Tympanic temperature matches the brain temperature, fact or fiction?

Background: Hypothermia is a known neuronal protecting agent and used in post cardiac arrest. However, its use for stroke and brain trauma has not made any progress due to the lack of accurate way of measuring brain temperature. Hence, hypothermic degree and duration for it to be therapeutic is unknown. The phase I Check Brain Temperature Study was to define regional brain temperatures in normal individuals via MRI thermometry. The established brain temperature map can be used as the baseline to provide therapeutic hypothermia. Method: Temperatures of 5 regions of interest (ROI) of brain (frontal lobe, thalamus, hypothalamus, occipital lobe and cerebellum) were measured in 10 healthy individuals by using proton resonance frequency MRI spectroscopy single voxel method. The scanning protocol include a whole brain anatomical images, (3DFSPGR : TR/TE=150/3.9ms, FOV=24cm,matrix=256x256, slice thickness =1 mm.) and spectroscopy PRESS (TR/TE=1500/144 ms, 8 nex, 2 x 2 x 2 cm^3) on a GE 3T scanner. Ten right handed men (18<age<80) were recruited and their oral and tympanic temperatures were monitored. Average whole head temperature=average of oral temp+tympanic temp and average brain temp=average of temp of 5 regions of interest. Two tails, paired t-test used to compare temps between subjects and ROIs. Results: Average temperature differences between brain (38.2 °C) and head (36.5 °C) is 1.8 °C (p< 0.0000002). Thalamus has the highest temperature among all ROIs in brain. Brain temperature > oral temperature > tympanic temperature. Conclusion: Brain temperatures may not correlate to body temperatures and there is a regional difference. Our finding will be used as the baseline brain temperature map when hypothermia is applied in patients with hemisphere stroke in the phase II study.

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Temperature Difference Between the Body Core and the Arterial Blood Supplied to the Brain During Hyperthermia or Hypothermia

10.1115/imece2001/htd-24418 ◽

2001 ◽

Author(s):

Liang Zhu ◽

Maithreyi Bommadevara

Keyword(s):

Blood Vessel ◽

Temperature Difference ◽

Carotid Arteries ◽

Brain Temperature ◽

Indirect Evidence ◽

Blood Perfusion ◽

The Body ◽

Arterial Blood ◽

Body Core ◽

The Brain

Abstract In this study a theoretical model was developed to evaluate the temperature difference between the body core and the arterial blood supplied to the brain. Several factors including the local blood perfusion rate, blood vessel bifurcation in the neck, and blood vessel pairs on both sides of the neck were considered in the model. The theoretical approach was used to estimate the potential for cooling of blood in the carotid artery on its way to the brain by heat exchange with its countercurrent jugular vein and by the radial heat conduction loss to the cool neck surface. It shows that blood temperature along the common and internal carotid arteries typically decreases up to 0.86°C during hyperthermia. Selectively cooling the neck surface during hypothermia increases the heat loss from the carotid arteries and results in approximately 1.2°C in the carotid arterial temperature. This research could provide indirect evidence of the existence of selective brain cooling (SBC) in humans during hyperthermia. The simulated results can also be used to evaluate the feasibility of lowering brain temperature effectively by selectively cooling the head and neck surface during hypothermia treatment for brain injury or multiple sclerosis.

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Sweating responses during changes of hypothalamic temperature in the rhesus monkey

Journal of Applied Physiology ◽

10.1152/jappl.1976.40.5.653 ◽

1976 ◽

Vol 40 (5) ◽

pp. 653-657 ◽

Cited By ~ 25

Author(s):

K. A. Smiles ◽

R. S. Elizondo ◽

C. C. Barney

Keyword(s):

Rhesus Monkey ◽

Skin Temperature ◽

Sweat Rate ◽

Brain Temperature ◽

Hypothalamic Area ◽

Indirect Measurements ◽

Hypothalamic Temperature ◽

Temperature Changes ◽

Experimental Analogue ◽

The Brain

A technique is presented for preparing a durable thermode implant in the hypothalamus of the rhesus monkey. In unanesthetized monkeys implanted with thermodes in the anterior hypothalamic area of the brain, a linear relation was found between local sweat rates on the general body surface and clamped hypothalamic temperature. Changes in skin temperature were found to shift the hypothalamic set-point temperature at which sweating began but did not alter the gain of the hypothalamic temperature-sweat rate relationship. This study provides direct support for the concept that central brain temperature and skin temperature interact additively in the control of sweating in higher primates. Due to the very close similarity between these responses and those seen with indirect measurements of brain temperature in men, the rhesus monkey is seen as an excellent experimental analogue for studying human thermoregulation.

