Knowledge of core temperature confirms the diagnosis, directs future therapy and assesses the effectiveness of re-warming. Skin surface temperature measurement is of no use. Different sites of measurement may give different temperature readings and imply differing rates of re-warming – so it is sensible to select one site and use it consistently.
Rectal temperatures may demonstrate a lag during the re-warming phase of several degrees, which may lead to escalation of care when simpler re-warming strategies are in fact working . Rectal temperatures can also be unreliable if there is faecal loading. Tympanic thermometers are usually accurate down to about 20°C but cannot provide continuous measurement. For these reasons, oesophageal or vascular temperature probes are recommended .