Blood pressure in humans is a quantifiable physiologic trait which, in population studies, has a normal distribution with slight skew.¹ Elevated blood pressure has been shown to be a contributing factor in coronary artery disease, stroke, and renal disease. Deleterious effects of blood pressure can be seen even within the "normal" range and seem to increase in tandem with increasing pressures. There is in fact no sharp distinction between normal and pathologic blood pressures; however, as a practical matter, a consensus agreement has been reached as to what range of blood pressures are considered to represent hypertension. Most recently, these guidelines have been outlined in the Express Report from The Seventh Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) (Table 1), the most recognized authority on the practice of diagnosing and treating hypertension.² The JNC 7 recommendations are considered expert opinions and represent helpful guidelines, however, they are not mandates; ultimately the determination of the management of blood pressure rests with the treating physician. It follows that the identification of patients with hypertension requires the provider to be familiar with the uses, advantages, and limitations of the technologies available for noninvasive estimate of blood pressure.

OVERVIEW OF INITIAL EVALUATION

The initial physician evaluation of the hypertensive patient typically occurs in the outpatient environment, often by the primary care provider. The patient may present for unrelated reasons, or the visit may be specifically sought to confirm a blood pressure reading obtained in a hospital visit, emergency room visit, or community screening setting. The goals of the initial evaluation are multifocal: to establish a diagnosis; to gather information pertaining to other cardiovascular risk factors, secondary causes of hypertension, and end-organ effects of hypertension; and to outline treatment and follow-up plans. We tend to approach the initial evaluation in a stepwise fashion, with goals as outlined in Table 2.

To achieve these goals, we recommend a thorough history, physical examination, and basic laboratory work-up as outlined in the following sections.

As noted in JNC 7, identification of hypertensive patients begins with the proper measurement of blood pressure.² The sheer number of patients requiring either screening or follow-up of established hypertension necessitates a diagnostic method that is of low cost, reproducible, and easily used in the outpatient setting. Most commonly, this is accomplished in the clinic by indirect measurement of blood pressure with a standardized technique and certified equipment.³ It is essential for the clinician to be familiar with the proper techniques used in sphygmomanometry. The recommended technique for office measurement of blood pressure (OBP) using this equipment and the auscultatory technique is outlined in Table 3.⁴

Of course, office measurements can be made using automated devices similar to those outlined later in this chapter; however, it remains crucial, in the authors' opinion, that clinicians be capable and proficient with the more traditional auscultatory method of blood pressure determination.

Cuff Size for Measuring Blood Pressures
It is crucial to select the proper cuff for determination of blood pressure (Table 4). Cuffs that are too small may artifactually elevate the blood pressure, whereas the opposite can be true if the cuff is too large (Table 5).⁵

The most avoidable or correctable limitations involve poor training. Gillespie and Curzio⁶ examined several studies that revealed staff weakness in the technique of blood pressure measurement. These studies indicate that only 30% to 81% of staff measure blood pressure to the nearest 2 mm Hg, 3% to 35% identify the correct procedure for cuff deflation, and 23% to 30% know the correct method of identifying the diastolic pressure.⁶ Clearly, the accuracy of the technique depends upon the skill and training of the health care providers who gather these data.

Perhaps the most unavoidable limitation of OBP is that measurement takes place at times and in situations outside the patient's normal routine. This is inherent in OBP. The extent to which this affects the diagnostic or prognostic usefulness of OBP is an area of debate. However, as blood pressure itself is known to be a continuous and variable hemodynamic trait, the limitation of measuring this trait only in the office setting may lead to misidentification of patients on either end of the blood pressure spectrum.

Efforts to correct the above limitation have resulted in two techniques that can measure blood pressure in different, presumably more "natural," settings: home blood pressure (HBP) monitoring and ambulatory blood pressure monitoring (ABPM).

