High-inspired oxygen concentration further impairs opioid-induced respiratory depression

Abstract

BackgroundHyperoxaemia depresses the output of peripheral and central chemoreceptors. Patients treated with opioids often receive supplemental oxygen to avert possible decreases in oxygen saturation (). We examined the effect of a single dose of remifentanil in healthy volunteers inhaling room air vs air enriched with 50% oxygen.MethodsTwenty healthy volunteers received i.v. 50 μg remifentanil (infused over 60 s) at anormoxic (N) or hyperoxic (0.5, H) background on separate occasions. Minute ventilation (Vi), respiratory rate (RR), end-tidal Pco2, and were collected on a breath-to-breath basis. The occurrence of apnoea was recorded.ResultsDuring normoxia, remifentanil decreased Vi from 7.4 (1.3) [mean (sd)] to 2.2 (1.2) litre min-1 (P<0.01), and during hyperoxia from 7.9 (1.0) to 1.2 (1.2) litre min -1 (P<0.01; H vs N: P<0.001). RR decreased from 13.1 (2.9) to 6.1 (2.8) bpm during N (P<0.01) and from 13.2 (3.0) to 3.6 (4.0) bpm during H (P<0.01; H vs N: P<0.01). During normoxia, decreased from 98.4 (1.5) to 88.6 (6.7)% (P<0.01), while during hyperoxia, changed from 99.7 (0.7) to 98.7 (1.0)% (P<0.001). Apnoea developed in two subjects during normoxia and 10 during hyperoxia.ConclusionsRespiratory depression from remifentanil is more pronounced in hyperoxia than normoxia as determined from minute ventilation, end-tidal Pco2, and RR. During hyperoxia, respiratory depression may be masked when measuring as pulse oximetry remains in normal values during the first minutes of respiratory depression. © 2013 Author.