The incidence of systemic side-effects following subconjunctival Mydricaine no. 1 injection

To investigate the cardiovascular response to the subconjunctival injection of 0.25 ml of Mydricaine No. 1 during vitrectomy surgery.

Pulse and blood pressure were recorded at 5 min intervals before and following the subconjunctival injection of Mydricaine No. 1 in a group of 49 sequential patients undergoing vitrectomy surgery under general anaesthetic during a 6 month period. These responses were compared with a sequential and similar group of 35 patients during the following 6 months.

Ten patients in the group administered Mydricaine, but no patients in the control group, developed a sinus tachycardia of > 100 beats/min for more than 10 min which was attributable to the mydriatic regime used. The occurrence of this response was not predictable based on the patients' age, weight or the presence of conjunctival erythema. The magnitude and temporal course of the tachycardia observed were variable. Blood pressure recordings showed no clinically significant changes during the tachycardias.

Twenty per cent of patients administered 0.25 ml of Mydricaine No. 1 subconjunctivally develop a significant sinus tachycardia following injection. This response is unpredictable and all patients given Mydricaine should be monitored carefully after injection.