Complications of ophthalmic regional blocks: their treatment and prevention

Considerations for Corneal Surgery With Patients in the 10th Decade of Life

PURPOSE

The purpose of this study was to report the indications, ocular and systemic comorbidities, and surgical outcomes of corneal transplantation in patients older than 90 years.

METHODS

A retrospective review was conducted to identify individuals 90 years and older who underwent corneal transplantation surgery at the Bascom Palmer Eye Institute between January 2013 and October 2020. Outcomes included best-corrected visual acuity and graft survival over time. Paired t tests were used to compare visual acuity preoperatively versus postoperatively. Graft survival was evaluated with Kaplan-Meier curves.

RESULTS

Fifty-eight eyes of 52 consecutive individuals were included. The mean age of individuals was 92 ± 2 years; 26.9% were male; and 48.1% self-identified as non-Hispanic White and 38.5% as Hispanic. Postoperative follow-up was 14.7 ± 12.1 months. Of the 58 eyes, 44.8% (26/58) underwent penetrating keratoplasty, 46.6% (27/58) Descemet stripping automated endothelial keratoplasty, and 6.9% (4/58) keratoprosthesis. All surgeries were performed under monitored local anesthesia, without major complications. Surgical indications included pseudophakic bullous keratopathy (36.2%), glaucoma-associated corneal decompensation (27.6%), Fuchs endothelial dystrophy (25.9%), and perforated corneal ulceration (19.0%). The best-corrected visual acuity improved by 0.32 (95% confidence interval 0.14-0.50; P < 0.01) as early as 1 month postoperatively, and vision gains were sustained for at least 12 months. Graft survival probability at 12 months was 88%.

CONCLUSIONS

Corneal transplantation is a safe and successful procedure in restoring the visual acuity for patients older than 90 years after careful preoperative evaluation. Further research is needed to evaluate the impact of corneal transplantation on quality of life in patients in the 10th decade of life.

Computed tomography scan measurements of the globe and orbit to assess the risks of traumatic complications from medial peribulbar anaesthesia

Complications of peribulbar anaesthesia include retrobulbar haemorrhage, globe perforation and brainstem anaesthesia. Therefore, this study took measurements relating the proximity of medial canthus to the optic nerve and also the safe angle between orbit and globe using 200 multiplanar reconstructed computed tomography (CT) images of the orbit. The principal results show that in 1.5% of the sample, the optic nerve is within 20 mm of the medial canthus, with a minimum distance of 15 mm. One% have a safe angle of 10 degrees or less between bone and globe. None of the demographic data, nor axial length were predictive of these results. We have shown that there are a minority of patients with unusual orbital anatomy. This places them at a theoretical higher risk of complications. These cases are not currently predicted by measured data.

Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect

Simple Summary

Standing ophthalmic surgeries have become more and more common in horses. For these standing surgeries, the blind retrobulbar block is often used for anesthesia and akinesia of the eye. However, placing a retrobulbar block using this blind technique can lead to complications, for example, penetration of the globe, nerve injury or chemosis due to spreading of the local anesthetic in the region of the globe. For this reason, it might be better to perform the retrobulbar block using guidance by ultrasound. Ultrasound-guided retrobulbar block has only been described twice in the literature using equine cadavers. Comparison of the ultrasound-guided peribulbar technique to the blind technique has only been carried out once. Furthermore, the learning curve of ultrasound-guided retrobulbar nerve block placement has not been evaluated. Our study aimed to compare the blind and ultrasound-guided approaches to retrobulbar block placement in horses and to evaluate the success and complication rates, analyzing the effect of training on ultrasound guidance. A trend towards a significant improvement in accuracy was seen for ultrasound guidance, and larger scale follow-up studies might show a significant training effect on the use of ultrasound in retrobulbar nerve block placement and that the use of ultrasound guidance could be promising.

Abstract

In standing ophthalmic surgery in horses, a retrobulbar nerve block (RNB) is often placed blindly for anesthesia and akinesia. The ultrasound (US)-guided RNB may have fewer complications, but the two techniques have only been compared once in equine cadavers. This study compares the techniques for success and complication rates and analyzes the effect of training on US guidance. Twenty-two equine cadavers were divided into three groups: blind RNBs were performed bilaterally in eight cadavers, US-guided RNBs were performed bilaterally in seven cadavers, and after US-guided training, blind RNBs were performed bilaterally in seven cadavers. All RNBs were performed by the same two inexperienced operators, and a combination of contrast medium (CM; 1.25 mL) and methylene blue dye (1.25 mL) were injected (2.5 mL total volume). Needle positioning in the periorbita and the distance of the CM to the optic foramen were assessed using computerized tomography (CT). Dye spreading was evaluated by dissection. In group 1, 37.5% of the injections were in the optimal central position in the periorbita; in group 2, 75% and in group 3, 71.4%. There was no significant difference between the groups regarding needle position (groups 1 and 2 p = 0.056; groups 1 and 3 p = 0.069, groups 2 and 3 p = 0.8). The mean CM distribution distance was not significantly different between all groups. Group 1 had 18.75% intraocular injections versus 0% in group 2 and 7.1% in group 3 (not significant). US guidance showed no significant increases in accuracy nor decreases in complications. However, the effects on accuracy showed a trend towards significant improvement, and larger scale follow-up studies might show significant training effects on US guidance.

