Initial Core Temperature Research Articles

Criteria for the interpretation of cocaine levels in human biological samples and their relation to the cause of death.

The determination that cocaine is directly responsible for the immediate cause of death should be considered only when there is a reasonably complete understanding of the circumstances or facts surrounding the death. Another, more obvious and immediate cause of death must be absent, or, at least cocaine must be shown to be a significant contributing factor in the chain of medical findings that lead directly to the immediate cause of death. Not all death investigation requires the sequential steps described in this paper, but these steps must be considered early on in the investigation whenever there is scene, investigational, medical or a historical basis to believe that cocaine is directly related to the cause of death. A relatively high profile death when cocaine is known to be involved, or a death involving unusual behavior on the part of the deceased with police involvement are examples where these considerations may well apply. Information needs to be obtained as soon as possible to have the highest chance of successfully documenting the toxicologic basis for the diagnosis. These facts would include, but would not necessarily be limited to, a scene investigation (whenever possible), a careful review of the investigative reports from all involved agencies, the initial core temperature of the body as well as that of the environment at the time of the collapse or death, the past medical history of the individual, and the results of a complete forensic autopsy and toxicologic studies. Knowledge of and an understanding of the current relevant forensic literature on this subject should be available to the reviewer prior to any interpretation of the significance of cocaine upon a specific death.

Thermal evolution of Earth: Models with time‐dependent layering of mantle convection which satisfy the Urey ratio constraint

We present a new set of Earth thermal history calculations in which the effect of increasing mantle layering with convection Rayleigh number is included in a parameterized mantle convection model. We demonstrate that the inclusion of this effect results in strong buffering of the upper mantle temperature and surface heat flow. Models of this type deliver the observed surface heat flow when geochemically constrained internal heating rates (Urey ratios) are assumed with reasonable initial core temperatures. The surface heat flow is also relatively unchanged for the last 3 Gyr of Earth history in models of this kind, in accord with geological inferences concerning ancient geotherms derived from the study of Archean continental materials. In contrast, models with constant degrees of layering spanning the range from whole mantle to fully layered convection are shown to require unreasonably high initial core temperatures in order to meet the surface heat flow constraint. All successful models require that the coupling of heat flow between reservoirs be smaller than would be expected if mantle viscosities are those inferred on the basis of postglacial rebound (PGR) observations. This may indicate that viscosity for convection is significantly greater than that for rebound and hence that mantle rheology is non‐Newtonian and that the PGR process is governed by transient rather than steady state creep.

Severe Accidental Hypothermia Treated in an ICU: Prognosis and Outcome

To assess the characteristics and outcomes of patients admitted to an ICU for severe accidental hypothermia, and to identify risk factors for mortality. All consecutive patients admitted to an ICU between January 1, 1979, and July 31, 1998, with a temperature of < or = 32 degrees C were retrospectively analyzed. Rewarming was always conducted passively with survival blankets and conventional covers. Prognostic factors were studied by means of univariate analysis (Mann-Whitney U and chi(2) tests) and multivariate analysis (logistic regression). Forty-seven patients were enrolled (mean +/- SD age, 61.7 +/- 16 years). Five patients had a cardiac arrest before ICU admission. Patient characteristics at ICU admission were as follows: temperature, 28.8 +/- 2.5 degrees C; systolic BP, 85 +/- 23 mm Hg; heart rate, 60 +/- 24 beats/min; Glasgow Coma Scale, 10.4 +/- 3.7; and simplified acute physiology score (SAPS) II, 50.9 +/- 27. Mechanical ventilation was necessary in 23 cases, and 22 patients in shock received vasoactive drugs. The mean length of stay in the ICU was 6.7 +/- 9 days. Eighteen patients (38%) died, but ventricular arrhythmia was never the cause. Univariate analysis identified several prognostic factors (p < 0.05): age (57 +/- 16 years vs 69 +/- 14 years), systolic arterial BP (93 +/- 20 mm Hg vs 71 +/- 21 mm Hg), blood bicarbonate level (23.5 +/- 5.2 mmol/L vs 16.6 +/- 6.2 mmol/L), SAPS II score (35.3 +/- 19.5 vs 72 +/- 21), mechanical ventilation (34% vs 81%), vasopressor agents (42% vs 82%), rewarming time (11.5 +/- 7.2 h vs 17.2 +/- 7 h), and discovery of the patient at home (2.3% vs 54.5%). The initial temperature did not influence vital outcome (28.9 +/- 2.6 degrees C vs 28.6 +/- 2.2 degrees C). Only the use of vasoactive drugs (odds ratio, 9; 95% confidence interval, 1.6 to 50.1) was identified as a prognostic factor in the multivariate analysis. Severe accidental hypothermia is a rare cause of ICU admission in an urban area. Its mortality remains high, but there is no overmortality according to the SAPS II-derived prediction of death. Shock, requiring treatment with vasoactive drugs, is an independent risk factor for mortality, while initial core temperature is not. It remains to be determined whether aggressive rather than passive rewarming procedures are better.

