OBJECTIVE: To document clinical complications and intervention options associated with norepinephrine (NE) extravasation in dogs and cats. DESIGN: Cases were identified between 2015 and 2021. Because this is an uncommon complication, the findings are compiled as a descriptive retrospective study. SETTING: Cases were provided from 4 universities and 2 private practice groups in the United States, Canada, and Australia. ANIMALS: Fourteen patients (13 dogs, 1 cat) that experienced extravasation events (16 total). INTERVENTIONS: Small animal patients were included where extravasation of a NE constant rate infusion (CRI) was documented. Records were reviewed for information, including suspected underlying condition, description of the interventions pursued after identification of extravasation, clinical signs after extravasation, and survival to discharge or reason for patient death or euthanasia. When available, information was collected pertaining to the NE dose, dilution, total duration of CRI, and duration of CRI before extravasation was recognized. MEASUREMENTS AND MAIN RESULTS: The most commonly reported clinical signs after extravasation of NE were skin necrosis (n = 9 [64.3%]) and swelling (n = 6 [42.9%]). In 10 of 16 events (62.5%), discontinuation of the NE CRI and/or application of a warm compress to the extravasation site were performed
these were the most common nonpharmacological rescue measures. Two patients received subcutaneous phentolamine, and 1 patient underwent hyperbaric oxygen therapy. While surgical intervention was recommended for 4 dogs, 2 improved without surgical debridement. The overall survival rate from underlying disease processes was 57% (n = 8), with only 1 patient (7%) euthanized due to an injury from the extravasation. CONCLUSIONS: Severe lesions can result from NE extravasation in dogs and cats, leading to euthanasia. Although phentolamine remains the treatment of choice, lesions may heal with alternative supportive measures.