Comparative study of silicone membrane simulator and animal eye models for sub-Tenon's block

To compare and assess silicone membrane-based sub-Tenon's block (STB) simulator and animal eye model (goat's eye) for practicing STB in terms of anatomical similarity and feel of texture of eye layers. The study included 34 participants (26 learners and 8 consultants) from tertiary ophthalmic centres. The participants were divided into groups A and B. Group A performed STB on the goat's eyes before using the silicone membrane simulator. Group B performed STB on the simulator and further proceeded to the goat's eye. Participants had to rate the anatomical similarity and feel of the texture for the simulator model on a scale of 0-10 and share their preference between the two models. In group A, the scores given to the simulator model and the feel of texture of layers were 8.05 ± 0.88 and 7.97 ± 1.07, respectively, and the scores given to the animal model and the feel of texture of layers were 8.11 ± 0.97 and 8.21 ± 0.88, respectively. Group B participants scored the simulator model and feel of texture of layers with 8.13 ± 0.95 and 8.25 ± 0.99, respectively. Overall, 89% participants preferred the simulator; the reasons included ease of usage, helpful warning system, absence of biological waste, and facility for repeatable training. The study validated anatomical accuracy, preference, and ability of usage of the STB simulator. For broader usage, further study involving higher number of participants is recommended.

Anaesthesia for ophthalmic procedures in patients with thyroid eye disease

Thyroid eye disease is an autoimmune inflammatory disorder of the orbit in adults. It causes inflammation, expansion and fibrosis of orbital fat, muscles and the lacrimal gland, leading to facial disfigurement, functional disability and, in severe cases, blindness. Overall, approximately 20% of affected patients need some form of surgical intervention requiring anaesthesia. This narrative review explores the background of thyroid eye disease, surgical procedures performed and their implications for anaesthesia. General anaesthesia is used for orbital decompression procedures, strabismus correction surgery and complex oculoplastic procedures. Local anaesthetic infiltration or regional anaesthesia under monitored anaesthesia care are the techniques most commonly employed for eyelid retraction surgery. It is important to limit the volume of local anaesthetic agent used during infiltration and continuously monitor the orbital volume and ocular pressure with a ballottement technique. In addition, the contralateral eye should be checked and, if necessary, protected against corneal exposure. Retrobulbar, peribulbar and sub-Tenon's blocks are best avoided. Topical anaesthesia has been used for some strabismus correction surgery but its use is limited to motivated and cooperative patients only.

Lacrimal dilator-facilitated incisionless vs. standard sub-Tenon's block: a randomized, prospective and non-inferiority comparative study

BACKGROUND/OBJECTIVES

Standard sub-Tenon's block (STB) involves incision (dissection) of conjunctiva and Tenon's capsule with the help of blunt scissors and forceps, insertion of a blunt sub-Tenon's cannula under the Tenon's capsule and injection of local anaesthetic agent. STB is frequently associated with minor complications such as chemosis and postoperative subconjunctival haemorrhage but rare sight and life-threatening complications. To reduce these minor complications, several variations of incisionless STB have been described however, there are no comparative data. One such incisionless STB involves the use of lacrimal dilator which is easily available in the operating theatre. We compared incisionless lacrimal dilator-facilitated with the standard STB for effectiveness, chemosis, and postoperative subconjunctival haemorrhage.

SUBJECTS/METHODS

After obtaining ethical approval, patients scheduled to undergo elective phacoemulsification cataract surgery were enroled to receive incisionless lacrimal dilator-facilitated STB (Group LD) or a standard STB using Wescott scissors and blunt forceps (Group WS). All patients received 3 mL 2% lidocaine without any adjuvant. No sedation was administered. Demographics of the patients, duration of the procedure, analgesia, akinesia, duration of the procedure intraoperative chemosis, and postoperative subconjunctival haemorrhage were compared.

RESULTS

Both groups were comparable for demographic data, duration of the procedure, analgesia, and akinesia (p > 0.05). The severity of chemosis and postoperative subconjunctival haemorrhage were significantly lower in Group LD (n = 32) in comparison to Group WS (n = 31) (p < 0.001).

CONCLUSIONS

Incisionless lacrimal dilator-facilitated STB decreases intraoperative chemosis and postoperative conjunctival haemorrhage in comparison to standard STB. Analgesia and akinesia are comparable in both techniques.

Ultrasound detection of iatrogenic injury during peribulbar eye block: a cadaveric study

Background

Ophthalmic eye blocks, such as retrobulbar, peribulbar and sub-Tenon’s, are traditionally conducted “blind”. Complications are rare but potentially devastating. Life-threatening complications include brain stem anesthesia and local anesthetic toxicity, whereas sight-threatening complications include globe perforation, optic nerve damage and ocular muscle damage. Ultrasound permits a view of orbital structures and can be used to guide needle placement. The ultrasound appearances of unintended local anesthetic injection into vital orbital structures have not been documented. This study aimed to record the ultrasound appearances of unintended injection locations.

