A review of sub-Tenon's block

Evaluation of magnesium sulfate as an adjuvant in sub-Tenon anesthesia for cataract surgery: A prospective, randomized controlled trial

Purpose

To evaluate the efficacy, safety, and satisfaction for the use of adjuvant; magnesium sulfate (MgSO4) in sub-Tenon anesthesia for cataract surgery.

Methods

This single centered randomized, double blind trial was held in 2021 after approval of ethical committee at the Eye Hospital, Riyadh, Saudi Arabia. Cataract patients to be operated using local anesthesia were randomly assigned to two groups; Group magnesium sulfate (MS) received 50 mg/0.5 ml of magnesium sulfate and Group normal saline (NS) received 0.5 ml of normal saline added to the standard mixture, respectively. Absence of eyelid dropping and akinesia of the globe at different time after anesthesia were considered as ineffective anesthesia. The age and sex-adjusted generalized estimating equation (GEE) analysis was carried out. Complications, patient's and surgeon's satisfaction were also compared.

Results

Each group had 100 cataract patients. Effectiveness of block was not significantly different in two groups (adjusted odds ratio, 0.90; 95% confidence interval [CI], 0.62, 1.31; P = 0.594). The likelihood of "no eye-opening" significantly increased with time (adjusted odds ratio, 1.26; 95% CI, 1.18-1.34; P < 0.001). Subconjunctival bleeding was significantly higher in the MS versus NS Group (36 of 98 [36.7%] vs. 11 of 102 [10.8%], P < 0.001). Chemosis was not significantly different between the groups (P = 0.95). Patient's satisfaction score was very good (9/10) but slightly higher in NS group than MS (P = 0.001) while surgeon's satisfaction score was similar in both groups (P = 0.149).

Conclusions

Although safe, adding 50 mg of magnesium sulfate did not improve the effect of sub-Tenon anesthesia for cataract surgery. Risk of subconjunctival bleeding was higher in cataract patients operated using MgSO4 compared to those managed with the conventional sub-Tenon anesthetic.

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.

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.

Contact topical anesthesia for strabismus surgery in adult patients

OBJECTIVE

To analyze the effectiveness and usefulness of contact topical anesthesia in strabismus surgery in adult patients.

MATERIAL AND METHODS

A prospective study was conducted on 20 patients undergoing strabismus surgery using contact topical anesthesia and sedation with remifentanil. The intensity of pain was recorded using a numeric pain rating scale at the time of anesthesia implementation, during the surgical procedure, 30 min afterwards, and during the first postoperative day. The incidence of oculocardiac reflex, postoperative nausea and vomiting, corneal ulcers, patient satisfaction (numerically from 0 to 10) and the degree of residual ocular deviation were also assessed.

RESULTS

The operation was performed successfully in all patients. Average pain intensity was 1.40 ± 1.73 during anesthesia implementation, 4.20 ± 2.57 during the surgical procedure, 2.50 ± 2.54 30 min after surgery, and 3.55 ± 2.89 during the first postoperative day. Oculocardiac reflex was observed in 7 patients (35%), postoperative nausea and vomiting in 4 (20%), and corneal ulcer in 4 (20%). The patient satisfaction was 9.53 ± 2.51. More than two-thirds (70%) of patients had a residual ocular deviation less than 10 prism diopters.

CONCLUSIONS

Contact topical anesthesia is a safe and effective alternative for strabismus surgery in adult patients. Contact topical anesthesia provides adequate pain control, lower incidence of postoperative nausea and vomiting and oculocardiac reflex, and optimal setting of ocular alignment.

Comparison of Topical Versus Sub-Tenon's Anesthesia in Phacoemulsification at a Tertiary Care Eye Hospital

PURPOSE

To compare the effectiveness of topical and sub-Tenon's anesthesia in providing pain relief during phacoemulsification.

