Transcript Video What is a Normal Temperature and What is Therapeutic?Prof. Michael Holzer < Back to Boundaries of Temperature Session 1: The Temperaturist What is a Normal Temperature and What is Therapeutic? Presented by Professor Michael Holzer it is now my great pleasure to introduce the next speaker to you. Next speaker is Professor Michelle Holzner. He's an internist at working at the department of Emergency medicine at the university hospital in Vienna. His research focus over decades I would say some category best and re perfusion following categories best initially with Professor Later with Willie Beringer and many others. He is one of the investigators of the Haka trial that led us all cool patients down following out of hospital category rest. And he's not only working in the clinical field but also in the experimental field on global cerebral ischemia categories and re perfusion and temperature management. Mikhail. The stage is yours. We are very much looking forward to your presentation now. Thank you very much for the nice introduction and the topic today is not so much on cooling but more on what is a normal temperature and what is a therapeutic temperature. So I will talk a little bit on thermoregulation very shortly because Professor Keller already touched it. I then go to history of measuring temperature and definition of normal for miA and then definition of different temperature levels that we are using clinically. And then at the end we discuss maybe which the temperatures therapeutic. So first start with thermal regulation. You have seen that maybe a little bit already we have this central regulator in the hip autonomous and that is regulating the temperature. I have not very much to add to this. Maybe just a comment on the behavior things behavior means that when you're feeling cold you're getting grab your pull over, grab your blanket, That's behavioral change for example, that so that's a very complex thing. Uh thermal regulation is not only shivering, it's not only sweating but it also changes your behavior. You go inside because it's cold outside. That's initiated by the changes in the hypothalamus. And if you are moving for example working in a hot environment, considers on that slide. Then you have heat production and you have to get rid of this heat production in your muscles. So you increase the um blood flow in the muscles. And you have regulation in the skin to get the heat from the inside to the outside region. And if you're not possible to get rid of this heat then you have a problem. Then you get overheated. Then then your body temperature will increase, then you will start sweating and you can lose a lot of fluid and that negatively influences your regulation kept capacities against the heat for example. So then in the end it could be that you collapse because you have to less fluid working in a hot environment. And this table regulation set points can be changed by medication and that's a central acting uh analgesic naval palm. And you can see that the shivering threshold, the temperature where you start shivering can be reduced with this medication, we have a lot of medication that can change these set points like opioids for example. Also it use the shivering threshold and it's not a real set point that's fixed, but it's influenced by various things. So let's switch to the history of measuring temperature and definition of normal for me. And that's quite interesting thing Already, years before Christ Hippocrates used defined measuring temperature by holding their hand on a human being and that's what we also do now with my Children for example, and they say, Oh I'm feeling so federal. And then I touched them and said, no you're not federal, you have to go to school. So that's what we always still using. And then in 1612 they invented the telescope. And you've seen a picture here of the telescope. It's uh airfield tube which is stuck into the in water. And what they knew was that air would change this volume with temperature. So they had a bulb which you had to put in mouth and then the water had was expelled from the tube. And then you have grading on the tube and therefore you could read some sort of temperature. It was quite complicated. So then they, a few years later invented the first thermometer, which was a tube, glass glaciers tube filled with alcohol not to drink but to measure temperature. And that was quite useful. And uh then they invented Fahrenheit and went to the farmer's scale on Celsius had the first uh Scale based on science or scientific data. And he had two defined set points. He had freezing point and he had the boiling point freezing with zero boiling 100 and it was just divided in 100 parts. That was the first uh calibration of 10 of 13 m. That has been done Already 18, 21 term couple thermometer has been invented where you found that you have two different um metals put together and have temperature on that, that there is a current on that and that you can then show that on On a motivator. And in 1960 for the non contact radio mater was invented. That's what we're using now for tim panic temperature for example. And the first large study on human temperature and the to define what is the normal human temperature was done by Dr. A. German physician. And he did a lot of studies and he published it in this publication from 1870 And he had almost 25,000 patients in his outpatient clinic. And he measured temperature in those patients and he measured axillary temperature. So what we are talking about with Wonderlic temperatures, it's axillary temperature. But the precision of the measurement is quite questionable because the thermometer that he used at this time as only one left from this time. Uh it measures 1.5 to 2 degrees different from digital thermometers. And it also measures different from thermometers that were used at that time. So we don't really know if the temperature that he defined which is, 30 sweet. Um It's it's depending on my uh work on hypothermia, you know. Um So and we also