I Am Still Alive

Feb 24 2011 Published by under [Medicine&Pharma]

But I would kill for a nap. The week covering inpatients drags on, and I have not gotten more than 5 hours of uninterrupted sleep. I feel very Disney, and not in a princess way.

What has kept me up on the phone? Clots.

The bane of a nephrologist's existence is access for dialysis. If we can't get blood flow, we can't do much. We usually use a drug called heparin to prevent clots from forming in our plastic tubing, but some patients develop a reaction to it called heparin-induced thrombocytopenia (HIT for short).

We switched to something called regional citrate anticoagulation. To understand this protocol, you need to know how blood clots. Cell fragments called platelets circulate in the blood, looking for damaged vessels. When they sense damage, they clump on the spot, releasing chemicals that initiate the thrombin cascade (more about clotting Here). These clotting factors require calcium to work, so removing calcium from blood will keep it flowing. Of course, a certain amount of calcium must be in the blood for normal function of heart, nerves, and other important organs. If we try to remove calcium in the circulation, the body works to remove it from the bones and fix the problem.

We use a drug called citrate to bind calcium. Citrate enters the dialysis circuit where we pull the blood out of the patient. At the same time we put calcium back into the central circulation. Calcium levels are then measured every few hous in the dialysis circuit (where we want it barely detectable) and from the patient (where we want normal blood values). The IV drips of citrate and calcium must be adjusted based on the lab measurements, especially during the first day.

So what happens if citrate gets into the patient? The liver metabolizes it into bicarbonate, which can then become carbon dioxide and water.

We have not used this anticoagulation protocol much, but it is the first line treatment at many other places. As we use it more, it will get easier and require fewer calls.

In the meantime, I'm looking forward to a night of shut-eye.

- Posted using BlogPress from my iPad

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