Tuesday, October 7, 2008

And Now For Something Completely Different

Back to science, which is what this blog is supposed to be partly about. We've been fiddling around, trying to get a working rat hypothermia model that's clinically relevant. We think we've got it now, and yesterday we tried our new system, the Arctic Rat (TM) suit, while monitoring both rectal temperature (body core temperature) and temporal muscle temperature ( a surrogate for brain temperature) in a rat under general anesthesia. Here are the results.

A couple of notes. The temperature is reported, obviously, in deg C. The x-axis time points are every five minutes, so the experiment went from 0 to 90 minutes. Target temp was 32 deg C, which is as far as we intend to go with the current study. That's equivalent to 89.6 deg F, or 9 degrees F lower than body temp. The top two curves are core temp and temporal muscle temp, and they correlate very nicely. The third curve down is the ambient temp (yeah, it's hot down here). The next curve is tank temperature; this is the temperature of coolant we used. The bottom curve is the difference between the two temps, which got tighter quickly and stayed that way; it was always under our max acceptable diff of 2 deg C.

What I'm happiest about is that we were able to get to our target temp quickly and then keep it pretty much on target with minimal adjustments of tank temperature. This model is almost ready for prime time. We have to tweak our sedation method and make sure the core and temporalis temperatures correlate with brain temperature, but once all that's done we're In Like Flynn. Hypothermia for brain ischemia is hot, and we're eager to explore not only its therapeutic benefit but also just exactly what it does at the molecular level.

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