Clinical significance of blood pressure response triggered by a doctor's visit in patients with essential hypertension

Sources of inaccuracy in the measurement of adult patients' resting blood pressure in clinical settings: a systematic review

BACKGROUND

To interpret blood pressure (BP) data appropriately, healthcare providers need to be knowledgeable of the factors that can potentially impact the accuracy of BP measurement and contribute to variability between measurements.

METHODS

A systematic review of studies quantifying BP measurement inaccuracy. Medline and CINAHL databases were searched for empirical articles and systematic reviews published up to June 2015. Empirical articles were included if they reported a study that was relevant to the measurement of adult patients' resting BP at the upper arm in a clinical setting (e.g. ward or office); identified a specific source of inaccuracy; and quantified its effect. Reference lists and reviews were searched for additional articles.

RESULTS

A total of 328 empirical studies were included. They investigated 29 potential sources of inaccuracy, categorized as relating to the patient, device, procedure or observer. Significant directional effects were found for 27; however, for some, the effects were inconsistent in direction. Compared with true resting BP, significant effects of individual sources ranged from -23.6 to +33 mmHg SBP and -14 to +23 mmHg DBP.

CONCLUSION

A single BP value outside the expected range should be interpreted with caution and not taken as a definitive indicator of clinical deterioration. Where a measurement is abnormally high or low, further measurements should be taken and averaged. Wherever possible, BP values should be recorded graphically within ranges. This may reduce the impact of sources of inaccuracy and reduce the scope for misinterpretations based on small, likely erroneous or misleading, changes.

Pre-anesthesia systolic blood pressure increases with age regardless of sex

PURPOSE

Pre-anesthesia hypertension (PAH) is the temporary elevation of blood pressure (BP), compared with normal ambulatory recorded BP or self-measured BP at home, in patients waiting for operation in the operating room (OR) before anesthesia induction. In general, the incidence of sustained hypertension (SH) increases progressively with age and the increase is greater in males than in females. In this study, we investigated the influence of age and sex on PAH.

METHODS

Sampling data on consecutive patients who were more than 20 years old and who had undergone surgery under general, intrathecal, or epidural anesthesia were retrospectively collected from hospital records and anesthesia records. Patients with SH, which was defined as a past history of hypertension and taking oral antihypertensive medications, were excluded from the analyses, and the data of 231 patients, 102 males and 129 females, were used for the analyses.

RESULTS

The proportions of male and female patients with a systolic BP (sBP) of more than 140 mmHg in the OR before anesthesia induction were 55.9 and 42.6%, respectively. The proportions of male and female patients with a diastolic BP (dBP) of more than 90 mmHg were 34.3 and 23.3%, respectively. There was no difference in the proportions of male and female patients with PAH. The differences in sBP between measurements in the hospital room (HR) before the operation and those in the OR (ΔsBP) in males and females were 22.9 ± 25.6 and 19.0 ± 24.0 mmHg, respectively. The differences in dBP between measurements in the HR and those in the OR (ΔdBP) in males and females were 12.7 ± 16.5 and 8.4 ± 17.9 mmHg, respectively. There were no differences in ΔsBP and ΔdBP between males and females. The sBP in the OR and the ΔsBP increased significantly with age in both males and females.

CONCLUSION

Age is an important clinical factor related to PAH. Pre-anesthesia sBP and the change in pre-anesthesia sBP increase progressively with age regardless of sex. These findings suggest that the higher BP seen in the elderly in the OR before anesthesia induction, as reported previously, might be explained in part by a greater impact of PAH in older people.

