C H A P T E R 4 3
Drugs affecting blood pressure
661
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).
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:
“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:
• 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).
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.
The evidence
BOX 43.1
■■
TABLE 43.1 Categories rating the severity of
hypertension
Diagnostic category
Systolic
(mmHg)
Diastolic
(mmHg)
Normal
<120
<80
High-normal
120–139 80–89
Grade 1 (mild) hypertension
140–159 90–99
Grade 2 (moderate)
hypertension
160–179 100–109
Grade 3 (severe) hypertension ≥180
≥110
Isolated systolic hypertension ≥140
<90
Isolated systolic hypertension
with widened pulse pressure
≥160
≤70
Source: Heart Foundation (2010). Guide to Management of Hypertension:
Assessing and Managing Raised Blood Pressure in Adults. Available at:
Guidelines2008to2010Update.pdf.
