COMPARISON OF RETROBULBAR, SUB-TENON ANESTHESIA AND MEDIAL CANTHUS EPISCLERAL ANESTHESIA FOR 25-GAUGE POSTERIOR VITRECTOMY.

PURPOSE: The aim of the study is to compare the efficacy, safety, and globe akinesia between retrobulbar anesthesia, sub-Tenon anesthesia, and medial canthus episcleral anesthesia for 25-gauge posterior vitrectomy. METHODS: A total of 340 25-gauge vitrectomy data sheets were retrospectively collected between November 2017 and June 2019. Ninety patients were included in the study. These patients were matched by sex and age to receive retrobulbar anesthesia (group 1, n = 30), sub-Tenon anesthesia (group 2, n = 30), and medial canthus episcleral anesthesia (group 3, n = 30). Globe akinesia was recorded after the injection of anesthetic at 2, 5, and 10 minute time intervals. Patients were asked to rate the pain during administration of anesthesia, during surgery, and postoperatively using the visual analog pain scale. RESULTS: For a perfect block, at 10 minutes, retrobulbar outperformed both sub-Tenon and medial canthus episcleral anesthesia which seemed quite similar. During administration, the three techniques did not show statistically different effects on pain. Regarding perioperative pain, retrobulbar outperformed medial canthus episcleral anesthesia. CONCLUSION: All three techniques allowed for safe surgery. Retrobulbar obtained the best results, although sub-Tenon proved to be a valid alternative. Medial canthus episcleral anesthesia obtained mostly good and fair blocks and acceptable pain levels during surgery. Further studies should investigate whether optimal anesthetic efficacy can be obtained with sub-Tenon and medial canthus episcleral techniques when higher volumes are used.

Effects of Qingguang'an containing serum on the expression levels of autophagy-related genes in human Tenon's fibroblasts induced by transforming growth factor beta 1.

OBJECTIVE: To explore the effects of Qingguang'an () containing serum on the expression levels of autophagy related genes in the transforming growth factor beta 1 (TGF-ß1)-activated human Tenon's fibroblasts (HTFs). METHODS: (a) Primary HTFs were stimulated by TGF-ß1 and underwent immunohistochemistry, which established a cell model after Glaucoma filtration surgery (GFS). (b) The cell models were divided into 4 group: normal group (normal cells), model group (+TGF-ß1),treatment group (+TGF-ß1+ medicated serum), and positive control group (TGF-ß1+ rapamycin). Then, Qingguang'an medicated serum with optimum concentration was added to the corresponding group. The autophagy positive cells were identified by the Cyto-ID autophagy detection kits under fluorescent microscope and Cytation 5 multifunctional instrument for cell imaging. And the mean fluorescence intensity of autophagy positive cells was determined by flow cytometry. The expression levels of autophagy related genes － Beclin-1, autophagy related gene 5 (ATG-5), and microtubule-associated protein 1 light chain 3 (LC-3Ⅱ were detected by quantitative reverse transcription-polymerase chain reaction and Western blot analysis. RESULTS: Compared with the normal group and the model group, the relative mRNA expression levels of autophagy-related genes (Beclin-1, ATG-5 and LC-3Ⅱ in the experimental group were notably increased (P < 0.05, P < 0.01), and with the extension of treatment time, it had an increasing trend (48 h was more obvious), which showed a certain time dependency; the protein expression levels of autophagy-related genes (Beclin-1, ATG-5, and LC-3Ⅱ were significantly increased in the experimental group (P < 0.05, P < 0.01). With the prolongation of treatment time, there was an increasing trend (48 h was relatively obvious), and it revealed a certain time dependency. CONCLUSION: The Qingguang'an medicated serum could up-regulate autophagy related genes (Beclin1, ATG5, and LC3Ⅱ in the TGF-ß1-activated HTFs.

A Tenon's capsule/bulbar conjunctiva interface biomimetic to model fibrosis and local drug delivery.

