688
Chapter 19
chemicals that result in infl ammation (see Figure 19–1 and
Figure 7–32), causing the muscles to swell and forcing the
eyeball forward. Sometimes, particular muscles of the eye are
more affected than others, which explains the double vision of
our patient when she gazes to one side.
Therapy
The most important component of the treatment is to lower
the thyroid hormone levels. There are three general approaches
to accomplish this. Removal of the thyroid gland is the most
obvious, but currently the least frequently used approach. Re-
moving a large, hyperactive thyroid gland has defi
nite surgical
risks and is usually not performed unless absolutely necessary.
The drugs
methimazole
and
propylthiouracil
can be used be-
cause they block the synthesis of thyroid hormone by reducing
the oxidation and organifi
cation of iodide (see Figure 11–22).
Although these drugs are effective in some patients, they some-
times lose effectiveness and do not provide a defi nitive cure.
In the United States, a common approach is a more
permanent, nonsurgical treatment. This involves the partial
destruction of the thyroid gland with a high dose of orally
administered
radioactive iodide.
Remember that iodide is a
critical component of thyroid hormone (see Figure 11–22),
and the thyroid gland has a mechanism to trap iodide by sec-
ondary active transport from the blood into the follicular cell.
Radioactive iodide administered to the patient is trapped by
the thyroid; the local emission of radioactive decay destroys
most of the thyroid gland over time. However, the procedure
does not work equally well in all people. In fact, sometimes
patients have so much of their thyroid gland destroyed that
they become hypothyroid. Such people must take T
4
pills for
the rest of their lives to maintain thyroid hormones in the
normal range.
In the short term, while waiting for the treatments to take
effect, patients benefi t from treatment with beta-adrenergic
receptor blockers (see Table 12–9) to reduce the effects of in-
creased sensitivity to circulating catecholamines. This often
helps control the palpitations and increased heart rate, as
well as some of the other symptoms such as nervousness and
tremors. Because proptosis is not caused by the increase in
T
4
, its treatment can be accomplished, if necessary, with anti-
infl ammatory drugs, such as glucocorticoids, or surgery or ra-
diation therapy of the eye muscles.
With adequate treatment, patients generally get better
over time with most, if not all, of the symptoms resolving.
Our patient was treated with radioactive iodide, and all of her
symptoms slowly resolved over several months.
CASE 19–2
A Man with Chest Pain After
a Long Airplane Flight
Case Presentation
A 50-year-old, obese man has just returned from vacationing
in Hawaii. He took an 8-h fl ight during which he sat by the
window and did not leave his seat. In the taxi on the way home
from the airport, he starts to feel chest pain, and has shortness
of breath, increased respiratory rate, and nausea. Thinking he
is having a heart attack (
myocardial infarction
), he asks the
taxi driver to take him to the hospital emergency room.
Physical Examination
An examination of the patient at the hospital indicates that
he has dull, aching chest pain, is clearly upset and anxious,
short of breath, and overweight. He is 68 in (173 cm) tall
and weighs 300 lbs (136 kg). The emergency room physician
immediately orders an electrocardiogram (ECG), primarily to
rule out a heart attack. The ECG shows an increased heart
rate (100 beats per min), but does not show changes consistent
with a heart attack or with left heart failure.
Refl
ect and Review #7
What are the main factors that control heart rate
(see Figure 12–23)? Might any of them explain the
elevated heart rate in our patient?
How might damage to the heart be detected in
an ECG? (See Figures 12–15 and 12–16 for a general
discussion of ECG.)
A chest x-ray is performed in an attempt to determine the cause
of the patient’s chest pain and shortness of breath. The results
indicate no abnormalities such as pneumonia or collapse of
lung lobes (
atelectasis
).
Laboratory Tests
Based on the patient’s history and symptoms, the physician
obtains a sample of the patient’s arterial blood in order to
measure the levels of oxygen, carbon dioxide, bicarbonate, hy-
Table 19–2
Blood Gas, Bicarbonate, and
Hemoglobin Results While Patient
Breathes Room Air
Blood
Measurement
Result
Normal Range
Arterial
P
O
2
60 mmHg
>90 mmHg
Arterial
P
CO
2
30 mmHg
35–45 mmHg
A rterial pH
7.50
7.38 –7.45
Bicarbonate
22 mmol/L
23–27 mmol/L
Hemoglobin
15 g/dL
14–18 g/dL
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