Drop In Core Temperature Research Articles

The effect of intraseptally applied vasopressin on thermoregulation in the rat

The thermoregulatory effects of intraseptal injection of arginine vasopressin were studied in eight rats in which a thermode and a bilateral cannula had been chronically implanted into the preoptic area and lateral septa, respectively. Intraseptal injection of vasopressin completely suppressed the increase in heat production and body temperature elicited by cooling the preoptic area, but did not appear to affect vasomotor tone. Vasopressin also inhibited heat production in a cold environment, and thus induced a marked drop in core temperature; skin temperature did not, however, fall as much as core temperature suggesting that some vasodilatation occurred. At an ambient temperature in the upper range of thermoneutrality vasopressin had no effect on the thermoregulatory variables studied. It is concluded that vasopressin does not reduce the normal set point temperature and that its main effect is to inhibit thermoregulatory heat production. This effect may explain its antipyretic action.

Brain stem sites mediating specific and non-specific temperature effects on thermoregulation in the pekin duck.

1. Thermodes were chronically implanted into various levels of the brain stem of sixteen Pekin ducks. The effects of local thermal stimulation on metabolic heat production, core temperature, peripheral skin temperature and respiratory frequency were investigated. 2. Four areas of thermode positions were determined according to the responses observed and were histologically identified at the end of the investigation. 3. Thermal stimulation of the lower mid-brain/upper pontine brain stem (Pos. III) elicited an increase in metabolic heat production, cutaneous vasoconstriction and rises in core temperature in response to cooling at thermoneutral and cold ambient conditions and, further, inhibition of panting by cooling and activation of panting by heating at warm ambient conditions. The metabolic response to cooling this brain stem section amounted to -0.1 W/kg. degrees C as compared with -7 W/kg. degrees C in response to total body cooling. 4. Cooling of the anterior and middle hypothalamus (Pos. II) caused vasodilatation in the skin and did not elicit shivering. The resulting drop in core temperature at a given degree of cooling was greater than the rise in core temperature in response to equivalent cooling of the lower mid-brain/upper pontine brain stem. 5. Cooling of the preoptic forebrain (Pos. I) and of the myelencephalon (Pos. IV) did not elicit thermoregulatory reactions. 6. It is concluded that the duck's brain stem contains thermoreceptive structures in the lower mid-brain/upper pontine section. However, the brain stem as a whole appears to contribute little to cold defence during general hypothermia because of the inhibitory effects originating in the anterior and middle hypothalamus. Cold defence in the duck, which is comparable in strength to that in mammals, has to rely on extracerebral thermosensory structures.

Naloxone response in non-dependent man: Effect on six physiological variables

The response to 1.2 mg naloxone in a testing situation known to precipitate opiate withdrawal in narcotic addicts, has been evaluated in normal, non-dependent human subjects. Six physiological variables known to be sensitive to opiate withdrawal were measured. Naloxone produced a change in three of the variables, pupil diameter, core temperature and systolic blood pressure compared with saline placebo. A slight miosis, increased rate of core temperature drop and reduced blood pressure may be indicative of the fact that naloxone possesses some slight opiate agonist properties; however the interaction of naloxone with endogenous opiate substances cannot be ruled out.

Incremental changes in deer mouse ( Peromyscus maniculatus) core temperatures during behavioral challenges

1. 1. Second generation deer mice bearing temperature-sensitive radiosondes respond by increasing body temperatures incrementally as a result of exposure to novel environments, visual, physical and contact, with opponents during intra-specific tests of aggression. 2. 2. Physical contact with an opponent results in additional increase in core temperature if the opponent is either of nearly equal or lower social rank. 3. 3. Physical contact with a more aggressive opponent does not result in an increase in core temperature over that recorded during visual contact, but is associated with a drop in core temperature of the submissive animal.

Ca 2+ induced hypothermia in a hibernator ( Citellus beechyi)

1. 1. Excess Ca 2+ and Na + were perfused into the preoptic anterior hypothalamus (POAH) and the posterior hypothalamus (PHYPO) of adult, awake ground squirrels, Citellus beechyi, at high (33°C), low (12°C) and neutral (25°C) temperatures. 2. 2. Excess Na + results in a moderate rise of core temperature only when perfused into the PHYPO 3. 3. Excess Ca 2+ results in respiratory and heart rate decreases, partial loss of thermoregulatory control and general depressant effects when perfused into either region. The magnitude of the effects of hypothalamic Ca 2+ perfusion on core temperature are determined by dose, but also by air temperature since Ca 2+ perfusion causes a greater drop in core temperature at lower ambient temperatures and even causes a rise in core temperature at high ambient temperatures. 4. 4. Ca 2+ perfusion into the hypothalamus of ground squirrels apparently causes a non-specific depression of thermoregulatory control and does not determine the “set-point” for thermoregulation.

Brain calcium: role in temperature regulation.

Perfusion of the preoptic-anterior hypothalamus with excess calcium ion in ground squirrels produces a drop in core temperature. The magnitude of the drop is directly dependent on ambient temperature. Respiration, heart rate, and oxygen consumption are also reduced during perfusion of calcium ion. It is concluded that the depression of body temperature during calcium ion perfusion is due to generalized depression of the neurons of the preoptic-anterior hypothalamus.

Responses of Andean highlanders to night cold.

Six adult male Andean highlanders of Quechua descent were tested in night cold exposures (4°C) in both a single-layer blanket bag and native bedding. In the blanket bag exposure the subjects maintained body temperature through increased metabolic heat production. Previous reports of a "hypothermic" response involving a drop of core temperature with minimal increased heat production were not confirmed. When the subjects were exposed to cold using native bedding there was a marked diminution in responses: rectal, skin and mean body temperature were maintained at high levels and heat production was only slightly increased. Simple native bedding in both the laboratory and huts substantially diminishes cold stress and permits sleep in what otherwise would be intolerable conditions.

Comparison of Effects of Propofol and Isosorbide Dinitrate during Rewarming on Cardiopulmonary Bypass.

Objectives:Comparison of effects of propofol and isosorbide dinitrate during rewarming on cardiopulmonary bypass in patients undergoing coronary artery bypasses grafting.Methods:It was randomized prospective clinical trial. One hundred and twenty patient (120) undergoing CABG surgery were included in this study. Group-I (Study group, n=60): in which only propofol infusion used during rewarming and Group-II (control Group, n=60) in which isosorbide dinitrate and propofol infusion combination was used during rewarming. The data was entered and analyzed through SPSS Version 19. Independent sample T-test and chi-square test were used for data analysis. P value of ≤ 0.05 was taken as significant.Results:Mean arterial pressures during rewarming were 63.41±3.61 mmHg in propofol group versus 60.80±4.86 mmHg in control group (p-value 0.001). Core temperature on weaning from cardiopulmonary bypass was 37.11±0.49 °C in propofol group and 37.00±0.18 °C in control group. After drop in core temperature was little more in propofol group (1.02±0.36 °C) versus 0.96±0.37 °C in control group but this difference was not statistically significant (p-value 0.41). Mean Ventilation time after surgery in propofol group was 4.65±0.65 hours versus 5.03±0.81 hours in control group (p-value 0.006).Conclusion:Propofol alone is capable of fulfilling the requirements of adequate rewarming during Cardiopulmonary bypass and can produce more hemodynamic stability and early post-operative recovery.