METHODS

This randomized controlled trial was carried out at a tertiary eye care hospital, Coimbatore, Tamil Nadu, India. Patients who underwent phacoemulsification through self-sealing clear corneal incision with foldable intra-ocular lens implantation were randomized into two groups. Group 1 (n = 100) received topical anesthesia with 0.5% proparacaine (Paracaine, Sunways India Pvt. Ltd., India) drops. Group 2 (n = 100) received sub-Tenon's infiltration with 2% lignocaine (Xylocaine, AstraZeneca Pharma India Pvt. Ltd., India). As per study criteria, patients graded the pain during administration of anesthesia, during surgery and after surgery on a visual analogue pain scale. The surgeon graded overall patient co-operation. The complications were also noted. Data analysis was performed using Statistical Package for Social Sciences version 11. Student's t-test and Chi-square test were used for comparison of variables between the groups.

RESULTS

Sub-Tenon's anesthesia provided statistically significant better intra-operative pain relief and patient satisfaction than topical anesthesiat. No statistically significant difference was noted between the two groups regarding pain during administration, postoperative pain, and surgeon satisfaction.

CONCLUSION

Sub-Tenon's anesthesia provides better pain relief than topical anesthesia during phacoemulsification.

[Simplified anesthesia protocol for cataract surgery under topical anesthesia: one year retrospective study]

INTRODUCTION

The reduced supply of anesthesiologists in the hospital setting calls for a reconsideration of anesthesia management for ophthalmology patients. Therefore, a simplified management protocol has been designed through close collaboration between the involved specialists for cataract surgery under topical anesthesia (anesthetic eye drops or sub-Tenon's injection).

MATERIALS AND METHODS

At the conclusion of the visit confirming the need for surgery, the surgeon completes a questionnaire designed to elicit a history of the presence of diabetes mellitus (type I or II), prior organ transplantation, chronic renal insufficiency requiring dialysis, communication difficulties, psychiatric disorders, allergy and/or a complex cataract. If one of the items is positive, the patient is scheduled for a preoperative anesthesia consult. If all the items are negative, this anesthesia evaluation is waived. The surgeon explains the fasting requirement and how to take the patient's usual medications on the morning of surgery. The patient continues his/her medications. No lab tests or chest X-ray are performed. If necessary, the surgeon prescribes preoperative antibiotic prophylaxis and any other preparation. During the surgery, the patient receives IV fluids and is monitored via EKG, non-invasive blood pressure and pulse oxymetry by a certified nurse anesthetist. The anesthesiologist on duty (one per every four rooms) is immediately available for the slightest problem. The surgeon signs the postoperative anesthesia note and discharge order.

RESULTS

This procedure was assessed by one surgeon over a one year period, including 145 patients (60% of the patients recruited for this surgery), primarily outpatient (77%) under topical anesthesia (Oxybuprocaine(®)+Visthesia(®), Zeiss) or under sub-Tenon's injection (Xylocaïne(®)). No major complications were observed. Seven cases of arterial hypertension, treated with calcium channel blockers (nicardipine), and three episodes of brief anxiety were observed.

CONCLUSION

This simplified anesthesia protocol appears to be safe and effective but requires more demanding involvement of the surgeon, whose scope of competence and responsibility must naturally increase. This is the only way by which cataract surgery can remain competitive.

Are ocular injection anesthetic blocks obsolete? Indications and guidelines

PURPOSE OF REVIEW

In this era of topical anesthesia for ocular surgery, anesthetic ocular blocks are still important when profound anesthesia and akinesia are required. Although injection ocular blocks, retrobulbar and peribulbar anesthesia, have been supplanted for most ocular surgery in many centers by sub-Tenon's irrigation block because of its superior safety profile, still worldwide, injection blocks remain popular.

RECENT FINDINGS

We present here the results of a survey of the literature published over the last 5 years to assess current international preferences for ocular anesthesia injection blocks. We discuss the reasons why sub-Tenon's anesthesia is not more universally popular and advocate for its greater acceptance because of safety. Specific narrow indications for performing injection ocular blocks are presented. Also, guidelines for performing retrobulbar anesthesia which reduce the risk of serious ocular complications are provided as well as our rationale for preferring retrobulbar to peribulbar anesthesia.

