Hypoventilation following oxygen administration associated with alfaxalone–dexmedetomidine–midazolam anesthesia in New Zealand White rabbits |
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| Institution: | 1. Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, QC, Canada;2. Groupe de recherché en pharmacologie animale du Québec (GREPAQ), Université de Montréal, Saint-Hyacinthe, QC, Canada;3. Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada;1. Department of Companion Animal Clinical Studies, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa;2. Anaesthesia and Critical Care Services, Valley Farm Animal Hospital, Pretoria, South Africa;3. Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa;4. Optivet Referrals, Havant, Hampshire, United Kingdom;5. Clinical Sciences Department, Ross University School of Veterinary Medicine, Basseterre, Saint Kitts and Nevis;1. Health Sciences Centre, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada;2. Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada;1. Department of Veterinary Clinical Sciences, College of Veterinary Medicine, University of Minnesota, St Paul, MN, USA;2. Veterinary Medical Center, College of Veterinary Medicine, University of Minnesota, St Paul, MN, USA;1. Department of Veterinary Anesthesiology and Critical Care, Ecole Nationale Vétérinaire d''Alfort, Paris, France;2. Department of Clinical Sciences and Services, Royal Veterinary College, Hatfield, UK;1. Centre Vétérinaire Daubigny, Québec, QC, Canada;2. Department of Clinical Sciences, Faculté de médecine vétérinaire, Université de Montréal, Saint-Hyacinthe, QC, Canada;3. Foundation for Veterinary Aid International, St-Charles-sur-le-Richelieu, QC, Canada |
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| Abstract: | ObjectiveTo investigate the relationship between oxygen administration and ventilation in rabbits administered intramuscular alfaxalone–dexmedetomidine–midazolam.Study designProspective, randomized, blinded study.AnimalsA total of 25 New Zealand White rabbits, weighing 3.1–5.9 kg and aged 1 year.MethodsRabbits were anesthetized with intramuscular alfaxalone (4 mg kg–1), dexmedetomidine (0.1 mg kg–1) and midazolam (0.2 mg kg–1) and randomized to wait 5 (n = 8) or 10 (n = 8) minutes between drug injection and oxygen (100%) administration (facemask, 1 L minute–1). A control group (n = 9) was administered medical air 10 minutes after drug injection. Immediately before (PREoxy/air5/10) and 2 minutes after oxygen or medical air (POSToxy/air5/10), respiratory rate (fR), pH, PaCO2, PaO2, bicarbonate and base excess were recorded by an investigator blinded to treatment allocation. Data median (range)] were analyzed with Wilcoxon, Mann–Whitney U and Kruskal–Wallis tests and p < 0.05 considered significant.ResultsHypoxemia (PaO2 < 88 mmHg, 11.7 kPa) was observed at all PRE times: PREoxy5 71 (61–81) mmHg, 9.5 (8.1–10.8) kPa], PREoxy10 58 (36–80) mmHg, 7.7 (4.8–10.7) kPa] and PREair10 48 (32–64) mmHg, 6.4 (4.3–8.5) kPa]. Hypoxemia persisted when breathing air: POSTair10 49 (33–66) mmHg, 6.5 (4.4–8.8) kPa]. Oxygen administration corrected hypoxemia but was associated with decreased fR (>70%; p = 0.016, both groups) and hypercapnia (p = 0.016, both groups). Two rabbits (one per oxygen treatment group) were apneic (no thoracic movements for 2.0–2.5 minutes) following oxygen administration. fR was unchanged when breathing air (p = 0.5). PaCO2 was higher when breathing oxygen than air (p < 0.001).Conclusions and clinical relevanceEarly oxygen administration resolved anesthesia-induced hypoxemia; however, fR decreased and PaCO2 increased indicating that hypoxemic respiratory drive is an important contributor to ventilation using the studied drug combination. |
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| Keywords: | blood gas hypoventilation hypoxemia hypoxic respiratory drive rabbit |
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