Resistant Hypertension

Does your blood pressure (BP) remain high despite the use of three different types of high blood pressure drugs at its maximal tolerable dose like a diuretic (medication that increases urine volume and salt excretion)? Do you require four different types of medication to control your BP? If your answer is yes, then you are considered to have Resistant Hypertension (RH).

How to Manage Resistant Hypertension

RH is best managed by a systemic approach which includes the following steps:

• Confirm diagnosis of RH

  This is done by ensuring proper BP measurements, which excludes the “white coat hypertension” effect and with prescribed medication taken.

  To avoid “white coat hypertension”, which happens when a patient’s anxiety in a medical environment results in an abnormally high BP reading, it is important to conduct two or more BP readings when the patient is sitting quietly in a home environment. It is also recommended to do the reading in the morning for a better result.

  Alternatively, the patient can conduct an “ambulatory BP recording” by using an automated BP recording device, which he/she has to wear for 24 hours or more.

• Check compliance with prescribed treatment

  It is important for the doctor to check that the patient is complying with their prescribed medications, as poor compliance with prescribed treatment has been one of the most common causes of apparent RH.

  This is due to patient, doctor or both, which also includes:

  • Complicated dosing schedules
  • Poor communication between doctor and patient
  • Inadequate patient education
  • Memory or psychiatric problems
  • Cost of medication

  A high proportion of patients with hypertension require two or more medications to control their BP. In addition, many patients have other medical conditions e.g. diabetes, high blood cholesterol, coronary heart disease, which also require medications. The high pill load often causes patients to omit one or more of their prescriptions. This may be made worse when there is inadequate communication between the patient and doctor.

  Some patients may have memory or psychiatric problems leading to difficulty in understanding their prescription. In such a situation, it may be necessary to communicate with a family member or caregiver on the patient’s treatment.

  The cost of medication may also be a cause of non-compliance with treatment, particularly with new medications and when the patient must take multiple medications. This may be partly ameliorated by subsidies provided by the government or insurance programmes.

• Reverse contributory factors

  Contributory causes of RH include:

  • Lifestyle factors
  • Obstructive sleep apnea (OSA)
  • Interfering or exogenous substances

  By improving lifestyle factors such as reducing obesity, dietary salt intake and alcohol intake; and increasing physical activity can make it easier to control BP.

  Obstructive sleep apnea (OSA) is a condition characterised by repeated episodes of complete or partial obstructions of the upper airway during sleep and is usually associated with a reduction in blood oxygen saturation. Individuals who have OSA are 30% more likely to suffer from hypertension.

  Some medications and supplements like the following can also increase BP:

  • Nonsteroidal anti-inflammatory drugs
  • Sympathomimetics like decongestants, and appetite suppressants
  • Cocaine, amphetamines, other illicit drugs
  • Oral contraceptive hormones
  • Steroid hormones like cortisone
  • Erythropoietin prescribed for anaemia due to kidney failure
  • Medications to inhibit rejection of organ transplants viz Cyclosporine and tacrolimus

  Patients taking these medications should discuss with their doctors how to control their BP.

  Some illicit drugs and supplements like the following may also increase BP and patients taking them should disclose them to their doctors.

  • Cocaine and amphetamines
  • Licorice (included in some chewing tobacco)
  • Over-the-counter dietary and herbal supplements (e.g. ginseng, yohimbine, ma huang and bitter orange)

• Screen for secondary causes of hypertension

  Resistant hypertension is sometimes secondary to another disease, which includes:

  • Reduced kidney function
  • The disease of the kidney arteries
  • Congenital narrowing of the aorta (the main arterial trunk, referred to as coarctation)
  • Excessive secretion of hormones from the adrenal glands (endocrine glands)
  • Primary aldosteronism and pheochromocytoma (a rare tumour of the adrenal gland)
  • Abnormal thyroid function

  Diagnosis and treatment of these conditions require referral to a physician with special knowledge of these conditions.

  Less than 5% of patients fall under this category.

• Optimise anti-hypertensive agents

  For patients whose BP is still elevated despite multiple medications, their doctor will need to review the medications and consider escalating dosages, changing combinations and/or use less conventional or more recently developed methods.

  Article contributed by Dr Low Lip Ping, Emeritus Chairman, Board of Directors, Singapore Heart Foundation.

What is a “normal” or healthy BP for me?
For most people (according to Singapore’s standards):
< 140/90 at the clinic
< 135/85 at home and at rest
For people with diabetes, chronic kidney disease, or a prior heart attack or stroke:
< 130/80
Your doctor can advise on your specific goal.