The acute hypoxic ventilatory response under halothane,isoflurane, and sevoflurane anaesthesia in rats* |
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| Authors: | N Karanovic R Pecotic M Valic A Jeroncic M Carev S Karanovic A Ujevic Z Dogas |
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| Institution: | 1. Staff Anaesthesiologist & Assistant Professor;2. Assistant Professor;3. Associate Professor;4. Research Assistant, Departments of Neuroscience and Scientific Methodology, School of Medicine, and Faculty of Science, University of Split, Split, Croatia;5. Intern, University Hospital Zagreb, Zagreb, Croatia;6. Head of Department, Department of Anaesthesiology and Intensive Care, University Hospital Split, Split, Croatia;7. Vice‐Dean, Professor & Head of Department, Department of Neuroscience, University of Split School of Medicine, Split, Croatia |
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| Abstract: | The relative order of potency of anaesthetic agents on the hypoxic ventilatory response has been tested in humans, but animal data are sparse. We examined the effects of 1.4, 1.6, 1.8, and 2.0 MAC halothane, isoflurane, and sevoflurane on phrenic nerve activity in euoxia (baseline) and during acute normocapnic hypoxia (inspired oxygen fraction 0.09) in adult male Sprague‐Dawley rats. With halothane, all animals became apnoeic even in euoxia, and the hypoxic response was completely abolished at all anaesthetic levels. With isoflurane, 5 of 14 animals exhibited phrenic nerve activity in euoxia at 1.4 MAC and demonstrated a hypoxic response (302% of baseline activity), but all became apnoeic and lost the hypoxic response at higher doses. With sevoflurane, phrenic nerve activity and a hypoxic response was preserved in at least some animals at all doses (i.e. even the highest dose of 2.0 MAC). Similar to the rank order of potency previously observed in humans, the relative order of potency of depression of the hypoxic ventilatory response in rats was halothane (most depressive) > isoflurane > sevoflurane (p = 0.01 for differences between agents). |
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