SUMMARY

Sub-Tenon's block should be performed in the operating theatre in preference to retrobulbar or peribulbar anesthesia except for limited indications. When injection ocular block is deemed necessary, we feel that retrobulbar anesthesia with the technique described may be safer than peribulbar anesthesia.

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.

Local anesthesia for cataract surgery

Various aspects of local anesthesia for cataract surgery, such as the anesthetic agents and their interaction with ocular nerve supply, anesthesia requirements, available clinical techniques and their inherent complications are reviewed. A comparative evaluation of clinical techniques in terms of efficacy, akinesia, and patient-perceived pain during both anesthesia administration and intraoperative cataract surgery is presented, along with the prevailing practice patterns of anesthesia techniques among refractive surgeons in the United Kingdom and United States. More randomized clinical trials are needed to facilitate statistical methods of metaanalysis to establish convincingly the overall benefits and efficacy of the various local anesthesia procedures in cataract surgery. The wide scope of the present review is of relevance in structuring ophthalmology and anesthesia specialist training programs for junior staff.

Anesthetic management of ophthalmic surgery

Ophthalmic surgery presents challenges for the anesthesiologists, including control of intraocular pressure, prevention and management of the oculocardiac reflex. In addition to understanding ocular anatomy and physiology, the anesthesiologists must have possess technical expertise and knowledge of ophthalmic drug's systemic effects. Patients undergoing ophthalmic surgery have extremes of age and several medical diseases, like as hypertension, diabetes mellitus, coronary heart disease, chronic renal failure, and chronic obstructive lung disease. Anesthesiologist should be knowledgeable about the content as stated above to perform safe and desirable anesthesia for ophthalmic surgery.

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.

[Impact of hyaluronidase on anesthetic distribution in retrobulbar region following sub-Tenon anesthesia]

BACKGROUND/AIM

Sub-Tenon's block is nowadays commonly used in ophthalmic surgery because of its safety and efficacy. The aim of this study was to investigate the distribution of the anaesthetic solution with different amounts of hyaluronidase in the retrobulbar space, following an injection into the Sub-Tenon's space.

METHODS

In this experimental study, 40 pig cadaver heads were used (80 eyeballs). The material was divided into four groups (of 20 eyeballs each). Each group was administered 4.5 ml of a mixture of 2% lignocaine, 0.5% bupivacaine, and 0.5 ml of Indian ink, with different amounts of hyaluronidase--15 IU/ml, 75 IU/ml, 150 IU/ml, except the control one. Samples of retrobulbar tissue were analysed using the standard histopathological procedure. After that, they were also analysed using the Adobe Photoshop program (Windows, USA). The retrobulbar space was divided into eight zones by four perpendicular lines, which crossed in the centre of the optic nerve. The presence of ink in fat and muscle tissues and in the sheath of the optic nerve was observed.

RESULTS

The presence of the local anaesthetic solution was significantly higher in inferonasal and superonasal quadrants of the fat and muscle tissues (p < 0.01). The distribution in optic nerve sheath is similar in each quadrant. Distribution of local anesthetic in each zone of the muscle tissue (I-VIII) was strongly influenced by the amount of hyaluronidase added. In the fat tissue, the distribution of local anesthetic under the influence of hyaluronidase was significantly higher (p < 0.05) in the areas which were distant from the place of injection (I-IV). The distribution in the optic nerve sheath is significantly higher (p < 0.01) in the group with 150 IU/ml of hyaluronidase.

CONCLUSIONS

Following a sub-Tenon block local anaesthetic was present in the retrobulbar space in a high percentage of the cases. The presence of local anaesthetic solution in retrobulbar space depends on the amount of hyaluronidase previously added to the local anaesthetic.

The effect of warming local anaesthetic on the pain of injection during sub-Tenon's anaesthesia for cataract surgery

In a double blind, randomised controlled trial, we examined the effect of warming local anaesthetic solutions on the pain experienced by patients undergoing a sub-Tenon's block for cataract surgery. In all, 140 patients were randomly allocated to receive either local anaesthetic stored at room temperature (control group) or local anaesthetic warmed to 37 degrees C (study group). Pain scores were assessed using a verbal analogue scale from 0 to 10. There was no significant difference in pain scores between the two groups. We conclude that the practice of warming local anaesthetic prior to performing a sub-Tenon's block does not significantly reduce the amount of pain experienced by patients.