Reproducibility of masked hypertension determined from morning and evening home blood pressure measurements over a 6-month period

Recently, the existence of so-called masked hypertension has attracted attention. In this study, the reproducibility of masked hypertension determined from morning and evening home blood pressure measurements was examined over a 6-month period. Home blood pressure measurements were taken consecutively for 7 days in volunteers at a company in 2002 and again in 2003. The 503 Japanese subjects (329 male, 174 female, mean age: 39.4 years), who were not taking antihypertensive drugs, were asked to measure their home blood pressure three times every morning and three times every evening. We defined casual blood pressure > or =140 (systolic) or > or =90 (diastolic) mmHg and home blood pressure > or =135 or > or =85 mmHg as hypertension. We also defined normotension as <140 and <90 mmHg in casual blood pressure and <135 and <85 mmHg in home blood pressure. We examined the reproducibility of four blood pressure categories (normotension, hypertension, white-coat hypertension, and masked hypertension) over a 6-month period. When measured in morning home blood pressure, the reproducibility of masked hypertension (59.1%) was significantly higher than that of white-coat hypertension (25.0%) and similar to that of hypertension (67.6%). However, the reproducibility of masked hypertension (23.5%) was similar to that of white-coat hypertension (32.0%) and significantly lower than that of hypertension (66.7%) when determined using evening home blood pressure. The concordances in the four blood pressure categories between the two periods were 0.582 (kappa coefficient) and 0.463 when determined using morning and evening home blood pressure data, respectively. In conclusion, the reproducibility of masked hypertension over a 6-month period was moderate in an urban Japanese population when evaluated by morning home blood pressure.

Masked hypertension in diabetes mellitus: a potential risk

The prevalence and clinical significance of masked hypertension (MHT) in diabetics have infrequently been described. The authors assessed the association of MHT (defined using a clinic blood pressure [BP] <140/90 mm Hg and daytime ambulatory BP > or = 135/85 mm Hg) with microvascular and macrovascular end organ damage in 81 clinically normotensive Japanese diabetic persons. The prevalence of silent cerebral infarcts (SCIs), increased left ventricular mass, and albuminuria were evaluated. Of 81 patients, 38 (46.9%) were classified as having MHT and showed significantly more SCIs (mean +/- SE: 2.5+/-0.5 vs 1.1+/-0.2; P=.017), and more albuminuria (39% vs 16%; P=.025), but no increase in left ventricular mass index, than the normotensive persons in office and on ambulatory BP monitoring group. The prevalence of MHT in this diabetic population was high (47%). Diabetic patients with MHT showed evidence of brain and kidney damage. Hence, out-of-office monitoring of BP may be indicated in diabetics whose BP is normal in the clinic.

Estimation of base blood pressure by using a new device in the outpatient clinic

Direct measurement of intra-arterial blood pressure (BP) for 24-h provides approximately 100,000 values that vary enormously, but each (BPi) can be expressed by the equation BPi = BP0 + DeltaBPi (BP0, base BP; DeltaBPi, BP increment, i=1, 2, ..., 100 x 10(3)). About 20% of outpatients with hypertension exhibit white-coat hypertension (WCH). In such patients, DeltaBPc (i = c; c, time at the clinic) is surmised to be large. A method for explaining the physiological factors in DeltaBPc and the estimation of base BP in the outpatient clinic is important. This study addresses this issue. A total of 293 subjects were divided into four groups: 1) WCH group, 45 individuals (office BP > or = 140/90 mmHg and 24-h indirect BP < 125/80 mmHg); 2) normotensive (NT) group, 84 controls matched for age and sex; 3) WHO-I group, 95 hypertensive patients with WHO stage I (office BP > or = 140/90 mmHg and 24-h BP > or = 125/80 mmHg); and 4) WHO-II group, 69 hypertensive patients with WHO stage II. Their BPc and heart rate (HR; HRc, clinic HR) values were measured by a BP-ECG monitoring device in the outpatient clinic. Power-spectral analysis was used to obtain the ratio between the low-frequency component (LF) and high-frequency component (HF) of ECG-RR variability (LF/HF = LH). Twenty-four-hour indirect BP (and BP0) and base HR (HR0) were measured by a portable device (TM2425) at 30-min intervals. Then, DeltaBPc (= BPc - BP0) was estimated by performing linear multivariate analysis applying the model equation DeltaBPc = (BPc -alphaLH)(1-betaHR0/HRc) + epsilon to the above variables (alpha and beta, constant values; epsilon, error). This model equation made it possible to estimate BP0 (and DeltaBPc) with a high coefficient of correlation (r > or = 0.85, mean of error less than 0.82 +/- 5.9 mmHg). The predictive accuracy for discrimination between WCH and sustained hypertension (WHO-I and WHO-II groups) by this equation was 88%. The new DeltaBP-estimation device (BP-ECG monitor) enabled us to infer BP0 and is therefore useful in estimating WCH in the outpatient clinic.

