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Frequency of hypotension in a historical cohort of anaesthetised dogs undergoing elective desexing

Costa, R.S., Raisis, A., Musk, G.C. and Hosgood, G. (2013) Frequency of hypotension in a historical cohort of anaesthetised dogs undergoing elective desexing. Australian Veterinary Practitioner, 43 (2). pp. 414-419.

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The aim of this study was to determine the frequency of hypotension (based on mean arterial pressure measurements; MAP) in healthy dogs that were anaesthetised for elective desexing at Murdoch University Veterinary Hospital (MUVH). The secondary aim was to explore any association between gender, age, body mass, heart rate and anaesthetic induction agent with MAP. We hypothesised that MAP less than 60 mmHg would occur in at least 40% of healthy anaesthetised dogs. A historical cohort study was performed using anaesthetic records from dogs desexed by clinicians in the general practice service at MUVH between 2007 and 2011. Each dog was categorised according to the following criteria: I) hypotension - the lowest MAP present for at least two consecutive measurements was less than 60 mmHg, II) mild hypotension - the lowest MAP present for at least two measurements was between 60–79 mmHg and III) normotension - all MAP measurements were between 80–120 mmHg. The frequency of each category (point estimate, 95% confidence interval - CI) was calculated. Records from 188 dogs were included with 87/188 (0.46; 95% CI 0.39-0.53) categorised as hypotensive, 72/188 (0.38; 95% CI 0.31-0.45) as mildly hypotensive and 29/188 (0.15; 95% CI 0.10-0.21) as normotensive. Normotensive dogs were significantly older than hypotensive and mildly hypotensive dogs (P=0.0003 and 0.009 respectively) and hypotensive dogs had significantly lower body mass than mildly hypotensive dogs and normotensive dogs (P=0.008 and P=0.015 respectively). The frequency of hypotension was significantly higher when acepromazine and methadone was administered compared to acepromazine and morphine. The frequency of hypotension observed in the current study was at least as high as hypothesised at approximately 40%. This supports the concern that the development of hypotension is not infrequent and monitoring and managing blood pressure in healthy dogs is important. The significantly higher frequency of hypotension in younger and smaller dogs suggests modification of anaesthetic techniques may be warranted.

Item Type: Journal Article
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Publisher: Australian Small Animal Veterinary Association
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