Death potentially secondary to sub-Tenon's block

An 82-year-old ASA 2 patient underwent routine sub-Tenon's block for cataract surgery. One minute after injection of the local anaesthetic, the patient had a generalised tonic-clonic seizure and developed refractory ventricular fibrillation; subsequent resuscitation was unsuccessful. With no evidence for intravascular injection, the lack of structural brain abnormalities, and the most striking feature on post mortem examination being severe triple vessel coronary artery disease, it was concluded that this was primarily cardiac in origin; however, the possibility of brainstem anaesthesia should also be considered.

Retrobulbar Alcohol Injection for Orbital Pain Relief Under Difficult Circumstances: A Case Report

Introduction: A case is presented of a patient with severe and chronic pain in the orbital region, which was relieved by retrobulbar injection of absolute alcohol. The management of chronic pain in the orbital region has received little attention and the literature is reviewed. Clinical Picture: A 52-year-old man with adenoid cystic carcinoma of the maxillary sinus was suffering from severe pain, especially in the left orbital region. There was also pain from ocular exposure and compression caused by the tumour. Magnetic resonance imaging (MRI) revealed spread of tumour to both orbits, particularly on the left. Multiple debulking surgery and various treatment modalities offered no relief from his pain. Treatment: A single retrobulbar injection of 2 mL of absolute alcohol, was placed into the putative orbital apex. Outcome: As a consequence of the injection, he had complete resolution of his pain in the 6 months prior to his death. Discussion: Retrobulbar injection of alcohol offers effective pain relief in certain specific conditions characterised by chronic orbital pain when other treatments do not help. Conclusion: We have demonstrated that the retrobulbar technique still has a place in our armamentarium. Key words: Ocular pain, Orbital pain, Orbital pain management, Retrobulbar alcohol injection

Complications of ophthalmic regional blocks: their treatment and prevention

Complications following ophthalmic regional anaesthesia are rare but are reported during both needle (intraconal and extraconal blocks) and blunt cannula (sub-Tenon's block) techniques. At present there is no perfect technique of ophthalmic regional anaesthesia. This article reports on the complications, treatment and prevention of commonly used ophthalmic regional blocks. Thorough knowledge of the measures required to deal with complications when they occur are of paramount importance for safe clinical practice.

A comparison of infero-nasal and infero-temporal sub-Tenon's block

BACKGROUND AND OBJECTIVE

Sub-Tenon's block is usually delivered by the infero-nasal (IN) approach, but occasionally this may not be possible. The infero-temporal (IT) approach has been described, but data is not available on its efficacy.

METHODS

One hundred patients undergoing cataract extraction were randomized to receive an IN or IT sub-Tenon's injection of lidocaine 2% with hyaluronidase 15 IU mL-1. Akinesia was assessed using the Brahma scale at 0, 2, 4, 6 and 8 min. Injection, intraoperative and postoperative pain scores (verbal analogue score, 0-10) were noted, along with the incidence of sub-conjunctival haemorrhage and chemosis.

RESULTS

There were no differences in patient characteristics data, or mean volume of administered local anaesthetic solution (3.3 (SD = 0.4) mL). There were no significant differences between groups in terms of onset of akinesia. Mean akinesia scores at 2, 4, 6 and 8 min were 2.7, 1.1, 0.4 and 0.2 for Group IN, compared to 2.2, 0.9, 0.8 and 0.3 for Group IT. Chemosis occurred in 14 patients in Group IN, compared to 22 in Group IT (P = 0.21).A sub-conjunctival haemorrhage was noted in 14 patients in Group IN and 19 patients in Group IT (P = 0.52). No patients required supplementary injections. Mean pain scores for the injection, intraoperatively and postoperatively were 0.9, 0 and 0 for Group IN, compared to 1.1, 0 and 0 for group IT. The surgeons scored all the blocks as 'good' except for one patient in each group.

CONCLUSIONS

The IT approach provides an equally rapid onset of block, without a significant increase in complications.