Higher Plasma Homocysteine Concentration Is Associated with More Advanced Systemic Arterial Stiffness and Greater Blood Pressure Response to Stress in Hypertensive Patients

Hyperhomocysteinemia has been reported to be associated with both vascular structure alteration and increased cardiovascular risk. This study examined whether hyperhomocysteinemia causes increased systemic arterial stiffness, thereby enhancing blood pressure response to stress in hypertensive patients. In 50 treated hypertensive patients, we studied brachial-ankle pulse wave velocity (PWV), a new measure for arterial stiffness, blood pressure response to stress, and blood pressure recovery after stress. Autonomic nervous activities were examined by spectral analysis of blood pressure and RR interval variabilities. Total plasma homocysteine and neurohumoral parameters were determined from fasting blood. Brachial-ankle PWV correlated with age (r=0.64, p<0.001), plasma homocysteine concentration (r=0.35, p<0.05), and systolic blood pressure (SBP) (r=0.62, p<0.001). Higher plasma homocysteine concentration was independently associated with greater brachial-ankle PWV (beta=0.388, p=0.01). We classified the subjects into high homocysteine (7.3 nmol/ml or over) and low homocysteine (7.2 nmol/ml or below) groups. Baseline SBP, plasma renin activity, aldosterone, and norepinephrine concentrations were similar between the two groups. However, the SBP values during stress and the recovery periods were higher in the high homocysteine group than the low homocysteine group even after adjusting for sex and age. The behavior of sympathetic vasomotor activity did not differ between the two groups. These data suggest that higher plasma homocysteine concentration is associated with increased systemic arterial stiffness, which may enhance blood pressure reactivity to stress in hypertensive patients.

Beneficial Effect of Cilnidipine on Morning Hypertension and White-Coat Effect in Patients with Essential Hypertension

Home blood pressure has a higher predictive power for cardiovascular events than office blood pressure, and there is a particularly close association between morning blood pressure at home and the incidence of cardiovascular events and mortality in the early morning. In this study, we evaluated the efficacy of a long-acting N-type and L-type calcium channel blocker, cilnidipine, in reducing morning blood pressure at home and in ameliorating the white-coat effect. Fifty-eight subjects diagnosed with both essential hypertension and morning hypertension (43 currently being treated, 15 new patients) were prescribed cilnidipine at a dosage of 10-20 mg per day for 8 weeks. After the addition of or a change to cilnidipine, the morning systolic blood pressure (SBP) was controlled to less than 135 mmHg in 25 (58%) out of the 43 patients currently receiving antihypertensive medication. The office SBP in 24 out of those 25 patients was also maintained under 140 mmHg. In the 15 newly treated patients, the morning SBP of 12 patients (80%) was controlled to less than 135 mmHg after administration of cilnidipine. At baseline, 17 patients showed a clear white-coat effect, in which the difference between office blood pressure and home blood pressure was 20/10 mmHg or more. The white-coat effect was depressed significantly after cilnidipine administration. These results suggest that cilnidipine may serve as a useful antihypertensive medication in the treatment of morning hypertension, and also attenuate the white-coat effect in patients with essential hypertension.

