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

Ultrasound-guided versus conventional peribulbar anaesthesia in cataract surgery: A randomised controlled study

BACKGROUND

Blind ophthalmic anaesthetic techniques may have serious complications.

AIM

To assess the safety of ultrasound as a guide in ophthalmic blocks.

METHODS

Fifty adult patients undergoing cataract surgery under peribulbar block anaesthesia were randomly assigned to ultrasound-guided and conventional block groups. In the ultrasound-guided block group, a large amount of the standard ultrasound gel was applied to the closed eyelids. The globes were scanned in both sagittal and transverse planes. The patients were asked to look straight ahead with closed eyes without clenching the eyelids. The depth and gain were adjusted before performing the block. The primary outcome was the rate of complications. Secondary outcomes included the volume of injected anaesthetics and surgeon and patients' satisfaction.

RESULTS

The local anaesthetic volume used was not significantly different between the two groups (7.08 ± 1.66 and 6.72 ± 1.97ml). The block onset, time and quality were comparable in both groups. No complications were reported, and there were no significant differences regarding surgeons' or patients' satisfaction with either procedure.

CONCLUSION

The ultrasound-guided local ophthalmic block is as safe as the conventional method. Although its use was not superior to the conventional procedure, direct visualisation with ultrasound may be important to avoid vulnerable structures such as staphylomas.

Comparison of four peribulbar anaesthetic techniques: a preliminary study in equine cadavers

OBJECTIVE

To compare the peribulbar injectate distribution and probability of regional anaesthesia of four peribulbar anaesthetic techniques in equine cadavers.

STUDY DESIGN

Prospective experimental cadaver study.

ANIMALS

A total of 12 isolated equine cadaver heads and 24 eyes.

METHODS

The 24 orbits underwent one of four injection techniques (six orbits each) with a mixture (1:4) of contrast medium and saline (CM): 20 mL ventrolateral peribulbar injection (V-20), 20 mL dorsolateral peribulbar injection (D-20), combined ventrolateral and dorsolateral peribulbar injections 10 mL each (VD-20) or 20 mL each (VD-40). To evaluate and score CM distribution at the base of, within the extraocular muscle cone (EOMC), and around the optic nerve (before and after pressure application to the periorbital area), computed tomography was performed. To assess the probability of achieving locoregional anaesthesia, two criteria were applied and both scored as 'likely', 'possible' or 'unlikely'. To compare CM distribution scores between injection techniques, Kruskal-Wallis analysis of variance was used. Mann-Whitney U test was used for post hoc comparisons between groups when needed. A p value < 0.05 was considered significant.

RESULTS

The CM distribution within the EOMC and around the optic nerve circumference was detected as 'possible' only after pressure application in seven out of 24 orbits (V-20, 3; D-20, 1; VD-40, 3). It was never considered 'likely' either before or after pressure application. The CM distribution at the EOMC base was considered 'likely' to provide regional anaesthesia in 50% (V-20), 0% (D-20), 33% (VD-20), 100% (VD-40) and in 66% (V-20), 16% (D-20), 50% (VD-20), 100% (VD-40) before and after applying pressure, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Complete regional anaesthesia seems more likely using the VD-40 technique, although the authors advise caution due to the risk of potential complications. Future studies are necessary to evaluate the efficacy of the technique in vivo.

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.

Real-time ultrasound-guided retrobulbar block vs blind technique for cataract surgery (pilot study)

Background

Retrobulbar regional eye block aims to ensure eye globe akinesia and anesthesia during ophthalmic surgery, and despite the rarity of occurrence of complications due to the blind needle passage while performing either peribulbar or retrobulbar block, some of them are serious and may be life threatening.

Aim

The aim of this study was to estimate the accuracy and safety of real-time ultrasound-guided retrobulbar regional anesthesia in comparison with the blind technique for cataract surgery.

Design

This was a prospective randomized controlled trial.

