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PubMed1993

Core temperature measurement: a comparison of rectal, axillary and pulmonary artery blood temperature.

This research study was undertaken to determine the relationship between pulmonary artery (PA) blood temperature, rectal temperature and axillary temperature for adult patients admitted to an intensive care unit (ICU). 31 adults had their temperatures monitored. Simultaneous recordings of PA blood temperature, rectal temperature and axillary temperature were taken every 4h for up to 7 days. The mean difference between rectal and axillary temperature for all 31 patients was 0.32 degree C. Of the 16 patients who had their PA blood temperature monitored mean rectal temperature was 0.1 degree C above PA blood temperature and mean axillary temperature was 0.19 degree C below PA blood temperature. Very high statistical correlations were obtained which demonstrate the strength of the relationships between the three sites (rectal-axillary temperature difference R = 0.97; PA blood-rectal temperature difference R = 0.99; PA blood-axilla temperature difference R = 0.97). The linear relationship between the three sites studied was not found to be affected by age, gender, number of temperature samples taken, post/non-operative admission or peripheral temperature.

Adult↗

PubMed2005

Both incubation temperature and posthatching temperature affect swimming performance and morphology of wood frog tadpoles (Rana sylvatica).

In many oviparous vertebrates, hatchling phenotypes are influenced by egg incubation temperature. Many of those phenotypic traits can also acclimate to long-term thermal conditions of juveniles and adults, yet the interactive effects of prehatching and posthatching temperatures on phenotypes have not been studied. To address such interaction, we incubated eggs of wood frogs (Rana sylvatica) at two temperatures and subsequently reared larvae at three temperatures in a fully factorial design. We measured body size, size-independent morphology, and burst swimming speed at one developmental stage. Body size was independent of egg temperature but decreased significantly with increasing larval temperature. Size-independent morphology depended in complex ways on both temperature treatments directly and on their interaction. Burst speed was not influenced directly by egg temperature but was influenced by larval temperature and by the interactions among egg temperature, larval temperature, and test temperature. Our results indicate pervasive effects of egg temperature even late in the larval period and show that prehatching and posthatching temperatures can interact to affect various phenotypic traits. Tadpoles may be able to alter the long-term effects of incubation temperature by choosing particular larval developmental temperatures. Thus, the importance of incubation temperature in oviparous vertebrates should be evaluated by considering the effects of posthatching temperatures.

Animals↗

PubMed1998

Brain temperature exceeds systemic temperature in head-injured patients.

OBJECTIVE: To identify the temperature differences in readings taken from the brain, jugular bulb, and core body in head-injured patients. DESIGN: Prospective, observational study. SETTING: Neurosurgical intensive care unit of a university-affiliated county hospital. PATIENTS: Thirty patients with severe head injuries had measurements of brain and core body temperatures. Fourteen patients also had measurements of jugular venous blood at the level of the jugular bulb. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Brain temperature was increased an average of 2.0 degrees F (1.1 degrees C) over the core body temperature. In individual patients, the average brain temperature increase over the core body temperature ranged from -0.5 degrees to 3.8 degrees F (-0.30 degrees to 2.1 degrees C). Jugular vein and core body temperatures were similar. The difference in the brain and body temperatures increased when cerebral perfusion pressure decreased to between 20 and 50 mm Hg. The difference in the brain and body temperatures decreased in those patients treated with barbiturate coma. CONCLUSIONS: Direct measurement of temperature in head-injured patients is a safe procedure. Temperatures in the brain are typically increased over the core body temperature and the jugular bulb temperatures. Jugular vein temperature measurement is not a good measurement of brain temperature since it reflects body, not brain temperature. These findings support the potential importance of monitoring brain temperature and the importance of controlling fever in severely head-injured patients since brain temperature may be higher than expected.

Adult↗

PubMed1998

Small changes in ambient temperature cause large changes in 3,4-methylenedioxymethamphetamine (MDMA)-induced serotonin neurotoxicity and core body temperature in the rat.

