• Amanda E Coleman, Molly K Shepard, Chad W Schmiedt, Erik H Hofmeister, and Scott A Brown.
• Department of Small Animal Medicine and Surgery, University of Georgia College of Veterinary Medicine, Athens, GA, USA.
• Vet Anaesth Analg. 2016 Sep 1; 43 (5): 482-94.

ObjectiveTo examine whether preanesthetic administration of enalapril, compared with placebo, results in a greater decline in blood pressure (BP) or decreased responsiveness of BP to isotonic fluids or vasopressors in healthy dogs during isoflurane anesthesia.Study DesignRandomized, experimental, placebo-controlled, blinded, crossover study.AnimalsTwelve healthy, female, purpose-bred beagles.MethodsDogs underwent the following week-long treatment protocols, each preceded by a 1 week washout period: oral placebo twice daily (PLA); oral enalapril, 0.5 mg kg(-1) twice daily, with the 15th dose withheld on the day of anesthesia (ENA-W), and oral enalapril, 0.5 mg kg(-1) twice daily, with the 15th dose administered 90 minutes prior to anesthetic induction (ENA). On day 8 of each treatment period, dogs were anesthetized in random order utilizing a standard protocol. Following stabilization at an end-tidal isoflurane concentration (Fe'Iso) of 1.3%, invasively measured systolic (SAP), diastolic (DAP) and mean (MAP) arterial blood pressure were continuously recorded via telemetry. Hypotension (SAP < 85 mmHg) was treated with the following sequential interventions: lactated Ringer's solution (LRS) bolus (10 mL kg(-1) ); repeated LRS bolus; dopamine (7 μg kg(-1)  min(-1) ); and dopamine (10 μg kg(-1)  min(-1) ) first without and then with vasopressin (1 mU kg(-1)  hour(-1) ).ResultsCompared with the PLA but not the ENA-W group, the ENA group had significantly lower average SAP, DAP and MAP at an Fe'Iso of 1.3%, spent more minutes in hypotension, and required a greater number of interventions to correct moderate-to-severe mean arterial hypotension.ConclusionsIn healthy dogs, enalapril administered 90 minutes prior to isoflurane anesthesia increases the degree of intra-anesthetic hypotension and the number of interventions required to correct moderate-to-severe hypotension.Clinical RelevanceDogs receiving angiotensin-converting enzyme inhibitors on the day of anesthesia may exhibit clinically significant intra-anesthetic hypotension.© 2016 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.

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