Sub-Tenon's anaesthesia for modern eye surgery-clinicians' perspective, 30 years after re-introduction

Retinal artery occlusion after ophthalmic surgery under regional anaesthesia: A narrative review

Two recent cases of central retinal artery occlusion under otherwise uncomplicated sub-Tenon's block that resulted in significant visual loss after cataract surgery prompted us to undertake a literature review of such cases. We identified 97 cases of retinal artery occlusion after ophthalmic surgery under regional anaesthesia that had no immediate signs of block-related complications. These occurred after various intraocular (87%) and extraocular (13%) operations, across a wide range of ages (19-89 years) on patients with (59%) or without (39%) known risk factors. The anaesthetic techniques included 40 retrobulbar blocks, 36 peribulbar blocks, 19 sub-Tenon's blocks, one topical anaesthetic and one unspecified local anaesthetic. Different strengths of lidocaine, bupivacaine, mepivacaine and ropivacaine, either alone or in various combinations, were used. The details of the anaesthetic techniques were often incomplete in the reports, which made comparison and analysis difficult. Only nine cases had their cause (optic nerve sheath injury) identified, while the mechanism of injury was unclear in the remaining patients. Various mechanisms were postulated; however, the cause was likely to be multifactorial due to patient, surgical and anaesthetic risk factors, especially in those with compromised retinal circulation. As there were no definite risk factors identified, no specific recommendations could be made to avoid this devastating outcome. We have provided rationales for some general considerations, which may reduce this risk, and propose anaesthetic options for ophthalmic surgery on the fellow eye if required, based both on our literature review and our personal experience.

Long-Acting Ocular Injectables: Are We Looking In The Right Direction?

The complex anatomy and physiological barriers of the eye make delivering ocular therapeutics challenging. Generally, effective drug delivery to the eye is hindered by rapid clearance and limited drug bioavailability. Biomaterial-based approaches have emerged to enhance drug delivery to ocular tissues and overcome existing limitations. In this review, some of the most promising long-acting injectables (LAIs) in ocular drug delivery are explored, focusing on novel design strategies to improve therapeutic outcomes. LAIs are designed to enable sustained therapeutic effects, thereby extending local drug residence time and facilitating controlled and targeted drug delivery. Moreover, LAIs can be engineered to enhance drug targeting and penetration across ocular physiological barriers.

Inflammatory signal transduction pathways induced by prilocaine toxicity in cultured ARPE-19 cells

Prilocaine (PRL) is a common local anesthetic. Despite the successful use of regional anesthesia for intraocular surgery, there are associated side effects that may affect the retina in case of accidental intravitreal injection. This study examined the signal transduction pathways activated by PRL toxicity and determined the protective role of nitric oxide synthase-2 (NOS2) inhibition in cultured human-derived retinal pigment epithelial cells (ARPE-19). Toxicity analysis was performed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay to detect the toxic dose of PRL and protective effectiveness of asperglaucide (ASP), an NOS2 inhibitor. Nuclear factor kappa B p65 (NF-κB p65), phosphorylated NF-κB p65, phospho-protein kinase B (AKT), NOS2, nitrotyrosine, and cleaved caspase-3 protein levels were evaluated by immunofluorescence staining and/or western blot analysis. Interleukin-6 (IL-6) and nitrated protein levels were quantified using an immunoassay, whereas caspase-3 activity and nitrite/nitrate levels were measured using a fluorometric method. A significant increase in NF-κB p65, and phosphorylated NF-κB p65 and AKT levels due to PRL toxicity was observed. Similarly, IL-6, NOS2, nitrite/nitrate, and nitrotyrosine levels were significantly higher in PRL-treated cells than in control cells. Application of ASP to PRL-treated cells reduced NF-κB p65, and phosphorylated NF-κB p65 and AKT to basal levels. IL-6, NOS2, nitrite/nitrate, and nitrotyrosine levels also considerably decreased following ASP treatment in cells experiencing PRL-induced toxicity. Moreover, the caspase-3-dependent apoptotic pathway was not activated. Our results indicate that ASP could ameliorate PRL-induced activation of NF-κB p65 that led to inflammation in cultured ARPE-19 cells.

Safety and feasibility of sutureless pars-plana vitrectomy in sub-Tenon anesthesia (SAFE-VISA): a prospective study

BACKGROUND

To determine the safety and feasibility of sutureless pars-plana vitrectomy (ppV) in sub-Tenon anesthesia.

METHODS

In this prospective study. Pain and anxiety at various times after ppV using a visual analogue scale (VAS) and Wong-Baker-FACES scale as well as visual sensations during surgery were investigated. The surgeon evaluated motility, chemosis, overall feasibility.

RESULTS

ppV was performed on 67 eyes (33 sub-Tenon anesthesia, 34 general anesthesia). Pain during surgery in sub-Tenon anesthesia was 1.8 ± 2.2 (0.0-8.0), anxiety was 2.3 ± 2.2 (0.0-8.5). There was a moderate correlation between pain and anxiety (R2 = 0.58). Comparing sub-Tenon and general anesthesia no difference in pain perception was found the day after surgery. 27.3% of patients saw details, 21.2% saw colors, 90.1% saw light/motion perception, 3.0% had no light perception. Median chemosis after surgery was 1.0 (IQR = 1.0). Median motility of the eye during surgery was 1.0 (IQR = 1.0), median grade was 1.0 (IQR = 1.0). 24.2% of patients showed subconjunctival hemorrhage during or after surgery.

