McKenna's Pharmacology for Nursing, 2e

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C H A P T E R 4 3 Drugs affecting blood pressure

The evidence

BOX 43.1

“White coat” hypertension The diagnosis of hypertension is accompanied by the impact of serious ramifications, such as increased risk of numerous diseases and cardiovascular death, as well as the potential need for significant lifestyle changes and also drug therapy, which may include many unpleasant adverse effects. Consequently, it is important that a person be correctly diagnosed before being labelled hypertensive. Researchers in the 1990s discovered that some people were hypertensive only when they were in their doctor’s office having their blood pressure measured.This was correlated to a sympathetic stress reaction (which elevates systolic blood pressure) and a tendency to tighten the muscles (isometric exercise, which elevates diastolic blood pressure) while waiting to be seen and during the blood pressure measurement.The researchers labelled this phenomenon “white coat” hypertension. The Heart Foundation has put forth new guidelines for the diagnosis of hypertension. A person should have multiple consecutive blood pressure readings above normal.These guidelines point out the importance of using the correct technique when taking a person’s blood pressure, especially because the results can have such a tremendous impact on a person. It is good practice to periodically review the process for performing this routine task. For example, the nurse should:

Untreated hypertension increases a person’s risk for the following conditions: CAD and cardiac death, stroke, renal failure and loss of vision. Because hyper- tension has no symptoms, it is difficult to diagnose and treat, and it is often called the “silent killer”. All of the drugs used to treat hypertension have adverse effects, many of which are seen as unacceptable by otherwise healthy people. Health professionals face a difficult challenge trying to convince people to comply with their drug regimens when they experience adverse effects and do not see any positive effects on their bodies. Research into the cause of hypertension is ongoing. Many theories have been proposed for the cause of the disorder, and it may well be due to a mosaic of factors. Factors that are known to increase blood pressure in some people include high levels of psychological stress, exposure to high-frequency noise, a high-salt diet, lack of rest and genetic predisposition. Hypotension If blood pressure becomes too low, the vital centres in the brain, as well as the rest of the tissues of the body, may not receive enough oxygenated blood to continue functioning. Hypotension can progress to shock , in which the body is in serious jeopardy as waste products accumulate and cells die from lack of oxygen. Hypoten- sive states can occur in the following situations: Blood pressure machines found in grocery stores and pharmacies often give higher readings than the actual blood pressure, so people should not be encouraged to use these machines for follow-up readings.The Heart Foundation offers many guidelines for accurate blood pressure measurement. Nurses and midwives are often the healthcare providers most likely to be taking and recording blood pressure, so it is important to always use proper technique and to make accurate records. • Select a cuff that is the correct size for the person’s arm (a cuff that is too small may give a high reading; a cuff that is too large may give a lower reading). • Try to put the person at ease; remember that waiting alone in a cold room can be stressful to the body and mind and can increase the blood pressure. • Ensure that the arm that will be used for the cuff is supported. • Make sure the rest of the person’s muscles are not tensed while the blood pressure is being taken. • Place both the cuff and the stethoscope directly on the person instead of on clothing. • Listen carefully and record the first sound heard, the muffling of sounds, and the absence of sound (the actual diastolic pressure is thought to be between these two sounds).

■■ TABLE 43.1 Categories rating the severity of hypertension

Systolic (mmHg)

Diastolic (mmHg)

Diagnostic category

Normal

<120

<80

High-normal

120–139 80–89 140–159 90–99 160–179 100–109

Grade 1 (mild) hypertension

Grade 2 (moderate) hypertension

Grade 3 (severe) hypertension ≥180 Isolated systolic hypertension ≥140

≥110

<90 ≤70

Isolated systolic hypertension with widened pulse pressure

≥160

the muscle has to generate every time it contracts increase the workload of the heart and the risk of coronary artery disease (CAD) as well. The force of the blood being pro- pelled against them damages the inner linings of the arteries, making these vessels susceptible to atheroscle- rosis and to narrowing of the lumen of the vessels (see Chapter 46). Tiny vessels can be damaged and destroyed, leading to loss of vision (if the vessels are in the retina), loss of kidney function (if the vessels include the glomer- uli in the nephrons) or loss of cerebral function (if the vessels are small and fragile vessels in the brain). Source: Heart Foundation (2010). Guide to Management of Hypertension: Assessing and Managing Raised Blood Pressure in Adults. Available at: www.heartfoundation.org.au/SiteCollectionDocuments/Hypertension Guidelines2008to2010Update.pdf.