The ability of HBP measurements to accurately reflect the underlying physiology of the patient depends on the same factors that are critical in the office setting: proficiency of skill among those entrusted to obtain the blood pressure and accuracy of the device in use. For a long time, HBP was underutilized because of shortcomings in both areas. With regard to skill, we have already noted the inaccuracy with which health care providers answered basic questions on the auscultatory technique; thus, it seems unlikely that the hypertensive population could be educated en masse in the technique without first assuring better clinical competency among providers. Further, the elemental mercury is a potential source of toxicity, and thus it is impractical and possibly dangerous in the home setting. Those members of the patient community who might be skilled in blood pressure determination are therefore pushed into using other, historically less trusted devices. These concerns certainly do not mean a patient or caregiver cannot accurately determine blood pressure at home using an aneroid device and the auscultatory method; rather, they serve to highlight the fact that accurate HBP monitoring can occur only when diligent training of personnel and calibration of devices are both assured.

Recently, a number of accurate and inexpensive HBP monitoring devices have come onto the market, and this has led to increased interest in the concept. Particularly intriguing are the automated oscillometric devices. These still require training as to proper use; however, with the innate ability to record data, they resolve much of the human error associated with previous methods of HBP measurement. In addition, these devices do not depend on the patient's ability to detect the sounds associated with blood pressure measurement nor to manipulate the pressure cuff; this makes them practical for patients who have diminished sensory or fine motor skills as a result of age or comorbid conditions.

Although hundreds of specific models of automated HBP monitors are in existence, in general there are three types available:⁷

1. Finger devices measure blood pressure by means of data obtained at the distal digit. They are not generally considered useful or accurate.
2. Wrist devices are subject to significant inaccuracy because of improper limb position and cuff-to-heart relations.
3. Upper arm devices are most similar to those used in the OBP auscultatory technique and are the least susceptible to position error.

Although the accuracy of the upper arm devices is considered superior to that of the other two alternatives, the accuracy of HBP devices in general is a subject of great interest. Many HBP devices do not determine blood pressure by the auscultatory method; they instead use an oscillometric method, which may require mathematical transformation into recognizable systolic and diastolic blood pressure readings. Although the transformation is done automatically, the details of how this occurs may not be available to the consumer or clinician since the algorithms are often proprietary and guarded.^7,8 The consensus among experts with regard to automated devices is that they can accurately determine blood pressure, but that only those devices that have undergone a proper and thorough evaluation and validation should be used.^8-10

Assuming the accuracy of the device and proper technique, what information can be obtained from HBP monitoring and what can clinicians do with this information? The key concepts are outlined in Table 7. One consistent finding in comparison studies is that HBP readings are generally lower than those obtained in the clinic setting, a fact which is important in patients suspected of having white-coat hypertension.¹¹

The Association for the Advancement of Medical Instrumentation is entrusted with the validation of instruments to be used for ABPM. The data that ABPM yields are dependent on both the device and the software package used to analyze the data. Multiple studies with diverse patient populations have shown that blood pressures obtained by means of ABPM are typically lower than those obtained in the clinical setting using the auscultatory method.¹² Unfortunately there are no large scale studies to definitively establish "normal" and "hypertensive" values for blood pressure readings obtained by means of ABPM; as such, these distinctions remain a consensus definition. The commonly used ABPM normal values for daytime blood pressure are <135/85, with nighttime blood pressure <120/70.¹¹

ABPM is particularly useful when isolated blood pressure readings in the clinical setting may be suboptimal (Table 8), including situations in which the evaluation of nocturnal blood pressure is important.

The goals of the history include:

1. An attempt to exclude an unidentified underlying cause of the hypertension such as hyperaldosteronism, coarctation of the aorta, pheochromocytoma, hypo- or hyperthyroidism, Cushing's syndrome, renal disease, or renal artery stenosis (Table 11).
   
2. Risk stratification of the patient. Hypertension contributes to the morbidity and mortality of other diseases such as diabetes, heart failure, coronary artery disease, vascular disease, and neurologic disease, including strokes. Additionally, hypertension in pregnancy has important prognostic and therapeutic significance. The presence and magnitude of these conditions should be evaluated early in the course of care of the hypertensive patient.
3. Comprehensive identification of other factors, such as current medications (prescription and other), lifestyle factors, and previous attempts at treatment, which may influence the care of the patient.

The physical examination of the patient starts with the correct measurement of the blood pressure using one of the previously mentioned methods in the proper manner. The blood pressure should be recorded in at least both arms (preferably both arms and one leg in the initial evaluation). Following this, each patient should undergo a complete physical examination. Certain areas of the examination pertinent to the hypertension itself include the following:

1. Neurologic assessment: to exclude any sequelae of previous stroke or ongoing neurologic complaints related to hypertension.

