Hypertension Blog

Serum creatinine and blood urea nitrogen (BUN) tests can help detect kidney damage resulting from hypertension. The increased systemic vascular resistance caused by hypertension promotes renal vascular changes and decreases renal blood flow. Diminished blood flow through the glomeruli triggers the release of renin, further increasing vasoconstriction and systemic vascular resistance. The glomeruli atrophy, and the kidneys shrink, inhibiting the excretion of creatinine and BUN.

Normally, the kidneys excrete creatinine-a waste product of muscle metabolism. Usually, serum creatinine levels range from 0.8 to 1.2 mg/dl in men and from 0.6 to 0.9 mg/dl in women. But when reduced blood flow through the glomeruli hinders renal excretion, serum creatinine levels are elevated.

The kidneys also filter and excrete the nitrogen fraction of urea-a waste product of protein metabolism. Normal BUN levels range from 8 to 26 mg/dl.

Test Implications

Elevated BUN levels alone don’t indicate renal dysfunction because infection, trauma, GI bleeding, diet, and dehydration can also increase BUN levels. But when a patient has elevated BUN and serum creatinine levels, he probably has reduced glomerular blood flow and kidney dysfunction.

If a patient is taking a diuretic or an ACE inhibitor to treat his hypertension, closely monitor his BUN and creatinine test results. Diuretics generally increase water and sodium excretion, which lowers circulating intravascular volume. As circulating volume decreases, so does renal blood flow, causing a rise in BUN and creatinine levels.

Other drugs can also influence a patient’s test results. For example, aminoglycosides can increase creatinine levels. Drugs such as allopurinol, furosemide, and indomethacin can increase BUN levels. And chloramphenicol can decrease BUN levels.

Changes in the patient’s protein intake and overhydration and underhydration can also affect the test results

The signs and symptoms of hypertensive encephalopathy result from a rapid increase in diastolic blood pressure to more than 140 mm Hg and the abrupt onset of hypertension in a patient with no history of hypertension or in one with well-controlled hypertension.

Initially, your patient may complain of a severe, generalized headache and restlessness. This may progress to nausea and projectile vomiting. His neurologic signs and symptoms may include confusion, drowsiness, stupor, and generalized tonic­clonic or focal seizures. Because the encephalopathy results from emergency hypertension, he also may exhibit signs of impaired cardiovascular and renal function, such as myocardial ischemia and a decreased glomerular filtration rate.

Retinal damage also can result from hypertensive encephalopathy. An ophthalmic examination may reveal retinal hemorrhages, exudates, and papilledema-a condition known as grade I.V. hypertensive retinopathy.

The fasting serum lipid profile measures total cholesterol, triglyceride, high-density lipoprotein (HDL) cholesterol, and low-density lipoprotein (LDL) cholesterol levels. This test helps in the overall assessment of hypertension and in identifying a patient’s risk of developing coronary artery disease (CAD).

Hyperlipidemia commonly results from hyper­tension. Hypertension injures the endotheliallining of the arterial wall. And this damage promotes platelet aggregation and lipid deposits, leading to intracoronary atherosclerosis and plaque formation.

Patient preparation

To obtain accurate test results, tell the patient to fast for 14 hours before the test. He may drink water during the fast, but he should abstain from drinking alcoholic beverages before the test. Also, he should avoid exercising immediately before the test.

The patient should maintain a stable diet and lifestyle for 2 weeks before this test. An acute illness or an exacerbation of a chronic illness can cause inaccurate test results. Also, certain drugs­such as antilipemics, oral contraceptives, corticosteroids, and diuretics-can interfere with the test results.

Test Implications

High levels of total cholesterol and LDL cholesterol can indicate the development of CAD, as can low levels of HDL cholesterol. A patient’s risk of CAD also increases when elevated triglyceride levels appear in conjunction with high LDL and low HDL cholesterol levels.

If you are suffering from hypertension and are experiencing sudden vision impairment, it’s recommended that you don’t just go out and buy glasses or contact lenses to correct this, but make a thorough examination of the causes of these sight problems. As hypertension can lead to blurry vision for some patients, this can actually be the cause behind your problems, and this is most often not corrected with the usual optical methods, like lenses. The vision impairments your are suffering from are then a result of high blood pressure, which is treated by your regular doctor. It is important however that you make regular visits to your eye doctor, to carefully follow the symptoms.

If your blurry vision isn’t caused by hypertension, you can of course get contacts or glasses, as normal. After a prescription, you are ready to start looking into the market, and this is of course done most easily on the web. To get a good deal, just make a quick search for a website where you can make a contact lens price comparison and you are on your way. As modern lenses are very soft, surprisingly cheap and handy to use, you are very likely to be satisfied.

Echocardiography uses sound waves to evaluate the heart’s structure and function. In this test, a transducer is positioned on various areas of the chest. The transducer emits sound waves, which make contact with the heart and are then recorded on a monitor as moving images of it. Using this test, a physician can observe a patient’s systolic and diastolic function, calculate the sizes of the cardiac chambers, measure left ventricular wall thickness, and measure valve areas.An echocardiogram can accurately detect ischemia or left ventricular hypertrophy resulting from hypertension. On an echocardiogram, ischemic changes appear as wall-motion abnormalities. However, standard echocardiography may not detect ischemia of the left ventricle.

