We are frequently faced with patients on multiple anti-hypertensives still with poorly controlled BP levels. I learned some very interesting points on an article at CJASN from Dr Townsend on how to approach the management of those patients:
** Drug-resistant hypertension is quite common, present in about one in eight hypertensives. Measuring ambulatory BP is very important in this population since 30% of these patients will have BP readings below 135/85 mmHg and will be classified as white-coat HTN
** Ensure the cuff size is adequate, encircling at least 80% of the arm circumference. If the arm is too big for the cuff, it will falsely give higher BP readings.
** Lifestyle factors like dietary sodium intake and excess body weight should be addressed. Despite the difficulty in compliance, a low salt diet (50 mEq Na/day) is capable of reducing BP as much as most effective antihypertensives when used as monotherapy (23 and 9-mmHg reductions of systolic and diastolic, respectively). An average 8 kg weight loss is capable of reducing BP by ~8 mmHg systolic. Double-check compliance to prescribed meds. Frequencies higher than BID can significantly affect adherence to treatment.
** If evaluating for secondary causes of HTN like hyperaldosteronism, do not use the aldosterone/renin ratio if aldosterone level does not exceed the normal value for your reference lab (usually above 15 mg/dL).
** Before screening every patient for renal artery stenosis, consider how it will change your management. Interventions for renal artery stenosis secondary to atherosclerosis have been shown to be associated with significant complications and no major benefits.
** When evaluating the anti-hypertensive regimens, keep in mind that there are usually 4 contributory mechanisms to hypertension in cases of resistant hypertension that should be target with class-specific complimentary drugs:
Total body salt: diuretics (chlorthalidone better than HCTZ based on longer half-life, lasix if lower GFR)
Renin-angiotensin-aldosterone system: ACEI/ARB, Spirinolactone/Eplerenone, Direct renin inhibitor
Sympathetic tone: alpha/beta blocker (labetolol), beta-blocker, alpha-2 agonist, alpha blocker
Vascular tone: calcium channel blocker, hydralazine, minoxidil, (nitrate)
Finally, in patients with resistant hypertension despite maximal uptitration of agents on 4 classes, the addition of aldosterone blocker has been shown to have a strong effect on BP levels, despite its weak diuretic effect. Certainly the issue of hyperkalemia is always a concern but I believe this class of drugs is the most underused in hypertension despite data available (including lowering proteinuria in combination with ACEI or ARB).
Please refer to the article on CJASN for additional details. This new section on Attending Rounds is very practical and quite useful. Kudos to Dr Curhan and editors involved in the creation of this section!