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Macgregor JW, Holyoake C, Fleming PA, et al. Investigation into the characteristics, triggers and mechanism of apnoea and bradycardia in the anaesthetized platypus (Ornithorhynchus anatinus). Conserv Physiol. 2014;2(1):cou053doi: 10.1093/conphys/cou053.
Macgregor, J. W., Holyoake, C., Fleming, P. A., Robertson, I. D., Connolly, J. H., & Warren, K. S. (2014). Investigation into the characteristics, triggers and mechanism of apnoea and bradycardia in the anaesthetized platypus (Ornithorhynchus anatinus). Conservation physiology, 2(1), cou053. https://doi.org/10.1093/conphys/cou053
Macgregor, J W, et al. "Investigation into the characteristics, triggers and mechanism of apnoea and bradycardia in the anaesthetized platypus (Ornithorhynchus anatinus)." Conservation physiology vol. 2,1 (2014): cou053. doi: https://doi.org/10.1093/conphys/cou053
Macgregor JW, Holyoake C, Fleming PA, Robertson ID, Connolly JH, Warren KS. Investigation into the characteristics, triggers and mechanism of apnoea and bradycardia in the anaesthetized platypus (Ornithorhynchus anatinus). Conserv Physiol. 2014 Dec 05;2(1):cou053. doi: 10.1093/conphys/cou053. eCollection 2014. PMID: 27293674; PMCID: PMC4732481.
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Conserv Physiol. 2014 Dec 05;2(1):cou053. doi: 10.1093/conphys/cou053. eCollection 2014.

Investigation into the characteristics, triggers and mechanism of apnoea and bradycardia in the anaesthetized platypus (Ornithorhynchus anatinus).

Conservation physiology

J W Macgregor, C Holyoake, P A Fleming, I D Robertson, J H Connolly, K S Warren

Affiliations

  1. College of Veterinary Medicine , School of Veterinary and Life Sciences, Murdoch University , 90 South Street, Murdoch, WA 6150 , Australia.
  2. Environmental and Conservation Sciences , School of Veterinary and Life Sciences, Murdoch University , 90 South Street, Murdoch, WA 6150 , Australia.
  3. School of Animal and Veterinary Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia; Graham Centre for Agricultural Innovation, Locked Bag 588, Wagga Wagga, NSW 2678, Australia.

PMID: 27293674 PMCID: PMC4732481 DOI: 10.1093/conphys/cou053

Abstract

Health and conservation research on platypuses (Ornithorhynchus anatinus) may require anaesthesia to reduce stress and the risk of injury to both the animal and the researcher, as well as to facilitate examination and sample collection. Platypus anaesthesia can be difficult to manage, with reports of periods of apnoea and bradycardia described. This study investigated the conditions around sudden-onset apnoea and bradycardia in 163 field-anaesthetized platypuses as part of a health study. Anaesthesia was induced and maintained using isoflurane delivered in oxygen by face mask. Sudden-onset apnoea and bradycardia was observed in 19% of platypuses, occurring either at induction of anaesthesia, during recovery, or both. At induction, occurrence was more often recorded for adults (P = 0.19) and was correlated with low body temperature (P < 0.001), season (P = 0.06; greater incidence in summer) and longer pre-anaesthetic holding time (P = 0.16). At recovery, sudden-onset apnoea and bradycardia occurred only in platypuses that had been placed in dorsal recumbency as part of their examination, and correlated with poor body condition (P = 0.002), time in dorsal recumbency (P = 0.005), adults (P = 0.06), number of fieldworkers (P = 0.06) and females (P = 0.11). The sudden-onset apnoea and bradycardia we observed is likely to result from the irritant nature of isoflurane (stimulating the trigeminal nerve via nasal chemoreceptors). We propose that this mechanism is analogous to that of submersion of the face/nasal cavity in cold water during a natural dive response, but that the term 'nasopharyngeal response' would more appropriately describe the changes observed under isoflurane anaesthesia. Although we did not record any long-term adverse effects on platypuses that had undergone this response, the nasopharyngeal response could complicate the diagnosis of anaesthetic dose-dependent apnoea and bradycardia. Therefore, we suggest that these responses during anaesthesia of platypuses might be avoided by minimizing the stress around capture and handling, as well as reducing the time in dorsal recumbency.

Keywords: Apnoea; Ornithorhynchus anatinus; bradycardia; dive response; isoflurane; nasopharyngeal response; platypus

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