Central nervous system complications after 6000 retrobulbar blocks

Six thousand consecutive patients in whom retrobulbar anesthesia was performed by an anesthesiologist before ophthalmic surgery were studied. Sixteen patients (1 in 375) developed signs and symptoms presumed to be caused by the direct spread of the local anesthetic agents to the central nervous system. These signs and symptoms ranged from drowsiness, blindness of the contralateral eye, abnormal shivering, or vomiting, through to respiratory depression, apnea, hemiplegia, aphasia, convulsions, unconsciousness, and cardiopulmonary arrest. The severity of the symptoms was unrelated to the dose of anesthetic administered. The time of the onset of symptoms after the retrobulbar injection was variable (average 8 min, range 2 to 40 min). The possibility of a life-threatening complication occurring was rare (1 in 750) but unpredictable. The need for closely monitored anesthesia care of all patients having surgery under retrobulbar anesthesia is stressed.