Oxygen Reserve Index for Kids (ORIkids)

In infants less than two years old the new Oxygen Reserve Index (ORI) will be measured during general anaesthesia. It will evaluated if and how ORI-monitoring gives earlier warning of hypoxaemia than conventional oxygen saturation measurement.

The Oxygen Reserve Index (ORI) is a new development in multiple wavelength pulse oximetry, reflecting the arterial partial oxygen pressure (PaO2) continuously and non-invasively by an index. In contrast to established standard oxygen saturation (SpO2) measurements, ORI detects a drop of PaO2 until the threshold of 100 mmHg. During anaesthesia induction-associated apnoeic periods ORI may detect a drop of PaO2 early enough for the anaesthesiologist to interrupt the intubation procedure and re-start oxygenation. In contrast, due to the flat upper part of the oxyhaemoglobin dissociation curve, SpO2 stays at values above 90% until PaO2 falls below 60mmHg. At this point, SpO2 drops rapidly and a pro- longed hypoxic dip is the consequence. To avoid this potentially harmful hypoxic dip, continuous monitoring of PaO2 using ORI would be advantageous during anaesthesia induction phase. This clinical study aims to evaluate the time benefit between alarm of hypoxaemia by the ORI-monitoring and the start of the dropping of oxygen saturation. Pre-set and pre-described ORI-alarms will be checked for their utility and a new ORI-alarm will be defined that is potentially more useful. As secondary endpoints the study examines the correlation of ORI with PO2, the influence of patient or measurement characteristics on the correlation of ORI with PO2 and the influence of the measurement site on ORI-measurement.

In this arm ORI measurement is done from the beginning of the induction of anaesthesia until the end of the induction of anaesthesia or until the end of the stay in the operating theatre. The measurement to ORI is done by the "Radical-97" device by Masimo®

ORI measurement is done from the beginning of the induction of anaesthesia until the end of the induction of anaesthesia or until the end of the stay in the operating theatre. The measurement to ORI is done by the "Radical-97" device by Masimo®.

Additionally a potential better definition of ORI-alarm than the preset or previously reported ORI-alarm will be defined

influence of measurement site on the correlation or ORI with PO2 and the influence of the measurement site on ORI measurement

Inclusion Criteria: small infants < 2 years scheduled for elective surgery with general anaesthesia. Exclusion Criteria: emergency procedures, lack of informed consent of legal guardian