Emergency Medicine Q & A, 2009, Pg

Emergency Medicine Q & A, 2009, Pg


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c. Multiple studies have shown that injuries to the coronary arteries are the most important factor in
determining outcome after penetrating cardiac injury. Injury to a single chamber (even if comminuted) or to
multiple chambers is less likely to be fatal than injuries that involve a major coronary artery.
54. Match the radiographic \ufb01nding with the appropriate diagnosis:
a. \u201cThumbprint\u201d appearance of the epiglottis in a 34-year-old\u2014sublingual abscess.
b. Anterior displacement of C2 on C3 in toddler\u2014locked facets.
c. \u201cSteeple\u201d-shaped trachea in toddler\u2014epiglottitis.
d. Prevertebral space swelling of neck in an asymptomatic infant\u2014artifact.
e. Air in intestinal wall of newborn\u2014intussusception.
... CHAPTER 1 Resuscitation 19
The answer is d. Epiglottitis is not only a disease of children. Older patients and adults may present with a history
of sore throat, fever, dysphagia, and hoarseness, without pharyngitis or neck tenderness. Epiglottitis is caused by a
variety of organisms including Haemophilus in\ufb02uenzae and Streptococcus species. The infection can progress to an
epiglottic abscess. In laryngotracheobronchitis, AP views of the trachea often show subglottic narrowing (the steeple
sign). Lateral neck \ufb01lms may demonstrate a widened hypopharynx. Retropharyngeal swelling is often an artifact:
expiration causes the prevertebral soft tissue to widen. In the symptomatic child, usually from age 6 months to
3 years, such swelling is diagnostic for a retropharyngeal abscess. Pneumatosis intestinalis is diagnostic of
necrotizing enterocolitis in the premature or stressed neonate.
55. Choose the correct statement about the oxygen\u2013hemoglobin dissociation relationship:
a. Increasing Pco2 results in shift of dissociation curve to left.
b. Decreasing 2,3-DPG results in shift of dissociation curve to left.
c. Decreasing hydrogen ion concentration results in shift of dissociation curve to right.
d. Increasing Fio2 results in shift of dissociation curve to right.
e. Increasing temperature results in shift of dissociation curve to left.
The answer is b. The inspired oxygen concentration has no direct effect on the oxygen\u2013hemoglobin dissociation
curve. Increasing Pco2, increasing temperature, increasing hydrogen ion concentration (decreasing pH), and
increasing 2,3-DPG shifts the curve to the right and results in an increase in oxygen tissue delivery.
56. Choose the correct statement regarding the pathogenesis of cerebral ischemic injury:
a. Most structural damage occurs during reperfusion.
b. Decreased intracellular calcium is an important contributor to neuronal cell death.
c. Xanthine oxidase, which produces oxygen free radicals, is protective against cerebral damage.
d. Excess protein synthesis contributes to ischemic injury.
e. Restoring blood \ufb02ow to an ischemic area lessens the chance of cerebral damage.
The answer is a. High cytosolic calcium is a major event leading to cell death. Calcium activates membrane
phospholipases and contributes to degradation of both membrane and DNA. The presence of xanthine oxidase, an
enzyme that produces oxygen free radicals, contributes to irreversible cell death. Suppression of protein synthesis
contributes to ischemic injury. Restoring blood \ufb02ow to an ischemic area contributes to neuronal injury and cell
death.
57. Nitroglycerin relaxes vascular smooth muscle. At low doses, its effects are best seen in:
a. Coronary arteries.
b. Veins.
c. Large arteries.
d. Small arteries.
e. Capillaries.
The answer is b. At lower dosages, nitrates are primarily venodilatators. They effectively decrease pulmonary artery
occlusion pressures (PAOP) and are therefore very effective in the initial therapy of acute pulmonary edema. At
higher dosages IV nitroglycerin also causes arteriolar dilatation that results in decreased blood pressure and
afterload. The afterload reduction effect appears to be more pronounced in hypertensive patients. Nitrates act as an
exogenous source of nitric oxide, which causes vascular smooth muscle relaxation and may have a modest effect on
platelet aggregation and thrombosis.
