Investigation of the potential bronchodilatory effect of propofol constant rate infusion for suspected reflex bronchoconstriction in isoflurane-anesthetized dogs.

To evaluate the bronchodilatory effect of propofol constant rate infusion (CRI) on PaO2 and PaCO2 in dogs with suspected bronchoconstriction. In this retrospective, observational study, anesthetic records from August 2022 through July 2023 at the Seoul National University Veterinary Medical Teaching Hospital were reviewed. Dogs with PaO2 < 300 mm Hg and PaCO2 > 45 mm Hg during mechanical ventilation under inhalation anesthesia receiving a propofol CRI were included. Ventilatory parameters and arterial blood gas results were extracted, reported as median (range). Arterial partial pressure of oxygen and PaCO2 values before and after propofol CRI were compared. 7 client-owned dogs were identified. Bronchoconstriction was suspected postintubation based on ventilatory parameters (tidal volume of 8.1 [6.0 to 9.3] mL/kg; compliance respiratory system of 0.6 [0.4 to 0.8] mL/cm H2O/kg) and arterial blood gas results. Despite immediate interventions, including optimizing mechanical ventilation, deepening anesthesia, and drug therapy, PaO2 remained < 300 mm Hg. Thus, a propofol CRI (12 to 14 mg/kg/h) was initiated. Arterial partial pressure of oxygen increased following propofol CRI, rising from 153.0 (75.5 to 233.0) mm Hg to 284.0 (183.0 to 386.0) mm Hg at 30 minutes (mean difference, 130.9 mm Hg; 95% CI, 21.4 to 240.3) and to 331.5 (236.0 to 458.0) mm Hg at 60 minutes (mean difference, 168.0 mm Hg; 95% CI, 93.0 to 244.5). Arterial partial pressure of carbon dioxide levels were similar without improvement. Postoperatively, 4 dogs exhibited hypoxemia, taking 60 to 135 minutes to recover. In dogs with perioperative gas exchange problems, PaO2 increased after propofol CRI, though PaCO2 levels remained unchanged. Propofol CRI improved oxygenation in dogs with suspected bronchoconstriction and may serve as a bronchodilatory treatment option.