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The Effect of Selective Brain Cooling on Intracerebral Temperature during Craniotomy

Anaesthesia and Intensive Care ◽

10.1177/0310057x0203000207 ◽

2002 ◽

Vol 30 (2) ◽

pp. 167-170 ◽

Cited By ~ 10

Author(s):

C. C. Iatrou ◽

C. M. Domaingue ◽

R. D. Thomas ◽

D. H. Nye

Keyword(s):

Brain Temperature ◽

Tissue Temperature ◽

General Anaesthetic ◽

Irrigation Fluid ◽

Sterile Needle ◽

Maximum Decrease ◽

Systemic Hypothermia ◽

Baseline Temperature ◽

The Brain ◽

Harmful Effects

In this study we investigated the effect of topical application of cool irrigation fluid on brain tissue temperature during craniotomy. Eight patients were given a standard general anaesthetic for craniotomy. Distal oesophageal and nasopharyngeal temperatures were measured continuously and systemic normothermia was maintained. A sterile needle temperature probe was inserted 18 mm into the cerebrum to measure brain temperature. Brain temperatures were recorded for five minutes while the brain was irrigated with 1000 ml of normal saline at a temperature of 30°C. Measurement continued until the brain temperature returned to baseline. The mean maximum decrease in cerebral parenchymal temperature following irrigation was 1.6±0.5°C (P<0.01). The average time to return to baseline temperature after cessation of irrigation was 5.3±1.5 minutes. Cooling the brain has a marked protective effect after brain injury, but systemic hypothermia can produce significant harmful effects. This study demonstrates that the use of cool irrigation fluid during neurosurgery is a simple and effective method of cooling the brain whilst minimizing the use of systemic hypothermia.

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Acclimation, temperature selection, and heat exchange in the turtle, Chrysemys scripta

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1980.238.5.r443 ◽

1980 ◽

Vol 238 (5) ◽

pp. R443-R446 ◽

Cited By ~ 1

Author(s):

L. I. Crawshaw ◽

M. H. Johnston ◽

D. E. Lemons

Keyword(s):

Heart Rate ◽

Initial Temperature ◽

Brain Temperature ◽

Time Of Day ◽

Acclimation Temperature ◽

Mean Body Temperature ◽

Rapid Changes ◽

Ambient Water Temperature ◽

The Brain ◽

Turtle Heart

Turtles acclimated to temperatures between 3 and 19 degrees C were placed in a thermal gradient. The animals usually selected temperatures above 28 degrees C within 1 h after placement in the gradient, attaining a final thermal preferendum between 31 and 33 degrees C. Turtles placed in the gradient for extended periods of time were more active during the day; the temperature selected was not related to activity or time of day. Turtles were transferred from a constant temperature bath at 10 or 30 degrees C to a calorimeter at 30 or 10 degrees C. Mean body temperature (Tb) and temperatures of the heart (The), brain (Tbr), and cloaca (Tcl) as well as heart rate were continuously monitored. In a 0.76-kg turtle, temperatures increased to two-thirds of the final difference between the initial temperature and the final temperature in the following times (min): Tb, 5.5; The, 6.0; Tcl, 9.0. The increase in Tbr varied depending on whether the head was extended or retracted. Rapid changes in ambient water temperature had relatively little effect on the heart rate of a submerged turtle. Heart rates were closely related to The and were practically independent of brain temperature.

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A cyclooxygenase-2 inhibitor attenuates spontaneous and TNF-α-induced non-rapid eye movement sleep in rabbits

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00609.2002 ◽

2003 ◽

Vol 285 (1) ◽

pp. R99-R109 ◽

Cited By ~ 17

Author(s):

Hitoshi Yoshida ◽

Takeshi Kubota ◽

James M. Krueger

Keyword(s):

Eye Movement ◽

Slow Wave ◽

Brain Temperature ◽

Wave Activity ◽

Slow Wave Activity ◽

Rapid Eye Movement ◽

Rapid Eye Movement Sleep ◽

Tnf Α ◽

Cox 2 ◽

The Brain

Sleep is regulated in part by the brain cytokine network, including tumor necrosis factor-α (TNF-α). TNF-α activates the transcription factor nuclear factor-κB, which in turn promotes transcription of many genes, including cyclooxygenase-2 (COX-2). COX-2 is in the brain and is an enzyme responsible for production of prostaglandin D2. The hypothesis that central COX-2 plays a role in the regulation of spontaneous and TNF-α-induced sleep was investigated. Three doses (0.5, 5, and 50 μg) of NS-398, a highly selective COX-2 inhibitor, were injected intracerebroventricularly. The highest dose decreased non-rapid eye movement sleep. The intermediate and highest doses decreased electroencephalographic slow-wave activity; the greatest reduction occurred after 50 μg of NS-398 during the first 3-h postinjection period. Rapid eye movement sleep and brain temperature were not altered by any dose of NS-398. Pretreatment of rabbits with 5 or 50 μg of NS-398 blocked the TNF-α-induced increases in non-rapid eye movement sleep, electroencephalographic slow-wave activity, and brain temperature. These data suggest that COX-2 is involved in the regulation of spontaneous and TNF-α-induced sleep.

