure measurement, it is logical that the accuracy of blood pressure measurement is very important. Some of the following errors are commonly seen: improperly sized cuffs, use of a plain cuff in those with thick upper arm circumference, cuffs placed on the outside of clothing with elastic resistance (sweaters), too rapid deflation, stethoscope body piece placed inside the cuff, and excessive downward force on the stethoscope body piece. Pseudohypertension can occur in older adults with extensive atherosclerosis and calcification, and measurement of brachial artery blood pressure requires higher cuff pressure than the arterial lumen to block blood flow. Pseudohypertension should be suspected when: 1. Blood pressure is significantly elevated without target organ damage. 2, Significant dizziness, weakness, and other hypotensive symptoms arise after antihypertensive therapy in the absence of excessive blood pressure drop. 3, Evidence of calcification at the brachial artery. 4.Brachial artery blood pressure is higher than lower extremity artery blood pressure. 5, Severe simple systolic hypertension. White coat hypertension is defined as elevated blood pressure when measured only in the clinic setting, with normal self-measured blood pressure or ambulatory blood pressure outside the clinic. Drug interactions: Concomitant administration of drugs that interfere with the action of antihypertensive drugs is one of the more insidious causes of difficulty in controlling blood pressure in patients with hypertension. Nonsteroidal anti-inflammatory drugs (e.g., fotarolimus) cause water and sodium retention, enhance the vasoconstrictive response to blood pressure-raising hormones, and can counteract the effects of various antihypertensive drugs except calcium antagonists. Volume overload: Excessive dietary sodium intake counteracts the effect of antihypertensive drugs, and all antihypertensive drugs except calcium antagonists require sodium intake restriction to have a more pronounced antihypertensive effect. Volume overload is usually present in cases of obesity, diabetes, renal impairment, and chronic renal insufficiency. In some patients whose blood pressure is still not controlled by combination therapy, it is often found that diuretics are not used or that the choice and dose of diuretics are not reasonable. Measurement of 24-hour urine sodium and plasma volume can provide the degree of volume overload as a guide to intensive diuretic therapy. A short-term trial of augmented diuretic therapy can also be taken to determine this, combining a long-acting thiazide diuretic and a short-acting tab diuretic to observe the therapeutic effect. Insulin resistance: Insulin resistance is the main pathophysiological cause of intractable hypertension in obese and diabetic patients. Secondary hyperinsulinemic evidence can lead to increased sympathetic activity, water and sodium retention and thickening of resistance vascular smooth muscle cells. Secondary hypertension: Secondary hypertension accounts for 10-30% of cases of intractable hypertension, with renal artery stenosis and primary aldosteronism being the most common causes, especially in elderly patients, with about 1/3 of patients with primary aldosteronism exhibiting intractable hypertension and many without hypokalemia. Notably, occult hypothyroidism is increasing in elderly patients with hypertension. Obstructive sleep apnea syndrome, excessive alcohol consumption, and heavy smoking are also causes of intractable hypertension. Patients with obstructive sleep apnea syndrome have hyperactive sympathetic activity at night, significantly elevated blood pressure, and a loss of circadian rhythm in blood pressure. For the elderly, the goal and speed of blood pressure reduction; elderly hypertension does not necessarily have to be reduced to 140/90 mmHg, but generally to 150/95 mmHg. A 10-30 mmHg decrease in systolic and diastolic blood pressure is considered satisfactory. At the same time, the blood pressure of the elderly should not fall too fast, too fast fall can appear syncope, easy to cause cerebral infarction or induce angina attack. Therefore, the blood pressure of the elderly should be adjusted to a slightly higher average normal physiological blood pressure, generally not lower than 70-80% of the normal blood pressure value, in order to adapt to the blood flow of the heart, kidney and brain.