Decrease In Central Temperature Research Articles

Relationship between perfusion index and central temperature before and after induction of anesthesia in laparoscopic gastrointestinal surgery: A prospective cohort study.

The perfusion index (PI) cutoff value before anesthesia induction and the ratio of PI variation after anesthesia induction remain unclear. This study aimed to clarify the relationship between PI and central temperature during anesthesia induction, and the potential of PI in individualized and effective control of redistribution hypothermia. This prospective observational single center study analyzed 100 gastrointestinal surgeries performed under general anesthesia from August 2021 to February 2022. The PI was measured as peripheral perfusion, and the relationship between central and peripheral temperature values was investigated. Receiver operating characteristic curve analysis was performed to identify baseline PI before anesthesia, which predicts a decrease in central temperature 30 minutes after anesthesia induction, and the rate of change in PI that predicts the decrease in central temperature 60 minutes after anesthesia induction. In cases with a central temperature decrease of ≥ 0.6°C after 30 minutes, the area under the curve was 0.744, Youden index was 0.456, and the cutoff value of baseline PI was 2.30. In cases with a central temperature decrease of ≥ 0.6°C after 60 minutes, the area under curve was 0.857, Youden index was 0.693, and the cutoff value of the PI ratio of variation after 30 minutes of anesthesia induction was 1.58. If the baseline PI is ≤ 2.30 and the PI 30 minutes after anesthesia induction is at least 1.58-fold the PI ratio of variation, there is a high probability of a central temperature decrease of at least 0.6°C within 30 minutes after 2 time points.

An old galaxy group:ChandraX-ray observations of the nearby fossil group NGC 6482

We present the first detailed X-ray observations, using Chandra, of NGC 6482 - the nearest known fossil group. The group is dominated by an optically luminous giant elliptical galaxy and all other known group members are at least two magnitudes fainter. The global X-ray properties (luminosity, temperature, extent) of NGC 6482 fall within the range of other groups, but the detailed properties show interesting differences. We derive the gas temperature and total mass profiles for the central 30 h -1 70 kpc (∼0.1 r 200 ) using ACIS spatially resolved spectroscopy. The unusually high L X /L opt ratio is found to result from a high central gas density. The temperature profile shows a continuous decrease outward, dropping to 0.63 of its central value at 0.1r 200 . The derived total mass profile is strongly centrally peaked, suggesting an early formation epoch. These results support a picture in which fossil groups are old, giving time for the most massive galaxies to have merged (via the effects of dynamical friction) to produce a central giant elliptical galaxy. Although the cooling time within 0.1r 200 is less than a Hubble time, no decrease in central temperature is detected. The entropy of the system lies toward the low side of the distribution seen in poor groups and drops all the way into the centre of the system, reaching very low values. No isentropic core, such as those predicted in simple pre-heating models, is present. Given the lack of any central temperature drop in the system, it seems unlikely that radiative cooling can be invoked to explain this low central entropy. The lack of any signature of central cooling is especially striking in a system that appears to be old and relaxed, and to have a central cooling time ≤10 8 yr. We find that the centrally peaked temperature profile is consistent with a steady-state cooling-flow solution with an accretion rate of 2 M ○. yr -1 , given the large P dV work arising from the cuspy mass profile. However, solutions involving distributed or non-steady heating cannot be ruled out.

Initiation and maintenance of continuous breathing at birth.

Changes in arterial PCO2 (PaCO2) and body temperature normally occurring at the moment of birth may play a role in the initiation and maintenance of continuous breathing. To clarify these mechanisms, five chronically instrumented fetal lambs were connected to an extracorporeal membrane oxygenation (ECMO) system. ECMO was initiated in utero at a flow rate sufficient to support the fetus totally, the umbilical cord was occluded, and the fetuses were delivered into a warm isotonic saline bath. Breathing activity was present periodically before connection to the ECMO system and on ECMO during fetal normocapnia and normoxia. Near delivery there were no breathing movements, because all ewes were in labor. After delivering the fetuses into the warm saline bath, breathing movements remained episodic, being absent during high voltage electrocortical activity, whereas fetal PaCO2 remained constant. However, after 36-192 min, breathing activity became present continuously in all animals, at a time when fetal central temperature decreased. Once initiated, continuous breathing could be stopped by reducing the PaCO2. We conclude that maintenance of fetal PaCO2 and a slow decrease in central temperature after cord occlusion delays the establishment of continuous breathing, and that the level of PaCO2 is important in the maintenance of breathing activity during early postnatal life.

