Friday, January 25, 2008

An Arm and a Leg

You examine a 2-week old male. Oddly, the blood pressure in the right arm is higher than the blood pressures in the legs. You can barely feel a femoral pulse, and when you palpate both the femoral and right brachial pulses, the femoral one is delayed.

Challenge 1: What is your diagnosis?

You examine a female neonate who was delivered 8 hours ago. Her respiratory rate is elevated and she is cyanotic. You put on some pulse oximeters and oddly enough, the oxygen saturation in her right arm is higher than that in her legs.

Challenge 2: How can this be the case?


Alex said...

aortic coarctation?

what if you got the opposite of case 1 in an young asian woman?

Craig said...

An Arm and a Leg

For the first case, this is classic coarctation of the aorta. In this disorder, the aorta narrows where the ductus arteriosus inserts, though there may be some anatomic variability. This is distal to the origin of the brachiocephalic trunk; as a result, the right arm will often have arterial hypertension whereas the lower extremities will have normal or low blood pressure. There are often poor femoral pulses and a delay in the femoral pulse. This is more common in boys.

For the second case, the presentation of tachypnea, cyanosis, and signs of pulmonary hypertension suggest persistent pulmonary hypertension. But how can you get decreased saturation at different sites in the body? Most likely, the neonate is shunting blood from the right to the left via the ductus arteriosus. The ductus arteriosus inserts distal to the origin of the brachiocephalic trunk so the right arm will have a higher oxygen saturation than the lower extremities. Blood may also be shunted R to L via the foramen ovale.

Sources: Wikipedia, AccessMedicine