DO TEMPERATURES RECORDED AT STANDARD MONITORING SITES REFLECT ACTUAL BRAIN TEMPERATURE DURING DEEP HYPOTHERMIA?

Temperature measurement

For many decades the measurement of body core temperature has been ubiquitously established in medical and non-medical applications, e.g., in hospitals, occupational medicine, sports medicine, military and other settings. However, there are still numerous challenges, such as the precise definition of the body core temperature, establishing the clinical importance of the measured temperature and the lack of a reliable, non-invasive and fast measurement method for body core temperature. After an introduction to the topic, the medical aspects from a user point of view are presented, i.e., the needs for temperature measurements, as well as possible measurement sites and clinical specifications and needs are highlighted. Subsequently, technical methods are presented which are used for temperature measurement. The analysis of the technical methods is divided into two sections: the first deals with the standard methods, which are currently used and the second describes methods, which are currently under development. Although temperature measurement appears very easy and is very common in daily use, it has many constraints, which are considered later. The need for further research is deduced from the above-mentioned sections and is finally followed by the conclusions section.

Monitoring and thermal management

Anaesthesia alters normal thermoregulatory control of the body, usually leading to perioperative hypothermia. Hypothermia is associated with a large number of serious complications. To assess perianaesthetic hypothermia, core temperature should be monitored vigorously. Pulmonary artery, tympanic membrane, distal oesophageal or nasopharyngeal temperatures reflect core temperature reliably. Core temperatures can be often estimated with reasonable accuracy using oral, axillary and bladder temperatures, except during extreme thermal perturbations. The body site for measurements should be chosen according to the surgical procedure. Unless hypothermia is specifically indicated, efforts should be made to maintain intraoperative core temperatures above 36 degrees C. Forced air is the most effective, commonly available, non-invasive warming method. Resistive heating electrical blankets and circulating water garment systems are an equally effective alternative. Intravenous fluid warming is also helpful when large volumes are required. In some patients, induction of mild therapeutic hypothermia may become an issue for the future. Recent studies indicate that patients suffering from neurological disease may profit from rapid core cooling.