Effectiveness of Resistive Heating Compared With Passive Warming in Treating Hypothermia Associated With Minor Trauma: A Randomized Trial

To determine the occurrence of hypothermia in patients with minor trauma, to test the hypotheses that resistive heating during transport is effective treatment for hypothermia and that this treatment reduces patients' thermal discomfort, pain, and fear, and to evaluate the accuracy of oral temperatures obtained at the scene of injury. In December 1999 and January 2000, 100 patients with minor trauma were randomly assigned to passive warming or resistive heating. All patients were covered with a carbon-fiber resistive warming blanket and a wool blanket, but the warming blanket was activated only in those assigned to resistive heating. Core (tympanic membrane) and oral temperatures, heart rate, pain, fear, and overall satisfaction of patients were compared between the 2 groups on arrival at a hospital. Hypothermia was noted in 80 patients at the time of rescue. Mean initial core temperatures were 35.4 degrees C (95% confidence interval [CI], 35.2 degrees C - 35.6 degrees C) in the patients who received passive warming and 35.3 degrees C (95% CI, 35.1 degrees C - 35.5 degrees C) in those who received resistive heating. From the time of rescue until arrival at the hospital, mean core temperature decreased 0.4 degrees C/h (95% CI, 0.3 degrees C/h - 0.5 degrees C/h) with passive warming, whereas it increased 0.8 degrees C/h (95% CI, 0.7 degrees C/h - 0.9 degrees C/h) with resistive heating. Oral and tympanic membrane temperatures were similar. Mean heart rate decreased 23 beats/min in those assigned to resistive heating but remained unchanged in those assigned to passive warming. Patients in the resistive heating group felt warmer, had less pain and anxiety, and overall were more satisfied with their care. Oral temperatures are sufficiently accurate for field use. Hypothermia is common even in persons with minor trauma. Resistive heating during transport augments thermal comfort, increases core temperature, reduces pain and anxiety, and improves overall patient satisfaction.

Temperature Monitoring and Management During Neuraxial Anesthesia: An Observational Study

Temperature monitoring and thermal management are rare during spinal or epidural anesthesia because clinicians apparently restrict monitoring to patients with an expected risk of hypothermia. This implies that anesthesiologists can predict patient thermal status without monitoring core temperature. We therefore, tested the hypotheses that during neuraxial anesthesia: 1) amount of core hypothermia depends on the magnitude and duration of surgery; 2) temperature monitoring and thermal management are used selectively in patients at high risk of hypothermia; and 3) anesthesiologists can estimate patient thermal status. We evaluated thermal status on arrival in the recovery room along with intraoperative thermal management and monitoring in 120 patients. Anesthesiologists were asked if their patients were hypothermic (<36°C). There was no correlation between the magnitude or duration of surgery and initial postoperative core temperature in unwarmed patients. Temperature monitoring and thermal management were not used selectively in high-risk patients. Initial postoperative tympanic membrane temperatures were <36°C in 77% of patients and <35°C in 22%. Body temperature was monitored intraoperatively in 27% of the patients and forced-air warming was used in 31%. Anesthesiologists failed to accurately estimate whether their patients were hypothermic. Our results suggest that temperature monitoring and management during neuraxial anesthesia is currently inadequate. Implications In this observational study, we evaluated core temperatures and intraoperative thermal management in patients undergoing spinal or epidural anesthesia. Hypothermia was common, however, rarely detected either by temperature monitoring or estimates by anesthesiologists. In addition, it was not treated with active warming. Consequently, temperature monitoring and management have to be done during neuraxial anesthesia.