Methodology

A total of 30 patients who met the inclusion criteria were registered in our research and were divided into two groups: 15 patients received real-time ultrasound-guided retrobulbar block compared to 15 patients who received the block using the blind technique.

Results

One patient out of the 30 was excluded from the analysis, and no statistically significant differences were observed between the two groups regarding the onset of akinesia, numeric pain rating scores, rate of complications, and degree of patient and physician satisfaction.

Conclusion

There were no statistically significant difference between real-time ultrasound-guided and blind retrobulbar regional eye blocks concerning the onset of action, total volume of injected local anesthetic solution, supplemental injection required, pain scores, and degree of patient satisfaction.

Development of an ultrasound-guided technique for retrobulbar nerve block in dromedary camels: a cadaveric study

OBJECTIVE

Description of an ultrasound (US)-guided technique for retrobulbar nerve blockade in dromedary (Camelus dromedarius) cadavers.

STUDY DESIGN

Prospective experimental cadaveric study that was carried out in three phases: phase I: anatomical dissection and development of US-guided technique; phase II: methylene blue (MB) injection; phase III: contrast medium (CM), US-guided injections with computed tomography (CT) control.

ANIMALS

A total of 36 orbits from 18 heads were obtained from 18 dromedary cadavers.

METHODS

Phase I: anatomical dissections were carried out bilaterally, using two heads to determine needle site placement. Phase II: a US-guided, lateral, in-plane approach using one of three volumes of MB (3, 6, or 9 mL) was evaluated in six heads (four orbits per volume tested) to establish the ideal injection volume. Injections of MB that strongly stained all retrobulbar nerves were considered successful, whereas insufficient MB volumes resulted in weak or no nerve staining. Phase III: US-guided retrobulbar injection with CM was carried out using 20 orbits. Computed tomography was performed after each injection trial to determine the accuracy of needle placement and CM dispersal. An injection was judged to be successful when the CT images revealed that the needle was located within the retractor bulbi muscle cone and the CM reached the target nerves at the orbitorotundum and the optic foramina.

RESULTS

Only injection of 9 mL of MB stained the target nerves sufficiently, whereas there was no or only weak staining with 3 and 6 mL, respectively. Therefore, 9 mL of CM was used for the US-guided injections in phase III. Subsequent CT scans revealed satisfying CM distribution within the ocular muscle cone in 18 of 20 cases (90% success rate).

CONCLUSIONS AND CLINICAL RELEVANCE

US-guided retrobulbar injection in dromedary cadavers is feasible. Further research is required to assess its practicality and usefulness in vivo.

Complication of Peribulbar Block: Brainstem Anaesthesia

Peribulbar block is used to obtain anaesthesia and akinesia of the eye by injecting a local anaesthetic around the musclecone. A patient scheduled for cataract surgery received peribulbar block with 6 mL of 2% lidocaine hydrochloride. Following the injection, confusion, hypotension and dilatation of the contralateral pupil rapidly progressed to loss of consciousness and respiratory arrest. The patient was intubated and mechanically ventilated for 30 min. The patient regained her consciousness, was extubated and transferred to the intensive care unit for further follow-up. Although brainstem anaesthesia because of peribulbar block is very rare, this procedure should be performed with complete monitorisation and resuscitation equipment.

Anatomical landmarks for maxillary nerve block in the pterygopalatine fossa: A radiological study

INTRODUCTION

The aim of this study was to describe the anatomical landmarks for maxillary nerve block in the pterygopalatine fossa. The risk of injury to the skull base and maxillary artery was assessed.

METHODS

This retrospective study was based on the analysis of 61 consecutive computed tomography angiographies obtained from patients suffering from different pathologies. Anatomical relationships between optic canal (OC), foramen rotundum (FR), inferior orbital fissure (IOF) and puncture point (PP) were assessed. A "maxillary section" was virtually carried out on the CTs, following a plane passing through PP, IOF and FR in order to mimic the anaesthesia needle route.

