Continuous Core Temperature Monitoring Research Articles

Preventing perioperative hypothermia in children through implementation of customised guidelines.

Perioperative hypothermia (PH) is common in children and associated with adverse clinical outcomes. Guidelines to prevent PH are mainly developed for adults and differ among institutions. We aimed to evaluate the effectiveness of customised guidelines in reducing PH in our paediatric population and the impact of cost considerations on physician practice. Patients aged ≤16 years undergoing general anaesthesia in our tertiary paediatric hospital were prospectively recruited in this cohort study. Patient demographics, surgical procedures, anaesthesia details and temperature control measures were recorded. Data collection occurred over four phases: Phases 1 and 2 comprised standard management, while Phases 3 and 4 occurred following guidelines implementation. Sensors for continuous core temperature monitoring were provided free to patients during Phases 1 and 3, but were charged during Phases 2 and 4. The main outcome was occurrence of PH, defined as core temperature <36°C at any point from induction of anaesthesia to discharge from the postanaesthetic care unit. The impact of guidelines implementation and cost considerations influencing physician practice on PH outcomes was also analysed. Data from 3917 patients was analysed (1766 in Phase 1, 679 in Phase 2, 706 in Phase 3 and 766 in Phase 4). Guidelines implementation decreased PH incidence from 11.0% to 6.79% (odds ratio [OR] 0.63, 95% confidence interval [CI] 0.50-0.80, P = 0.0002). Free sensors increased the odds of detecting PH (OR 1.48, 95% CI 1.17-1.88, P = 0.001). With guidelines implementation, there was greater reduction in PH with free sensors (OR 0.64, 95% CI 0.47-0.88, P = 0.0055) compared to chargeable sensors (OR 0.75, 95% CI 0.50-1.11, P = 0.1471). Customised guidelines facilitated a sustained reduction of hypothermia in our paediatric surgical patients, although its impact was reduced by cost considerations.

Continuous timely monitoring of core temperature with two wearable devices in pediatric patients undergoing chemotherapy for cancer – a comparison study

PurposePediatric patients with cancer often develop chemotherapy-induced fever in neutropenia (FN), requiring emergency broad-spectrum antibiotics. Continuous temperature monitoring can lead to earlier FN detection and therapy with improved outcomes. We aimed to compare the feasibility of continuous core temperature monitoring with timely data availability between two wearable devices (WDs) in pediatric oncology patients undergoing chemotherapy.MethodsIn this prospective observational two-center study, 20 patients (median age: 8 years) undergoing chemotherapy simultaneously wore two WDs (CORE®, Everion®) for 14 days. The predefined goal was core temperature recorded in sufficient quality and available within ≤ 30 min during ≥ 18/24 h for ≥ 7/14 days in more than 15 patients.ResultsMore patients reached the goal with CORE® (n = 13) versus Everion® (n = 3) (difference, 50% p < 0.001). After correcting for the transmission bottleneck caused by two WDs transmitting via one gateway, these numbers increased (n = 15 versus n = 14; difference, 5%; p = 0.69). CORE® measurements corresponded better to ear temperatures (n = 528; mean bias, − 0.07 °C; mean absolute difference, 0.35 °C) than Everion® measurements (n = 532; − 1.06 °C; 1.10 °C). Acceptance rates for the WDs were 95% for CORE® and 89% for Everion®.ConclusionThe CORE® fulfilled the predefined feasibility criterion (15 of 20 patients) after correction for transmission bottleneck, and the Everion® nearly fulfilled it. Continuous core temperature recording of good quality and with timely data availability was feasible from preschool to adolescent patients undergoing chemotherapy for cancer. These results encourage the design of randomized controlled trials on continuously monitored core temperature in pediatric patients.Trial registration.ClinicalTrials.gov (NCT04914702) on June 7, 2021.

Heat Health Management in a Quarantine and Isolation Facility in the Tropics.

