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Introduction: In clinical practice, evaluating dynamic compliance of the respiratory system (C dyn ) could provide valuable insights into respiratory mechanics. Reference values of C dyn based on body weight have been reported, but various factors may affect them and the evidence is scanty. This study aimed to establish a reference interval for C dyn and identify associated variables., Methods: Data were collected from 515 client-owned dogs requiring anesthesia, excluding those with lower airway disease. The dogs were anesthetized, the tracheas intubated, and lungs ventilated at clinicians' discretion across 11 centers in six countries, with no restrictions on anesthesia protocols or ventilation settings, except avoiding inspiratory pauses. Three C dyn measurements from three consecutive breaths per dog were recorded using a standardized form, which also documented factors affecting C dyn identified through literature and an online survey. Various spirometry technologies were used. The substantial variance in C dyn measurements led to a comprehensive analysis using a multiple linear regression model. Multicollinearity (variables highly correlated with each other) was addressed by investigating, transforming, or excluding factors. Initial simple linear regression assessed each variable's individual effect on C dyn , followed by a multiple linear regression model constructed via stepwise forward selection and backward elimination., Results: The best-fitting model identified a linear relationship between C dyn and body mass when the following conditions were met: high BCS (Body Condition Score), orotracheal tubes <7% smaller than predicted, the use of a D-lite flow sensor, and the absence of a high FIO2 (>80%) exposure for more than 10 minutes before C dyn measurement. In cases where these conditions were not met, additional factors needed to be incorporated into the model. Low (1/9, 2/9, 3/9) and medium (4/9, 5/9) BCS, an orotracheal tube of the predicted size or larger and longer inspiratory times were associated with increased C dyn . The use of alternative spirometry sensors, including Ped-lite, or prolonged exposure to high FIO 2 levels resulted in decreased C dyn ., Conclusion and Clinical Relevance: Establishing a reference interval for C dyn proved challenging. A single reference interval may be misleading or unhelpful in clinical practice. Nevertheless, this study offers valuable insights into the factors affecting C dyn in healthy anesthetized dogs, which should be considered in clinical assessments., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. KP declared that she was an editorial board member of Frontiers at the time of submission. This had no impact on the peer review process or the final decision., (Copyright © 2024 Raillard, Mosing, Raisis, Auckburally, Beaumont, Downing, Heselton, MacFarlane, Portier, Robertson, Soares, Steblaj, Wringe and Levionnois.)

Objective:  The aim of this study was to retrospectively evaluate the success rate and perioperative complications of lumbosacral extradural anaesthesia in dogs undergoing total hip replacement., Study Design:  Records of dogs undergoing total hip replacement in which lumbosacral extradural anaesthesia with 0.5% levo- or bupivacaine combined with either morphine or buprenorphine were retrieved. Success rate was defined as intraoperative fentanyl consumption <1 μg/kg/h with no intravenous infusion of other analgesic drugs and no additional morphine/methadone within the first 3 hours from premedication. Prevalence of intraoperative anaesthetic and postoperative surgical complications was calculated., Results:  Overall, 206 dogs were included in the study. Success rate was 88.7%. Hypercapnia (75.2%), hypotension (46.1%), hypothermia (27.7%) and regurgitation (6.3%) were recorded during anaesthesia. Within 24 hours post-surgery, urinary retention (17.8%), vomiting/regurgitation/diarrhea (8.2%) and sciatic neurapraxia of the operated limb (5.8%) were recorded. Luxation of the operated hip occurred at 48 and 72 hours after surgery in two dogs and one dog respectively. One dog had cardiopulmonary arrest at 52 hours after surgery., Conclusion:  While hypercapnia, hypotension and hypothermia might develop intraoperatively, the high success rate and the relatively low prevalence of postoperative surgical complications directly associated with lumbosacral extradural anaesthesia justify its use in dogs undergoing total hip replacement., Competing Interests: None declared., (Thieme. All rights reserved.)