Intraoperative warming therapies: a comparison of three devices

Study Objective: To compare the effectiveness of three commonly used intraoperative warming devices. Design: A randomized, prospective clinical trial. Setting: The surgical suite of a university medical center. Patients: Twenty adult patients undergoing kidney transplantation for end-stage renal disease. Interventions: Patients were assigned to one of four warming therapy groups: circulating-water blanket (40°C), heated humidifier (40°C), forced-air warmer (43°C, blanket covering legs), or control (no extra warming). Intravenous fluids were warmed (37°C), and, fresh gas foes was 5 Llmin for all groups. No passive heat and moisture exchangers were used. Measurements and Main Results: The central temperature (tympanic membrane thermocouple) decreased approximately 1 °c during the first hour of anesthesia in all groups. After three hours r f anesthesia, the decrease in the tympanic membrane temperature from baseline (preinduction) was least in the forced-air warmergroup (−0.5°C ±0.4°C), intermediate in the circulating-water blanket group (−1.2°C ±0.4°C), and greatest in the heated humidifier and control groups (−2.0°C ± 0.5°C and −2.0°C ± 0.7°C, respectively). Total cutaneous heat loss measured with distributed thermal flux transducers was approximately 35W (walls = joules/sec) less in the forced-air warmer group than in the others. Heal gain across the back from the circulating-water blanket was approximately 7W versus a loss of approximately 3W in patients lying on a standard foam mattress. Conclusion: The forced-air- warmer applied to only a limited skin surface area transferred more heat and was clinically more effective (at maintaining central body temperature) than were the other devices. The characteristic early decrease in central temperature observed in all groups regardless of warming therapy is consistent with the theory of anesthetic-induced heat redistribution within the body.

Physiologic Responses to Mild Perianesthetic Hypothermia in Humans

To evaluate physiologic responses to mild perianesthetic hypothermia, we measured tympanic membrane and skin-surface temperatures, peripheral vasoconstriction, thermal comfort, and muscular activity in nine healthy male volunteers. Each volunteer participated on three separate days: 1) normothermic isoflurane anesthesia; 2) hypothermic isoflurane anesthesia (1.5 degrees C decrease in central temperature); and 3) hypothermia alone (1.5 degrees C decrease in central temperature) induced by iced saline infusion. Involuntary postanesthetic muscular activity was considered thermoregulatory when preceded by central hypothermia and peripheral cutaneous vasoconstriction. Tremor was considered normal shivering when electromyographic patterns matched those produced by cold exposure in unanesthetized individuals. During postanesthetic recovery, central temperatures in hypothermic volunteers increased rapidly when residual end-tidal isoflurane concentrations were less than or equal to 0.3% but remained 0.5 degree C less than control values throughout 2 h of recovery. All volunteers were vasodilated during isoflurane administration. Peripheral vasoconstriction occurred only during recovery from hypothermic anesthesia, at end-tidal isoflurane concentrations of less than approximately 0.4%. Spontaneous tremor was always preceded by central hypothermia and peripheral vasoconstriction, indicating that muscular activity was thermoregulatory. Maximum tremor intensity during recovery from hypothermic anesthesia occurred when residual end-tidal isoflurane concentrations were less than or equal to 0.4%. Three patterns of postanesthetic muscular activity were identified. The first was a tonic stiffening that occurred in some normothermic and hypothermic volunteers when end-tidal isoflurane concentrations were approximately 0.4-0.2%. This activity appeared to be largely a direct, non-temperature-dependent effect of isoflurane anesthesia. In conjunction with lower residual anesthetic concentrations, stiffening was followed by a synchronous, tonic waxing-and-waning pattern and spontaneous electromyographic clonus, both of which were thermoregulatory. Tonic waxing-and-waning was by far the most common pattern and resembled that produced by cold-induced shivering in unanesthetized volunteers; it appears to be thermoregulatory shivering triggered by hypothermia. Spontaneous clonus resembled flexion-induced clonus and pathologic clonus and did not occur during hypothermia alone; it may represent abnormal shivering or an anesthetic-induced modification of normal shivering. We conclude that among the three patterns of muscular activity, only the synchronous, tonic waxing-and-waning pattern can be attributed to normal thermoregulatory shivering.

Response of dogs' cutaneous veins to local and central temperature changes.

To study the separate actions of peripheral and central temperature-sensitive systems on the cutaneous veins of the dog, a cross-circulation preparation was made in which hindleg and central temperatures could be varied independently. The lateral saphenous vein of a vascularly isolated hindleg was cross-perfused at constant flow; the difference between perfusion and femoral vein pressures was a measure of venomotor activity. With central temperature constant, local cooling of one leg from 47° to 17°C caused the lateral saphenous vein to constrict; sensitivity to cooling was maximal between 42° and 27°C. With leg temperature constant, central cooling caused the lateral saphenous vein to constrict; over the range of 40° to 33°C, the constriction was linearly related to the decrease in temperature. Central heating reduced the response to local cooling, whereas central cooling had the opposite effect. Thus a decrease in central temperature from 38° to 34°C increased the venoconstrictor response to local cooling from 42° to 22°C by a factor of ten or more.