Thursday, July 5, 2007

Aneurysms..and Transplants?

This past week was basically a continuation of what I blogged last week. Except that the scope of what I observed was a bit more interesting as compared to the seemingly mundane kidney transplants. So obviously to prolong the life of a patient awaiting kidney transplant, which is in the order of 5 -7 years, the patient has to undergo dialysis every 3 days to purge out urea and other waste products. I observed minor operations intended to either construct or remove blood vessels(Fistula) necessary for dialysis. The first and initial route of dialyzing blood is by peritoneal dialysis. This is done by tapping into high pressure blood from peritoneal artery which is a major vessel with blood being pumped in and out of the heart. While this is reasonable method of drawing blood for dialysis, it is however a short-term approach typically used before an arterovenous fistula (AVF) construction. This is because the peritoneal approach requires making a permanent opening through the neck area which exposes the subject to wide array of infections. A way to get around that is to construct a graft that can provide access to blood under high pressure, while minimizing chances of infections. One can directly poke into a major artery, but poking to into it every 3 days would be dangerous to the patient; a bleeding from artery can be life-threatening. What is normally done to preclude the need to expose the subject such a high risk is to construct a graft by attaching a vein, which are abundant in the body, to a major artery such as the brachial artery (in the arm). This is referred to as arterovenous fistula (AVF) construction. Once the AVF is healed, blood is then drawn by poking the vein (graft) which is less life-threatening as it is abundant and is not a major blood supply vessel. So I observed one of these procedures and a day later observed a De-construction of it in another case and wondered aloud what big arm swelling was(Aneurysm).

As it turns out, repeated poking the graft vein in order to dialyze a patient is like 'repeatedly hitting a car tire against a curb' which effectually results in a bubble-like swelling on the tire. So after years of dialysis, a diabetic patient develops arm aneurysm..I am sure some of you have seen it in the past. When there's no longer a need for this AVF graft, i.e., the patient has gotten a kidney transplant, the aneurysm a.k.a AVF graft has to be removed. There are 2 majors reasons why this is done. One is that aneurysms (distension of vein), increases the cardiac output, necessary to maintain physiological blood pressure. This makes the heart work harder than it should. In addition, increased blood pressure will also aid in further distending the swelling, which can rupture the graft. When this occurs, the subject can bleed to death since the aneurysmic vein is grafted to a brachial artery, a major blood vessel. I hope you have learned that aneurysms are not only aesthetically unpleasant but are also very dangerous....

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