Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [150]-158).

Recent studies of heterothermy in free-ranging mammals have revealed that solar radiation is an important variable influencing torpor patterns. The interaction between solar radiation (SR) and arousal costs can be thought of as a continuum from passive increases in body temperature (Tb) (rewarming at a slower rate but energetically less costly), to supplementation of endogenous heat production (rewarming more rapidly but with costs similar to that in the absence of solar radiation). To better understand the importance of solar radiation I experimentally manipulated its availability for E. myurus rewarming from torpor under natural conditions of air temperature and photoperiod. Tb was recorded for E. myurus housed in deep shade (20 % SR), partial shade (40% SR) or full sun (100% SR), and torpor frequency, rewarming rates, minimum body temperature, torpor bout duration and heterothermy index compared among treatments. Animals in unshaded cages rewarmed more rapidly than individuals in partially shaded cages. Torpor bouts were less frequent, but overall levels of heterothermy were higher in E. myurus receiving natural solar radiation compared to those in partially shaded treatments. This study, as far as I am aware, is the first demonstrating that solar heat gain, separated from the effects of an increase in ambient temperature (Ta), plays an important role in torpor arousal. Taken with the direct evidence for elephant shrews basking while rewarming, this demonstrates that animals in the unshaded treatment used solar radiation to supplement, rather than replace, endogenous metabolic thermogenesis. It is clear that E. myurus does not necessarily depend on solar radiation for rewarming, but will take advantage of this resource if available, primarily by reducing time taken to rewarm. / Dissertation (MSc)--University of Pretoria, 2014. / lk2014 / Zoology and Entomology / MSc / Unrestricted

Rewarming mildly hypothermic subjects with distal extremity rewarming has been associated with significantly greater rewarming rate compared to shivering-only as it increases heat flow to the core by opening up of arteriovenous anastomoses in the extremities. This study compared distal extremity rewarming with Fluidotherapy® or warm water, or shivering-only. Seven healthy individuals were cooled in 8°C water to either a core temperature of 35°C or a maximum of one hour. The subjects were then rewarmed with one of the three rewarming methods (distal extremity rewarming with 44°C water or 46°C Fluidotherapy® or shivering-only) on three different occasions. There was no significant difference in the afterdrop length and duration between the three conditions. Fluidotherapy® provided rewarming rates similar to the shivering-only condition. Warm water rewarming provided higher heat donation to distal extremities and lead to a threefold higher rewarming rate compared to the other two treatments.

Rewarming mildly hypothermic subjects with distal extremity rewarming has been associated with significantly greater rewarming rate compared to shivering-only as it increases heat flow to the core by opening up of arteriovenous anastomoses in the extremities. This study compared distal extremity rewarming with Fluidotherapy® or warm water, or shivering-only. Seven healthy individuals were cooled in 8°C water to either a core temperature of 35°C or a maximum of one hour. The subjects were then rewarmed with one of the three rewarming methods (distal extremity rewarming with 44°C water or 46°C Fluidotherapy® or shivering-only) on three different occasions. There was no significant difference in the afterdrop length and duration between the three conditions. Fluidotherapy® provided rewarming rates similar to the shivering-only condition. Warm water rewarming provided higher heat donation to distal extremities and lead to a threefold higher rewarming rate compared to the other two treatments.