Status of Home Blood Pressure Measured in Morning and Evening: Evaluation in Normotensives and Hypertensives in Japanese Urban Population

To assess home blood pressure status in a Japanese urban population, we analyzed home blood pressure values in normotensive subjects determined by casual blood pressure (< 140/90 mmHg), hypertensive subjects without medication (> or = 140/90 mmHg) and treated hypertensive patients. The subjects (468 male, 232 female; mean age 41 years old) were recruited from a company located in Tokyo. Home blood pressure was measured with a semi-automatic device (Omron HEM-759P). Subjects were instructed to perform triplicate morning and evening measurements on 7 consecutive days. In the treated hypertensive group (n = 70), there was a significant difference between morning (139 +/- 12/88 +/- 9 mmHg) and evening (130 +/- 12/79 +/- 8 mmHg) home blood pressure. In the normotensive group (n = 558), however, only the diastolic blood pressure (DBP) component of the home blood pressure was significantly different between morning (115 +/- 13/72 +/- 9 mmHg) and evening (114 +/- 12/68 +/- 8 mmHg). In the nontreated hypertensive group (n = 72), casual blood pressure (145 +/- 14/92 +/- 9 mmHg) was higher than morning (138 +/- 16/89 +/- 11 mmHg) and evening (134 +/- 16/83 +/- 11 mmHg) home blood pressure, but no difference was seen between morning and evening systolic blood pressure (SBP). According to the reference value of the Japanese Society of Hypertension 2004 (SBP > or = 135 mmHg and/or DBP > or = 85 mmHg), 7.2% (systolic) and 8.7% (diastolic) of subjects in the normotensive group were classified as hypertensive by home blood pressure. Casual blood pressure in the treated hypertensive group was normal in 64.3% for SBP and 70.0% for DBP. However, their morning SBP (32.9%), morning DBP (40.0%), evening SBP (10.0%), and evening DBP (17.1%) were classified as hypertensive by home blood pressure. Furthermore, patients who were taking antihypertensive drug(s) only in the morning (n = 52) showed higher morning SBP (6 mmHg, p = 0.086) and morning DBP (6 mmHg, p = 0.005) than patients taking drug(s) by other administration schedules (n = 18), but no difference in evening home blood pressure was observed. In conclusion, a proportion of the subjects defined as normotensive by casual blood pressure were classified as hypertensive by home blood pressure in the present urban population. Furthermore, morning home blood pressure control in the treated hypertensive group classified as under control by casual blood pressure was insufficient, especially in patients who were taking medication only in the morning.

White-coat hypertension: a clinical review

White-coat hypertension (WCHT), also called 'isolated office or clinic hypertension', is defined as the occurrence of blood pressure (BP) values higher than normal when measured in the medical environment, but within the normal range during daily life, usually defined as average daytime ambulatory BP (ABP) or home BP values (<135 mm Hg systolic and <85 mm Hg diastolic). The prevalence of WCHT varies from 15% to over 50% of all patients with mildly elevated office BP (OBP) values. In untreated hypertensive patients, the probability of WCHT especially increases with female gender and a mildly elevated OBP level. The value of other possible determinants such as (non) smoking status, duration of hypertension, left ventricular mass, number of OBP measurements, educational level, etc. is less consistently shown. Although, for various reasons, studies evaluating the long-term effects of WCHT are not always easy to interpret, most data indicate that persons with WCHT have a worse or equal cardiovascular prognosis than normotensives, but a better one than those with sustained hypertension. WCHT is sometimes considered a prehypertensive state, but data on the long-term evolution of subjects with WCHT are scarce. Patients with WCHT and a high cardiovascular risk or proven target organ damage should be pharmacologically treated. Subjects with uncomplicated WCHT should probably not receive medical therapy, but a close follow-up, including regular assessment of other risk factors and measurement of OBP (every 6 months) and ABP (every 1 or 2 years), is warranted.