Thursday, February 03, 2005


So today one of my patients says to me, "I'm really thirsty, can I have a drink." Now my general response is no. This is because before surgery we keep patients NPO or "nulla per os" which is Latin for nothing by mouth usually for a least 8 hours before surgery, or sometimes from midnight the night before. This is because one of the the most dreaded complications of anesthesia is aspiration. This is when stomach contents get into the lungs. This can cause a chemical pneumonitis which can result in lung damage, ranging from minor effects up to and including death. This is obviously preventable with prescheduled surgery. Anyway I didn't think too much about it, it's actually a pretty common thing for people to say before their surgery and reassuring that they didn't eat or drink before their surgery.

Later I'm giving the resident in the room a break while we're on bypass and I look at the intraoperative lab work. The hematocrit (aka "crit"), or percentage blood count, is 41 on the slip -- it's circled and the tech or perfusionist or someone had written "Outstanding!" next to it. This struck me as kind of funny. Someone was impressed enough with the lab value to comment about it.

A "normal" hematocrit is generally listed at 42-54 percent, but in my experience cardiac surgery patients tend to be a bit anemic and run in the 30-40 range. Now after you go onto bypass the hematocrit tends to drop a bit because the bypass pump is primed with fluid so the blood volume gets diluted and a hematocrit above 27 tends to be acceptable for most patients. Some patients start low and drop further on bypass and receive blood as a result. So 41 is really doing pretty good. I look back to the first set of labs before the patient is asleep and the crit is 48. Again still within the normal range, but quite a bit higher than we usually see for our cardiac patients. Explanations for this are many, and include disorders such as polycythemia vera where the blood is abnormally thick. In this clinically setting the most likely diagnosis is dehydration. In this instance, it was caused by us, in our instructions for the patient not to eat or drink.

So when this patient said he was thirsty... he really meant it.

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