Bakgrund: Hypotermi, låg kroppstemperatur, i samband med operation är ett vanligt förekommande problem. För patienten medför hypotermi ett flertal fysiologiska konsekvenser, men kan även bidra till ett försämrat välbefinnande. För att förebygga hypotermi i samband med operation kan passiva och aktiva uppvärmningsmetoder vidtas. Syfte: Syftet med litteraturstudien var att undersöka vilka aktiva och passiva filtar som förebyggde iatrogen hypotermi och medföljande shivering. Metod: Studien gjordes som en litteraturstudie efter sökningar i databaserna PubMed och Cinahl.  Elva randomiserade kontrollerade studier och en kvasiexperimentell studie inkluderades. Resultat: Forced air warming, FAW, var mer effektiv i att öka kärntemperaturen och bevara normotermi postoperativt. FAW var också den mest effektiva uppvärmningsmetod i att minska intensiteten av shivering. Litteraturstudien visar motstridiga resultat om vilken uppvärmningsmetod som var mest effektiv i det intraoperativa skedet. Det fanns ingen signifikant skillnad mellan de olika uppvärmningsmetoderna i att minska incidensen av shivering. Slutsats: Att motverka iatrogen hypotermi är en väsentlig del för patientens välbefinnande. Forced air warming, FAW, var mer effektiv att förebygga hypotermi och minska intensiteten av shivering. Det fanns däremot ingen signifikant skillnad mellan de olika uppvärmningsmetoderna i det intraoperativa skedet eller i att minska incidensen av shivering. Dock är litteraturstudiens omfång begränsad och det krävs därför mer omfattande studier för att uppdatera kunskapsläget och ge patienten den mest lämpade vården. / Background: Hypothermia, low body temperature, is a common problem associated with surgery. For the patient, hypothermia involves a high frequency of physiological consequences, but may also contribute to a reduced wellbeing. In order to prevent iatrogen hypothermia - that is to say hypothermia associated with surgery, passive and active rewarming systems can be used. Aim: The aim of the litterature study was to investigate which rewarming system of active and passive blankets that prevent iatrogen hypothermia with supplied shivering. Method: The study was made as a literature study after a research on the databases PubMed and Cinahl. Eleven randomized controlled studies and a quasi-experimental study were included. Results: Forced air warming, FAW, was the most effective rewarming system in raising the core temperature and maintaining normothermia in postoperative patients. FAW was also the most effective rewarming method in decreasing the intensity of shivering. The literature study also showed contradictory results regarding which rewarming system that was most efficient during surgery. There were no significant differences between the rewarming systems in preventing the incidence of shivering. Conclusions: Preventing hypothermia is an essential part for the patient’s wellbeing. FAW were the rewarming systems that were most efficient in preventing hypothermia and decreasing the intensity of shivering. In contrast, there were no significant differences between the rewarming systems during surgery, nor regarding decreased incidence of shivering. However the range of the literature study is limited and therefore more extensive studies are required to update the state of knowledge to be able to give the most adequate care for the patient.

Abstract Since ancient times, warm or cold skin on the human body has been used as a parameter in evaluating health. Changes in body temperature are attributed to diseases or disorders. The assessment of body temperature is often performed to measure fever by detecting an elevated core temperature. With techniques such as infrared thermography, it is possible to perform a non-contact temperature measurement on a large surface area. The overall aim of this thesis was to contribute to a better understanding of the hand skin temperature variability in healthy persons and in persons experiencing whitening fingers (WF). The enclosed four papers discuss issues such as thermal variability response to cold stress test (CST) in repeated investigations; the specific rewarming pattern after CST; the difference between the hand’s palmar and dorsal temperatures; and evaluating skin temperatures and response to CST in participants with WF and healthy participants. All four papers used an experimental approach involving healthy males (I-III) and females (III) as well as individuals with (IV) and without WF (I-IV). Data were generated using dynamic infrared imaging before and after a CST. The radiometric images were analyzed using image analysis and statistics. The study showed that: (I) there is variability in hand skin temperature; (II) there are cold and warm hand skin temperature response patterns; (III) the skin temperatures on the palmar and dorsal sides of the hand are closely related; and (IV) a baseline hand skin temperature measurement can distinguish between whitening fingers and controls. The conclusion of this thesis is that it is necessary to engage in thorough planning before an investigation in order to choose the most adequate method for evaluating peripheral skin temperature response depending on the question asked.

