Medschool MCQ4

MCQ4: A 62-year-old woman has had atrial fibrillation since experiencing a myocardial infarction(MI) 7 months prior. Two weeks ago she was hospitalized following a car accident in which she suffered a compound fracture of her left femur and several severe contusions. She nowvreturns to the emergency room with right flank pain, hematuria, and left-sided paralysis. These newly developing problems are most likely the result of which of the following?

(A) air embolism from the compound

fracture

(B) bone marrow embolus from the frac-

tured femur

(C) fat embolism from the fractured femur

(D) systemic thromboemboli from the left

atrium

(E) venous thromboemboli from the deep

leg veins

Explanation:

(D) Atrial fibrillation produces turbulence that

is conducive to the formation of thrombi

which can then embolize throughout the sys-

temic circulation. In this patient the right flank

pain and hematuria and left-sided paralysis

suggest that thromboemboli traveled to the

right kidney and the brain, respectively.

Embolism of air (choice A) has variable effects,

although small amounts are typically incon-

sequential. Larger volumes (~ >100 mL) can

obstruct arteries and lead to ischemia and

necrosis; an air embolism that lodges in the

right heart may lead to sudden death.

However, air embolism is rare and is not the

most likely event in this patient. Bone marrow

embolism (choice B) can occur following a

broken bone or cardiac resuscitation, but typ-

ically will have no clinical consequences.

However, fat embolism (choice C) from a

broken long bone or traumatized areas of adi-

pose tissue can, when severe, produce clinical

manifestations. These follow the trauma by

about 1–3 days and usually include dyspnea,

skin rash, and acute neurologic changes. In a

few cases this has been fatal. Venous throm-

boemboli from deep leg veins (choice E) could

not get past the lungs (with the unusual

exception of paradoxical embolism in a person

with a septal defect) so could not reach the

kidneys or brain to cause the effects reported

for this patient.