Methods

The spherical shape of the eyeballs of three soft-fix Thiel embalmed human cadavers were restored using glycerol. Iatrogenic injury in peribulbar block was then simulated through injection of printers’ ink mixed with Thiel embalming fluid. Ultrasound was used to guide the needles and the tips were redirected to lie within the globe, lateral rectus and optic nerve. Ultrasound images were recorded during injection. The orbital cavities were then dissected via a superior approach to record the location and extent of injectate spread.

Results

Real-time globe rupture, ocular muscle injection and optic nerve injection were visible using ultrasound. Characteristic appearances were identified in each case. Dissection confirmed needle and injection placement.

Conclusions

The ultrasound appearance of block complications is important to document and should be an integral part of regional anesthesia training. This study is the first to provide such images for ophthalmic nerve blocks. It offers ophthalmic anesthetists and ophthalmologists the potential to diagnose severe complications rapidly and accurately with a potential impact on patient safety.

Analgesic effects of intraorbital insertion of an absorbable gelatin hemostatic sponge soaked with 1% ropivacaine solution following enucleation in dogs

OBJECTIVE

To evaluate analgesic effects and complications associated with intraorbital insertion of an absorbable gelatin hemostatic sponge (AGHS) soaked with 1% ropivacaine solution following enucleation in dogs.

ANIMALS

20 client-owned dogs undergoing enucleation.

PROCEDURES

Dogs were randomly assigned to receive an AGHS soaked with 1% ropivacaine solution (n = 10) or saline (0.9% NaCl) solution (control group; 10) inserted intraorbitally prior to skin closure following enucleation. Carprofen (2 mg/kg [0.9 mg/lb]) was administered SC once after orotracheal extubation and then PO twice a day for 5 days. During the postoperative recovery period, apparent pain level was scored at various points with a modified short-form Glasgow Composite Pain Scale (score range, 0 to 19), and methadone was administered for rescue analgesia if any score was ≥ 5. After dogs returned home, owners recorded their behavior and apparent pain level for the first 3 days following enucleation.

RESULTS

At extubation, the median (range) pain score was significantly higher in the control group (8 [2 to 14]) versus the ropivacaine group (3 [1 to 7]). A greater proportion of dogs in the control group received methadone (7/10 vs 1/10) and had crying or attention-seeking behavior on the first day following enucleation (7/10 vs 1/10). No complications were observed in either group.

CONCLUSIONS AND CLINICAL RELEVANCE

Addition of intraorbital insertion of a ropivacaine-soaked AGHS to the analgesic protocol for dogs undergoing enucleation provided better analgesia than was achieved without this treatment as measured immediately and the first day after surgery, with no noted adverse effects.

Regional Anesthesia for Pediatric Ophthalmic Surgery: A Review of the Literature

Ophthalmic pediatric regional anesthesia has been widely described, but infrequently used. This review summarizes the available evidence supporting the use of conduction anesthesia in pediatric ophthalmic surgery. Key anatomic differences in axial length, intraocular pressure, and available orbital space between young children and adults impact conduct of ophthalmic regional anesthesia. The eye is near adult size at birth and completes its growth rapidly while the orbit does not. This results in significantly diminished extraocular orbital volumes for local anesthetic deposition. Needle-based blocks are categorized by relation of the needle to the extraocular muscle cone (ie, intraconal or extraconal) and in the cannula-based block, by description of the potential space deep to the Tenon capsule. In children, blocks are placed after induction of anesthesia by a pediatric anesthesiologist or ophthalmologist, via anatomic landmarks or under ultrasonography. Ocular conduction anesthesia confers several advantages for eye surgery including analgesia, akinesia, ablation of the oculocardiac reflex, and reduction of postoperative nausea and vomiting. Short (16 mm), blunt-tip needles are preferred because of altered globe-to-orbit ratios in children. Soft-tip cannulae of varying length have been demonstrated as safe in sub-Tenon blockade. Ultrasound technology facilitates direct, real-time visualization of needle position and local anesthetic spread and reduces inadvertent intraconal needle placement. The developing eye is vulnerable to thermal and mechanical insults, so ocular-rated transducers are mandated. The adjuvant hyaluronidase improves ocular akinesia, decreases local anesthetic dosage requirements, and improves initial block success; meanwhile, dexmedetomidine increases local anesthetic potency and prolongs duration of analgesia without an increase in adverse events. Intraconal blockade is a relative contraindication in neonates and infants, retinoblastoma surgery, and in the presence of posterior staphylomas and buphthalmos. Specific considerations include pertinent pediatric ophthalmologic topics, block placement in the syndromic child, and potential adverse effects associated with each technique. Recommendations based on our experience at a busy academic ophthalmologic tertiary referral center are provided.

Outcomes and Adverse Events of Sub-Tenon's Anesthesia with the Use of a Flexible Cannula in 35,850 Refractive Lens Exchange/Cataract Procedures

Purpose

To describe our technique of sub-Tenon’s anesthesia and report adverse events and patient comfort.

Setting

Optical Express, United Kingdom.

Design

Retrospective case series.

