Wednesday, December 03, 2008

Can you warm up that ultrasound gel for me?

So, the eternal kvetching point for patients exposed to ultrasound in the Emergency Department is, oooooh, "that ultrasound gel is cold".

I wondered why it feels so cold when it is kept at room temperature? For that matter, why can you touch a blanket when it is at room temperature, and it does not feel cold, whereas a stethoscope, or a metal counter may feel cold.

What is it about the sensation of cold that makes some things which may be 78 degrees seem freezing when your body is at 98 degrees, yet when the temperature of the air is 78 degrees you do not feel cold?

And as another question, does this have any diagnostic significance? Does a patient's response to cold indicate anything clinically? There are conditions with weird temperature findings, so-called hot cold reversal or dysesthesia. For example, ciguatera is a condition in which involved seafood can contain ciguatoxin, which can cause strange neurologic findings, including hot cold reversal.

I went back into the advanced thermodynamics and sensory physiology of my youth and looked all this up...hmmm. Didn't find much.Probably something to do with the specific heat of a substance.

Apparently there is something which scientists are calling the menthol receptor. There is even a knockout mouse!

However, you can actually purchase ultrasound gel warmers. Now that is a posh ER that has those!

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