don't know if he how he gets to these values. There is no real publication. There's just a book where he reads and writes a lot of things on that. But there is no statistical plan. There is no primary data where we can see how he did this. But there is a systematic review of the literature and what you can see here is that it's quite different where you measure temperature. If you measure temperature in the cellar. It's quite different when you measure it orally or rectally. There is always a different temperature to measure. And it's different from men to women. So women tend to have a little bit lower temperature and you also have a circadian rhythm of temperature in the morning. It's higher than in the evening, for example, overall. So we can say each side where we measure temperature has its own range. And the normal range found at the for example, is significantly different from that really measured. And so we need a little bit more different different understanding of that. And if you look at this chart here from one patient that we studied during therapeutic hypothermia. Um we cool down the patient and measure different temperatures and the one that's below ist is the tim panic temperature is not measured by an infrared thermometer. It's just there was a promise to put in the oral uh channel and you could see that there is quite a big difference between between these temperatures. But the central temperatures like pulmonary artery temperature or soft shell temperature or the sickle Temperature, they are quite narrow together. Maybe the bladder temperature is just lagging behind a little bit 20 minutes. But then in steady state they are quite the same. But it's not only the measuring side where you have different temperatures, but it's also within the organs that you have different temperatures. That's just the recent publication from this year where they uh analyze with M. R. I. With respect apostrophe. The temperature within the brain and in the morning, afternoon and evening of healthy subjects. And what they found was that the temperature within the brain are quite different. Uh when they go to the central region they are a little bit higher. Maybe if you're going to uh more peripheral regions, they are lower in the central region. Whether between the hemispheres they have a very low temperature. So it's not really clear what is the brain temperature? What is the party party temperature? So we really have to define it a little bit. So when we define different temperature levels, We first have to define normal for me in the first line, is that what Wonderlic proposed was 36.25 was the lower limit. So the seven degrees was the mean temperature that he said and the upper limit was 7 37.5 degrees. That is what we knew for for most of the time when my Have fever for example, that's higher than the upper limit. And then a study by Markowitz in 1992 just reanalyzed the data from uh from and its own studies 150 patients. And they said it looks like that the temperature of one is a little bit different but they didn't measure the temperature in the axillary, they measured it in the oral cavity in this study. So The upper part is the temperature from the axle, which might be not wrong because the thermometers have been wrong and the lower temperature might be a temperature from the oral cavity cavity which is 36.8. But what is the central temperature? There are no studies up to now where we define the normal patients the central temperature because it's quite different difficult. So for normal things, when we are talking about normal for mia we should refer to 36.8 as the mean temperature and maybe the lower limit because that's not defined by micro week by 36.0 degrees, which is according to the range of one click and the upper limit to 7 37.7. And if you're using hypothermia, there have been different levels proposed. We have mild hypothermia which is from 34 to 36°. We have moderate from 28 to 32 deep from 18 to 28 profound and ultra profound. Which is very seldom used uh in human medicine. We use deep hypothermia for example, at aquatic arch surgery for example. But uh normally in patients after categories when we want to cool them down or in babies after ah asphyxia, we normally use mild to moderate hypothermia. So the next question is which temperature is therapeutic? And I would suppose that we call every temperature level therapeutic that leads to a clinical effect in a patient or animal. And that would be some sort of definition that we can use. And if you look at studies where hypothermia has been used, this is systematic review, meta analysis of animals that were resuscitated from cardiac arrest from 1991 to 1919. Um And you can see here that in most of these studies there was a positive effect of hypothermia and T. T. M reduced, namely the temperature of 32 to 34 degrees. Which was used in these animals compared to 37 degrees mean temperature or 36.5 to 39 degrees. This reduced the mortality by about 70%. And I think that's an therapeutic temperature But also this is an therapeutic temperature but 40° used for treating cancer patients with uh soft tissue Sarcoma and what they did, they did local hypothermia in combination with um chemo, radio chemotherapy. And you could see that the uh Relapsed three days or the mortality in this in this group was reduced when they using hypothermia because the tumor was more reduced with hypothermia. But that's also a therapeutic level of hypothermia. So I will come to my conclusion. What is normal temperature and what is therapeutic? I think every temperature that leads to a clinical effect should be considered therapeutic. The normal term limits should be 36 up to 37.7. And the mean temperature that we think is normal should be 30 63.8 degrees. And if we're measuring body temperature it's not easy. We should always be aware that there are differences on different sites where we measure temperature and that there are different temperatures within the organs of interest. Thank you very much. Created by
