Hypertension can only be detected when BP is measured. Therefore frequent opportunities should be taken to measure BP: every 6–12 weeks in high-risk patients; every 6–12 months in moderate-risk patients.7
Diagnosis should not be made on the basis of a single visit. Initial raised BP readings should be confirmed on at least two other visits within the space of 3 months; average levels of 90 mmHg diastolic or more, or 140 mmHg systolic or more, are needed before hypertension can be diagnosed. This will avoid the possibility of an incorrect diagnosis, committing an asymptomatic, normotensive individual to unjustified, lifelong treatment.
BP varies continuously and can be affected by many outside factors. Care should therefore be taken to ensure that readings accurately represent the patient’s usual pressure.
BP measurement recommendations6
Office BP measurement guidelines5
Allow the patient to sit quietly for several minutes.
Use a validated (calibrated) device.
Take at least two measurements spaced by 60 seconds.
Use a standard bladder (12–13 × 35 cm), but a larger one for big arms.
Have the cuff at the heart level (see FIG. 86.1).
Deflate the cuff slowly (2 mmHg/s).
Measure BP also in standing position in elderly patients and diabetic patients.
Correct placement of the cuff
On each occasion when the BP is taken, two or more readings should be averaged. Wait at least 30 seconds before repeating the procedure. If the first two readings differ by more than 6 mmHg systolic or 4 mmHg diastolic, more readings should be taken.
Both systolic and diastolic levels should be recorded. For the diastolic reading the disappearance of sound (Phase 5)—that is, the pressure when the last sound is heard and after which all sound disappears—should be used.8 This is more accurate than the muffling of sounds (phase 4) (see FIG. 86.2), which should only be used if the sound continues to zero.
Illustration of blood pressure measurement in relation to arterial blood flow, cuff pressure and auscultation
At the same time the BP is measured, the heart rate and rhythm should be measured and recorded. A high heart rate may indicate undue stress that is causing the associated elevated BP reading. An irregular heart rhythm may cause difficulty in obtaining an accurate BP reading.
|Apprehension ||Patient should be rested for at least 5 minutes and made as relaxed as possible. |
|Caffeine ||Patients should not take caffeine for 4–6 hours before measurement. |
|Smoking ||Patients should avoid smoking for 2 hours before measurement. |
|Eating ||Patients should not have eaten for 30 minutes. |
Strategies for high initial readings
If the initial reading is high (DBP >90 mmHg, SBP >140 mmHg) repeat the measures after 10 minutes of quiet rest. The ‘white coat’ influence in the medical practitioner’s office may cause higher readings so measurement in other settings such as the home or the workplace should be managed whenever possible.
Confirmation and follow-up1
Repeated BP readings will determine whether initial high levels are confirmed and need attention, or whether they return to normal and need only periodic checking. Particular attention should be paid to younger patients to ensure that they are regularly followed up.
Initial diastolic BP readings of 115 mmHg or more, particularly for patients with target organ damage, may need immediate drug therapy.
Once an elevated level has been detected, the timing of subsequent readings should be based on the initial pressure level, as shown in TABLE 86.6.
Table 86.6Follow-up criteria for initial blood pressure measurement for adults 18 years and older9 ||Download (.pdf) Table 86.6 Follow-up criteria for initial blood pressure measurement for adults 18 years and older9
|Systolic (mmHg) ||Diastolic (mmHg) ||Action/recommended follow-up* |
|<120 ||<80 ||Recheck in 2 years |
|120–139 ||80–89 ||Recheck in 1 year—lifestyle advice |
|140–159 ||90–99 ||*Confirm within 2 months—lifestyle advice |
|160–179 ||100–109 ||*Evaluate (or refer) within 1 month—lifestyle advice |
|≥180 ||≥110 ||*Further evaluate and refer within 1 week (or immediately depending on clinical situation) |
| || ||If BP has been confirmed at ≥180 mm Hg systolic and/or ≥110 diastolic mmHg (after multiple readings and excluding ‘white coat’ hypertension), commence drug treatment |
If mild hypertension is found, observation with repeated measurement over 3–6 months should be followed before beginning therapy. This is because levels often return to normal.
Ambulatory 24-hour monitoring
This is required for the diagnosis and follow-up of patients with fluctuating levels, borderline hypertension or refractory hypertension (especially where the ‘white coat’ effect may be significant). Studies have shown that this method provides a more precise estimate of BP variability than casual recordings.
Guidelines for ambulatory BP measurement:
unusual variability of office BP
marked discrepancy between office and home BP
resistance to drug treatment
suspected sleep apnoea
when two BP readings >140/90
‘White coat’ hypertension
This group may comprise up to 25% of patients presenting with hypertension. These people have a type of conditioned response to the clinic or office setting, yet their home BP and ambulatory BP profiles are normal. They appear to be at low risk of cardiovascular disease but may progress to sustained hypertension. Ambulatory 24-hour monitoring can be useful.
This is where office measurements are normal but ambulatory BP is elevated. Prognosis is relatively poor. Suspect it if evidence of end organ damage but normal office BP.
Isolated systolic hypertension
Isolated systolic hypertension is most frequently seen in elderly people. It is not benign.
SBP ≥140 mmHg with a DBP <90 mmHg
If a trial of non-pharmacological therapy fails, then drugs are used to cautiously reduce the systolic BP to between 140 and 160 mmHg.