Content provided in partnership with

Health Care Industry

Laboratory and diagnostic testing: a perioperative update

AORN Journal, April, 2007 by Kathleen D. Pagana

Most professionals no longer know anyone who does not have an e-mail address. Although just a few years ago, e-mail was a "nice to have" form of communication, it now is a "need to have" requirement. Similarly, although knowledge of diagnostic and laboratory testing was once in the category of "nice to know," it is now "need to know" information for professional nurses. This article presents an update of several relatively new laboratory tests and diagnostic studies--brain natriuretic peptide (BNP), virtual colonoscopy, and microalbumin screening--and provides nursing implications to help perioperative nurses remain informed about this challenging and rapidly changing field.

Most Popular Articles in Health: Fuel your workout: exercisers who eat before they work out have more energy ...; Soothe a dry, itchy scalp: 5 easy expert solutions; Cocktails and calories: Beer, wine and liquor calories can really add up. ...; The sour truth about apple cider vinegar - evaluation of therapeutic use; The, six best supplements you've never heard of: these secret weapons can ...; More »

BRAIN NATRIURETIC PEPTIDE TEST

There are three major neuroendocrine, natriuretic peptides: atrial natriuretic peptide (ANP), BNP, and C-type natriuretic peptide. (1-4) Atrial natriuretic peptide is synthesized in the cardiac atrial muscle. Although BNP was first discovered in porcine brain tissue, which explains its name, BNP, is produced by ventricular muscle in humans. Both BNP and its inactive metabolite, N-terminal portion BNP (ie, NT-proBNP), circulate in the plasma and can be measured via a blood test. (3) Endothelial cells produce C-type natriuretic peptide. (4)

A BNP blood test can help diagnose congestive heart failure (CHF). Atrial natriuretic peptide and BNP are released in response to atrial and ventricular stretch, respectively, and will cause

* vasorelaxation,

* inhibition of aldosterone secretion from the adrenal gland, and

* inhibition of renin from the kidney.

These increase natriuresis (ie, excretion of greater-than-normal amounts of sodium in the urine) and reduce blood volume, which decreases the signs and symptoms of CHF. Nesiritide, a recombinant form of BNP, has been administered as a treatment for acute exacerbation of CHF because it increases natriuresis. (1)

Serum concentrations of BNP and NT-proBNP correlate well to left ventricular pressures. As a result, they are good markers for CHF and are valuable for differentiating dyspnea caused by heart failure from dyspnea caused by other problems. (1-3) The higher the level of BNP, the more severe the CHF (Table 1).

The BNP and NT-proBNP test results also are used in emergency or urgent care settings to aid in the differential diagnosis of shortness of breath. If levels are elevated, the shortness of breath is a result of CHF. If levels are normal, the shortness of breath does not have a cardiac cause. This is particularly helpful in evaluating shortness of breath in patients with cardiac conditions versus chronic lung disease. (2)

Currently, there is a worldwide epidemic of CHF. (5) Use of BNP and NT-proBNP test results to rule out heart failure may save patients from undergoing additional invasive and uncomfortable test procedures, such as echocardiogram and right-heart catheterization. If results are negative, health care providers can focus on other causes of the shortness of breath. (6) Nurses should ask the physician whether he or she would like the patient to undergo the BNP and NT-proBNP test to help determine hydrational status.

Some clinicians in acute care medicine consider the BNP test to be the new gold standard in classifying the severity of CHF because the degree of BNP elevation correlates well with the New York Heart Association classification system (Table 2). (6) The BNP test also is helpful as a prognosticator. Patients with CHF whose BNP levels do not rapidly return to normal with treatment experience a significantly higher risk of mortality in the ensuing months than do those whose levels rapidly normalize with treatment. (7)

Measurement of BNP levels is evolving as an efficient and cost-effective screening technique for identifying patients with other conditions who might be at increased risk for various cardiac problems. For example, BNP elevation screening to determine the risk of cardiac disease in patients with diabetes is becoming increasingly common because of the low cost of the test compared to an echocardiogram. (5)

TEST PROCEDURE. A health care provider collects the patient's venous blood in a lavender-top tube containing ethylene-diaminetetraacetic acid (EDTA). Some laboratories require that the patient fast for eight to 12 hours except for drinking water. In nonemergent situations, cardiovascular medications may be held per a physician's order before the blood specimen is drawn. (8)

IMPLICATIONS FOR PERIOPERATIVE NURSES. Congestive heart failure is a major health problem in the United States. The BNP test is a reliable and inexpensive tool available for rapid, bedside detection of CHF. It is especially useful in emergency and urgent care settings. Perioperative nurses may benefit from the use of this test for patients with a history of CHF; for preoperative screening of their patients with cardiac abnormalities; and in the postoperative period, for patients experiencing dyspnea. For instance, if a patient has elevated levels, a perioperative nurse would carefully monitor the patient's fluid status and alter the plan of care accordingly to prevent fluid overload.

Health Care Industry

Laboratory and diagnostic testing: a perioperative update

AORN Journal, April, 2007 by Kathleen D. Pagana

Find Research Guides for:

Find Featured Titles for: Health

Most Popular Articles in Health

Most Popular Publications in Health