Objective: To describe a case of clinically significant norepinephrine extravasation in a dog with a successful outcome following the use of subcutaneous phentolamine infusion.

Case summary: An 8-year-old male neutered Labrador Retriever experienced norepinephrine extravasation from a cephalic, peripheral intravenous catheter while under anesthesia for an exploratory laparotomy. Upon recognition of norepinephrine extravasation, moderate subcutaneous edema and a painful dermal plaque were apparent at the extravasation site. Ten milligrams of phentolamine mesylate, a potent alpha-adrenergic receptor antagonist, were diluted in 10 mL of sterile saline and administered subcutaneously in small aliquots at multiple sites in the area of extravasation. The patient remained hemodynamically stable during and after the infusion. Most phentolamine injections produced instantaneous erythematous macules that resolved 24-36 h later, and the integument in the extravasation area rapidly changed from a “blanched” to a “pink” color. The subcutaneous edema gradually resolved within 7 days post-extravasation. At 12 h following extravasation, the dermal plaque progressed into a necrotic focus, which later developed into an ulcer (36 h), then a small crust (7 days), and finally healed epidermis (9 days). When the patient was euthanized 10 days after surgery due to continued decline secondary to systemic disease, there remained only a small superficial crust at the site of extravasation.

Unique information: To the authors’ knowledge at the time of submission, this case report documented the first reported clinical use of subcutaneous phentolamine infusion for the management of norepinephrine extravasation in a veterinary species.

Flynn GE, Riffe CI, Aicher KM, Wheeler LR. Phentolamine Infusion for the Treatment of Norepinephrine Extravasation in a Dog. J Vet Emerg Crit Care (San Antonio). 2025 Mar 24:e13461. doi: 10.1111/vec.13461. Epub ahead of print. PMID: 40127428.