5/19/2023 0 Comments Aural temperature definitionAs normally used, i.e. , directed into the aural canal 15or near the temporal artery, 16infrared systems are insufficiently accurate for clinical use ( fig. 13,14However, nearly all available systems are intentionally too large to even fit more than a few millimeters into the aural canal and do not “see” anywhere near the tympanic membrane. When infrared signals are actually obtained from the tympanic membrane, the result is core temperature. Clinical models can measure temperature of the skin surface to within a 10th of a degree or so. These thermometers are accurate and relatively inexpensive. They can consequently be used without actually touching the surface in question (which is useful for measuring the temperature of molten lava or metals, for example). They work by evaluating infrared energy that is emitted by all surfaces above absolute zero degrees. Infrared sensors are another type of thermometer that has become popular in the past decade. Prolonged epidural analgesia is associated with hyperthermia whose cause remains unknown. Neuraxial anesthesia also impairs thermoregulatory control, although to a lesser extent than does general anesthesia. Anesthetic-induced impairment of normal thermoregulatory control, with the resulting core-to-peripheral redistribution of body heat, is the primary cause of hypothermia in most patients. All general anesthetics produce a profound dose-dependent reduction in the core temperature, triggering cold defenses, including arteriovenous shunt vasoconstriction and shivering. Core body temperature is normally tightly regulated. Body temperature should be measured in patients undergoing general anesthesia exceeding 30 min in duration and in patients undergoing major operations during neuraxial anesthesia. Nonetheless, temperature can be reliably measured in most patients. The difficulty is that no reliably core-temperature-measuring sites are completely noninvasive and easy to use-especially in patients not undergoing general anesthesia. Most clinically available thermometers accurately report the temperature of whatever tissue is being measured.
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