547 David H.W. Wong MB as FRCPC,* A modified retrobulbar Ernest Koehrer MD FRCPC,* Hugo F. Sutton MB as FRCS,~ Pamela Merrick BSN* block for eye surgery A modified retrobulbar block (MRB) using a single superome- Cataract surgery is commonly performed as an out- dial injection was compared with the classical retrobulbar block patient procedure and with regional anaesthesia, i-3 The (RB) and peribulbar block (PB) in a randomized, prospective, advantages of this approach include less disruption to surgeon-blinded study involving 150 patients undergoing cat- the patient's physiology,4 rapid return to normal rou- aract surgery. No serious complication occurred in any of the tines, 2,3 better u~ation of hospital beds and economy. patients, The MRB produced higher rates of total akinesia in Retrobulbar block (RB) and peribulbar block (PB) are the orbicularis and all the extraocular muscles, which were sta- the two most frequently used techniques. tistically significant for the orbicularis, superior, inferior and Retrobulbar block was first described in 1884 by lateral rectus and oblique muscles when compared with RB, Knapp who performed an enucleation of an eyeball by and for the superior rectus and oblique muscles when compared injecting cocaine behind the eye. 5 The introduction of with PB. MRB required less supplemental blocks, provided better local anaesthetic agents has made RB an effective good operating conditions for the surgeon, and achieved high and popular choice for most ophthalmic surgical proce- patient acceptance. It is concluded that MRB is a useful al- dures. However, akinesia of the orbicularis muscle may ternative method of ocular block for cataract surgery. not be adequate, and facial nerve block or orbital margin block is often used to immobilize the eyelids. The blind Le bloc r~trobulbaire modifi~ (BRM) ,~ une seule injection insertion of a needle into the orbit may occasionally tra- supdro-interne est compar~ au bloc r~trobulbaire classique (BR) umatize neural and vascular structures or cause systemic et au bloc p~ribulbaire (BP). L~tude randomis~e, prospective, complications, including ocular perforation, 6-8 optic nerve 71 l~nsu du chirurgien comprend 150 patients operas pour ca- damage, 9,t~ retrobulbar venous or arterial haemor- taracte. La chirurgie se d~roule sans complications. Le BRM rhage, ' '- Is contralateral amaurosis, J6.,7 brain-stem an aes- produit plus d'akin~sie totale de l'orbiculaire et de tousles mus- thesia, j8-21 grand mal seizure, n respiratory arrest, 23-z5 cles extra-oculaires: elle est significative pour lbrbiculaire, les and cardiac arrest. 26 Fortunately, serious complications muscles droits inf~rieurs, sup~rieurs, latdraux et les muscles obli- are rare. 27 Nonetheless, RB continues to be the most com- ques comparativement au BP. Le BRM requiert moins souvent monly used technique. de supplement anesth~sique, fournit des bonnes conditions Peribulbar block, with dual injections of anaesthetic op~ratoires et est bien accept~ par le patient. On conclut que solution outside the muscle cone, is an alternative ap- le BRM reprksente une alternative valable pour la chirurgie proach which is believed to reduce the chance of needle oculaire. penetration of the globe or traumatizing the neuro- vascular structures. 3,28-31 This technique involves injection at two sites, uses a greater volume of anaesthetic solution, has a slower onset, and requires prolonged pressure on the orbit to optimize the orbital pressure and the quality of anaesthesia and akinesia. Peribulbar block also pro- vides adequate lid block. However, serious complications such as globe perforation can still occur. 32-35 Key words The requirements of regional anaesthesia for cataract ANAESTHETICTECHNIQUES: regional: retrobulbar; extraction are analgesia, akinesia and optimal orbital SURGERY: ophthalmic. pressure. 3,36 There is controversy in the literature of the From the Departments of Anaesthesia* and Ophthalmology,~ relative merits of the retrobulbar versus the peribulbar Faculty of Medicine, University of British Columbia, blocks. 37-4j In a large series of cases, the incidence of Vancouver, British Columbia inadequate akinesia which required block supplementa- Address correspondence to: Dr. David H.W. Wong, tion was around 20-25%. 