To detect such ischemia, a physician may order stress echocardiography. This test is performed immediately after the patient exercises. Patients who can’t exercise are tested by pharmacologic stress echocardiography. Dobutamine, an inotropic agent, is administered I.V. as the patient lies in bed. The examiner gradually increases the dose until the patient’s heart rate mimics an exercise heart rate. Then, echocardiography is performed to evaluate the heart wall for motion abnormalities.

Echocardiography also helps in evaluating a patient’s response to hypertensive therapy. For instance, calcium channel blockers can decrease left ventricular hypertrophy and the occurrence of arrhythmias; follow-up echocardiographic testing can verify this response to therapy.

Stress or pharmacologic stress echocardiograms are usually performed when cardiac isoenzymes have returned to normal 7 to 10 days after surgery or an acute ML And some patients then have these tests performed several months later so that the physician can evaluate therapy and progress.

Nursing Considerations

When preparing a patient for an echocardiogram, advise him that he may feel some discomfort during the test because the technician must place the transducer firmly between the ribs to enhance sound-wave transmission and diminish interference. Also, advise your patient that he’ll have to lie quietly for 30 to 45 minutes, depending on the technical quality of sound-wave transmission and the cardiac images.

The serum calcium test can be used to monitor a patient’s response to treatment with calcium channel blockers such as amlodipine, diltiazem, felodipine, nifedipine, and verapamil. These drugs work by inhibiting the flow of calcium into the cells, promoting arterial relaxation and decreasing peripheral vascular resistance.About half of the body’s calcium is found in its ionized or free form, while the other half is bound to albumin. Calcium testing results in two measurements: the serum calcium level, which is a total of both forms of calcium, and the ionized calcium level.

Normally, blood levels of total calcium range from 9.0 to 10.5 mg/dl, and blood levels of ionized calcium range from 4.4 to 5.0 mg/dl.

Certain factors can affect the results of calcium testing. Thiazide diuretics can cause hypercalcemia. Also, prolonged use of a tourniquet when performing the venipuncture can increase the calcium level by decreasing blood pH.

Although blood tests aren’t used to detect hypertension, they are useful for identifying the effects of hypertension and the causes of secondary hypertension. They can also help in monitoring a patient’s response to hypertensive treatment.

Electrolyte Levels

Serum electrolyte testing is used to determine the body’s homeostatic status. For a patient with known hypertension, serum electrolyte levels­specifically sodium and potassium levels-can help identify complications arising from hypertension and its treatment. Serum electrolyte testing may also help identify disorders causing secondary hypertension, such as hyperaldosteronism, which is characterized by low serum potassiumlevels.

In many cases, physicians prescribe diuretics and angiotensin-converting enzyme (ACE) inhibitors to treat hypertension. If your patient’s treatment plan will include these drugs as well as a sodium-restricted diet, electrolyte testing should be performed before therapy begins. Also, you should monitor the patient’s electrolyte levels during therapy to help identify abnormal levels that can result in a life-threatening complication.

If a patient is scheduled for serum electrolyte testing, explain the reasons for the test and the importance of the findings. This will increase his knowledge of his hypertensive condition and help promote compliance with his medical regimen.

Test Implications

Normally, serum sodium levels range from 135 to 145 mEq/L, and serum potassium levels range from 3.5 to 5.0 mEq/L. If you note abnormal levels, verify that the patient is adhering to his medical regimen. If he’s complying, notify his physician, who may change the regimen-perhaps by adding a potassium supplement.

Abnormally high potassium levels may indicate changes in renal blood flow and electrolyte exchange in the renal tubules, requiring an adjustment in the patient’s ACE inhibitor dosage. High potassium levels also may result from treatment with potassium sparing diuretics.

A 12-lead ECG, which records the electrical activity of the heart, may help in diagnosing cardiac complications of hypertension such as left ventricular hypertrophy, myocardial ischemia, an MI, and arrhythmias.

Nursing Considerations

Before obtaining a 12-lead ECG, document any antihypertensive drugs your patient is taking. Some of these drugs produce effects that show up on the ECG such as sinus bradycardia or tachycardia, heart block, or a prolonged QT interval. Diuretics in particular may cause electrolyte abnormalities that alter the ECG.

If a hypertensive patient complains of chest pain, evaluate his 12-lead ECG for ischemic changes. Perform the ECG before administering pain-relieving drugs so that you’ll have a base­line ECG. If the patient is using antianginal drugs, repeat the ECG as appropriate to assess his response to therapy.

Test Implications

If the patient has left ventricular hypertrophy, the ECG shows some characteristic changes:

• The QRS complex shows left-axis deviation.
• The Rand S waves of the QRS complex increase in amplitude or depth.
• The ST segment is depressed.
• The T wave is inverted in certain leads .

If the patient has myocardial ischemia, you’ll note ST-segment and T-wave changes. The ST segment, which represents repolarization (the period of recovery after ventricular activation), normally appears flat on the ECG tracing. When coronary blood flow to the myocardium diminishes, however, the ST segment becomes depressed, and the normally upright T wave becomes inverted. Less commonly, ischemia causes an ST-segment elevation.

If a hypertensive patient is taking a diuretic, he may be at risk for developing electrolyte imbalances, which can precipitate arrhythmias. Thiazide diuretics can produce hypercalcemia, which may cause shortening of the ST segment and QT interval. Diuretics also cause hypokalemia, which can lead to ventricular ectopy. ECG abnormalities caused by hypokalemia include ST-segment depression, which can make assessment of ischemic changes difficult; decreased T-wave amplitude; and, occasionally, T-wave inversion.