Desaturation times between dogs preoxygenated via face mask or flow-by technique before induction of anesthesia
Ambros B, Carrozzo MV, Jones T
Veterinary Anaesthesia and Analgesia (2018), doi: 10.1016/j.vaa.2018.03.004.
What did the research find?
This study evaluates the effectiveness of two methods of preoxygenation in healthy yet sedated dogs and the impact of these methods on time taken to reach a predetermined haemoglobin desaturation point (haemoglobin saturation (SpO2) of 90%) during an experimentally induced period of apnoea. The study found time to desaturation was significantly longer after mask preoxygenation compared with flow-by (187 ± 67 versus 66 ± 17 seconds respectively).
How was it conducted?
Six healthy dogs were anaesthetised twice a minimum of 14 days apart. Dogs were sedated and a catheter inserted into the tracheal lumen and advanced to the level of the thoracic inlet to allow gaseous sampling. Pre-oxygenation was performed via a closely fitting face mask or flow by (with the end of the circuits y-piece a fixed distance of 2.5cm from the nares).
Preoxygenation was performed for a period of 3 minutes in each case. Propofol was used to induce anaesthesia and apnoea.
Inspired and end-tidal oxygen levels were measured prior to pre-oxygenation and immediately before induction. Arterial blood samples and SpO2 readings were attained until the desaturation point was reached. At this point intubation and manual ventilation was performed. All dogs used in this investigation recovered fully and without any complications.
Why is this study important?
Face mask preoxygenation before induction of anaesthesia is effective to delay the onset of desaturation during apnoea and is recommended for use in dogs (McNally et al. 2009). However, an animal may be intolerant of the face mask, manifesting anxiety and physical struggling which may increase oxygen consumption and decrease the effectiveness of preoxygenation (Galosy et al. 2009). Flow-by administration of oxygen is a less stressful method of pre-oxygenation although the distance of the oxygen source from the patients nose may limit the effectiveness of this method.
No publications comparing flow-by and face mask administration of oxygen in dogs were found in a search of the literature.
Although further research investigating the efficacy of different flow-by techniques is warranted, in this study preoxygenation with a face mask was found to be significantly more effective in increasing time to desaturation than the flow-by technique.
Link to the full article: https://www.sciencedirect.com/science/article/pii/S146729871830059X
Originally published: Thursday, 10th May 2018
Last updated: Tuesday, 15th May 2018
Galosy, R.A., Clarke, L.K. and Mitchell, J.H. 1979. Cardiac changes during behavioural stress in dogs. American Journal of Physiology-Heart and Circulatory Physiology. 236(5): H750-H758.
McNally, E.M., Robertson, S.A. and Pablo, L.S. 2009. Comparison of time to desaturation between preoxygenated and nonpreoxygenated dogs following sedation with acepromazine maleate and morphine and induction of anesthesia with propofol. American journal of veterinary research. 70(11): 1333-1338.
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