The Howard Springs Quarantine Facility (HSQF) is located in tropical Northern Australia and has 875 blocks of four rooms (3,500 rooms in total) spread over 67 hectares. The HSQF requires a large outdoor workforce walking outdoor pathways to provide individual care in the ambient climate. The personal protective equipment (PPE) required for the safety of quarantine workers varies between workgroups and limits body heat dissipation that anecdotally contributes to excessive sweating, which combined with heat stress symptoms of fatigue, headache, and irritability, likely increases the risk of workplace injuries including infection control breaches. The purpose of this study was the description of qualitative and quantitative assessment for HSQF workers exposed to tropical environmental conditions and provision of evidenced-based strategies to mitigate the risk of heat stress in an outdoor quarantine and isolation workforce. The study comprised two components - a cross-sectional physiological monitoring study of 18 workers (eight males/ten females; means: 41.4 years; 1.69m; 80.6kg) during a single shift in November 2020 and a subjective heat health survey completed by participants on a minimum of four occasions across the wet season/summer period from November 2020 through February 2021. The physiological monitoring included continuous core temperature monitoring and assessment of fluid balance. The mean apparent temperature across first-half and second-half of the shift was 34.7°C (SD = 0.8) and 35.6°C (SD = 1.9), respectively. Across the work shift (mean duration 10.1 hours), the mean core temperature of participants was 37.3°C (SD = 0.2) with a range of 37.0°C - 37.7°C. The mean maximal core temperature of participants was 37.7°C (SD = 0.3). In the survey, for the workforce in full PPE, 57% reported feeling moderately, severely, or unbearably hot compared to 49% of those in non-contact PPE, and the level of fatigue was reported as moderate to severe in just over 25% of the workforce in both groups. Heat stress is a significant risk in outdoor workers in the tropics and is amplified in the coronavirus disease 2019 (COVID-19) frontline workforce required to wear PPE in outdoor settings. A heat health program aimed at mitigating risk, including workplace education, limiting exposure times, encouraging hydration, buddy system, active cooling, and monitoring, is recommended to limit PPE breaches and other workplace injuries in this workforce.

ERC-ESICM guidelines on temperature control after cardiac arrest in adults

The aim of these guidelines is to provide evidence‑based guidance for temperature control in adults who are comatose after resuscitation from either in-hospital or out-of-hospital cardiac arrest, regardless of the underlying cardiac rhythm. These guidelines replace the recommendations on temperature management after cardiac arrest included in the 2021 post-resuscitation care guidelines co-issued by the European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM).The guideline panel included thirteen international clinical experts who authored the 2021 ERC-ESICM guidelines and two methodologists who participated in the evidence review completed on behalf of the International Liaison Committee on Resuscitation (ILCOR) of whom ERC is a member society. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations. The panel provided suggestions on guideline implementation and identified priorities for future research.The certainty of evidence ranged from moderate to low. In patients who remain comatose after cardiac arrest, we recommend continuous monitoring of core temperature and actively preventing fever (defined as a temperature > 37.7 °C) for at least 72 hours. There was insufficient evidence to recommend for or against temperature control at 32–36 °C or early cooling after cardiac arrest. We recommend not actively rewarming comatose patients with mild hypothermia after return of spontaneous circulation (ROSC) to achieve normothermia. We recommend not using prehospital cooling with rapid infusion of large volumes of cold intravenous fluids immediately after ROSC.

ERC-ESICM guidelines on temperature control after cardiac arrest in adults.

The aim of these guidelines is to provide evidence‑based guidance for temperature control in adults who are comatose after resuscitation from either in-hospital or out-of-hospital cardiac arrest, regardless of the underlying cardiac rhythm. These guidelines replace the recommendations on temperature management after cardiac arrest included in the 2021 post-resuscitation care guidelines co-issued by the European Resuscitation Council (ERC) and the European Society of Intensive Care Medicine (ESICM). The guideline panel included thirteen international clinical experts who authored the 2021 ERC-ESICM guidelines and two methodologists who participated in the evidence review completed on behalf of the International Liaison Committee on Resuscitation (ILCOR) of whom ERC is a member society. We followed the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach to assess the certainty of evidence and grade recommendations. The panel provided suggestions on guideline implementation and identified priorities for future research. The certainty of evidence ranged from moderate to low. In patients who remain comatose after cardiac arrest, we recommend continuous monitoring of core temperature and actively preventing fever (defined as a temperature > 37.7°C) for at least 72h. There was insufficient evidence to recommend for or against temperature control at 32-36°C or early cooling after cardiac arrest. We recommend not actively rewarming comatose patients with mild hypothermia after return of spontaneous circulation (ROSC) to achieve normothermia. We recommend not using prehospital cooling with rapid infusion of large volumes of cold intravenous fluids immediately after ROSC.

