Resistant hypertension, defined as failure to lower the blood pressure below 140/90 mm Hg with a maximized three-drug regimen, is relatively common. An organized approach helps physicians identify complicating factors that hinder better blood pressure control. O'Rorke and Richardson review the management of difficult-to-control blood pressure.

Causes of resistant hypertension are listed in the accompanying table. Accurate blood pressure readings require the proper technique and optimal conditions. Blood pressure may rise when patients visit a physician (white coat hypertension) but be under good control at other times. Multiple measurements taken at home or ambulatory blood pressure monitoring can accurately identify this condition. Hypertensive disease progression can occur, especially with aging, making blood pressure control more difficult. Other possible causes for difficult-to-control blood pressure should be considered before the problem is diagnosed simply as disease progression.

Medication regimens may be suboptimal, with some patients requiring multiple medications in addition to diet and exercise instructions. For example, diuretics may be helpful in reducing the fluid retention caused by high dietary salt intake. Poor compliance with a therapeutic regimen can also affect the ability to reach the desired blood pressure goal. Antagonizing substances that raise the blood pressure include nonsteroidal anti-inflammatory drugs, caffeine, erythropoietin, licorice, oral contraceptives, sympathomimetic agents, and medications containing sodium.

Coexisting conditions that may increase blood pressure or negatively affect treatment efficacy include anxiety disorders, hyperinsulinism with insulin resistance, obesity, pain, sleep apnea, and smoking. Patients with secondary hypertension have an underlying disorder, including renovascular disease, pheochromocytoma, and hyperaldosteronism, that is a direct cause of hypertension. These conditions and underlying disorders must be managed to attain better blood pressure control.

O'Rorke and Richardson conclude that physicians should systematically look at the potential causes of difficult-to-control hypertension to successfully manage patients with this condition. This step requires working with patients to learn more about their habits and health activities, evaluating blood pressure monitoring techniques, and seeking a primary cause for secondary hypertension when the initial evaluation is unsuccessful. Referral to a hypertension specialist may be necessary when the cause of poor blood pressure control remains elusive.

editor's note: Estimates of the percentage of patients whose hypertension is inadequately controlled are as high as 70 percent. Non-compliance with prescribed regimens is a primary contributor to uncontrolled hypertension. Noncompliance ranges from a simple drug holiday to an unfilled prescription. Patients with other chronic diseases at the time of initiation of antihypertensive therapy have better continuation adherence. Adherence to a drug regimen is not a decision made by a patient when the medication is prescribed by the physician. It is more commonly an ongoing decision that requires a longitudinal behavior change. Patient compliance can be improved with good communication and patient education, concerned follow-up, and use of medication regimens that involve the least number of pills with the least number of daily doses.—r.s.