Delivery of sevoflurane to dogs using a Stephens anaesthetic machine

Ferguson, Andrew J., Filippich, Lucio J . and Keates, Helen L. (2014) Delivery of sevoflurane to dogs using a Stephens anaesthetic machine. Veterinary Anaesthesia and Analgesia, 41 1: 54-63. doi:10.1111/vaa.12087

Author Ferguson, Andrew J.
Filippich, Lucio J .
Keates, Helen L.
Title Delivery of sevoflurane to dogs using a Stephens anaesthetic machine
Journal name Veterinary Anaesthesia and Analgesia   Check publisher's open access policy
ISSN 1467-2987
Publication date 2014-01-01
Year available 2013
Sub-type Article (original research)
DOI 10.1111/vaa.12087
Volume 41
Issue 1
Start page 54
End page 63
Total pages 10
Place of publication Chichester, West Sussex, United Kingdom
Publisher Wiley-Blackwell
Language eng
Formatted abstract
Objective: To investigate the sevoflurane concentrations produced within the Stephens anaesthetic machine circuit (vaporizer in-circle system) at different fresh gas flow rates (FGFRs), temperatures, vaporizer settings and vaporizer sleeve positions when used to anaesthetize dogs of different body sizes.

Study design: Experimental non-blinded studies. Animals: Eighteen mixed breed dogs, weights 4-39 kg.

Methods: Anaesthetic induction with propofol was followed by maintenance with sevoflurane in oxygen via the Stephens anaesthetic machine. In study 1, the vaporizer setting, temperature and circuit FGFRs were altered with the vaporizer sleeve down (n = 3), or in separate experiments, up (n = 3). Delivered (Fi′SEVO) and expired sevoflurane concentrations were recorded. Study 2 determined the vaporizer settings (sleeve up) required to achieve predetermined multiples of minimal alveolar concentration (MAC) of Fi′SEVO when sevoflurane was delivered to dogs (n = 12) of different bodyweights and at different FGFRs.

Results: Delivered concentrations of sevoflurane were sufficient to maintain anaesthesia in all dogs, regardless of bodyweight, FGFR, vaporizer temperature and sleeve position. Fi′SEVO increased with increasing temperature, when the vaporizer sleeve was down, when vaporizer setting was increased and when FGFR was decreased. As the FGFR increased or the dog's bodyweight decreased, higher vaporizer settings were required to produce the same Fi′SEVO. The median Stephens vaporizer settings to achieve an Fi′SEVO of 1.3 MAC ranged from 4.3 to 5.0 for a small dog (1-10 kg), 2.5 to 5.6 for a medium dog (15-25 kg) and 2.5 to 3.5 for a large dog (30-40 kg), depending on the FGFR.

Conclusion and clinical relevance: The Stephens anaesthetic machine can deliver to dogs, weighing 4 kg and above, concentrations of sevoflurane sufficient or in excess of that required to maintain anaesthesia, at temperatures from 10 to 35 °C, FGFRs of 1 to 5 times the patient's estimated metabolic oxygen requirement and at any vaporizer sleeve position.
Keyword Anaesthesia
Respiratory minute volume
Stephens anaesthetic machine
Vaporizer in-circle
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Official 2014 Collection
School of Veterinary Science Publications
Version Filter Type
Citation counts: TR Web of Science Citation Count  Cited 0 times in Thomson Reuters Web of Science Article
Scopus Citation Count Cited 1 times in Scopus Article | Citations
Google Scholar Search Google Scholar
Created: Tue, 07 Jan 2014, 10:19:38 EST by System User on behalf of School of Veterinary Science