The amphetamine derivative 3,4-methylenedioxymethamphetamine (MDMA) is a drug of abuse and has been shown to be neurotoxic to 5-HT terminals in many species. MDMA-engendered neurotoxicity has been shown to be affected by both ambient temperature and core body temperature. We now report that small (2 degreesC) changes in ambient temperature produce changes in core temperature in MDMA-treated rats, but the same changes in ambient temperature do not affect core temperature of saline-treated animals. Furthermore, increases in core temperature of MDMA-treated animals increase neurotoxicity. Rats were given MDMA (20 or 40 mg/kg) or saline and placed in an ambient temperature of 20, 22, 24, 26, 28, or 30 degreesC using a novel temperature measurement apparatus that controls ambient temperature +/-0.5 degrees C. Two weeks after MDMA treatment, the rats were killed, and regional 5-HT and 5-hydroxyindole acetic acid levels were analyzed as a measure of neurotoxicity. Rats treated with MDMA at 20 and 22 degrees C showed a hypothermic core temperature response. Treatment with MDMA at 28 and 30 degreesC produced a hyperthermic response. At ambient temperatures of 20-24 degrees C, neurotoxicity was not observed in the frontal cortex, somatosensory cortex, hippocampus, or striatum. At ambient temperatures of 26-30 degrees C, neurotoxicity was seen and correlated with core temperature in all regions examined. These data indicate that ambient temperature has a significant affect on MDMA neurotoxicity, core temperature, and thermoregulation in rats. This finding has implications on both the temperature dependence of the mechanism of MDMA neurotoxicity and human use because fatal hyperthermia is associated with MDMA use in humans.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1990

Effects of spinal cord temperature on the generation and transmission of temperature signals in the goat.

A series of 38 experiments were performed in five conscious goats at air temperatures of +20 degrees C or +30 degrees C to see whether a temperature dependence of spinal cord signal transmission affects the relationships between body temperature and metabolic rate (MR) or respiratory evaporative heat loss (REHL). Prior to the experiments the animals received peridural thermodes to clamp the spinal cord temperature by perfusion temperatures of 31 degrees C, 38 degrees C or 43 degrees C (45 degrees C), carotid loops to clamp the brain temperature at 39 degrees C or 39.5 degrees C, and arteriovenous shunts to alter the trunk temperature and to determine thresholds and slopes of MR and REHL over trunk temperature. The trunk temperature thresholds, at which MR and REHL increased, were inversely related to the spinal cord temperature, thereby confirming previous observations on the generation of specific spinal temperature signals. The slopes at which MR rose below the threshold, increased with decreasing spinal cord temperature. The slopes of REHL over trunk temperature were independent of spinal cord temperature. Both observations are at variance with previously observed temperature effects on hypothalamic signal transmission and imply that temperature-dependent signal transmission at the spinal level cannot account for nonlinear interaction of various body temperatures in the control of MR and REHL.

Animals↗

PubMed2005

[Changes in core temperature associated with lower extremity tourniquet--the influence of ambient temperature and warming equipments].

BACKGROUND: We investigated changes in core temperature associated with lower extremity tourniquet (TQ) under two different ambient temperatures (1) and two different warming equipments (2) under general anesthesia combined with lumbar epidural anesthesia. METHODS: (1) The values of core temperature at ambient temperature of either 22 degrees C (n = 15) or 20 degrees C (n=15) were recorded after induction of anesthesia, at start of TQ application, at the termination of TQ application, and 14 minute after TQ release. (2) The values of core temperature using either air-forced warming or active heated i.v. at ambient temperature 20 degrees C were recorded at four points as mentioned above. RESULTS: (1) Changes in core temperature were not observed during TQ application at ambient temperature both 20 degrees C and 22 degrees C. Core temperatures in both groups decreased significantly after TQ release, and core temperatures at termination of TQ application and after TQ release at ambient temperature 20 degrees C were significantly lower than those at ambient temperature 22 degrees C. (2) Significant increases in core temperatures using two different warming equipments were observed at termination of TQ application and after TQ release at ambient temperature 20 degrees C. Core temperatures using air-forced warming were maintained during the investigation, though significant decrease in core temperature using active heated i.v. was recorded after TQ release. CONCLUSIONS: Air-forced warming maintains core temperature efficiently associated with lower extremity tourniquet.