Temperature Monitoring and Management During Neuraxial Anesthesia: An Observational Study

Temperature monitoring and thermal management are rare during spinal or epidural anesthesia because clinicians apparently restrict monitoring to patients with an expected risk of hypothermia. This implies that anesthesiologists can predict patient thermal status without monitoring core temperature. We therefore, tested the hypotheses that during neuraxial anesthesia: 1) amount of core hypothermia depends on the magnitude and duration of surgery; 2) temperature monitoring and thermal management are used selectively in patients at high risk of hypothermia; and 3) anesthesiologists can estimate patient thermal status. We evaluated thermal status on arrival in the recovery room along with intraoperative thermal management and monitoring in 120 patients. Anesthesiologists were asked if their patients were hypothermic (<36 degrees C). There was no correlation between the magnitude or duration of surgery and initial postoperative core temperature in unwarmed patients. Temperature monitoring and thermal management were not used selectively in high-risk patients. Initial postoperative tympanic membrane temperatures were <36 degrees C in 77% of patients and <35 degrees C in 22%. Body temperature was monitored intraoperatively in 27% of the patients and forced-air warming was used in 31%. Anesthesiologists failed to accurately estimate whether their patients were hypothermic. Our results suggest that temperature monitoring and management during neuraxial anesthesia is currently inadequate. In this observational study, we evaluated core temperatures and intraoperative thermal management in patients undergoing spinal or epidural anesthesia. Hypothermia was common, however, rarely detected either by temperature monitoring or estimates by anesthesiologists. In addition, it was not treated with active warming. Consequently, temperature monitoring and management have to be done during neuraxial anesthesia.

Thermal X‐Ray Pulses Resulting from Pulsar Glitches

The non-spherical symmetric transport equations and exact thermal evolution model are used to calculate the transient thermal response to the pulsar’s glitches. The three ways of energy release originated from glitches, namely the ‘shell’, ‘ring’ and ‘spot’ cases are compared. Their luminosity profiles for various sets of parameters are computed. The ‘ ring ’ case is always the middle one in terms of the response time, the response duration and the intensity of the response. This is not unexpected as the volume in which glitch energy is released in the ‘ ring ’ case is between those of the ‘shell’ case and the ‘spot’ case. The effects of initial core temperature before glitch, the density at which the glitch occurs, the amount of energy released in a glitch and the equations of state on the luminosity profiles are also compared.

チタンおよびマグネシウムにおける（ｃ＋ａ）転位芯構造の分子動力学シミュレーション

To clarify the activity of the secondary pyramidal slip system in magnesium and titanium, core structures of (c+a) edge and (c+a) screw dislocations have been investigated by molecular dynamics method. The Lennard-Jones type and Finnis-Sinclair type potentials were employed. Stabled core structures were obtained in various temperature ranges. The (c+a) edge dislocation in magnesium has two kinds of core structures at 0 K; one is perfect dislocation (Type–A) and the other two 1/2 (c+a) partial dislocations (Type–B) . The type–A core structure expands to the basal plane with increasing temperature, while the type–B core is stable at higher temperatures. In the case of titanium, (c+a) edge-dislocation shows perfect dislocation independent of initial core structure and temperature. Furthermore, it never moves by applying strain. This behavior is different from the previous result of magnesium that the Type–A core changes to two partial dislocations (Type–B) and moves on the (1122) slip plane by applying strain, and the Type–B core slips without a change of structures. In the case of the (c+a) screw-dislocation, the core structures of titanium and magnesium expand on two first order pyramidal planes at 0 K, and they change to the structure expanded on a secondary pyramidal plane with increasing temperature. The activities of the secondary pyramidal slip system in titanium and magnesium can be explained from the difference of (c+a) edge dislocation core structures.

