sulfate is a respiratory depressant and may lead to hypoventilation. It does
not act as rapidly or as effectively as nitroglycerin in preload reduction. (c)
Nitroprusside is a mixed venous and arteriolar dilator; it reduces both pre-
load and afterload. It can be used in patients with acute pulmonary edema
but is typically reserved for individuals with a systolic BP > 100 mm Hg who
fail to respond to adequate doses of standard preload reducers (eg, nitro-
glycerin).(e)This patient is hypoxic with an oxygen saturation of 85% and
requires supplemental oxygen. In the acute setting this patient should be
placed on a nonrebreather with 100% oxygen flowing through the mask.
18.The answer is e.(Rosen, p 1069.)The patient’s ECG shows a sinus
rhythm at a rate of 70 with first-degree heart block.First-degree heart block
is defined as prolonged conduction of atrial impulses without the loss of any
impulse. On an ECG this translates to a PR interval greater than 200 ms
with a narrow QRS complex (less than 120 msec). First-degree heart block is
often a normal variant without clinical significance, occurring in 1% to 2% of
healthy young adults. This variant requires no specific treatment.
(a)A pacemaker is considered in patients with a second-degree type II AV
block or third-degree complete heart block. (b)An observation period is not
required, as the prolonged PR interval is a normal variant in this individual.
(c)Aspirin and cardiac biomarkers are sent for patients thought to have ACS.
(d)There is no evidence that the ECG leads are placed incorrectly.
19.The answer is e. (Rosen, pp 1210-1224. Tintinalli, pp 386-391.)
D-dimeris a degradation product produced by plasmin-mediated proteolysis
of cross-linked fibrin. There are two types of D-dimer assays. Those with
greatest sensitivity are the enzyme-linked immunosorbent assays and the tur-
bidimetric assays. Because of their high negative predictive value, D-dimer lev-
els are typically used to rule out the diagnosis of PE.In conjunction with a low
pretest probability, a negative D-dimer is predictive of not having a PE. Therefore,
in this patient with a high probability of PE (eg, exhibiting dyspnea, chest pain,
tachycardia, malignancy), it is likely that the D-dimer will be abnormal.
(a)Arterial blood gas has a very low predictive value in a typical pop-
ulation of patients in whom PE is suspected because they typically have
some pulmonary pathology that affects pulmonary gas exchange more than
a PE does. Most patients with a PE have a normal PaO 2 .(b)Oxygen satu-
ration is rarely depressed and not very useful in the workup of PE. (c)The
most common ECG findings are tachycardia and nonspecific ST/T-wave
abnormalities. Occasionally, signs of right heart strain are noted. (d)Chest
34 Emergency Medicine