Aged↗

PubMed1994

Influence of changing temperature on growth rate and competition between two psychrotolerant Antarctic bacteria: competition and survival in non-steady-state temperature environments.

Competition between two psychrotolerant bacteria was examined in glycerol-limited chemostat experiments subjected to non-steady-state conditions of temperature. One bacterium, a Brevibacterium sp. strain designated CR3/1/15, responded rapidly to temperature change, while a second, Hydrogenophaga pseudoflava, designated CR3/2/10, exhibited a lag in growth after a shift-down during a square-wave temperature cycle but not after a shift-up. The effects on competition and survival by these bacteria of both sine-wave and square-wave temperature changes between 2 and 16 degrees C over a 24-h cycle time were examined, as well as square-wave cycles over 12 and 96 h. The changing proportion of each bacterium in the chemostat was determined by plate counting at regular intervals. Under a sine-wave temperature cycle H. psedoflava outcompeted the Brevibacterium sp., but under square-wave temperature cycles the two bacteria coexisted because the lag by H. pseudoflava after the temperature shift-down favored the faster-responding Brevibacterium sp. The two bacteria thus exhibited different survival strategies, with H. pseudoflava adapted to effective competition under steady-state conditions and the Brevibacterium sp. adapted to rapid adaptation and survival in a changing environment. The degree of perturbation of the bacteria, expressed as a temperature challenge index (delta temp/delta time), was greater under a square-wave temperature cycle than under a sine-wave cycle of equivalent amplitude and frequency, and higher-temperature challenge favored the Brevibacterium sp. A computer model was developed to examine competition between the bacteria in transient environments. The frequency of the temperature cycle influenced competition, as with a longer cycle (96 h) the significance of the lag by H. pseudoflava decreased compared with that of a 24-h cycle, and H. pseudoflava predominated in a mixed culture with a 96-h cycle. The shift-down lag by H. pseudoflava, during which it adapted to low temperature, disadvantaged it in a changing temperature environment, but at a short cycle time (12 h) this disadvantage was countered by the incomplete loss of low-temperature adaptation between cycles and thus the carryover of some low-temperature adaptation. Also, it was demonstrated that, as well as consideration of the effect of temperature changes on inducing lags in growth, the loss of adaptation to low temperature between cycles had to be taken into account in the computer model if it was to reproduce the trends in the experimental data.

Antarctic Regions↗

PubMed1996

Jugular bulb temperature: comparison with brain surface and core temperatures in neurosurgical patients during mild hypothermia.

Blood temperature at the jugular bulb was monitored in 10 patients undergoing neurovascular procedures that used induced mild hypothermia, and its correlation with surface brain, core, and peripheral temperatures was determined. The study was motivated by the difficulty encountered in directly measuring global brain temperature and the poor correlations between various core and peripheral sites temperatures and brain temperature, particularly during deep hypothermia. Although not statistically significant, previous studies have suggested a trend toward higher brain temperatures. Temperatures from the jugular bulb (collected using a No. 5 French Swan-Ganz catheter) as well as from subdural, pulmonary artery, esophagus, tympanic membrane, and bladder sites were analyzed during three surgical conditions: prior to incision, with the dura open, and after closure of the dura. No complications related to placement of the jugular bulb catheter, induced hypothermia, or temperature monitoring were seen. The authors found that jugular bulb temperature was similar to pulmonary artery and esophageal temperatures; although prior to incision it tended to be higher than that found at the pulmonary artery, most commonly by 0.2 degrees C. Surface brain temperature was cooler than all other temperatures (p < 0.05), except that of the tympanic membrane, and was particularly sensitive to environmental variations. Finally, as has been shown by others, bladder temperature lagged substantially behind core temperatures particularly during rapid cooling and rewarming of the patient. In summary, monitoring of jugular bulb temperature is a feasible technique, and temperatures measured in the jugular bulb are similar to core temperatures.