Forced-air warming and continuous core temperature monitoring with zero-heat-flux thermometry during cesarean section: a retrospective observational cohort study

BackgroundOver 30% of parturients undergoing spinal anesthesia for cesarean section become intraoperatively hypothermic. This study assessed the magnitude of hypothermic insult in parturients and newborns using continuous, high-resolution thermometry and evaluated the efficiency of intraoperative forced-air warming for prevention of hypothermia. MethodsOne hundred and eleven parturients admitted for elective or emergency cesarean section under spinal anesthesia with newborn bonding over a 5-month period were included in this retrospective observational cohort study. Patients were divided into two groups: the passive insulation group, who received no active warming, and the active warming group, who received convective warming through an underbody blanket. Core body temperature was continuously monitored by zero-heat-flux thermometry and automatically recorded by data-loggers. The primary outcome was the incidence of hypothermia in the operating and recovery room. Neonatal outcomes were also analyzed. ResultsThe patients in the passive insulation group had significantly lower temperatures in the operating room compared to the actively warmed group (36.4°C vs. 36.6°C, p = 0.005), including temperature at skin closure (36.5°C vs. 36.7°C, p = 0.017). The temperature of the newborns after discharge from the postanesthetic care unit was lower in the passive insulation group (36.7°C vs. 37.0°C, p = 0.002); thirteen (15%) of the newborns were hypothermic, compared to three (4%) in the active warming group (p < 0.01). ConclusionForced-air warming decreases perioperative hypothermia in parturients undergoing cesarean section but does not entirely prevent hypothermia in newborns while bonding. Therefore, it can be effectively used for cesarean section, but special attention should be given to neonates.

Measured Versus Heart Rate-Derived Core Temperature During Outdoor Work In The Southeastern United States

Climate change is increasing the number of hot days to which outdoor workers are exposed, thereby increasing their risk of heat illness. Currently, continuous monitoring of core temperature (Tc) is expensive, invasive, and impractical. The BioModule is a non-invasive physiological monitor that uses heart rate to provide an estimation of Tc, but its accuracy is unknown. PURPOSE: To test the association between measured gastrointestinal temperature (TGI) and estimated core temperature (Tc-est) from the BioModule device during outdoor work in a hot environment. METHODS: Twenty groundskeepers (18 men; mean±SD age = 38±8 y, body mass index = 31.5±7.5 kg/m2) swallowed an ingestible temperature sensor and strapped on a BioModule before work. TGI was collected every 15 minutes during the workday; Tc-est was determined by a 1-min average from the same time of day. Data collection occurred in Alabama during July and August (31.4±3.1 °C WBGT). Relationship between TGI and Tc-est was quantified using the repeated measures correlation coefficient (rrm). Agreement (bias±1.96 SD) between TGI and Tc-est was evaluated using the Bland-Altman method for repeated observations. RESULTS: There was a moderate, positive relationship between TGI and Tc-est (rrm = 0.56, p < 0.001). Agreement analysis indicated that Tc-est overestimated TGI (0.28±0.58 °C). The error between Tc-est and TGI was larger at lower temperatures, as indicated by a strong negative trend (Pearson’s r = −0.73). CONCLUSION: The BioModule provides an estimation of Tc that may be helpful as a guide during outdoor work in hot environments but should not be used for safety considerations or measurement of Tc . Funded by the Deep South Center for Occupational Safety and Health, a National Institute for Occupational Safety and Health Education and Research Center.

