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

Purpose To investigate the cardiovascular response to the subconjunctival i njection of 0.25 ml of Mydricaine No. 1 during vitrectomy surgery. Methods Pulse and blood pressure were recorded at 5 min intervals before an d following the subconjunctival injection of Mydricaine No. 1 in a group of 49 sequential patients undergoing vitrectomy surgery under general anaesth etic during a 6 month period. These responses were compared with a sequenti al and similar group of 35 patients during the following 6 months. Results Ten patients in the group administered Mydricaine, but no patients in the control group, developed a sinus tachycardia of >100 beats/min for m ore than 10 min which was attributable to the mydriatic regime used. The oc currence of this response was not predictable based on the patients' age, w eight 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. Conclusion Twenty per cent of patients administered 0.25 mi of Mydricaine N o. 1 subconjunctivally develop a significant sinus tachycardia following in jection. This response is unpredictable and all patients given Mydricaine s hould be monitored carefully after injection.