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Canine hyperthermia with cerebral protection

Journal of Applied Physiology ◽

10.1152/jappl.1976.40.4.543 ◽

1976 ◽

Vol 40 (4) ◽

pp. 543-548 ◽

Cited By ~ 17

Author(s):

R. W. Carithers ◽

R. C. Seagrave

Keyword(s):

Core Temperature ◽

Cold Water ◽

Brain Temperature ◽

Body Core Temperature ◽

Whole Body ◽

Similar Time ◽

Data Points ◽

Body Core ◽

Heat Transfer System ◽

The Brain

Extreme whole-body hyperthermia was achieved without lasting side effects in canines by elevating body core temperature to 42 degrees C, using a warm water bath. Cold water irrigation of the nasal alar fold permitted an additional core temperature elevation of 0.5–1.0 degrees C above brain temperature for periods up to 1.5 h. The brain-core temperature differential was maintained by a physiological arteriovenous heat exchanger located at the base of the brain. The maximum tolerable core temperature for the 21 nonirrigated dogs was 42 degrees C for 60–90 min, whereas that for the 28 irrigated dogs was 42.5–43 degrees C for similar time intervals. A mathematical model of the total heat transfer system described the observed dynamic temperature responses. It was the solution of a differential equation which fit the normalized experimental data points and predicted reasonable values for known and unknown experimental parameters.

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Effects of temperature and PCO2 on O2 affinity of pigeon blood: implications for brain O2 supply

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1985.249.6.r758 ◽

1985 ◽

Vol 249 (6) ◽

pp. R758-R764 ◽

Cited By ~ 1

Author(s):

B. Pinshow ◽

M. H. Bernstein ◽

Z. Arad

Keyword(s):

Heat Exchangers ◽

Venous Return ◽

Brain Temperature ◽

Columba Livia ◽

Co2 Exchange ◽

Arterial Blood ◽

Effects Of Temperature ◽

O2 Supply ◽

The Brain ◽

And Diffusion

Bird heads contain paired countercurrent heat exchangers, the ophthalmic retia, which function in brain temperature regulation. Blood, cooled by evaporation from the nasal and buccal mucosa and the ocular surfaces, flows to the venous side of each rete and there gains heat from arterial blood flowing countercurrent to it. The cooled arterial blood then flows to the brain. To ascertain whether characteristics of the blood reaching the cooling surfaces and the retia favor O2 and CO2 exchange, as well as heat exchange, we studied blood O2 affinity in relation to temperature (T) and CO2 tension (PCO2) in six pigeons (Columba livia). O2 tension (PO2) at half-saturation (P50, Torr) was measured at various combinations of T and PCO2 from 36 to 44 degrees C and 9 to 33 Torr. pH was uncontrolled. O2 half-saturation of hemoglobin (P50) varied according to P50 = 1.049T + 0.573PCO2–19.444. We propose that shifts in blood O2 affinity, associated with T and PCO2 at the mucosa and eyes and in the retia, would enhance the brain O2 supply by an exchange of O2 and CO2 between air and blood at moist cephalic surfaces, thereby augmenting O2 and reducing CO2 in the venous return to the retia and diffusion of O2 from veins to arteries in the retia. This mechanism might have particular importance at high altitude; we calculate that at 7,000 m above sea level both O2 saturation and PO2 could double in blood flowing from the retia to the brain.

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Independence of brain and tympanic temperatures in an unanesthetized human

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.1.482 ◽

1988 ◽

Vol 65 (1) ◽

pp. 482-486 ◽

Cited By ~ 111

Author(s):

K. Shiraki ◽

S. Sagawa ◽

F. Tajima ◽

A. Yokota ◽

M. Hashimoto ◽

...

Keyword(s):

Skin Surface ◽

The Body ◽

Tympanic Temperature ◽

The Face ◽

Series Of Experiments ◽

Long Term Monitoring ◽

The Brain ◽

Term Monitoring ◽

Monitoring Temperature

Temperature within the brain and the esophagus and at the tympanum were obtained in a 12-yr-old male in a series of experiments that began 8 days after surgery for implantation of a drainage catheter. Fanning the face did reduce tympanic temperature but not temperature in the brain; brain temperatures followed esophageal temperatures. In long-term monitoring, temperature in the lateral ventricle was 0.5 degree C above esophageal temperature and 0.2 degree C below that in white matter 1 cm above, with the offsets fixed throughout the overnight cycle. All temperatures went through similar excursions when the face was excluded from fanning applied to the body. These observations highlight the fact that in humans the defense against hyperthermia takes advantage of cooling distributed over the entire skin surface.

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