When is High Blood Pressure Resistant and What Are Some Medicines We Use in That Setting

Hypertension is extremely common. As the goal or target blood pressure continues to decline over time, that is, less than 140/90, more patients, by definition, will have hypertension. In the setting of challenging to control high blood pressure, kidney providers are a frequent part of the management team. Let’s define some terms so that we can understand what it means to have resistant hypertension. We diagnose resistant hypertension when a patient’s blood pressure is above our target range when the patient is on three different classes of blood pressure medications. We also diagnose resistant hypertension when the patient has achieved target blood pressure but requires four or more medications to achieve the target. One medication needs to be a water pill to meet the definition of resistant high blood pressure. Using diuretics, or water pills, in chronic kidney disease patients with hypertension can be a challenge. Favored therapies for patients with CKD or heart disease not infrequently put the kidneys at risk. So we providers need to use water pills, such as hydrochlorothiazide or chlorthalidone, which also are blood pressure pills, carefully to avoid worsening kidney function. A diagram will help explain why, although great medications over the long term, a patient may end up in kidney failure when a provider adds a diuretic in the setting of other high-risk medications used for high blood pressure or chronic kidney disease.

The afferent arteriole goes to the filter which makes the urine which goes to the efferent arteriole which pumps clean blood back to the body.

First, let’s define some terms: the afferent arteriole goes to the filter of the kidney and allows for removal of fluid and toxins through the kidney filter. The efferent arteriole goes away from the kidney and allows for blood to return to the body. The urine follows the arrow and goes into the toilet. Medications we use every day can effect the size of the tubes and the amount of urine produced and risk hurting the kidneys if not used correctly. NSAIDS or non-steroidals like Motrin or Advil constrict the afferent arteriole. Less blood may get to the filter. NSAIDS can worsen GFR. That’s why we don’t recommend them in CKD. ACE inhibitors and ARBs lower blood pressure, but they also dilate or open the efferent arteriole. That takes more blood away from the filter and can worsen GFR. Diuretics or water pills decrease the total volume of the body, can dehydrate, and can worsen GFR. A class of medication, the SGLT2 inhibitors, which causes sugar to spill into the urine, is used to treat CKD, and one mechanism of this class is to constrict the afferent arteriole. So, in the short term, there is a risk of dehydration and worsening kidney function. Over time, patients do better, but as you can see, when we combine these medications, it gets complicated. We want to treat the blood pressure, the chronic kidney disease, the volume status of the patient (avoid edema), diabetes (if a patient has it), heart failure (if a patient has it), and use a combination of therapies used to achieve goal-directed therapy. Beyond this article, some patients have additional causes for high blood pressure. We call this secondary hypertension. If we have concerns for this, we will evaluate a patient’s hypertension further. Resistant hypertension is quite common. Patients usually require multiple therapies from different classes to achieve goal. We frequently use a diuretic if possible if we feel the benefit outweighs the risk of the therapy.