Adult↗

PubMed1993

Evidence that the antinociceptive tail-flick response is produced independently from changes in either tail-skin temperature or core temperature.

It has recently been hypothesized that tail-skin temperature may exert a profound influence on the latency of the tail-flick response to radiant heat. Several recent reports in the literature urge investigators to assess tail temperatures concurrently when using the tail-flick test and to adjust the tail-flick latency by a coefficient when a change in tail temperature is detected. Because much of the supporting evidence of this hypothesis was strictly correlational, the purpose of the present study was to determine whether tail-skin temperature is an important factor contributing to the latency of the tail-flick response to radiant heat. The effects of a series of pharmacological and non-pharmacological manipulations on tail-skin temperature and response latencies were assessed using either a low-intensity or high-intensity tail-flick stimulus. In addition, colonic temperature was evaluated. None of the drug treatments yielded a significant correlation between tail temperature and tail-flick latency. Of the seven drugs tested, only mecamylamine produced a consistent change in tail-skin temperature. Although mecamylamine significantly elevated tail temperature by more than 2 degrees C, it failed to alter response latencies. Similarly tail submergence into 5 degrees C water for 10 sec led to profound decreases in tail temperature ranging from -6.5 to -7.6 degrees C while producing only minimal increases in tail-flick latency. Conversely, submerging the tail in 38 degrees C water or placing the animals over a heating pad maintained at 38 degrees C increased tail temperatures at least 2 degrees C without affecting response latencies. Inverse correlations were found between tail-flick latency and colonic temperature after morphine, delta 9-tetrahydrocannabinal (delta 9-THC), and nicotine administration; however, these relationships do not appear to be causal. Sodium barbital produced far more hypothermia than any other agent, but did not produce any antinociception. Moreover, placing subjects in heated cages increased tail-skin temperature between 2 and 4 degrees C and blocked the hypothermic effects of morphine and delta 9-THC without reducing the antinociceptive potencies of these agents. These findings indicate that tail-skin and core temperatures have a negligible influence on the tail-flick response. We conclude that monitoring tail-skin or core temperatures when employing the tail-flick test is unnecessary and altering tail-flick latencies to account for changes in tail temperature is unwarranted.

Analgesics↗

PubMed2001

Growth temperature can alter the temperature dependent stimulation of photosynthesis by elevated carbon dioxide in Albutilon theophrasti.

Stimulation of photosynthesis in response to elevated carbon dioxide concentration [CO2] in the short-term (min) should be highly temperature dependent at high photon flux. However, it is unclear if long-term (days, weeks) adaptation to a given growth temperature alters the temperature-dependent stimulation of photosynthesis to [CO2]. In velveltleaf (Albutilon theophrasti), the response of photosynthesis, determined as CO2 assimilation, was measured over a range of internal CO2 concentrations at 7 short-term measurement (12, 16, 20, 24, 28, 32, 36 degrees C) temperatures for each of 4 long-term growth (16, 20, 28 and 32 degrees C) temperatures. In vivo estimates of VCmax, the maximum RuBP saturated rate of carboxylation, and Jmax, the light-saturated rate of potential electron transport, were determined from gas exchange measurements for each temperature combination. Overall, previous exposure to a given growth temperature adjusted the optimal temperatures of Jmax and VCmax with subsequently greater enhancement of photosynthesis at elevated [CO2] (i.e., a greater enhancement of photosynthesis at elevated [CO2] was observed at low measurement temperatures for A. theophrasti grown at low growth temperatures compared with higher growth temperatures, and vice versa for plants grown and measured at high temperatures). Previous biochemical based models used to predict the interaction between rising [CO2] and temperature on photosynthesis have generally assumed no growth temperature effect on carboxylation kinetics or no limitation by Jmax. In the current study, these models over predicted the temperature dependence of the photosynthetic response to elevated [CO2] at temperatures above 24 degrees C. If these models are modified to include long-term adjustments of Jmax and VCmax to growth temperature, then greater agreement between observed and predicted values was obtained.

