Totonidou L. DVM, Intern at the Department of Anaesthesia and Critical care, Companion Animal Clinic, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki
Zioga E. DVM, Intern at the Department of Anaesthesia and Critical care, Companion Animal Clinic, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki
Kazakos G. DVM, PhD, Associate Professor, Department of Anaesthesia and Critical care, Companion Animal Clinic, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki
Introduction
This study describes the effect of phenylephrine as an ophthalmic solution on the mean arterial pressure (MAP) of a canine patient under general anaesthesia.
Clinical case
A 6-year-old English Setter was admitted for nephrectomy (ASA 3). It was premedicated with Fentanyl (5μg/kg iv) and Midazolam (0.2mg/kg iv). Intubation was achieved using Propofol (2mg/kg iv). A semiclosed circle system was used and anaesthesia was maintained using 1% isoflurane with vaporised oxygen. Meloxicam (0.1mg/kg) iv and Fentanyl CRI (0.1 μg/kg/min) iv were administered for analgesia. Invasive blood pressure was monitored via an arterial catheter.
Results
Perioperatively heart rate (HR) ranged from 100 to 160 bpm and MAP from 112 to 55 mmHg. Shortly after the start of surgery HR peaked at 160 bpm and Dexmedetomidine (0.2μg/kg iv) was used twice to decrease the HR (to 156 bpm and 128 bpm respectively). MAP also dropped gradually to 55 mmHg. Two drops of Phenylephrine applied topically in the patient’s right eye increased MAP to 80-90 mmHg within 15 minutes and it was maintained for 30 minutes until the end of the surgery.
Conclusion
Phenylephrine is an alpha-1adrenergic agonist associated with elevation of arterial blood pressure via peripheral vasoconstriction, and reflex bradycardia. Topical administration of Phenylephrincan have similar effects in a dog under general anaesthesia.
References
- Herring IP, Jacobson J D, Pickett JP (2004) Cardiovascular effects of topical ophthalmic 10% phenylephrine in dogs, Vet Ophth 7 (1), 41-46.
- Martin-Flores M, Mercure-McKenzie T M, Campoy L, Erb HN, Ludders JW, Gleed RD (2010) Controlled retrospective study of the effects of eyedrops containing phenylephrine hydrochloride and scopolamine hydrobromide on mean arterial blood pressure in anesthetized dogs, J Am Vet Med Assoc 71 (12), 1407-1412.