Methods

The outcomes of 35,850 intraocular procedures (phacoemulsification and implantation of an intraocular lens) were retrospectively reviewed and the incidence of adverse events related to sub-Tenon’s anesthesia was calculated. On the first postoperative day, patients were asked to complete a questionnaire enquiring about their comfort during and after the procedure. The anesthetic solution consisted of a combination of Lidocaine and Hyaluronidase, which was administered into sub-Tenon’s space with a single-use sterile polyurethane 22G x 1” (0.9 x 25 mm) cannula. Mild conscious sedation (midazolam) was used during anesthetic and surgical procedure.

Results

No significant adverse events that would affect the posterior segment of the eye or result in vision loss were recorded. Subconjunctival haemorrhage related to sub-Tenon’s anesthesia was noted in 4.3% of eyes. Five minutes after the administration of sub-Tenon’s block, 80.6% of eyes had no chemosis, 14.8% had chemosis that affected only 1 quadrant of the eye and 4.5% of eyes had chemosis affecting 2 or more quadrants of the eye. Other adverse events included 14 cases of cyst/granuloma formation in the area of sub-Tenon’s incision and 7 eyes required suturing of the conjunctival cut. Of all patients, 93.2% experienced no or only mild discomfort during or after surgical procedure.

Conclusion

Sub-Tenon’s anesthesia with the use of a flexible cannula is a safe option for ophthalmic anesthesia. No sight-threatening adverse events occurred.

Preventing Adverse Events in Cataract Surgery: Recommendations From a Massachusetts Expert Panel

Massachusetts health care facilities reported a series of cataract surgery-related adverse events (AEs) to the state in recent years, including 5 globe perforations during eye blocks performed by 1 anesthesiologist in a single day. The Betsy Lehman Center for Patient Safety, a nonregulatory Massachusetts state agency, responded by convening an expert panel of frontline providers, patient safety experts, and patients to recommend strategies for mitigating patient harm during cataract surgery. The purpose of this article is to identify contributing factors to the cataract surgery AEs reported in Massachusetts and present the panel's recommended strategies to prevent them. Data from state-mandated serious reportable event reports were supplemented by online surveys of Massachusetts cataract surgery providers and semistructured interviews with key stakeholders and frontline staff. The panel identified 2 principal categories of contributing factors to the state's cataract surgery-related AEs: systems failures and choice of anesthesia technique. Systems failures included inadequate safety protocols (48.7% of contributing factors), communication challenges (18.4%), insufficient provider training (17.1%), and lack of standardization (15.8%). Choice of anesthesia technique involved the increased relative risk of needle-based eye blocks. The panel's surveys of Massachusetts cataract surgery providers show wide variation in anesthesia practices. While 45.5% of surgeons and 69.6% of facilities reported increased use of topical anesthesia compared to 10 years earlier, needle-based blocks were still used in 47.0% of cataract surgeries performed by surgeon respondents and 40.9% of those performed at respondent facilities. Using a modified Delphi approach, the panel recommended several strategies to prevent AEs during cataract surgery, including performing a distinct time-out with at least 2 care-team members before block administration; implementing standardized, facility-wide safety protocols, including a uniform site-marking policy; strengthening the credentialing and orientation of new, contracted and locum tenens anesthesia staff; ensuring adequate and documented training in block administration for any provider who is new to a facility, including at least 10 supervised blocks before practicing independently; using the least invasive form of anesthesia appropriate to the patient; and finally, adjusting anesthesia practices, including preferred techniques, as evidence-based best practices evolve. Future research should focus on evaluating the impact of these recommendations on patient outcomes.

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.

Perioperative considerations and anesthesia management in patients with obstructive sleep apnea undergoing ophthalmic surgery

Obstructive sleep apnea (OSA) is a disorder characterized by breathing cessation caused by obstruction of the upper airway during sleep. It is associated with multiorgan comorbidities such as obesity, hypertension, heart failure, arrhythmias, diabetes mellitus, and stroke. Patients with OSA have an increased prevalence of ophthalmic disorders such as cataract, glaucoma, central serous retinopathy (detachment of retina, macular hole), eyelid laxity, keratoconus, and nonarteritic anterior ischemic optic neuropathy; and some might require surgery. Given that OSA is associated with a high incidence of perioperative complications and more than 80% of surgical patients with OSA are unrecognized, all surgical patients should be screened for OSA (eg, STOP-Bang questionnaire) with comorbidities identified. Patients suspected or diagnosed with OSA scheduled for ophthalmic surgery should have their comorbid conditions optimized. This article includes a review of the literature and highlights best perioperative anesthesia practices in the management of ophthalmic surgical patients with OSA.

Anesthesia for pediatric ophthalmologic surgery

This review presents updated recommendations, based on existing clinical research, for anesthetic management of strabismus surgery in children. In children, unlike adults, eye surgery nearly always requires general anesthesia, even for brief procedures. Recommendations for preoperative anxiolysis, fasting guidelines, and management of upper respiratory infections are discussed. Airway considerations and the oculocardiac reflex are highlighted. The prevention of postoperative complications, including those related to opioid prescription therapy, is also addressed. Finally, given the 2016 warning from the Food and Drug Administration about anesthesia neurotoxicity in children, we discuss recent studies on anesthetic neurotoxicity in children undergoing general anesthesia.