3 All cataract surgery at Van- Department of Anaesthesia, Vancouver General Hospital, couver General Hospital (VGH) Eye Care Centre (ECC) Room 3200, 910 West 10th Avenue, Vancouver, British is performed under regional anaesthesia. Our experience Columbia, Canada V5Z 4E3 in the fwst six months of operation in 1988 showed a Acceptedfor publication 16th February, 1993. comparable rate of block supplementation. CAN J ANAESTH 1993 / 40:6 / pp 547-53 548 CANADIAN JOURNAL OF ANAESTHESIA Block supplementation is undesirable. The dual injec- serted through the lower lid, at a point between the lateral tion sites used in PB increases patient discomfort, anxiety one-third and medial two-thirds, to a depth of about 25 and risk of complications. A modified approach to ret- ram, and then angled up and medially toward the apex robulbar anaesthesia using a single superomedial injection of the orbit to a depth of about 33-35 mm (Figure A). is proposed. This modified retrobulbar block (MRB) does Four ml of the anaesthetic mixture were deposited. not require redirection of the needle around the equator of the globe and thus minimizes the possibility of globe Peribulbar block perforation, particularly in highly myopic eyes. It does This consisted of two injections. The first was an in- not require additional facial nerve block that is frequently ferolateral injection of 4 ml, with the needle inserted used in the classical RB technique and is associated wi/.h through the lower lid similar to the retrobulbar approach, a low supplementation rate. but advanced only slightly past the equator of the globe A randomized prospective, surgeon-blinded study was to a total depth of 25 mm. After two minutes, the needle conducted to compare MRB with the classical RB and was inserted superiomedially through the upper lid at PB, in regard to (1) immobilization of the individual ex- a point midway between the medial canthus and the su- traocular muscles, (2) immobilization of the orbicularis praorbital notch, and advanced in the sagittal plane to oculi, (3) incidence of block supplementation, (4) surgical a depth of about 20 mm, where 3 ml of the anaesthetic conditions with respect to analgesia, akinesia and low mixture were deposited (Figure B). globe pressure, (5) patient acceptance, and (6) associated complications. Modified retrobulbar block (study group) This consisted of a single needle insertion superomedially Methods through the upper rid at a point midway between the The study was approved by the Ethics Committees of medial canthus and the supraorbital notch, and advanced the University of British Columbia and the Vancouver slowly in the sagittal plane to a depth of 32-33 mm (Fig- General Hospital. All patients, of one surgeon, having ure C). There should be no resistance to the passage cataract surgery at the VGH-ECC were recruited into of the needle. Four ml of anaesthetic solution were dep- the study after informed consent was obtained. No pa- osited. As the needle was withdrawn, an additional 0.5 tients were excluded. One hundred and fifty patients were ml were injected. Following all block injections, a Super randomly assigned (by draw) to one of the three block Pinkie ball was applied to reduce the intraocular pressure. techniques, resulting in 50 patients in each group. Ten minutes after completion of the block, the eye was All patients received the same standard care. The examined by the anaesthetist and the attending nurse to- preoperative history, physical examination and appropri- gether. The ability of the orbicularis oculi, superior rectus, ate laboratory data (ECG, CBC, electrolytes), were ob- inferior rectus, medial rectus, lateral rectus, and oblique tained before surgery. During the block procedure, ECG, muscles to move was graded as total akinesia, a flicker pulse oximetry, and non-invasive blood pressure were of movement, some movement or full movement. The monitored. The anxiety level of the patient on arrival presence or absence of conjunctival oedema or haemor- was graded by the anaesthetist as calm, mildly to mod- rhage was noted. Numbness of the nose, cheek, lips or erately anxious, and very anxious. gum was also looked for. The pressure of the globe was The anaesthetic block was performed approximately manually assessed and compared with the opposite eye. 30 to 40 min before surgery. The same anaesthetic mix- Inadequate akinesia was treated by supplemental retro- ture was used for all blocks, the final concentration being bulbar or peribulbar injection of 2-3 ml of the same bupivacaine 0.375%, lidocaine 1% and 7.5 units hyalu- anaesthetic mixture, and residual orbicularis movement ronidase per ml. No epinephrine was added. The anaes- was obliterated with van Lint facial nerve block. Eye thetic blocks were performed with the patients resting drops prescribed by the surgeon (flurbiprofen 0.03%, phe- in a 45 ~ reclined position on a dental chair with the eye nylephrine 2.5%, and cyclopentolate 1%) were also given. gazing in neutral position at a marker placed on the ceil- The Super Pinkie ball was reapplied until the patient ing. One drop of tetracaine 0.5% was deposited on the went into the operating room. Sedation with small doses conjunctiva. A disposable 27 gauge 35 mm needle was of intravenous