A review of current ophthalmic anaesthetic practice

Intro Ophthalmic surgery ranks among the commonest procedures performed worldwide. This review considers the range of anaesthetic techniques available to the modern ophthalmic anaesthetist, and practical considerations to evaluate in different circumstances. There is a brief summary of the main issues pertaining to the common ophthalmic subspecialties and operations. Sources of data Pubmed. Areas of agreement We present a view of contemporary ophthalmic anaesthetic practice as we see it, both from current UK clinical experience, and the available published evidence. Areas of controversy There is an ongoing debate about the safety of sharp needle blocks (SNBs) compared to subtenons and topical techniques, but SNBs still have a role to play, both in specific cases, and in circumstances where resources are limited. Growing points It remains a challenge to provide safe, cost effective anaesthesia to a growing patient base with ever increasing demands and medical comorbidities. There is a continuing trend towards replacing general with local anaesthesia where possible. Research Research in ophthalmic anaesthesia, as in so many areas, has been plagued by heterogeneity and small studies. A coordinated, large scale, multicentred approach to research questions in future would help to guide best practice with more certainty.

Simple and customizable method for fabrication of high-aspect ratio microneedle molds using low-cost 3D printing

We present a simple and customizable microneedle mold fabrication technique using a low-cost desktop SLA 3D printer. As opposed to conventional microneedle fabrication methods, this technique neither requires complex and expensive manufacturing facilities nor expertise in microfabrication. While most low-cost 3D-printed microneedles to date display low aspect ratios and poor tip sharpness, we show that by introducing a two-step “Print & Fill” mold fabrication method, it is possible to obtain high-aspect ratio sharp needles that are capable of penetrating tissue. Studying first the effect of varying design input parameters and print settings, it is shown that printed needles are always shorter than specified. With decreasing input height, needles also begin displaying an increasingly greater than specified needle base diameter. Both factors contribute to low aspect ratio needles when attempting to print sub-millimeter height needles. By setting input height tall enough, it is possible to print needles with high-aspect ratios and tip radii of 20–40 µm. This tip sharpness is smaller than the specified printer resolution. Consequently, high-aspect ratio sharp needle arrays are printed in basins which are backfilled and cured in a second step, leaving sub-millimeter microneedles exposed resulting microneedle arrays which can be used as male masters. Silicone female master molds are then formed from the fabricated microneedle arrays. Using the molds, both carboxymethyl cellulose loaded with rhodamine B as well as polylactic acid microneedle arrays are produced and their quality examined. A skin insertion study is performed to demonstrate the functional capabilities of arrays made from the fabricated molds. This method can be easily adopted by the microneedle research community for in-house master mold fabrication and parametric optimization of microneedle arrays.

Comparison of Intravascular Injection Rate Between Blunt and Sharp Needles During Cervical Transforaminal Epidural Block

Background: Cervical transforaminal epidural block (CTEB) is a useful option in the diagnosis and treatment of cervical radicular pain. However, inadvertent intravascular injection can lead to severe neurologic complications. Blunt needles are considered to displace instead of penetrate vessels because of their dull needle tip. Objectives: To investigate whether there is a difference between blunt and sharp needles in intravascular injection rates during CTEB. Study Design: Prospective, randomized, clinical trial. Setting: A tertiary hospital in South Korea. Methods: After institutional review board approval, 108 patients undergoing CTEB for treatment of radicular pain resulting from spinal stenosis and herniated nucleus pulposus were randomly assigned to one of 2 needle groups (blunt needle or sharp needle). The needle position was confirmed using biplanar fluoroscopy, and 2 mL of nonionic contrast medium was injected to detect intravascular injection. Intravascular injection was defined as the contrast medium spreading out through the vascular channel during injection under realtime fluoroscopy. This study was registered in ClinicalTrials.gov. Results: The intravascular injection rate was not significantly different between the blunt needle and sharp needle groups (35.2% vs. 33.3%, P > 0.05). The procedure time was longer in the blunt needle group than in the sharp needle group (101.00 ± 12.4 seconds vs. 56.67 ± 8.3 seconds, P < 0.001). Limitations: This was a single-center study. Additionally, the physicians could not be blinded to the type of needle used. Conclusions: In the present study, use of a blunt needle did not reduce the rate of intravascular injection during CTEB compared to use of a sharp needle. In addition, procedure time significantly increased with blunt needle use compared to sharp needle use. Key words: Analgesia, bleeding, blunt needle, cervical spine, clinical trials, complications, intravascular injection, radiculopathy, sharp needle, transforaminal epidural block