20 Emergency Medicine Q & A: Pearls of Wisdom ...
58. The therapeutic goal in treating a patient with shock is to:
a. Establish a normal CVP pressure.
b. Replace the estimated blood loss with 3 times the volume of crystalloid.
c. Obtain a normal urine output of 0.5\u20131.0 mL/kg/h.
d. Obtain a blood pressure >120/80 mmHg.
e. None of the above.
The answer is e. The treatment goal for shock is to restore adequate tissue perfusion. This can only be judged by
the effects of therapy on all the major body organs: brain (CNS function); vascular system (blood pressure, pulse
pressure, skin color); and kidneys (urine output). No single organ system should be used as the determinant of
adequate tissue perfusion. Other factors may mask abnormal function, such as glycosuria increasing urine output or
intoxication masking CNS function. Failure to respond to therapy or clinical deterioration should lead one to
suspect complicating factors (unrecognized coexistent disease, hypoadrenalism, gastric distension, pneumothorax,
cardiac tamponade, etc.).
59. Prolonged hypoxia can result in:
a. Pulmonary vasodilation.
b. Reduced proportion of pulmonary blood \ufb02ow to the lung apex.
c. Coronary vasoconstriction.
d. Decreased right ventricular end diastolic pressure.
e. Increased mean circulatory \ufb01lling pressure.
The answer is e. Hypoxia causes a sustained generalized pulmonary vasoconstriction that increases pulmonary
arterial pressure. This increased pulmonary arterial pressure tends to increase perfusion in the lung apex by
minimizing the effects of gravity on pulmonary perfusion. Increased pulmonary vasoconstriction initially decreases
cardiac output, leading to re\ufb02ex increases in salt and water retention, leading to increased extracellular volume and
subsequent increase in mean circulatory \ufb01lling pressure, which contributes to an increase in right ventricular end
diastolic pressure and an increased preload that helps the right ventricle compensate for the increased afterload.
Prolonged hypoxia also causes vasodilation.
60. Properly performed closed-chest cardiac massage provides approximately what percentage of prearrest
cardiac output?
a. 15%.
b. 25%.
c. 45%.
d. 60%.
e. 85%.
The answer is b. Cardiac output declines by 75% during CPR. Diastolic blood pressure, which is the main
determinant of coronary blood \ufb02ow, falls from 40 to 20 mmHg. Epinephrine increases vasomotor tone and helps
preserve diastolic pressure. Coronary and cerebral blood \ufb02ow during properly performed CPR are reduced to 5%
and 10%, respectively, of prearrest blood \ufb02ow.
... CHAPTER 1 Resuscitation 21
61. A 33-year-old man presents comatose with no available history. You secure the airway, check blood glucose
(90 mg/dL), administer naloxone, and assess for trauma. You receive the following laboratory results:
sodium, 148 mEq/L; chloride, 125 mEq/L; HCO3, 17 mEq/L; potassium, 5.8 mEq/L; BUN, 18 mg/dL;
creatinine, 1.1 mg/dL; serum osmolarity, 305. His condition is most likely due to:
a. Addisonian crisis.
b. Methanol ingestion.
c. Salicylate ingestion.
d. Cyanide ingestion.
e. Alcohol ingestion.
The answer is a. Calculation of the anion gap [Na+ \u2013 (Cl\u2013 + HCO3)] helps differentiate metabolic acidosis. A
normal anion gap is less than 12. Causes of normal anion gap acidosis include renal tubular acidosis, Addison\u2019s
disease, diarrhea, and ureterosigmoidostomy. Causes of a high anion gap acidosis include methanol, uremia, DKA,
paraldehyde, isoniazid, lactic acidosis, ethanol, salicylates, and cyanide.
62. A 65-year-old man is receiving a \ufb01brinolytic agent for an acute anterior wall myocardial infarction. He
develops a wide complex regular ventricular rhythm with a rate of 90/min. His blood pressure is
120/80 mmHg and he is asymptomatic. You should now:
a. Continue close monitoring, but give no