Controversies of Labor Epidural Analgesia

Controversies of Labor Epidural Analgesia

Temperature profiles during resuscitation predict survival following burns complicated by smoke inhalation injury

Temperature and resuscitation profiles of 15 non-survivors were compared with matched survivors of major burns. All patients were intubated and ventilated for smoke inhalation injury, survived more than 3 days postburn and had a cutaneous burn greater than 15 per cent of the body surface area (mean 32.3 ± 11.0 per cent SD). Cases were matched for similar ages (within 10 years) and total body surface area burn (within 10 per cent). The rate of core temperature rise following admission to the burn unit was significantly greater in survivors (mean 0.46 ± 0.18°C/h) compared with matched non-survivors (mean 0.30 ± 0.15°C/h; p<0.01). Core temperature increased at a rate of 0.27°C/h or greater in all survivors, whereas 7 non-survivors raised their core temperature at a rate less than this. The rate of skin temperature rise was also significantly greater in the survivors (mean 1.35±0.91°C/h) compared with matched non-survivors (mean 0.63±0.43°C/h, p<0.01). In 13 15 survivors, the skin temperature increased at a rate of 0.6°C/h or greater, whereas in 8 15 non-survivors skin temperature increased at a rate less than this. There was a negative relationship between initial core temperature and delay from time of burn to admission to the burns unit in non-survivors (correlation coefficient = −0.92; p<0.01), whereas there was no effect of delay in the survivors. These findings suggest that patients with a high mortality probability can be detected early in their clinical course by means of temperature profiles.

The effects of calcium channel blockade on agouti ‐induced obesity

We have previously observed that obese viable yellow (Avy/a) mice exhibit increased intracellular Ca2+ ([Ca2+]i) and fatty acid synthase (FAS) gene expression; further, recombinant agouti protein increases in cultured adipocytes and these effects are inhibited by Ca2+ channel blockade. Accordingly, we determined the effect of Ca2+ channel blockade (nifedipine for 4 wk) on FAS and obesity in transgenic mice expressing the agouti gene in a ubiquitous manner. The transgenic mice initially were significantly heavier (30.5+/-0.6 vs. 27.3+/-0.3 g; P<0.001) and exhibited a 0.81 degrees C lower initial core temperature (P<0.0005), an approximately twofold increase in fat pad weights (P=0.002), a sevenfold increase in adipose FAS activity (P=0.009), and a twofold increase in plasma insulin level (P<0.05) compared to control mice. Nifedipine treatment resulted in an 18% decrease in fat pad weights (P<0.007) and a 74% decrease in adipose FAS activity (P=0.03), normalized circulating insulin levels and insulin sensitivity (P<0.05), and transiently elevated core temperature in the transgenic mice, but was without effect in the control mice. These data suggest that agouti regulates FAS, fat storage, and possibly thermogenesis, at least partially, via a [Ca2+]i-dependent mechanism, and that Ca2+ channel blockade may partially attenuate agouti-induced obesity.

Enflurane Decreases the Threshold for Vasoconstriction More than Isoflurane or Halothane

Intraoperative hypothermia results largely from anesthetic-induced inhibition of tonic thermoregulatory vasoconstriction. Sufficient hypothermia, however, triggers peripheral vasoconstriction, which usually prevents further decrease in core temperature. The thermoregulatory effects of all volatile anesthetics have been tested in adults and/or children, but different anesthetics have not been directly compared. We therefore evaluated thermoregulatory responses during enflurane, isoflurane, and halothane administration. Anesthesia was maintained with 1 minimum alveolar anesthetic concentration (MAC) of halothane, isoflurane, or enflurane in 27 patients undergoing intraabdominal surgery. Patients were maintained normovolemic and normocapnic but were allowed to cool passively. A forearm minus fingertip, skin-temperature gradient of 4 degrees C identified significant vasoconstriction; the core temperature triggering vasoconstriction identified the threshold. Morphometric characteristics, initial core temperatures, ambient operating room temperatures, blood pressures, and anesthetic potencies were similar in each group. All eight patients given halothane vasoconstricted at a core temperature of 35.5 +/- 0.6 degrees C. Eight of the patients given isoflurane vasoconstricted at a core temperature of 35.2 +/- 0.5 degrees C. However, two others did not at minimum core temperatures of 34.0 and 33.8 degrees C. Only one patient given enflurane vasoconstricted at a core temperature of 34.6 degrees C. The other six patients never vasoconstricted, at minimum core temperatures of 33.6 +/- 0.4 degrees C. Our data indicate that enflurane profoundly inhibits thermoregulatory responses in children. The mechanism for this extraordinary inhibition remains unknown but does not result from any obvious anesthetic pharmacology or thermoregulatory physiology. We conclude that unwarmed pediatric patients will become colder when anesthetized with enflurane than with halothane or isoflurane. (Anesth Analg 1996;83:595-9)