Glaucoma filtration surgery is one of the most effective methods for lowering intraocular pressure in glaucoma. The surgery efficiently reduces intra-ocular pressure but the most common cause of failure is scarring at the incision site. This occurs in the conjunctiva/Tenon's capsule layer overlying the scleral coat of the eye. Currently used antimetabolite treatments to prevent post-surgical scarring are non-selective and are associated with potentially blinding side effects. Developing new treatments to target scarring requires both a better understanding of wound healing and scarring in the conjunctiva, and new means of delivering anti-scarring drugs locally and sustainably. By combining plastic compression of collagen gels with a soft collagen-based layer, we have developed a physiologically relevant model of the sub-epithelial bulbar conjunctiva/Tenon's capsule interface, which allows a more holistic approach to the understanding of subconjunctival tissue behaviour and local drug delivery. The biomimetic tissue hosts both primary human conjunctival fibroblasts and an immune component in the form of macrophages, morphologically and structurally mimicking the mechanical proprieties and contraction kinetics of ex vivo porcine conjunctiva. We show that our model is suitable for the screening of drugs targeting scarring and/or inflammation, and amenable to the study of local drug delivery devices that can be inserted in between the two layers of the biomimetic. We propose that this multicellular-bilayer engineered tissue will be useful to study complex biological aspects of scarring and fibrosis, including the role of inflammation, with potentially significant implications for the management of scarring following glaucoma filtration surgery and other anterior ocular segment scarring conditions. Crucially, it uniquely allows the evaluation of new means of local drug delivery within a physiologically relevant tissue mimetic, mimicking intraoperative drug delivery in vivo.

Surgical outcomes of macular hole and epimacular membrane treatment in patients with intraoperative amaurosis under sub-Tenon's anesthesia.

OBJECTIVE: Some patients have been found to develop intraoperative amaurosis under sub-Tenon's anesthesia. We explored whether these patients have poor surgical outcomes during mid- to long-term postoperative follow-up. METHODS: In this case series, 74 of 85 patients with macular diseases who underwent phacoemulsification combined with vitrectomy under sub-Tenon's anesthesia developed intraoperative amaurosis. The surgical outcomes at the 2- and 4-month follow-ups in these patients were investigated and compared with the outcomes in patients without amaurosis using best-corrected visual acuity (BCVA), optical coherence tomography (OCT), and pattern visual evoked potential (PVEP). RESULTS: Both BCVA and the OCT-based macular structure in patients with intraoperative amaurosis showed significant postoperative improvement comparable with that of patients without amaurosis. The presence of intraoperative amaurosis was not associated with either macular hole closure or macular edema regression. PVEP revealed no significant changes in the wave latency or amplitude before and after surgery. CONCLUSION: Intraoperative amaurosis following sub-Tenon's block is commonly seen but does not predict a poor surgical prognosis. When a patient develops amaurosis during surgery, the surgeon should increase patient comfort through verbal communication rather than perform an additional intervention to help relieve the patient's anxiety.

Natural Plant Extract Berbamine Is a Potent Inhibitor of Cell Growth and Survival of Human Tenon's Fibroblasts.

INTRODUCTION: Post-trabeculectomy scarring due to excessive proliferation of human Tenon's fibroblasts (HTFs) often led to operation failure. Developing a new anti-fibrosis drug with high efficacy to inhibit HTF cell growth will greatly improve the effectiveness of trabeculectomy. OBJECTIVE: This study aims to investigate the effect of berbamine (BBM) treatment on the cell growth and survival of HTFs. METHODS: Cultured human fetal Tenon's fibroblasts (HFTFs) were treated with or without different concentrations of BBM. Cell morphology was observed with a phase contrast microscope. A CCK-8 method and Ki67 immunofluorescence were used to determine cell viability and cell proliferation. A scratch test was used to study cell migration. Flow cytometry and TUNEL staining were performed to detect cell apoptosis. The expression of BAX/BCL-2, ERK, and AKT/mTOR pathway components was determined by Western blotting. RESULTS: BBM treatment disrupted HFTF normal morphology and inhibited its cell growth in a dose-dependent manner. Ki67 immunofluorescence and scratch assay showed BBM suppressed HFTF cell proliferation and migration. Importantly, BBM dose-dependently increased the BAX/BCL-2 ratio and induced apoptosis in HFTF cells. Western blotting showed BBM significantly inhibited the ERK and AKT/mTOR pathway, and PTEN inhibition ameliorated the inhibitory effect of BBM on cell viability and survival in HFTFs. CONCLUSIONS: BBM potently inhibits the cell growth and survival of HTFs through AKT/mTOR and has the potential to serve as an anti-fibrosis drug after trabeculectomy.