Prevention of Hypothermia During Caesarean Section: Continuous Core Temperature Monitoring With Zero-heat-flux

Prevention of Hypothermia During Caesarean Section: Continuous Core Temperature Monitoring With Zero-heat-flux

Intra-operative cutaneous temperature monitoring with zero-heat-flux technique (3M SpotOn) in comparison with oesophageal and arterial temperature

Continuous monitoring of core temperature is essential during major surgery as a way of improving patient safety. Oesophageal probes or specific arterial catheters are invasive methods used in this setting. A new noninvasive device based on zero-heat-flux (ZHF) technique (SpotOn) seems promising but has been poorly investigated during rapid core temperature changes (RCTC). To assess the accuracy of a SpotOn sensor vs. an oesophageal probe or specific arterial catheter during a slow change in core temperature of less than 1 °C within 30 min and RCTC ≥ 1 °C within 30 min. Prospective observational study. Operating rooms at the University Hospital of Poitiers, France. Fifty patients scheduled for major abdominal surgery under general anaesthesia were enrolled from June 2015 to March 2016. Data from 49 patients were finally analysed. Among these, 15 patients were treated with hyperthermic intraperitoneal chemotherapy. Each patient had a ZHF sensor placed on the skin surface of the forehead (TempZHF) and an oesophageal probe (TempEso) used as a reference method. Twenty-two patients also had a thermodilution arterial catheter (TempArt) placed in the axillary artery. Core temperature was continuously recorded from the three devices after induction of anaesthesia. Comparison of temperature measurements between methods was made using the Bland and Altman method during two separate periods according to the speed of core temperature changes. Compared with TempEso, bias and limits of agreement for TempZHF were 0.1 ± 0.5 °C during slow core temperature changes periods and 0.6 ± 1.8 °C during RCTC periods (P = 0.0002). Compared with TempArt, these values were -0.1 ± 0.4 and 0.5 ± 1.7 °C, respectively (P = 0.0039). The ZHF sensor was well tolerated. A SpotOn sensor using the ZHF method seems reliable for core temperature monitoring during abdominal surgery when variations in core temperature are slow rather than rapid. ClinicalTrials.gov identifier: NCT02869828.

When do trauma patients lose temperature? – a prospective observational study

The prevalence of hypothermia in trauma patients is high and rapid recognition is important to prevent further heat loss. Hypothermia is associated with poor patient outcomes and is an independent predictor of increased mortality. The aim of this study was to analyze the changes in core body temperature of trauma patients during different treatment phases in the pre-hospital and early in-hospital settings. A prospective observational cohort study in severely injured patients. Continuous core temperature monitoring using an epitympanic sensor in the auditory canal was initiated at the scene of injury and continued for 3 h. The degree of patient insulation was photo-documented throughout, and graded on a binary scale. The outcome variable was temperature change in each treatment phase. Twenty-two patients were included with a median injury severity score (ISS) of 21 (IQR 14-29). Most patients (N = 16, 73%) were already hypothermic (< 36°C) on scene at their first measurement. Twenty patients (91%) became colder at the scene of injury; on average, the decline was -1.7°C/h. Full clothing reduced this value to -1.1°C/h. Temperature remained essentially stable during ambulance and emergency department phases. Trauma patients are at risk for hypothermia already at the scene of injury. Lay persons and professionals should focus on early prevention of heat loss. An active, individually tailored approach to counter hypothermia in trauma should begin immediately at the scene of injury and continue during transportation to hospital. Active rewarming during evacuation should be considered.

Rectal and Bladder Temperatures vs Forehead Core Temperatures Measured With SpotOn Monitoring System.

Methods and frequency of temperature monitoring in intensive care unit patients vary widely. The recently available SpotOn system uses zero-heat-flux technology and offers a noninvasive method for continuous monitoring of core temperature of critical care patients at risk for alterations in body temperature. To evaluate agreement between and precision of a zero-heat-flux thermometry system (SpotOn) and continuous rectal and urinary bladder thermometry during fever and defervescence in adult patients in intensive care units. Prospective comparison of SpotOn vs rectal and urinary bladder thermometry in eligible patients enrolled in a randomized clinical trial on the effect of acetaminophen on core body temperature and hemodynamic status. A total of 748 paired temperature measurements from 38 patients who had both SpotOn monitoring and either continuous rectal or continuous bladder thermometry were analyzed. Temperatures during the study were from 36.6°C to 39.9°C. The mean difference for SpotOn compared with bladder thermometry was -0.07°C (SD, 0.24°C; 95% limits of agreement, ± 0.47°C [-0.54°C, 0.40°C]). The mean difference for SpotOn compared with rectal thermometry was -0.24°C (SD, 0.29°C; 95% limits of agreement, ± 0.57°C [-0.81°C, 0.33°C]). Most differences in temperature between methods were within ± 0.5°C in both groups (96% bladder and 85% rectal). The SpotOn thermometry system has excellent agreement and good precision and is a potential alternative for noninvasive continuous monitoring of core temperature in critical care patients, especially when alternative methods are contraindicated or not available.

