Hypotension aggravated by dopamine in a dog under isoflurane anesthesia

ABSTRACT

Background: Hypotension (MAP < 60 mmHg) is the most common complication in anesthetic practice and has been identified in 38% of canine patients undergoing general anesthesia for variety of procedures. Normalization of arterial pressure can usually be achieved by decreases in inhalant anesthetic concentrations, fluid administration, and use of inotropes/ vasopressors in healthy animals (ASA I) or animals with mild systemic disease (ASA anesthetic risk II). The present report shows an ASA II dog with severe hypotensive crisis [mean arterial pressure (MAP) < 50 mmHg] during general anesthesia, in which the procedure was aborted because hypotension was aggravated by dopamine.Case A 7-year-old male Bull Terrier was anesthetized for magnetic resonance imaging (MRI) of a tumor in the face. After intramuscular acepromazine (0.01 mg/kg) and meperidine (3 mg/kg), anesthesia was induced with intravenous (IV) ketamine (1 mg/kg) and propofol (2.3 mg/kg) and maintained with isoflurane in oxygen. Ten min after induction of anesthesia MAP was 45 mmHg, while end-tidal isoflurane (ETISO) concentration was 0.5%. End-tidal isoflurane was decreased to 0.3% and an IV bolus of Lactated Ringer’s was initiated (15 mL/kg over 10 min), followed by two ephedrine boluses (0.1 mg/kg, IV) administered 5 min apart. MAP remained low (< 50 mmHg) and dopamine constant rate infusion (CRI) was initiated (7.5 μg/kg/min). Ten minutes after dopamine CRI was commenced, MAP was further decreased to 25-22 mmHg. Dopamine CRI was increased to 10 μg/kg/min, but MAP remained < 25 mmHg. Infusion drugs and isoflurane anesthesia were stopped. After the animal was extubated MAP returned 60-70 mmHg.Discussion: Among the drugs used, isoflurane is known for decreasing blood pressure in a dose-related manner because of its vasodilating properties.[...]