Efficacy and Safety of a Novel Blunt Cannula Trans-Sub-Tenon's Retrobulbar Block for Vitreoretinal Surgery.

PURPOSE: To evaluate a novel trans-sub-Tenon's retrobulbar block (TSTRB) compared to sub-Tenon's block (STB) and peribulbar block (PBB) anesthesia for vitreoretinal surgery. METHODS: This study was a prospective evaluation of cases undergoing TSTRB, STB, or PBB. The Kallio scale and Brahma scales were used to score hemorrhage and extraocular motility, respectively. Pain was documented on a visual analog score graded (1-10) at induction, intraoperatively, and postoperatively, any confounding variables were noted. RESULTS: Seventy eyes have been used in this analysis, of which TSTRB was used in 37% (n = 26), PBB in 34% (n = 24), and STB in 29% (n = 20). Postoperative analgesia was required by 10% (n = 2) of STB and 8% (n = 2) of PBB; none of the TSTRB cases required analgesia (P = 0.003). The mean volume required with each technique was as follows: TSTRB, 4.8 ml; STB, 5.3 ml; and PBB, 10.4 ml (P = 0.030). The volume of anesthesia was correlated with the level of proptosis and even more important affected the ease of surgery most (P = 0.005). Akinesia was greatest with TSTRB > PBB > STB (P = 0.040). There were no complications such as brainstem anesthesia, globe perforation, or retrobulbar hemorrhage. CONCLUSION: Intentionally extending a STB into the retrobulbar space, via a TSTRB fenestration utilizes a familiar skill set. TSTRB produced the best levels of reduced kinesia during surgery and increased duration of postoperative analgesia. The technique uses a small-volume anesthesia.

Incidence and impact factors of intraoperative loss of light perception under sub-Tenon's anesthesia in patients with macular diseases.

PURPOSE: To investigate the incidence and impact factors of intraoperative loss of light perception (LP) under sub-Tenon's anesthesia in patients with macular diseases. METHODS: Eighty-five consecutive patients received standard phacoemulsification combined pars plana vitrectomy (PPV) under sub-Tenon's anesthesia. At several checkpoints during the surgery (the end of phacoemulsification, the end of vitrectomy, and the end of surgery), participants were interviewed about whether they had LP or not after removing the influence of contralateral eye and the photo-bleaching effect. In patients treated with retinal photocoagulation, visual experience on laser flashes was evaluated. RESULTS: Under routine draping, no patients reported loss of LP at all the checkpoints. When the contralateral eye was tightly covered, the rates of LP loss were 84.7%, 97.6%, and 87.1% at the end of phacoemulsification, the end of vitrectomy, and the end of surgery, respectively. When the photo-bleaching effect was also removed, the rates of LP loss were 61.2%, 82.4%, and 56.5% at each checkpoint, respectively, and there were 87.1% (74/85) of patients reporting visual loss in at least one checkpoint. In addition, 76.9% (50/65) of patients could not feel laser flashes during retinal photocoagulation. CONCLUSION: Intraoperative loss of LP under sub-Tenon's anesthesia was a relatively common and reversible event. The conduction block of optic nerve by anesthetic mainly contributed to the visual loss during surgery. Photo-bleaching effect also has some effect on the LP evaluation. Surgeons need to inform and counsel the patients about the intraoperative loss of LP, to prevent any sudden panic attacks in them.

Change in flash visual evoked potentials in New Zealand albino rabbits after sub-tenon's anesthesia.