Journal Article↗

PubMed1971

The influence of deep body temperatures and skin temperatures on peripheral blood flow in the pig.

1. The rate of blood flow through the tail of the pig has been measured by means of venous occlusion plethysmography using a mercury in rubber strain gauge. Conscious animals were used in all experiments because previous work had demonstrated that anaesthetics interfere with the animal's ability to vasoconstrict.2. Graded changes in the temperature of the hypothalamus were imposed by means of an implanted thermode. It was found that the change in blood flow depended on the extent of the change in hypothalamic temperature and on the ambient temperature. Below 20 degrees C ambient temperature, heating the hypothalamus did not cause vasodilatation and at 30 degrees C ambient temperature, cooling the hypothalamus caused only slight vasoconstriction, but at 25 degrees C ambient temperature, changes in hypothalamic temperature caused changes in blood flow from full vasoconstriction to full vasodilatation.3. The skin temperature on the trunk was changed by means of water circulated through tubes sewn into a coat worn by the pig. Blood flow in the tail, which was outside the coat, depended on the skin temperature of the trunk, the ambient temperature, and the temperature of the hypothalamus, all of which were varied separately.4. A thermode was implanted in the epidural space in the cervical region of the spinal cord. The change in blood flow in the tail which accompanied a change in thermode temperature was found to depend on the temperature of the thermode and the ambient temperature. Cooling the spine while the hypothalamus was being heated to 43 degrees C resulted in a decrease in blood flow, but when the spine was heated while the hypothalamus was being cooled the increase in blood flow was only slight.5. Local stimulus to the tail in the form of infra-red heat, or increased air movement was followed by changes in blood flow even when deep body temperature remained stable.

Animals↗

PubMed2000

Radiant warmers versus incubators for regulating body temperature in newborn infants.

BACKGROUND: This section is under preparation and will be included in the next issue. OBJECTIVES: To assess the effects of radiant warmers versus incubators (in the neonatal period) on fluid and electrolyte balance, neonatal morbidity and mortality. SEARCH STRATEGY: The standard strategy of the Cochrane Neonatal Review Group was used. This includes searches of the Oxford Database of Perinatal Trials, Medline, previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants, journal handsearching mainly in the English language. SELECTION CRITERIA: All randomised or quasi-randomised trials in which radiant warmers are compared to incubators in a neonatal population. DATA COLLECTION AND ANALYSIS: Methods used to collect data from the included studies: Each author extracted data separately, then compared and resolved differences. A referee was sought for unresolved differences. Methods used to synthesise the data : Standard method of Neonatal Review Group with the use of weighted mean difference for outcome data measured on a continuous scale. MAIN RESULTS: A statistically significant increase in insensible water loss (IWL) was shown in neonates nursed under radiant warmers (WMD 0.94g/Kg/day, 95% CI 0.48, 1.41). A trend towards increased oxygen consumption which was not statistically significant was shown for the radiant warmer group (WMD 0. 27mL/kg/min, 95% CI -0.10, 0.63). A comparison of the radiant warmers with heat shields vs incubator without heat shields showed a similar trend for increased IWL in the radiant warmer group which was not statistically significant (WMD 1.00g/kg/day, 95% CI -0.10, 2. 10). No difference was shown in the rate of oxygen consumption when radiant warmers with heat shields were compared to incubators (WMD -0.05, 95% CI -0.84, 0.74). REVIEWER'S CONCLUSIONS: Radiant warmers result in increased IWL compared to incubators which needs to be taken into account when calculating daily fluid requirements.The results of this review do not provide sufficient evidence on important outcomes with the use of radiant warmers vs incubators to guide clinical practice. Further randomised controlled trials are required to assess the role of radiant warmers in neonatal care with particular attention to the extremely low birthweight population.

Body Temperature Regulation↗

PubMed1952