Oculocardiac reflex caused by retrobulbar block in a dog with scoliosis

Abstract

Enucleation of a 9-year-old, spayed female Pekingese's right eye was scheduled because of recurrent eyeball rupture caused by chronic corneal ulcer and descemetocele. Scoliosis of the thoracic vertebra was observed on thoracic radiography. Complete blood count, electrolytes, serum chemistry profiles were within normal ranges except of alkaline phosphatase, which was markedly improved, compared with that of five months ago. Severe respiratory sinus arrhythmia was observed before induction of anesthesia, it disappeared after induction. Retrobulbar block was performed with 0.5% bupivacaine, 2% lidocaine, 0.1% epinephrine combination (4: 1: 0.2 ratio of volume) before start of surgery. After retrobulbar block, heart rate decreased from 110 to 76 beats/min and sinus arrhythmia recurred. It was considered as oculocardiac reflex caused by increase of intraorbital pressure from retrobulbar block, atropine (0.025 mg/kg, IV) was administered and intermittent positive pressure ventilation was started. Three minutes after atropine administration, abnormal waveform of the electrocardiograph was appeared, it suspected as ventricular or supraventricular tachycardia, so lidocaine (2 mg/kg, IV) was administered. Then, heart rate was maintained around 130 beats/min, and the surgery was finished without the other problems. Although, retrobulbar block is performed to provide analgesia and to prevent oculocardiac reflex in ophthalmic surgery, occasionally it could induce oculocardiac reflex by infiltrated volume.