CONCLUSIONS

Sutureless pars-plana vitrectomy in sub-Tenon anesthesia was performed safely, with pain and anxiety levels tolerable for the patients and without the necessity for presence of an anesthesiologist. With 88.9% of patients willing to undergo vitreoretinal surgery in sub-Tenon anesthesia again, we recommend it as a standard option. Trial registration This study was approved by the Institutional Ethical Review Board of the RWTH Aachen University (EK 111/19). This study is listed on clinicaltrials.gov (ClinicalTrials.gov identifier: NCT04257188, February 5th 2020).

Role of hyaluronidase as an adjuvant in local anesthesia for cataract surgery

Cataract surgery ranks among the commonest procedures performed worldwide. Approximately 51% of blindness worldwide is related to cataracts, affecting about 65.2 million people worldwide and more so in developing countries. Over the years, there has been a significant evolution in the surgical techniques of cataract extraction. The advancement in phacoemulsification machines, phaco-tips, and the availability of ophthalmic viscoelastic devices have played a substantial role in cataract surgery such that they are faster and more controlled than before. Similarly, anesthetic techniques in cataract surgery have advanced significantly from retrobulbar, peribulbar, and sub-Tenon's blocks to topical anesthesia. Though topical anesthesia eliminates the possible complications of injectable anesthesia, it is not suitable for use in uncooperative, anxious patients, pediatric age groups, and patients with cognitive disabilities. Hyaluronidase is an enzyme that breaks down hyaluronic acid in the retrobulbar tissue, facilitating uniform diffusion of the anesthetic drug and hastening the onset of anesthesia and akinesia. Hyaluronidase has been used in the last 80 years successfully as an adjuvant in retrobulbar, peribulbar, and sub-Tenon's blocks. Initially, the hyaluronidase enzyme was animal-derived and of bovine and ovine sources. Recombinant human-derived hyaluronidase, which has lesser allergic reactions, impurities, and toxicity, is now available. There is conflicting evidence regarding the efficacy of hyaluronidase as an adjuvant in retrobulbar and peribulbar blocks. This article summarizes a brief review of the literature on the role of hyaluronidase as an adjuvant in local anesthetic blocks in ophthalmic surgeries.

Anaesthetic considerations for the surgical management of ocular hypotony in adults

Ocular hypotony can occur from many causes, including eye trauma, ophthalmic surgery and ophthalmic regional anaesthesia-related complications. Some of these patients require surgical intervention(s) necessitating repeat anaesthesia. While surgical management of these patients is well described in the literature, the anaesthetic management is seldom discussed. The hypotonous eye may also have altered globe anatomy, meaning that the usual ocular proprioceptive feedbacks during regional ophthalmic block may be altered or lost, leading to higher risk of inadvertent globe injury. In an 'open globe' there is a risk of sight-threatening expulsive choroidal haemorrhage as a consequence of ophthalmic block or general anaesthesia. This narrative review describes the physiology of aqueous humour, the risk factors associated with ophthalmic regional anaesthesia-related ocular hypotony, the surgical management, and a special emphasis on anaesthetic management. Traumatic hypotony usually requires urgent surgical repair, whereas iatrogenic hypotony may be less urgent, with many cases scheduled as elective procedures. There is no universal best anaesthetic technique. Topical anaesthesia and regional ophthalmic block, with some technique modifications, are suitable in many mild-to-moderate cases, whilst general anaesthesia may be required for complex and longer procedures, and severely distorted globes.

Sub-Tenon's bupivacaine injection is superior to placebo for pediatric strabismus surgery: A meta-analysis

BACKGROUND

The effect of post-operation sub-Tenon's bupivacaine injection for pediatric strabismus surgery is controversial. The objective of this meta-analysis is to compare the outcome of sub-Tenon injection of bupivacaine and placebo duringstrabismus surgery.

METHODS

We searched the databases (Pubmed, Cochrane library and EMBASE) and reference lists systematically. Randomized controlled trials (RCTs) comparing sub-Tenon's bupivacaine and placebo injection for pediatric strabismus surgery were included. The methodological quality was evaluated by the Cochrane risk of bias (ROB) tool. Outcome measurements were pain score, oculocardiac reflex (OCR), additional drug consumption and related complications. RevMan 5.4 was used for the statistical analysis and graph preparation. For the outcomes that are not suitable for statistical analysis, descriptive analysis was performed.

RESULTS

A total of 5 RCTs with 217 patients were finally identified and analyzed. Sub-Tenon's bupivacaine injection showed pain relief within 30 min after operation. But with the extension of time, the analgesic effect gradually disappeared at 1 h. It can reduce the incidence of OCR, vomiting and supplementary drug requirements. However, in terms of nausea, there is no difference between the two groups.

