Update on Evaluating Patients for Asymptomatic Hypertension

Emerg Med 40(3):33, 2008

By Carlos J. Roldan, MD, FAAEM

Hypertension often goes unrecognized or underassessed in the emergency department. The author reviews the importance of detecting high blood pressure and the JNC-VII guidelines on diagnosis and classification of this condition.

Hypertension and its related complications are among the most common pathologies associated with emergency department visits. It would be easy to assume that managing hypertension is part of chronic health care. To do so, however, would be to fail to recognize that encounters with these patients in the emergency department represent an opportunity to avoid the potentially catastrophic consequences of this condition.

In this article, I’ll present some updated guidelines regarding the diagnosis and classification of hypertension. I’ll also discuss the importance of early identification of hypertension in the emergency department and the role of education and referral as part of a comprehensive management strategy.

ONE billion population

The hypertensive population worldwide is estimated to be around one billion. Approximately 50 million of that population lives in the United States, of whom only about one-half are receiving antihypertensive drugs. It is believed that 30% of patients are unaware that they even have high blood pressure.

Hypertension is the most common primary diagnosis and the most prevalent reason for a primary care office visit in the United States. Its potential long-term consequences are dire. In the elderly population, untreated hypertension doubles the risk of cardiovascular disease complications independent of other risk factors, thus imposing an enormous financial and social burden that has been a public health concern for decades. In 2000, 27% of new end-stage renal disease cases were attributable to uncontrolled hypertension, at an estimated cost of $16.5 billion in 2002.

Hypertension as a risk factor has an independent, consistent, and continuous relationship with coronary artery disease, heart failure, stroke, and kidney disease. The control of high blood pressure has been associated with reductions in the incidence of myocardial infarction, stroke, and heart failure of up to 25%, 40%, and 50%, respectively.

The high cost of extensive workups, medications, treatments, and disabilities related to untreated hypertension justifies a more focused and aggressive approach to this condition, even in the busy environment of the emergency department.

AT LEAST TWO MEASUREMENTS

According to the seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC-VII), a proper diagnosis needs at least two measurements of blood pressure obtained in the office setting after the patient has been sitting quietly for at least five minutes—which could be unrealistic in an emergency department setting. However, some studies suggest that two readings measured in an emergency department are adequate screening tools. Dieterle found that hypertension screening in the emergency department has a high sensitivity and specificity. A study by Backer and colleagues found that emergency department patients without a prior diagnosis of hypertension who had an elevated blood pressure on the first reading also had elevated readings on follow-up evaluations. Another study by Slater showed a correlation between elevated blood pressure in the emergency department and outpatient follow-up measurements.

Chernow and colleagues found that 35% of patients were hypertensive and 33% were pre-hypertensive on follow-up readings after initial readings greater than 159 mm Hg systolic and 94 mm Hg diastolic obtained in an emergency department. Unfortunately, several publications suggest that emergency physicians underrecognize the presence of asymptomatic hypertension and perform suboptimal reassessment, ignoring subsequent readings even if they remain elevated. Improvement is also needed in documentation, patient education, and appropriate follow-up arrangements.

Obviously, the emergency department staff should always try to establish blood pressure readings that are as accurate and reliable as possible. The patient should be seated with the arm bared and supported at heart level; using a mercury sphygmomanometer and a cuff that encircles at least 80% of the arm is optimal. Blood pressure should be verified in the contralateral arm, and the higher value should be used as the reading to be documented. Treatment should be based on that reading.

A thorough physical examination should be performed, including fundoscopy, which may reveal “copper wiring” and arteriovenous nicking as evidence of retinal hypertension-related changes. Other findings—such as obesity, hirsutism, arterial bruits on auscultation, thyroid gland and abdominal masses, lower extremity edema, and an abnormal neurologic exam—may suggest secondary hypertension or end-organ damage.

NEW CLASSIFICATION SYSTEM

To determine a reliable screening level for hypertension in the emergency department, several readings should be taken two minutes apart. The average of those readings should then be calculated. If readings differ by more than 5 mm Hg, additional readings should be averaged, and the classification of the patient’s blood pressure should be based on the average of the highest systolic or diastolic blood pressure readings. Systolic blood pressure is a more precise risk indicator for diagnosing and classifying hypertension than diastolic pressure.