RESULTS

No gender difference was observed except for the PP-OC distance that was longer in men. The mean PP-IOF distance was of 31.9 (± 0.7mm). PP-OC (43.9±0.5) and PP-FR (44.2±0.7) distances increased significantly with the patients height (PP-FR=17.25+0.16×height (cm); PP-OC=20.54+0.13×height (cm)). The route to the skull base was curved, with an angle of 168±1.6° at the FR level. The angle to reach the OC was greater than 7°.

DISCUSSION

With a 35-mm needle length, the probability to reach the IOF was high (79%), while the risk to injure the skull base (2%) and the optical nerve (0%) was low. Artery injuries were only found in 13% of cases. Therefore, a 35-mm needle length allows for the best efficacy/risk ratio in maxillary nerve block.

Retrobulbar chlorpromazine in management of painful eye in blind or low vision patients

OBJECTIVE

To evaluate the results of applying retrobulbar chlorpromazine in the management of patients with painful blind eyes or with very poor vision.

METHODS

A retrospective, descriptive review was carried out on the medical records of 33 patients who were treated with a retrobulbar injection of chlorpromazine (25mg) for the management of painful blind eyes in Centro Oftalmológico Virgilio Galvis.

RESULTS

Pain control was achieved in 90% of cases (with mean follow-up of 2.1 years). The mean intraocular pressure decreased by 37%. In 7 out of 12 eyes that maintained residual vision, loss of some degree of vision was acknowledged. One patient required an additional cyclodestructive procedure, another one required an absolute alcohol injection, and in an additional case evisceration surgery was necessary to achieve pain control. No serious complications were noted with this therapy.

CONCLUSIONS

Retrobulbar injection of chlorpromazine is a valid option in painful, blind eye cases (or with very poor vision) with a poor visual prognosis.

Ophthalmic regional blocks: management, challenges, and solutions

In the past decade ophthalmic anesthesia has witnessed a major transformation. The sun has set on the landscape of ophthalmic procedures performed under general anesthesia at in-hospital settings. In its place a new dawn has ushered in the panorama of eye surgeries conducted under regional and topical anesthesia at specialty eye care centers. The impact of the burgeoning geriatric population is that an increasing number of elderly patients will present for eye surgery. In order to accommodate increased patient volumes and simultaneously satisfy administrative initiatives directed at economic frugality, administrators will seek assistance from anesthesia providers in adopting measures that enhance operating room efficiency. The performance of eye blocks in a holding suite meets many of these objectives. Unfortunately, most practicing anesthesiologists resist performing ophthalmic regional blocks because they lack formal training. In future, anesthesiologists will need to block eyes and manage common medical conditions because economic pressures will eliminate routine preoperative testing. This review addresses a variety of topical issues in ophthalmic anesthesia with special emphasis on cannula and needle-based blocks and the new-generation antithrombotic agents. In a constantly evolving arena, the sub-Tenon's block has gained popularity while the deep angulated intraconal (retrobulbar) block has been largely superseded by the shallower extraconal (peribulbar) approach. Improvements in surgical technique have also impacted anesthetic practice. For example, phacoemulsification techniques facilitate the conduct of cataract surgery under topical anesthesia, and suture-free vitrectomy ports may cause venous air embolism during air/fluid exchange. Hyaluronidase is a useful adjuvant because it promotes local anesthetic diffusion and hastens block onset time but it is allergenic. Ultrasound-guided eye blocks afford real-time visualization of needle position and local anesthetic spread. An advantage of sonic guidance is that it may eliminate the hazard of globe perforation by identifying abnormal anatomy, such as staphyloma.

Convulsions during cataract surgery under peribulbar anesthesia: a case report

INTRODUCTION

Locoregional anesthesia techniques are increasingly used for cataract surgery. From these techniques, peribulbar anesthesia has been very successful over the retrobulbar anesthesia seen its effectiveness and safety. However, peribulbar anesthesia is not without risk.