Brainstem Anaesthesia after Retrobulbar Block

Regional anaesthesia techniques in ophthalmology are usually utilized for day case surgery. During various procedures, profound akinesia of the eye and anaesthesia of the surgical site are required, both of which are achieved with retrobulbar block. Due to the anatomy of the eye, life-threatening complications are possible. An 82-year-old female with secondary post-herpetic uveitic glaucoma of the right eye presented at the Department of Ophthalmology for an elective trans-scleral laser cyclophotocoagulation. She was given a retrobulbar block to the right eye with 2 mL of 0.5% levobupivacaine and 2 mL of 2% lidocaine. The procedure was technically performed without any issues. 2-3 minutes after the injection she became lethargic and 5 minutes later she lost consciousness and developed severe hypotension with bradycardia and respiratory arrest. She was successfully intubated and resuscitated, using mechanical ventilation, vasoactive medications, fluid therapy and intravenous lipid emulsion. There are three mechanisms for local anaesthetic (LA) to reach the central nervous system after a retrobulbar block: systemic absorption of LA, direct intra-arterial injection and retrograde flow into the cerebral circulation, and injecting LA into the subdural space via puncturing the dural optic nerve sheath, the latter being most common. The clinical picture of our patient was very consistent with subdural anaesthesia after exposure of the pons, midbrain and cranial nerves to LA, i.e. brainstem anaesthesia. Following appropriate life support measures taken in our case, there was a successful outcome. To minimize the chance for brainstem anaesthesia after retrobulbar block, we recommend low volume with low concentration of LA and block performance by an experienced ophthalmologist or anaesthesiologist with proper technique. Patients receiving retrobulbar anaesthesia should be carefully monitored at least 20 minutes after the block. Life support equipment should be available before performing retrobulbar block.

Retrobulbar Block in Pediatric Vitreoretinal Surgery Eliminates the Need for Intraoperative Fentanyl and Postoperative Analgesia: A Randomized Controlled Study

BACKGROUND AND OBJECTIVES

Pediatric ophthalmologic surgery is traditionally accomplished by general anesthesia with opioids, but respiratory depression remains a major concern. Our study compared the efficacy of retrobulbar block with systemic fentanyl on pain, hemodynamic, and stress response in pediatric vitreoretinal surgery.

METHODS

A prospective double-blind, randomized controlled study was performed comparing retrobulbar block with intravenously administered fentanyl in 28 children aged 1 to 6 years undergoing vitreoretinal surgery. After general anesthesia was induced, retrobulbar block with 0.5% ropivacaine was accomplished in group RB (general anesthesia plus retrobulbar block) (n = 13), and normal saline was injected into retrobulbar space in group F (general anesthesia alone) (n = 15). Fentanyl 0.5 μg/kg was administered when signs of inadequate anesthesia were observed.

RESULTS

Respiratory depression (defined as a persistent respiratory rate <10 breaths/min or persistent oxygen desaturation <92%) was observed in 5 of 15 patients in group F after laryngeal mask airway was removed in the operating room, compared with none in group RB. All children in group F consumed intraoperative fentanyl rescue (average intraoperative fentanyl consumption, 1.3 ± 0.3 μg/kg) compared with none in group RB. Pain scores assessed with Faces, Legs, Activity, Cry and Consolability were significantly lower in group RB than in group F (1 [0, 3.5] vs 5 [3, 7], P = 0.003) immediately after laryngeal mask airway removal. Heart rate in group RB was significantly lower than that in group F before anesthesia induction, at the beginning and end of surgery, respectively. Mean blood pressure in group RB was significantly lower than that in group F at the beginning of surgery. Postoperative tumor necrosis factor α concentration in group RB was significantly lower than that in group F.

CONCLUSIONS

Retrobulbar block is safe and effective as an alternative to systemic fentanyl and could provide better pain management, hemodynamic suppression, and stress response suppression in pediatric vitreoretinal surgery.

Optimal Dose of Dexmedetomidine Retrobulbar Anesthesia during Phacoemulsification Cataract Surgery

Background

The cataract surgery anesthesia should be to make the procedure as safe and as satisfactory as possible for all concerned. The recent progress in anesthesia and surgery now allow cataract extraction to be done with minimal physiological changes to the patient. We aimed in the study to compare between two different doses of dexmedetomidine combined with lidocaine and bupivacaine during retrobulbar anesthesia for cataract extraction by phacoemulsification.

Materials and Methods

This study was done on forty patients with cataract. The patients were enrolled in two groups: Group (A):Twenty patients were received 1.5 ml 2% lidocaine + 1.5 ml 0.5% bupivacaine + 0.25 μg/kg of dexmedetomidine and Group (B): Twenty patients were received 1.5 ml 2% lidocaine + 1.5 ml 0.5% bupivacaine + 0.5 μg/kg of dexmedetomidine.

Results

The globe anesthesia duration, globe, and lid akinesia were significantly longer in the Group B than in the Group A (P < 0.05). Intraocular pressure decreased through the first 15 min after anesthesia in the two groups, and the changes were not significant between the two groups but highly significant in every group when compared to its baseline reading. As regards the conscious level in the two groups, there was a significant difference (P < 0.001). Group A is higher regarding score 2 and 3, and Group B higher in score 4.

