Resistant Hypertension
The average person with high blood pressure is on 2.3 medications. Up to 30% of this population has “resistant hypertension,” defined as blood pressure that is above goal despite the use of three or more appropriate blood pressure medications at maximal doses, with one being a diuretic or “water pill.”
Causes
Obesity, excess salt intake, excessive alcohol use, having diabetes, being over 75, having left ventricular hypertrophy (thickened walls of the heart on EKG or heart ultrasound), obstructive sleep apnea (loud snoring and daytime drowsiness) or chronic kidney disease all contribute. Medications like Non Steroidal Anti Inflammatory Drugs (high doses of aspirin, ibuprofen, or naproxen), stimulant compounds (for ADHD, decongestants, and diet drugs), oral contraceptives, herbal preparations containing ephedra, and some injected anemia treatments can elevate blood pressures.
Falsely elevated readings occur when the cuff is too small for a patient's arm girth, by not getting a resting value, by poor compliance with medications, or by anxiety. Some older patients have heavily calcified arteries, and it is best to also check the pulse at the wrist when evaluating the real blood pressure.
Those who are resistant to control should be screened for secondary forms of hypertension, including kidney disease, kidney artery narrowing, and primary aldosteronism (an excess stress hormone). Less common causes of resistance include Cushing's syndrome, pheochromocytoma, hyperparathyroidism, intracranial tumors, and aortic coarctation (ask your doctor to consider these).
Evaluation
Blood pressure should be measured repeatedly with a proper-size cuff using good technique. Make sure that you are taking all medications as directed. Drugs that may interfere with blood pressure control should be discontinued, if possible.
A physical exam should look for damage in the retina (back of the eye), arterial blockages/narrowing, features of Cushing's syndrome, and a blood pressure checked in both arms. If you are anxious, blood pressure readings at home or work, or ambulatory blood pressure monitoring, should be considered.
Lab evaluation to look for secondary causes should now be considered to include basic labs and urine testing, first morning aldosterone/renin stress hormone levels, activities and ratios. Also, a 24-hour urine test can be obtained if there is a history of severe spikes in pressure with sweating and headache. Imaging tests for kidney artery narrowing can be considered in young patients with severe hypertension, and in older patients with vascular disease. In most cases, no secondary cause is found because the cause is often multifactorial.
Treatment
Lifestyle modification with a low-salt, high-fiber, low-fat diet; weight loss; moderation of alcohol intake; and exercise should be encouraged. Treatment of sleep apnea should be started. Medication regimens should be simplified, making compliance easier.
Blood pressure can often be improved by increasing the dose or changing to a more potent diuretic. In patients with chronic kidney disease, the use of a strong diuretic used twice a day can help. Adding diuretics like spironolactone or amiloride may have additional benefit.
If blood pressure remains elevated despite the above, referral to a hypertension specialist is recommended.