CONTEXT: The occurrence of amaurosis during ophthalmic anesthesia is well known. The reason for this manifestation has not been studied. PURPOSE: To investigate the effect of sub-tenon's anesthesia on visual conduction in rabbit eyes. METHODS: Fifteen right eyes of 15 New Zealand albino rabbits were included. 2% lidocaine hydrochloride and 0.75% bupivacaine hydrochloride (1 ml, 1:1 mixture) was injected in the sub-tenon's space of 8 eyes while the control group (n = 7) was injected with 1 ml physiological saline. Flash visual evoked potentials (FVEP) were performed with Roland reti-scan system before and, 5 min, 15 min, and 5 days after injection. The natural pupillary diameter and minimal pupillary diameter with light reflex were recorded. RESULTS: In the anesthesia group, N1 latency, P1 latency, and P1 amplitude were 17.13 ± 1.13 ms, 28.25 ± 1.83 ms, 13.45 ± 4.36 µv respectively before injection; 21.75 ± 3.06 ms, 29.63 ± 2.67 ms, 7.24 ± 4.64 µv at 5 min after injection; 22.25 ± 1.39 ms, 29.50 ± 2.51 ms, 7.54 ± 4.47 µv at 15 min after injection, and, 17.75 ± 0.71 ms, 28.13 ± 2.42 ms, 13.17 ± 4.08 µv 5 days after injection. When compared with baseline, N1 latency at 5 min and 15 min after injection showed prolongation (p = 0.019 and p = 0.001, respectively). Likewise, P1 amplitude decreased at 5 min and 15 min after injection (p < 0.001, p < 0.001, respectively). Both N1 latency and P1 amplitude recovered 5 days after the injection. Pupillary light reflex (PLR) constriction amplitude was 35.42% and 0.00% before and at 5 min after injection (p = 0.012). After 5 days it recovered to 33.33%. The FVEP and PLR constriction amplitude did not change significantly after injection in the control group. DISCUSSION: Sub-tenon's anesthesia was associated with changes in the FVEP and pupullary light reflex in rabbit eyes in our study. CONCLUSIONS: The data from this study suggested that sub-tenon's anesthesia could reversibly block visual conduction in rabbit's eyes.

Modified Scleral Tunnel to Prevent Tube Exposure in Patients With Refractory Glaucoma.

PURPOSE: To present and evaluate modified scleral tunnel in prevention of tube exposure following Ahmed valve implantation in refractory glaucoma. METHODS: In the Affiliated Eye Hospital of Shandong University of Traditional Chinese Medicine, a retrospective study was conducted in 36 eyes of 34 patients who were diagnosed with refractory glaucoma and underwent Ahmed glaucoma valve implantation. In the surgery, the modified scleral tunnel was done to prevent tube exposure. RESULTS: At the end of follow-up (mean 21.68±9.25 mo), there was no conjunctival tube exposure in all 36 eyes. The mean intraocular pressure was 18.3±6.79 mmHg, and 8 eyes needed 1 to 3 types of drugs to decrease intraocular pressure. CONCLUSIONS: The modified scleral tunnel technique in Ahmed glaucoma valve implantation is able to prevent conjunctival tube exposure in the patients with refractory glaucoma.

Local Anesthesia With Blunt Sub-Tenon's Cannula Versus Sharp Retrobulbar Needle for Vitreoretinal Surgery: A Retrospective, Comparative Study.

BACKGROUND AND OBJECTIVE: To evaluate the safety and efficacy of a blunt sub-Tenon's cannula for local anesthesia before vitreoretinal surgery compared to a sharp retrobulbar needle. PATIENTS AND METHODS: Retrospective, comparative study of all patients undergoing vitreoretinal surgery at the Medical College of Wisconsin between August 2009 and November 2013. Institutional review board approval was obtained. RESULTS: Of 940 surgeries performed with a sub-Tenon's cannula, 99% (938 of 940) were completed. Of the 771 surgeries performed with a sharp retrobulbar needle, 99% (770 of 771) were completed. Factors associated with use of a sharp retrobulbar needle over sub-Tenon's cannula were presence of prior scleral buckle (P < .01) and inclusion of scleral buckle placement in the procedure (P < .01). No case of globe perforation, severe retrobulbar hemorrhage, or severe conjunctival chemosis was observed in either group. CONCLUSION: Blunt sub-Tenon's cannula appears as effective and safe as a sharp retrobulbar needle for local anesthesia during vitreoretinal surgery. Vitreoretinal surgeons may wish to consider a blunt sub-Tenon's cannula for local surgical anesthesia.

Effects of sub-Tenon's anaesthesia on ocular hemodynamics.

OBJECTIVE: To research the effects of sub-Tenon's anaesthesia (STA) on ocular hemodynamics in patients with cataract using colour Doppler imaging (CDI). DESIGN: Prospective clinical study. PARTICIPANTS: Thirty-four eyes of 34 patients with age-related cataract. METHODS: Peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) values of the ophthalmic artery (OA), central retinal artery, and central retinal vein were measured by CDI before and immediately after performing sub-Tenon block using 2 mL of 2% lidocaine with adrenaline (1:200 000). RESULTS: Both PSV and EDV values were significantly decreased after sub-Tenon injection in all the studied vessels of the patients. However, no important changes were observed in the RI values of the vessels. CONCLUSIONS: STA markedly reduced ocular blood flow. The reduction may be more acceptable compared with other retrobulbar block methods. Sub-Tenon block should be performed carefully to senile patients with cataract with vascular occlusive disorder.