Conclusions

We concluded that dexmedetomidine 0.25 μg/kg, when added to retrobulbar block for cataract surgery, will significantly increase the duration of retrobulbar block and improve both the surgeon and the patient satisfaction.

Surdity in the OR: An Unusual Case of Brainstem Anesthesia

Brainstem anesthesia is a potentially life-threatening complication of regional ophthalmic anesthesia. This case report chronicles an unusual presentation of brainstem anesthesia following an eye block. The unique features of this case were the presenting symptoms of deafness and slurred speech in the absence of loss of consciousness, respiratory depression, or contralateral ophthalmoplegia. This report underscores two key points: first, the importance of ongoing patient monitoring after performance of an eye block; second, the exigency of supportive therapy in suspected cases of brainstem anesthesia.

Comparison of Olive Tipped and Conventional Steven's Cannula for Sub-Tenon Ophthalmic Anesthesia

PURPOSE:

To compare the efficacy of the olive tipped (OT) cannula to the conventional Steven's cannula for sub-Tenon block (STB) before cataract surgery.

METHODS:

This prospective, randomized, double-masked compared STB delivered in cataract surgery patients with an OT cannula or a conventional Steven's cannula (ST). Outcome variables included the akinesia score and lid movement scores at 5 and 10 min. The patient perception of pain during delivery of the STB and surgery were also compared between groups. Surgeon satisfaction with anesthesia was compared between groups. P <0.05 was statistically significant.

RESULTS:

There were sixty patients in each group. The age between groups was not statistically different (P = 0.4). The body mass index was higher in the ST group compared to the OT group (P < 0.001). The akinesia score at 5 and 10 min did not differ between groups (P = 0.07 and P = 0.6, respectively). The patient perception of pain during STB and surgery were similar between groups (P = 0.1 and P = 0.06, respectively). There were six patients with mild chemosis and redness in the OT group and 15 patients in the ST group.

CONCLUSION:

An OT cannula is equally effective as the conventional Steven's cannula for delivering STB anesthesia before cataract surgery.

Visual evoked potentials in the horse

BACKGROUND

Electrical potentials generated in the central nervous system in response to brief visual stimuli, flash visual evoked potentials (FVEPs), can be recorded non-invasively over the occipital cortex. FVEPs are used clinically in human medicine and also experimentally in a number of animal species, but the method has not yet been evaluated in the horse. The method would potentially allow the ophthalmologist and equine clinician to evaluate visual impairment caused by disorders affecting post-retinal visual pathways. The aim was to establish a method for recording of FVEPs in horses in a clinical setting and to evaluate the waveform morphology in the normal horse.

METHODS

Ten horses were sedated with a continuous detomidine infusion. Responses were recorded from electrodes placed on the scalp. Several positions were evaluated to determine suitable electrode placement. Flash electroretinograms (FERGs) were recorded simultaneously. To evaluate potential contamination of the FVEP from retinal potentials, a retrobulbar nerve block was performed in two horses and transection of the optic nerve was performed in one horse as a terminal procedure.

RESULTS

A series of positive (P) and negative (N) peaks in response to light stimuli was recorded in all horses. Reproducible wavelets with mean times-to-peaks of 26 (N1), 55 (P2), 141 (N2) and 216 ms (P4) were seen in all horses in all recordings. Reproducible results were obtained when the active electrode was placed in the midline rostral to the nuchal crest. Recording at lateral positions gave more variable results, possibly due to ear muscle artifacts. Averaging ≥100 responses reduced the impact of noise and artifacts. FVEPs were reproducible in the same horse during the same recording session and between sessions, but were more variable between horses. Retrobulbar nerve block caused a transient loss of the VEP whereas transection of the optic nerve caused an irreversible loss.

CONCLUSIONS

We describe the waveform of the equine FVEP and our results show that it is possible to record FVEPs in sedated horses in a clinical setting. The potentials recorded were shown to be of post-retinal origin. Further studies are needed to provide normative data and assess potential clinical use.

Comparison of orbital muscle akinesia caused by rocuronium versus hyaluronidase mixed to the local anesthetic in single injection peribulbar block for cataract surgery

Background:

The aim of this study was to compare orbital muscle akinesia caused by rocuronium versus hyaluronidase when mixed with the local anesthetic in single-injection peribulbar anesthesia (PBA).

Patients and Methods:

Sixty patients were included in the study and subjected to cataract extraction using phacoemulsification technique with intraocular lens implantation. Group I received peribulbar block with 5 ml mixture of 30 IU/ml hyaluronidase and 2% lidocaine. Group II received peribulbar block with 5 ml mixture of rocuronium 5 mg and 2% lidocaine. The onset and duration of akinesia were assessed; the akinesia score at 2, 5, and 10 min was measured after injection. The need for supplementary injection was also recorded.

Results and Conclusion:

PBA using a mixture of rocuronium and lidocaine provides optimal globe akinesia and faster establishment of suitable conditions to start eye surgery and shortens the block onset time as compared with the addition of hyaluronidase to lidocaine.

