Abstract

High perianesthetic mortality rates have been identified in pinniped species,¹ highlighting the importance of comprehensive anesthetic monitoring to ensure sufficient oxygen delivery to vital organs, including the brain. Near-infrared spectroscopy (NiRS) is an indirect monitoring tool used to assess regional cerebral perfusion (rSO₂) in humans and veterinary species.² The objective of this study was to evaluate NiRS to assess cerebral perfusion in South American fur seals (SAFS, Arctocephalus australis) and South American sea lions (SASL, Otaria flavescens). Free-ranging, adult, male SAFS and female SASL were immobilized with intramuscular butorphanol, medetomidine, and midazolam delivered via dart using previously described methods.³ Animals were intubated and manually ventilated using a bag valve mask (FiO₂ 21%) [SASL] or demand valve (FiO₂ 100%) [SAFS] to a target ETCO₂ of 35–45 mm Hg. Anesthetic monitors included a capnograph, pulse oximeter, rectal temperature probe, and two cerebral NiRS probes (one on the dorsal cranium and one on the dorsal nasopharynx). Paired arterial (radial, median) and venous (jugular) blood samples were collected for blood gas analysis and calculation of arteriovenous oxygen saturation (S_avO₂) using a human validation algorithm.⁴ Concurrent NiRS values (rSO₂) were recorded. rSO₂ values were consistent between both probe placement sites (cranium, nasopharynx) and, compared to calculated S_avO₂, rSO₂ consistently underestimated regional cerebral perfusion. Near-infrared spectroscopy may be used to monitor trends in rSO₂ during pinniped anesthesia and is suitable for use in a field setting.

Acknowledgements

Research was approved by Peru's Ministry of the Environment under permit 019-2016-SERNANP-RNSIIPG. Access to the Punta San Juan Protected Area was authorized under permit 298-2016-SERNANP-RNSIIPG. The authors thank Susana Cárdenas-Alayza, Maria Jose Ganoza, Marco Cardeña, Paulo Colchao, Matt Allender, and Ashlee Webb for their assistance. We further thank the Chicago Board of Trade Endangered Species Fund, Paul M. Angell Family Foundation, and Grainger Foundation for their financial support of this project.

* Presenting author
+ Student presenter

Literature Cited

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