In Canada, hypertension is one of the most common reasons for patients to visit their family physicians.1 Further, most patients with hypertension are managed in a primary care setting by family physicians rather than other specialists.2 With cardiovascular disease being one of the leading causes of death in Canada, improved management of hypertension is key in reducing risk.3
To support primary care providers with the management of hypertension, as well as patients with self-measurement of blood pressure at home, we created 2 infographics (Figures 1 and 2), also available at CFPlus.* To do this, we considered evidence from landmark trials and recommendations from Canadian and American guidelines. The 2-page infographic (Figure 1) on hypertension management is described in the following sections.
When to start a drug?
Evidence for when to start a drug is mixed, and primary care providers should choose a threshold based on patient preference (drug or nondrug options), comorbidities, and frailty. Additionally, it is important to rule out short-term factors that could be temporarily increasing blood pressure (eg, sickness, pain, stress, trauma).
For primary prevention (no history of coronary artery disease, heart attack, stroke, heart failure, or other cardiovascular risk factors†), strong evidence supports the use of an antihypertensive drug once the blood pressure level exceeds 160/100 mm Hg.4,5 For secondary prevention (history of heart attack or stroke) or patients with a 10-year Framingham cardiovascular risk score of 15% or higher, evidence to support the use of an antihypertensive drug once the blood pressure level exceeds 140/90 mm Hg is generally positive.4 For patients with diabetes (type 1 or type 2), lower-quality evidence‡ suggests that a drug should be started once the blood pressure level exceeds 130/80 mm Hg.4
What drug to start first?
To start, prescribe the lowest available dose of a first-line antihypertensive drug and schedule a follow-up blood pressure check 4 weeks later.6 This is the approach used in several landmark antihypertensive trials such as ALLHAT (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial) and SPRINT (Systolic Blood Pressure Intervention Trial). Recommended first-line monotherapy drugs are listed in Figure 1.* Of note, long-acting thiazide-like diuretics such as chlorthalidone and calcium channel blockers (CCBs) such as amlodipine are more effective and safer than angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in black patients.7
When choosing a drug, consider the landmark ALLHAT study, which demonstrated that chlorthalidone lowers cardiovascular risk more than amlodipine and lisinopril do.8 Chlorthalidone is longer acting and has more consistent evidence supporting its blood pressure–lowering and cardiovascular risk–lowering effects than hydrochlorothiazide does.9
What blood pressure goal to aim for?
Once drug therapy is started, consider the patient’s overall health and preferences when setting a blood pressure goal. Strong evidence suggests that most patients taking an antihypertensive medication should aim for a blood pressure level below 140/90 mm Hg.4 Grade C evidence suggests that patients who have diabetes should aim for a level below 130/80 mm Hg.4 High-risk patients with specific cardiovascular risk factors might consent to aim for a systolic goal of 120 mm Hg.4
For patients whose blood pressure levels are consistently above their goals despite taking the usual dose of a first-line antihypertensive drug, expert opinion suggests adding a drug with a complementary mechanism of action.4,10 For example, a patient taking chlorthalidone should usually have an ACEI or ARB added instead of a CCB.4,10
Follow-up with the patient
Measuring blood pressure in the clinic and at home.
Prescribers might find it helpful to ask patients to monitor their blood pressure at home if they suspect a white-coat effect.4,11 To ensure accurate results are obtained, patients should be taught proper technique (Figure 2).*
Laboratory monitoring.
Before initiating or adjusting the doses of ACEIs, ARBs, or diuretics, electrolyte and serum creatinine levels should be measured at baseline. Once the drug or new dose has been started, the same laboratory parameters should be measured within 1 to 2 weeks. Patients at higher risk of hyperkalemia or acute kidney injury should get bloodwork within 7 days.12
If serum creatinine levels rise higher than 30% over baseline after starting an ACEI or ARB, the drug should be stopped and serum creatinine levels rechecked in 3 days.13 If the level increase is from a temporary cause such as dehydration, the drug can be restarted once the event is resolved.13 If no cause is identified, consider the possibility of renal artery stenosis or a drug-induced kidney injury. With both options, the drug should be discontinued, and the primary care provider should request the appropriate laboratory workup for the patient and the patient might require referral to nephrology.13 Angiotensin-converting enzyme inhibitors and ARBs can also increase serum potassium concentrations. A serum potassium level higher than 5.6 mmol/L generally requires a dose reduction or discontinuation of the medication.14
Special situations
Resistant hypertension.
Patients who do not reach their blood pressure goals despite having used at least 3 different antihypertensive drugs—a diuretic, an ACEI or ARB, and a CCB—might have resistant hypertension.15 If the patient is adherent to therapy and the drugs are at the patient’s maximally tolerated doses, it is more effective to add spironolactone than a β-blocker or an α-blocker.16 If spironolactone is added, monitor for elevated potassium levels.16
When to refer.
If you suspect your patient is experiencing a hypertensive emergency, refer him or her to the hospital. Hypertensive emergencies are characterized by acute target organ damage (kidneys, heart, or brain) in the setting of a notably elevated blood pressure level. There is no specific blood pressure measurement that defines a hypertensive emergency, as it is dependent on the signs or symptoms of organ damage (see Figure 1 for a list of symptoms).17
Conclusion
Our 2-page infographic on managing hypertension (Figure 1) is a great tool for primary care providers to use as an easy reference to our discussion in this article. Figure 2 provides a stepwise approach to taking blood pressure at home and can be a resource for your patients. Each figure can be easily accessed from CFPlus.*
Acknowledgments
We thank Adrian Poon for designing the infographics, and Rosemary Killeen for editing the infographics. This work was supported in part by the Ontario College of Pharmacists through funding in support of the Pharmacy5in5 program.
Notes
We encourage readers to share some of their practice experience: the neat little tricks that solve difficult clinical situations. Praxis articles can be submitted online at http://mc.manuscriptcentral.com/cfp or through the CFP website (www.cfp.ca) under “Authors and Reviewers.”
Footnotes
↵* The infographics on managing hypertension (Figure 1) and on how to take blood pressure at home (Figure 2) are available at www.cfp.ca. Go to the full text of the article online and click on the CFPlus tab.
↵† Risk factors include increasing age, tobacco smoking, poor eating habits, excess weight in the abdominal area, uncontrolled diabetes, high cholesterol, male sex, and family history of cardiovascular disease.4
↵ǂ Grade C evidence involves the following: “Recommendations are based on trials that have lower levels of internal validity and/or precision, or trials reporting unvalidated surrogate outcomes, or results from non-randomized observational studies.”4
Competing interests
None declared
- Copyright© the College of Family Physicians of Canada
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