widening of the QRS complex.Eventually the tracing assumes a sine-
wave pattern,followed by ventricular fibrillation or asystole.
(a)ECG manifestations of hypokalemia include flattening of T waves,
ST-segment depression, and U waves. (c)Hypocalcemia manifests as QT
prolongation, whereas hypercalcemia (d), manifests as shortening of the
QT interval. (e)There are no classic ECG findings with hyponatremia.
5.The answer is a.(Rosen, pp 1000-1004.)The patient presents with a
primary spontaneous pneumothorax (PTX),which occurs in individuals
without clinically apparent lung disease. In contrast, secondary sponta-
neous pneumothorax occurs in individuals with underlying lung disease,
especially chronic obstructive pulmonary disease (COPD). For otherwise
healthy, young patients with a small primary spontaneous PTX (less than
20% of the hemithorax), observation alone may be appropriate. The intrinsic
reabsorption rate is approximately 1% to 2% a day, and accelerated with the
administration of 100% oxygen. Many physicians observe these patients for
6 hoursand then repeat the chest x-ray. If the repeat chest x-ray shows no
increase in the size of the PTX, the patient can be discharged with follow-up
in 24 hours.Air travel and underwater diving (changes in atmospheric pres-
sure) must be avoided until the PTX completely resolves.
(b)Needle decompression is a temporizing maneuver for patients with
suspected tension PTX. (c)Tube thoracostomy is used in secondary sponta-
neous PTX, trauma PTX, and PTX > 20% of the hemithorax. (d)Unless
there is a change in his status, the patient does not need to be observed for
another 6 hours. (e)A pleurodesis is an operative intervention to prevent
recurrence of PTX. It is performed on patients with underlying lung disease.
6.The answer is d.(Rosen, pp 1236-1237.)Esophageal perforationis a
potentially life-threatening condition that can result from any Valsalva-like
maneuver, including childbirth, coughing, and heavy lifting. Alcoholics are
at risk as a result of their frequent vomiting. The most common cause of
esophageal perforation is from iatrogenic causes, such as a complication from
upper endoscopy. The classic physical examination finding is mediastinal or
cervical emphysema.This is noted by feeling air under the skin on palpa-
tion of the chest wall or by a crunchingsound heard on auscultation, also
known as Hamman sign.Radiographic signs of pneumomediastinum can be
subtle. Lateral displacement of the mediastinal pleura by mediastinal air cre-
ates a linear density paralleling the mediastinal contour. On the lateral pro-
jection, mediastinal air can be seen in the retrocardiac space.
26 Emergency Medicine