Ultrasound Imaging of No-Needle 1-Quadrant Sub-Tenon Local Anaesthesia for Cataract Surgery

One Quadrant Sub-Tenon's Capsule Anesthesia in Anterior Segment Surgery

Reports of complications associated with local anesthesia in ophthalmic surgery have increased conspicuously in recent years. Sub-Tenon's capsule anesthesia for anterior segment surgery avoids the risks of retrobulbar and peribulbar injections. This study compared sub-Tenon's and retrobulbar anesthesia. Patients undergoing various anterior segment surgery were randomly assigned to sub-Tenon's or retrobulbar anesthesia; 300 were operated with 1-quadrant sub-Tenon's anesthesia (1-QST) and the results were compared with 270 patients operated with retrobulbar anesthesia. Retrobulbar anesthesia consisted of a 2.5 ml injection of a 1:1 mixture of 2% lidocaine without epinephrine and 0.5% bupivacaine. Sub-Tenon's anesthesia involved direct transconjunctival infiltration of the same local anesthetic directly into the sub-Tenon's space, in the inferior-nasal quadrant, using a blunt 23-gauge cannula. Patients undergoing various anterior segment surgery procedures were randomly assigned to 1-QST or retrobulbar anesthesia; 300 patients were operated with 1-QST and the results were compared with 270 patients operated with retrobulbar anesthesia. Preinjection mean (+/- SD) IOP wer 12.9 +/- 3.7 mmHg in the retrobulbar and 13.4 +/- 3.2 mmHg in the 1-QST patients. Preoperative intraocular pressures were 8.7 +/- 3.0 mmHg in the retrobulbar and 9.2 +/- 3.2 mmHg in 1-QST patients. Pre- and postinjection IOP for retrobulbar and 1-QST patients were similar. Pain scores for delivery of the anesthetic, using a numerical rating scale, produced a median score of 1 for 1-QST and 2 for the retrobulbar technique. For the subsequent operative procedure, the median score was 1 for 1-QST and 2 for the retrobulbar patients. Complete akinesia was achieved in 41% with 1-QST and in 69% of retrobulbar patients. 1-QST patients with incomplete akinesia most often had lateral muscle function which did not interfere with the operation. We found the use of a blunt cannula to deliver anesthetic into the sub-Tenon's space as a simple, safe and effective alternative approach to traditional retrobulbar anesthesia in anterior segment surgery.

Combined propofol sedation with sub-Tenon's lidocaine/mercaine infusion for strabismus surgery in adults

AIMS

To evaluate the safety and efficacy of propofol sedation combined with sub-Tenon's anaesthesia for strabismus surgery in adults.

METHODS

Thirty-two consecutive patients aged 31-85 years underwent strabismus surgery under general (n=16) or local (n=16) anaesthesia. In the local anaesthesia (study) group, sedation was induced with a loading dose of midazolam, fentanyl, and propofol, followed by continuous infusion of propofol, 3-6 mg/k/h to deep sedation. A nasal tube was inserted to prevent airway obstruction. Sub-Tenon's anaesthesia included infusion of a 3-4 ml mixture (50 : 50) of lidocaine 2%/mercaine 0.5%. General anaesthesia consisted of premedication with midazolam, followed by fentanyl, esmeron-bromate, propofol, and tracheal intubation. Duration of surgery and anaesthesia, intraoperative oculocardiac reflex and arrhythmias, time to discharge, postoperative pain, nausea and vomiting, and patient and surgeon satisfaction were evaluated.

RESULTS

The local anaesthesia group had a significantly shorter operative and anaesthesia time, fewer episodes of oculocardiac reflex or arrythmia/bradycardia requiring treatment, fewer early or late episodes of nausea and vomiting, and less pain. The patients and surgeon in this group reported higher satisfaction.

CONCLUSION

Propofol sedation with local sub-Tenon's injection of lidocaine/mercaine is recommended for the induction and maintenance of anaesthesia during unilateral or bilateral strabismus surgery in adults. The method is quick and effective, without systemic or ocular side effects.

Localization of local anesthetic solution by magnetic resonance imaging

PURPOSE

The aim of this study was to examine the distribution of local anesthetic solution by magnetic resonance imaging (MRI) after combined peribulbar and retrobulbar, superomedial retrobulbar, and sub-Tenon's injection in relation to clinical akinesia.

DESIGN

Randomized clinical trial.

PARTICIPANTS

Fifteen patients scheduled for cataract surgery, 5 patients in each group.

METHODS

Five patients received combined peribulbar and retrobulbar anesthesia, 5 patients received superomedial retrobulbar injection, and 5 patients had sub-Tenon's injection, all with a combination of bupivacaine 0.75%, lidocaine 2%, and hyaluronidase. The MRI scans were performed before the injection and up to 35 minutes after the injection.

RESULTS AND CONCLUSIONS

Reliable anesthesia is achieved using a combined peribulbar and retrobulbar block and a relatively great volume of local anesthetic solution, which spreads throughout the orbit, as evidenced by MRI. After superomedial retrobulbar and sub-Tenon's injection, the local anesthetic solution accumulates behind the globe. Sub-Tenon's injection gives good analgesia and slight akinesia with a very small volume. Superomedial retrobulbar injection and combined peribulbar and retrobulbar block provide a similar degree of exophthalmos, which seems to be the result of the volume injected behind the globe.