Background: (Papers I and II) The objectives were to first determine incidence and contributing factors to cold-related injuries in northern Sweden, both those that led to hospitalization and those that led to fatality.  (Papers III and IV) A further aim was to assess post-cooling hand-rewarming responses and effects of training in a cold environment, both on fingertip rewarming and on function of the autonomic nervous system, to evaluate if there was adaptation related to prolonged occupational cold exposure. Methods:  In a retrospective analysis, cases of accidental cold-related injury with hospital admission in northern Sweden during 2000-2007 were analyzed (Paper I).  Cases of fatal hypothermia in the same region during 1992-2008 were analyzed (Paper II).  A cohort of volunteers was studied before and after many months of occupational cold exposure. Subject hand rewarming response was measured after a cold hand immersion provocation and categorized as slow, moderate or normal in rewarming speed.  This cold provocation and rewarming assessment was performed before and after their winter training.  (Paper III).  Heart rate variability (HRV) was analyzed from the same cold provocation/recovery sequences (Paper IV). Results:  (Paper I) For the 379 cases of hospitalization for cold-related injury, annual incidences for hypothermia, frostbite, and drowning were 3.4/100,000, 1.5/100,000, and 1.0/100,000 inhabitants, respectively.  Male gender was more frequent for all categories.  Annual frequencies for hypothermia hospitalizations increased during the study period.  Hypothermia degree and distribution of cases were 20 % mild (between 32 and 35ºC), 40% moderate (31.9 to 28ºC), and 24% severe (< 28ºC), while 12% had temperatures over 35.0ºC.  (Paper II) The 207 cases of fatal hypothermia showed an annual incidence of 1.35 per 100,000 inhabitants, 72% in rural areas, 93% outdoors, 40% found within 100 meters of a building.  Paradoxical undressing was documented in 30%.  Ethanol was detected in femoral vein blood in 43%. Contributing co-morbidity was common including heart disease, previous stroke, dementia, psychiatric disease, alcoholism, and recent trauma.  (Paper III) Post-training, baseline fingertip temperatures and cold recovery variables in terms of final rewarming fingertip temperature and vasodilation time increased significantly in moderate and slow rewarmers.  Cold-related injury (frostbite) during winter training occured disproportionately more often in slow rewarmers (4 of the 5 injuries).  (Paper IV) At ‘pre- winter-training’, normal rewarmers had higher power for low frequency and high frequency heart rate variability.  After cold acclimatization (post-training), normal rewarmers showed lower resting power values for the low frequency and high frequency heart rate variability components.  Conclusions: Hypothermia and cold injury continues to cause injury and hospitalization in the northern region of Sweden.  Assessment and management is not standardized across hospitals.  With the identification of groups at high risk for fatal hypothermia, it should be possible to reduce the incidence, particularly for highest risk subjects; rural, living alone, alcohol-imbibing, and psychiatric diagnosis-carrying citizens.  Long-term cold-weather training may affect hand rewarming patters after a cold provocation, and a warmer baseline hand temperature with faster rewarming after a cold provocation may be associated with less general risk for frostbite.  Heart rate variability results support the conclusion that cold adaptation in the autonomic nervous system occurred in both groups, though the biological significance of this is not yet clear.

Hypotermi, en sänkning av kroppens kärntemperatur under 36°C, är en oönskad men vanlig komplikation under den perioperativa perioden. Det är förenat med en rad negativa konsekvenser som kan orsaka lidande för patienter och innebära ökade vårdkostnader. Svårigheterna med att på ett enkelt och effektivt sätt förhindra hypotermi utgör ett hinder i vården och nya produkter utvecklas därför kontinuerligt. En viktig del i anestesisjuksköterskans arbete är att bevara patientens kroppstemperatur så nära det normala som möjligt. Syftet med föreliggande litteraturstudie var att beskriva olika metoder som är lämpliga för anestesisjuksköterskan att använda för att förhindra hypotermi hos vuxna i det perioperativa förloppet. I de 18 resultatartiklarna testades olika metoder för att bibehålla normal kroppstemperatur: täcka patienten, höjd salstemperatur, värmning med varmluft, elektrisk värmning, värmning av infusionsvätskor, värmning med cirkulerande varmvatten och strålningsvärme. Flera metoder visades effektiva men resultaten var inte entydiga. Inget system visades värma bättre än varmluft. Ytterligare forskning krävs för att fastställa nytta och säkerhet för de övriga aktiva värmesystemen men vissa kan komma att utgöra ett komplement till nuvarande strategier. / Hypothermia, a reduction of the body core temperature below 36°C, is an undesirable but common complication in the perioperative period. It is associated to a series adverse events that can cause discomfort to patients and result in increased health care costs. The difficulties involve a simple and effective way to prevent hypothermia and is an obstacle in the care and new products will develop over time. An important part of nurse anesthetists work is to maintain the patient´s body temperature as close to normal as possible. The aim of the literature study was to describe different methods that is appropriate for the nurse anesthetist to use to prevent hypothermia in adults in the perioperative process. In the results of the 18 articles different forms of methods were tested in order to maintain normal body temperature: cover the patient, raised room temperature, forced air warming, electric heating, fluid warming, warming with circulating hot water and radiant warming. Several methods were shown to be effective but the results were not conclusive. No system was demonstrated to be better than forced air warming. Further research is required to confirm the benefit and safety of the other active warming systems, but some may be in addition to current strategies.

Dissertation (Ph.D.)--University of South Florida, 2007. / Title from PDF of title page. Document formatted into pages; contains 107 pages. Includes vita. Includes bibliographical references.

Thesis--University of Oklahoma. / Includes bibliographical references (leaves 65-69).