Pain score assessment in babies undergoing laser treatment for retinopathy of prematurity under sub-tenon anaesthesia.

PURPOSE: To assess the tolerability and outcomes of laser treatment for retinopathy of prematurity (ROP) under sub-tenon anaesthetic with oral or rectal sedation using a reliable, multidimensional, and internationally accepted tool for assessment of neonatal pain. METHODS: Sixty-two babies have had ROP laser treatment in our neonatal unit in the 7-year interval between 1 March 2005 and 28 February 2012; 44% (27 of the 62) were performed using sub-tenon anaesthesia. Pain scores were routinely assessed using the Neonatal Pain Agitation and Sedation Scale (N-PASS) every 10 min during laser treatment. The outcome and requirement for re-treatment in this group was compared with that in the intravenous sedation group. RESULTS: Pain scores were available in 19 of the 27 babies treated under sub-tenon anaesthesia. The mean pain score during treatment was 2.7 (SD ± 1.7, range 0.5-6.2). There was no statistically significant correlation between the mean pain score and duration of treatment (Spearman correlation coefficient (ρ) = 0.31; P = 0.09), number of laser burns (ρ = 0.32; P = 0.09), or post-menstrual age of the baby at the time of treatment (ρ = 0.38; P = 0.052). Treatments performed under sub-tenon anaesthesia were as successful as those performed under intravenous sedation. The mean pain scores during laser treatment under sub-tenon anaesthesia in our study were lower than those previously reported during ROP screening or heel-stick procedure.Conclusion Our study demonstrated that sub-tenon anaesthesia with oral or rectal sedation provides sufficient pain control for laser treatment for ROP without the need or risks of intravenous sedation and intubation.

Effects of peribulbar anesthesia (sub-Tenon injection of a local anesthetic) on akinesia of extraocular muscles, mydriasis, and intraoperative and postoperative analgesia in dogs undergoing phacoemulsification.

OBJECTIVE: To evaluate the effects of peribulbar anesthesia (sub-Tenon injection of lidocaine hydrochloride) on akinesia of extraocular muscles, mydriasis, and intraoperative and postoperative analgesia in dogs undergoing phacoemulsification. ANIMALS: 14 Beagles with ophthalmically normal eyes. PROCEDURES: A blinded randomized controlled trial was performed. Dogs were anesthetized and assigned to 2 treatments: concurrent sub-Tenon injection of 2% lidocaine hydrochloride solution (2 mL) and IV injection of saline (0.9% NaCl) solution (0.02 mL/kg; lidocaine group [n = 7]) or concurrent sub-Tenon injection of saline solution (2 mL) and IV injection of 0.2 mg of atracurium/kg (0.02 mL/kg; control group [7]). Pupils were dilated by topical application of a combined tropicamide and phenylephrine ophthalmic solution. Ten minutes after the injections, pupil diameter was measured and phacoemulsification was performed. End-tidal isoflurane concentration was used to evaluate intraoperative pain. Subjective pain scores were recorded during the postoperative period. RESULTS: Akinesia was induced and maintained throughout the surgery in all eyes. Mean ± SD pupil diameter was significantly greater in the lidocaine group (13.7 ± 0.7 mm) than in the control group (12.2 ± 0.8 mm). Isoflurane requirements were significantly lower in the lidocaine group than the control group. However, postoperative pain scores were not significantly different between the groups. CONCLUSIONS AND CLINICAL RELEVANCE: Sub-Tenon injection of lidocaine was an effective method for inducing akinesia of extraocular muscles, mydriasis, and intraoperative analgesia for phacoemulsification in dogs. Therefore, this could be another option for surgical field exposure and pain management during phacoemulsification in dogs.

Anaesthesia in various anterior segment complications of sub-Tenon surgeries.

