- Skin temperature (forehead): Normally 3°F to 4°F below core temperature. The gradient can increase with further cooling
- Axilla: Common site for noninvasive temperature determination and is usually 1°F below body temperature. The probe needs be placed at the axillary artery with the arm adducted.
- Tympanic membrane: Correlates well with core temperature. Intervening cerumen may enlarge the gradient with respect to core temperature.
- Rectal: Changes in temperature can lag behind those of core body temperature. This phenomenon is often noted during rewarming.
- Nasopharyngeal: Measured at the posterior nasopharynx and reflects the brain temperature. Can be associated with epistaxis in coagulopathic or pregnant patients. Discouraged in patients with head trauma or cerebrospinal fluid rhinorrhea.
- Esophageal: Reflects the core temperature well. Probe should be located at the lower third of the esophagus.
- Blood: Can be obtained with the thermistor of a pulmonary artery catheter (PAC).
**Source: Clinical Anesthesia Procedures of the Massachusetts General Hospital (2010)