• In the patient with markedly elevated blood pressure, exclude ongoing end-organ damage.

2. Funduscopic examination: to evaluate for end-organ damage.

• Evaluation of the fundi. Actual grading of the fundus is difficult to do effectively in the primary care setting, but the exclusion of exudates, hemorrhage, or papilledema is crucial and should be undertaken in the initial visit, after which a formal consultation with a specialist can be sought, particularly in those with uncertain findings and in all diabetic patients.

3. Cardiovascular examination: to document findings that are commonly seen in patients with hypertension. Includes evaluation for:

• Cardiac murmurs
• S₃ and/or S₄ gallop
• Arrhythmias
• Pulmonary rales
• Estimation of the size and force of the point of maximal impulse (PMI), the size of the heart, and the adequacy of the peripheral circulation
• Assessment of the pulse and presence of bruits in the major vascular beds

4. Abdominal examination: to evaluate the internal organs and visceral vascular beds. Includes:

• Assessment of the size of the kidneys, if possible
• Identification of visceral vascular bed bruits

5. Extremity examination: often an area in which the sequelae of hypertension can be seen and causative mechanisms can sometimes be elicited. Includes:

• Presence of and severity of edema
• Assessment of peripheral pulses
• Exclusion of peripheral signs of embolic disease of arterial or venous insufficiency

See also Table 11.

For convenience, in Table 12 we have included what we consider to be the basic work-up appropriate for all patients with newly diagnosed hypertension, while in Table 13 we list some additional studies to be obtained in those patients suspected of having an underlying cause of their hypertension.

Hypertension is a common disease that has been implicated in causing or contributing to significant morbidity and mortality. Hypertension is generally treatable and in some cases curable; however, this requires timely recognition of the condition. The primary care provider is in a position to identify the hypertensive patient early in the course of the disease and to initiate evaluation and treatment. The provision of optimal care in this scenario requires attention to detail with regard to the measurement of blood pressure, proper employment of alternative methods of determining blood pressure, and a properly guided laboratory evaluation of the patient.

1. Carretero OA, Oparil S. Essential hypertension. Part 1: definition and etiology. Circulation. 2000;101:329-35.
   
   
2. Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7) Express. 2003, US Department of Health and Human Services, National Institutes of Health: NIH Publication No. 03-5233 May 2003.
   
   
3. Prisant LM, Alpert BS, Robbins CB, et al., American National Standard for nonautomated sphymomanometers. Summary report. American Journal of Hypertension. 1995;8:210-13.
   
   
4. Perloff D, Grim C, Flack J, et al., Human blood pressure determination by sphygmomanometry. Circulation. 1993;88(5 Pt 1):2460-70.
   
   
5. Weber, M.A., Hypertension Medicine. 2001, Totawa, NJ: Humana Press.
   
   
6. Gillespie A, Curzio J. Blood pressure measurement: assessing staff knowledge. Nurs Stand. 1998;12:35-37.
   
   
7. O'Brien E, Beevers G, Lip GY. ABC of hypertension: Blood pressure measurement. Part IV-automated sphygmomanometry: self blood pressure measurement. BMJ. 2001;322:1167-70.
   
   
8. Staessen JA, O'Brien ET, Thijs L, Fagard RH. Modern approaches to blood pressure measurement. Occup Environ Med. 2000;57:510-520.
   
   
9. O'Brien E, Petrie J, Littler W, et al. The British Hypertension Society protocol for the evaluation of automated and semi- automated blood pressure measuring devices with special reference to ambulatory systems. Journal of Hypertension. 1990;8:607-619.
   
   
10. White WB, Berson AS, Robbins C, et al. National standard for measurement of resting and ambulatory blood pressures with automated sphygmomanometers. Hypertension. 1993;21:504-509.
    
    
11. McAlister FA, Straus SE. Evidence based treatment of hypertension. Measurement of blood pressure: an evidence based review. BMJ. 2001;322:908-911.
    
    
12. Yarows SA, Julius S, Pickering TG. Home blood pressure monitoring. Arch Intern Med. 2000;160:1251-57.

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