Ultrasonic localization of anaesthetic fluid using sub-Tenon's cannulae of three different lengths

PURPOSE

To study the distribution of anaesthetic fluid during sub-Tenon's block by B-scan ultrasonography using cannulae of three different lengths.

METHODS

A total of 30 patients undergoing routine phacoemulsification and lens implantation were studied after informed consent had been obtained. Ages ranged from 60 to 92 years and globe axial lengths from 21.50 to 27.00 mm. All were given a sub-Tenon's block and the patients were classified into three groups in which either a long, intermediate, or short cannula was used. B-scan ultrasonography was performed before administration of the anaesthetic agent, during injection, and 2 min after completion of the injection.

RESULTS

In all patients the optic nerve was identified. During the injection, anaesthetic fluid could be seen tracking behind the globe and opening up the posterior sub-Tenon's space (the previously described 'T'-sign). After 2 min very little or no fluid was seen, suggesting that it had dispersed into the surrounding tissues. There was no discernible difference in the distribution of fluid or in the quality of the block in the three groups.

CONCLUSIONS

B-scan ultrasonography can reliably identify the distribution of anaesthetic fluid during sub-Tenon's block. Anaesthetic agents can be successfully delivered into the sub-Tenon's space by long, intermediate, or short cannulae.

Anticoagulation and cataract surgery: a review of the current literature

The anticoagulated patient presenting for cataract surgery presents many dilemmas for anaesthetist and surgeon alike. Current evidence suggests that warfarin therapy significantly improves prognosis in patients with atrial fibrillation with coexisting cerebrovascular disease, and those with non-tissue prosthetic heart valves. Inadequate anticoagulation in these groups exposes them to higher risk of systemic embolic complications, which are frequently devastating. Warfarin is an extremely complex drug. Attempted cessation and recommencement of warfarin therapy may not only reverse anticoagulation for unpredictable periods of time but may also expose patients to a transient yet dangerous hypercoagulable state. In most instances this state represents an additive risk to the untreated disease for which warfarin is being prescribed. It is difficult to accurately measure risks of local anaesthetic blockade in anticoagulated patients as techniques are not standardized. Smaller needles and single injections appear safer with deep eye blocks, while sub-Tenon's block and topical techniques appear safer still, and acceptable provided patients and surgeons are happy with the conditions so created. Retrobullbar haemorrhage appears to occur more frequently in anticoagulated patients who have their anticoagulation continued up to the time of cataract surgery. Retrobulbar haemorrhage is also more frequent in this same group even when anticoagulation is ceased prior to surgery when compared to non-anticoagulated patients. Prognosis for visual acuity with retrobulbar haemorrhage is generally good, given an experienced surgeon is present to rapidly decompress the eye.

Ultrasonic localization of anesthetic fluid in sub-Tenon's, peribulbar, and retrobulbar techniques

PURPOSE

To determine the distribution of anesthetic fluid during 3 regional anesthetic techniques routinely used for phacoemulsification.

METHODS

Patients having routine cataract extraction by phacoemulsification were studied after informed consent had been obtained. B-scan ultrasonography was performed on the eye before administration of the anesthetic agent. Kinetic echography was used to scan the eye during administration of the anesthesia to show the needle position and location of fluid in the orbit during the injection. Ten minutes after injection, another scan was performed to outline the pattern of fluid distribution.

RESULTS

In all patients, the needle and the anesthetic fluid were seen on ultrasonography, with sub-Tenon's the most easily seen. In the sub-Tenon's group, fluid tracked behind the globe in the retrobulbar space, appearing as a dark outline during the injection. The fluid around the optic nerve developed a characteristic T sign. In the retrobulbar technique, the needle was less easily identifiable and fluid localized within the cone. The fluid distributed in the intraconal fat. Identification of the peribulbar needle and fluid was also more difficult; the fluid was, however, seen in the extraconal fat. After 10 minutes, fluid was seen within the cone.

CONCLUSION

B-scan ultrasonography was a suitable method of identifying the needle position and the distribution of anesthetic fluid in regional ocular anesthesia. The sub-Tenon's technique appears to be the safest method of introducing anesthetic fluid into the retrobulbar space without the potential complications of sharp-needle techniques.

Topical anesthesia for phacoemulsification: initial 20-case series with one month follow-up

We report the results of our initial 20 phacoemulsification cases performed using topical anesthesia. The preferred topical regimen consisted of preservative-free 0.75% bupivacaine. Intravenous sedation was provided primarily with fentanyl and midazolam. Phacoemulsification was performed through a scleral tunnel incision, and a one-piece poly(methyl methacrylate) or three-piece silicone intraocular lens was implanted. There were no complications with the anesthetic technique. One day postoperatively, 69% of patients with a desired refractive error within 0.75 diopters of emmetropia had an uncorrected visual acuity of 20/40 or better. At one month, all patients had a best corrected acuity of 20/30 or better, and 60%, 20/20 or better. Eighteen patients reported complete intraoperative comfort, and 17 reported complete postoperative comfort. Seven of the 10 patients who had had previous peribulbar anesthesia preferred topical. All 10 "first eye" patients said they would choose topical anesthesia for future surgery. With appropriate case selection, topical anesthesia for phacoemulsification surgery can be used with excellent intraoperative and postoperative results.