Technique
Resuscitative equipment, monitoring and personnel must be immediately available prior to performance of this block. The retrobulbar block is performed with the patient either seated or supine and looking straight ahead. The head should be maintained in a neutral position. A needle (22-27 Gauge, 3cm long) is inserted at the inferolateral border of the bony orbit and directed straight back until it has passed the equator of the globe. It is then directed medially and cephalad toward the apex of the orbit. Occasionally a 'pop' is felt as the needle tip passes through the muscle cone delineating the retrobulbar space. Following a negative aspiration for blood, 2-4mls of local anesthetic solution is injected and the needle is withdrawn. 2% Lidocaine (Xylocaine) and 0.5% to 0.75% bupivicaine (Marcaine) are two commonly used agents. Avoid epinephrine, commonly mixed in with local anesthetics for vasconstriction, in seeing eyes as this can cause a central retinal artery occlusion. An enzyme, hyaluronidase, is frequently a component of the anaesthetic solution, as it accelerates and improves dispersal of the agent. Akinesia and anesthesia quickly ensue within minutes with a successful retrobulbar injection. Retrobulbar block can be used successfully for corneal transplantation but may required supplemental facial nerve block. Retrobulbar block can block levator palpebrea muscle but not orbucularis oculi. Several techniques for facial nerve block can be used in conjunction with retrobulbar block.
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