Minerva Anestesiologica 2020 Dec 15

DOI: 10.23736/S0375-9393.20.14895-8

Copyright © 2020 EDIZIONI MINERVA MEDICA

language: English

The Oxygen Reserve Index as a determinant of the necessary amount of postoperative supplemental oxygen

Motoi KUMAGAI ¹ ✉, Hiroto KURIHARA ¹, Kazushige ISHIDA ², Hideaki KOMATSU ², Kenji SUZUKI ¹

¹ Department of Anaesthesiology, School of Medicine, Iwate Medical University Hospital, Yahaba-cho, Japan; ² Department of Surgery, School of Medicine, Iwate Medical University Hospital, Yahabacho, Japan

BACKGROUND: Although blood gas analysis (BGA) is important for supplemental oxygen titration, it is invasive, intermittent, costly, and burdensome for staff. We assessed whether the Oxygen Reserve Index (ORi™), a novel pulse oximeter-based index that reflects the partial pressure of oxygen (PaO2), could determine the amount of postoperative supplemental oxygen. We also evaluated the extent of hyperoxia and hypoxia.
METHODS: Fifty patients scheduled to undergo breast surgery were randomly assigned to receive ORi-based oxygen (group O) or conventional postoperative oxygen (group C) treatments. Postoperatively, patients were transported to the post-anesthesia care unit (PACU) and then to general wards. In group O, oxygen was administered at 4 L·min-1 in the operation room after extubation and was decreased if the ORi was >0.00 until a continuous index of 0.00 was achieved for 30 min in the PACU and wards. In group C, oxygen was administered at 4 L·min-1 throughout the evaluation period. BGA was performed 1 h after anesthesia induction (T0), after extubation (T1), before PACU exit (T2), and on the first postoperative morning (T3). Percutaneous oxygen saturation was measured every 2 seconds from 9 PM after surgery to 6 AM the next morning.
RESULTS: The supplemental oxygen amount and PaO2 were significantly lower in group O than group C at T2 (1.5 [0.5-3.0] vs 4.0 [4.0-4.0] l/min, 117.3 (26.8) vs 170.0 (42.8) mmHg) and T3 (1.0 [0.5-3.0] vs 4.0 [4.0-4.0] l/min, 107.5 (16.5) vs 157.1 (28.4) mmHg; median [interquartile ranges] and mean (1 SD); P<0.01). No patient exhibited hypoxia.
CONCLUSIONS: Based on our results, ORi might be useful to titrate postoperative oxygen supplementation.

KEY WORDS: Oxygen Reserve index; Postoperative supplemental oxygen; Oxygen titration; Hypoxia; Hyperoxia