The new JNC-VII’s classification of hypertension for adults aged 18 and older should be combined with concomitant risk factors for effective stratification and control of associated complications. Pre-hypertension has been added as a new category, and stages 2 and 3 have been combined to establish simpler guidelines that are more useful for clinicians, as follows:
• normal (<120/<80)
• pre-hypertension (120-139/80-89)
• stage 1 (140-159/90-99)
• stage 2 (>160/>100)

Emergency physicians need to be aware of the external factors that may cause variations in blood pressure levels. In a study by Pitts and Adams, a spontaneous decline of 11.6 mm Hg in a follow-up diastolic blood pressure measurement compared to the first reading in the emergency department was indicative of an initial “alerting reaction” (traditionally called “white coat hypertension”). Additional factors such as pain, nicotine, caffeine, anxiety, and urinary retention may contribute to a transient elevation in blood pressure and, if present, will need to be addressed. If elevated blood pressure persists, patients should be screened for evidence of end-organ damage.

INTERVENTION IN THE EMERGENCY DEPARTMENT

In the absence of acute end-organ damage, the current literature does not support a better outcome as a result of pharmacologic intervention in the emergency department. However, a nonreferenced recommendation of the JNC-VII establishes that marked elevations in blood pressure even in the absence of end-organ damage calls for immediate oral antihypertensive therapy. The American College of Emergency Physicians also acknowledges the importance of individualized physician management but emphasizes outpatient care over initiation of pharmacologic therapy in the emergency department.

Even if pharmacologic intervention is not considered, the emergency physician should always regard an abnormally high blood pressure reading as a unique opportunity to educate the patient on risk factors and nonpharmacologic interventions, such as weight reduction, if needed, and increased physical activity. The Dietary Approaches to Stop Hypertension (DASH), which centers around a diet rich in potassium and calcium, with intake of only 1.6 grams of sodium daily, should also be encouraged. Moderation in alcohol consumption and discontinuation of oral contraceptives in non-postmenopausal hormonal replacement therapy are also key interventions.

If the decision is made to start pharmacologic intervention, the treating physician needs to be aware of the following:
• The gradual lowering of blood pressure is associated with improved long-term outcomes, and there are no data supporting the need for rapid normalization of blood pressure in asymptomatic patients in the emergency department. Quite the contrary, there have been numerous reports of poor outcomes associated with too rapid a lowering of blood pressure in these patients.
• Older patients should be started on lower doses of medications than those used in younger patients.
• Today the use of an age-adjusted blood pressure target is no longer recommended; rather, it is discouraged.
• Patients with diabetes or renal disease have a recommended blood pressure target level below 130/80.

SPECIAL CONSIDERATIONS

Patients with a history of stroke, as well as those with renal disease, diabetes, and medication-related hypertension, warrant special considerations.

Stroke. In patients with chronic uncontrolled hypertension, the arterioles adjust over time to regulate brain perfusion. After a stroke, however, this compensatory action is disturbed for several weeks; in fact, a spontaneous fall in blood pressure is seen during the first week. Therefore, a rapid lowering of blood pressure during this time in the asymptomatic patient may endanger the marginally perfused brain. A gradual lowering of blood pressure, on the other hand, carries little risk of causing harm.

Renal disease. The most significant intervention to slow progressive renal damage is to lower blood pressure to levels below 130/80. Unless contraindicated by hyperkalemia or renovascular disease, renal insufficiency secondary to hypertension in both diabetic and nondiabetic individuals with creatinine levels below 3 mg/dl should be managed with angiotension-converting enzyme (ACE) inhibitors and angiontensin II receptor blockers (ARBs). This will slow the progression of renal deterioration and control blood pressure.

Diabetes. Volume retention is a common feature in the hypertensive patient with diabetes, which gives diuretics a favorable profile for achieving therapeutic goals alone or combined with other agents. The protective value against progressive renal damage leading to end-stage renal disease seems evident with ACE inhibitors and ARBs more than with other antihypertensives.

Medication-related hypertension. In the general population, immunosuppressors such as cyclosporine are associated with hypertension 25% to 30% of the time. In recipients of solid organ transplants, cyclosporine, steroids, and tacrolimus are associated with hypertension in 50% to 80% of cases as a result of generalized vasoconstriction reducing glomerular filtration and increasing sodium reabsorption. Therefore, therapy should be focused on vasodilation, which is achieved primarily with calcium channel blockers.

Erythropoietin may induce hypertension in 18% to 45% of patients due to increased systemic vascular resistance. However, this undesirable effect may be controlled with a route change from intravenous to subcutaneous or a dose reduction. Sometimes administration of antihypertensive medications as needed will be effective.

UNIQUE OPPORTUNITY

Emergency physicians have a unique opportunity to affect the future of patients screened in the emergency department and found to have asymptomatic hypertension. In a large trial, 51% of people who were informed that they had high blood pressure reported adherence to the lifestyle changes that were necessary to control it. This should encourage education of patients seen in the emergency department with hypertension (see box below).

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