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Altitude, temperature, circadian rhythms and exercise
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Henning Wackerhage, Kenneth A. Dyar, Martin Schönfelder
Humans have evolved a regulatory system that maintains the temperature of our body within a narrow range. In relation to temperature, our body has two parts. First, our shell includes our skin and extremities, and here the temperature can vary considerably, for example when we have cold hands or feet. Second, our core comprises the vital inner organs and here the temperature is on average close to ≈37°C. Maintaining our core body temperature is important, as temperature has profound effects on the molecules of life. For example, the activity of enzymes increases with temperature before a too hot temperature causes enzymes and other proteins to denature. If we become too hot then we can suffer a heat stroke which is hyperthermia (core body temperature of >40°C) accompanied by systemic inflammation which can cause defects of several organs and eventually death (35). In contrast, when our body cools down, then enzymes are less active, membranes are more rigid and ion fluxes are reduced. Hypothermia is a medical syndrome when the core body temperature falls to below 35°C. When we are hypothermic, we start to shiver and become lethargic and this can progress further to confusion, coma and death.
Introduction
Published in Kevin L. Erskine, Erica J. Armstrong, Water-Related Death Investigation, 2021
With continued contact with cold water, deep tissue cooling (the third stage) signifies the onset of hypothermia. Immersion of bodies in cold water for prolonged periods puts one at particular risk for drowning due to the physiologic effects of hypothermia, and death can result from hypothermia alone.14,17,18 Hypothermia causes suppression of the body’s metabolism, blood flow, and brain function which translates to reduced O2 requirements and virtually all organ systems are ultimately affected. The normal core body temperature is approximately 37°C (98.6°F). Hypothermia occurs when the core body temperature falls below 35°C (95°F). Cold water has a conductivity 25 times that of air causing the body to cool four to five times faster in water than in air. This is in addition to body heat lost through respiration, urination, and sweating.14,17,18 Previous studies have found that prolonged immersion (upward of six hours or more) and cold water temperatures ranging from below 0°C to just below 20°C (or 32–68°F) are important risk factors for death due to hypothermia. Other studies have illuminated additional risk factors, including lower body fat, lack of clothing, exertional activity, intoxication, and the use of certain prescription medications that can accelerate the onset of hypothermia.14,17,18
Heat, cold and electrical trauma
Published in Jason Payne-James, Richard Jones, Simpson's Forensic Medicine, 2019
Jason Payne-James, Richard Jones
Hyperthermia, a condition where the core body temperature is greater than 40°C (100°F), occurs when heat is no longer effectively dissipated, leading to excessive heat retention. Its development may be associated with those who have taken prescribed drugs including some anti-psychotics and those who have taken illicit stimulants including cocaine and amphetamine and some novel psychoactive substances. These appear to elevate metabolic rate/heat production or reduce sweating. It may also occur in those with medical conditions (e.g., hyperthyroidism), or in those who are resisting restraint. It may occur in those exposed to high ambient temperatures (heat stroke) and has a high risk of mortality or morbidity, which can occur in the young and fit (exertional heat stroke) as well as the elderly and infirm (non-exertional heat stroke). Other examples may include children trapped in hot cars. Exertional heat illness is recognised within military training programmes. Autopsy findings in such cases are non-specific but can include diffuse petechial haemorrhages of serosal membranes and lung congestion as well as features in keeping with ‘shock’ and multiple organ failure in those who survive for a short period, if resuscitative measures are ineffective.
Application of HIPEC simulations for optimizing treatment delivery strategies
Published in International Journal of Hyperthermia, 2023
Daan R. Löke, H. Petra Kok, Roxan F. C. P. A Helderman, Bella Bokan, Nicolaas A. P. Franken, Arlene L. Oei, Jurriaan B. Tuynman, Pieter J. Tanis, Johannes Crezee
The chemotherapy and heat in the peritoneal tissues can be transferred to the systemic compartment by perfusion, and then partially redistributed. The systemic exposure to chemotherapy and the core body temperature were continuously monitored during the simulation. The change of core body temperature, the perfusate drug concentration, plasma drug concentration and the ratio of perfusate concentration to plasma concentration over time is shown in Figure 3(A–D). Core body temperature is visualized for the mild (yellow), moderate (orange) and severe (red) treatment strategies, demonstrating the effect of treatment strategy on the core body temperature. Table 4 (top) shows a comparison of the predicted systemic values and those reported in literature. Since the core body temperature is dependent on treatment characteristics, core body temperatures from the literature were compared to the case that matched the treatment characteristics in the respective study. Core body temperatures were in good agreement with literature values. A similar comparison was made for plasma concentrations of chemotherapeutic agents. Since studies use different doses, the maximum perfusate concentration to the maximum plasma concentration, Table 4). The values in the literature vary widely (
Enhanced intestinal permeability and intestinal co-morbidities in heat strain: A review and case for autodigestion
Published in Temperature, 2021
Anthony A. Fung, Andy Zhou, Jennifer K. Vanos, Geert W. Schmid-Schönbein
There is a direct association between the magnitude of hyperthermia as measured by core body temperature and the degree to which intestinal permeability increases. Pires et al. [44] show that intestinal hyperpermeability in humans begins to occur at core temperatures above 38.5°C and is almost certain to occur at core temperatures above 39°C. Furthermore, it has been found that increasing core temperature accounts for 63% of the variance in intestinal permeability [44]. Although intestinal permeability is often observed when the core temperature exceeds 39°C during exercise, it should be noted that well-conditioned individuals, such as athletes, commonly reach temperatures higher than 39°C while training and/or competing [71,72] yet the incidence of heat stroke is relatively low. Moreover, enhanced intestinal permeability does not always lead to heat illness, especially in light of the liver’s capacity to filter out many constituents from portal venous blood.
Demonstration of treatment planning software for hyperthermic intraperitoneal chemotherapy in a rat model
Published in International Journal of Hyperthermia, 2021
Daan R. Löke, Roxan F. C. P. A. Helderman, Hans M. Rodermond, Pieter J. Tanis, Geert J. Streekstra, Nicolaas A. P. Franken, Arlene L. Oei, Johannes Crezee, H. Petra Kok
A part of the heat transferred to the blood is lost to the environment, establishing the indirect heat loss from the peritoneal cavity. We take two ways into account in which rats can lose their body heat. First of all, there is significant heat loss to the exterior via the skin (Qs). We used a separate perfusion term to take this into account similar to Equation (3). The second way is via the rat tail (Qt), used for thermal regulation. At an ambient temperature of 22 °C, the perfusion for the tail vein is minimal. However, if the core temperature increases during HIPEC, the perfusion in the rat tail also starts to increase, resulting in significant heat loss through the tail. We take this into account by replacing the constant wb with a temperature-dependent mass perfusion term in Equation (3). This mass perfusion term is based on experimental data taken from [38]. These data were fitted linearly between 37 °C and 43 °C, yielding T (K). The rest of the heat carried away from the organs elevates the core body temperature. The contributions Qo, Qs, Qt and Qpw depend on the core temperature. To ensure realistic values, we monitor the core temperature throughout the simulation.