title: Exploring alternative routes for oxygen administration.
abstract: BACKGROUND
  Hypoxemia may compromise cell metabolism and organ function. Supplemental oxygen (O2) at high concentrations may prove ineffective, and issues relating to hyperoxia, barotrauma, mechanical ventilation, and extracorporeal oxygenation are well documented. Old reports suggest the potential safety and efficacy of alternative routes for O2administration, such as intravenous or intestinal. We re-explored these routes in rat models of hypoxemia.
  
  
  METHODS
  Hypoxemia was induced in spontaneously breathing, anesthetized rats by breathing a hypoxic gas mix (FiO20.1). Pilot studies infusing pure O2gas caused early death, likely due to pulmonary embolism. Instead, rats (n = 6/group) were given intravenous O2via a continuous infusion of pre-oxygenated Hartmann's solution (10 ml/kg/h) for 3 h with normal Ringer's lactate used in control animals. In separate experiments (n = 8/group), bowel intraluminal oxygenation was assessed with pure O2administered through a cannula placed into the jejunal lumen at a dose of a 15 ml/kg bolus followed by a continuous infusion of 50 ml/kg/h; no treatment was given to controls. Echocardiography, arterial blood gas analysis, mean arterial pressure, muscle and liver tPO2, muscle microvascular perfused vessel density, and urine output were measured.
  
  
  RESULTS
  Administration of oxygenated Hartmann's solution (PO2of solution at end-experiment = 87.5 ± 1.7 kPa) was safe but did not increase either systemic or tissue oxygenation. Similarly, the administration of bowel O2was safe but did not improve neither systemic nor liver oxygenation.
  
  
  CONCLUSIONS
  In this rat model of hypoxemia, the intravenous infusion of gaseous O2was unfeasible as it induced early mortality. Although safe, both intravenous infusion of oxygenated Hartmann's solution and bowel O2administration were unable to improve arterial or tissue oxygenation.
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, via Tronto 10/A, 60126, Torrette di Ancona, Italy. eli.dam86@alice.it.|Bloomsbury Institute of Intensive Care Medicine, Division of Medicine, University College London, London, UK. eli.dam86@alice.it.
authors.forename: Elisa
authors.identifier: http://orcid.org/0000-0002-3166-1835
authors.initials: E
authors.lastname: Damiani
authors.affiliation: Bloomsbury Institute of Intensive Care Medicine, Division of Medicine, University College London, London, UK.
authors.forename: Alex
authors.initials: A
authors.lastname: Dyson
authors.affiliation: Bloomsbury Institute of Intensive Care Medicine, Division of Medicine, University College London, London, UK.|Department of Anesthesiology and Intensive Care, Fondazione IRCCS, Cà-Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Zacchetti
authors.affiliation: Anesthesia and Intensive Care Unit, Department of Biomedical Sciences and Public Health, Università Politecnica delle Marche, via Tronto 10/A, 60126, Torrette di Ancona, Italy.
authors.forename: Abele
authors.initials: A
authors.lastname: Donati
authors.affiliation: Bloomsbury Institute of Intensive Care Medicine, Division of Medicine, University College London, London, UK.
authors.forename: Mervyn
authors.initials: M
authors.lastname: Singer
keywords: Hypoxemia; Oxygen therapy; Tissue oxygenation