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Cool New Ideas to Save Brains
An anonymous reader writes "An estimated 700,000 Americans suffer strokes each year. Researchers are looking for ways to cool the head of a stroke victim while keeping the rest of the body at normal temperature; they've developed a nifty cool helmet to accomplish this. Cooling the brain essentially puts the brain in 'pause' mode, giving doctors time before damage from oxygen starvation occurs. This is similar to the way in which near-drowning victims do much better if they are in freezing water rather than in warmer water."
Considering that the blood is circulating through the brain multiple times per minute carrying warmer fluid from elsewhere in the body, and that the heat
would have to be removed through the skull (not sure what the thermal conductivity of bone tissue is), it makes me wonder how effective this would really be at cooling the interior regions of the brain without cooling the other parts of the body as well. I would suspect it would only be marginally useful at cooling just the outer portions, and even that would be countered by the warmer blood flowing through it. I'm sure it sounds real good in their brochure.
At the same time, the amount of blood flowing through your hand, as opposed to the amount of blood flowing through your head, is substantially lower. So, your hand in ice water will chill more easily, since it has no outer bone casing, and less of an incoming source of heat, whereas your head has substantially more blood flowing to it, and, as he pointed out, a skull around the brain.
Another thing to consider... Hold your hand only in ice water, and see if your arm doesn't become cold. As the original poster pointed out, the blood flowing out will be quite cold, and thus cool the rest of the body.
And a final concen not mentioned, is the fact that the body's thermostat is up in the brain. When somebody is suffering from heat stroke, putting ice on the back of their neck will make them FEEL cooler all over, and actually worsen the situation, since it chills the brain and causes it to think "My body is cold! Must increase heat production!"
Overall, if it was JUST the brain, no problem. But since the body is an integrated system, I wonder if this is really a proper approach.
@Whee
So, I have been attending vicariously via conversations with friends and family that are at the meeting in San Diego. It turns out that yes, indeed one gets a royally painful headache when wearing these things, but when given the alternative......
Actually, TPA treatment is dramatically effective if given within the time window of effectiveness, but as the article alluded to there are other issues with treatment of stroke via TPA, specifically one has to ensure that the stroke is an embolic stroke (meaning a blocking off of blood flow) as opposed to a hemorrhagic stroke (meaning a leak in blood vessels of the brain) as TPA can worsen a stroke that is hemorrhagic in nature. So, careful diagnosis becomes critical. Additionally, TPA administration itself can be a little tricky and can cause a fair risk of damage, but again the alternative.....
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When I got my SCUBA certification, we had to break some ice to get into the water. I think it ran from 38-42 F depending on how deep we went in the middle of the lake.
I had a hood on, but five minutes in that kind of water and the hood isn't so good. You get an awful ice-cream headache. Then you get so numb you can barely feel your face. Then your regulator freezes up. (then you practice your emergency decompression ascent)
So yeah, external cold source to the head gives a bad headache, but not for too long.
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There is currently research in cooling to prevent brain damage in infants that suffer hypoxia (oxygen starvation) during birth. Hypoxia occurs when the baby does not get an adequate oxygen supply to the brain during labour, which is usually as a result of fetal distress or pinching of the umbilical cord. Usually, an infant in intensive care is put under lights to keep body temperature up, but in one study (Infant Cooling Evaluation at the Royal Womens Hospital in Melbourne, Australia) infants are cooled simply by turning the lights off. There is not sufficient data to report results of this study at present, but resutls in animals have been very promising.
A similar technique has been used for cooling the whole body of a patient. This is done by letting the patient breathe a oxygen saturated liquid such as LiquiVent. Normally, when you apply liquid breathing, you pre-heat the liquid to body temperature, but in this case you could use a lower temperature. The total area of the lung alveoli is about 100 square meters. Compared to the area of the head (as used in the helmet approach), the area available for heat transfer is many times greater, which means that the cooling is done much faster.
Of course this technique is not useful in an ambulance, due to the fact that you have to apply local anasthetics to the lung in order to prevent the cough reflex when the liquid enters the lung/lungs. Also, you have to put the patient in a respirator, because breathing liquid is so taxing on the diaphragm muscles, that all your energy is spent on breathing - you can't do anything else.
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