Unilateral mydriasis after induction of anaesthesia

Unilateral mydriasis is a disturbing finding during anaesthesia and may indicate serious neurological injury. In addition, the assessment of abnormal neurological findings is limited during general anaesthesia, and therefore requires special consideration. I report finding a dilated right pupil (7 mm, nonreactive to light) after bronchoscopic tracheal intubation and induction of general anaesthesia in a frail, 74-yr-old woman with cervical subluxations and spinal cord impingement. The possible aetiology of the unilateral mydriasis includes the effects of anaesthetic agents, stellate ganglion block, impaired venous return from the head and neck, acute intracranial mass lesion or an haemorrhagic event, direct eye trauma, pre-existing medical or surgical conditions, and inadvertent direct deposition of alpha-adrenergic or anticholinergic agents in the eye. Consideration of these factors, the autonomic innervation of the eye, and an intraoperative "wake-up" test allowed satisfactory neurological assessment in this patient and surgery to proceed. Unilateral mydriasis, while unusual, may be seen during general anaesthesia and requires thorough knowledge of autonomic nerve pathways and pharmacology of the eye for correct diagnosis. In this case, mydriasis was considered to result from phenylephrine/lidocaine spray which was used to provide topical anaesthesia to the airway.