Clinical Pearls

Body temperature readings provide vital information for accurate diagnoses and required therapies. However, standard practices for measuring body temperature in intensive care units (ICUs) vary and often require invasive methods with limited accuracy in different types of patients.Schell-Chaple and colleagues evaluated a new, noninvasive monitoring system that is applied to the lateral forehead, called SpotOn. They compared temperatures taken with the SpotOn system with rectal and bladder temperatures in febrile adult patients. They found the following:The SpotOn method was accurate. Although the authors recommend further research to test for longer periods, they suggest this noninvasive system be considered for continuous monitoring of core temperature in ICU patients.See Article, pp 43–50Family-centered care (FCC) enables and empowers families through improved communication and involvement in their child’s care. However, recent changes in FCC have incorporated a customer service emphasis that can be challenging for staff.The research team interviewed nurses to explore their perceptions of the benefits and challenges in providing FCC. They found thatWhile acknowledging the benefits of FCC, Coats and colleagues recommend that (1) support systems be available for nurses dealing alone with families, (2) new nurses have a longer mentorship to become comfortable with providing care independently in private rooms, and (3) nurses be involved in the implementation of FCC practices.See Article, pp 52–58Patients who require mechanical ventilation often receive sedative therapy to reduce anxiety and optimize comfort and safety. Although various sedation protocols have been successfully used to facilitate quick weaning from mechanical ventilation, there is no standardized practice despite guidelines from organizations such as the Society of Critical Care Medicine.Borkowska and colleagues surveyed more than 300 nurses from an adult intensive care unit and asked them to evaluate their daily sedation practices. They found the following:Nurses’ perceptions, attitudes, and knowledge are vital to the success of any sedation practice. Organizational and multidisciplinary collaboration is needed to improve sedation practices at regional, national, and international levels.See Article, pp 32–42The influenza A(H1N1) pandemic of 2009 to 2010 caused thousands of deaths across the world and left survivors with significant functional limitations and morbidities. Many patients had acute renal failure requiring continuous renal replacement therapy (CRRT); however, the long-term consequences are unknown.Napolitano and colleagues examined the long-term recovery of adult patients in a surgical intensive care unit (ICU) with acute respiratory distress syndrome (ARDS) who tested positive for H1N1. They found the following:This study is the largest to date to report renal outcomes in ARDS-H1N1 patients. The findings provide clinicians with valuable information needed to optimize future resource use.See Article, pp 67–73

Malignant hyperthermia deaths related to inadequate temperature monitoring, 2007-2012: a report from the North American malignant hyperthermia registry of the malignant hyperthermia association of the United States.