Cardiopulmonary bypass resuscitation for accidental hypothermia: Ann. Thorac. Surg. 1994; 58/3: 895–898

Many victims of accidental hypothermia have been suc­ cessfully resuscitated with cardiopulmonary bypass, but questions remain regarding treatment indications and efficacy. To assess the role of cardiopulmonary bypass in resuscitation from hypothermia, a collective literature review was performed. Data on 68 hypothermic patients resuscitated with cardiopulmonary bypass were ana­ lyzed. Impairment from alcohol, drug abuse, or mental illness was the most common predisposing factor for accidental hypothermia. Mean initial core temperature was 21°C. Sixty-one patients (90%) were in cardiac arrest. Femoral-femoral bypass was used in 72% of patients. Overall survival was 60%. Eighty percent of survivors returned to their previous level of function. Sixty-seven percent of nonsurvivors died because of inability to establish a cardiac rhythm or wean from bypass. Patient age, type of cardiopulmonary bypass (femoral-femoral or atrial-aortic), and initial core temperature were not sig­ nificant prognostic indicators. There were no survivors among the 6 patients with a core temperature less than

Treatment of hypothermia in trauma victims: thermodynamic considerations.

The relatively high specific heat of the human body makes hypothermia very difficult to treat. Although there are many treatment methods available, most evaluations of rewarming techniques are based on clinically observed rewarming rates, and they do not take into account initial core temperature, ambient temperature, the patient's own heat production, the effects of anesthesia, paralytic agents, and other variables. A heat transfer model is proposed that simulates the flow of heat through the body of a hypothermic patient. The model uses first principles involved in heat transfer and thermodynamics to describe the effects of currently available rewarming techniques. A commercially available routine is used to solve the equations, which also include any heat exchange between the patient's body and the environment, as well as metabolic heat generation as a function of time and core temperature. This thermodynamic analysis of rewarming, based on computer modeling of heat transfer, provides a scientific basis on which to establish guidelines for appropriate selection of treatment strategies for hypothermia, and it indicates that direct blood warming or infusion of warm intravenous fluids are the most effective rewarming techniques.

A second postcooling afterdrop: more evidence for a convective mechanism

An attempt was made to demonstrate the importance of increased perfusion of cold tissue in core temperature afterdrop. Five male subjects were cooled twice in water (8 degrees C) for 53-80 min. They were then rewarmed by one of two methods (shivering thermogenesis or treadmill exercise) for another 40-65 min, after which they entered a warm bath (40 degrees C). Esophageal temperature (Tes) as well as thigh and calf muscle temperatures at three depths (1.5, 3.0, and 4.5 cm) were measured. Cold water immersion was terminated at Tes varying between 33.0 and 34.5 degrees C. For each subject this temperature was similar in both trials. The initial core temperature afterdrop was 58% greater during exercise (mean +/- SE, 0.65 +/- 0.10 degrees C) than shivering (0.41 +/- 0.06 degrees C) (P < 0.005). Within the first 5 min after subjects entered the warm bath the initial rate of rewarming (previously established during shivering or exercise, approximately 0.07 degrees C/min) decreased. The attenuation was 0.088 +/- 0.03 degrees C/min (P < 0.025) after shivering and 0.062 +/- 0.022 degrees C/min (P < 0.025) after exercise. In 4 of 10 trials (2 after shivering and 2 after exercise) a second afterdrop occurred during this period. We suggest that increased perfusion of cold tissue is one probable mechanism responsible for attenuation or reversal of the initial rewarming rate. These results have important implications for treatment of hypothermia victims, even when treatment commences long after removal from cold water.

A method for estimating eruption rates of planetary lava flows

A model that accounts for radiative losses from a partially crusted hotter core can be used to constrain eruption rates of single-lobed planetary lava flows by assuming thermal characteristics are similar to terrestrial flows. Eruption rate can be expressed as a function of the area fraction of core exposed, initial core temperature, core temperature when the flow stops advancing, crust thickness, flow thickness, and the density and heat capacity of the lava.