Anatomy of anterior ethmoidal foramen, medial canthal tendon, and lacrimal fossa for transcutaneous anterior ethmoidal nerve block in Japanese individuals

PURPOSE

To examine the anatomical relationships of the anterior ethmoidal foramen (AEF), medial canthal tendon (MCT), and lacrimal fossa (LF) in Japanese individuals.

METHODS

Thirty-eight orbits from 19 Japanese cadavers (7 men and 12 women; average age at death, 89.3 years) were used in this experimental anatomical study. The AEF, MCT, and superior border of the LF were exposed. The following distances were then measured: 1) from the point at the medial orbital rim directly anterior to the AEF to the superior border of the MCT (AEF-MCT), and 2) from the superior border of the LF to the superior border of the MCT (LF-MCT).

RESULTS

(AEF-MCT) and (LF-MCT) distances were 9.40±1.92 (mean±standard deviation) and 4.21±1.18 mm, respectively. No values of (LF-MCT) exceeded the mean (AEF-MCT) (9.40 mm).

CONCLUSIONS

The transcutaneous anterior ethmoidal nerve block can be reliably performed without injury to the lacrimal sac by inserting a needle approximately 9 mm superior to the superior border of the MCT.

Ophthalmic regional anaesthesia: A review and update

Local anaesthetic techniques are increasingly popular for ophthalmic surgery. It is now being provided mainly by anaesthesiologists and varies from an akinetic injection technique to a non-akinetic topical technique. Each technique has its own risk/benefit profile, and proven to be highly successful if performed correctly. The choice of the technique should be individualized based upon specific needs of the patient, the nature and extent of eye surgery, and the anaesthesiologist's and surgeon's preferences and skill. This review article attempts to outline the orbital anatomy, discuss the commonly used agents, current method of pre-operative preparation, available clinical techniques and their inherent complications.

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.

Ophthalmic regional blockade complication rate: a single center audit of 33,363 ophthalmic operations

STUDY OBJECTIVE

To determine the incidence and contributing factors of complications for patients receiving regional ophthalmic anesthesia.

DESIGN

Retrospective analysis.

SETTING

Tertiary-care eye center.

MEASUREMENTS

Anesthesia records of ophthalmic blocks performed from January 2003 to June 2009 were reviewed. The frequency of block-related complications and details of each complication were recorded.

MAIN RESULTS

A total of 33,363 peribulbar blocks were performed, with a total incidence of 0.12% (41 cases). These complications may be divided into systemic complications, 18 cases (0.053%) and needle-related complications, 23 cases (0.068%).

CONCLUSION

Peribulbar block complications were rare. In this series, experience of caregivers and axial and needle length were not contributing factors.

Single-injection percutaneous peribulbar anesthesia with a short needle versus sub-Tenon's anesthesia for cataract extraction

Purpose:

This study compared the efficacy of single-injection percutaneous peribulbar anesthesia (PBA) with a short needle with sub-Tenon's anesthesia (STA) to produce optimal operating conditions for cataract extraction in patients with complicated cataract.

Methods:

Two hundred patients with complicated cataract were enrolled in this prospective, double-blinded, randomized study. Adequate akinesia was a surgical requisite for all cases included in the study because of the expected difficult surgery. The patients were divided into two equal groups to receive either peribulbar anesthesia (PBA) with a 16-mm needle or sub-Tenon's anesthesia. Surgical akinesia (as a primary end point), analgesia, incidence of complications, as well as patient and surgeon satisfaction (as secondary end points) were assessed.

Results:

Both techniques provided similar analgesia during the operation and similar rates of incidence of chemosis with no serious complications; while the PBA group provided higher degree of akinesia 10 minutes after injection of the local anesthetic, a lower incidence of subconjunctival hemorrhage (SCH) and higher patient and surgeon satisfaction compared to the STA group.

Conclusion:

We concluded that when globe akinesia is necessary during surgery, the single-injection technique for percutaneous peribulbar anesthesia with a short needle proved to be more suitable than the STA in providing akinesia for cataract surgery. Also, this PBA technique demonstrated a lower incidence of SCH and was preferred to STA by the patients and surgeon.

Overview of ocular anesthesia: past and present

PURPOSE OF REVIEW

Many choices of ocular anesthetic techniques are available to the ophthalmologist. This study reviews currently used techniques of topical, subconjunctival and regional block anesthesia used in ophthalmic procedures.

RECENT FINDINGS

The choices of anesthetics that are available are considered and a new ocular anesthetic gel is described that provides sustained ocular surface anesthesia, minimal side-effects and may also have antimicrobial properties.

SUMMARY

Consideration of ocular anesthetic techniques and anesthetic choice plays a critical role for the success and safety of ophthalmic surgery.

Sub-Tenon's anaesthesia: complications and their prevention

The advent of a new technique that is considered much safer than previously established one leads to its rapid adoption. This usually leads to the identification of previously unreported complications of the new technique, and a re-assessment of its position in clinical care, which is precisely the state of play with the sub-Tenon's block. The sub-Tenon's block was introduced into the clinical practice in early 1990. A systematic recent search of subject headings such as complications of sub-Tenon's block, subtenon, orbital block, orbital block complications, and orbital anaesthesia was performed in Medline, EMBASE, and Cochrane database. Indeed there are complications of sub-Tenon's block published as case reports and the exact incidence of these complications is not known. Management and preventive measures of these complications are described. Although the sub-Tenon's block appears to be relatively safer than needle-based blocks but a proper prospective, randomized, double-blind controlled trial is essential for scientific proof that sub-Tenon's block is better than needle-based blocks.