CONCLUSION

Sub-Tenon's bupivacaine injection can relieve short-term postoperative pain, reduce the incidence of OCR and vomiting, and reduce the use of supplementary drugs in strabismus surgery.

3T high-resolution magnetic resonance imaging, conventional ultrasonography and ultrasound biomicroscopy of the normal canine eye

Background

Advances in MRI coil technology and increased availability of high-field MRI in veterinary medicine enable the acquisition of images of increasingly high spatial resolution while preserving signal-to-noise ratio.The purpose of the present study was to compare 3T high-resolution magnetic resonance imaging (HR-MRI) with ultrasound (US) and ultrasound biomicroscopy (UBM) in the normal canine eye, to assess its potential to depict normal ocular anatomy.

Results

HR-MRI was compared with US and UBM in 10 eyes from 10 healthy beagle dogs. Ocular structures (cornea, anterior chamber, iridocorneal angle, iris, lens, ciliary body, choroid, vitreous body, posterior wall of the eye, optic nerve and optic nerve sheath, extraocular muscles) were assessed subjectively and central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth (AQD), anteroposterior, mediolateral and dorsoventral lens diameter (APLD, MLLD, DVLD), anteroposterior diameter of the globe including and excluding the scleroretinal rim (APDSRR, APD), vitreous chamber depth (VCD) and optic nerve sheath diameter (ONSD) were measured in HR-MRI and in US. Optic nerve diameter (OND) was measured in HR-MRI. HR-MRI and UBM appearance of the anterior segment were subjectively compared. Detailed reference high-resolution MRI images of normal eyes of Beagle dogs are provided.

Conclusions

HR-MRI allowed assessment of all structures identified with US and UBM. The MRI examinations were performed under general anesthesia with the addition of a neuromuscular blocking agent, while US and UBM examinations were performed in conscious animals. Visibility of the entire ocular wall, the lens, the structures caudal to the ciliary body and the optic nerve and its sheath was superior with HR-MRI. HR-MRI allowed the distinction of retina, choroid and sclera, and the delineation of structures not previously identified in canine eyes with MRI, including Tenon’s capsule and the sub-Tenon’s space.Plane selection was more accurate with HR-MRI compared to US. In general, the range of measurements was narrower for MRI than for US. CCT, AQD, APLD, MLLD, APD, APDSRR and ONSD differed significantly between HR-MRI and US, respectively (p = 0.005-0.027).Micro-MRI may be useful for the assessment of ocular pathologies in the future.

Vitreoretinal Surgery Under Sub-Tenon’s Block and Conscious Sedation in a Patient with Brugada Syndrome: A Case Report and Literature Review

Brugada syndrome (BrS), a type of sudden arrhythmic unexpected death syndrome (SADS), is characterized by specific electrocardiogram (ECG) changes, a structurally normal heart, and susceptibility to life-threatening ventricular arrhythmias. General anesthesia (GA) is usually used for major surgery in patients with BrS due to concerns that some local anesthetic agents may precipitate critical arrhythmias. The majority of ophthalmic surgeries are successfully carried out under regional anesthesia (RA). The literature does not address the use of ophthalmic RA in patients with BrS except one report of peribulbar block for glaucoma surgery. This clinical case report and the liertature review suggests that for BrS patients presenting for vitreoretinal surgery, a sub-tenon block, with or without sedation may safely be used as a primary anaethestic technique.

Effect of adding clonidine to lidocaine on ocular hemodynamics during sub-Tenon's anesthesia: randomized double-blind study

INTRODUCTION AND OBJECTIVES

Different regional anesthesia techniques for ophthalmology can have hemodynamic effects on the eye. We assessed the effects of adding clonidine to lidocaine on Intraocular Pressure (IOP), Ocular Pulse Amplitude (OPA), and Ocular Perfusion Pressure (OPP) after the sub-Tenon's technique for cataract surgery.

METHODS

The study included 40 patients randomly allocated into two groups: sub-Tenon's blockade with Lidocaine plus Saline Solution (LS) or Lidocaine plus Clonidine (LC). IOP, OPA and OPP were measured before anesthesia, and 1, 5 and 10 minutes after the injection of anesthetic solution.

RESULTS

There was no difference between the groups in IOP, OPA, and OPP baseline values. After the injection of the anesthetic solution, the IOP increased in both groups at minute one, with a mean difference of +4.67 mmHg (p = 0.001) and +2.15 mmHg (p = 0.013) at 5 minutes. The increase was lower in the LC group when compared to LS (p = 0.027). OPA decreased in both groups, with a baseline difference, after 1 minute, of -0.85 mmHg (p =  -0.85 mmHg (p = 0.001), and at 5 and 10 minutes with differences of -1.17 (p = 0.001) and -0.89 mmHg (p = 0.001), respectively. The highest decrease was observed in group LC in relation to group LS (p = 0.03). There was no difference in OPP in relation to baseline measurements.

CONCLUSIONS

Adding clonidine to lidocaine for sub-Tenon's anesthesia reduced IOP and OPA without significant changes in OPP.