OBJECTIVE: The sub-Tenon's space is a potential space between the capsule and the sclera. This study evaluated complications from sub-Tenon's anaesthesia in different corneal and anterior chamber ophthalmic surgical procedures. METHODS: The prospective cross-sectional study was carried out at the Baqai Medical University, Karachi, from March 2010 to August 2011, and comprised 149 patients for various minor and major intraocular surgeries. All the patients were operated under sub-Tenon's anaesthesia, administered in the inferio-nasal quadrant with a 19G cannula.Their complications were noted on a specific proforma. Data was analysed for frequencies of complications. SPSS 13 was used for statistical analysis. RESULTS: There were 82 (55%) males and 67 (45%) females who underwent surgery. There were 89 (59.7%) right eyes and 60 (40%) left eyes. The commonest surgery was phaco-emulsification (n = 79; 53%), followed by extracapsular cataract extraction with intraocular lens implantation (n = 33; 22.1%). Subconjuctival haemorrhage (n = 75; 50.3%) was the commonest complication, and the least common was pain during injection (n = 9; 6%). CONCLUSION: There was no incidence of life-threatening or sight-threatening complications. The procedure was almost pain free and can be simply, safely and effectively given by the beginners with due precautions.

Prospective study of cooperation and satisfaction in glaucoma surgery under sub-Tenon's anesthesia.

OBJECTIVES: To evaluate the analgesic effect as well as patient cooperation and satisfaction with sub-tenon's anesthesia in glaucoma surgery. MATERIAL AND METHODS: Prospective uncontrolled study. Fifty-three patients who underwent glaucoma surgery, with or without cataract extraction, with sub-Tenon's anesthesia have been studied. Satisfaction and cooperation were evaluated on a qualitative scale. The pain level was quantified using a numerical scale from 1 (no pain) to 10 (unsupportable pain). RESULTS: The mean pain score at the different periods was: 2.13 (standard deviation [SD] 1.47) on administering anesthesia, 1.74 (SD 1.27) during the surgery, 1.63 SD (1.23) immediately after the procedure, 1.38 (SD 0.38) 30 min later, and 1.38 (SD 0.63) when leaving the recovery unit. The postoperative satisfaction was "fairly or very satisfied" in 92.6% of the cases for both the surgeons and the patients. Twenty-four patients complained during the surgery, 15 of them at the conjunctival suture; in these cases additional anesthesia was administered, and, in 4 cases, intravenous paracetamol was given. Pain scores were significatively higher during the surgery (P=.033), and immediately after the procedure (P=.027) in trabeculectomy than in deep sclerectomy patients. CONCLUSIONS: The good analgesic level reached led to a high level of patient and surgeon satisfaction, even in longer procedures such as deep sclerectomy combined with cataract extraction, or implantation of drainage devices. Pain scores were significatively higher in trabeculectomy than in deep sclerectomy patients.

Comparison of metal and flexible sub-Tenon cannulas.

PURPOSE: To compare metal posterior, flexible posterior, and flexible medium sub-Tenon cannulas for akinesia and anesthesia. SETTING: King Khaled Specialist Eye Hospital, Riyadh, Saudi Arabia. DESIGN: Prospective blind randomized comparison. METHOD: Patients having cataract surgery under sub-Tenon block received a mixture of bupivacaine and lidocaine with hyaluronidase. The patients were divided into 3 groups based on whether a metal posterior sub-Tenon cannula, flexible posterior sub-Tenon cannula, or flexible medium sub-Tenon cannula was used. Pain during injection, akinesia, anesthesia, and complications were recorded. RESULTS: The study enrolled 159 patients. The akinesia score, superior oblique muscle activity, lid movements, and pain during injection were significantly lower in the metal posterior cannula group 2 minutes after injection (P=.002, P=.008, P=.097, and P=.001, respectively); there was no significant difference at 4 minutes, 6 minutes, 8 minutes, and 10 minutes. The incidence of intraoperative pain was low in all groups (P=.607). Chemosis was significantly less in the flexible posterior cannula group (P=.003); however, there was no significant difference in the site of chemosis (P=.460). There was no significant difference in the incidence, site, or severity of subconjunctival hemorrhage (P=.087, P=.072, and P=.331, respectively). No serious complications occurred. CONCLUSIONS: Rigid posterior, flexible posterior, and flexible medium cannulas produced effective and equivalent anesthesia. The flexible cannulas may be safer than the rigid cannulas. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.