Isoproterenol and phenylephrine infusions following external pacing failure in an anaesthetised dog with sick sinus syndrome undergoing unilateral mastectomy

Managing anaesthesia in dogs with sick sinus syndrome poses significant challenges due to bradyarrhythmias and life-threatening hypotension. An 8-year-old, mixed-breed dog with sick sinus syndrome underwent general anaesthesia for unilateral mastectomy. Anaesthetic drugs with minimal cardiovascular impact and a multimodal analgesic approach, including loco-regional techniques, were employed. Initially, transcutaneous pacing ensured stable cardiovascular parameters, but surgical repositioning led to pacing failure, causing a rapid drop in heart rate and mean arterial pressure. Immediate infusion of isoproterenol and phenylephrine successfully normalised the dog's haemodynamics, allowing the 100-minute surgery to proceed with stable vital parameters. The infusions were discontinued at the end of anaesthesia, leading to an uneventful recovery. This case demonstrates the effectiveness of isoproterenol and phenylephrine infusions in managing an anaesthetised dog with sick sinus syndrome, highlighting the importance of preparedness and having alternative pharmacological interventions ready for device-related challenges.