Needle-based blocks for the 21st century ophthalmology

PURPOSE

This paper reviews history of the needle orbital blocks used in the earlier centuries and how they have evolved towards safer anaesthesia in the modern clinical practice.

METHODS

Material is derived from literature searches from major ophthalmic and anaesthetic journals on the use of orbital needle blocks over earlier centuries.

RESULTS

Needle-based anaesthetic techniques were described shortly after the invention of reliable medical needles. Atkinson popularized the classical retrobulbar block in a series of papers published in the early 20th century. This technique,which utilises a relatively long needle inserted towards the apex of the muscle cone behind the globe, has been criticized by some as unsuitable for modern 21st century ophthalmic surgery because of the extremely rare potential for serious complications. Satisfactory anaesthesia and akinesia can be obtained with short sharp or dull needles with slightly higher volumes of local anaesthetic agent placed in the farthest inferotemporal quadrant.

CONCLUSION

Aside from relative safety, modern needle blocks offer the advantage of lid akinesia without a need for a second injection for the seventh nerve that is often performed con-comitantly with retrobulbar block.

Superficial extraconal blockade for vitreoretinal surgery

Context:

Needle length plays an important role for the success of ophthalmic block. The standard practice is to use 25 mm needles length; however, unnecessarily long needles may increase the risk of complications especially in the presence of staphyloma or previous scleral buckle.

Aims:

This work was designed to compare the efficacy of using 15 and 25 mm needle in performing extraconal block for patients undergoing vitreoretinal surgery.

Settings and Design:

Prospective randomized double blinded study.

Materials and Methods:

A total of 120 patients were enrolled in this study and were divided in two groups. In group (1) extraconal block was performed using 25 mm needle, while in group (2) 15 mm needle was used. After primary injection, assessment of the block was done by an anesthesiologist who was unaware of the needle used. If satisfactory akinesia was not achieved a supplementation was provided. At the end of the procedures, patients and surgeons were asked to assess their pain and satisfaction with the anesthetic technique.

Statistical Analysis used:

The sample size calculation using N-Quary version 4. Numerical and categorical data were analyzed using an independent sample, a two-tailed t-test, and chi-square test, respectively.

Results:

The volume of primary injectable was significantly higher in group 2. The two groups were comparable as regards total volume of local anesthetic, supplementation rate, akinesia, pain score, and surgeon satisfaction.

Conclusions:

Using 15 mm needle length to perform extraconal blockade for posterior segment procedures is equally effective to 25 mm needle.

Sub-Tenon's anaesthesia: a well tolerated and effective procedure for ophthalmic surgery

PURPOSE OF REVIEW

To report recent advancements with sub-Tenon's anaesthesia for ocular surgery, accentuating the efficacy and safety of this technique. Further clinical implications are reviewed with regard to its technique, indications, benefits, and reported complications.

RECENT FINDINGS

Sub-Tenon's anaesthesia, a versatile and technically easy procedure to master, has gained popularity with both ophthalmic surgeons and anaesthetists. This block is achieving repute as the block of choice, providing anaesthesia as well as akinesia during ophthalmic surgery. As the technique has further evolved and novel cannulae introduced, increasing complications have been documented.

SUMMARY

Currently, there is no absolutely well tolerated orbital regional block technique. However, well founded evidence appears to support sub-Tenon's block as a safer option. Sound knowledge of orbital anatomy, pharmacology of anaesthetic agents, and prevention of potential complications are therefore crucial to perform sub-Tenon's block effectively and safely.

Real-time visualization of ultrasound-guided retrobulbar blockade: an imaging study

BACKGROUND

Retrobulbar anaesthesia allows eye surgery in awake patients. Severe complications of the blind techniques are reported. Ultrasound-guided needle introduction and direct visualization of the spread of local anaesthetic may improve quality and safety of retrobulbar anaesthesia. Therefore, we developed a new ultrasound-guided technique using human cadavers.

METHODS

In total, 20 blocks on both sides in 10 embalmed human cadavers were performed. Using a small curved array transducer and a long-axis approach, a 22 G short bevel needle was introduced under ultrasound guidance lateral and caudal of the eyeball until the needle tip was seen 2 mm away from the optic nerve. At this point, 2 ml of contrast dye as a substitute for local anaesthetic was injected. Immediately after the injection, the spread of the contrast dye was documented by means of CT scans performed in each cadaver.

RESULTS

The CT scans showed the distribution of the contrast dye in the muscle cone and behind the posterior sclera in all but one case. No contrast dye was found inside the optic nerve or inside the eyeball. In one case, there could be an additional trace of contrast dye behind the orbita.

CONCLUSIONS

Our new ultrasound-guided technique has the potential to improve safety and efficacy of the procedure by direct visualization of the needle placement and the distribution of the injected fluid. Furthermore, the precise injection near the optic nerve could lead to a reduction of the amount of the local anaesthetic needed with fewer related complications.