AMRA (adverse metabolic or muscular reaction to anesthesia) reports submitted to The North American Malignant Hyperthermia Registry of the Malignant Hyperthermia Association of the United States from 1987 to 2006 revealed a 2.7% cardiac arrest and a 1.4% death rate for 291 malignant hyperthermia (MH) events. We analyzed 6 years of recent data to update MH cardiac arrest and death rates, summarized characteristics associated with cardiac arrest and death, and documented differences between early and recent cohorts of patients in the MH Registry. We also tested whether the available data supported the hypothesis that risk of dying from an episode of MH is increased in patients with inadequate temperature monitoring. We included U.S. or Canadian reports of adverse events after administration of at least 1 anesthetic drug, received between January 1, 2007, and December 31, 2012, with an MH clinical grading scale rank of "very likely MH" or "almost certain MH." We excluded reports that, after review, were judged to be due to pathologic conditions other than MH. We analyzed patient demographics, family and patient anesthetic history, anesthetic management including temperature monitoring, initial dantrolene dose, use of cardiopulmonary resuscitation, MH complications, survival, and reported molecular genetic DNA analysis of RYR1 and CACNA1S. A one-sided Cochran-Armitage test for proportions evaluated associations between mode of monitoring and mortality. We used Miettinen and Nurminen's method for assessing the relative risk of dying according to monitoring method. We used the P value of the slope to evaluate the relationship between duration of anesthetic exposure before dantrolene administration and peak temperature. We calculated the relative risk of death in this cohort compared with our previous cohort by using the Miettinen and Nurminen method adjusted for 4 comparisons. Of 189 AMRA reports, 84 met our inclusion criteria. These included 7 (8.3%) cardiac arrests, no successful resuscitations, and 8 (9.5%) deaths. Of the 8 patients who died, 7 underwent elective surgeries considered low to intermediate risk. The average age of patients who died was 31.4 ± 16.9 years. Five were healthy preoperatively. Three of the 8 patients had unrevealed MH family history. Four of 8 anesthetics were performed in freestanding facilities. In those who died, 3 MH-causative RYR1 mutations and 3 RYR1 variants likely to have been pathogenic were found in the 6 patients in whom RYR1 was examined. Compared to core temperature monitoring, the relative risk of dying with no temperature monitoring was 13.8 (lower limit 2.1). Compared to core temperature monitoring, the relative risk of dying with skin temperature monitoring was 9.7 (1.5). Temperature monitoring mode best distinguished patients who lived from those who died. End-tidal CO2 was the worst physiologic measure to distinguish patients who lived from those who died. Longer anesthetic exposures before dantrolene were associated with higher peak temperatures (P = 0.00056). Compared with the early cohort, the recent cohort had a higher percentage of MH deaths (4/291 vs 8/84; relative risk = 6.9; 95% confidence interval, 1.7-28; P = 0.0043 after adjustment for 4 comparisons). Despite a thorough understanding of the management of MH and the availability of a specific antidote, the risk of dying from an MH episode remains unacceptably high. To increase the chance of successful MH treatment, the American Society of Anesthesiologists and Malignant Hyperthermia Association of the U.S. monitoring standards should be altered to require core temperature monitoring for all general anesthetics lasting 30 minutes or longer.

Brain Temperature: Physiology and Pathophysiology after Brain Injury

The regulation of brain temperature is largely dependent on the metabolic activity of brain tissue and remains complex. In intensive care clinical practice, the continuous monitoring of core temperature in patients with brain injury is currently highly recommended. After major brain injury, brain temperature is often higher than and can vary independently of systemic temperature. It has been shown that in cases of brain injury, the brain is extremely sensitive and vulnerable to small variations in temperature. The prevention of fever has been proposed as a therapeutic tool to limit neuronal injury. However, temperature control after traumatic brain injury, subarachnoid hemorrhage, or stroke can be challenging. Furthermore, fever may also have beneficial effects, especially in cases involving infections. While therapeutic hypothermia has shown beneficial effects in animal models, its use is still debated in clinical practice. This paper aims to describe the physiology and pathophysiology of changes in brain temperature after brain injury and to study the effects of controlling brain temperature after such injury.

Do alterations in temperature regulation contribute to protein‐energy malnutrition‐induced increase in reactive gliosis after global ischemia?

Protein‐energy malnutrition (PEM) impairs functional outcome after global ischemia, and this is associated with an increase in reactive gliosis. Since temperature is a key determinant of brain damage following an ischemic insult, the objective of this study was to determine if PEM modifies post‐ischemic temperature regulation. Bio‐electrical sensor transmitters were implanted into the peritoneal cavity of male, Sprague‐Dawley rats (31d) for continuous monitoring of core temperature. Rats were randomized for 7d to modified AIN‐93G control diet (CON; 18% protein) or PEM (2% protein). Animals were exposed to global ischemia (I) induced by 10 min bilateral carotid artery occlusion and hypotension (38 ± 0.2 mm Hg) or sham surgery (S) with tympanic temperature maintained at 37.4 ± 0.2°C. Physiological values were as follows: pH 7.29–7.41, pO2 119–144 mm Hg, pCO2 34–51 mm Hg, blood glucose 3.8–6.7 mmol/L. Preliminary results indicate mean (± SEM) core and daily temperature fluctuation from 5d of postsurgical monitoring as follows: CON‐S: 37.4 ± 0.04°C, 2.0 ± 0.1°C (n=3); PEM‐S: 37.4 ± 0.1°C, 2.6 ± 0.1°C (n=3); CON‐I: 37.7 ± 0.1°C, 1.9 ± 0.2 °C (n=3); PEM‐I: 37.5 ± 0.2°C, 2.3 ± 0.3°C (n=2). These data suggest that although PEM does not cause marked hypothermia or hyperthermia during the postsurgical period, it reduces thermoregulatory function in both sham and ischemic animals. Funded by the Heart and Stroke Foundation of SK.