Prognostic Factors in Severe Accidental Hypothermia

The May 1986 Mt. Hood climbing disaster presented Portland area hospitals the opportunity to initiate a trial of extracorporeal rewarming using cardiopulmonary bypass in ten severely hypothermic patients (two survivors). The data from this experience as well as others previously reported can yield prognostic indicators of survival in cases of accidental hypothermia. These are demonstrated to include: the presence of underlying medical illness, duration of cold exposure, initial core temperature, mental status, the presence of spontaneous respirations, presenting cardiac rate and rhythm, and arterial oxygen tension. Profound hyperkalemia and markedly elevated serum ammonia levels indicate cell lysis; significant hypofibrinogenemia suggests intravascular thrombosis and each laboratory marker predicts a dire outcome. The treatment of choice for severe accidental hypothermia is felt to be rapid core rewarming on cardiopulmonary bypass.

The development of thermoregulation after prenatal exposure to alcohol in rats.

The effect of prenatal exposure to alcohol on the development of thermoregulation and behavioral thermogenesis was assessed in rats. Pups at 5, 10, 15, and 20 days of age were chosen from litters with one of three prenatal treatment histories: liquid diet with 35% ethanol-derived-calories (35% EDC), pair-fed control (0% EDC), or lab chow control (LC). Subjects were removed from the home nest and had their initial rectal temperatures recorded before placement alone in the center of an observational chamber in a testing room maintained at 23-24 degrees C. Rectal temperatures were recorded again every hour for the next 4 h. Speed to reach the wall for behavioral thermogenesis (wall-huddling) was also measured at each hourly interval. With increasing age, all pups displayed increasing ability to maintain their initial core temperature, but prenatal exposure to alcohol had a significant effect in retarding the development of thermoregulation. At 5 and 10 days of age, alcohol-exposed pups had significantly lower rectal temperatures at 1-4 h out of the nest compared to control pups. In addition, the speed to reach the wall was slower in 35% EDC pups than in pups from the two control groups, suggesting a deficit in behavioral thermogenesis as well. These results agree with others demonstrating alcohol-induced development delays, and may have implications for other behavioral deficits seen after prenatal exposure to alcohol.

Prognostic variables in nearly drowned, comatose children.

Prognostic variables were evaluated in 51 nearly drowned, comatose children, and they included values for age, estimated submersion time, initial arterial pH and core temperature, mean intracranial pressure (ICP), and mean cerebral perfusion pressure (CPP); the latter two values were obtained during the first 24 hours. There were 33 survivors (19 with intact neurologic survival and 14 with brain damage) and 18 deaths. Estimated submersion time and mean ICP and mean CPP determined survival but could not predict the neurologic outcome (intact survival or brain damage). Age, arterial pH, and core temperature were not useful variables in predicting outcome. This study discourages the use of these unreliable variables in predicting survival in nearly drowned, comatose victims and, in addition, cautions against the use of mean ICP, mean CPP, and submersion time as predictors of neurologic outcome. Since mean ICP and mean CPP measurements are reliable in predicting survival but not neurologic outcome, major efforts should be undertaken to explore neurophysiologic and metabolic prognostic factors that may either discourage or mandate early institution of aggressive cerebral resuscitative measures in nearly drowned victims.

Whole body hyperthermia (41-42 degrees C): a simple technique for unanesthetized mice.

A technique for accomplishing 41-42 degrees C whole body hyperthermia (WBH) in unrestrained, unanesthetized mice using a simple apparatus is reported. This method combines a radiant heat technology with monitoring of individual rectal temperatures at 10-min intervals. In 66 heating sessions, involving 116 AKR mice and a total of 619 WBH treatments, the mortality rate was less than 1%. Treatment at 41-42 degrees C for periods of up to 120 min were accomplished. Relationships of several variables of mouse temperature-time profiles were studied including (1) initial core temperature, (2) rate of heating, (3) whole body irradiation, and (4) the presence of tumor (transplanted AKR leukemia). Sham treatments produce a consistent temperature-time profile showing about a 1 degree C rise. Between-mouse variability, as well as between-treatment variability in individual animals was estimated. Thermal mapping of the device demonstrates a range from 32-38 degrees C of the air temperature in the zone with the mice to a high of 47 degrees C near to the radiant heating surface at the top of the apparatus.