Can the SpotOn™ Zero-Heat-Flux-Thermometry Sensor Accurately Measure Core Temperature in Children?

Inclusion Criteria: * ASA I \& II * Age: 1d - 16 years * Elective surgery * Minimum anaesthesia time of 30 minutes Exclusion Criteria: * Fragile skin state in the forehead * Know allergy to probe adhesive * Maxillofacial trauma or lesions * Procedures impeding proper use of SpotOn™ sensor (mostly maxillo-facial) * Abnormal oesophageal anatomy/gastroesophageal procedures. * Coagulopathy * Neurologically impaired children with abnormal thermoregulation * Extensive Haemodynamic instability * Need for Vasopression * Procedures associated with extended use of rinsing fluids (abdominal/thoracic lavages) * Thoracoscopic/thoracotomic procedures (oesophageal probe cooling) * Need for use of "over body" forced air warming systems * Malignant Hyperthermia or family history of malignant hyperthermia * Fever / Infectious patient * All conditions that might be judged to alter skin perfusion in an abnormal way * Anatomical variants (overt hydrocephalus …) * Calibration/device failure