The Usefulness of an Earphone-Type Infrared Tympanic Thermometer for Intraoperative Core Temperature Monitoring

In this study we sought to determine the usefulness of a novel earphone-type infrared tympanic thermometer (IRT) for core temperature monitoring during surgery. Two groups of patients were studied under different surgical conditions. The first group consisted of 18 adult patients (ASA I or II) who had been scheduled for elective surgery under general anesthesia. Before induction of general anesthesia, an earphone-type IRT was inserted into either the left or right ear canal. Tympanic temperature was monitored and recorded along with both rectal and esophageal temperatures during anesthesia. The second group consisted of eight adult patients (ASA II or III) who had been scheduled for cardiac surgery with cardiopulmonary bypass. Similar to the first group, tympanic temperature was measured by the earphone-type IRT and recorded along with the rectal and esophageal temperatures during cooling and rewarming phases of cardiopulmonary bypass. Study 1-The average temperature (+/-2 sd) measured with the IRT was +0.08 degrees C (+/-0.34 degrees C) above the esophageal temperature, and that with the rectal temperature was +0.11 degrees C (+/-0.55 degrees C) above the esophageal temperature. Study 2-The average temperature (+/-2 sd) measured with the IRT was +0.72 degrees C (+/-2.2 degrees C) above the esophageal temperature during cooling and warming phases during cardiac surgery with cardiopulmonary bypass. The earphone-type IRT might be used in a clinical setting for reliable and continuous core temperature monitoring during an operation.

A nonsurgical method allowing continuous core temperature monitoring in mares for extended periods, including during endurance exercise

Body temperature can be a useful measure of how well the horse responds to thermal challenges of exercise and environment. Currently there is little information available about how body temperature changes throughout an endurance ride, and no nonsurgical methods to evaluate internal temperature of exercising horses during prolonged periods and during long distances. To develop and test a nonsurgical method, using temperature loggers, of continuously recording internal temperature during exercise and over an extended period. Loggers were inserted transcervically into the uterus of mares to measure internal temperature. A total of 9 mares were implanted for periods of 3 days to 6 weeks. The internal temperature was recorded while horses underwent their normal training and competition. Loggers were validated against rectal temperature over a range of internal temperatures while mares were alternatively exercised and rested. The technique proved to be straightforward and accurate. There were no ill effects observed and all mares retained the logger in utero until removal manually, except for one mare, which expelled the logger when she came into oestrus. The intrauterine and deep rectal temperatures were highly correlated and increased during exercise and decreased with aggressive cooling after exercise. The technique is a useful and accurate nonsurgical method for prolonged monitoring of internal temperature in mares, including those animals in athletic competition. This method allows more intensive studies of core temperature during prolonged exercise in competition and under different environmental conditions. It also enables comparison to be made of different methods of cooling of horses post exercise.

