nbme1 - mimi2009

[ArchivalUser]

A 40-year-old man is brought to the emergency department 1 hour after a high-speed motor
vehicle collision. On arrival, he is awake and alert but has severe pain over the sternum. His systolic
blood pressure is 80 mm Hg, pulse is 80/min, and respirations are 10/min. An ECG shows multifocal
premature ventricular contractions but no ST-segment changes. His PO2 is 100 mm Hg. After 1 L of
lactated Ringer's solution is administered, his PO2 decreases to 60 mm Hg while breathing 4 L/min
of oxygen by nasal cannula. Pulmonary capillary wedge pressure has increased from 14 mm Hg to
24 mm Hg (N=1“10). Which of the following is the most likely explanation for the patient's poor
response to fluid resuscitation?
A ) Inadequate administration of fluids
B ) Myocardial contusion
C ) Myocardial infarction
D ) Pulmonary contusion
E ) Traumatic rupture of the aorta

can anyone help me with the answer! i do have the right answer but i'm not convinsed!

[ArchivalUser]

I think its B)

[ArchivalUser]

DD

[ArchivalUser]

sorry i meant myocardial contusion ( BB).

[ArchivalUser]

u guys r right but why B!! its a myocardia contusion but how would that affect systolic BP and why is the pt not responding to giving him fluid??

[ArchivalUser]

EKG doesn't show any sign of MI, so C is out. Before fluid resuscitation, paiteint has a normal Po2, then D is unlikely. Raise in PCWP indicates a heart failure (cardiogenic shock), among the remaining options B is the most likely answer. Mechanism of trauma and findings in EKG also is in favor of D, although, non-specific.
Rupture of aorta could happen in MVA or fallings. If the site of rupture is asceding aorta, death would be immediate, if the site is aortic arch then we would have a clot formation, aneurism, and very unstable patient even before fluid resuscitation.

[ArchivalUser]

he has developed congestive heart failure secondary to contusion and has gone into pulmonary edema

[ArchivalUser]

Come on mimi,
myocardial contusion causes akinetic cardiac muscle ( dysfunction cardiac muscle) lead to decr.CO and decr. systolic BP.

if you give fluid may cause pulmonary edema ( i do believe this pt. has pul. edema), increase PCWP and hypoxia, so that why drop PO2 ( from 100mmHg to 60mmHg).

correct me guys, if im wrong.