Prolonged pharmacokinetic simulator-assisted propofol total intravenous infusion in a cat undergoing thoracic duct ligation

Abstract

This case report describes the use of total intravenous anesthesia with propofol and dexmedetomidine for 5 hours in a cat undergoing thoracic duct ligation revision surgery for persistent chylothorax. Following intravenous (IV) premedication with methadone (0.2 mg kg^–1), general anesthesia was induced with IV propofol (2 mg kg^–1) and ketamine (2 mg kg^–1). For maintenance of anesthesia, dexmedetomidine was given as constant rate infusion (1 μg kg^–1 hour^–1), while a free web-based application was used to predict propofol plasma concentration (PPC) in real-time. Ultrasound-guided left erector spinae plane blocks were performed preoperatively at thoracic vertebrae 11 and 13, injecting bupivacaine (1.5 mg kg^–1 site^–1) and dexmedetomidine (1.7 μg kg^–1 site^–1). Propofol infusion rates were manually reduced at anesthetist discretion to achieve reductions in predicted PPC of 0.5–1 μg mL^–1 if no response to surgery was observed. During anesthesia (from tracheal intubation to propofol discontinuation), the propofol infusion rate ranged from 0.066 to 0.2 mg kg^–1 minute^–1, and the mean predicted PPC recorded during anesthesia was 4.23 ± 0.68 μg mL^–1 (mean ± standard deviation). Intraoperatively, heart rate, mean arterial blood pressure, and end-expiratory partial pressure of carbon dioxide were 128 ± 7 beats minute^–1, 76 ± 10 mmHg, and 34 ± 5 mmHg (4.53 ± 0.67 kPa), respectively. No additional intraoperative analgesics were given. Recovery from general anesthesia was uneventful and the trachea was extubated 10 minutes after discontinuing dexmedetomidine and propofol (predicted PPC 2.3 μg mL^–1). The real-time PPC predictions enabled precise propofol titration, ensuring hemodynamic stability while minimizing drug accumulation and promoting rapid recovery.