The safety and effectiveness of a modified convection heating system for children during anesthesia

Convection heating shows most promise in maintaining children's core temperatures under anesthesia. We have previously shown that a modified convection heating technique worked in a mannequin model and sought to establish its safety and effectiveness in a clinical study. Children were recruited who were having elective surgery under general anesthesia lasting >90 min. The children were anesthetized and maintained in a room temperature of 21 degrees C. Warming was performed by a 'Bair Hugger' attached to a heat dissipation box, producing turbulent air from multiple outlet holes on its face. A plastic sheet covered the child, was attached to the top of the box, tucked into the sides of the bed and left open at the head end. Temperatures at various sites (air, skin, and core) were continuously monitored using thermistors connected to a datalogger and laptop. Analysis was performed using Excel. The study comprised 40 children ranging in age from 2 days to 12.5 years and weigh 2.5-73 kg. Operations were 'peripheral' (e.g. urethroplasty) lasting 90 min to major laparotomy lasting 590 min. Body surface area uncovered was 5-25%. Skin temperatures rose to a maximum of c. 40 degrees C. Core temperatures rose after a 12-min lag by 0.01-0.04 degrees C x min(-1). In children who became hyperthermic, cooling was readily achieved by turning the heating off and leaving the fan running. The technique is safe and effective for children throughout the pediatric range. The practice of increasing room temperature above 21 degrees C for elective cases should be abandoned. Continuous monitoring of core temperature is necessary to prevent hyperthermia.

Freeze lesion-induced focal cortical dysplasia predisposes to atypical hyperthermic seizures in the immature rat.

To determine the effects of focal cortical dysplasia on the behavioral and electrographic features of hyperthermia-induced seizures (HSs) in rats. A right sensorimotor cortex freeze lesion was induced in postnatal day 1 (P1) rat pups, and HSs were provoked at P10 under continuous monitoring of core temperature; EEGs were recorded from the right amygdala during and after hyperthermia. Controls included both sham-operated at P1 and naïve rats. HSs began with jaw myoclonus, followed by hindlimb clonus and generalized convulsions (GCs), and terminated by a period of posthyperthermia depression. The threshold temperature and latency of jaw myoclonus were similar across the groups. However, both the threshold temperature and latency of GCs were significantly lower in lesioned pups than in controls (40.5 +/- 0.5 degrees C, n = 24, vs. 42.0 +/- 0.2 degrees C, n = 21; p < 0.001; 6.7 +/- 0.6 min, n = 20, vs. 8.4 +/- 0.6 min, n = 22; p < 0.05). In lesioned pups, the threshold and latencies for jaw myoclonus and hindlimb clonus were similar, whereas in controls, the progression from one to the other was marked by significant differences in both parameters. Posthyperthermia depression was longer in lesioned (13.3 +/- 1.2 min, n = 21) than in control (8.0 +/- 0.8 min, n = 20; p < 0.0001) pups. Ictal EEG activity was recorded during both behavioral seizures and posthyperthermia depression. An HS in rats with a localized freeze lesion results in lower threshold GC and prolonged ictal manifestations, thus supporting a pathophysiologic link between focal cortical dysplasia and atypical febrile seizures, conditions that have a high prevalence in children with mesial temporal lobe epilepsy.

Continuous core temperature monitoring of search and rescue divers during extreme conditions

Objectives. To study the feasibility of continuously monitoring core temperatures of search and rescue divers, to compare core temperature gradients occurring during warm and cold diving events, and to identify conditions under which divers are subjected to extreme temperatures. Methods. Between June 1994 and March 1995, emergency medical technicians (EMTs) from two midwestern dive teams volunteered to ingest an encapsulated temperature sensor developed for the National Aeronautics and Space Administration. The capsule monitored continuous core temperatures and transmitted the data to a recorder worn under the divers' dry suits. Results. Twenty male EMTs, mean age 34 years and mean body weight 184 pounds, were monitored during training. Nine dives were ice dives, with ice thickness averaging 9 inches, and mean ambient temperatures of 33°F. Eleven dives were warm-water dives; average water temperature was 70°F and mean ambient temperature was 74°F. The average time spent in the dry suit was 95 minutes, and the mean total bottom time was 15 minutes. The ice divers showed a mean increase in core temperature of 1.0°C, while the warm-water divers showed a mean increase of 1.2°C. Divers experiencing the most extreme fluctuations were those in the role of safety diver, regardless of the season. Divers reported more subjective discomfort during ice dives than during warm-water dives. Conclusions. Continuous monitoring of body temperature during the duration of dive operations is possible, but labor-intensive. Safety measures to protect divers from extreme core temperature fluctuations should focus on the safety diver as well as the active diver.