CASE PRESENTATION

A 70-year-old African man was scheduled for cataract surgery and lens implant for his right eye. His medical history included hypertension, diabetes mellitus and gall bladder surgery. There were no personal or family antecedents of allergy, epilepsy or taking food or toxic drug. No abnormalities were detected in his preoperative evaluation. In the operating room, standard monitoring was installed and a peripheral venous catheter 18g was inserted. Peribulbar anesthesia was realized with two injections in primary gaze position. The anesthetic mixture contained lidocaine 2% and bupivacaine 0.5%. The needle used was 25GA, 19mm, ¾ inch. The first injection was performed in his lower temporal peribulbar space with 5mL of mixture; the second injection was performed with 3mL of mixture in his upper nasal peribulbar space. These injections were performed after a negative aspiration test and followed by manual compression of his globe for 5 minutes. Five minutes after peribulbar anesthesia, his blood pressure increased to 209/115mmHg requiring three bolus of nicardipine (3.0mg) to reduce his blood pressure to 134/56mmHg. One minute after, he had generalized tonic-clonic seizures. Tracheal intubation was performed. His capillary blood glucose was 170mg/dL, axillary temperature was 36.5°C, and his serum electrolytes were normal. He recovered spontaneous ventilation 1.5 hours later. A neurological examination noted no deficit. Extubation was performed 15 minutes later without incident. A brain computed tomography and electroencephalogram were unremarkable. He was discharged on the second day and operated on 1 month later under general anesthesia.

CONCLUSIONS

Various serious complications can occur during locoregional anesthesia techniques in ophthalmic surgery. The mastering and perfecting of these techniques by practitioners and compliance with safety standards in anesthesia are the only way to guarantee the prevention of such complications.

Relação entre a biometria ultrassonográfica ocular e os parâmetros morfométricos do crânio, idade, peso e gênero em gatos domésticos

O exame ultrassonográfico ocular é indispensável no pré-operatório de procedimentos cirúrgicos intraoculares como a facectomia, além de ser uma ferramenta complementar ao exame oftalmológico, em casos de perda da transparência dos meios ópticos. A inexistência de estudos acerca de padrões de normalidades para as medidas do bulbo ocular e de suas estruturas internas nos gatos, cujos valores possibilitam o monitoramento de enfermidades e auxiliam em procedimentos cirúrgicos motivaram este estudo. Utilizaram-se 40 gatos, adultos, machos e fêmeas, livres de enfermidades sistêmica e oftalmológica. Destes, 22 eram da raça persa (grupo braquicefálico - GB) e 18 sem raça definida (grupo não braquicefálico - GNB). A biometria ultrassonográfica ocular transcorneana foi realizada, em modo-B∕A, com o transdutor microlinear de 9 MHz e as medidas D1 (profundidade da câmara anterior), D2 (diâmetro do cristalino), D3 (profundidade da câmara vítrea) e D4 (diâmetro axial do bulbo ocular) aferidas. Ainda, mensuraram-se as distâncias fronto-occipital e bizigomática e o peso desses animais. Os dados obtidos foram analisados pelo teste-t pareado, seguindo-se as análises de variância e covariância, além da regressão linear múltipla relacionando-se as medidas de D1, D2, D3 e D4 às medidas bizigomática e fronto-occipital, como também à idade, ao peso e ao gênero. Obteve-se como resultado a média de D1, D2, D3 e D4, assim como dos diâmetros bizigomático e fronto-occipital, idade e peso, verificando-se diferenças significativas para D4 nas fêmeas de GB. Houve, pela análise de regressão linear, influência do peso, idade e diâmetro fronto-occipital sobre D1, D2 e D4 nos gatos do GB, e dos diâmetros bizigomático sobre D1, D3 e D4 nos gatos do GNB. Conclui-se que houve diferença no diâmetro axial do bulbo ocular nas fêmeas do GB, e que o peso, a idade e os diâmetros cranianos influenciam a biometria ocular dos gatos braquicefálicos e não braquicefálicos.