Investigation of the causes of refractory hypertension and emergency treatment plan for hypertensive emergencies

What are the possible causes of refractory hypertension, and how should it be treated?

Refractory hypertension (or intractable hypertension) occurs when, after lifestyle modifications and the use of three antihypertensive drugs (including diuretics) in adequate and appropriate combinations, blood pressure remains above the target level for more than three months, or at least four drugs are required to achieve target blood pressure. This accounts for 15%–20% of hypertension cases. In such cases, there may be an unknown cause of elevated blood pressure that has not been eliminated. It is essential to carefully identify the cause and treat it accordingly. Once the cause is eliminated, blood pressure will naturally decrease. Possible causes of refractory hypertension include:

(1) Continued use of vasopressors (oral contraceptives, adrenal steroids, cocaine, licorice, ephedra, etc.).

(2) Failure to improve lifestyle (weight gain, frequent heavy alcohol consumption).

(3) Volume overload (insufficient diuretic treatment).

(4) Progressive renal insufficiency, high salt intake.

(5) The most common cause of pseudo-refractory hypertension is simple clinic (white coat) hypertension.

(6) Problems with the blood pressure measurement method (not using a larger cuff when the patient's upper arm is thicker).

(7) Presence of sleep apnea syndrome or other secondary factors.

Hypertensive emergencies are not common if medication is taken regularly. In most cases, it is better to err on the side of lower blood pressure than higher. The only exception is during the acute phase of cerebrovascular disease.

What is a hypertensive emergency and how is it treated?

In the course of primary and secondary hypertension, under certain influences, blood pressure rises sharply, and the condition deteriorates rapidly, which is called a hypertensive emergency. It usually exceeds 180/120 mmHg and is accompanied by symptoms such as palpitations, shortness of breath, wheezing, headache, and nausea. Because hypertensive emergencies often occur during acute stroke, hypertensive encephalopathy, acute myocardial infarction, acute left-sided heart failure with pulmonary edema, unstable angina, and aortic dissection, it is important to rule out these conditions when a hypertensive emergency occurs. A systolic blood pressure >220 mmHg and/or a diastolic blood pressure >130 mmHg, regardless of the presence or absence of clinical symptoms, should be considered a hypertensive emergency.

A hypertensive emergency requires immediate treatment. In cases of uncertainty, immediately call emergency services (120 in China) and arrange for transfer to a qualified hospital as soon as possible.

For acute stroke and hypertensive encephalopathy, blood pressure should be lowered cautiously. Pay particular attention to the rate and magnitude of blood pressure reduction. For acute myocardial infarction, acute left-sided heart failure with pulmonary edema, unstable angina, aortic dissection, etc., blood pressure should be immediately lowered to a safe range. Under close monitoring of blood pressure, sodium nitroprusside, nitroglycerin, esmolol, or nicardipine, urapidil, etc., can be slowly administered intravenously. When lowering blood pressure, pay attention to the rate and magnitude, aiming for a reduction to 20%–25% of the original level or to 160/100 mmHg. Observe the changes in the patient's condition before considering whether to continue antihypertensive treatment.

For patients with hypertensive emergencies, short-acting, rapid-acting antihypertensive drugs, such as captopril, labetalol, urapidil, and clonidine, may be considered, depending on the condition. Regular-form nifedipine, due to its rapid absorption and onset of action, exhibits significant fluctuations in blood pressure reduction, and may reflexively cause an increase in heart rate, especially when taken sublingually. Therefore, nifedipine should be used with caution or avoided sublingually, and should never be used for acute coronary syndrome or heart failure.